1
|
Fu M, Hartmann R, Braun J, Andreev S, Pietsch T, Scheer E. Modulated critical currents of spin-transfer torque-induced resistance changes in NiCu/Cu multilayered nanowires. Beilstein J Nanotechnol 2024; 15:360-366. [PMID: 38590428 PMCID: PMC10999983 DOI: 10.3762/bjnano.15.32] [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] [Received: 01/09/2024] [Accepted: 03/14/2024] [Indexed: 04/10/2024]
Abstract
We present a novel method combining anodic aluminum oxide template synthesis and nanolithography to selectively deposit vertically patterned magnetic nanowires on a Si substrate. With this approach we fabricated three-dimensional nanowire-based spin valve devices without the need of complex etching processes or additional spacer coating. Through this method, we successfully obtained NiCu/Cu multilayered nanowire arrays with a controlled sequence along the long axis of the nanowires. Both magnetic switching and excitation phenomena driven by spin-polarized currents were clearly demonstrated in our NiCu/Cu multilayered nanowires. Moreover, the critical currents for switching and excitation were observed to be modulated in an oscillatory manner by the magnetic field in the nanowire-based devices. We present a toy model to qualitatively explain these observations.
Collapse
Affiliation(s)
- Mengqi Fu
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| | - Roman Hartmann
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| | - Julian Braun
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| | - Sergej Andreev
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| | - Torsten Pietsch
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| | - Elke Scheer
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| |
Collapse
|
2
|
Tan M, Sun F, Zhao X, Zhao Z, Zhang S, Xu X, Adijiang A, Zhang W, Wang H, Wang C, Li Z, Scheer E, Xiang D. Conductance Evolution of Photoisomeric Single-Molecule Junctions under Ultraviolet Irradiation and Mechanical Stretching. J Am Chem Soc 2024; 146:6856-6865. [PMID: 38413090 DOI: 10.1021/jacs.3c13752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/29/2024]
Abstract
A comprehensive understanding of carrier transport in photoisomeric molecular junctions is crucial for the rational design and delicate fabrication of single-molecule functional devices. It has been widely recognized that the conductance of azobenzene (a class of photoisomeric molecules) based molecular junctions is mainly determined by photoinduced conformational changes. In this study, it is demonstrated that the most probable conductance of amine-anchored azobenzene-based molecular junctions increases continuously upon UV irradiation. In contrast, the conductance of pyridyl-anchored molecular junctions with an identical azobenzene core exhibits a contrasting trend, highlighting the pivotal role that anchoring groups play, potentially overriding (even reversing) the effects of photoinduced conformational changes. It is further demonstrated that the molecule with cis-conformation cannot be fully mechanically stretched into the trans-conformation, clarifying that it is a great challenge to realize a reversible molecular switch by purely mechanical operation. Additionally, it is revealed that the coupling strength of pyridyl-anchored molecules is dramatically weakened when the UV irradiation time is prolonged, whereas it is not observed for amine-anchored molecules. The mechanisms for these observations are elucidated with the assistance of density functional theory calculations and UV-Vis spectra combined with flicker noise measurements which confirm the photoinduced conformational changes, providing insight into understanding the charge transport in photoisomeric molecular junctions and offering a routine for logical designing synchro opto-mechanical molecular switches.
Collapse
Affiliation(s)
- Min Tan
- Institute of Modern Optics and Center of Single-Molecule Science, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin 300350, China
| | - Feng Sun
- Key Laboratory of Medical Physics and Image Processing of Shandong Province, School of Physics and Electronics, Shandong Normal University, Jinan, Shandong 250358, China
| | - Xueyan Zhao
- Institute of Modern Optics and Center of Single-Molecule Science, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin 300350, China
| | - Zhibin Zhao
- Institute of Modern Optics and Center of Single-Molecule Science, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin 300350, China
| | - Surong Zhang
- Institute of Modern Optics and Center of Single-Molecule Science, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin 300350, China
| | - Xiaona Xu
- Institute of Modern Optics and Center of Single-Molecule Science, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin 300350, China
| | - Adila Adijiang
- Institute of Modern Optics and Center of Single-Molecule Science, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin 300350, China
| | - Wei Zhang
- Institute of Modern Optics and Center of Single-Molecule Science, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin 300350, China
| | - Haoyu Wang
- Institute of Modern Optics and Center of Single-Molecule Science, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin 300350, China
| | - Chuankui Wang
- Key Laboratory of Medical Physics and Image Processing of Shandong Province, School of Physics and Electronics, Shandong Normal University, Jinan, Shandong 250358, China
| | - Zongliang Li
- Key Laboratory of Medical Physics and Image Processing of Shandong Province, School of Physics and Electronics, Shandong Normal University, Jinan, Shandong 250358, China
| | - Elke Scheer
- Department of Physics, University of Konstanz, Konstanz 78457, Germany
| | - Dong Xiang
- Institute of Modern Optics and Center of Single-Molecule Science, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin 300350, China
| |
Collapse
|
3
|
Sobral Rey L, Ohnmacht DC, Winkelmann CB, Siewert J, Belzig W, Scheer E. Interplay of Andreev Reflection and Coulomb Blockade in Hybrid Superconducting Single-Electron Transistors. Phys Rev Lett 2024; 132:057001. [PMID: 38364128 DOI: 10.1103/physrevlett.132.057001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Revised: 08/29/2023] [Accepted: 12/22/2023] [Indexed: 02/18/2024]
Abstract
We study the interplay between Coulomb blockade and superconductivity in a tunable superconductor-superconductor-normal-metal single-electron transistor. The device is realized by connecting the superconducting island via an oxide barrier to the normal-metal lead and with a break junction to the superconducting lead. The latter enables Cooper pair transport and (multiple) Andreev reflection. We show that these processes are relevant also far above the superconducting gap and that signatures of Coulomb blockade may reoccur at high bias while they are absent for small bias in the strong-coupling regime. Our experimental findings agree with simulations using a rate equation approach in combination with the full counting statistics of multiple Andreev reflection.
Collapse
Affiliation(s)
- Laura Sobral Rey
- Physics Department, University of Konstanz, 78457 Konstanz, Germany
| | | | - Clemens B Winkelmann
- Université Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, 38000 Grenoble, France
| | - Jens Siewert
- University of the Basque Country UPV/EHU and EHU Quantum Center, 48080 Bilbao, Spain
- Ikerbasque, Basque Foundation for Science, 48009 Bilbao, Spain
| | - Wolfgang Belzig
- Physics Department, University of Konstanz, 78457 Konstanz, Germany
| | - Elke Scheer
- Physics Department, University of Konstanz, 78457 Konstanz, Germany
| |
Collapse
|
4
|
Snegir S, Dappe YJ, Sysoiev D, Huhn T, Scheer E. Nonuniform STM Contrast of Self-Assembled Tri- n-octyl-triazatriangulenium Tetrafluoroborate on HOPG. ACS Omega 2023; 8:38766-38772. [PMID: 37867726 PMCID: PMC10586247 DOI: 10.1021/acsomega.3c06454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Accepted: 09/21/2023] [Indexed: 10/24/2023]
Abstract
We have assembled 4,8,12-tri-n-octyl-4,8,12-triazatrianguleniumtetrafluoroborate (TATA-BF4) on highly oriented pyrolytic graphite (HOPG) and have studied the structure and tunneling properties of this self-assembled monolayer (SAM) using scanning tunneling microscopy (STM) under ambient conditions. We show that the triazatriangulenium cations TATA+ form hexagonally packed structures driven by the interaction between the aromatic core and the HOPG lattice, as evidenced by density functional theory (DFT) modeling. According to the DFT results, the three alkyl chains of the platform tend to follow the main crystallographic directions of HOPG, leading to a different STM appearance. The STM contrast of the SAM shows that the monolayer is formed by two types of species, namely, TATA+ with BF4- counterions on top and without them. The cationic TATA+ platform gives rise to a seemingly higher appearance than neutral TATA-BF4, in contrast to observations made on metallic substrates. The variation of the STM tunneling parameters does not change the relative difference of contrast, revealing the stability of both species on HOPG. DFT calculations show that TATA-BF4 on HOPG has sufficient binding energy to resist dissociation into TATA+ and BF4-, which might occur under the action of the electric field in the tunneling gap during STM scanning.
Collapse
Affiliation(s)
- Sergii Snegir
- Department
of Physics, University of Konstanz, Universitätsstraße 10, Konstanz 78464, Germany
| | - Yannick J. Dappe
- SPEC,
CEA, CNRS, Université Paris-Saclay, CEA Saclay, Gif-sur-Yvette Cédex 91191, France
| | - Dmytro Sysoiev
- Department
of Chemistry, University of Konstanz, Universitätsstraße 10, Konstanz 78464, Germany
| | - Thomas Huhn
- Department
of Chemistry, University of Konstanz, Universitätsstraße 10, Konstanz 78464, Germany
| | - Elke Scheer
- Department
of Physics, University of Konstanz, Universitätsstraße 10, Konstanz 78464, Germany
| |
Collapse
|
5
|
Lokamani M, Kilibarda F, Günther F, Kelling J, Strobel A, Zahn P, Juckeland G, Gothelf KV, Scheer E, Gemming S, Erbe A. Stretch Evolution of Electronic Coupling of the Thiophenyl Anchoring Group with Gold in Mechanically Controllable Break Junctions. J Phys Chem Lett 2023:5709-5717. [PMID: 37318265 DOI: 10.1021/acs.jpclett.3c00370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The current-voltage characteristics of a single-molecule junction are determined by the electronic coupling Γ between the electronic states of the electrodes and the dominant transport channel(s) of the molecule. Γ is profoundly affected by the choice of the anchoring groups and their binding positions on the tip facets and the tip-tip separation. In this work, mechanically controllable break junction experiments on the N,N'-bis(5-ethynylbenzenethiol-salicylidene)ethylenediamine are presented, in particular, the stretch evolution of Γ with increasing tip-tip separation. The stretch evolution of Γ is characterized by recurring local maxima and can be related to the deformation of the molecule and sliding of the anchoring groups above the tip facets and along the tip edges. A dynamic simulation approach is implemented to model the stretch evolution of Γ, which captures the experimentally observed features remarkably well and establishes a link to the microscopic structure of the single-molecule junction.
