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Merino-Diez N, Amador R, Stolz ST, Passerone D, Widmer R, Gröning O. Asymmetric Molecular Adsorption and Regioselective Bond Cleavage on Chiral PdGa Crystals. Adv Sci (Weinh) 2024; 11:e2309081. [PMID: 38353319 DOI: 10.1002/advs.202309081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 01/22/2024] [Indexed: 04/25/2024]
Abstract
Homogenous enantioselective catalysis is nowadays the cornerstone in the manufacturing of enantiopure substances, but its technological implementation suffers from well-known impediments like the lack of endurable catalysts exhibiting long-term stability. The catalytically active intermetallic compound Palladium-Gallium (PdGa), conserving innate bulk chirality on its surfaces, represent a promising system to study asymmetric chemical reactions by heterogeneous catalysis, with prospective relevance for industrial processes. Here, this work investigates the adsorption of 10,10'-dibromo-9,9'-bianthracene (DBBA) on the PdGa:A(1 ¯ 1 ¯ 1 ¯ $\bar{1}\bar{1}\bar{1}$ ) Pd3-terminated surface by means of scanning tunneling microscopy (STM) and spectroscopy (STS). A highly enantioselective adsorption of the molecule evolving into a near 100% enantiomeric excess below room temperature is observed. This exceptionally high enantiomeric excess is attributed to temperature activated conversion of the S to the R chiral conformer. Tip-induced bond cleavage of the R conformer shows a very high regioselectivity of the DBBA debromination. The experimental results are interpreted by density functional theory atomistic simulations. This work extends the knowledge of chirality transfer onto the enantioselective adsorption of non-planar molecules and manifests the ensemble effect of PdGa surfaces resulting in robust regioselective debromination.
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Affiliation(s)
- Nestor Merino-Diez
- Nanotech@surfaces Laboratory, Empa - Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, Dübendorf, 8600, Switzerland
| | - Raymond Amador
- Nanotech@surfaces Laboratory, Empa - Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, Dübendorf, 8600, Switzerland
| | - Samuel T Stolz
- Nanotech@surfaces Laboratory, Empa - Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, Dübendorf, 8600, Switzerland
| | - Daniele Passerone
- Nanotech@surfaces Laboratory, Empa - Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, Dübendorf, 8600, Switzerland
| | - Roland Widmer
- Nanotech@surfaces Laboratory, Empa - Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, Dübendorf, 8600, Switzerland
| | - Oliver Gröning
- Nanotech@surfaces Laboratory, Empa - Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, Dübendorf, 8600, Switzerland
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Huang X, Xiong R, Hao C, Beck P, Sa B, Wiebe J, Wiesendanger R. 2D Lateral Heterojunction Arrays with Tailored Interface Band Bending. Adv Mater 2024:e2308007. [PMID: 38315969 DOI: 10.1002/adma.202308007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 12/24/2023] [Indexed: 02/07/2024]
Abstract
Two-dimensional (2D) lateral heterojunction arrays, characterized by well-defined electronic interfaces, hold significant promise for advancing next-generation electronic devices. Despite this potential, the efficient synthesis of high-density lateral heterojunctions with tunable interfacial band alignment remains a challenging. Here, a novel strategy is reported for the fabrication of lateral heterojunction arrays between monolayer Si2 Te2 grown on Sb2 Te3 (ML-Si2 Te2 @Sb2 Te3 ) and one-quintuple-layer Sb2 Te3 grown on monolayer Si2 Te2 (1QL-Sb2 Te3 @ML-Si2 Te2 ) on a p-doped Sb2 Te3 substrate. The site-specific formation of numerous periodically arranged 2D ML-Si2 Te2 @Sb2 Te3 /1QL-Sb2 Te3 @ML-Si2 Te2 lateral heterojunctions is realized solely through three epitaxial growth steps of thick-Sb2 Te3 , ML-Si2 Te2 , and 1QL-Sb2 Te3 films, sequentially. More importantly, the precisely engineering of the interfacial band alignment is realized, by manipulating the substrate's p-doping effect with lateral spatial dependency, on each ML-Si2 Te2 @Sb2 Te3 /1QL-Sb2 Te3 @ML-Si2 Te2 junction. Atomically sharp interfaces of the junctions with continuous lattices are observed by scanning tunneling microscopy. Scanning tunneling spectroscopy measurements directly reveal the tailored type-II band bending at the interface. This reported strategy opens avenues for advancing lateral epitaxy technology, facilitating practical applications of 2D in-plane heterojunctions.
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Affiliation(s)
- Xiaochun Huang
- Department of Physics, University of Hamburg, D-20355, Hamburg, Germany
| | - Rui Xiong
- Multiscale Computational Materials Facility & Materials Genome Institute, School of Materials Science and Engineering, Fuzhou University, Fuzhou, 350108, P. R. China
| | - Chunxue Hao
- Department of Physics, University of Hamburg, D-20355, Hamburg, Germany
| | - Philip Beck
- Department of Physics, University of Hamburg, D-20355, Hamburg, Germany
| | - Baisheng Sa
- Multiscale Computational Materials Facility & Materials Genome Institute, School of Materials Science and Engineering, Fuzhou University, Fuzhou, 350108, P. R. China
| | - Jens Wiebe
- Department of Physics, University of Hamburg, D-20355, Hamburg, Germany
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Gozlinski T, Henn M, Wolf T, Le Tacon M, Schmalian J, Wulfhekel W. Bosonic excitation spectra of superconductingBi2Sr2CaCu2O8+δandYBa2Cu3O6+xextracted from scanning tunneling spectra. J Phys Condens Matter 2024; 36:175601. [PMID: 38194720 DOI: 10.1088/1361-648x/ad1ca8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Accepted: 01/09/2024] [Indexed: 01/11/2024]
Abstract
A detailed interpretation of scanning tunneling spectra obtained on unconventional superconductors enables one to gain information on the pairing boson. Decisive for this approach are inelastic tunneling events. Due to the lack of momentum conservation in tunneling from or to the sharp tip, those are enhanced in the geometry of a scanning tunneling microscope compared to planar tunnel junctions. This work extends the method of obtaining the bosonic excitation spectrum by deconvolution from tunneling spectra to nodald-wave superconductors. In particular, scanning tunneling spectra of slightly underdopedBi2Sr2CaCu2O8+δwith aTcof 82 K and optimally dopedYBa2Cu3O6+xwith aTcof 92 K reveal a resonance mode in their bosonic excitation spectrum atΩres≈63 meVandΩres≈61 meVrespectively. In both cases, the overall shape of the bosonic excitation spectrum is indicative of predominant spin scattering with a resonant mode atΩres<2Δand overdamped spin fluctuations for energies larger than 2Δ. To perform the deconvolution of the experimental data, we implemented an efficient iterative algorithm that significantly enhances the reliability of our analysis.
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Affiliation(s)
- Thomas Gozlinski
- Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Mirjam Henn
- Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Thomas Wolf
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
| | - Matthieu Le Tacon
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
| | - Jörg Schmalian
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
- Institute for Theory of Condensed Matter, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Wulf Wulfhekel
- Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
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4
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Kamal S, Seo I, Bampoulis P, Jugovac M, Brondin CA, Menteş TO, Šarić Janković I, Matetskiy AV, Moras P, Sheverdyaeva PM, Michely T, Locatelli A, Gohda Y, Kralj M, Petrović M. Unidirectional Nano-modulated Binding and Electron Scattering in Epitaxial Borophene. ACS Appl Mater Interfaces 2023. [PMID: 38041641 DOI: 10.1021/acsami.3c14884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2023]
Abstract
A complex interplay between the crystal structure and the electron behavior within borophene renders this material an intriguing 2D system, with many of its electronic properties still undiscovered. Experimental insight into those properties is additionally hampered by the limited capabilities of the established synthesis methods, which, in turn, inhibits the realization of potential borophene applications. In this multimethod study, photoemission spectroscopies and scanning probe techniques complemented by theoretical calculations have been used to investigate the electronic characteristics of a high-coverage, single-layer borophene on the Ir(111) substrate. Our results show that the binding of borophene to Ir(111) exhibits pronounced one-dimensional modulation and transforms borophene into a nanograting. The scattering of photoelectrons from this structural grating gives rise to the replication of the electronic bands. In addition, the binding modulation is reflected in the chemical reactivity of borophene and gives rise to its inhomogeneous aging effect. Such aging is easily reset by dissolving boron atoms in iridium at high temperature, followed by their reassembly into a fresh atomically thin borophene mesh. Besides proving electron-grating capabilities of the boron monolayer, our data provide comprehensive insight into the electronic properties of epitaxial borophene which is vital for further examination of other boron systems of reduced dimensionality.
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Affiliation(s)
- Sherif Kamal
- Centre for Advanced Laser Techniques, Institute of Physics, 10000 Zagreb, Croatia
| | - Insung Seo
- Department of Materials Science and Engineering, Tokyo Institute of Technology, Yokohama 226-8502, Japan
| | - Pantelis Bampoulis
- Physics of Interfaces and Nanomaterials, MESA+ Institute, University of Twente, 7522 NB Enschede, The Netherlands
- Institute of Physics II, University of Cologne, 50937 Cologne, Germany
| | - Matteo Jugovac
- Elettra─Sincrotrone Trieste S.C.p.A., S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Carlo Alberto Brondin
- Department of Molecular Sciences and Nanosystems, Ca' Foscari University of Venice, 30172 Venice, Italy
| | - Tevfik Onur Menteş
- Elettra─Sincrotrone Trieste S.C.p.A., S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Iva Šarić Janković
- Faculty of Physics and Centre for Micro- and Nanosciences and Technologies, University of Rijeka, 51000 Rijeka, Croatia
| | - Andrey V Matetskiy
- Istituto di Struttura della Materia-CNR (ISM-CNR), S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Paolo Moras
- Istituto di Struttura della Materia-CNR (ISM-CNR), S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Polina M Sheverdyaeva
- Istituto di Struttura della Materia-CNR (ISM-CNR), S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Thomas Michely
- Institute of Physics II, University of Cologne, 50937 Cologne, Germany
| | - Andrea Locatelli
- Elettra─Sincrotrone Trieste S.C.p.A., S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Yoshihiro Gohda
- Department of Materials Science and Engineering, Tokyo Institute of Technology, Yokohama 226-8502, Japan
| | - Marko Kralj
- Centre for Advanced Laser Techniques, Institute of Physics, 10000 Zagreb, Croatia
| | - Marin Petrović
- Centre for Advanced Laser Techniques, Institute of Physics, 10000 Zagreb, Croatia
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Vaňo V, Ganguli SC, Amini M, Yan L, Khosravian M, Chen G, Kezilebieke S, Lado JL, Liljeroth P. Evidence of Nodal Superconductivity in Monolayer 1H-TaS 2 with Hidden Order Fluctuations. Adv Mater 2023; 35:e2305409. [PMID: 37592888 DOI: 10.1002/adma.202305409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 08/07/2023] [Indexed: 08/19/2023]
Abstract
Unconventional superconductors represent one of the fundamental directions in modern quantum materials research. In particular, nodal superconductors are known to appear naturally in strongly correlated systems, including cuprate superconductors and heavy-fermion systems. Van der Waals materials hosting superconducting states are well known, yet nodal monolayer van der Waals superconductors have remained elusive. Here, using low-temperature scanning tunneling microscopy (STM) and spectroscopy (STS) experiments, it is shown that pristine monolayer 1H-TaS2 realizes a nodal superconducting state. Non-magnetic disorder drives the nodal superconducting state to a conventional gapped s-wave state. Furthermore, many-body excitations emerge close to the gap edge, signalling a potential unconventional pairing mechanism. The results demonstrate the emergence of nodal superconductivity in a van der Waals monolayer, providing a building block for van der Waals heterostructures exploiting unconventional superconducting states.
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Affiliation(s)
- Viliam Vaňo
- Department of Applied Physics, Aalto University, FI-00076, Aalto, Finland
| | | | - Mohammad Amini
- Department of Applied Physics, Aalto University, FI-00076, Aalto, Finland
| | - Linghao Yan
- Department of Applied Physics, Aalto University, FI-00076, Aalto, Finland
- Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
| | - Maryam Khosravian
- Department of Applied Physics, Aalto University, FI-00076, Aalto, Finland
| | - Guangze Chen
- Department of Applied Physics, Aalto University, FI-00076, Aalto, Finland
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, Gothenburg, 41296, Sweden
| | - Shawulienu Kezilebieke
- Department of Physics, Department of Chemistry and Nanoscience Center, University of Jyväskylä, University of Jyväskylä, FI-40014, Finland
| | - Jose L Lado
- Department of Applied Physics, Aalto University, FI-00076, Aalto, Finland
| | - Peter Liljeroth
- Department of Applied Physics, Aalto University, FI-00076, Aalto, Finland
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6
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Pushkarna I, Pásztor Á, Renner C. Twist-Angle-Dependent Electronic Properties of Exfoliated Single Layer MoS 2 on Au(111). Nano Lett 2023; 23:9406-9412. [PMID: 37844067 PMCID: PMC10603799 DOI: 10.1021/acs.nanolett.3c02804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 09/29/2023] [Indexed: 10/18/2023]
Abstract
Synthetic materials and heterostructures obtained by the controlled stacking of exfoliated monolayers are emerging as attractive functional materials owing to their highly tunable properties. We present a detailed scanning tunneling microscopy and spectroscopy study of single layer MoS2-on-gold heterostructures as a function of the twist angle. We find that their electronic properties are determined by the hybridization of the constituent layers and are modulated at the moiré period. The hybridization depends on the layer alignment, and the modulation amplitude vanishes with increasing twist angle. We explain our observations in terms of a hybridization between the nearest sulfur and gold atoms, which becomes spatially more homogeneous and weaker as the moiré periodicity decreases with increasing twist angle, unveiling the possibility of tunable hybridization of electronic states via twist angle engineering.
