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Dziobek-Garrett R, Kempa TJ. Excitons at the interface of 2D TMDs and molecular semiconductors. J Chem Phys 2024; 160:200902. [PMID: 38804485 DOI: 10.1063/5.0206417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Accepted: 05/02/2024] [Indexed: 05/29/2024] Open
Abstract
Van der Waals heterostructures (vdWHs) of vertically stacked two-dimensional (2D) atomic crystals have been used to elicit intriguing phenomena stemming from strong electronic correlations, magnetic textures, and interlayer excitons spawned at the heterointerface. However, vdWHs comprised of heterointerfaces between these 2D atomic crystal lattices and molecular assemblies are emerging as equally intriguing platforms supporting properties to be harnessed for photovoltaic energy conversion, photodetection, spin-selective charge injection, and quantum emission. In this perspective, we summarize recent research examining exciton dynamics in heterostructures between semiconducting 2D transition metal dichalcogenides and molecular organic semiconductors. We discuss methods for assembly of these heterostructures, the nature of interlayer or charge-transfer excitons at transition-metal dichalcogenide (TMD)-molecule interfaces, explicit exciton transfer between organics and TMDs, and other interfacial phenomena driven by the merger of these two material classes. We also suggest key new research directions extending the remit of these 2D atomic-molecular lattice heterointerfaces into the domains of condensed matter physics, quantum sensing, and energy conversion.
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Affiliation(s)
| | - Thomas J Kempa
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA
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2
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Zhang Q, Li M, Li L, Geng D, Chen W, Hu W. Recent progress in emerging two-dimensional organic-inorganic van der Waals heterojunctions. Chem Soc Rev 2024; 53:3096-3133. [PMID: 38373059 DOI: 10.1039/d3cs00821e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2024]
Abstract
Two-dimensional (2D) materials have attracted significant attention in recent decades due to their exceptional optoelectronic properties. Among them, to meet the growing demand for multifunctional applications, 2D organic-inorganic van der Waals (vdW) heterojunctions have become increasingly popular in the development of optoelectronic devices. These heterojunctions demonstrate impressive capability to synergistically combine the favourable characteristics of organic and inorganic materials, thereby offering a wide range of advantages. Also, they enable the creation of innovative device structures and introduce novel functionalities in existing 2D materials, avoiding the need for lattice matching in different material systems. Presently, researchers are actively working on improving the performance of devices based on 2D organic-inorganic vdW heterojunctions by focusing on enhancing the quality of 2D materials, precise stacking methods, energy band regulation, and material selection. Therefore, this review presents a thorough examination of the emerging 2D organic-inorganic vdW heterojunctions, including their classification, fabrication, and corresponding devices. Additionally, this review offers profound and comprehensive insight into the challenges in this field to inspire future research directions. It is expected to propel researchers to harness the extraordinary capabilities of 2D organic-inorganic vdW heterojunctions for a wider range of applications by further advancing the understanding of their fundamental properties, expanding the range of available materials, and exploring novel device architectures. The ongoing research and development in this field hold potential to unlock captivating advancements and foster practical applications across diverse industries.
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Affiliation(s)
- Qing Zhang
- Key Laboratory of Organic Integrated Circuit, Ministry of Education & Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, School of Science, Tianjin University, Tianjin 300072, China.
- Department of Chemistry, National University of Singapore, Singapore 117543, Singapore.
- Beijing National Laboratory for Molecular Sciences, Beijing 100190, China
- Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China
| | - Menghan Li
- Key Laboratory of Organic Integrated Circuit, Ministry of Education & Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, School of Science, Tianjin University, Tianjin 300072, China.
- Beijing National Laboratory for Molecular Sciences, Beijing 100190, China
- Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China
| | - Lin Li
- College of Chemistry, Tianjin Normal University, Tianjin 300387, China.
- Beijing National Laboratory for Molecular Sciences, Beijing 100190, China
| | - Dechao Geng
- Key Laboratory of Organic Integrated Circuit, Ministry of Education & Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, School of Science, Tianjin University, Tianjin 300072, China.
- Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Fuzhou 350207, China
- Haihe Laboratory of Sustainable Chemical Transformations, Tianjin 300192, China
- Beijing National Laboratory for Molecular Sciences, Beijing 100190, China
- Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China
| | - Wei Chen
- Department of Chemistry, National University of Singapore, Singapore 117543, Singapore.
- Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Fuzhou 350207, China
| | - Wenping Hu
- Key Laboratory of Organic Integrated Circuit, Ministry of Education & Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, School of Science, Tianjin University, Tianjin 300072, China.
- Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Fuzhou 350207, China
- Haihe Laboratory of Sustainable Chemical Transformations, Tianjin 300192, China
- Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China
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3
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Frimpong J, Liu ZF. Generalized Substrate Screening GW for Covalently Bonded Interfaces. J Phys Chem Lett 2024; 15:2133-2141. [PMID: 38364077 DOI: 10.1021/acs.jpclett.3c03470] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2024]
Abstract
An accurate description of the interfacial quasiparticle electronic structure is key to the design of heterogeneous materials. While the first-principles GW approach is state-of-the-art, the computational cost is high for large interface systems. This has led to the substrate screening GW approach for weakly coupled interfaces, which breaks down for covalently bonded interfaces. In this work, we present the generalized substrate screening GW approach, based on the following two considerations: (i) the contribution of the interfacial covalent bond to the polarizability can be efficiently calculated with a low energy cutoff; (ii) the contribution of the deprotonated adsorbate to the interface polarizability can be well approximated by that of the protonated molecule. Our approach is exemplified using interfaces formed between benzene-1,4-dithiol (BDT) and Au(111), which feature the widely used Au-S bonds in experiments. Our work provides a robust and simple scheme for accurate and efficient GW calculations of covalently bonded interfaces.
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Affiliation(s)
- Joseph Frimpong
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - Zhen-Fei Liu
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
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4
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Günder D, Axt M, Witte G. Heteroepitaxy in Organic/TMD Hybrids and Challenge to Achieve it for TMD Monolayers: The Case of Pentacene on WS 2 and WSe 2. ACS APPLIED MATERIALS & INTERFACES 2024; 16:1911-1920. [PMID: 38154080 DOI: 10.1021/acsami.3c15829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2023]
Abstract
The intriguing photophysical properties of monolayer stacks of different transition-metal dichalcogenides (TMDs), revealing rich exciton physics including interfacial and moiré excitons, have recently prompted an extension of similar investigations to hybrid systems of TMDs and organic films, as the latter combine large photoabsorption cross sections with the ability to tailor energy levels by targeted synthesis. To go beyond single-molecule photoexcitations and exploit the excitonic signatures of organic solids, crystalline molecular films are required. Moreover, a defined registry on the substrate, ideally an epitaxy, is desirable to also achieve an excitonic coupling in momentum space. This poses a certain challenge as excitonic dipole moments of organic films are closely related to the molecular orientation and film structure, which critically depend on the support roughness. Using X-ray diffraction, optical polarization, and atomic force microscopy, we analyzed the structure of pentacene (PEN) multilayer films grown on WSe2(001) and WS2(001) and identified an epitaxial alignment. While (022)-oriented PEN films are formed on both substrates, their azimuthal orientations are quite different, showing an alignment of the molecular L-axis along the ⟨ 110 ⟩ WSe 2 and ⟨ 100 ⟩ WS 2 directions. This intrinsic epitaxial PEN growth depends, however, sensitively on the substrates surface quality. While it occurs on exfoliated TMD single crystals and multilayer flakes, it is hardly found on exfoliated monolayers, which often exhibit bubbles and wrinkles. This enhances the surface roughness and results in (001)-oriented PEN films with upright molecular orientation but without any azimuthal alignment. However, monolayer flakes can be smoothed by AFM operated in contact mode or by transferring to ultrasmooth substrates such as hBN, which again yields epitaxial PEN films. As different PEN orientations result in different characteristic film morphologies (elongated mesa islands vs pyramidal dendrites), which can be easily distinguished by AFM or optical microscopy, this provides a simple means to judge the roughness of the used TMD surface.