Collapse
Affiliation(s)
- Mani Lokamani
- Department of Information Services and Computing, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Bautzner Landstraße 400, 01328 Dresden, Germany
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Bautzner Landstraße 400, 01328 Dresden, Germany
| | - Filip Kilibarda
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Bautzner Landstraße 400, 01328 Dresden, Germany
| | - Florian Günther
- Instituto de Física de São Carlos, Universidade de São Paulo, USP Av. Trabalhador saocarlense, 400, 13560-970, São Carlos, São Paulo, Brazil
| | - Jeffrey Kelling
- Department of Information Services and Computing, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Bautzner Landstraße 400, 01328 Dresden, Germany
- Institute of Physics, Technische Universität Chemnitz, 09107 Chemnitz, Germany
| | - Alexander Strobel
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Bautzner Landstraße 400, 01328 Dresden, Germany
| | - Peter Zahn
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Bautzner Landstraße 400, 01328 Dresden, Germany
| | - Guido Juckeland
- Department of Information Services and Computing, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Bautzner Landstraße 400, 01328 Dresden, Germany
| | - Kurt V Gothelf
- Department of Chemistry and Interdisciplinary Nanoscience Center, Centre for DNA Nanotechnology, iNANO, Gustav Wieds Vej 14, Aarhus C, 8000 Denmark
| | - Elke Scheer
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
| | - Sibylle Gemming
- Institute of Physics, Technische Universität Chemnitz, 09107 Chemnitz, Germany
| | - Artur Erbe
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Bautzner Landstraße 400, 01328 Dresden, Germany
| |
Collapse
|
6
|
Hartmann R, Högen M, Lignon D, Tan AKC, Amado M, El-Khatib S, Egilmez M, Das B, Leighton C, Atatüre M, Scheer E, Di Bernardo A. Intrinsic giant magnetoresistance due to exchange-bias-type effects at the surface of single-crystalline NiS 2 nanoflakes. Nanoscale 2023. [PMID: 37184489 DOI: 10.1039/d3nr00467h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
The coexistence of different properties in the same material often results in exciting physical effects. At low temperatures, the pyrite transition-metal disulphide NiS2 hosts both antiferromagnetic and weak ferromagnetic orders, along with surface metallicity dominating its electronic transport. The interplay between such a complex magnetic structure and surface-dominated conduction in NiS2, however, is still not understood. A possible reason for this limited understanding is that NiS2 has been available primarily in bulk single-crystal form, which makes it difficult to perform studies combining magnetometry and transport measurements with high spatial resolution. Here, NiS2 nanoflakes are produced via mechanical cleaving and exfoliation of NiS2 single crystals and their properties are studied on a local (micron-size) scale. Strongly field-asymmetric magnetotransport features are found at low temperatures, which resemble those of more complex magnetic thin film heterostructures. Using nitrogen vacancy magnetometry, these magnetotransport features are related to exchange-bias-type effects between ferromagnetic and antiferromagnetic regions forming near step edges at the nanoflake surface. Nanoflakes with bigger steps exhibit giant magnetoresistance, which suggests a strong influence of magnetic spin textures at the NiS2 surface on its electronic transport. These findings pave the way for the application of NiS2 nanoflakes in van der Waals heterostructures for low-temperature spintronics and superconducting spintronics.
Collapse
Affiliation(s)
- Roman Hartmann
- Department of Physics, University of Konstanz, Konstanz 78457, Germany.
| | - Michael Högen
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
| | - Daphné Lignon
- Department of Physics, University of Konstanz, Konstanz 78457, Germany.
| | - Anthony K C Tan
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
| | - Mario Amado
- Nanotechnology Group, University of Salamanca, Salamanca 37008, Spain
| | - Sami El-Khatib
- Department of Physics, American University of Sharjah, Sharjah 26666, United Arab Emirates
| | - Mehmet Egilmez
- Department of Physics, American University of Sharjah, Sharjah 26666, United Arab Emirates
| | - Bhaskar Das
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
| | - Chris Leighton
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
| | - Mete Atatüre
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
| | - Elke Scheer
- Department of Physics, University of Konstanz, Konstanz 78457, Germany.
| | - Angelo Di Bernardo
- Department of Physics, University of Konstanz, Konstanz 78457, Germany.
- Dipartimento di Fisica "E. R. Caianiello", Università degli Studi di Salerno, 84084 Fisciano, SA, Italy
| |
Collapse
|
7
|
Zhao X, Zhang X, Yin K, Zhang S, Zhao Z, Tan M, Xu X, Zhao Z, Wang M, Xu B, Lee T, Scheer E, Xiang D. In Situ Adjustable Nanogaps and In-Plane Break Junctions. Small Methods 2023; 7:e2201427. [PMID: 36732898 DOI: 10.1002/smtd.202201427] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 12/27/2022] [Indexed: 06/18/2023]
Abstract
The ability to precisely regulate the size of a nanogap is essential for establishing high-yield molecular junctions, and it is crucial for the control of optical signals in extreme optics. Although remarkable strategies for the fabrication of nanogaps are proposed, wafer-compatible nanogaps with freely adjustable gap sizes are not yet available. Herein, two approaches for constructing in situ adjustable metal gaps are proposed which allow Ångstrom modulation resolution by employing either a lateral expandable piezoelectric sheet or a stretchable membrane. These in situ adjustable nanogaps are further developed into in-plane molecular break junctions, in which the gaps can be repeatedly closed and opened thousands of times with self-assembled molecules. The conductance of the single 1,4-benzenediamine (BDA) and the BDA molecular dimer is successfully determined using the proposed strategy. The measured conductance agreeing well with the data by employing another well-established scanning tunneling microscopy break junction technique provides insight into the formation of molecule dimer via hydrogen bond at single molecule level. The wafer-compatible nanogaps and in-plane dynamical break-junctions provide a potential approach to fabricate highly compacted devices using a single molecule as a building block and supply a promising in-plane technique to address the dynamical properties of single molecules.
Collapse
Affiliation(s)
- Xueyan Zhao
- Institute of Modern Optics and Center of Single-Molecule Science, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Xubin Zhang
- Institute of Modern Optics and Center of Single-Molecule Science, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Kaikai Yin
- Institute of Modern Optics and Center of Single-Molecule Science, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Surong Zhang
- Institute of Modern Optics and Center of Single-Molecule Science, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Zhikai Zhao
- Institute of Modern Optics and Center of Single-Molecule Science, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Min Tan
- Institute of Modern Optics and Center of Single-Molecule Science, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Xiaona Xu
- Institute of Modern Optics and Center of Single-Molecule Science, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Zhibin Zhao
- Institute of Modern Optics and Center of Single-Molecule Science, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Maoning Wang
- Institute of Modern Optics and Center of Single-Molecule Science, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| | - Bingqian Xu
- College of Engineering, University of Georgia, Athens, GA, 30602, USA
| | - Takhee Lee
- Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul, 08826, Korea
| | - Elke Scheer
- Department of Physics, University of Konstanz, 78457, Konstanz, Germany
| | - Dong Xiang
- Institute of Modern Optics and Center of Single-Molecule Science, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin, 300350, China
| |
Collapse
|
8
|
Mitra G, Low JZ, Wei S, Francisco KR, Deffner M, Herrmann C, Campos LM, Scheer E. Interplay between Magnetoresistance and Kondo Resonance in Radical Single-Molecule Junctions. Nano Lett 2022; 22:5773-5779. [PMID: 35849010 DOI: 10.1021/acs.nanolett.2c01199] [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
We report transport measurements on tunable single-molecule junctions of the organic perchlorotrityl radical molecule, contacted with gold electrodes at low temperature. The current-voltage characteristics of a subset of junctions shows zero-bias anomalies due to the Kondo effect and in addition elevated magnetoresistance (MR). Junctions without Kondo resonance reveal a much stronger MR. Furthermore, we show that the amplitude of the MR can be tuned by mechanically stretching the junction. On the basis of these findings, we attribute the high MR to an interference effect involving spin-dependent scattering at the metal-molecule interface and assign the Kondo effect to the unpaired spin located in the center of the molecule in asymmetric junctions.
Collapse
Affiliation(s)
- Gautam Mitra
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
| | - Jonathan Z Low
- Department of Chemistry, Columbia University, New York, New York 10027, United States
- Singapore Institute of Manufacturing Technology, 2 Fusionopolis Way, Singapore 138634, Singapore
| | - Sujun Wei
- Department of Chemistry, Queensborough Community College of the City University of New York, Bayside, New York 11364, United States
| | - Karol R Francisco
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Michael Deffner
- Institut für Anorganische und Angewandte Chemie, The Hamburg Centre for Ultrafast Imaging, 22761 Hamburg, Germany
| | - Carmen Herrmann
- Institut für Anorganische und Angewandte Chemie, The Hamburg Centre for Ultrafast Imaging, 22761 Hamburg, Germany
| | - Luis M Campos
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Elke Scheer
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
| |
Collapse
|
9
|
Mitra G, Delmas V, Al Sabea H, Norel L, Galangau O, Rigaut S, Cornil J, Costuas K, Scheer E. Electronic transport through single-molecule oligophenyl-diethynyl junctions with direct gold-carbon bonds formed at low temperature. Nanoscale Adv 2022; 4:457-466. [PMID: 36132702 PMCID: PMC9419624 DOI: 10.1039/d1na00650a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 11/27/2021] [Indexed: 06/16/2023]
Abstract
We report on the first systematic transport study of alkynyl-ended oligophenyl-diethynyl (OPA) single-molecule junctions with direct Au-C anchoring scheme at low temperature using the mechanically controlled break junction technique. Through quantitative statistical analysis of opening traces, conductance histograms and density functional theory studies, we identified different types of junctions, classified by their conductance and stretching behavior, for OPA molecules between Au electrodes with two to four phenyl rings. We performed inelastic electron tunneling spectroscopy and observed the excitation of Au-C vibrational modes confirming the existence of Au-C bonds at low temperature and compared the stability of molecule junctions upon mechanical stretching. Our findings reveal the huge potential for future functional molecule transport studies at low temperature using alkynyl endgroups.