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Affiliation(s)
| | | | - Christoph Renner
- Department of Quantum Matter
Physics, Université de Genève, 24 Quai Ernest Ansermet, CH-1211 Geneva, Switzerland
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7
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Kumar Nayak A, Steinbok A, Roet Y, Koo J, Feldman I, Almoalem A, Kanigel A, Yan B, Rosch A, Avraham N, Beidenkopf H. First-order quantum phase transition in the hybrid metal-Mott insulator transition metal dichalcogenide 4Hb-TaS 2. Proc Natl Acad Sci U S A 2023; 120:e2304274120. [PMID: 37856542 PMCID: PMC10614784 DOI: 10.1073/pnas.2304274120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Accepted: 08/19/2023] [Indexed: 10/21/2023] Open
Abstract
Coupling together distinct correlated and topologically nontrivial electronic phases of matter can potentially induce novel electronic orders and phase transitions among them. Transition metal dichalcogenide compounds serve as a bedrock for exploration of such hybrid systems. They host a variety of exotic electronic phases, and their Van der Waals nature enables to admix them, either by exfoliation and stacking or by stoichiometric growth, and thereby induce novel correlated complexes. Here, we investigate the compound 4Hb-TaS2 that interleaves the Mott-insulating state of 1T-TaS2 and the putative spin liquid it hosts together with the metallic state of 2H-TaS2 and the low-temperature superconducting phase it harbors using scanning tunneling spectroscopy. We reveal a thermodynamic phase diagram that hosts a first-order quantum phase transition between a correlated Kondo-like cluster state and a depleted flat band state. We demonstrate that this intrinsic transition can be induced by an electric field and temperature as well as by manipulation of the interlayer coupling with the probe tip, hence allowing to reversibly toggle between the Kondo-like cluster and the depleted flat band states. The phase transition is manifested by a discontinuous change of the complete electronic spectrum accompanied by hysteresis and low-frequency noise. We find that the shape of the transition line in the phase diagram is determined by the local compressibility and the entropy of the two electronic states. Our findings set such heterogeneous structures as an exciting platform for systematic investigation and manipulation of Mott-metal transitions and strongly correlated phases and quantum phase transitions therein.
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Affiliation(s)
- Abhay Kumar Nayak
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot7610001, Israel
| | - Aviram Steinbok
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot7610001, Israel
| | - Yotam Roet
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot7610001, Israel
| | - Jahyun Koo
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot7610001, Israel
| | - Irena Feldman
- Department of Physics, Technion - Israel Institute of Technology, Haifa32000, Israel
| | - Avior Almoalem
- Department of Physics, Technion - Israel Institute of Technology, Haifa32000, Israel
| | - Amit Kanigel
- Department of Physics, Technion - Israel Institute of Technology, Haifa32000, Israel
| | - Binghai Yan
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot7610001, Israel
| | - Achim Rosch
- Institute for Theoretical Physics, University of Cologne, Zülpicher Str. 77, Köln50937, Germany
| | - Nurit Avraham
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot7610001, Israel
| | - Haim Beidenkopf
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot7610001, Israel
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8
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Duan J, Wang J, Hou L, Ji P, Zhang W, Liu J, Zhu X, Sun Z, Ma Y, Ma L. Application of Scanning Tunneling Microscopy and Spectroscopy in the Studies of Colloidal Quantum Qots. CHEM REC 2023; 23:e202300120. [PMID: 37255365 DOI: 10.1002/tcr.202300120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 05/15/2023] [Indexed: 06/01/2023]
Abstract
Colloidal quantum dots display remarkable optical and electrical characteristics with the potential for extensive applications in contemporary nanotechnology. As an ideal instrument for examining surface topography and local density of states (LDOS) at an atomic scale, scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) has become indispensable approaches to gain better understanding of their physical properties. This article presents a comprehensive review of the research advancements in measuring the electronic orbits and corresponding energy levels of colloidal quantum dots in various systems using STM and STS. The first three sections introduce the basic principles of colloidal quantum dots synthesis and the fundamental methodology of STM research on quantum dots. The fourth section explores the latest progress in the application of STM for colloidal quantum dot studies. Finally, a summary and prospective is presented.
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Affiliation(s)
- Jiaying Duan
- Tianjin International Center for Nanoparticles and NanoSystems, Tianjin University, Tianjin, China, 300072
| | - Jiapeng Wang
- Tianjin International Center for Nanoparticles and NanoSystems, Tianjin University, Tianjin, China, 300072
| | - Liangpeng Hou
- Tianjin International Center for Nanoparticles and NanoSystems, Tianjin University, Tianjin, China, 300072
| | - Peixuan Ji
- Tianjin International Center for Nanoparticles and NanoSystems, Tianjin University, Tianjin, China, 300072
| | - Wusheng Zhang
- Tianjin International Center for Nanoparticles and NanoSystems, Tianjin University, Tianjin, China, 300072
| | - Jin Liu
- Tianjin International Center for Nanoparticles and NanoSystems, Tianjin University, Tianjin, China, 300072
| | - Xiaodong Zhu
- Tianjin International Center for Nanoparticles and NanoSystems, Tianjin University, Tianjin, China, 300072
| | - Zhixiang Sun
- Center for Joint Quantum Studies and Department of Physics, School of Science, Tianjin University, Tianjin, China, 300072
| | - Yanqing Ma
- Tianjin International Center for Nanoparticles and NanoSystems, Tianjin University, Tianjin, China, 300072
| | - Lei Ma
- Tianjin International Center for Nanoparticles and NanoSystems, Tianjin University, Tianjin, China, 300072
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9
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Huang PC, Sun H, Sarker M, Caroff CM, Girolami GS, Sinitskii A, Lyding JW. Sub-5 nm Contacts and Induced p-n Junction Formation in Individual Atomically Precise Graphene Nanoribbons. ACS Nano 2023; 17:17771-17778. [PMID: 37581379 DOI: 10.1021/acsnano.3c02794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/16/2023]
Abstract
This paper demonstrates the fabrication of nanometer-scale metal contacts on individual graphene nanoribbons (GNRs) and the use of these contacts to control the electronic character of the GNRs. We demonstrate the use of a low-voltage direct-write STM-based process to pattern sub-5 nm metallic hafnium diboride (HfB2) contacts directly on top of single GNRs in an ultrahigh-vacuum scanning tunneling microscope (UHV-STM), with all the fabrication performed on a technologically relevant semiconductor silicon substrate. Scanning tunneling spectroscopy (STS) data not only verify the expected metallic and semiconducting character of the contacts and GNR, respectively, but also show induced band bending and p-n junction formation in the GNR due to the metal-GNR work function difference. Contact engineering with different work function metals obviates the need to create GNRs with different characteristics by complex chemical doping. This is a demonstration of the successful fabrication of precise metal contacts and local p-n junction formation on single GNRs.
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Wang J, Bagheri Tagani M, Zhang L, Xia Y, Wu Q, Li B, Tian Y, Yin LJ, Zhang L, Qin Z. Realization of black phosphorus-like PbSe monolayer on Au(111) via epitaxial growth. J Phys Condens Matter 2023; 35:485002. [PMID: 37586387 DOI: 10.1088/1361-648x/acf107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Accepted: 08/16/2023] [Indexed: 08/18/2023]
Abstract
Lead selenide (PbSe) has been attracted a lot attention in fundamental research and industrial applications due to its excellent infrared optical and thermoelectric properties, toward reaching the two-dimensional limit. Herein, we realize the black phosphorus-like PbSe (α-phase PbSe) monolayer on Au(111) via epitaxial growth, where a characteristic rectangular superlattice of 5 Å × 9 Å corresponding to 1 × 2 reconstruction with respect to the pristine ofα-phase PbSe is observed by scanning tunneling microscopy. Corresponding density functional theory calculation confirmed the reconstruction and revealed the driven mechanism, the coupling between monolayer PbSe and Au(111) substrate. The metallic feature of differential conductance spectra as well as the transition of the density of states from semiconductor to metal further verified such coupling. As the unique anisotropic structure, our study provides a pathway towards the synthesis of BP-PbSe monolayer. In addition, it builds up an ideal platform for studying fundamental physics and also excellent prospects in PbSe-based device applications.
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Affiliation(s)
- Jing Wang
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | | | - Li Zhang
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Yu Xia
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Qilong Wu
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Bo Li
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Yuan Tian
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Long-Jing Yin
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Lijie Zhang
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Zhihui Qin
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
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11
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Marz M, Issac A, Fritsch V, Kimouche A, Hoffmann-Vogel R. Real-Space Imaging of Several Molecular Layers of C 60in the Rotational Glass Phase. J Phys Condens Matter 2023. [PMID: 37369226 DOI: 10.1088/1361-648x/ace22b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/29/2023]
Abstract
C60is a model system to study molecule-surface interactions and phase transitions due to its high symmetry and strong covalent π bonding within the molecule versus weak van-der-Waals coupling between neighboring molecules. In the solid, at room temperature, the molecule rotates and behaves as a sphere. However, the pentagonal and hexagonal atomic arrangement imposes deviations from the spherical symmetry that become important at low temperatures. The orientation of the C60can be viewed to represent classic spins. For geometrical reasons the preferred orientation of neighboring C60cannot be satisfied for all of the neighboring molecules, making C60a model for disordered spin systems with frustration. We study several molecular
layers of C<sub>60</sub islands on highly oriented pyrolytic graphite (HOPG) using scanning tunneling microscopy at liquid nitrogen temperatures. By imaging several layers we obtain a limited access to the three-dimensional rotational structure of the molecules in
an island. We find one rotationally disordered layer between two partially rotationally ordered layers with hexagonal patterns. This exotic pattern shows an example of the local distribution of order and disorder in geometrically frustrated systems. Scanning
Tunneling Spectroscopy data confirms the weak interactions of neighboring molecules.
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Affiliation(s)
- Michael Marz
- Karlsruher Institut für Technologie, Wolfgang-Gaede-Str. 1, Karlsruhe, 76128, GERMANY
| | - Andrew Issac
- Physikalisches Institut, Karlsruher Institut für Technologie, Wolfgang-Gaede-Str. 1, Karlsruhe, 76128, GERMANY
| | - Veronika Fritsch
- Experimental Physics VI, University of Augsburg, Center for Electronic Correlations and Magnetism, Augsburg, Bayern, 86159, GERMANY
| | - Amina Kimouche
- Department of Physics and Astronomy, University of Potsdam, Karl-Liebknecht Straße 24-25, Potsdam, 14469, GERMANY
| | - Regina Hoffmann-Vogel
- Department of Physics and Astronomy, University of Potsdam, Karl-Liebknecht Straße 24-25, Potsdam, 14469, GERMANY
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12
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Abstract
Electronic properties of two-dimensional (2D) materials can be significantly tuned by an external electric field. Ferroelectric gates can provide a strong polarization electric field. Here, we report the measurements of the band structure of few-layer MoS2 modulated by a ferroelectric P(VDF-TrFE) gate with contact-mode scanning tunneling spectroscopy. When P(VDF-TrFE) is fully polarized, an electric field up to ∼0.62 V/nm through the MoS2 layers is inferred from the measured band edges, which affects the band structure significantly. First, strong band bending in the vertical direction signifies the Franz-Keldysh effect and a large extension of the optical absorption edge. Photons with energy of half the band gap are still absorbed with 20% of the absorption probability of photons at the band gap. Second, the electric field greatly enlarges the energy separations between the quantum-well subbands. Our study intuitively demonstrates the great potential of ferroelectric gates in band structure manipulation of 2D materials.
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Affiliation(s)
- Xinzuo Sun
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Yan Chen
- Shanghai Frontiers Science Research Base of Intelligent Optoelectronics and Perception, Institute of Optoelectronics, Fudan University, Shanghai 200433, China
- Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 20083, China
| | - Dongyang Zhao
- Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 20083, China
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Jianlu Wang
- Shanghai Frontiers Science Research Base of Intelligent Optoelectronics and Perception, Institute of Optoelectronics, Fudan University, Shanghai 200433, China
- Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 20083, China
- Frontier Institute of Chip and System, Fudan University, Shanghai 200433, China
| | - Jiamin Xue
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
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13
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Sagisaka K, Kusawake T, Bowler D, Ohno S. Emergence of metallic surface states and negative differential conductance in thin β-FeSi 2films on Si(001). J Phys Condens Matter 2023; 35:135001. [PMID: 36696697 DOI: 10.1088/1361-648x/acb628] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 01/25/2023] [Indexed: 06/17/2023]
Abstract
The electronic properties of the surface ofβ-FeSi2have been debated for a long. We studied the surface states ofβ-FeSi2films grown on Si(001) substrates using scanning tunnelling microscopy (STM) and spectroscopy (STS), with the aid of density functional theory calculations. STM simulations using the surface model proposed by Romanyuket al(2014Phys. Rev.B90155305) reproduce the detailed features of experimental STM images. The result of STS showed metallic surface states in accordance with theoretical predictions. The Fermi level was pinned by a surface state that appeared in the bulk band gap of theβ-FeSi2film, irrespective of the polarity of the substrate. We also observed negative differential conductance at ∼0.45 eV above the Fermi level in STS measurements performed at 4.5 K, reflecting the presence of an energy gap in the unoccupied surface states ofβ-FeSi2.