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Affiliation(s)
- Darius Günder
- Molekulare Festkörperphysik, Philipps-Universität Marburg, Marburg 35032, Germany
| | - Marleen Axt
- Oberflächenphysik, Philipps-Universität Marburg, Marburg 35032, Germany
| | - Gregor Witte
- Molekulare Festkörperphysik, Philipps-Universität Marburg, Marburg 35032, Germany
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5
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Liu XY, Chen WK, Fang WH, Cui G. Nonadiabatic Dynamics Simulations for Photoinduced Processes in Molecules and Semiconductors: Methodologies and Applications. J Chem Theory Comput 2023. [PMID: 37984502 DOI: 10.1021/acs.jctc.3c00960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Nonadiabatic dynamics (NAMD) simulations have become powerful tools for elucidating complicated photoinduced processes in various systems from molecules to semiconductor materials. In this review, we present an overview of our recent research on photophysics of molecular systems and periodic semiconductor materials with the aid of ab initio NAMD simulation methods implemented in the generalized trajectory surface-hopping (GTSH) package. Both theoretical backgrounds and applications of the developed NAMD methods are presented in detail. For molecular systems, the linear-response time-dependent density functional theory (LR-TDDFT) method is primarily used to model electronic structures in NAMD simulations owing to its balanced efficiency and accuracy. Moreover, the efficient algorithms for calculating nonadiabatic coupling terms (NACTs) and spin-orbit couplings (SOCs) have been coded into the package to increase the simulation efficiency. In combination with various analysis techniques, we can explore the mechanistic details of the photoinduced dynamics of a range of molecular systems, including charge separation and energy transfer processes in organic donor-acceptor structures, ultrafast intersystem crossing (ISC) processes in transition metal complexes (TMCs), and exciton dynamics in molecular aggregates. For semiconductor materials, we developed the NAMD methods for simulating the photoinduced carrier dynamics within the framework of the Kohn-Sham density functional theory (KS-DFT), in which SOC effects are explicitly accounted for using the two-component, noncollinear DFT method. Using this method, we have investigated the photoinduced carrier dynamics at the interface of a variety of van der Waals (vdW) heterojunctions, such as two-dimensional transition metal dichalcogenides (TMDs), carbon nanotubes (CNTs), and perovskites-related systems. Recently, we extended the LR-TDDFT-based NAMD method for semiconductor materials, allowing us to study the excitonic effects in the photoinduced energy transfer process. These results demonstrate that the NAMD simulations are powerful tools for exploring the photodynamics of molecular systems and semiconductor materials. In future studies, the NAMD simulation methods can be employed to elucidate experimental phenomena and reveal microscopic details as well as rationally design novel photofunctional materials with desired properties.
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Affiliation(s)
- Xiang-Yang Liu
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu 610068, P. R. China
| | - Wen-Kai Chen
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Wei-Hai Fang
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
- Hefei National Laboratory, Hefei 230088, P. R. China
| | - Ganglong Cui
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
- Hefei National Laboratory, Hefei 230088, P. R. China
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6
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Zhang S, Sun D, Sun J, Ma K, Wei Z, Park JY, Coffey AH, Zhu C, Dou L, Huang L. Unraveling the Effect of Stacking Configurations on Charge Transfer in WS 2 and Organic Semiconductor Heterojunctions. PRECISION CHEMISTRY 2023; 1:443-451. [PMID: 37771515 PMCID: PMC10526440 DOI: 10.1021/prechem.3c00057] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2023] [Revised: 06/06/2023] [Accepted: 06/08/2023] [Indexed: 09/30/2023]
Abstract
Photoinduced interfacial charge transfer plays a critical role in energy conversion involving van der Waals (vdW) heterostructures constructed of inorganic nanostructures and organic materials. However, the effect of molecular stacking configurations on charge transfer dynamics is less understood. In this study, we demonstrated the tunability of interfacial charge separation in a type-II heterojunction between monolayer (ML) WS2 and an organic semiconducting molecule [2-(3″',4'-dimethyl-[2,2':5',2':5″,2″'-quaterthiophen]-5-yl)ethan-1-ammonium halide (4Tm)] by rational design of relative stacking configurations. The assembly between ML-WS2 and the 4Tm molecule forms a face-to-face stacking when 4Tm molecules are in a self-aggregation state. In contrast, a face-to-edge stacking is observed when 4Tm molecule is incorporated into a 2D organic-inorganic hybrid perovskite lattice. The face-to-face stacking was proved to be more favorable for hole transfer from WS2 to 4Tm and led to interlayer excitons (IEs) emission. Transient absorption measurements show that the hole transfer occurs on a time scale of 150 fs. On the other hand, the face-to-edge stacking resulted in much slower hole transfer without formation of IEs. This inefficient hole transfer occurs on a similar time scale as A exciton recombination in WS2, leading to the formation of negative trions. These investigations offer important fundamental insights into the charge transfer processes at organic-inorganic interfaces.
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Affiliation(s)
- Shuchen Zhang
- Davidson
School of Chemical Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Dewei Sun
- Department
of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Jiaonan Sun
- Davidson
School of Chemical Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Ke Ma
- Davidson
School of Chemical Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Zitang Wei
- Davidson
School of Chemical Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Jee Yung Park
- Davidson
School of Chemical Engineering, Purdue University, West Lafayette, Indiana 47907, United States
| | - Aidan H. Coffey
- Advanced
Light Source, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Chenhui Zhu
- Advanced
Light Source, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
| | - Letian Dou
- Davidson
School of Chemical Engineering, Purdue University, West Lafayette, Indiana 47907, United States
- Birck
Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States
| | - Libai Huang
- Department
of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
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7
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Wang X, Liu S, Chen Y, Zheng Y, Li L. Properties at the interface of the pristine CdSe and core-shell CdSe-ZnS quantum dots with ultrathin monolayers of two-dimensional MX 2 (M: Mo, W; X: S, Se, Te) heterostructures from density functional theory. J Mol Model 2022; 28:220. [PMID: 35831761 DOI: 10.1007/s00894-022-05194-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 06/13/2022] [Indexed: 11/25/2022]
Abstract
In this work, eight van der Waals heterojunctions based on CdSe or CdSe-ZnS quantum dots (QDs) and four commonly used two-dimensional transition metal dichalcogenides (2D-TMDs) are theoretically designed. On the basis of the constructed structures, density functional theory (DFT) method is employed to investigate the structural and optoelectronic related properties of these heterojunctions in detail. Specifically, their electronic properties including charge density differences, density of states, and band offsets are calculated, based on which band alignment types as well as their potentials as novel photovoltaic materials are discussed. According to these calculations, we proposed that several van der Waals heterostructures including MoS2/CdSe, MoTe2/CdSe, WSe2/CdSe, MoTe2/CdSe-ZnS, and WSe2/CdSe-ZnS might be used as potential photovoltaic materials due to their type II band alignment characteristics. Moreover, the WSe2/CdSe-ZnS heterostructure is expected to have optimal photovoltaic performance attributed to their large bond offsets and band gaps, which could not only facilitate charge separation processes, but also slow down charge recombination. Our present theoretical work could be helpful for the future experimental design of novel CdSe QDs and 2D-TMD based van der Waals heterostructures with excellent photovoltaic performances.
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Affiliation(s)
- Xin Wang
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu, 610068, China
| | - Shuai Liu
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu, 610068, China
| | - Yang Chen
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu, 610068, China
| | - Yan Zheng
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu, 610068, China.
| | - Laicai Li
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu, 610068, China.
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8
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Melani G, Guerrero-Felipe JP, Valencia AM, Krumland J, Cocchi C, Iannuzzi M. Donors, acceptors, and a bit of aromatics: electronic interactions of molecular adsorbates on hBN and MoS 2 monolayers. Phys Chem Chem Phys 2022; 24:16671-16679. [PMID: 35766517 DOI: 10.1039/d2cp01502a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The design of low-dimensional organic-inorganic interfaces for the next generation of opto-electronic applications requires in-depth understanding of the microscopic mechanisms ruling electronic interactions in these systems. In this work, we present a first-principles study based on density-functional theory inspecting the structural, energetic, and electronic properties of five molecular donors and acceptors adsorbed on freestanding hexagonal boron nitride (hBN) and molybdenum disulfide (MoS2) monolayers. All considered interfaces are stable, due to the crucial contribution of dispersion interactions, which are maximized by the overall flat arrangement of the physisorbed molecules on both substrates. The level alignment of the hybrid systems depends on the characteristics of the constituents. On hBN, both type-I and type-II interfaces may form, depending on the relative energies of the frontier orbitals with respect to the vacuum level. On the other hand, all MoS2-based hybrid systems exhibit a type-II level alignment, with the molecular frontier orbitals positioned across the energy gap of the semiconductor. The electronic structure of the hybrid materials is further determined by the formation of interfacial dipole moments and by the wave-function hybridization between the organic and inorganic constituents. These results provide important indications for the design of novel low-dimensional hybrid materials with suitable characteristics for opto-electronics.
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Affiliation(s)
- Giacomo Melani
- Department of Chemistry, Universität Zürich, 8057 Zürich, Switzerland. .,Present Address: Pritzker School of Molecular Engineering, University of Chicago, 60637, Chicago, USA
| | - Juan Pablo Guerrero-Felipe
- Physics Department and IRIS Adlesrshof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany. .,Department of Physics, Free University Berlin, 14195 Berlin, Germany
| | - Ana M Valencia
- Physics Department and IRIS Adlesrshof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany. .,Institute of Physics, Carl-von-Ossietzy Universität Oldenburg, 26129 Oldenburg, Germany
| | - Jannis Krumland
- Physics Department and IRIS Adlesrshof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany.
| | - Caterina Cocchi
- Physics Department and IRIS Adlesrshof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany. .,Institute of Physics, Carl-von-Ossietzy Universität Oldenburg, 26129 Oldenburg, Germany
| | - Marcella Iannuzzi
- Department of Chemistry, Universität Zürich, 8057 Zürich, Switzerland.