Collapse
Affiliation(s)
- Gautam Mitra
- University of Konstanz, Department of Physics 78 457 Konstanz Germany
| | - Vincent Delmas
- Univ. Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes), UMR 6226 F-35 000 Rennes France
| | - Hassan Al Sabea
- Univ. Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes), UMR 6226 F-35 000 Rennes France
| | - Lucie Norel
- Univ. Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes), UMR 6226 F-35 000 Rennes France
| | - Olivier Galangau
- Univ. Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes), UMR 6226 F-35 000 Rennes France
| | - Stéphane Rigaut
- Univ. Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes), UMR 6226 F-35 000 Rennes France
| | - Jérôme Cornil
- University of Mons, Laboratory for Chemistry of Novel Materials, Department of Chemistry Place du Parc 20 B-7000 Mons Belgium
| | - Karine Costuas
- Univ. Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes), UMR 6226 F-35 000 Rennes France
| | - Elke Scheer
- University of Konstanz, Department of Physics 78 457 Konstanz Germany
| |
Collapse
|
10
|
Yang F, Fu M, Bosnjak B, Blick RH, Jiang Y, Scheer E. Mechanically Modulated Sideband and Squeezing Effects of Membrane Resonators. Phys Rev Lett 2021; 127:184301. [PMID: 34767395 DOI: 10.1103/physrevlett.127.184301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 09/02/2021] [Accepted: 09/27/2021] [Indexed: 06/13/2023]
Abstract
We investigate the sideband spectra of a driven nonlinear mode with its eigenfrequency being modulated at a low frequency (<1 kHz). This additional parametric modulation leads to prominent antiresonance line shapes in the sideband spectra, which can be controlled through the vibration state of the driven mode. We also establish a direct connection between the antiresonance frequency and the squeezing of thermal fluctuation in the system. Our Letter not only provides a simple and robust method for squeezing characterization, but also opens a new possibility toward sideband applications.
Collapse
Affiliation(s)
- Fan Yang
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| | - Mengqi Fu
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| | - Bojan Bosnjak
- Center for Hybrid Nanostructures, Universität Hamburg, 22761 Hamburg, Germany
| | - Robert H Blick
- Center for Hybrid Nanostructures, Universität Hamburg, 22761 Hamburg, Germany
| | - Yuxuan Jiang
- School of Physics and Optoelectronics Engineering, Anhui University, 230601 Hefei, China
| | - Elke Scheer
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| |
Collapse
|
11
|
Fittipaldi R, Hartmann R, Mercaldo MT, Komori S, Bjørlig A, Kyung W, Yasui Y, Miyoshi T, Olde Olthof LAB, Palomares Garcia CM, Granata V, Keren I, Higemoto W, Suter A, Prokscha T, Romano A, Noce C, Kim C, Maeno Y, Scheer E, Kalisky B, Robinson JWA, Cuoco M, Salman Z, Vecchione A, Di Bernardo A. Unveiling unconventional magnetism at the surface of Sr 2RuO 4. Nat Commun 2021; 12:5792. [PMID: 34608149 PMCID: PMC8490454 DOI: 10.1038/s41467-021-26020-5] [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] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 09/14/2021] [Indexed: 11/09/2022] Open
Abstract
Materials with strongly correlated electrons often exhibit interesting physical properties. An example of these materials is the layered oxide perovskite Sr2RuO4, which has been intensively investigated due to its unusual properties. Whilst the debate on the symmetry of the superconducting state in Sr2RuO4 is still ongoing, a deeper understanding of the Sr2RuO4 normal state appears crucial as this is the background in which electron pairing occurs. Here, by using low-energy muon spin spectroscopy we discover the existence of surface magnetism in Sr2RuO4 in its normal state. We detect static weak dipolar fields yet manifesting at an onset temperature higher than 50 K. We ascribe this unconventional magnetism to orbital loop currents forming at the reconstructed Sr2RuO4 surface. Our observations set a reference for the discovery of the same magnetic phase in other materials and unveil an electronic ordering mechanism that can influence electron pairing with broken time reversal symmetry.
Collapse
Affiliation(s)
- R Fittipaldi
- CNR-SPIN, c/o University of Salerno, I-84084, Fisciano, Salerno, Italy.,Dipartimento di Fisica "E.R. Caianiello", University of Salerno, I-84084, Fisciano, Salerno, Italy
| | - R Hartmann
- Department of Physics, University of Konstanz, 78457, Konstanz, Germany
| | - M T Mercaldo
- Dipartimento di Fisica "E.R. Caianiello", University of Salerno, I-84084, Fisciano, Salerno, Italy
| | - S Komori
- Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB3 0FS, UK.,Department of Physics, Nagoya University, Nagoya, 464-8602, Japan
| | - A Bjørlig
- Department of Physics, Bar Ilan University, Ramat Gan, 5920002, Israel
| | - W Kyung
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Korea
| | - Y Yasui
- Department of Physics, Kyoto University, Kyoto, 606-8502, Japan.,RIKEN, Centre for Emergent Matter Science, Saitama, 351-0198, Japan
| | - T Miyoshi
- Department of Physics, Kyoto University, Kyoto, 606-8502, Japan
| | - L A B Olde Olthof
- Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB3 0FS, UK
| | - C M Palomares Garcia
- Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB3 0FS, UK
| | - V Granata
- Dipartimento di Fisica "E.R. Caianiello", University of Salerno, I-84084, Fisciano, Salerno, Italy
| | - I Keren
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232, Villigen, PSI, Switzerland.,The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel
| | - W Higemoto
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki, 319-1195, Japan
| | - A Suter
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232, Villigen, PSI, Switzerland
| | - T Prokscha
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232, Villigen, PSI, Switzerland
| | - A Romano
- CNR-SPIN, c/o University of Salerno, I-84084, Fisciano, Salerno, Italy.,Dipartimento di Fisica "E.R. Caianiello", University of Salerno, I-84084, Fisciano, Salerno, Italy
| | - C Noce
- CNR-SPIN, c/o University of Salerno, I-84084, Fisciano, Salerno, Italy.,Dipartimento di Fisica "E.R. Caianiello", University of Salerno, I-84084, Fisciano, Salerno, Italy
| | - C Kim
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Korea
| | - Y Maeno
- Department of Physics, Kyoto University, Kyoto, 606-8502, Japan
| | - E Scheer
- Department of Physics, University of Konstanz, 78457, Konstanz, Germany
| | - B Kalisky
- Department of Physics, Bar Ilan University, Ramat Gan, 5920002, Israel
| | - J W A Robinson
- Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, CB3 0FS, UK
| | - M Cuoco
- CNR-SPIN, c/o University of Salerno, I-84084, Fisciano, Salerno, Italy. .,Dipartimento di Fisica "E.R. Caianiello", University of Salerno, I-84084, Fisciano, Salerno, Italy.
| | - Z Salman
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232, Villigen, PSI, Switzerland.
| | - A Vecchione
- CNR-SPIN, c/o University of Salerno, I-84084, Fisciano, Salerno, Italy.,Dipartimento di Fisica "E.R. Caianiello", University of Salerno, I-84084, Fisciano, Salerno, Italy
| | - A Di Bernardo
- Department of Physics, University of Konstanz, 78457, Konstanz, Germany.
| |
Collapse
|
12
|
Yang F, Hellbach F, Rochau F, Belzig W, Weig EM, Rastelli G, Scheer E. Persistent Response in an Ultrastrongly Driven Mechanical Membrane Resonator. Phys Rev Lett 2021; 127:014304. [PMID: 34270281 DOI: 10.1103/physrevlett.127.014304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 06/01/2021] [Accepted: 06/04/2021] [Indexed: 06/13/2023]
Abstract
We study experimentally and theoretically the phenomenon of "persistent response" in ultrastrongly driven membrane resonators. The term persistent response denotes the development of a vibrating state with nearly constant amplitude over an extreme wide frequency range. We reveal the underlying mechanism by directly imaging the vibrational state using advanced optical interferometry. We argue that this state is related to the nonlinear interaction between higher-order flexural modes and higher-order overtones of the driven mode. Finally, we propose a stability diagram for the different vibrational states that the membrane can adopt.
Collapse
Affiliation(s)
- Fan Yang
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| | | | - Felix Rochau
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| | - Wolfgang Belzig
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| | - Eva M Weig
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
- Fakultät für Elektrotechnik und Informationstechnik, Technische Universität München, 80333 München, Germany
| | - Gianluca Rastelli
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
- INO-CNR BEC Center and Dipartimento di Fisica, Università di Trento, 38123 Povo, Italy
| | - Elke Scheer
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| |
Collapse
|
13
|
Snegir S, Dappe YJ, Sysoiev D, Pluchery O, Huhn T, Scheer E. Where do the counterions go? Tip-induced dissociation of self-assembled triazatriangulenium-based molecules on Au(111). Phys Chem Chem Phys 2021; 23:9930-9937. [PMID: 33861285 DOI: 10.1039/d1cp00221j] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Chemical coupling of functional molecules on top of the so-called platform molecules allows the formation of functional self-assembled monolayers (SAMs). An often-used example of such a platform is triazatriangulenium (TATA), which features an extended aromatic core providing good electronic contact to the underlying metal surface. Here, we present a study of the SAM formation of a TATA platform on Au(111) employing scanning tunneling microscopy (STM) under ambient atmospheric conditions. In solution, the TATA platform is stabilized by BF4 counterions, while after deposition on a gold substrate, the localization of the BF4 counterions remains unknown. We used 1,2,4-trichlorobenzene as a solvent of TATA-BF4 to induce SAM formation on a heated (∼50 °C) Au substrate. We show by STM how to detect and distinguish TATA-BF4 from TATA platforms, which lost their BF4 counterions. Finally, we observe a change of the counterion position on the SAM during the STM scanning, which we explain by an electric-field-induced decrease of the electrostatic interaction in TATA-BF4 on the surface. We applied DFT calculations to reveal the influence of the gold lattice and the electric field of the STM tip on the stability of TATA-BF4 physisorbed on the surface.
Collapse
Affiliation(s)
- S Snegir
- Department of Physics, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany.
| | - Y J Dappe
- SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
| | - D Sysoiev
- Department of Chemistry, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
| | - O Pluchery
- Sorbonne Université, CNRS, Institut des NanoSciences de Paris (INSP), 4 place Jussieu, 75005 Paris, France
| | - T Huhn
- Department of Chemistry, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
| | - E Scheer
- Department of Physics, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany.
| |
Collapse
|
14
|
Basu TS, Diesch S, Hayakawa R, Wakayama Y, Scheer E. Single-charge transport through hybrid core-shell Au-ZnS quantum dots: a comprehensive analysis from a modified energy structure. Nanoscale 2021; 13:4978-4984. [PMID: 33634301 DOI: 10.1039/d0nr06883g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We examined the modified electronic structure and single-carrier transport of individual hybrid core-shell metal-semiconductor Au-ZnS quantum dots (QDs) using a scanning tunnelling microscope. Nearly monodisperse ultra-small QDs are achieved by a facile wet chemical route. The exact energy structures are evaluated by scanning tunnelling spectroscopy (STS) measurements at 300 mK for the individual nanoobjects starting from the main building block Au nanocrystals (NCs) to the final Au-ZnS QDs. The study divulges the evolution of the energy structure and the charge transport from the single metallic building block core to the core-shell metal-semiconductor QDs. Furthermore, we successfully determined the contributions related to the quantum-confinement-induced excitonic band structure of the ZnS nano-shell and the charging energy of the system by applying a semi-empirical approach considering a double barrier tunnel junction (DBTJ) arrangement. We detect strong conductance peaks in Au-ZnS QDs due to the overlapping of the energy structure of the Au nano-core and the discrete energy states of the semiconductor ZnS nano-shell. Our findings will help in understanding the electronic properties of metal-semiconductor QDs. The outcomes therefore have the potential to fabricate tailored metal-semiconductor QDs for single-electron devices.