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Affiliation(s)
- Keisuke Sagisaka
- Research Center for Advanced Measurement and Characterization, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan
| | - Tomoko Kusawake
- Research Center for Advanced Measurement and Characterization, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan
| | - David Bowler
- London Centre for Nanotechnology, University College London, 17-19 Gordon St., London WC1H 0AH, United Kingdom
- Department of Physics & Astronomy, University College London, Gower St, London WC1E 6BT, United Kingdom
- International Centre for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Shinya Ohno
- Yokohama National University, 79-5 Tokiwadai Hodogaya-ku, Yokohama, Kanagawa 240-8501, Japan
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14
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Chen Z, Sun M, Li H, Huang B, Loh KP. Oscillatory Order-Disorder Transition during Layer-by-Layer Growth of Indium Selenide. Nano Lett 2023; 23:1077-1084. [PMID: 36696459 DOI: 10.1021/acs.nanolett.2c04785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
It is important to understand the polymorph transition and crystal-amorphous phase transition in In2Se3 to tap the potential of this material for resistive memory storage. By monitoring layer-by-layer growth of β-In2Se3 during molecular beam epitaxy (MBE), we are able to identify a cyclical order-disorder transition characterized by a periodic alternation between a glassy-like metastable subunit cell film consisting of n < 5 sublayers (nth layers = the number of subunit cell layers), and a highly crystalline β-In2Se3 at n = 5 layers. The glassy phase shows an odd-even alternation between the indium-cluster layer (n = 1, 3) and an In-Se solid solution (n = 2, 4), which suggests the ability of In and Se atoms to diffuse, aggregate, and intermix. These dynamic natures of In and Se atoms contribute to a defect-driven memory resistive behavior in current-voltage sweeps that is different from the ferroelectric switching of α-In2Se3.
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Affiliation(s)
- Zhi Chen
- International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology (ICL-2D MOST), Shenzhen University, Shenzhen518060, People's Republic of China
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, 518060, People's Republic of China
| | - Mingzi Sun
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, 999077, People's Republic of China
| | - Haohan Li
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore117543, Singapore
| | - Bolong Huang
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, 999077, People's Republic of China
- Research Centre for Carbon-Strategic Catalysis, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, 999077, People's Republic of China
| | - Kian Ping Loh
- International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology (ICL-2D MOST), Shenzhen University, Shenzhen518060, People's Republic of China
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore117543, Singapore
- Department of Applied Physics, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR999077, People's Republic of China
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15
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Li Y, Shen D, Kreisel A, Chen C, Wei T, Xu X, Wang J. Anisotropic Gap Structure and Sign Reversal Symmetry in Monolayer Fe(Se,Te). Nano Lett 2023; 23:140-147. [PMID: 36450010 DOI: 10.1021/acs.nanolett.2c03735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
The iron-based superconductors are an ideal platform to reveal the enigma of the unconventional superconductivity and potential topological superconductivity. Among them, the monolayer Fe(Se,Te)/SrTiO3(001), which is proposed to be topological nontrivial, shows interface-enhanced high-temperature superconductivity in the two-dimensional limit. However, the experimental studies on the superconducting pairing mechanism of monolayer Fe(Se,Te) films are still limited. Here, by measuring the quasiparticle interference in monolayer Fe(Se,Te)/SrTiO3(001), we report the observation of the anisotropic structure of the large superconducting gap and the sign change of the superconducting gap on different electron pockets. The results are well consistent with the "bonding-antibonding" s±-wave pairing symmetry driven by spin fluctuations in conjunction with spin-orbit coupling. Our work is of basic significance not only for a unified superconducting formalism in the iron-based superconductors, but also for understanding of topological superconductivity in high-temperature superconductors.
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Affiliation(s)
- Yu Li
- International Center for Quantum Materials, School of Physics, Peking University, Beijing100871, China
| | - Dingyu Shen
- International Center for Quantum Materials, School of Physics, Peking University, Beijing100871, China
| | - Andreas Kreisel
- Institut für Theoretische Physik, Universität Leipzig, D-04103Leipzig, Germany
| | - Cheng Chen
- International Center for Quantum Materials, School of Physics, Peking University, Beijing100871, China
| | - Tianheng Wei
- International Center for Quantum Materials, School of Physics, Peking University, Beijing100871, China
| | - Xiaotong Xu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing100871, China
| | - Jian Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing100871, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing100190, China
- Beijing Academy of Quantum Information Sciences, Beijing100193, China
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16
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Xie H, Xiang X, Chen Y. Improving the deconvolution of spectra at finite temperatures by replacing spectrum with a neural network. J Phys Condens Matter 2022; 35:045701. [PMID: 36541497 DOI: 10.1088/1361-648x/aca57a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 11/23/2022] [Indexed: 06/17/2023]
Abstract
In condensed matter physics studies, spectral information plays an important role in understanding the composition of materials. However, it is difficult to obtain a material's spectrum information directly through experiments or simulations. For example, the spectral information deconvoluted by scanning tunneling spectroscopy suffers from the temperature broadening effect, which is a known ill-posed problem and makes the deconvolution results unstable. Existing methods, such as the maximum entropy method, tend to select an appropriate regularization to suppress unstable oscillations. However, the choice of regularization is difficult, and oscillations are not completely eliminated. We believe that the possible improvement direction is to pay different attention to different intervals. Combining stochastic optimization and deep learning, in this paper, we introduce a neural network-based strategy to solve the deconvolution problem. Because the neural network can represent any nonuniform piecewise linear function, our method replaces the target spectrum with a neural network and can find a better approximation solution through an accurate and efficient optimization. Experiments on theoretical datasets using superconductors demonstrate that the superconducting gap is more accurately estimated and oscillates less. Plug in real experimental data, our approach obtains clearer results for material analysis.
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Affiliation(s)
- Haidong Xie
- China Academy of Aerospace Science and Innovation, Beijing 100082, People's Republic of China
| | - Xueshuang Xiang
- Qian Xuesen Laboratory of Space Technology, China Academy of Space Technology, Beijing 100080, People's Republic of China
| | - Yuanqing Chen
- China Academy of Aerospace Science and Innovation, Beijing 100082, People's Republic of China
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17
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Lin YH, Chen CJ, Kumar N, Yeh TY, Lin TH, Blügel S, Bihlmayer G, Hsu PJ. Fabrication and Imaging Monatomic Ni Kagome Lattice on Superconducting Pb(111). Nano Lett 2022; 22:8475-8481. [PMID: 36282025 DOI: 10.1021/acs.nanolett.2c02831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Artificial fabrication of a monolayer Kagome material can offer a promising opportunity to explore exceptional quantum states and phenomena in low dimensionality. Here, we have systematically studied a monatomic Ni Kagome lattice grown on Pb(111) by scanning tunneling microscopy/spectroscopy (STM/STS) and density functional theory (DFT). Sawtooth edge structures with distinct heights due to subsurface Ni atoms have been revealed, leading to asymmetric edge scattering of surface electrons on Pb(111). In addition, a local maximum at about -0.2 eV in tunneling spectra represents a manifestation of characteristic phase-destructive flat bands. Although charge transfer from underlying Pb(111) substrate results in a vanishing magnetic moment of Ni atoms, the proximity-induced superconducting gap is slightly enhanced on the Ni Kagome lattice. In light of single-atomic-layer Ni Kagome lattice on superconducting Pb(111) substrate, it could serve as an ideal platform to investigate the interplay between Kagome physics and superconductivity down to the two-dimensional limit.
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Affiliation(s)
- Yen-Hui Lin
- Department of Physics, National Tsing Hua University, 300044Hsinchu, Taiwan
| | - Chia-Ju Chen
- Department of Physics, National Tsing Hua University, 300044Hsinchu, Taiwan
| | - Nitin Kumar
- Department of Physics, National Tsing Hua University, 300044Hsinchu, Taiwan
| | - Ta-Yu Yeh
- Department of Physics, National Tsing Hua University, 300044Hsinchu, Taiwan
| | - Tzu-Hsuan Lin
- Department of Physics, National Tsing Hua University, 300044Hsinchu, Taiwan
| | - Stefan Blügel
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, D-52425Jülich, Germany
| | - Gustav Bihlmayer
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, D-52425Jülich, Germany
| | - Pin-Jui Hsu
- Department of Physics, National Tsing Hua University, 300044Hsinchu, Taiwan
- Center for Quantum Technology, National Tsing Hua University, Hsinchu300044, Taiwan
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18
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Küster F, Brinker S, Hess R, Loss D, Parkin SSP, Klinovaja J, Lounis S, Sessi P. Non-Majorana modes in diluted spin chains proximitized to a superconductor. Proc Natl Acad Sci U S A 2022; 119:e2210589119. [PMID: 36215505 DOI: 10.1073/pnas.2210589119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Spin chains proximitized with superconducting condensates have emerged as one of the most promising platforms for the realization of Majorana modes. Here, we craft diluted spin chains atom by atom following a seminal theoretical proposal suggesting indirect coupling mechanisms as a viable route to trigger topological superconductivity. Starting from single adatoms hosting deep Shiba states, we use the highly anisotropic Fermi surface of the substrate to create spin chains characterized by different magnetic configurations along distinct crystallographic directions. By scrutinizing a large set of parameters we reveal the ubiquitous emergence of boundary modes. Although mimicking signatures of Majorana modes, the end modes are identified as topologically trivial Shiba states. Our work demonstrates that zero-energy modes in spin chains proximitized to superconductors are not necessarily a link to Majorana modes while simultaneously identifying other experimental platforms, driving mechanisms, and test protocols for the determination of topologically nontrivial superconducting phases.
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19
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Wang X, Liu N, Wu Y, Qu Y, Zhang W, Wang J, Guan D, Wang S, Zheng H, Li Y, Liu C, Jia J. Strong Coupling Superconductivity in Ca-Intercalated Bilayer Graphene on SiC. Nano Lett 2022; 22:7651-7658. [PMID: 36066512 DOI: 10.1021/acs.nanolett.2c02804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The metal-intercalated bilayer graphene has a flat band with a high density of states near the Fermi energy and thus is anticipated to exhibit an enhanced strong correlation effect and associated fascinating phenomena, including superconductivity. By using a self-developed multifunctional scanning tunneling microscope, we succeeded in observing the superconducting energy gap and diamagnetic response of a Ca-intercalated bilayer graphene below a critical temperature of 8.83 K. The revealed high value of gap ratio, 2Δ/kBTc ≈ 5.0, indicates a strong coupling superconductivity, while the variation of penetration depth with temperature and magnetic field indicates an isotropic s-wave superconductor. These results provide crucial experimental clues for understanding the origin and mechanism of superconductivity in carrier-doped graphene.
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Affiliation(s)
- Xutao Wang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
| | - Ningning Liu
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
| | - Yanfu Wu
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
| | - Yueqiao Qu
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
| | - Wenxuan Zhang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
| | - Jinyue Wang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
| | - Dandan Guan
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
| | - Shiyong Wang
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
| | - Hao Zheng
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
| | - Yaoyi Li
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
| | - Canhua Liu
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
- Tsung-Dao Lee Institute, Shanghai 200240, People's Republic of China
| | - Jinfeng Jia
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People's Republic of China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, People's Republic of China
- Tsung-Dao Lee Institute, Shanghai 200240, People's Republic of China
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20
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Lin MK, Chen GH, Ho CL, Chueh WC, Hlevyack JA, Kuo CN, Fu TY, Lin JJ, Lue CS, Chang WH, Takagi N, Arafune R, Chiang TC, Lin CL. Tip-Mediated Bandgap Tuning for Monolayer Transition Metal Dichalcogenides. ACS Nano 2022; 16:14918-14924. [PMID: 36036754 DOI: 10.1021/acsnano.2c05841] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Monolayer transition metal dichalcogenides offer an appropriate platform for developing advanced electronics beyond graphene. Similar to two-dimensional molecular frameworks, the electronic properties of such monolayers can be sensitive to perturbations from the surroundings; the implied tunability of electronic structure is of great interest. Using scanning tunneling microscopy/spectroscopy, we demonstrated a bandgap engineering technique in two monolayer materials, MoS2 and PtTe2, with the tunneling current as a control parameter. The bandgap of monolayer MoS2 decreases logarithmically by the increasing tunneling current, indicating an electric-field-induced gap renormalization effect. Monolayer PtTe2, by contrast, exhibits a much stronger gap reduction, and a reversible semiconductor-to-metal transition occurs at a moderate tunneling current. This unusual switching behavior of monolayer PtTe2, not seen in bulk semimetallic PtTe2, can be attributed to its surface electronic structure that can readily couple to the tunneling tip, as demonstrated by theoretical calculations.