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9
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Wang D, Lu X, Cai L, Zhang L, Feng S, Zhang W, Yang M, Wu J, Wang Z, Wee ATS. Low-Dimensional Porous Carbon Networks Using Single-/Triple-Coupling Polycyclic Hydrocarbon Precursors. ACS NANO 2022; 16:9843-9851. [PMID: 35657207 DOI: 10.1021/acsnano.2c03909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Polycyclic hydrocarbons (PHs) share the same hexagonal structure of sp2 carbons as graphene but possess an energy gap due to quantum confinement effect. PHs can be synthesized by a bottom-up strategy starting from small building blocks covalently bonded into large 2D organic sheets. Further investigation of the role of the covalent bonding/coupling ways on their electronic properties is needed. Here, we demonstrate a surface-mediated synthesis of hexa-peri-hexabenzocoronene (HBC) and its extended HBC oligomers (dimers, trimers, and tetramers) via single- and triple-coupling ways and reveal the implication of different covalent bonding on their electronic properties. High-resolution low-temperature scanning tunneling microscopy and noncontact atomic force microscopy are employed to in situ determine the atomic structures of as-synthesized HBC oligomers. Scanning tunneling spectroscopy measurements show that the length extension of HBC oligomers narrows the energy gap between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). Furthermore, the energy gaps of triple-coupling HBC oligomers are smaller and decrease more significantly than that of the single-coupling ones. We hypothesize that the triple coupling promotes a more effective delocalization of π-electrons than the single coupling, according to density functional theory calculations. We also demonstrate that the HBC oligomers can further extend across the substrate steps to achieve conjugated polymers and large-area porous carbon networks.
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Affiliation(s)
- Dingguan Wang
- SZU-NUS Collaborative Innovation Center for Optoelectronic Science and Technology, International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, China
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117551, Singapore
| | - Xuefeng Lu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- Department of Materials Science, Fudan University, Shanghai 200438, China
| | - Liangliang Cai
- SZU-NUS Collaborative Innovation Center for Optoelectronic Science and Technology, International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, China
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117551, Singapore
| | - Lei Zhang
- SZU-NUS Collaborative Innovation Center for Optoelectronic Science and Technology, International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, China
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117551, Singapore
| | - Shuo Feng
- SZU-NUS Collaborative Innovation Center for Optoelectronic Science and Technology, International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, China
| | - Wenjing Zhang
- SZU-NUS Collaborative Innovation Center for Optoelectronic Science and Technology, International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, China
| | - Ming Yang
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
| | - Jishan Wu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Zhuo Wang
- SZU-NUS Collaborative Innovation Center for Optoelectronic Science and Technology, International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, China
| | - Andrew T S Wee
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117551, Singapore
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10
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Adeniran O, Liu ZF. Quasiparticle electronic structure of phthalocyanine:TMD interfaces from first-principles GW. J Chem Phys 2021; 155:214702. [PMID: 34879665 DOI: 10.1063/5.0072995] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Interfaces formed between monolayer transition metal dichalcogenides and (metallo)phthalocyanine molecules are promising in energy applications and provide a platform for studying mixed-dimensional molecule-semiconductor heterostructures in general. An accurate characterization of the frontier energy level alignment at these interfaces is key in the fundamental understanding of the charge transfer dynamics between the two photon absorbers. Here, we employ the first-principles substrate screening GW approach to quantitatively characterize the quasiparticle electronic structure of a series of interfaces: metal-free phthalocyanine (H2Pc) adsorbed on monolayer MX2 (M = Mo, W; X = S, Se) and zinc phthalocyanine (ZnPc) adsorbed on MoX2 (X = S, Se). Furthermore, we reveal the dielectric screening effect of the commonly used α-quartz (SiO2) substrate on the H2Pc:MoS2 interface using the dielectric embedding GW approach. Our calculations furnish a systematic set of GW results for these interfaces, providing the structure-property relationship across a series of similar systems and benchmarks for future experimental and theoretical studies.
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Affiliation(s)
- Olugbenga Adeniran
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
| | - Zhen-Fei Liu
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
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11
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Zheng YJ, Zhang Q, Odunmbaku O, Ou Z, Li M, Sun K. Tuning the carrier type and density of monolayer tin selenide via organic molecular doping. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 34:085001. [PMID: 34736236 DOI: 10.1088/1361-648x/ac3691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2021] [Accepted: 11/04/2021] [Indexed: 06/13/2023]
Abstract
Utilizing first-principles calculations, charge transfer doping process of single layer tin selenide (SL-SnSe) via the surface adsorption of various organic molecules was investigated. Effective p-type SnSe, with carrier concentration exceeding 3.59 × 1013 cm-2, was obtained upon adsorption of tetracyanoquinodimethane or 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane on SL-SnSe due to their lowest unoccupied molecular orbitals acting as shallow acceptor states. While we could not obtain effective n-type SnSe through adsorption of tetrathiafulvalene (TTF) or 1,4,5,8-tetrathianaphthalene on pristine SnSe due to their highest occupied molecular orbitals (HOMO) being far from the conduction band edge of SnSe, this disadvantageous situation can be amended by the introduction of an external electric field perpendicular to the monolayer surface. It is found that Snvacwill facilitate charge transfer from TTF to SnSe through introducing an unoccupied gap state just above the HOMO of TTF, thereby partially compensating for the p-type doping effect of Snvac. Our results show that both effective p-type and n-type SnSe can be obtained and tuned by charge transfer doping, which is necessary to promote its applications in nanoelectronics, thermoelectrics and optoelectronics.
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Affiliation(s)
- Yu Jie Zheng
- Key Laboratory of Low-grade Energy Utilization Technologies and Systems of the Ministry of Education of China, Chongqing University, Chongqing 400044, People's Republic of China
- School of Energy and Power Engineering, Chongqing University, Chongqing 400044, People's Republic of China
| | - Qi Zhang
- School of Energy and Power Engineering, Chongqing University, Chongqing 400044, People's Republic of China
| | - Omololu Odunmbaku
- Key Laboratory of Low-grade Energy Utilization Technologies and Systems of the Ministry of Education of China, Chongqing University, Chongqing 400044, People's Republic of China
- School of Energy and Power Engineering, Chongqing University, Chongqing 400044, People's Republic of China
| | - Zeping Ou
- School of Energy and Power Engineering, Chongqing University, Chongqing 400044, People's Republic of China
| | - Meng Li
- Key Laboratory of Low-grade Energy Utilization Technologies and Systems of the Ministry of Education of China, Chongqing University, Chongqing 400044, People's Republic of China
- School of Energy and Power Engineering, Chongqing University, Chongqing 400044, People's Republic of China
| | - Kuan Sun
- Key Laboratory of Low-grade Energy Utilization Technologies and Systems of the Ministry of Education of China, Chongqing University, Chongqing 400044, People's Republic of China
- School of Energy and Power Engineering, Chongqing University, Chongqing 400044, People's Republic of China
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12
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13
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Cheng NLQ, Xuan F, Spataru CD, Quek SY. Charge Transfer Screening and Energy Level Alignment at Complex Organic-Inorganic Interfaces: A Tractable Ab Initio GW Approach. J Phys Chem Lett 2021; 12:8841-8846. [PMID: 34492190 DOI: 10.1021/acs.jpclett.1c02302] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Complex organic-inorganic interfaces are important for device and sensing applications. Charge transfer doping is prevalent in such applications and can affect the interfacial energy level alignments (ELA), which are determined by many-body interactions. We develop an approximate ab initio many-body GW approach that can capture many-body interactions due to interfacial charge transfer. The approach uses significantly less resources than a regular GW calculation but gives excellent agreement with benchmark GW calculations on an F4TCNQ/graphene interface. We find that many-body interactions due to charge transfer screening result in gate-tunable F4TCNQ HOMO-LUMO gaps. We further predict the ELA of a large system of experimental interest-4,4'-bis(dimethylamino)bipyridine (DMAP-OED) on monolayer MoS2, where charge transfer screening results in an ∼1 eV reduction of the molecular HOMO-LUMO gap. Comparison with a two-dimensional electron gas model reveals the importance of explicitly considering the intraband transitions in determining the charge transfer screening in organic-inorganic interface systems.