Collapse
Affiliation(s)
- Tuhin Shuvra Basu
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany.
| | | | | | | | | |
Collapse
|
15
|
Delmas V, Diez-Cabanes V, van Dyck C, Scheer E, Costuas K, Cornil J. On the reliability of acquiring molecular junction parameters by Lorentzian fitting of I/ V curves. Phys Chem Chem Phys 2020; 22:26702-26706. [PMID: 33216107 DOI: 10.1039/d0cp05372d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Fitting the I/V curves of molecular junctions by simple analytical models is often done to extract relevant molecular parameters such as energy level alignment or interfacial electronic coupling to build up useful property-relationships. However, such models can suffer from severe limitations and hence provide unreliable molecular parameters. This is illustrated here by extracting key molecular parameters by fitting computed voltage-dependent transmission spectra and by comparing them to the values obtained by fitting the calculated I/V curves with a typical Lorentzian model used in the literature. Doing so, we observe a large discrepancy between the two sets of values which warns us about the risks of using simple fitting expressions. Interestingly, we demonstrate that the quality of the fit can be improved by imposing the low bias conductance and Seebeck coefficient of the junction to be recovered in the fitting procedure.
Collapse
Affiliation(s)
- Vincent Delmas
- Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes) - UMR 6226, F-35000 Rennes, France.
| | | | | | | | | | | |
Collapse
|
16
|
Abstract
We study voltage-induced conductance changes of Pb, Au, Al, and Cu atomic contacts. The experiments are performed in vacuum at low temperature using mechanically controllable break junctions. We determine switching histograms, i.e., distribution functions of switching voltages and switching currents, as a function of the conductance. We observe a clear material dependence: Au reveals the highest and almost conductance-independent switching voltage, while Al has the lowest with a pronounced dependence on the conductance. The theoretical study uses density functional theory and a generalized Langevin equation considering the pumping of particular phonon modes. We identify a runaway voltage as the threshold at which the pumping destabilizes the atomic arrangement. We find qualitative agreement between the average switching voltage and the runaway voltage regarding the material and conductance dependence and contact-to-contact variation of the average characteristic voltages, suggesting that the phonon pumping is a relevant mechanism driving the rearrangements in the experimental contacts.
Collapse
Affiliation(s)
- Markus Ring
- Physics Department, University of Konstanz, 78457 Konstanz, Germany
| | - David Weber
- Physics Department, University of Konstanz, 78457 Konstanz, Germany
| | - Patrick Haiber
- Physics Department, University of Konstanz, 78457 Konstanz, Germany
| | - Fabian Pauly
- Physics Department, University of Konstanz, 78457 Konstanz, Germany
- Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa 904-0495, Japan
| | - Peter Nielaba
- Physics Department, University of Konstanz, 78457 Konstanz, Germany
| | - Elke Scheer
- Physics Department, University of Konstanz, 78457 Konstanz, Germany
| |
Collapse
|
17
|
Lenyk B, Schöps V, Boneberg J, Kabdulov M, Huhn T, Scheer E, Offenhäusser A, Mayer D. Surface Plasmon-Enhanced Switching Kinetics of Molecular Photochromic Films on Gold Nanohole Arrays. Nano Lett 2020; 20:5243-5250. [PMID: 32520573 DOI: 10.1021/acs.nanolett.0c01569] [Citation(s) in RCA: 2] [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: 06/11/2023]
Abstract
Diarylethene molecules are discussed as possible optical switches, which can reversibly transition between completely conjugated (closed) and nonconjugated (open) forms with different electrical conductance and optical absorbance, by exposure to UV and visible light. However, in general the opening reaction exhibits much lower quantum yield than the closing process, hindering their usage in optoelectronic devices. To enhance the opening process, which is supported by visible light, we employ the plasmonic field enhancement of gold films perforated with nanoholes. We show that gold nanohole arrays reveal strong optical transmission in the visible range (∼60%) and pronounced enhancement of field intensities, resulting in around 50% faster switching kinetics of the molecular species in comparison with quartz substrates. The experimental UV-vis measurements are verified with finite-difference time-domain simulation that confirm the obtained results. Thus, we propose gold nanohole arrays as transparent and conductive plasmonic material that accelerates visible-light-triggered chemical reactions including molecular switching.
Collapse
Affiliation(s)
- Bohdan Lenyk
- Institute of Biological Information Processing (IBI-3), Forschungszentrum Jülich, 52428 Jülich, Germany
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
| | - Volker Schöps
- Institute of Biological Information Processing (IBI-3), Forschungszentrum Jülich, 52428 Jülich, Germany
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
| | - Johannes Boneberg
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
| | - Mikhail Kabdulov
- Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
| | - Thomas Huhn
- Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
| | - Elke Scheer
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
| | - Andreas Offenhäusser
- Institute of Biological Information Processing (IBI-3), Forschungszentrum Jülich, 52428 Jülich, Germany
| | - Dirk Mayer
- Institute of Biological Information Processing (IBI-3), Forschungszentrum Jülich, 52428 Jülich, Germany
| |
Collapse
|
18
|
Stetsenko M, Margitych T, Kryvyi S, Maksimenko L, Hassan A, Filonenko S, Li Β, Qu J, Scheer E, Snegir S. Gold Nanoparticle Self-Aggregation on Surface with 1,6-Hexanedithiol Functionalization. Nanomaterials (Basel) 2020; 10:E512. [PMID: 32168942 PMCID: PMC7153467 DOI: 10.3390/nano10030512] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 03/02/2020] [Accepted: 03/06/2020] [Indexed: 12/02/2022]
Abstract
Here we study the morphology and the optical properties of assemblies made of small (17 nm) gold nanoparticles (AuNPs) directly on silicon wafers coated with (3-aminopropyl)trimethoxysilane (APTES). We employed aliphatic 1,6-hexanedithiol (HDT) molecules to cross-link AuNPs during a two-stage precipitation procedure. The first immersion of the wafer in AuNP colloidal solution led mainly to the attachment of single particles with few inclusions of dimers and small aggregates. After the functionalization of precipitated NPs with HDT and after the second immersion in the colloidal solution of AuNP, we detected a sharp rise in the number of aggregates compared to single AuNPs and their dimers. The lateral size of the aggregates was about 100 nm, while some of them were larger than 1μm. We propose that the uncompensated dipole moment of the small aggregates appeared after the first precipitation and acts further as the driving force accelerating their further growth on the surface during the second precipitation. By having such inhomogeneous surface coating, the X-ray reciprocal space maps and modulation polarimetry showed well-distinguished signals from the single AuNPs and their dimers. From these observations, we concluded that the contribution from aggregated AuNPs does not hamper the detection and investigation of plasmonic effects for AuNP dimers. Meantime, using unpolarized and polarized light spectroscopy, the difference in the optical signals between the dimers, being formed because of self-aggregation and the one being cross-linked by means of HDT, was not detected.
Collapse
Affiliation(s)
- Maksym Stetsenko
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China; (M.S.); (A.H.)
- V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine, 03680 Kyiv, Ukraine; (S.K.); (L.M.)
| | - Tetiana Margitych
- Kyiv Institute for Nuclear Research, National Academy of Sciences of Ukraine, 03680 Kyiv, Ukraine;
| | - Serhii Kryvyi
- V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine, 03680 Kyiv, Ukraine; (S.K.); (L.M.)
- Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw, Poland
| | - Lidia Maksimenko
- V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine, 03680 Kyiv, Ukraine; (S.K.); (L.M.)
| | - Ali Hassan
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China; (M.S.); (A.H.)
| | - Svitlana Filonenko
- Pisarzhevski Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospect Nauky, 03028 Kiev, Ukraine;
| | - Βaikui Li
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China; (M.S.); (A.H.)
| | - Junle Qu
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China; (M.S.); (A.H.)
| | - Elke Scheer
- University of Konstanz, Department of Physics, Universitätsstraße 10, 78464 Konstanz, Germany;
| | - Sergii Snegir
- University of Konstanz, Department of Physics, Universitätsstraße 10, 78464 Konstanz, Germany;
| |
Collapse
|
19
|
Mayer D, Scheer E. Stability makes a difference. Nat Nanotechnol 2019; 14:925-926. [PMID: 31527842 DOI: 10.1038/s41565-019-0537-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Affiliation(s)
- Dirk Mayer
- Institute of Complex Systems (ICS-8), Forschungszentrum Jülich, Jülich, Germany.
| | - Elke Scheer
- Department of Physics, University of Konstanz, Konstanz, Germany.
| |
Collapse
|
20
|
Yang F, Rochau F, Huber JS, Brieussel A, Rastelli G, Weig EM, Scheer E. Spatial Modulation of Nonlinear Flexural Vibrations of Membrane Resonators. Phys Rev Lett 2019; 122:154301. [PMID: 31050522 DOI: 10.1103/physrevlett.122.154301] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 03/13/2019] [Indexed: 06/09/2023]
Abstract
We study the vibrational motion of mechanical resonators under strong drive in the strongly nonlinear regime. By imaging the vibrational state of rectangular silicon nitride membrane resonators and by analyzing the frequency response using optical interferometry, we show that, upon increasing the driving strength, the membrane adopts a peculiar deflection pattern formed by concentric rings superimposed onto the drum head shape of the fundamental mode. Such a circular symmetry cannot be described as a superposition of a small number of excited linear eigenmodes. Furthermore, different parts of the membrane vibrate at different multiples of the drive frequency, an observation that we denominate as "localization of overtones." We introduce a phenomenological model that is based on the coupling of a small number of effective nonlinear resonators, representing the different parts of the membrane, and that describes the experimental observations correctly.