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Affiliation(s)
- Meng-Kai Lin
- Department of Physics, National Central University, Taoyuan 32001, Taiwan
| | - Guan-Hao Chen
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
- Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan
| | - Ciao-Lin Ho
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
| | - Wei-Chen Chueh
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
| | - Joseph Andrew Hlevyack
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Chia-Nung Kuo
- Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan
- Taiwan Consortium of Emergent Crystalline Materials, National Science and Technology Council, Taipei 106, Taiwan
| | - Tsu-Yi Fu
- Department of Physics, National Taiwan Normal University, Taipei 11677, Taiwan
| | - Juhn-Jong Lin
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
- Center for Emergent Functional Matter Science (CEFMS), National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
| | - Chin Shan Lue
- Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan
- Taiwan Consortium of Emergent Crystalline Materials, National Science and Technology Council, Taipei 106, Taiwan
| | - Wen-Hao Chang
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
- Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan
- Center for Emergent Functional Matter Science (CEFMS), National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
| | - Noriaki Takagi
- Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan
| | - Ryuichi Arafune
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Ibaraki 304-0044, Japan
| | - Tai-Chang Chiang
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Chun-Liang Lin
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
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21
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Wang Y, Gao Q, Li W, Cheng P, Zhang YQ, Feng B, Hu Z, Wu K, Chen L. Nearly Ideal Two-Dimensional Electron Gas Hosted by Multiple Quantized Kronig-Penney States Observed in Few-Layer InSe. ACS Nano 2022; 16:13014-13021. [PMID: 35943244 DOI: 10.1021/acsnano.2c05556] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
A theoretical ideal two-dimensional electron gas (2DEG) was characterized by a flat density of states independent of energy. Compared with conventional two-dimensional free-electron systems in semiconductor heterojunctions and noble metal surfaces, we report here the achievement of ideal 2DEG with multiple quantized states in few-layer InSe films. The multiple quantum well states (QWSs) in few-layer InSe films are found, and the number of QWSs is strictly equal to the number of atomic layers. The multiple stair-like DOS as well as multiple bands with parabolic dispersion both characterize ideal 2DEG features in these QWSs. Density functional theory calculations and numerical simulations based on quasi-bounded square potential wells described as the Kronig-Penney model provide a consistent explanation of 2DEG in the QWSs. Our work demonstrates that 2D van der Waals materials are ideal systems for realizing 2DEG hosted by multiple quantized Kronig-Penney states, and the semiconducting nature of the material provides a better chance for construction of high-performance electronic devices utilizing these states, for example, superlattice devices with negative differential resistance.
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Affiliation(s)
- Yu Wang
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Qian Gao
- School of Physics, Nankai University, Tianjin 300071, China
| | - Wenhui Li
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Peng Cheng
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Yi-Qi Zhang
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Baojie Feng
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Zhenpeng Hu
- School of Physics, Nankai University, Tianjin 300071, China
| | - Kehui Wu
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Lan Chen
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
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22
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Li K, Xiao F, Guan W, Xiao Y, Xu C, Zhang J, Lin C, Li D, Tong Q, Li SY, Pan A. Morphology Deformation and Giant Electronic Band Modulation in Long-Wavelength WS 2 Moiré Superlattices. Nano Lett 2022; 22:5997-6003. [PMID: 35839083 DOI: 10.1021/acs.nanolett.2c02418] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
As a lattice interference effect, moiré superlattices feature a magnification effect that they respond sensitively to both the extrinsic mechanical perturbations and intrinsic atomic reconstructions. Here, using scanning tunneling microscopy and spectroscopy, we observe that long-wavelength WS2 superlattices are reconstructed into various moiré morphologies, ranging from regular hexagons to heavily deformed ones. We show that a dedicated interplay between the extrinsic nonuniform heterostrain and the intrinsic atomic reconstruction is responsible for this interesting moiré structure evolution. Importantly, the interplay between these two factors also introduces a local inhomogeneous intralayer strain within a moiré. Contrary to the commonly reported electronic modulation that occurred at the valence band edge due to interlayer hybridization, we find that this local intralayer strain induces a strong modulation at K point of the conduction band, reaching up to 300 meV in the heavily deformed moiré. Our microscopic explorations provide valuable information in understanding the intriguing physics in TMD moirés.
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Affiliation(s)
- Kaihui Li
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha 410082, People's Republic of China
- Hunan Institute of Optoelectronic Integration, Hunan University, Changsha 410082, People's Republic of China
| | - Feiping Xiao
- School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Wen Guan
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha 410082, People's Republic of China
- Hunan Institute of Optoelectronic Integration, Hunan University, Changsha 410082, People's Republic of China
| | - Yulong Xiao
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha 410082, People's Republic of China
- Hunan Institute of Optoelectronic Integration, Hunan University, Changsha 410082, People's Republic of China
| | - Chang Xu
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha 410082, People's Republic of China
- Hunan Institute of Optoelectronic Integration, Hunan University, Changsha 410082, People's Republic of China
| | - Jinding Zhang
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha 410082, People's Republic of China
- Hunan Institute of Optoelectronic Integration, Hunan University, Changsha 410082, People's Republic of China
| | - Chenfang Lin
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha 410082, People's Republic of China
- Hunan Institute of Optoelectronic Integration, Hunan University, Changsha 410082, People's Republic of China
| | - Dong Li
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha 410082, People's Republic of China
- Hunan Institute of Optoelectronic Integration, Hunan University, Changsha 410082, People's Republic of China
| | - Qingjun Tong
- School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Si-Yu Li
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha 410082, People's Republic of China
- Hunan Institute of Optoelectronic Integration, Hunan University, Changsha 410082, People's Republic of China
| | - Anlian Pan
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, College of Materials Science and Engineering, Hunan University, Changsha 410082, People's Republic of China
- Hunan Institute of Optoelectronic Integration, Hunan University, Changsha 410082, People's Republic of China
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23
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Sung YY, Vejayan H, Baddeley CJ, Richardson NV, Grillo F, Schaub R. Surface Confined Hydrogenation of Graphene Nanoribbons. ACS Nano 2022; 16:10281-10291. [PMID: 35786912 PMCID: PMC9330764 DOI: 10.1021/acsnano.1c11372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
On-surface synthesis with designer precursor molecules is considered an effective method for preparing graphene nanoribbons (GNRs) of well-defined widths and with tunable electronic properties. Recent reports have shown that the band gap of ribbons doped with heteroatoms (such as boron, nitrogen, and sulfur) remains unchanged in magnitude in most cases. Nevertheless, theory predicts that a tunable band gap may be engineered by hydrogenation, but experimental evidence for this is so far lacking. Herein, surface-confined hydrogenation studies of 7-armchair graphene nanoribbons (7-AGNRs) grown on Au(111) surfaces, in an ultrahigh vacuum environment, are reported. GNRs are first prepared, then hydrogenated by exposure to activated hydrogen atoms. High resolution electron energy loss spectroscopy (HREELS) and scanning tunneling microscopy (STM) images reveal a self-limited hydrogenation process. By means of a combination of bond-resolved scanning tunneling microscopy (BRSTM) imaging and tip-induced site-specific dehydrogenation, the hydrogenation mechanism is studied in detail, and density-functional theory (DFT) calculation methods are used to complement the experimental findings. In all cases, the results demonstrate the successful modification of the electronic properties of the GNR/Au(111) system by edge and basal-plane hydrogenation, and a mechanism for the hydrogenation process is proposed.
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24
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Elizabeth A, Sahoo SK, Phirke H, Kodalle T, Kühne TD, Audinot JN, Wirtz T, Redinger A, Kaufmann CA, Mirhosseini H, Mönig H. Surface Passivation and Detrimental Heat-Induced Diffusion Effects in RbF-Treated Cu(In,Ga)Se 2 Solar Cell Absorbers. ACS Appl Mater Interfaces 2022; 14:34101-34112. [PMID: 35848892 DOI: 10.1021/acsami.2c08257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Alkali postdeposition treatments of Cu(In,Ga)Se2 absorbers with KF, RbF, and CsF have led to remarkable efficiency improvements for chalcopyrite thin film solar cells. However, the effect of such treatments on the electronic properties and defect physics of the chalcopyrite absorber surfaces are not yet fully understood. In this work, we use scanning tunneling spectroscopy and X-ray photoelectron spectroscopy to compare the surface defect electronic properties and chemical composition of RbF-treated and nontreated absorbers. We find that the RbF treatment is effective in passivating electronic defect levels at the surface by preventing surface oxidation. Our X-ray photoelectron spectroscopy (XPS) data points to the presence of chemisorbed Rb on the surface with a bonding configuration similar to that of a RbInSe2 bulk compound. Yet, a quantitative analysis indicates Rb coverage in the submonolayer regime, which is likely causing the surface passivation. Furthermore, ab initio calculations confirm that RbF-treated surfaces are less prone to oxidation (in the form of Ga, In, and Se oxides) than bare chalcopyrite surfaces. In addition, elemental diffusion of Rb along with Na, Cu, and Ga is found to occur when the samples are annealed under ultrahigh vacuum conditions. Magnetic sector secondary ion mass spectrometry measurements indicate that there is a homogeneous spatial distribution of Rb on the surface both before and after annealing, albeit with an increased concentration at the surface after heat treatment. Depth-resolved magnetic sector secondary ion mass spectrometry measurements show that Rb diffusion within the bulk occurs predominantly along grain boundaries. Scanning tunneling and XPS measurements after subsequent annealing steps demonstrate that the Rb accumulation at the surface leads to the formation of metallic Rb phases, involving a significant increase of electronic defect levels and/or surface dipole formation. These results strongly suggest a deterioration of the absorber-window interface because of increased recombination losses after the heat-induced diffusion of Rb toward the interface.
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Affiliation(s)
- Amala Elizabeth
- Physikalisches Institut, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Strasse 10, Münster 48149, Germany
- Center for Nanotechnology (CeNTech), Heisenbergstrasse 11, Münster 48149, Germany
| | - Sudhir K Sahoo
- Dynamics of Condensed Matter and Center for Sustainable Systems Design, University of Paderborn, Warburger Strasse 100, Paderborn D-33098, Germany
| | - Himanshu Phirke
- Department of Physics and Materials Science, Université du Luxembourg, 162 A, avenue de la Faïencerie, Luxembourg City L-1511 Luxembourg
| | - Tim Kodalle
- PVcomB/Helmholtz-Zentrum Berlin für Materialien und Energie, Schwarzschildstrasse 3, Berlin 12489, Germany
| | - Thomas D Kühne
- Dynamics of Condensed Matter and Center for Sustainable Systems Design, University of Paderborn, Warburger Strasse 100, Paderborn D-33098, Germany
| | - Jean-Nicolas Audinot
- Advanced Instrumentation for Nano-Analytics (AINA), Materials Research and Technology Department (MRT), Luxembourg Institute of Science and Technology (LIST), Belvaux L-4362, Luxembourg
| | - Tom Wirtz
- Advanced Instrumentation for Nano-Analytics (AINA), Materials Research and Technology Department (MRT), Luxembourg Institute of Science and Technology (LIST), Belvaux L-4362, Luxembourg
| | - Alex Redinger
- Department of Physics and Materials Science, Université du Luxembourg, 162 A, avenue de la Faïencerie, Luxembourg City L-1511 Luxembourg
| | - Christian A Kaufmann
- PVcomB/Helmholtz-Zentrum Berlin für Materialien und Energie, Schwarzschildstrasse 3, Berlin 12489, Germany
| | - Hossein Mirhosseini
- Dynamics of Condensed Matter and Center for Sustainable Systems Design, University of Paderborn, Warburger Strasse 100, Paderborn D-33098, Germany
| | - Harry Mönig
- Physikalisches Institut, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Strasse 10, Münster 48149, Germany
- Center for Nanotechnology (CeNTech), Heisenbergstrasse 11, Münster 48149, Germany
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25
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Lin YH, Hsu CH, Jang I, Chen CJ, Chiu PM, Lin DS, Wu CT, Chuang FC, Chang PY, Hsu PJ. Proximity-Effect-Induced Anisotropic Superconductivity in a Monolayer Ni-Pb Binary Alloy. ACS Appl Mater Interfaces 2022; 14:23990-23997. [PMID: 35575457 DOI: 10.1021/acsami.2c03034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
A proximity effect facilitates the penetration of Cooper pairs that permits superconductivity in a normal metal, offering a promising approach to turn heterogeneous materials into superconductors and develop exceptional quantum phenomena. Here, we have systematically investigated proximity-induced anisotropic superconductivity in a monolayer Ni-Pb binary alloy by combining scanning tunneling microscopy/spectroscopy (STM/STS) with theoretical calculations. By means of high-temperature growth, the ( 3 3 × 3 3 ) R 30 o Ni-Pb surface alloy has been fabricated on Pb(111) and the appearance of a domain boundary as well as a structural phase transition can be deduced from a half-unit-cell lattice displacement. Given the high spatial and energy resolution, tunneling conductance (dI/dU) spectra have resolved the reduced but anisotropic superconducting gap ΔNiPb ≈ 1.0 meV, in stark contrast to the isotropic ΔPb ≈ 1.3 meV. In addition, the higher density of states at the Fermi energy (D(EF)) of the Ni-Pb surface alloy results in an enhancement of coherence peak height. According to the same Tc ≈ 7.1 K with Pb(111) from the temperature-dependent ΔNiPb and the short decay length Ld ≈ 3.55 nm from the spatially monotonic decrease of ΔNiPb, both results are supportive of a proximity-induced superconductivity. Despite a lack of a bulk counterpart, the atomically thick Ni-Pb bimetallic compound opens a pathway to engineer superconducting properties down to the two-dimensional limit, giving rise to the emergence of anisotropic superconductivity via a proximity effect.