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Affiliation(s)
- Nicholas Lin Quan Cheng
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551 Singapore
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, 117546 Singapore
| | - Fengyuan Xuan
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, 117546 Singapore
| | - Catalin D Spataru
- Sandia National Laboratories, Livermore, California 94551, United States
| | - Su Ying Quek
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551 Singapore
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, 117546 Singapore
- NUS Graduate School Integrative Sciences and Engineering Programme, National University of Singapore, 117456 Singapore
- Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, 117575 Singapore
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14
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Zhou HJ, Xu DH, Yang QH, Liu XY, Cui G, Li L. Rational design of monolayer transition metal dichalcogenide@fullerene van der Waals photovoltaic heterojunctions with time-domain density functional theory simulations. Dalton Trans 2021; 50:6725-6734. [PMID: 33912883 DOI: 10.1039/d1dt00291k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
van der Waals heterojunctions formed by transition metal dichalcogenides (TMDs) and fullerenes are promising candidates for novel photovoltaic devices due to the excellent optoelectronic properties of both TMDs and fullerenes. However, relevant experimental and theoretical investigations remain scarce to the best of our knowledge. Herein, we have first employed static density functional theory (DFT) calculations in combination with time-domain density functional theory (TDDFT) based nonadiabatic dynamics simulations to rationally evaluate the photovoltaic performances of four TMD@fullerene heterostructures, i.e. WSe2@C60, WSe2@C70, MoTe2@C60 and MoTe2@C70, respectively. Our simulation results indicate that the C70-based heterostructures overall have better photoinduced electron transfer efficiencies than their C60-based counterparts, among which the performance of the WSe2@C70 heterostructure is the best and the electron transfer from WSe2 to C70 almost accomplishes within 1 ps. In addition, the large build-in potential of about 0.75 eV of WSe2@C70 is beneficial for the charge separation processes. Our present work not only selects the van der Waals TMD@fullerene heterojunctions that might have excellent photovoltaic properties, but also paves the way for the rational design of novel heterojunctions with better optoelectronic performances with DFT and TDDFT simulations in the future.
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Affiliation(s)
- Hong-Jun Zhou
- College of Chemistry and Material Science, Sichuan Normal University, Chengdu 610068, China.
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15
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Zhang Q, Huang Z, Hou Y, Yuan P, Xu Z, Yang H, Song X, Chen Y, Yang H, Zhang T, Liu L, Gao HJ, Wang Y. Tuning Molecular Superlattice by Charge-Density-Wave Patterns in Two-Dimensional Monolayer Crystals. J Phys Chem Lett 2021; 12:3545-3551. [PMID: 33818110 DOI: 10.1021/acs.jpclett.1c00230] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Charge density wave (CDW) in two-dimensional (2D) crystals plays a vital role in tuning the interface structures and properties. However, how the CDW tunes the self-assembled molecular superlattice still remains unclear. In this study, we investigated the self-assembled manganese phthalocyanine (MnPc) molecular superlattice on single-layered 1T- and 2H-NbSe2 crystals under regulation by distinct CDW patterns. We observe that, in low coverage, MnPc molecules preferentially adsorb on 2H-NbSe2 compared to 1T-NbSe2. With increasing coverage, MnPc can form a highly ordered superlattice on 2H-NbSe2; however, it is randomly distributed on 1T-NbSe2. We reveal a perfect geometric commensurability between the molecular superlattice and intrinsic CDW pattern in 2H-NbSe2 and a poor commensurability for that of 1T-NbSe2. We believe that the subtly different geometric commensurability dominates the different adsorption and arrangement of the molecular superlattices on 2D CDW patterns. Our study provides a pioneering approach for tuning the molecular superlattices using the CDW patterns.
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Affiliation(s)
- Quanzhen Zhang
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Zeping Huang
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Yanhui Hou
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Peiwen Yuan
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Ziqiang Xu
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Han Yang
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Xuan Song
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Yaoyao Chen
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Huixia Yang
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Teng Zhang
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Liwei Liu
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
| | - Hong-Jun Gao
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yeliang Wang
- MIIT Key Laboratory for Low-Dimensional Quantum Structure and Devices, School of Information and Electronics, Beijing Institute of Technology, Beijing 100081, China
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16
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Su J, Fan W, Mutombo P, Peng X, Song S, Ondráček M, Golub P, Brabec J, Veis L, Telychko M, Jelínek P, Wu J, Lu J. On-Surface Synthesis and Characterization of [7]Triangulene Quantum Ring. NANO LETTERS 2021; 21:861-867. [PMID: 33305570 DOI: 10.1021/acs.nanolett.0c04627] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The ability to engineer geometrically well-defined antidots in large triangulene homologues allows for creating an entire family of triangulene quantum rings (TQRs) with tunable high-spin ground state, crucial for next-generation molecular spintronic devices. Herein, we report the synthesis of an open-shell [7]triangulene quantum ring ([7]TQR) molecule on Au(111) through the surface-assisted cyclodehydrogenation of a rationally designed kekulene derivative. Bond-resolved scanning tunneling microscopy (BR-STM) unambiguously imaged the molecular backbone of a single [7]TQR with a triangular zigzag edge topology, which can be viewed as [7]triangulene decorated with a coronene-like antidot in the center. Additionally, dI/dV mapping reveals that both inner and outer zigzag edges contribute to the edge-localized and spin-polarized electronic states of [7]TQR. Both experimental results and spin-polarized density functional theory calculations indicate that [7]TQR retains its open-shell septuple ground state (S = 3) on Au(111). This work demonstrates a new route for the design of high-spin graphene quantum rings for future quantum devices.
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Affiliation(s)
- Jie Su
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Wei Fan
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Pingo Mutombo
- Institute of Physics, Czech Academy of Sciences, Prague 16200, Czech Republic
| | - Xinnan Peng
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Shaotang Song
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Martin Ondráček
- Institute of Physics, Czech Academy of Sciences, Prague 16200, Czech Republic
| | - Pavlo Golub
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, v.v.i., Dolejškova 3, 18223 Prague 8, Czech Republic
| | - Jiří Brabec
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, v.v.i., Dolejškova 3, 18223 Prague 8, Czech Republic
| | - Libor Veis
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, v.v.i., Dolejškova 3, 18223 Prague 8, Czech Republic
| | - Mykola Telychko
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Pavel Jelínek
- Institute of Physics, Czech Academy of Sciences, Prague 16200, Czech Republic
- Regional Centre of Advanced Technologies and Materials, Palacký University, Olomouc 78371, Czech Republic
| | - Jishan Wu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Jiong Lu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- Centre for Advanced 2D Materials (CA2DM), National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore
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17
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Xu R, Xuan F, Quek SY. Spin-Dependent Tunneling Barriers in CoPc/VSe 2 from Many-Body Interactions. J Phys Chem Lett 2020; 11:9358-9363. [PMID: 33091301 DOI: 10.1021/acs.jpclett.0c02944] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Mixed-dimensional magnetic heterostructures are intriguing, newly available platforms to explore quantum physics and its applications. Using state-of-the-art many-body perturbation theory, we predict the energy level alignment for a self-assembled monolayer of cobalt phthalocyanine (CoPc) molecules on magnetic VSe2 monolayers. The predicted projected density of states on CoPc agrees with experimental scanning tunneling spectra. Consistent with experiment, we predict a shoulder in the unoccupied region of the spectra that is absent from mean-field calculations. Unlike the nearly spin-degenerate gas-phase frontier molecular orbitals, the tunneling barriers at the interface are spin-dependent, a finding of interest for quantum information and spintronics applications. Both the experimentally observed shoulder and the predicted spin-dependent tunneling barriers originate from many-body interactions in the interface-hybridized states. Our results showcase the intricate many-body physics that governs the properties of these mixed-dimensional magnetic heterostructures and suggests the possibility of manipulating the spin-dependent tunneling barriers through modifications of interface coupling.
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Affiliation(s)
- Runrun Xu
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117542 Singapore
| | - Fengyuan Xuan
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, 117546 Singapore
| | - Su Ying Quek
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117542 Singapore
- Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, 117546 Singapore
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18
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Leng K, Wang L, Shao Y, Abdelwahab I, Grinblat G, Verzhbitskiy I, Li R, Cai Y, Chi X, Fu W, Song P, Rusydi A, Eda G, Maier SA, Loh KP. Electron tunneling at the molecularly thin 2D perovskite and graphene van der Waals interface. Nat Commun 2020; 11:5483. [PMID: 33127900 PMCID: PMC7599242 DOI: 10.1038/s41467-020-19331-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 10/07/2020] [Indexed: 11/17/2022] Open
Abstract
Quasi-two-dimensional perovskites have emerged as a new material platform for optoelectronics on account of its intrinsic stability. A major bottleneck to device performance is the high charge injection barrier caused by organic molecular layers on its basal plane, thus the best performing device currently relies on edge contact. Herein, by leveraging on van der Waals coupling and energy level matching between two-dimensional Ruddlesden-Popper perovskite and graphene, we show that the plane-contacted perovskite and graphene interface presents a lower barrier than gold for charge injection. Electron tunneling across the interface occurs via a gate-tunable, direct tunneling-to-field emission mechanism with increasing bias, and photoinduced charge transfer occurs at femtosecond timescale (~50 fs). Field effect transistors fabricated on molecularly thin Ruddlesden-Popper perovskite using graphene contact exhibit electron mobilities ranging from 0.1 to 0.018 cm2V−1s−1 between 1.7 to 200 K. Scanning tunneling spectroscopy studies reveal layer-dependent tunneling barrier and domain size on few-layered Ruddlesden-Popper perovskite. Insulating molecular layers on the basal plane of 2D perovskite is a major bottleneck for charge injection that limiting device performance. Here, the authors show that plane-contacted graphene functions as a low barrier and gate-tunable contact to overcome this limitation.