Collapse
Affiliation(s)
- Fan Yang
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
| | - Felix Rochau
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
| | - Jana S Huber
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
| | | | - Gianluca Rastelli
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
| | - Eva M Weig
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
| | - Elke Scheer
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
| |
Collapse
|
21
|
Koo J, Jang Y, Martin L, Kim D, Jeong H, Kang K, Lee W, Kim J, Hwang WT, Xiang D, Scheer E, Kabdulov M, Huhn T, Pauly F, Lee T. Unidirectional Real-Time Photoswitching of Diarylethene Molecular Monolayer Junctions with Multilayer Graphene Electrodes. ACS Appl Mater Interfaces 2019; 11:11645-11653. [PMID: 30821955 DOI: 10.1021/acsami.8b19372] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We fabricate and characterize vertical molecular junctions consisting of self-assembled monolayers of diarylethene (DAE) contacted by a multilayer graphene (MLG) electrode on the top and gold on the bottom. The DAE molecular junctions show two stable electrical states, a closed state (high conductance) or an open state (low conductance), which are created upon illumination with UV or visible light, respectively. For the Au-DAE-MLG junction structure, we observe that the current levels between the two conductance states are separated by 2 orders of magnitude. However, in a real-time measurement, we observe only unidirectional switching behavior from the open to the closed state.
Collapse
Affiliation(s)
- Jeongmin Koo
- Department of Physics and Astronomy, and Institute of Applied Physics , Seoul National University , Seoul 08826 , Korea
| | - Yeonsik Jang
- Department of Physics and Astronomy, and Institute of Applied Physics , Seoul National University , Seoul 08826 , Korea
| | - León Martin
- Okinawa Institute of Science and Technology Graduate University , Onna-son, Okinawa 904-0495 , Japan
| | | | - Hyunhak Jeong
- Department of Physics and Astronomy, and Institute of Applied Physics , Seoul National University , Seoul 08826 , Korea
| | - Keehoon Kang
- Department of Physics and Astronomy, and Institute of Applied Physics , Seoul National University , Seoul 08826 , Korea
| | - Woocheol Lee
- Department of Physics and Astronomy, and Institute of Applied Physics , Seoul National University , Seoul 08826 , Korea
| | - Junwoo Kim
- Department of Physics and Astronomy, and Institute of Applied Physics , Seoul National University , Seoul 08826 , Korea
| | - Wang-Taek Hwang
- Department of Physics and Astronomy, and Institute of Applied Physics , Seoul National University , Seoul 08826 , Korea
| | - Dong Xiang
- Tianjin Key Laboratory of Optoelectronic Sensor and Sensing Network Technology, College of Electronic Information and Optical Engineering , Nankai University , 300071 Tianjin , China
| | | | | | | | - Fabian Pauly
- Okinawa Institute of Science and Technology Graduate University , Onna-son, Okinawa 904-0495 , Japan
| | - Takhee Lee
- Department of Physics and Astronomy, and Institute of Applied Physics , Seoul National University , Seoul 08826 , Korea
| |
Collapse
|
22
|
Basu TS, Diesch S, Obergfell M, Demsar J, Scheer E. Energy scales and dynamics of electronic excitations in functionalized gold nanoparticles measured at the single particle level. Phys Chem Chem Phys 2019; 21:13446-13452. [DOI: 10.1039/c9cp02378j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The knowledge of the electronic structure in nanoparticles and their dynamics is a prerequisite to develop miniaturized single electron devices based on nanoparticles.
Collapse
Affiliation(s)
| | - Simon Diesch
- Department of Physics
- University of Konstanz
- 78457 Konstanz
- Germany
| | - Manuel Obergfell
- Institute of Physics
- Johannes Gutenberg-University Mainz
- 55128 Mainz
- Germany
| | - Jure Demsar
- Institute of Physics
- Johannes Gutenberg-University Mainz
- 55128 Mainz
- Germany
| | - Elke Scheer
- Department of Physics
- University of Konstanz
- 78457 Konstanz
- Germany
| |
Collapse
|
23
|
Diesch S, Machon P, Wolz M, Sürgers C, Beckmann D, Belzig W, Scheer E. Creation of equal-spin triplet superconductivity at the Al/EuS interface. Nat Commun 2018; 9:5248. [PMID: 30531894 PMCID: PMC6286363 DOI: 10.1038/s41467-018-07597-w] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Accepted: 11/12/2018] [Indexed: 11/09/2022] Open
Abstract
In conventional superconductors, electrons of opposite spins are bound into Cooper pairs. However, when the superconductor is in contact with a non-uniformly ordered ferromagnet, an exotic type of superconductivity can appear at the interface, with electrons bound into three possible spin-triplet states. Triplet pairs with equal spin play a vital role in low-dissipation spintronics. Despite the observation of supercurrents through ferromagnets, spectroscopic evidence for the existence of equal-spin triplet pairs is still missing. Here we show a theoretical model that reveals a characteristic gap structure in the quasiparticle density of states which provides a unique signature for the presence of equal-spin triplet pairs. By scanning tunnelling spectroscopy we measure the local density of states to reveal the spin configuration of triplet pairs. We demonstrate that the Al/EuS interface causes strong and tunable spin-mixing by virtue of its spin-dependent transmission.
Collapse
Affiliation(s)
- S Diesch
- Department of Physics, University of Konstanz, Universitätsstraße 10, D-78457, Konstanz, Germany
| | - P Machon
- Department of Physics, University of Konstanz, Universitätsstraße 10, D-78457, Konstanz, Germany
| | - M Wolz
- Department of Physics, University of Konstanz, Universitätsstraße 10, D-78457, Konstanz, Germany
| | - C Sürgers
- Physikalisches Institut, Karlsruhe Institute of Technology (KIT), Wolfgang Gaede Straße 1, D-76131, Karlsruhe, Germany
| | - D Beckmann
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, D-76344, Eggenstein-Leopoldshafen, Germany
| | - W Belzig
- Department of Physics, University of Konstanz, Universitätsstraße 10, D-78457, Konstanz, Germany.
| | - E Scheer
- Department of Physics, University of Konstanz, Universitätsstraße 10, D-78457, Konstanz, Germany.
| |
Collapse
|
24
|
|
25
|
Abstract
We have fabricated organically capped stable luminescent silicon nanocrystals with narrow size distribution by a novel, high yield and easy to implement technique. We demonstrate transport measurements of individual silicon nanocrystals by scanning tunnelling microscopy at a low temperature in a double-barrier tunnel junction arrangement in which we observed pronounced single electron tunnelling effects. The tunnelling spectroscopy of these nanocrystals with different diameters reveals quantum confinement induced bandgap modifications. Furthermore, from the features in the tunnelling spectra, we differentiate several energy contributions arising from electronic interactions inside the nanocrystal. By applying a magnetic field, we have detected a variation in the differential conductance profile that we attribute to arising from higher order tunnelling processes. We have also systematically simulated our experimental data with the Orthodox theory, and the results show good agreement with the experiment. The study establishes a correlation between the nanocrystal size and quantum confinement induced band-structure modifications which will pave the way to devise tailored nanocrystals.
Collapse
Affiliation(s)
- Tuhin Shuvra Basu
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany.
| | | | | |
Collapse
|
26
|
Möller TB, Ganser A, Kratt M, Dickreuter S, Waitz R, Scheer E, Boneberg J, Leiderer P. Fast quantitative optical detection of heat dissipation by surface plasmon polaritons. Nanoscale 2018; 10:11894-11900. [PMID: 29897094 DOI: 10.1039/c8nr02489h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Heat management at the nanoscale is an issue of increasing importance. In optoelectronic devices the transport and decay of plasmons contribute to the dissipation of heat. By comparison of experimental data and simulations we demonstrate that it is possible to gain quantitative information about excitation, propagation and decay of surface plasmon polaritons (SPPs) in a thin gold stripe supported by a silicon membrane. The temperature-dependent optical transmissivity of the membrane is used to determine the temperature distribution around the metal stripe with high spatial and temporal resolution. This method is complementary to techniques where the propagation of SPPs is monitored optically, and provides additional information which is not readily accessible by other means. In particular, we demonstrate that the thermal conductivity of the membrane can also be derived from our analysis. The results presented here show the high potential of this tool for heat management studies in nanoscale devices.
Collapse
Affiliation(s)
- Thomas B Möller
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany.
| | | | | | | | | | | | | | | |
Collapse
|
27
|
Abstract
In this work, we report a one-step method for the preparation of graphene-wrapped zinc oxide (ZnO) nanoparticle (NP) (ZnO@G) hybrids. These hybrids are characterized by transmission electron microscopy, X-ray diffraction, Raman spectroscopy, optical absorption measurements, photoluminescence (PL) emission spectroscopy, and M-H hysteresis measurements. All results reveal that the ZnO NPs are entirely covered with graphene sheets. In the PL spectra, the quenching of the band gap emission and the enhanced green emission serve as evidence of the electron transfer from the ZnO NPs to the graphene layer. The increase of the room-temperature magnetization of the hybrid, compared to pure ZnO NPs, is due to the increasing defect concentration. We suggest a band diagram model that accounts for these observations. We present the simple wet-chemical synthesis procedure to open a new way for the synthesis of NP-graphene hybrid systems having magnetic properties giving the large manifold potential application.
Collapse
Affiliation(s)
- Arpita Jana
- Department of Physics, University of Konstanz , 78457 Konstanz, Germany
| | - Elke Scheer
- Department of Physics, University of Konstanz , 78457 Konstanz, Germany
| |
Collapse
|
28
|
Abstract
We have fabricated mechanically controlled break junction samples made of lead (Pb) by means of state-of-the-art nanofabrication methods: electron beam lithography and physical vapour deposition. The electrical and magnetic properties were characterized in a [Formula: see text] cryostat and showed a hard superconducting gap. Temperature and magnetic field dependence of tunnel contacts were compared and quantitatively described by including either thermal broadening of the density of states or pair breaking in the framework of a Skalski model, respectively. We show point contact spectra of few-atom contacts and present tunneling spectra exhibiting a superconducting double-gap structure.