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Affiliation(s)
- Yen-Hui Lin
- Department of Physics, National Tsing Hua University, Hsinchu 300044, Taiwan
| | - Chia-Hsiu Hsu
- Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
- Physics Division, National Center for Theoretical Sciences, Taipei 10617, Taiwan
| | - Iksu Jang
- Department of Physics, National Tsing Hua University, Hsinchu 300044, Taiwan
| | - Chia-Ju Chen
- Department of Physics, National Tsing Hua University, Hsinchu 300044, Taiwan
| | - Pok-Man Chiu
- Department of Physics, National Tsing Hua University, Hsinchu 300044, Taiwan
| | - Deng-Sung Lin
- Department of Physics, National Tsing Hua University, Hsinchu 300044, Taiwan
- Center for Quantum Technology, National Tsing Hua University, Hsinchu 300044, Taiwan
| | - Chien-Te Wu
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 300093, Taiwan
| | - Feng-Chuan Chuang
- Department of Physics, National Tsing Hua University, Hsinchu 300044, Taiwan
- Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
- Physics Division, National Center for Theoretical Sciences, Taipei 10617, Taiwan
| | - Po-Yao Chang
- Department of Physics, National Tsing Hua University, Hsinchu 300044, Taiwan
| | - Pin-Jui Hsu
- Department of Physics, National Tsing Hua University, Hsinchu 300044, Taiwan
- Center for Quantum Technology, National Tsing Hua University, Hsinchu 300044, Taiwan
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26
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Wu Q, Bagheri Tagani M, Zhang L, Wang J, Xia Y, Zhang L, Xie SY, Tian Y, Yin LJ, Zhang W, Rudenko AN, Wee ATS, Wong PKJ, Qin Z. Electronic Tuning in WSe 2/Au via van der Waals Interface Twisting and Intercalation. ACS Nano 2022; 16:6541-6551. [PMID: 35285624 DOI: 10.1021/acsnano.2c00916] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The transition metal dichalcogenide (TMD)-metal interfaces constitute an active part of TMD-based electronic devices with optimized performances. Despite their decisive role, current strategies for nanoscale electronic tuning remain limited. Here, we demonstrate electronic tuning in the WSe2/Au interface by twist engineering, capable of modulating the WSe2 carrier doping from an intrinsic p-type to n-type. Scanning tunneling microscope/spectroscopy gives direct evidence of enhanced interfacial interaction induced doping in WSe2 as the twist angle with respect to the topmost (100) lattice of gold changing from 15 to 0°. Taking advantage of the strong coupling interface achieved this way, we have moved a step further to realize an n-p-n-type WSe2 homojunction. The intrinsic doping of WSe2 can be recovered by germanium intercalation. Density functional theory calculations confirm that twist angle and intercalation-dependent charge transfer related doping are involved in our observations. Our work offers ways for electronically tuning the metal-2D semiconductor interface.
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Affiliation(s)
- Qilong Wu
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, PR China
| | - Meysam Bagheri Tagani
- Department of Physics, University of Guilan, P.O. Box 41335-1914, Rasht 32504550, Iran
| | - Lijie Zhang
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, PR China
| | - Jing Wang
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, PR China
| | - Yu Xia
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, PR China
| | - Li Zhang
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, PR China
| | - Sheng-Yi Xie
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, PR China
| | - Yuan Tian
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, PR China
| | - Long-Jing Yin
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, PR China
| | - Wen Zhang
- School of Microelectronics, Northwestern Polytechnical University, Xi'an 710072, Shaanxi & NPU Chongqing Technology Innovation Center, Chongqing 400000, PR China
| | - Alexander N Rudenko
- Institute for Molecules and Materials, Radboud University, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Andrew T S Wee
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551, Singapore
- Centre for Advanced 2D Materials (CA2DM) and Graphene Research Centre (GRC), National University of Singapore, 6 Science Drive 2, 117546, Singapore
| | - Ping Kwan Johnny Wong
- School of Microelectronics, Northwestern Polytechnical University, Xi'an 710072, Shaanxi & NPU Chongqing Technology Innovation Center, Chongqing 400000, PR China
| | - Zhihui Qin
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, PR China
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27
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Gatin AK, Sarvadii SY, Dokhlikova NV, Kharitonov VA, Ozerin SA, Shub BR, Grishin MV. Oxidation of Supported Nickel Nanoparticles at Low Exposure to O 2: Charging Effects and Selective Surface Activity. Nanomaterials (Basel) 2022; 12:nano12071038. [PMID: 35407156 PMCID: PMC9000863 DOI: 10.3390/nano12071038] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 03/10/2022] [Accepted: 03/18/2022] [Indexed: 01/27/2023]
Abstract
The oxidation of Ni nanoparticles supported on highly oriented pyrolytic graphite was investigated under conditions of low exposure to oxygen by methods of scanning tunneling microscopy and spectroscopy. It was found that charge transfer effects at the Ni-C interface influenced the surface activity of the nanoparticles. The O2 dissociation and the Ni oxidation were shown to occur only at the top of the nanoparticle, while the border of the Ni-C interface was the less preferable area for these processes. The O2 dissociation was inhibited, and atomic oxygen diffusion was suppressed in the given nanosystem, due to the decrease in holes concentration.
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28
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Liu X, Rahn MS, Ruan Q, Yakobson BI, Hersam MC. Probing borophene oxidation at the atomic scale. Nanotechnology 2022; 33:235702. [PMID: 35180715 DOI: 10.1088/1361-6528/ac56bd] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 02/18/2022] [Indexed: 06/14/2023]
Abstract
Two-dimensional boron (i.e. borophene) holds promise for a variety of emerging nanoelectronic and quantum technologies. Since borophene is synthesized under ultrahigh vacuum (UHV) conditions, it is critical that the chemical stability and structural integrity of borophene in oxidizing environments are understood for practical borophene-based applications. In this work, we assess the mechanism of borophene oxidation upon controlled exposure to air and molecular oxygen in UHV via scanning tunneling microscopy andspectroscopy, x-ray photoelectron spectroscopy, and density functional theory calculations. While borophene catastrophically degrades almost instantaneously upon exposure to air, borophene undergoes considerably more controlled oxidation when exposed to molecular oxygen in UHV. In particular, UHV molecular oxygen dosing results in single-atom covalent modification of the borophene basal plane in addition to disordered borophene edge oxidation that shows altered electronic characteristics. By comparing these experimental observations with density functional theory calculations, further atomistic insight is gained including pathways for molecular oxygen dissociation, surface diffusion, and chemisorption to borophene. Overall, this study provides an atomic-scale perspective of borophene oxidation that will inform ongoing efforts to passivate and utilize borophene in ambient conditions.
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Affiliation(s)
- Xiaolong Liu
- Applied Physics Graduate Program, Northwestern University, Evanston, IL, 60208, United States of America
| | - Matthew S Rahn
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208, United States of America
| | - Qiyuan Ruan
- Department of Materials Science and NanoEngineering, and Department of Chemistry, Rice University, Houston, TX, 77005, United States of America
| | - Boris I Yakobson
- Department of Materials Science and NanoEngineering, and Department of Chemistry, Rice University, Houston, TX, 77005, United States of America
| | - Mark C Hersam
- Applied Physics Graduate Program, Northwestern University, Evanston, IL, 60208, United States of America
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208, United States of America
- Department of Chemistry, Northwestern University, Evanston, IL, 60208, United States of America
- Department of Electrical and Computer Engineering, Northwestern University, Evanston, IL, 60208, United States of America
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29
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Rizzo D, Shabani S, Jessen BS, Zhang J, McLeod AS, Rubio-Verdú C, Ruta FL, Cothrine M, Yan J, Mandrus DG, Nagler SE, Rubio A, Hone JC, Dean CR, Pasupathy AN, Basov DN. Nanometer-Scale Lateral p-n Junctions in Graphene/α-RuCl 3 Heterostructures. Nano Lett 2022; 22:1946-1953. [PMID: 35226804 PMCID: PMC8915251 DOI: 10.1021/acs.nanolett.1c04579] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The ability to create nanometer-scale lateral p-n junctions is essential for the next generation of two-dimensional (2D) devices. Using the charge-transfer heterostructure graphene/α-RuCl3, we realize nanoscale lateral p-n junctions in the vicinity of graphene nanobubbles. Our multipronged experimental approach incorporates scanning tunneling microscopy (STM) and spectroscopy (STS) and scattering-type scanning near-field optical microscopy (s-SNOM) to simultaneously probe the electronic and optical responses of nanobubble p-n junctions. Our STM/STS results reveal that p-n junctions with a band offset of ∼0.6 eV can be achieved with widths of ∼3 nm, giving rise to electric fields of order 108 V/m. Concurrent s-SNOM measurements validate a point-scatterer formalism for modeling the interaction of surface plasmon polaritons (SPPs) with nanobubbles. Ab initio density functional theory (DFT) calculations corroborate our experimental data and reveal the dependence of charge transfer on layer separation. Our study provides experimental and conceptual foundations for generating p-n nanojunctions in 2D materials.
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Affiliation(s)
- Daniel
J. Rizzo
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Sara Shabani
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Bjarke S. Jessen
- Department
of Physics, Columbia University, New York, New York 10027, United States
- Department
of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Jin Zhang
- Theory
Department, Max Planck Institute for Structure
and Dynamics of Matter and Center for Free-Electron Laser Science, 22761 Hamburg, Germany
| | - Alexander S. McLeod
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Carmen Rubio-Verdú
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Francesco L. Ruta
- Department
of Physics, Columbia University, New York, New York 10027, United States
- Department
of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
| | - Matthew Cothrine
- Department
of Materials Science and Engineering, University
of Tennessee, Knoxville, Tennessee 37996, United States
| | - Jiaqiang Yan
- Department
of Materials Science and Engineering, University
of Tennessee, Knoxville, Tennessee 37996, United States
- Materials
Science and Technology Division, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - David G. Mandrus
- Department
of Materials Science and Engineering, University
of Tennessee, Knoxville, Tennessee 37996, United States
- Materials
Science and Technology Division, Oak Ridge
National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Stephen E. Nagler
- Neutron
Scattering Division, Oak Ridge National
Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Angel Rubio
- Theory
Department, Max Planck Institute for Structure
and Dynamics of Matter and Center for Free-Electron Laser Science, 22761 Hamburg, Germany
- Center
for Computational Quantum Physics, Flatiron
Institute, New York, New York 10010, United
States
- Nano-Bio
Spectroscopy Group, Universidad del País
Vasco UPV/EHU, San Sebastián 20018, Spain
| | - James C. Hone
- Department
of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Cory R. Dean
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Abhay N. Pasupathy
- Department
of Physics, Columbia University, New York, New York 10027, United States
- Condensed
Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - D. N. Basov
- Department
of Physics, Columbia University, New York, New York 10027, United States
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30
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Rizzo D, Jiang J, Joshi D, Veber G, Bronner C, Durr RA, Jacobse PH, Cao T, Kalayjian A, Rodriguez H, Butler P, Chen T, Louie SG, Fischer FR, Crommie MF. Rationally Designed Topological Quantum Dots in Bottom-Up Graphene Nanoribbons. ACS Nano 2021; 15:20633-20642. [PMID: 34842409 PMCID: PMC8717637 DOI: 10.1021/acsnano.1c09503] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Bottom-up graphene nanoribbons (GNRs) have recently been shown to host nontrivial topological phases. Here, we report the fabrication and characterization of deterministic GNR quantum dots whose orbital character is defined by zero-mode states arising from nontrivial topological interfaces. Topological control was achieved through the synthesis and on-surface assembly of three distinct molecular precursors designed to exhibit structurally derived topological electronic states. Using a combination of low-temperature scanning tunneling microscopy and spectroscopy, we have characterized two GNR topological quantum dot arrangements synthesized under ultrahigh vacuum conditions. Our results are supported by density-functional theory and tight-binding calculations, revealing that the magnitude and sign of orbital hopping between topological zero-mode states can be tuned based on the bonding geometry of the interconnecting region. These results demonstrate the utility of topological zero modes as components for designer quantum dots and advanced electronic devices.
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Affiliation(s)
- Daniel
J. Rizzo
- Department
of Physics, University of California, Berkeley, California 94720, United States
- Department
of Physics, Columbia University, New York, New York 10027, United States
| | - Jingwei Jiang
- Department
of Physics, University of California, Berkeley, California 94720, United States
- Materials
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Dharati Joshi
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
| | - Gregory Veber
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
| | - Christopher Bronner
- Department
of Physics, University of California, Berkeley, California 94720, United States
| | - Rebecca A. Durr
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
| | - Peter H. Jacobse
- Department
of Physics, University of California, Berkeley, California 94720, United States
| | - Ting Cao
- Department
of Physics, University of California, Berkeley, California 94720, United States
- Department
of Materials Science and Engineering, University
of Washington, Seattle, Washington 98195, United States
| | - Alin Kalayjian
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
| | - Henry Rodriguez
- Department
of Physics, University of California, Berkeley, California 94720, United States
| | - Paul Butler
- Department
of Physics, University of California, Berkeley, California 94720, United States
| | - Ting Chen
- Department
of Physics, University of California, Berkeley, California 94720, United States
| | - Steven G. Louie
- Department
of Physics, University of California, Berkeley, California 94720, United States
- Materials
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Felix R. Fischer
- Materials
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
- Department
of Chemistry, University of California, Berkeley, California 94720, United States
- Kavli Energy
NanoSciences Institute at the University of California Berkeley and
the Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Michael F. Crommie
- Department
of Physics, University of California, Berkeley, California 94720, United States
- Materials
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
- Kavli Energy
NanoSciences Institute at the University of California Berkeley and
the Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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31
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Peng W, Wang H, Lu H, Yin L, Wang Y, Grandidier B, Yang D, Pi X. Recent Progress on the Scanning Tunneling Microscopy and Spectroscopy Study of Semiconductor Heterojunctions. Small 2021; 17:e2100655. [PMID: 34337855 DOI: 10.1002/smll.202100655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 05/18/2021] [Indexed: 06/13/2023]
Abstract
The band alignment, interface states, interface coupling, and carrier transport of semiconductor heterojunctions (SHs) need to be well understood for the design and fabrication of various important semiconductor structures and devices. Scanning tunneling microscopy (STM) with high spatial resolution and scanning tunneling spectroscopy (STS) with high energy resolution are significantly contributing to the understanding on the important properties of SHs. In this work, the recent progress on the use of STM and STS to study lateral, vertical and bulk SHs is reviewed. The spatial structures of SHs with atomically flat surface have been examined with STM. The electronic band structures (e. g., the band offset, interface state, and space charge region) of SHs are measured with STS. Combined with the spatial structures and the tunneling spectra features, the mechanism for the carrier transport in the SH may be proposed.