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Affiliation(s)
- Kai Leng
- Department of Chemistry, National University of Singapore, Singapore, Singapore.,Center for Advanced 2D Materials and Graphene Research Centre, Singapore, Singapore
| | - Lin Wang
- Department of Chemistry, National University of Singapore, Singapore, Singapore.,Center for Advanced 2D Materials and Graphene Research Centre, Singapore, Singapore
| | - Yan Shao
- Department of Chemistry, National University of Singapore, Singapore, Singapore
| | - Ibrahim Abdelwahab
- Department of Chemistry, National University of Singapore, Singapore, Singapore.,Center for Advanced 2D Materials and Graphene Research Centre, Singapore, Singapore.,Department of Physics, Imperial College London, London, SW7 2AZ, UK
| | - Gustavo Grinblat
- Nanoinstitute Munich, Faculty of Physics, Ludwig-Maximilians-Universität München, 80539, München, Germany
| | - Ivan Verzhbitskiy
- Center for Advanced 2D Materials and Graphene Research Centre, Singapore, Singapore.,Department of Physics, National University of Singapore, Singapore, Singapore
| | - Runlai Li
- Department of Chemistry, National University of Singapore, Singapore, Singapore
| | - Yongqing Cai
- Institute of Applied Physics and Materials Engineering, University of Macau, Macau, China
| | - Xiao Chi
- Department of Chemistry, National University of Singapore, Singapore, Singapore.,Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, 117603, Singapore, Singapore
| | - Wei Fu
- Department of Chemistry, National University of Singapore, Singapore, Singapore.,Center for Advanced 2D Materials and Graphene Research Centre, Singapore, Singapore
| | - Peng Song
- Department of Chemistry, National University of Singapore, Singapore, Singapore.,Center for Advanced 2D Materials and Graphene Research Centre, Singapore, Singapore
| | - Andrivo Rusydi
- Department of Physics, National University of Singapore, Singapore, Singapore.,Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, 117603, Singapore, Singapore
| | - Goki Eda
- Department of Chemistry, National University of Singapore, Singapore, Singapore.,Center for Advanced 2D Materials and Graphene Research Centre, Singapore, Singapore.,Department of Physics, National University of Singapore, Singapore, Singapore
| | - Stefan A Maier
- Department of Physics, Imperial College London, London, SW7 2AZ, UK.,Nanoinstitute Munich, Faculty of Physics, Ludwig-Maximilians-Universität München, 80539, München, Germany
| | - Kian Ping Loh
- Department of Chemistry, National University of Singapore, Singapore, Singapore. .,Center for Advanced 2D Materials and Graphene Research Centre, Singapore, Singapore.
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19
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Cheng CH, Cordovilla Leon D, Li Z, Litvak E, Deotare PB. Energy Transport of Hybrid Charge-Transfer Excitons. ACS NANO 2020; 14:10462-10470. [PMID: 32806037 DOI: 10.1021/acsnano.0c04367] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We investigate the energy transport in an organic-inorganic hybrid platform formed between semiconductors that support stable room-temperature excitons. We find that following photoexcitation, fast-moving hot hybrid charge-transfer excitons (HCTEs) are formed in about 36 ps via scattering with optical phonons at the interface between j-aggregates of organic dye and inorganic monolayer MoS2. Once the energy falls below the optical phonon energy, the excess kinetic energy is relaxed slowly via acoustic phonon scattering, resulting in energy transport that is dominated by fast-moving hot HCTEs that transition into cold HCTEs in about 110 ps. We model the exciton-phonon interactions using Fröhlich and deformation potential theory and attribute the prolonged transport of hot HCTEs to phonon bottleneck. We find that the measured diffusivity of HCTEs in both hot and cold regions of transport was higher than the diffusivity of MoS2 A exciton and verify these results by conducting the experiments with different excitation energies. This work not only provides significant insight into the initial energy transport of HCTEs at organic-inorganic hybrid interfaces but also contributes to the formulation of a complete physical picture of the energy dynamics in hybrid materials, which are poised to advance applications in energy conversion and optoelectronic devices.
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20
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Tan A, Zhang P. Tailoring the growth and electronic structures of organic molecular thin films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:503001. [PMID: 31422957 DOI: 10.1088/1361-648x/ab3c22] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
In the rapidly developing electronics industry, it has become increasingly necessary to explore materials that are cheap, flexible and versatile which have led to significant research efforts towards organic molecular thin films. Organic molecules are unique compared to their inorganic atomic counterparts as their properties can be tuned drastically through chemical functionalization, offering versatility, though their extended shape and weak intermolecular interactions bring significant challenges to the control of both the growth and the electronic structures of molecular thin films. In this paper, we will review the self-assembly process and how to establish long-range ordered organic molecular thin films. We will also discuss how the electronic structures of thin films are impacted by the molecule's local electrostatic environment and its interaction with the substrate, within the context of controlling interfacial energy level alignment between organic semiconductors and electrodes in electronic devices.
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Affiliation(s)
- Andrew Tan
- Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, United States of America
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21
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Tan A, Zhang PP. Interfacial charge transfer enhancement via formation of binary molecular assemblies on electronically corrugated boron nitride. Phys Chem Chem Phys 2019; 21:26146-26153. [PMID: 31750465 DOI: 10.1039/c9cp04853g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Using scanning tunneling microscopy/spectroscopy (STM/STS) in conjunction with finite element simulation, we investigate the interfacial behaviors in single-component zinc phthalocyanine (ZnPc) and hexadecafluorinated zinc phthalocyanine (F16ZnPc) molecular overlayers as well as their 1 : 1 mixed-phase superstructures on h-BN/Cu(111). We show that the formation of the binary molecular superstructure drastically increases the charge transfer between F16ZnPc molecules and the substrate, which is attributed to the greater electrostatic stability of the binary assembly compared to that of the pure phase. This study highlights the significant complication in the design of donor-acceptor molecular thin films as the presence of the substrate, even a weakly interacting one, such as h-BN/metal, can still perturb the intermolecular charge transfer and thereby the physical behaviors of the hybrid system via interfacial processes.
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Affiliation(s)
- A Tan
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824-2320, USA.
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22
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Xie XY, Liu XY, Fang Q, Fang WH, Cui G. Photoinduced Carrier Dynamics at the Interface of Pentacene and Molybdenum Disulfide. J Phys Chem A 2019; 123:7693-7703. [PMID: 31419385 DOI: 10.1021/acs.jpca.9b04728] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Understanding of photoinduced interfacial carrier dynamics in organic-transition metal dichalcogenides heterostructures is very important for the enhancement of their potential photoelectronic conversion efficiencies. In this work we have used density functional theory (DFT) calculations and DFT-based fewest-switches surface-hopping dynamics simulations to explore the photoinduced hole transfer and subsequent nonadiabatic electron-hole recombination dynamics taking place at the interface of pentacene and MoS2 in pentacene@MoS2. Upon photoexcitation the electronic transition mainly occurs on the MoS2 monolayer, which corresponds to moving an electron to the MoS2 conduction band. As a result, a hole is left in the valence band. This hole state is energetically lower than certain occupied states of the pentacene molecule; thus, the interfacial hole transfer from MoS2 to pentacene is favorable in energy. In terms of nonadiabatic dynamics simulations, the hole transfer time to the HOMO-1 state of the pentacene is estimated to be about 600 fs; however, the following hole relaxation process from HOMO-1 to HOMO takes much longer time of ca. 15 ps due to the large energy gap between HOMO-1 and HOMO. Moreover, our results also show that the subsequent radiationless recombination process between the hole transferred to the pentacene molecule and the remaining electron on the MoS2 CBM needs about 10.2 ns. The computational results shed important mechanistic insights on the interfacial carrier dynamics of mixed-dimensional pentacene@MoS2. These insights could help to design excellent interfaces for organic-TMDs heterostructures.
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Affiliation(s)
- Xiao-Ying Xie
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry , Beijing Normal University , Beijing 100875 , China
| | - Xiang-Yang Liu
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry , Beijing Normal University , Beijing 100875 , China
| | - Qiu Fang
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry , Beijing Normal University , Beijing 100875 , China
| | - Wei-Hai Fang
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry , Beijing Normal University , Beijing 100875 , China
| | - Ganglong Cui
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry , Beijing Normal University , Beijing 100875 , China
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23
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Liu Z, Sun K, Li X, Li L, Zhang H, Chi L. Electronic Decoupling of Organic Layers by a Self-Assembled Supramolecular Network on Au(111). J Phys Chem Lett 2019; 10:4297-4302. [PMID: 31318568 DOI: 10.1021/acs.jpclett.9b01167] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
A cyanuric acid and melamine (CA·M) supramolecular network, prepared via the drop-casting method under ambient conditions, can be utilized as a spacer layer to decouple electronic interactions between upper organics and the metal substrate. Typical semiconducting organics 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) and C60 are deposited on the CA·M network under ultrahigh vacuum conditions, forming an organics/CA·M/metal heterosystem. Both geometric and electronic structures of the upper organics are characterized by using scanning tunneling microscopy/spectroscopy (STM/STS). On the CA·M network, PTCDA molecules form a well-ordered herringbone structure in submonolayer patterns, whereas C60 molecules aggregate into multilayered islands. STS spectra reveal that the energy gap between the highest occupied and the lowest unoccupied molecular orbitals (HOMO - LUMO) is 3.6 eV for PTCDA and 3.8 eV for the first layer of C60 on CA·M. The remarkable bandgap broadening compared with the metal-organic contact indicates successful electronic decoupling of the upper molecules from the metal surface due to the CA·M network.