Collapse
Affiliation(s)
- David Weber
- Universitätsstr. 10, D-78464 Konstanz, Germany
| | | |
Collapse
|
29
|
Schöps V, Lenyk B, Huhn T, Boneberg J, Scheer E, Offenhäusser A, Mayer D. Facile, non-destructive characterization of 2d photonic crystals using UV-vis-spectroscopy. Phys Chem Chem Phys 2018; 20:4340-4346. [DOI: 10.1039/c7cp07498k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The quality of particle monolayers and size evolution of their particles during dry etching can be monitored by radiative losses of photonic modes into dielectric substrates.
Collapse
Affiliation(s)
- V. Schöps
- Department of Physics
- University of Konstanz
- 78457 Konstanz
- Germany
- Institute of Complex Systems (ICS-8)
| | - B. Lenyk
- Department of Physics
- University of Konstanz
- 78457 Konstanz
- Germany
- Institute of Complex Systems (ICS-8)
| | - T. Huhn
- Department of Chemistry
- University of Konstanz
- 78457 Konstanz
- Germany
| | - J. Boneberg
- Department of Physics
- University of Konstanz
- 78457 Konstanz
- Germany
| | - E. Scheer
- Department of Physics
- University of Konstanz
- 78457 Konstanz
- Germany
| | - A. Offenhäusser
- Institute of Complex Systems (ICS-8)
- Bioelectronics
- Forschungszentrum Jülich
- 52428 Jülich
- Germany
| | - D. Mayer
- Institute of Complex Systems (ICS-8)
- Bioelectronics
- Forschungszentrum Jülich
- 52428 Jülich
- Germany
| |
Collapse
|
30
|
Kim Y, Bahoosh SG, Sysoiev D, Huhn T, Pauly F, Scheer E. Inelastic electron tunneling spectroscopy of difurylethene-based photochromic single-molecule junctions. Beilstein J Nanotechnol 2017; 8:2606-2614. [PMID: 29259875 PMCID: PMC5727803 DOI: 10.3762/bjnano.8.261] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 11/17/2017] [Indexed: 06/07/2023]
Abstract
Diarylethene-derived molecules alter their electronic structure upon transformation between the open and closed forms of the diarylethene core, when exposed to ultraviolet (UV) or visible light. This transformation results in a significant variation of electrical conductance and vibrational properties of corresponding molecular junctions. We report here a combined experimental and theoretical analysis of charge transport through diarylethene-derived single-molecule devices, which are created using the mechanically controlled break-junction technique. Inelastic electron tunneling (IET) spectroscopy measurements performed at 4.2 K are compared with first-principles calculations in the two distinct forms of diarylethenes connected to gold electrodes. The combined approach clearly demonstrates that the IET spectra of single-molecule junctions show specific vibrational features that can be used to identify different isomeric molecular states by transport experiments.
Collapse
Affiliation(s)
- Youngsang Kim
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Lam Research, Fremont, California 94538, United States
| | - Safa G Bahoosh
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
| | - Dmytro Sysoiev
- Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
| | - Thomas Huhn
- Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
| | - Fabian Pauly
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
- Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa 904-0395, Japan
| | - Elke Scheer
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
| |
Collapse
|
31
|
Abstract
Low-temperature electronic transport measurements with high energy resolution require both effective low-pass filtering of high-frequency input noise and an optimized thermalization of the electronic system of the experiment. In recent years, elaborate filter designs have been developed for cryogenic low-level measurements, driven by the growing interest in fundamental quantum-physical phenomena at energy scales corresponding to temperatures in the few millikelvin regime. However, a single filter concept is often insufficient to thermalize the electronic system to the cryogenic bath and eliminate spurious high frequency noise. Moreover, the available concepts often provide inadequate filtering to operate at temperatures below 10 mK, which are routinely available now in dilution cryogenic systems. Herein we provide a comprehensive analysis of commonly used filter types, introduce a novel compact filter type based on ferrite compounds optimized for the frequency range above 20 GHz, and develop an improved filtering scheme providing adaptable broad-band low-pass characteristic for cryogenic low-level and quantum measurement applications at temperatures down to few millikelvin.
Collapse
Affiliation(s)
- M Thalmann
- Department of Physics, University of Konstanz, 78464 Konstanz, Germany
| | - H-F Pernau
- Department of Physics, University of Konstanz, 78464 Konstanz, Germany
| | - C Strunk
- Institute of Experimental Physics, University of Regensburg, 930253 Regensburg, Germany
| | - E Scheer
- Department of Physics, University of Konstanz, 78464 Konstanz, Germany
| | - T Pietsch
- Department of Physics, University of Konstanz, 78464 Konstanz, Germany
| |
Collapse
|
32
|
Jana A, Scheer E, Polarz S. Synthesis of graphene-transition metal oxide hybrid nanoparticles and their application in various fields. Beilstein J Nanotechnol 2017; 8:688-714. [PMID: 28462071 PMCID: PMC5372707 DOI: 10.3762/bjnano.8.74] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 02/06/2017] [Indexed: 05/20/2023]
Abstract
Single layer graphite, known as graphene, is an important material because of its unique two-dimensional structure, high conductivity, excellent electron mobility and high surface area. To explore the more prospective properties of graphene, graphene hybrids have been synthesised, where graphene has been integrated with other important nanoparticles (NPs). These graphene-NP hybrid structures are particularly interesting because after hybridisation they not only display the individual properties of graphene and the NPs, but also they exhibit further synergistic properties. Reduced graphene oxide (rGO), a graphene-like material, can be easily prepared by reduction of graphene oxide (GO) and therefore offers the possibility to fabricate a large variety of graphene-transition metal oxide (TMO) NP hybrids. These hybrid materials are promising alternatives to reduce the drawbacks of using only TMO NPs in various applications, such as anode materials in lithium ion batteries (LIBs), sensors, photocatalysts, removal of organic pollutants, etc. Recent studies have shown that a single graphene sheet (GS) has extraordinary electronic transport properties. One possible route to connecting those properties for application in electronics would be to prepare graphene-wrapped TMO NPs. In this critical review, we discuss the development of graphene-TMO hybrids with the detailed account of their synthesis. In addition, attention is given to the wide range of applications. This review covers the details of graphene-TMO hybrid materials and ends with a summary where an outlook on future perspectives to improve the properties of the hybrid materials in view of applications are outlined.
Collapse
Affiliation(s)
- Arpita Jana
- Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
| | - Elke Scheer
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
| | - Sebastian Polarz
- Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
| |
Collapse
|
33
|
Hayakawa R, Karimi MA, Wolf J, Huhn T, Zöllner MS, Herrmann C, Scheer E. Large Magnetoresistance in Single-Radical Molecular Junctions. Nano Lett 2016; 16:4960-4967. [PMID: 27458666 DOI: 10.1021/acs.nanolett.6b01595] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Organic radicals are promising building blocks for molecular spintronics. Little is known about the role of unpaired electrons for electron transport at the single-molecule level. Here, we examine the impact of magnetic fields on electron transport in single oligo(p-phenyleneethynylene) (OPE)-based radical molecular junctions, which are formed with a mechanically controllable break-junction technique at a low temperature of 4.2 K. Surprisingly huge positive magnetoresistances (MRs) of 16 to 287% are visible for a magnetic field of 4 T, and the values are at least 1 order of magnitude larger than those of the analogous pristine OPE (2-4%). Rigorous analysis of the MR and of current-voltage and inelastic electron-tunneling spectroscopy measurements reveal an effective reduction of the electronic coupling between the current-carrying molecular orbital and the electrodes with increasing magnetic field. We suggest that the large MR for the single-radical molecular junctions might be ascribed to a loss of phase coherence of the charge carriers induced by the magnetic field. Although further investigations are required to reveal the mechanism underlying the strong MR, our findings provide a potential approach for tuning charge transport in metal-molecule junctions with organic radicals.
Collapse
Affiliation(s)
- Ryoma Hayakawa
- International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science , 1-1 Namiki, Tsukuba 305-0044, Japan
| | | | | | | | - Martin Sebastian Zöllner
- Institute for Inorganic and Applied Chemistry, University of Hamburg , Martin-Luther-King-Platz 6, 20146 Hamburg, Germany
| | - Carmen Herrmann
- Institute for Inorganic and Applied Chemistry, University of Hamburg , Martin-Luther-King-Platz 6, 20146 Hamburg, Germany
| | | |
Collapse
|
34
|
Ghafoori G, Boneberg J, Leiderer P, Scheer E. Tuning the transmission of surface plasmon polaritons across nano and micro gaps in gold stripes. Opt Express 2016; 24:17313-17320. [PMID: 27464180 DOI: 10.1364/oe.24.017313] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We applied a far-field technique to measure the surface plasmon propagation over a wide range of gap sizes in thin gold stripes. This is realized with a grating technique which allows the excitation and out coupling of surface plasmon polaritons (SPPs). With this method the intensity can be monitored before and after the gap. The observations show that the SPPs can transmit over gaps with a width of 1μm with a probability of about 40% for Au stripe-waveguides (7 µm width) at a wavelength of 780 nm. The transmission decays exponentially above a gap size of 1 µm. The results also demonstrate that the transmission has non-monotonic behavior for gap sizes smaller than 1 µm that we attribute to excitation of Fabry-Perot modes and resonant localized plasmons within the gap. The experimental results are supported by numerical simulations using a Finite-Difference Time-Domain (FDTD) approach.
Collapse
|
35
|
Luka-Guth K, Hambsch S, Bloch A, Ehrenreich P, Briechle BM, Kilibarda F, Sendler T, Sysoiev D, Huhn T, Erbe A, Scheer E. Role of solvents in the electronic transport properties of single-molecule junctions. Beilstein J Nanotechnol 2016; 7:1055-67. [PMID: 27547624 PMCID: PMC4979908 DOI: 10.3762/bjnano.7.99] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 06/07/2016] [Indexed: 06/06/2023]
Abstract
We report on an experimental study of the charge transport through tunnel gaps formed by adjustable gold electrodes immersed into different solvents that are commonly used in the field of molecular electronics (ethanol, toluene, mesitylene, 1,2,4-trichlorobenzene, isopropanol, toluene/tetrahydrofuran mixtures) for the study of single-molecule contacts of functional molecules. We present measurements of the conductance as a function of gap width, conductance histograms as well as current-voltage characteristics of narrow gaps and discuss them in terms of the Simmons model, which is the standard model for describing transport via tunnel barriers, and the resonant single-level model, often applied to single-molecule junctions. One of our conclusions is that stable junctions may form from solvents as well and that both conductance-distance traces and current-voltage characteristics have to be studied to distinguish between contacts of solvent molecules and of molecules under study.