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Affiliation(s)
- Wenbing Peng
- State Key Laboratory of Silicon Materials and School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang, 310027, China
| | - Haolin Wang
- State Key Laboratory of Silicon Materials and School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang, 310027, China
| | - Hui Lu
- Institute of Advanced Semiconductors, Hangzhou Innovation Center, Zhejiang University, Hangzhou, Zhejiang, 311215, China
| | - Lei Yin
- State Key Laboratory of Silicon Materials and School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang, 310027, China
| | - Yue Wang
- State Key Laboratory of Silicon Materials and School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang, 310027, China
| | - Bruno Grandidier
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, Junia-ISEN, UMR 8520 - IEMN, Lille, 59000, France
| | - Deren Yang
- State Key Laboratory of Silicon Materials and School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang, 310027, China
- Institute of Advanced Semiconductors, Hangzhou Innovation Center, Zhejiang University, Hangzhou, Zhejiang, 311215, China
| | - Xiaodong Pi
- State Key Laboratory of Silicon Materials and School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang, 310027, China
- Institute of Advanced Semiconductors, Hangzhou Innovation Center, Zhejiang University, Hangzhou, Zhejiang, 311215, China
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32
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Fardian-Melamed N, Katrivas L, Rotem D, Kotlyar A, Porath D. Electronic Level Structure of Novel Guanine Octuplex DNA Single Molecules. Nano Lett 2021; 21:8987-8992. [PMID: 34694812 DOI: 10.1021/acs.nanolett.1c02269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Throughout the past few decades, guanine quadruplex DNA structures have attracted much interest both from a fundamental material science perspective and from a technologically oriented perspective. Novel guanine octuplex DNA, formed from coiled quadruplex DNA, was recently discovered as a stable and rigid DNA-based nanostructure. A detailed electronic structure study of this new nanomaterial, performed by scanning tunneling spectroscopy on a subsingle-molecule level at cryogenic temperature, is presented herein. The electronic levels and lower energy gap of guanine octuplex DNA compared to quadruplex DNA dictate higher transverse conductivity through guanine octads than through guanine tetrads.
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Affiliation(s)
- Natalie Fardian-Melamed
- Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Liat Katrivas
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, and The Center of Nanoscience and Nanotechnology, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
| | - Dvir Rotem
- Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Alexander Kotlyar
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, and The Center of Nanoscience and Nanotechnology, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
| | - Danny Porath
- Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
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33
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Abstract
Pursuing the confinement of linearly dispersive relativistic Fermions is of interest in both fundamental physics and potential applications. Here, we report strong STM evidence for the equally spaced, strikingly sharp, and densely distributed quantum well states (QWSs) near Fermi energy in Pb(111) nanoislands, van der Waals epitaxially grown on graphitized 6H-SiC(0001). The observations can be explained as the quantized energies of confined linearly dispersive [111] electrons, which essentially "simulate" the out-of-plane relativistic quasiparticles. The equally spaced QWSs with an origin of confined relativistic electrons are supported by phenomenological simulations and Fabry-Pérot fittings based on the relativistic Fermions. First-principles calculations further reveal that the spin-orbit coupling strengthens the relativistic nature of electrons near Fermi energy. Our finding uncovers the unique equally spaced quantum states in electronic systems beyond Landau levels and may inspire future studies on confined relativistic quasiparticles in flourishing topological materials and applications in structurally simpler quantum cascade laser.
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Affiliation(s)
- Chaofei Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Chunxiang Zhao
- International Laboratory for Quantum Functional Materials of Henan, and School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450001, China
| | - Shan Zhong
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Cheng Chen
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Zhenyu Zhang
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
| | - Yu Jia
- International Laboratory for Quantum Functional Materials of Henan, and School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450001, China
| | - Jian Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
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34
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Sun X, Chen Y, Li Z, Han Y, Zhou Q, Wang B, Taniguchi T, Watanabe K, Zhao A, Wang J, Liu Y, Xue J. Visualizing Band Profiles of Gate-Tunable Junctions in MoS 2/WSe 2 Heterostructure Transistors. ACS Nano 2021; 15:16314-16321. [PMID: 34651496 DOI: 10.1021/acsnano.1c05491] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Heterostructure devices based on two-dimensional materials have been under intensive study due to their intriguing electrical and optical properties. One key factor in understanding these devices is their nanometer-scale band profiles, which is challenging to obtain in devices. Here, we use a technique named contact-mode scanning tunneling spectroscopy to directly visualize the band profiles of MoS2/WSe2 heterostructure devices at different gate voltages with nanometer resolution. The long-held view of a conventional p-n junction in the MoS2/WSe2 heterostructure is reexamined. Due to strong inter- and intralayer charge transfer, the MoS2 layer in contact with WSe2 is found to convert from n-type to p-type, and a series of gate-tunable p-n and p-p+ junctions are developed in the devices. Highly conductive edges are also discovered which could strongly affect the device properties.
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Affiliation(s)
- Xinzuo Sun
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
- University of Chinese Academy of Sciences, Beijing 100190, China
| | - Yan Chen
- Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China
| | - Zhiwei Li
- School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Yu Han
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Qin Zhou
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Binbin Wang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Aidi Zhao
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Jianlu Wang
- Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China
| | - Yuan Liu
- School of Physics and Electronics, Hunan University, Changsha 410082, China
| | - Jiamin Xue
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
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35
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Dan S, Maiti A, Chatterjee S, Pal AJ. Origin of bandgap bowing in Cs 2Na 1-xAg xBiCl 6double perovskite solid-state alloys: a paradigm through scanning tunneling spectroscopy. J Phys Condens Matter 2021; 33:485701. [PMID: 34479226 DOI: 10.1088/1361-648x/ac238c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2021] [Accepted: 09/03/2021] [Indexed: 06/13/2023]
Abstract
Bandgap bowing has recently been emerged as an effective strategy toward band-engineering in metal halide perovskites. In this work, we report extensive studies on the bowing phenomenon in Cs2NaBiCl6double perovskite upon alloying with silver at the sodium site. Through optical spectroscopy, composition-dependent bandgap in Cs2Na1-xAgxBiCl6(0 ⩽x⩽ 1) evidenced bandgap bowing with an upward-concave nature. Further from the quadratic fit, the bowing coefficient (b= 0.74 eV) turned out to be independent of composition and is close to the theoretically predicted value. From scanning tunneling spectroscopy and associated studies on band-energies, we have observed that the bandgap-lowering originated from a significant change of the valence-band position. The behavior of band-energies has been explained through the orbital-contributions of the constituent elements responsible in forming the two bands. Formation of an internal type-I band-alignment between the two end-members, namely Cs2NaBiCl6and Cs2AgBiCl6could be visualized. Based on experimental evidences, we could infer that the bow-like evolution of bandgap in Cs2Na1-xAgxBiCl6alloys is principally dominated by structural distortions in the Cs2NaBiCl6host-lattice upon incorporation of silver.
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Affiliation(s)
- Soirik Dan
- School of Physical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
| | - Abhishek Maiti
- School of Physical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
| | - Soumyo Chatterjee
- School of Physical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
| | - Amlan J Pal
- School of Physical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
- UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001, India
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36
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Jarschel P, Kim JH, Biadala L, Berthe M, Lambert Y, Osgood RM, Patriarche G, Grandidier B, Xu J. Single-Electron Tunneling PbS/InP Heterostructure Nanoplatelets for Synaptic Operations. ACS Appl Mater Interfaces 2021; 13:38450-38457. [PMID: 34357748 DOI: 10.1021/acsami.1c06096] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Power consumption, thermal management, and wiring challenge of the binary serial architecture drive the search for alternative paradigms to computing. Of special interest is neuromorphic computing, in which materials and device structures are designed to mimic neuronal functionalities with energy-efficient non-linear responses and both short- and long-term plasticities. In this work, we explore and report on the enabling potential of single-electron tunneling (SET) in PbS nanoplatelets epitaxially grown in the liquid phase on InP, which present these key features. By extrapolating the experimental data in the SET regime, we predict and model synaptic operations. The low-energy (<fJ), high-speed (MHz) operation and scalable fabrication process of the PbS/InP nanoplatelets make such a nanoscale system attractive as neuromorphic computing building blocks.
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Affiliation(s)
- Paulo Jarschel
- School of Engineering, Brown University, Providence 02912, Rhode Island, United States
- Photonics Research Center, University of Campinas, Campinas 13083-859, São Paulo, Brazil
- Quantum Electronics Department, Gleb Wataghin Physics Institute, University of Campinas, Campinas 13083-859, São Paulo, Brazil
| | - Jin Ho Kim
- School of Engineering, Brown University, Providence 02912, Rhode Island, United States
| | - Louis Biadala
- University of Lille, CNRS, Centrale Lille, University of Polytechnique Hauts-de-France, Junia-ISEN, UMR 8520-IEMN, Lille 59000, France
| | - Maxime Berthe
- University of Lille, CNRS, Centrale Lille, University of Polytechnique Hauts-de-France, Junia-ISEN, UMR 8520-IEMN, Lille 59000, France
| | - Yannick Lambert
- University of Lille, CNRS, Centrale Lille, University of Polytechnique Hauts-de-France, Junia-ISEN, UMR 8520-IEMN, Lille 59000, France
| | - Richard M Osgood
- US Army Combat Capabilities Development Command-Soldier Center, 15 General Greene Avenue, Natick, Massachusetts 01760, United States
| | - Gilles Patriarche
- Centre de Nanosciences et de Nanotechnologies (C2N), UMR 9001 CNRS, University Paris-Saclay, Avenue de la Vauve, Palaiseau 91120, France
| | - Bruno Grandidier
- University of Lille, CNRS, Centrale Lille, University of Polytechnique Hauts-de-France, Junia-ISEN, UMR 8520-IEMN, Lille 59000, France
| | - Jimmy Xu
- School of Engineering, Brown University, Providence 02912, Rhode Island, United States
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37
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Roccapriore KM, Zou Q, Zhang L, Xue R, Yan J, Ziatdinov M, Fu M, Mandrus DG, Yoon M, Sumpter BG, Gai Z, Kalinin SV. Revealing the Chemical Bonding in Adatom Arrays via Machine Learning of Hyperspectral Scanning Tunneling Spectroscopy Data. ACS Nano 2021; 15:11806-11816. [PMID: 34181383 DOI: 10.1021/acsnano.1c02902] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The adatom arrays on surfaces offer an ideal playground to explore the mechanisms of chemical bonding via changes in the local electronic tunneling spectra. While this information is readily available in hyperspectral scanning tunneling spectroscopy data, its analysis has been considerably impeded by a lack of suitable analytical tools. Here we develop a machine learning based workflow combining supervised feature identification in the spatial domain and unsupervised clustering in the energy domain to reveal the details of structure-dependent changes of the electronic structure in adatom arrays on the Co3Sn2S2 cleaved surface. This approach, in combination with first-principles calculations, provides insight for using artificial neural networks to detect adatoms and classifies each based on their local neighborhood comprised of other adatoms. These structurally classified adatoms are further spectrally deconvolved. The unexpected inhomogeneity of electronic structures among adatoms in similar configurations is unveiled using this method, suggesting there is not a single atomic species of adatoms, but rather multiple types of adatoms on the Co3Sn2S2 surface. This is further supported by a slight contrast difference in the images (or slight size variation) of the topography of the adatoms.
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Affiliation(s)
- Kevin M Roccapriore
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Qiang Zou
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Lizhi Zhang
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Rui Xue
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Jiaqiang Yan
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Maxim Ziatdinov
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Mingming Fu
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - David G Mandrus
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Mina Yoon
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Bobby G Sumpter
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Zheng Gai
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Sergei V Kalinin
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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38
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Behn WA, Krebs ZJ, Smith KJ, Watanabe K, Taniguchi T, Brar VW. Measuring and Tuning the Potential Landscape of Electrostatically Defined Quantum Dots in Graphene. Nano Lett 2021; 21:5013-5020. [PMID: 34096737 DOI: 10.1021/acs.nanolett.1c00791] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We use Kelvin probe force microscopy (KPFM) to probe the carrier-dependent potential of an electrostatically defined quantum dot (QD) in a graphene/hexagonal boron nitride (hBN) heterostructure. We show that gate-dependent measurements enable a calibration scheme that corrects for uncertainty inherent in typical KPFM measurements and accurately reconstructs the potential well profile. Our measurements reveal how the well changes with carrier concentration, which we associate with the nonlinear dependence of graphene's work function on carrier density. These changes shift the energy levels of quasi-bound states in the QD which we can measure via scanning tunneling spectroscopy (STS). We show that the experimentally extracted energy levels closely compare with wave functions calculated from the reconstructed KPFM data. This methodology, where KPFM and STS data are simultaneously acquired from 2D materials, allows the quasiparticle response to an electrostatic potential to be determined in a self-consistent way.