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Affiliation(s)
- Zhonghua Liu
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices , Soochow University , 199 Ren'ai Road , Suzhou , 215123 , Jiangsu , PR China
| | - Kewei Sun
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices , Soochow University , 199 Ren'ai Road , Suzhou , 215123 , Jiangsu , PR China
| | - Xuechao Li
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices , Soochow University , 199 Ren'ai Road , Suzhou , 215123 , Jiangsu , PR China
| | - Ling Li
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices , Soochow University , 199 Ren'ai Road , Suzhou , 215123 , Jiangsu , PR China
| | - Haiming Zhang
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices , Soochow University , 199 Ren'ai Road , Suzhou , 215123 , Jiangsu , PR China
| | - Lifeng Chi
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices , Soochow University , 199 Ren'ai Road , Suzhou , 215123 , Jiangsu , PR China
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24
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Su J, Telychko M, Hu P, Macam G, Mutombo P, Zhang H, Bao Y, Cheng F, Huang ZQ, Qiu Z, Tan SJR, Lin H, Jelínek P, Chuang FC, Wu J, Lu J. Atomically precise bottom-up synthesis of π-extended [5]triangulene. SCIENCE ADVANCES 2019; 5:eaav7717. [PMID: 31360763 PMCID: PMC6660211 DOI: 10.1126/sciadv.aav7717] [Citation(s) in RCA: 112] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Accepted: 06/20/2019] [Indexed: 05/10/2023]
Abstract
The zigzag-edged triangular graphene molecules (ZTGMs) have been predicted to host ferromagnetically coupled edge states with the net spin scaling with the molecular size, which affords large spin tunability crucial for next-generation molecular spintronics. However, the scalable synthesis of large ZTGMs and the direct observation of their edge states have been long-standing challenges because of the molecules' high chemical instability. Here, we report the bottom-up synthesis of π-extended [5]triangulene with atomic precision via surface-assisted cyclodehydrogenation of a rationally designed molecular precursor on metallic surfaces. Atomic force microscopy measurements unambiguously resolve its ZTGM-like skeleton consisting of 15 fused benzene rings, while scanning tunneling spectroscopy measurements reveal edge-localized electronic states. Bolstered by density functional theory calculations, our results show that [5]triangulenes synthesized on Au(111) retain the open-shell π-conjugated character with magnetic ground states.
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Affiliation(s)
- Jie Su
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- Centre for Advanced 2D Materials (CA2DM), National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore
| | - Mykola Telychko
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- Centre for Advanced 2D Materials (CA2DM), National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore
| | - Pan Hu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Gennevieve Macam
- Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
| | - Pingo Mutombo
- Institute of Physics, The Czech Academy of Sciences, Prague 16200, Czech Republic
| | - Hejian Zhang
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Yang Bao
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- Centre for Advanced 2D Materials (CA2DM), National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore
| | - Fang Cheng
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- Centre for Advanced 2D Materials (CA2DM), National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore
| | - Zhi-Quan Huang
- Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
| | - Zhizhan Qiu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, 28 Medical Drive, Singapore 117456, Singapore
| | - Sherman J. R. Tan
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, 28 Medical Drive, Singapore 117456, Singapore
| | - Hsin Lin
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Pavel Jelínek
- Institute of Physics, The Czech Academy of Sciences, Prague 16200, Czech Republic
- Regional Centre of Advanced Technologies and Materials, Palacký University, Olomouc 78371, Czech Republic
| | - Feng-Chuan Chuang
- Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
| | - Jishan Wu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Jiong Lu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
- Centre for Advanced 2D Materials (CA2DM), National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore
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25
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Liu ZF, da Jornada FH, Louie SG, Neaton JB. Accelerating GW-Based Energy Level Alignment Calculations for Molecule-Metal Interfaces Using a Substrate Screening Approach. J Chem Theory Comput 2019; 15:4218-4227. [PMID: 31194538 DOI: 10.1021/acs.jctc.9b00326] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The physics of electronic energy level alignment at interfaces formed between molecules and metals can in general be accurately captured by the ab initio GW approach. However, the computational cost of such GW calculations for typical interfaces is significant, given their large system size and chemical complexity. In the past, approximate self-energy corrections, such as those constructed from image-charge models together with gas-phase molecular level corrections, have been used to compute level alignment with good accuracy. However, these approaches often neglect dynamical effects of the polarizability and require the definition of an image plane. In this work, we propose a new approximation to enable more efficient GW-quality calculations of interfaces, where we greatly simplify the calculation of the noninteracting polarizability, a primary bottleneck for large heterogeneous systems. This is achieved by first computing the noninteracting polarizability of each individual component of the interface, e.g., the molecule and the metal, without the use of large supercells, and then using folding and spatial truncation techniques to efficiently combine these quantities. Overall this approach significantly reduces the computational cost for conventional GW calculations of level alignment without sacrificing the accuracy. Moreover, this approach captures both dynamical and nonlocal polarization effects without the need to invoke a classical image-charge expression or to define an image plane. We demonstrate our approach by considering a model system of benzene at relatively low coverage on the aluminum (111) surface. Although developed for such interfaces, the method can be readily extended to other heterogeneous interfaces.
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Affiliation(s)
- Zhen-Fei Liu
- Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.,Department of Physics , University of California , Berkeley , California 94720 , United States
| | - Felipe H da Jornada
- Department of Physics , University of California , Berkeley , California 94720 , United States.,Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Steven G Louie
- Department of Physics , University of California , Berkeley , California 94720 , United States.,Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Jeffrey B Neaton
- Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.,Department of Physics , University of California , Berkeley , California 94720 , United States.,Kavli Energy Nanosciences Institute at Berkeley , Berkeley , California 94720 , United States
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26
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Xuan F, Chen Y, Quek SY. Quasiparticle Levels at Large Interface Systems from Many-Body Perturbation Theory: The XAF-GW Method. J Chem Theory Comput 2019; 15:3824-3835. [PMID: 31084031 DOI: 10.1021/acs.jctc.9b00229] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
We present a fully ab initio approach based on many-body perturbation theory in the GW approximation to compute the quasiparticle levels of large interface systems without significant covalent interactions between the different components of the interface (meaning that the different components can be separated without the creation of dangling bonds). The only assumption in our approach is that the polarizability matrix (chi) of the interface can be given by the sum of the polarizability matrices of individual components of the interface. We show analytically, using a two-state hybridized model, that this assumption is valid even in the presence of interface hybridization to form bonding and antibonding states up to first order in the overlap matrix elements involved in the hybridization. We validate our approach by showing that the band structure obtained in our method is almost identical to that obtained using a regular GW calculation for bilayer black phosphorus, where interlayer hybridization is significant. Significant savings in computational time and memory are obtained by computing chi only for the smallest subunit cell of each component and expanding (unfolding) the chi matrix to that in the unit cell of the interface. To treat interface hybridization, the full wave functions of the interface are used in computing the self-energy. We thus call the method XAF-GW (X, eXpand-chi; A, Add-chi; F, Full wave functions). Compared to GW-embedding type approaches in the literature, the XAF-GW approach is not limited to specific screening environments or to nonhybridized interface systems. XAF-GW can also be applied to systems with different dimensionalities, as well as to Moire superlattices such as in twisted bilayers. We illustrate the generality and usefulness of our approach by applying it to self-assembled PTCDA monolayers on Au(111) and Ag(111) and PTCDA monolayers on graphite-supported monolayer WSe2. In all cases, the predicted HOMO and LUMO levels agree well with experimental measurements.