Collapse
Affiliation(s)
| | - Sebastian Hambsch
- Physics Department, University of Konstanz, D-78457 Konstanz, Germany
| | - Andreas Bloch
- Physics Department, University of Konstanz, D-78457 Konstanz, Germany
| | | | | | - Filip Kilibarda
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, D-01328 Dresden, Germany
| | - Torsten Sendler
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, D-01328 Dresden, Germany
| | - Dmytro Sysoiev
- Chemistry Department, University of Konstanz, D-78457 Konstanz, Germany
| | - Thomas Huhn
- Chemistry Department, University of Konstanz, D-78457 Konstanz, Germany
| | - Artur Erbe
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, D-01328 Dresden, Germany
| | - Elke Scheer
- Physics Department, University of Konstanz, D-78457 Konstanz, Germany
| |
Collapse
|
36
|
Ofarim A, Kopp B, Möller T, Martin L, Boneberg J, Leiderer P, Scheer E. Thermo-voltage measurements of atomic contacts at low temperature. Beilstein J Nanotechnol 2016; 7:767-75. [PMID: 27335765 PMCID: PMC4902067 DOI: 10.3762/bjnano.7.68] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Accepted: 05/10/2016] [Indexed: 05/28/2023]
Abstract
We report the development of a novel method to determine the thermopower of atomic-sized gold contacts at low temperature. For these measurements a mechanically controllable break junction (MCBJ) system is used and a laser source generates a temperature difference of a few kelvins across the junction to create a thermo-voltage. Since the temperature difference enters directly into the Seebeck coefficient S = -ΔV/ΔT, the determination of the temperature plays an important role. We present a method for the determination of the temperature difference using a combination of a finite element simulation, which reveals the temperature distribution of the sample, and the measurement of the resistance change due to laser heating of sensor leads on both sides next to the junction. Our results for the measured thermopower are in agreement with recent reports in the literature.
Collapse
Affiliation(s)
- Ayelet Ofarim
- Department of Physics, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
| | - Bastian Kopp
- Department of Physics, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
| | - Thomas Möller
- Department of Physics, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
| | - León Martin
- Department of Physics, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
| | - Johannes Boneberg
- Department of Physics, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
| | - Paul Leiderer
- Department of Physics, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
| | - Elke Scheer
- Department of Physics, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
| |
Collapse
|
37
|
Karimi MA, Bahoosh SG, Valášek M, Bürkle M, Mayor M, Pauly F, Scheer E. Identification of the current path for a conductive molecular wire on a tripodal platform. Nanoscale 2016; 8:10582-10590. [PMID: 27163116 DOI: 10.1039/c5nr08708b] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We present the chemical synthesis as well as charge transport measurements and calculations for a new tripodal platform based on a rigid 9,9'-spirobifluorene equipped with a phenylene-ethynylene wire. The transport experiments are performed with the help of the low-temperature mechanically controlled break junction technique with gold electrodes. By combining experimental and theoretical investigations of elastic and inelastic charge transport, we show that the current proceeds through the designated molecular wire and identify a binding geometry that is compatible with the experimental observations. The conductive molecular wire on the platform features a well-defined and relatively high conductance of the order of 10(-3)G0 despite the length of the current path of more than 1.7 nm, demonstrating that this platform is suitable to incorporate functional units like molecular switches or sensors.
Collapse
Affiliation(s)
- M A Karimi
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany.
| | - S G Bahoosh
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany.
| | - M Valášek
- Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology, P.O. Box 3640, 76021 Karlsruhe, Germany
| | - M Bürkle
- Nanosystem Research Institute (NRI) 'RICS', National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan
| | - M Mayor
- Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology, P.O. Box 3640, 76021 Karlsruhe, Germany and Department of Chemistry, University of Basel, 4056 Basel, Switzerland and Lehn Institute of Functional Materials (LIFM), Sun Yat-Sen University (SYSU), Xingang Rd. W., Guangzhou, China
| | - F Pauly
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany.
| | - E Scheer
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany.
| |
Collapse
|
38
|
Abstract
We report measurements of the shot noise on single-molecule Au-1,4-benzenedithiol-Au junctions, fabricated with the mechanically controllable break junction (MCBJ) technique at 4.2 K in a wide range of conductance values from 10(-2) to 0.24 conductance quanta. We introduce a simple measurement scheme using a current amplifier and a spectrum analyzer and that does not imply special requirements regarding the electrical leads. The experimental findings provide evidence that the current is carried by a single conduction channel throughout the whole conductance range. This observation suggests that the number of channels is limited by the Au-thiol bonds and that contributions due to direct tunneling from the Au to the π-system of the aromatic ring are negligible also for high conductance. The results are supported by quantum transport calculations using density functional theory.
Collapse
Affiliation(s)
- M A Karimi
- Department of Physics, University of Konstanz , 78457 Konstanz, Germany
| | - S G Bahoosh
- Department of Physics, University of Konstanz , 78457 Konstanz, Germany
| | - M Herz
- Department of Physics, University of Konstanz , 78457 Konstanz, Germany
| | - R Hayakawa
- Department of Physics, University of Konstanz , 78457 Konstanz, Germany
- International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science , 1-1 Namiki, Tsukuba 305-0044, Japan
| | - F Pauly
- Department of Physics, University of Konstanz , 78457 Konstanz, Germany
| | - E Scheer
- Department of Physics, University of Konstanz , 78457 Konstanz, Germany
| |
Collapse
|
39
|
Di Bernardo A, Diesch S, Gu Y, Linder J, Divitini G, Ducati C, Scheer E, Blamire M, Robinson J. Signature of magnetic-dependent gapless odd frequency states at superconductor/ferromagnet interfaces. Nat Commun 2015; 6:8053. [PMID: 26329811 PMCID: PMC4569701 DOI: 10.1038/ncomms9053] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 07/13/2015] [Indexed: 11/24/2022] Open
Abstract
The theory of superconductivity developed by Bardeen, Cooper and Schrieffer (BCS) explains the stabilization of electron pairs into a spin-singlet, even frequency, state by the formation of an energy gap within which the density of states is zero. At a superconductor interface with an inhomogeneous ferromagnet, a gapless odd frequency superconducting state is predicted, in which the Cooper pairs are in a spin-triplet state. Although indirect evidence for such a state has been obtained, the gap structure and pairing symmetry have not so far been determined. Here we report scanning tunnelling spectroscopy of Nb superconducting films proximity coupled to epitaxial Ho. These measurements reveal pronounced changes to the Nb subgap superconducting density of states on driving the Ho through a metamagnetic transition from a helical antiferromagnetic to a homogeneous ferromagnetic state for which a BCS-like gap is recovered. The results prove odd frequency spin-triplet superconductivity at superconductor/inhomogeneous magnet interfaces.
Collapse
Affiliation(s)
- A. Di Bernardo
- Department of Material Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK
| | - S. Diesch
- Department of Physics, University of Konstanz, Konstanz 78457, Germany
| | - Y. Gu
- Department of Material Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK
| | - J. Linder
- Department of Physics, Norwegian University of Science and Technology, Trondheim N-7491, Norway
| | - G. Divitini
- Department of Material Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK
| | - C. Ducati
- Department of Material Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK
| | - E. Scheer
- Department of Physics, University of Konstanz, Konstanz 78457, Germany
| | - M.G. Blamire
- Department of Material Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK
| | - J.W.A. Robinson
- Department of Material Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, UK
| |
Collapse
|
40
|
Stärk M, Schlickeiser F, Nissen D, Hebler B, Graus P, Hinzke D, Scheer E, Leiderer P, Fonin M, Albrecht M, Nowak U, Boneberg J. Controlling the magnetic structure of Co/Pd thin films by direct laser interference patterning. Nanotechnology 2015; 26:205302. [PMID: 25927344 DOI: 10.1088/0957-4484/26/20/205302] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Nanosecond pulsed two-beam laser interference is used to generate two-dimensional temperature patterns on a magnetic thin film sample. We show that the original domain structure of a [Co/Pd] multilayer thin film changes drastically upon exceeding the Curie temperature by thermal demagnetization. At even higher temperatures the multilayer system is irreversibly changed. In this area no out-of-plane magnetization can be found before and after a subsequent ac-demagnetization. These findings are supported by numerical simulations using the Landau-Lifshitz-Bloch formalism which shows the importance of defect sites and anisotropy changes to model the experiments. Thus, a one-dimensional temperature pattern can be transferred into a magnetic stripe pattern. In this way one can produce magnetic nanowire arrays with lateral dimensions of the order of 100 nm. Typical patterned areas are in the range of several square millimeters. Hence, the parallel direct laser interference patterning method of magnetic thin films is an attractive alternative to the conventional serial electron beam writing of magnetic nanostructures.
Collapse
Affiliation(s)
- Martin Stärk
- Department of Physics, University of Konstanz, Konstanz, Germany
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Sendler T, Luka-Guth K, Wieser M, Lokamani, Wolf J, Helm M, Gemming S, Kerbusch J, Scheer E, Huhn T, Erbe A. Light-Induced Switching of Tunable Single-Molecule Junctions. Adv Sci (Weinh) 2015; 2:1500017. [PMID: 27980936 PMCID: PMC5115361 DOI: 10.1002/advs.201500017] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Revised: 03/13/2015] [Indexed: 12/12/2023]
Abstract
A major goal of molecular electronics is the development and implementation of devices such as single-molecular switches. Here, measurements are presented that show the controlled in situ switching of diarylethene molecules from their nonconductive to conductive state in contact to gold nanoelectrodes via controlled light irradiation. Both the conductance and the quantum yield for switching of these molecules are within a range making the molecules suitable for actual devices. The conductance of the molecular junctions in the opened and closed states is characterized and the molecular level E0, which dominates the current transport in the closed state, and its level broadening Γ are identified. The obtained results show a clear light-induced ring forming isomerization of the single-molecule junctions. Electron withdrawing side-groups lead to a reduction of conductance, but do not influence the efficiency of the switching mechanism. Quantum chemical calculations of the light-induced switching processes correlate these observations with the fundamentally different low-lying electronic states of the opened and closed forms and their comparably small modification by electron-withdrawing substituents. This full characterization of a molecular switch operated in a molecular junction is an important step toward the development of real molecular electronics devices.