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Affiliation(s)
- Wyatt A Behn
- Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706, United States
| | - Zachary J Krebs
- Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706, United States
| | - Keenan J Smith
- Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706, United States
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Victor W Brar
- Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706, United States
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39
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Benhnia A, Watanabe S, Tuerhong R, Nakaya M, Onoe J, Bucher JP. Resolving Site-Specific Energy Levels of Small-Molecule Donor-Acceptor Heterostructures Close to Metal Contacts. Nanomaterials (Basel) 2021; 11:nano11061618. [PMID: 34203037 PMCID: PMC8234413 DOI: 10.3390/nano11061618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Revised: 06/15/2021] [Accepted: 06/17/2021] [Indexed: 11/16/2022]
Abstract
The active material of optoelectronic devices must accommodate for contacts which serve to collect or inject the charge carriers. It is the purpose of this work to find out to which extent properties of organic optoelectronic layers change close to metal contacts compared to known properties of bulk materials. Bottom-up fabrication capabilities of model interfaces under ultrahigh vacuum and single-atom low temperature (LT)-STM spectroscopy with density functional theory (DFT) calculations are used to detect the spatial modifications of electronic states such as frontier-orbitals at interfaces. The system under consideration is made of a silver substrate covered with a blend of C60 and ZnPc molecules of a few monolayers. When C60 and ZnPc are separately adsorbed on Ag(111), they show distinct spectroscopic features in STM. However, when C60 is added to the ZnPc monolayer, it shows scanning tunneling spectra similar to ZnPc, revealing a strong interaction of C60 with the ZnPc induced by the substrate. DFT calculations on a model complex confirm the strong hybridization of C60 with ZnPc layer upon adsorption on Ag(111), thus highlighting the role of boundary layers where the donor-acceptor character is strongly perturbed. The calculation also reveals a significant charge transfer from the Ag to the complex that is likely responsible for a downward shift of the molecular LUMO in agreement with the experiment.
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Affiliation(s)
- Amani Benhnia
- Institutde Physiqueet Chimiedes Matériaux de Strasbourg (IPCMS), Université de Strasbourg, CNRS, IPCMS UMR 7504, F-67034 Strasbourg, France; (A.B.); (R.T.)
| | - Shinta Watanabe
- Department of Energy Science and Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan; (S.W.); (M.N.); (J.O.)
| | - Rouzhaji Tuerhong
- Institutde Physiqueet Chimiedes Matériaux de Strasbourg (IPCMS), Université de Strasbourg, CNRS, IPCMS UMR 7504, F-67034 Strasbourg, France; (A.B.); (R.T.)
| | - Masato Nakaya
- Department of Energy Science and Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan; (S.W.); (M.N.); (J.O.)
| | - Jun Onoe
- Department of Energy Science and Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan; (S.W.); (M.N.); (J.O.)
| | - Jean-Pierre Bucher
- Institutde Physiqueet Chimiedes Matériaux de Strasbourg (IPCMS), Université de Strasbourg, CNRS, IPCMS UMR 7504, F-67034 Strasbourg, France; (A.B.); (R.T.)
- Correspondence:
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40
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Paramanik S, Chatterjee S, Pal AJ. Reverse bandgap-bowing in nickel-cadmium sulfide alloys (Ni 1-xCd xS) and its origin. J Phys Condens Matter 2021; 33:245703. [PMID: 33631725 DOI: 10.1088/1361-648x/abe9d8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 02/25/2021] [Indexed: 06/12/2023]
Abstract
We present evolution of band energies in α-NiS when alloyed with a cationic doping through isovalent cadmium (Cd2+). Optical bandgap of nickel-cadmium sulfide (Ni1-xCdxS) alloys, as a deviation from the linear relationship or Vegard's law, have exhibited a reverse bandgap-bowing in the form of downward-concave dependence. Such a phenomenon, which manifests as a negative value of bowing coefficient (b), is uncommon in chalcogenide alloys. In this work, we have deliberated on the origin of reverse bandgap-bowing in nickel-cadmium alloys and identified the band responsible for the bowing phenomenon. While thin-films of the alloys were formed through successive ionic layer adsorption and reaction method, tunnel conductance and thereby density of states of the materials were derived from scanning tunneling spectroscopy. The spectroscopy provided the variation of conduction and valence band-edges (CB and VB, respectively) with respect to the cadmium-content in Ni1-xCdxS. The CB-edge of the alloys could be seen to remain mostly unaffected with increasing cadmium-content, since the band is composed of only the S 2porbitals; the VB-energy, on the other hand, which forms due to an effective coupling between the metaldand the anionporbitals, could be seen to be affected due to ap-drepulsion. Based on our experimental findings, we inferred that an antagonism between volume deformation and structural relaxation had resulted in the reverse bandgap-bowing in Ni1-xCdxS alloys.
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Affiliation(s)
- Subham Paramanik
- School of Physical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
| | - Soumyo Chatterjee
- School of Physical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
| | - Amlan J Pal
- School of Physical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
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41
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Abstract
Atomically thin metal-semiconductor heterojunctions are highly desirable for nanoelectronic applications. However, coherent lateral stitching of distinct two-dimensional (2D) materials has traditionally required interfacial lattice matching and compatible growth conditions, which remains challenging for most systems. On the other hand, these constraints are relaxed in 2D/1D mixed-dimensional lateral heterostructures due to the increased structural degree of freedom. Here, we report the self-assembly of mixed-dimensional lateral heterostructures consisting of 2D metallic borophene and 1D semiconducting armchair-oriented graphene nanoribbons (aGNRs). With the sequential ultrahigh vacuum deposition of boron and 4,4″-dibromo-p-terphenyl as precursors on Ag(111) substrates, an on-surface polymerization process is systematically studied and refined including the transition from monomers to organometallic intermediates and finally demetallization that results in borophene/aGNR lateral heterostructures. High-resolution scanning tunneling microscopy and spectroscopy resolve the structurally and electronically abrupt interfaces in borophene/aGNR heterojunctions, thus providing insight that will inform ongoing efforts in pursuit of atomically precise nanoelectronics.
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Affiliation(s)
- Qiucheng Li
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
- Soochow Institute for Energy and Materials InnovationS (SIEMIS), Jiangsu Provincial Key Laboratory for Advanced Carbon Materials and Wearable Energy Technologies, Soochow University, Suzhou 215006, P. R. China
| | - Xiaolong Liu
- Applied Physics Graduate Program, Northwestern University, Evanston, Illinois 60208, United States
| | - Eden B Aklile
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Shaowei Li
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Mark C Hersam
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
- Applied Physics Graduate Program, Northwestern University, Evanston, Illinois 60208, United States
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
- Department of Electrical and Computer Engineering, Northwestern University, Evanston, Illinois 60208, United States
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42
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Deng J, Ablat G, Yang Y, Fu X, Wu Q, Li P, Zhang L, Safaei A, Zhang L, Qin Z. Two-dimensional germanium islands with Dirac signature on Ag 2Ge surface alloy. J Phys Condens Matter 2021; 33:225001. [PMID: 33596556 DOI: 10.1088/1361-648x/abe731] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Accepted: 02/17/2021] [Indexed: 06/12/2023]
Abstract
Two-dimensional (2D) Dirac materials have attracted intense research efforts due to their promise for applications ranging from field-effect transistors and low-power electronics to fault-tolerant quantum computation. One key challenge is to fabricate 2D Dirac materials hosting Dirac electrons. Here, monolayer germanene is successfully fabricated on a Ag2Ge surface alloy. Scanning tunneling spectroscopy measurements revealed a linear energy dispersion relation. The latter was supported by density functional theory calculations. These results demonstrate that monolayer germanene can be realistically fabricated on a Ag2Ge surface alloy. The finding opens the door to exploration and study of 2D Dirac material physics and device applications.
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Affiliation(s)
- Jiaqi Deng
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha, 410082, People's Republic of China
| | - Gulnigar Ablat
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha, 410082, People's Republic of China
| | - Yumu Yang
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha, 410082, People's Republic of China
| | - Xiaoshuai Fu
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha, 410082, People's Republic of China
| | - Qilong Wu
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha, 410082, People's Republic of China
| | - Ping Li
- Center for Spintronics and Quantum Systems, State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi, 710049, People's Republic of China
| | - Li Zhang
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha, 410082, People's Republic of China
| | - Ali Safaei
- Metallurgy and Materials Engineering Department, University of Gonabad, Khorasan Razavi, Iran
| | - Lijie Zhang
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha, 410082, People's Republic of China
| | - Zhihui Qin
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha, 410082, People's Republic of China
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43
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Montero AM, Guimarães FSM, Lounis S. Multiple magnetic states of CoPc molecule on a two-dimensional layer of NbSe 2. J Phys Condens Matter 2021; 33:205802. [PMID: 33704093 DOI: 10.1088/1361-648x/abed64] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Accepted: 03/10/2021] [Indexed: 06/12/2023]
Abstract
Molecular spintronics hinges on the detailed understanding of electronic and magnetic properties of molecules interfaced with various materials. Here we demonstrate withab initiosimulations that the prototypical Co-phthalocyanine (CoPc) molecule can surprisingly develop multi-spin states once deposited on the two-dimensional 2H-NbSe2layer. Conventional calculations based on density functional theory (DFT) show the existence of low, regular and high spin states, which reduce to regular and high spins states once correlations are incorporated with a DFT +Uapproach. Depending onU, the ground state is either the low spin or high spin state with energy differences affected by the molecular orientation on top of the substrate. Our results are compared to recent scanning probe measurements and motivate further theoretical and experimental studies on the unveiled rich multi-magnetic behavior of CoPc molecule.
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Affiliation(s)
- Ana M Montero
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszetrum Jülich and JARA, 52425 Jülich, Germany
| | - Filipe S M Guimarães
- Jülich Supercomputing Centre, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
| | - Samir Lounis
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszetrum Jülich and JARA, 52425 Jülich, Germany
- Faculty of Physics, University of Duisburg-Essen and CENIDE, 47053 Duisburg, Germany
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44
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Acharya J, Goul R, Wu J. High Tunneling Magnetoresistance in Magnetic Tunnel Junctions with Subnanometer Thick Al 2O 3 Tunnel Barriers Fabricated Using Atomic Layer Deposition. ACS Appl Mater Interfaces 2021; 13:15738-15745. [PMID: 32639721 DOI: 10.1021/acsami.0c03428] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Pinhole-free and defect-free ultrathin dielectric tunnel barriers (TBs) are a key to obtaining high-tunneling magnetoresistance (TMR) and efficient switching in magnetic tunnel junctions (MTJs). Among others, atomic layer deposition (ALD) provides a unique approach for the fabrication of ultrathin TBs with several advantages including atomic-scale control over the TB thickness, conformal coating, and a low defect density. Motivated by this, this work explores the fabrication and characterization of spin-valve Fe/ALD-Al2O3/Fe MTJs with an ALD-Al2O3 TB thickness of 0.55 nm using in situ ALD. Remarkably, high TMR values of ∼77 and ∼90% have been obtained, respectively, at room temperature and at 100 K, which are comparable to the best reported values on MTJs having thermal AlOx TBs with optimized device structures. In situ scanning tunneling spectroscopy characterization of the ALD-Al2O3 TBs has revealed a higher TB height (Eb) of 1.33 ± 0.06 eV, in contrast to Eb ∼ 0.3-0.6 eV for their AlOx TB counterparts, indicative of significantly lower defect concentrations in the former. This first success of the MTJs with subnanometer thick ALD-Al2O3 TBs demonstrates the feasibility of in situ ALD for the fabrication of pinhole-free and low-defect ultrathin TBs for practical applications, and the performance could be further improved through device optimization.
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Affiliation(s)
- Jagaran Acharya
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Ryan Goul
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Judy Wu
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
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45
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Wu Q, Fu X, Yang K, Wu H, Liu L, Zhang L, Tian Y, Yin LJ, Huang WQ, Zhang W, Wong PKJ, Zhang L, Wee ATS, Qin Z. Promoting a Weak Coupling of Monolayer MoSe 2 Grown on (100)-Faceted Au Foil. ACS Nano 2021; 15:4481-4489. [PMID: 33656862 DOI: 10.1021/acsnano.0c08513] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
As a two-dimensional semiconductor with many physical properties, including, notably, layer-controlled electronic bandgap and coupled spin-valley degree of freedom, monolayer MoSe2 is a strong candidate material for next-generation opto- and valley-electronic devices. However, due to substrate effects such as lattice mismatch and dielectric screening, preserving the monolayer's intrinsic properties remains challenging. This issue is generally significant for metallic substrates whose active surfaces are commonly utilized to achieve direct chemical or physical vapor growth of the monolayer films. Here, we demonstrate high-temperature-annealed Au foil with well-defined (100) facets as a weakly interacting substrate for atmospheric pressure chemical vapor deposition of highly crystalline monolayer MoSe2. Low-temperature scanning tunneling microscopy/spectroscopy measurements reveal a honeycomb structure of MoSe2 with a quasi-particle bandgap of 1.96 eV, a value comparable with other weakly interacting systems such as MoSe2/graphite. Density functional theory calculations indicate that the Au(100) surface exhibits the preferred energetics to electronically decouple from MoSe2, compared with the (110) and (111) crystal planes. This weak coupling is critical for the easy transfer of monolayers to another host substrate. Our study demonstrates a practical means to produce high-quality monolayers of transition-metal dichalcogenides, viable for both fundamental and application studies.