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Affiliation(s)
- Fengyuan Xuan
- Centre for Advanced 2D Materials , National University of Singapore , Block S14, Level 6, 6 Science Drive 2 , Singapore 117546 , Singapore
| | - Yifeng Chen
- Centre for Advanced 2D Materials , National University of Singapore , Block S14, Level 6, 6 Science Drive 2 , Singapore 117546 , Singapore
| | - Su Ying Quek
- Centre for Advanced 2D Materials , National University of Singapore , Block S14, Level 6, 6 Science Drive 2 , Singapore 117546 , Singapore.,Department of Physics , National University of Singapore , 2 Science Drive 3 , Singapore 117542 , Singapore
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27
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Liu XY, Chen WK, Fang WH, Cui G. Nonadiabatic Dynamics Simulations Reveal Distinct Effects of the Thickness of PTB7 on Interfacial Electron and Hole Transfer Dynamics in PTB7@MoS 2 Heterostructures. J Phys Chem Lett 2019; 10:2949-2956. [PMID: 31083919 DOI: 10.1021/acs.jpclett.9b01066] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Mixed-dimensional hybrid heterostructures have attracted a lot of experimental attention because they can provide an ideal charge-separated interface for optoelectronic and photonic applications. In this Letter, we have employed first-principles DFT calculations and nonadiabatic dynamics simulations to explore photoinduced interfacial electron and hole transfer processes in two PTB7- nL@MoS2 models ( n = 1 and 5). The interfacial electron transfer is found to be ultrafast and completes within ca. 10 fs in both PTB7-1L@MoS2 and PTB7-5L@MoS2 models, which demonstrates that the electron transfer is not sensitive to the thickness of the PTB7 polymer. Differently, the interfacial hole transfer is sensitive to the thickness of the PTB7 polymer. The transfer time is estimated to be ca. 70 ps in PTB7-1L@MoS2, while it is significantly accelerated to ca. 1 ps in PTB7-5L@MoS2. Finally, we have found that the electron transfer is mainly controlled by adiabatic electron evolution, whereas in the hole transfer, nonadiabatic hoppings play a dominant role. These findings are useful for the design of excellent charge-separated interfaces of mixed-dimensional TMD-based heterojunctions for a variety of optoelectronic applications.
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Affiliation(s)
- Xiang-Yang Liu
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry , Beijing Normal University , Beijing 100875 , China
| | - Wen-Kai Chen
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry , Beijing Normal University , Beijing 100875 , China
| | - Wei-Hai Fang
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry , Beijing Normal University , Beijing 100875 , China
| | - Ganglong Cui
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry , Beijing Normal University , Beijing 100875 , China
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28
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Liu XY, Xie XY, Fang WH, Cui G. Theoretical Insights into Interfacial Electron Transfer between Zinc Phthalocyanine and Molybdenum Disulfide. J Phys Chem A 2018; 122:9587-9596. [DOI: 10.1021/acs.jpca.8b07816] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Xiang-Yang Liu
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Xiao-Ying Xie
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Wei-Hai Fang
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Ganglong Cui
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
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29
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Cheng CH, Li Z, Hambarde A, Deotare PB. Efficient Energy Transfer across Organic-2D Inorganic Heterointerfaces. ACS APPLIED MATERIALS & INTERFACES 2018; 10:39336-39342. [PMID: 30339346 DOI: 10.1021/acsami.8b12291] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Combining organic and inorganic semiconductors enables us to integrate complementary advantages of each material system into a single hybrid material platform. Here, we report a study on the energy transport across a hybrid interface consisting of j-aggregates of organic dye and monolayer molybdenum disulfide (MoS2). The excellent overlap between the photoluminescence spectra of j-aggregates and the absorption of MoS2 B-exciton enables the material system to be used to study Förster resonance energy transfer (FRET) across the hybrid interface. We report a short Förster radius of 1.88 nm for the hybrid system. We achieve this by fabricating photodetectors based on the hybrid organic-inorganic interface that combine the high absorption of organics with the high-charge mobility of inorganics. Concomitantly, the hybrid photodetectors show nearly 93 ± 5% enhancement of photoresponsivity in the excitonic spectral overlap regime due to efficient energy transfer (ET) from j-aggregate to MoS2. This work not only provides valuable insight into the ET mechanism across such hybrid organic-inorganic interfaces but also demonstrates the feasibility of the platform for designing efficient energy conversion and optoelectronic devices.
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30
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Liu X, Hersam MC. Interface Characterization and Control of 2D Materials and Heterostructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1801586. [PMID: 30039558 DOI: 10.1002/adma.201801586] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Revised: 04/09/2018] [Indexed: 05/28/2023]
Abstract
2D materials and heterostructures have attracted significant attention for a variety of nanoelectronic and optoelectronic applications. At the atomically thin limit, the material characteristics and functionalities are dominated by surface chemistry and interface coupling. Therefore, methods for comprehensively characterizing and precisely controlling surfaces and interfaces are required to realize the full technological potential of 2D materials. Here, the surface and interface properties that govern the performance of 2D materials are introduced. Then the experimental approaches that resolve surface and interface phenomena down to the atomic scale, as well as strategies that allow tuning and optimization of interfacial interactions in van der Waals heterostructures, are systematically reviewed. Finally, a future outlook that delineates the remaining challenges and opportunities for 2D material interface characterization and control is presented.
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Affiliation(s)
- Xiaolong Liu
- Applied Physics Graduate Program, Northwestern University, 2220 Campus Drive, Evanston, IL, 60208-3108, USA
| | - Mark C Hersam
- Applied Physics Graduate Program, Northwestern University, 2220 Campus Drive, Evanston, IL, 60208-3108, USA
- Department of Materials Science and Engineering, Department of Chemistry, Department of Medicine, Department of Electrical Engineering and Computer Science, Northwestern University, 2220 Campus Drive, Evanston, IL, 60208-3108, USA
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31
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Huang YL, Zheng YJ, Song Z, Chi D, Wee ATS, Quek SY. The organic-2D transition metal dichalcogenide heterointerface. Chem Soc Rev 2018; 47:3241-3264. [PMID: 29651487 DOI: 10.1039/c8cs00159f] [Citation(s) in RCA: 79] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Since the first isolation of graphene, new classes of two-dimensional (2D) materials have offered fascinating platforms for fundamental science and technology explorations at the nanometer scale. In particular, 2D transition metal dichalcogenides (TMD) such as MoS2 and WSe2 have been intensely investigated due to their unique electronic and optical properties, including tunable optical bandgaps, direct-indirect bandgap crossover, strong spin-orbit coupling, etc., for next-generation flexible nanoelectronics and nanophotonics applications. On the other hand, organics have always been excellent materials for flexible electronics. A plethora of organic molecules, including donors, acceptors, and photosensitive molecules, can be synthesized using low cost and scalable procedures. Marrying the fields of organics and 2D TMDs will bring benefits that are not present in either material alone, enabling even better, multifunctional flexible devices. Central to the realization of such devices is a fundamental understanding of the organic-2D TMD interface. Here, we review the organic-2D TMD interface from both chemical and physical perspectives. We discuss the current understanding of the interfacial interactions between the organic layers and the TMDs, as well as the energy level alignment at the interface, focusing in particular on surface charge transfer and electronic screening effects. Applications from the literature are discussed, especially in optoelectronics and p-n hetero- and homo-junctions. We conclude with an outlook on future scientific and device developments based on organic-2D TMD heterointerfaces.
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Affiliation(s)
- Yu Li Huang
- Institute of Materials Research & Engineering (IMRE), A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore.
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32
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Gobbi M, Orgiu E, Samorì P. When 2D Materials Meet Molecules: Opportunities and Challenges of Hybrid Organic/Inorganic van der Waals Heterostructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1706103. [PMID: 29441680 DOI: 10.1002/adma.201706103] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 11/16/2017] [Indexed: 05/21/2023]
Abstract
van der Waals heterostructures, composed of vertically stacked inorganic 2D materials, represent an ideal platform to demonstrate novel device architectures and to fabricate on-demand materials. The incorporation of organic molecules within these systems holds an immense potential, since, while nature offers a finite number of 2D materials, an almost unlimited variety of molecules can be designed and synthesized with predictable functionalities. The possibilities offered by systems in which continuous molecular layers are interfaced with inorganic 2D materials to form hybrid organic/inorganic van der Waals heterostructures are emphasized. Similar to their inorganic counterpart, the hybrid structures have been exploited to put forward novel device architectures, such as antiambipolar transistors and barristors. Moreover, specific molecular groups can be employed to modify intrinsic properties and confer new capabilities to 2D materials. In particular, it is highlighted how molecular self-assembly at the surface of 2D materials can be mastered to achieve precise control over position and density of (molecular) functional groups, paving the way for a new class of hybrid functional materials whose final properties can be selected by careful molecular design.
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Affiliation(s)
- Marco Gobbi
- University of Strasbourg, CNRS, ISIS UMR 7006, 8 Allée Gaspard Monge, F-67000, Strasbourg, France
| | - Emanuele Orgiu
- University of Strasbourg, CNRS, ISIS UMR 7006, 8 Allée Gaspard Monge, F-67000, Strasbourg, France
| | - Paolo Samorì
- University of Strasbourg, CNRS, ISIS UMR 7006, 8 Allée Gaspard Monge, F-67000, Strasbourg, France
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33
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Cui X, Troadec C, Wee ATS, Huang YL. Surface Nanostructure Formation and Atomic-Scale Templates for Nanodevices. ACS OMEGA 2018; 3:3285-3293. [PMID: 31458585 PMCID: PMC6641249 DOI: 10.1021/acsomega.8b00014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 02/09/2018] [Indexed: 05/20/2023]
Abstract
The holy grail in nanoelectronics is the construction of nanodevices with high density, low cost, and high performance per device and per integrated circuit. One approach is the fabrication of surface nanostructures and atomic-scale templates via the autonomous assembly of atoms and/or molecules on well-defined surfaces. To steer the atomic or molecular growth processes and create a wide range of surface nanostructures with desired properties, a comprehensive understanding of the mechanisms that control the surface self-assembly processes is required. The capability to manipulate the nanodevices at the submolecular level with good controllability is also of paramount importance. This review highlights some key recent developments in the fabrication of low-dimensional nanostructures based on supramolecular self-assembly on predefined surfaces, with particular emphasis on the rapidly expanding field of two-dimensional materials. Special attention is also given to the latest progress in single-molecule manipulation for future device applications.