Collapse
Affiliation(s)
- Torsten Sendler
- Helmholtz-Zentrum Dresden - Rossendorf Bautzner Landstraße 400 01328 Dresden Germany
| | | | - Matthias Wieser
- Helmholtz-Zentrum Dresden - Rossendorf Bautzner Landstraße 400 01328 Dresden Germany
| | - Lokamani
- Institute for Materials Science and Max Bergmann Center of Biomaterials Dresden Technische Universität Dresden 01062 Dresden Germany
| | - Jannic Wolf
- Fachbereich Chemie Universität Konstanz 78457 Konstanz Germany
| | - Manfred Helm
- Helmholtz-Zentrum Dresden - Rossendorf Bautzner Landstraße 40001328 Dresden Germany; Center for Advancing Electronics Dresden Technische Universität Dresden 01062 Dresden Germany
| | - Sibylle Gemming
- Helmholtz-Zentrum Dresden - Rossendorf Bautzner Landstraße 40001328 Dresden Germany; Faculty of Science Technische Universität Chemnitz 09107 Chemnitz Germany
| | - Jochen Kerbusch
- Helmholtz-Zentrum Dresden - Rossendorf Bautzner Landstraße 40001328 Dresden Germany; Center for Advancing Electronics Dresden Technische Universität Dresden 01062 Dresden Germany
| | - Elke Scheer
- Department of Physics Universität Konstanz 78457 Konstanz Germany
| | - Thomas Huhn
- Fachbereich Chemie Universität Konstanz 78457 Konstanz Germany
| | - Artur Erbe
- Helmholtz-Zentrum Dresden - Rossendorf Bautzner Landstraße 400 01328 Dresden Germany
| |
Collapse
|
42
|
Affiliation(s)
- Elke Scheer
- Department of Physics, University of Konstanz, Universitätsstraβe 10, 78464 Konstanz, Germany
| |
Collapse
|
43
|
Abstract
We report low-temperature transport experiments on atomic-size contacts of bismuth that are fabricated using the mechanically controlled break-junction technique at low temperatures. We observe stable contacts with conductance values at fractions of one conductance quantum G0 = 2e(2)/h, as is expected for systems with long Fermi wavelength. We defer two preferred conductance scales: the lower one is in the order of 0.015 G0 and can be attributed to single-atom Bi contact, while the higher one amounts to 0.15 G0, as indicated by the appearance of multiples of this value in the conductance histogram. Rich magneto-transport behaviour with significant changes in the magneto-conductance is found in the whole conductance range. Although for the pristine samples and large contacts with G > 5 G0, indications for Shubnikov-de Haas oscillations are present, the smallest contacts show pronounced conductance fluctuations that decay rapidly when a magnetic field is applied. Moreover, large variations are observed when a finite bias voltage is applied. These findings are interpreted as the transition from the diffusive to the ballistic and the ultra-quantum regime when lowering the contact size.
Collapse
|
44
|
Benner D, Boneberg J, Nürnberger P, Waitz R, Leiderer P, Scheer E. Lateral and temporal dependence of the transport through an atomic gold contact under light irradiation: signature of propagating surface plasmon polaritons. Nano Lett 2014; 14:5218-5223. [PMID: 25089588 DOI: 10.1021/nl502165y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Metallic point contacts (MPCs) with dimensions comparable to the Fermi wavelength of conduction electrons act as electronic waveguides and might operate as plasmon transmitters. Here we present a correlated study of optical and conductance response of MPCs under irradiation with laser light. For elucidating the role of surface plasmon polaritons (SPPs), we integrate line gratings into the leads that increase the SPP excitation efficiency. By analyzing spatial, polarization, and time dependence, we identify two SPP contributions that we attribute to transmitted and decaying SPPs, respectively. The results demonstrate the role of SPPs for optically controlling the transport in metallic nanostructures and are important for designing opto-nanoelectronic devices.
Collapse
Affiliation(s)
- Daniel Benner
- Department of Physics, University of Konstanz , Universitätsstraße 10, 78464 Konstanz, Germany
| | | | | | | | | | | |
Collapse
|
45
|
Kim D, Jeong H, Lee H, Hwang WT, Wolf J, Scheer E, Huhn T, Jeong H, Lee T. Flexible molecular-scale electronic devices composed of diarylethene photoswitching molecules. Adv Mater 2014; 26:3968-3973. [PMID: 24687399 DOI: 10.1002/adma.201306316] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Revised: 02/21/2014] [Indexed: 06/03/2023]
Affiliation(s)
- Dongku Kim
- Department of Physics and Astronomy and Institute of Applied Physics, Seoul National University, Seoul, 151-747, Korea
| | | | | | | | | | | | | | | | | |
Collapse
|
46
|
Herz M, Bouvron S, Ćavar E, Fonin M, Belzig W, Scheer E. Fundamental quantum noise mapping with tunnelling microscopes tested at surface structures of subatomic lateral size. Nanoscale 2013; 5:9978-9983. [PMID: 23989889 DOI: 10.1039/c3nr02216a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We present a measurement scheme that enables quantitative detection of the shot noise in a scanning tunnelling microscope while scanning the sample. As test objects we study defect structures produced on an iridium single crystal at low temperatures. The defect structures appear in the constant current images as protrusions with curvature radii well below the atomic diameter. The measured power spectral density of the noise is very near to the quantum limit with Fano factor F = 1. While the constant current images show detailed structures expected for tunnelling involving d-atomic orbitals of Ir, we find the current noise to be without pronounced spatial variation as expected for shot noise arising from statistically independent events.
Collapse
Affiliation(s)
- Markus Herz
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany.
| | | | | | | | | | | |
Collapse
|
47
|
Schirm C, Matt M, Pauly F, Cuevas JC, Nielaba P, Scheer E. A current-driven single-atom memory. Nat Nanotechnol 2013; 8:645-8. [PMID: 23995456 DOI: 10.1038/nnano.2013.170] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2013] [Accepted: 07/24/2013] [Indexed: 05/27/2023]
Abstract
The possibility of fabricating electronic devices with functional building blocks of atomic size is a major driving force of nanotechnology. The key elements in electronic circuits are switches, usually realized by transistors, which can be configured to perform memory operations. Electronic switches have been miniaturized all the way down to the atomic scale. However, at such scales, three-terminal devices are technically challenging to implement. Here we show that a metallic atomic-scale contact can be operated as a reliable and fatigue-resistant two-terminal switch. We apply a careful electromigration protocol to toggle the conductance of an aluminium atomic contact between two well-defined values in the range of a few conductance quanta. Using the nonlinearities of the current-voltage characteristics caused by superconductivity in combination with molecular dynamics and quantum transport calculations, we provide evidence that the switching process is caused by the reversible rearrangement of single atoms. Owing to its hysteretic behaviour with two distinct states, this two-terminal switch can be used as a non-volatile information storage element.
Collapse
Affiliation(s)
- C Schirm
- Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
| | | | | | | | | | | |
Collapse
|
48
|
Sysoiev D, Yushchenko T, Scheer E, Groth U, Steiner UE, Exner TE, Huhn T. Pronounced effects on switching efficiency of diarylcycloalkenes upon cycloalkene ring contraction. Chem Commun (Camb) 2013; 48:11355-7. [PMID: 23073076 DOI: 10.1039/c2cc35726g] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Several difurylperfluorocyclobutenes showing reversible photochromism were synthesized. In comparison to their cyclopentene homologues they show enhanced quantum yields for ring opening but reduced quantum yields for ring closure. X-ray structure analysis and quantum chemical calculations provide a conclusive explanation for such a behaviour.
Collapse
Affiliation(s)
- Dmytro Sysoiev
- Fachbereich Chemie, Universität Konstanz, D-78457 Konstanz, Germany
| | | | | | | | | | | | | |
Collapse
|
49
|
Dickreuter S, Gleixner J, Kolloch A, Boneberg J, Scheer E, Leiderer P. Mapping of plasmonic resonances in nanotriangles. Beilstein J Nanotechnol 2013; 4:588-602. [PMID: 24205453 PMCID: PMC3817793 DOI: 10.3762/bjnano.4.66] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Accepted: 09/11/2013] [Indexed: 05/21/2023]
Abstract
Plasmonic resonances in metallic nano-triangles have been investigated by irradiating these structures with short laser pulses and imaging the resulting ablation and melting patterns. The triangular gold structures were prepared on Si substrates and had a thickness of 40 nm and a side length of ca. 500 nm. Irradiation was carried out with single femtosecond and picosecond laser pulses at a wavelength of 800 nm, which excited higher order plasmon modes in these triangles. The ablation distribution as well as the local melting of small parts of the nanostructures reflect the regions of large near-field enhancement. The observed patterns are reproduced in great detail by FDTD simulations with a 3-dimensional model, provided that the calculations are not based on idealized, but on realistic structures. In this realistic model, details like the exact shape of the triangle edges and the dielectric environment of the structures are taken into account. The experimental numbers found for the field enhancement are typically somewhat smaller than the calculated ones. The results demonstrate the caveats for FDTD simulations and the potential and the limitations of "near field photography" by local ablation and melting for the mapping of complex plasmon fields and their applications.
Collapse
Affiliation(s)
- Simon Dickreuter
- Physics Department, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
| | - Julia Gleixner
- Physics Department, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
| | - Andreas Kolloch
- Physics Department, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
| | - Johannes Boneberg
- Physics Department, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
| | - Elke Scheer
- Physics Department, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
| | - Paul Leiderer
- Physics Department, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
| |
Collapse
|
50
|
Kim Y, Garcia-Lekue A, Sysoiev D, Frederiksen T, Groth U, Scheer E. Charge transport in azobenzene-based single-molecule junctions. Phys Rev Lett 2012; 109:226801. [PMID: 23368145 DOI: 10.1103/physrevlett.109.226801] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Indexed: 05/21/2023]
Abstract
Azobenzene-derivative molecules change their conformation as a result of a cis-trans transition when exposed to ultraviolet or visible light irradiation and this is expected to induce a significant variation in the conductance of molecular devices. Despite extensive investigations carried out on this type of molecule, a detailed understanding of the charge transport for the two isomers is still lacking. We report a combined experimental and theoretical analysis of electron transport through azobenzene-derivative single-molecule break junctions with Au electrodes. Current-voltage and inelastic electron tunneling spectroscopy (IETS) measurements performed at 4.2 K are interpreted based on first-principles calculations of electron transmission and IETS spectra. This qualitative study unravels the origin of a slightly higher conductance of junctions with the cis isomer and demonstrates that IETS spectra of cis and trans forms show distinct vibrational fingerprints that can be used for identifying the isomer.
Collapse
Affiliation(s)
- Youngsang Kim
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
| | | | | | | | | | | |
Collapse
|