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Affiliation(s)
- Qilong Wu
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Xiaoshuai Fu
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Ke Yang
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Hongyu Wu
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Li Liu
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Li Zhang
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Yuan Tian
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Long-Jing Yin
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Wei-Qing Huang
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Wen Zhang
- School of Microelectronics & School of Electronics and Information, Northwestern Polytechnical University, Xi'an 710072, People's Republic of China
| | - Ping Kwan Johnny Wong
- School of Microelectronics & School of Electronics and Information, Northwestern Polytechnical University, Xi'an 710072, People's Republic of China
| | - Lijie Zhang
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
| | - Andrew T S Wee
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117551, Singapore
- Centre for Advanced 2D Materials (CA2DM) and Graphene Research Centre (GRC), National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore
| | - Zhihui Qin
- Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
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46
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Peric N, Lambert Y, Singh S, Khan AH, Franchina Vergel NA, Deresmes D, Berthe M, Hens Z, Moreels I, Delerue C, Grandidier B, Biadala L. Van Hove Singularities and Trap States in Two-Dimensional CdSe Nanoplatelets. Nano Lett 2021; 21:1702-1708. [PMID: 33544602 DOI: 10.1021/acs.nanolett.0c04509] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Semiconductor nanoplatelets, which offer a compelling combination of the flatness of two-dimensional semiconductors and the inherent richness brought about by colloidal nanostructure synthesis, form an ideal and general testbed to investigate fundamental physical effects related to the dimensionality of semiconductors. With low temperature scanning tunnelling spectroscopy and tight binding calculations, we investigate the conduction band density of states of individual CdSe nanoplatelets. We find an occurrence of peaks instead of the typical steplike function associated with a quantum well, that rule out a free in-plane electron motion, in agreement with the theoretical density of states. This finding, along with the detection of deep trap states located on the edge facets, which also restrict the electron motion, provides a detailed picture of the actual lateral confinement in quantum wells with finite length and width.
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Affiliation(s)
- Nemanja Peric
- Université de Lille, CNRS, Centrale Lille, Université Polytechnique Hauts-de-France, Junia-ISEN, Centrale Lille, UMR 8520 - IEMN, F-59000 Lille, France
| | - Yannick Lambert
- Université de Lille, CNRS, Centrale Lille, Université Polytechnique Hauts-de-France, Junia-ISEN, Centrale Lille, UMR 8520 - IEMN, F-59000 Lille, France
| | - Shalini Singh
- Physics and Chemistry of Nanostructures, Ghent University, 9000 Ghent, Belgium
| | - Ali Hossain Khan
- Physics and Chemistry of Nanostructures, Ghent University, 9000 Ghent, Belgium
| | - Nathali Alexandra Franchina Vergel
- Université de Lille, CNRS, Centrale Lille, Université Polytechnique Hauts-de-France, Junia-ISEN, Centrale Lille, UMR 8520 - IEMN, F-59000 Lille, France
| | - Dominique Deresmes
- Université de Lille, CNRS, Centrale Lille, Université Polytechnique Hauts-de-France, Junia-ISEN, Centrale Lille, UMR 8520 - IEMN, F-59000 Lille, France
| | - Maxime Berthe
- Université de Lille, CNRS, Centrale Lille, Université Polytechnique Hauts-de-France, Junia-ISEN, Centrale Lille, UMR 8520 - IEMN, F-59000 Lille, France
| | - Zeger Hens
- Physics and Chemistry of Nanostructures, Ghent University, 9000 Ghent, Belgium
| | - Iwan Moreels
- Physics and Chemistry of Nanostructures, Ghent University, 9000 Ghent, Belgium
| | - Christophe Delerue
- Université de Lille, CNRS, Centrale Lille, Université Polytechnique Hauts-de-France, Junia-ISEN, Centrale Lille, UMR 8520 - IEMN, F-59000 Lille, France
| | - Bruno Grandidier
- Université de Lille, CNRS, Centrale Lille, Université Polytechnique Hauts-de-France, Junia-ISEN, Centrale Lille, UMR 8520 - IEMN, F-59000 Lille, France
| | - Louis Biadala
- Université de Lille, CNRS, Centrale Lille, Université Polytechnique Hauts-de-France, Junia-ISEN, Centrale Lille, UMR 8520 - IEMN, F-59000 Lille, France
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47
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Sebait R, Biswas C, Song B, Seo C, Lee YH. Identifying Defect-Induced Trion in Monolayer WS 2 via Carrier Screening Engineering. ACS Nano 2021; 15:2849-2857. [PMID: 33470093 DOI: 10.1021/acsnano.0c08828] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Unusually high exciton binding energies (BEs), as much as ∼1 eV in monolayer transition-metal dichalcogenides, provide opportunities for exploring exotic and stable excitonic many-body effects. These include many-body neutral excitons, trions, biexcitons, and defect-induced excitons at room temperature, rarely realized in bulk materials. Nevertheless, the defect-induced trions correlated with charge screening have never been observed, and the corresponding BEs remain unknown. Here we report defect-induced A-trions and B-trions in monolayer tungsten disulfide (WS2) via carrier screening engineering with photogenerated carrier modulation, external doping, and substrate scattering. Defect-induced trions strongly couple with inherent SiO2 hole traps under high photocarrier densities and become more prominent in rhenium-doped WS2. The absence of defect-induced trion peaks was confirmed using a trap-free hexagonal boron nitride substrate, regardless of power density. Moreover, many-body excitonic charge states and their BEs were compared via carrier screening engineering at room temperature. The highest BE was observed in the defect-induced A-trion state (∼214 meV), comparably higher than the trion (209 meV) and neutral exciton (174 meV), and further tuned by external photoinduced carrier density control. This investigation allows us to demonstrate defect-induced trion BE localization via spatial BE mapping in the monolayer WS2 midflake regions distinctive from the flake edges.
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Kerelsky A, Rubio-Verdú C, Xian L, Kennes DM, Halbertal D, Finney N, Song L, Turkel S, Wang L, Watanabe K, Taniguchi T, Hone J, Dean C, Basov DN, Rubio A, Pasupathy AN. Moiréless correlations in ABCA graphene. Proc Natl Acad Sci U S A 2021; 118:e2017366118. [PMID: 33468646 PMCID: PMC7848726 DOI: 10.1073/pnas.2017366118] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Atomically thin van der Waals materials stacked with an interlayer twist have proven to be an excellent platform toward achieving gate-tunable correlated phenomena linked to the formation of flat electronic bands. In this work we demonstrate the formation of emergent correlated phases in multilayer rhombohedral graphene--a simple material that also exhibits a flat electronic band edge but without the need of having a moiré superlattice induced by twisted van der Waals layers. We show that two layers of bilayer graphene that are twisted by an arbitrary tiny angle host large (micrometer-scale) regions of uniform rhombohedral four-layer (ABCA) graphene that can be independently studied. Scanning tunneling spectroscopy reveals that ABCA graphene hosts an unprecedentedly sharp van Hove singularity of 3-5-meV half-width. We demonstrate that when this van Hove singularity straddles the Fermi level, a correlated many-body gap emerges with peak-to-peak value of 9.5 meV at charge neutrality. Mean-field theoretical calculations for model with short-ranged interactions indicate that two primary candidates for the appearance of this broken symmetry state are a charge-transfer excitonic insulator and a ferrimagnet. Finally, we show that ABCA graphene hosts surface topological helical edge states at natural interfaces with ABAB graphene which can be turned on and off with gate voltage, implying that small-angle twisted double-bilayer graphene is an ideal programmable topological quantum material.
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Affiliation(s)
| | | | - Lede Xian
- Theory Department, Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany
- Frontier Research Center, Songshan Lake Materials Laboratory, 523808 Dongguan, Guangdong, China
| | - Dante M Kennes
- Theory Department, Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany
- Institut für Theorie der Statistischen Physik, Rheinisch-Westfälische Technische Hochschule Aachen University, 52056 Aachen, Germany
- Jülich Aachen Research Alliance-Fundamentals of Future Information Technology, 52056 Aachen, Germany
| | - Dorri Halbertal
- Department of Physics, Columbia University, New York, NY 10027
| | - Nathan Finney
- Department of Mechanical Engineering, Columbia University, New York, NY 10027
| | - Larry Song
- Department of Physics, Columbia University, New York, NY 10027
| | - Simon Turkel
- Department of Physics, Columbia University, New York, NY 10027
| | - Lei Wang
- Department of Physics, Columbia University, New York, NY 10027
| | - Kenji Watanabe
- National Institute for Materials Science, 1-1 Namiki, 305-0044 Tsukuba, Japan
| | - Takashi Taniguchi
- National Institute for Materials Science, 1-1 Namiki, 305-0044 Tsukuba, Japan
| | - James Hone
- Department of Mechanical Engineering, Columbia University, New York, NY 10027
| | - Cory Dean
- Department of Physics, Columbia University, New York, NY 10027
| | - Dmitri N Basov
- Department of Physics, Columbia University, New York, NY 10027
| | - Angel Rubio
- Theory Department, Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany;
- Center for Computational Quantum Physics, The Flatiron Institute, New York, NY 10010
- Nano-Bio Spectroscopy Group, Departamento de Fisica de Materiales, Universidad del País Vasco, 20018 San Sebastian, Spain
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49
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Sarvadii SY, Gatin AK, Kharitonov VA, Dokhlikova NV, Ozerin SA, Grishin MV, Shub BR. Effect of CO Molecule Orientation on the Reduction of Cu-Based Nanoparticles. Nanomaterials (Basel) 2021; 11:nano11020279. [PMID: 33498990 PMCID: PMC7912012 DOI: 10.3390/nano11020279] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 01/14/2021] [Accepted: 01/20/2021] [Indexed: 11/16/2022]
Abstract
The adsorption of CO on the surface of Cu-based nanoparticles was studied in the presence of an external electric field by means of scanning tunneling microscopy (STM) and spectroscopy (STS). Nanoparticles were synthesized on the surface of a graphite support by the impregnation-precipitation method. The chemical composition of the surface of the nanoparticles was determined as a mixture of Cu2O, Cu4O3 and CuO oxides. CO was adsorbed from the gas phase onto the surface of the nanoparticles. During the adsorption process, the potential differences ΔV = +1 or -1 V were applied to the vacuum gap between the sample and the grounded tip. Thus, the system of the STM tip and sample surface formed an asymmetric capacitor, inside which an inhomogeneous electric field existed. The CO adsorption process is accompanied by the partial reduction of nanoparticles. Due to the orientation of the CO molecule in the electric field, the reduction was weak in the case of a positive potential difference, while in the case of a negative potential difference, the reduction rate increased significantly. The ability to control the adsorption process of CO by means of an external electric field was demonstrated. The size of the nanoparticle was shown to be the key factor affecting the adsorption process, and particularly, the strength of the local electric field close to the nanoparticle surface.
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50
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Franchina Vergel NA, Post LC, Sciacca D, Berthe M, Vaurette F, Lambert Y, Yarekha D, Troadec D, Coinon C, Fleury G, Patriarche G, Xu T, Desplanque L, Wallart X, Vanmaekelbergh D, Delerue C, Grandidier B. Engineering a Robust Flat Band in III-V Semiconductor Heterostructures. Nano Lett 2021; 21:680-685. [PMID: 33337891 DOI: 10.1021/acs.nanolett.0c04268] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Electron states in semiconductor materials can be modified by quantum confinement. Adding to semiconductor heterostructures the concept of lateral geometry offers the possibility to further tailor the electronic band structure with the creation of unique flat bands. Using block copolymer lithography, we describe the design, fabrication, and characterization of multiorbital bands in a honeycomb In0.53Ga0.47As/InP heterostructure quantum well with a lattice constant of 21 nm. Thanks to an optimized surface quality, scanning tunnelling spectroscopy reveals the existence of a strong resonance localized between the lattice sites, signature of a p-orbital flat band. Together with theoretical computations, the impact of the nanopatterning imperfections on the band structure is examined. We show that the flat band is protected against the lateral and vertical disorder, making this industry-standard system particularly attractive for the study of exotic phases of matter.
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Affiliation(s)
- Nathali A Franchina Vergel
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, Junia-ISEN, UMR 8520 - IEMN, 59000 Lille, France
| | - L Christiaan Post
- Debye Institute for Nanomaterials Science, Utrecht University, 3508 TA Utrecht, The Netherlands
| | - Davide Sciacca
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, Junia-ISEN, UMR 8520 - IEMN, 59000 Lille, France
| | - Maxime Berthe
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, Junia-ISEN, UMR 8520 - IEMN, 59000 Lille, France
| | - François Vaurette
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, Junia-ISEN, UMR 8520 - IEMN, 59000 Lille, France
| | - Yannick Lambert
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, Junia-ISEN, UMR 8520 - IEMN, 59000 Lille, France
| | - Dmitri Yarekha
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, Junia-ISEN, UMR 8520 - IEMN, 59000 Lille, France
| | - David Troadec
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, Junia-ISEN, UMR 8520 - IEMN, 59000 Lille, France
| | - Christophe Coinon
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, Junia-ISEN, UMR 8520 - IEMN, 59000 Lille, France
| | - Guillaume Fleury
- Univ. Bordeaux, CNRS, Bordeaux INP, LCPO, UMR 5629, F-33600 Pessac, France
| | - Gilles Patriarche
- CNRS, Centre de Nanosciences et de Nanotechnologies (C2N), University Paris-Saclay, 91120 Palaiseau, France
| | - Tao Xu
- Sino-European School of Technology, Shanghai University, 200444 Shanghai, China
| | - Ludovic Desplanque
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, Junia-ISEN, UMR 8520 - IEMN, 59000 Lille, France
| | - Xavier Wallart
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, Junia-ISEN, UMR 8520 - IEMN, 59000 Lille, France
| | - Daniel Vanmaekelbergh
- Debye Institute for Nanomaterials Science, Utrecht University, 3508 TA Utrecht, The Netherlands
| | - Christophe Delerue
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, Junia-ISEN, UMR 8520 - IEMN, 59000 Lille, France
| | - Bruno Grandidier
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, Junia-ISEN, UMR 8520 - IEMN, 59000 Lille, France
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