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Affiliation(s)
- Xiaoyang Cui
- Institute
of Materials Research & Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore
- Department
of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
| | - Cedric Troadec
- Institute
of Materials Research & Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore
| | - Andrew T. S. Wee
- Institute
of Materials Research & Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore
- Department
of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
- E-mail: (A.T.S.W.)
| | - Yu Li Huang
- Institute
of Materials Research & Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore
- Department
of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
- E-mail: (Y.L.H.)
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34
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Wang Z, Dong Z, Zhu H, Jin L, Chiu MH, Li LJ, Xu QH, Eda G, Maier SA, Wee ATS, Qiu CW, Yang JKW. Selectively Plasmon-Enhanced Second-Harmonic Generation from Monolayer Tungsten Diselenide on Flexible Substrates. ACS NANO 2018; 12:1859-1867. [PMID: 29301073 DOI: 10.1021/acsnano.7b08682] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Monolayer two-dimensional transition-metal dichalcogenides (2D TMDCs) exhibit promising characteristics in miniaturized nonlinear optical frequency converters, due to their inversion asymmetry and large second-order nonlinear susceptibility. However, these materials usually have very short light interaction lengths with the pump laser because they are atomically thin, such that second-harmonic generation (SHG) is generally inefficient. In this paper, we fabricate a judiciously structured 150 nm-thick planar surface consisting of monolayer tungsten diselenide and sub-20 nm-wide gold trenches on flexible substrates, reporting ∼7000-fold SHG enhancement without peak broadening or background in the spectra as compared to WSe2 on as-grown sapphire substrates. Our proof-of-concept experiment yields effective second-order nonlinear susceptibility of 2.1 × 104 pm/V. Three orders of magnitude enhancement is maintained with pump wavelength ranging from 800 to 900 nm, breaking the limitation of narrow pump wavelength range for cavity-enhanced SHG. In addition, SHG amplitude can be dynamically controlled via selective excitation of the lateral gap plasmon by rotating the laser polarization. Such a fully open, flat, and ultrathin profile enables a great variety of functional samples with high SHG from one patterned silicon substrate, favoring scalable production of nonlinear converters. The surface accessibility also enables integration with other optical components for information processing in an ultrathin and flexible form.
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Affiliation(s)
- Zhuo Wang
- NUS Graduate School for Integrative Sciences and Engineering (NGS), National University of Singapore , 28 Medical Drive, Singapore117456, Singapore
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117542, Singapore
- Department of Physics, Imperial College London , London SW7 2AZ, United Kingdom
| | - Zhaogang Dong
- Institute of Materials Research and Engineering, Agency for Science, Technology, and Research (A*STAR) , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634, Singapore
| | - Hai Zhu
- Department of Chemistry, National University of Singapore , 3 Science Drive 3, Singapore 117543, Singapore
| | - Lei Jin
- Department of Electrical and Computer Engineering, National University of Singapore , 4 Engineering Drive 3, Singapore 117583, Singapore
| | - Ming-Hui Chiu
- Physical Science and Engineering Division, King Abdullah University of Science and Technology , Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Lain-Jong Li
- Physical Science and Engineering Division, King Abdullah University of Science and Technology , Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Qing-Hua Xu
- Department of Chemistry, National University of Singapore , 3 Science Drive 3, Singapore 117543, Singapore
| | - Goki Eda
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117542, Singapore
- Department of Chemistry, National University of Singapore , 3 Science Drive 3, Singapore 117543, Singapore
- Centre for Advanced 2D Materials, National University of Singapore , 2 Science Drive 3, Singapore 117542, Singapore
| | - Stefan A Maier
- Department of Physics, Imperial College London , London SW7 2AZ, United Kingdom
- Chair in Hybrid Nanosystems, Faculty of Physics, Ludwig-Maximilians-Universität München , Munich 80799, Germany
| | - Andrew T S Wee
- NUS Graduate School for Integrative Sciences and Engineering (NGS), National University of Singapore , 28 Medical Drive, Singapore117456, Singapore
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117542, Singapore
- Centre for Advanced 2D Materials, National University of Singapore , 2 Science Drive 3, Singapore 117542, Singapore
| | - Cheng-Wei Qiu
- NUS Graduate School for Integrative Sciences and Engineering (NGS), National University of Singapore , 28 Medical Drive, Singapore117456, Singapore
- Department of Electrical and Computer Engineering, National University of Singapore , 4 Engineering Drive 3, Singapore 117583, Singapore
- Centre for Advanced 2D Materials, National University of Singapore , 2 Science Drive 3, Singapore 117542, Singapore
| | - Joel K W Yang
- Institute of Materials Research and Engineering, Agency for Science, Technology, and Research (A*STAR) , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634, Singapore
- Singapore University of Technology and Design , 8 Somapah Road, Singapore 487372, Singapore
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35
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Morteza Najarian A, Bayat A, McCreery RL. Orbital Control of Photocurrents in Large Area All-Carbon Molecular Junctions. J Am Chem Soc 2018; 140:1900-1909. [DOI: 10.1021/jacs.7b12577] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Amin Morteza Najarian
- Department
of Chemistry, University of Alberta, Edmonton, Alberta, Canada, T6G 2R3
- National
Institute for Nanotechnology, National Research Council Canada, Edmonton, Alberta, Canada, T6G 2G2
| | - Akhtar Bayat
- Department
of Chemistry, University of Alberta, Edmonton, Alberta, Canada, T6G 2R3
- National
Institute for Nanotechnology, National Research Council Canada, Edmonton, Alberta, Canada, T6G 2G2
| | - Richard L. McCreery
- Department
of Chemistry, University of Alberta, Edmonton, Alberta, Canada, T6G 2R3
- National
Institute for Nanotechnology, National Research Council Canada, Edmonton, Alberta, Canada, T6G 2G2
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36
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Yang F, Cheng S, Zhang X, Ren X, Li R, Dong H, Hu W. 2D Organic Materials for Optoelectronic Applications. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:1702415. [PMID: 29024065 DOI: 10.1002/adma.201702415] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Revised: 07/15/2017] [Indexed: 06/07/2023]
Abstract
The remarkable merits of 2D materials with atomically thin structures and optoelectronic attributes have inspired great interest in integrating 2D materials into electronics and optoelectronics. Moreover, as an emerging field in the 2D-materials family, assembly of organic nanostructures into 2D forms offers the advantages of molecular diversity, intrinsic flexibility, ease of processing, light weight, and so on, providing an exciting prospect for optoelectronic applications. Herein, the applications of organic 2D materials for optoelectronic devices are a main focus. Material examples include 2D, organic, crystalline, small molecules, polymers, self-assembly monolayers, and covalent organic frameworks. The protocols for 2D-organic-crystal-fabrication and -patterning techniques are briefly discussed, then applications in optoelectronic devices are introduced in detail. Overall, an introduction to what is known and suggestions for the potential of many exciting developments are presented.
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Affiliation(s)
- Fangxu Yang
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences Department of Chemistry, School of Sciences, Tianjin University, & Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, 300072, China
| | - Shanshan Cheng
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences Department of Chemistry, School of Sciences, Tianjin University, & Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, 300072, China
| | - Xiaotao Zhang
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences Department of Chemistry, School of Sciences, Tianjin University, & Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, 300072, China
| | - Xiaochen Ren
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences Department of Chemistry, School of Sciences, Tianjin University, & Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, 300072, China
| | - Rongjin Li
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences Department of Chemistry, School of Sciences, Tianjin University, & Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, 300072, China
| | - Huanli Dong
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
| | - Wenping Hu
- Tianjin Key Laboratory of Molecular Optoelectronic Sciences Department of Chemistry, School of Sciences, Tianjin University, & Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, 300072, China
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China
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37
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Zhang S, Zhang N, Zhao Y, Cheng T, Li X, Feng R, Xu H, Liu Z, Zhang J, Tong L. Spotting the differences in two-dimensional materials – the Raman scattering perspective. Chem Soc Rev 2018; 47:3217-3240. [DOI: 10.1039/c7cs00874k] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This review discusses the Raman spectroscopic characterization of 2D materials with a focus on the “differences” from primitive 2D materials.
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38
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Zhao Y, Li Q, Shi L, Wang J. Exploitation of the Large-Area Basal Plane of MoS 2 and Preparation of Bifunctional Catalysts through On-Surface Self-Assembly. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2017; 4:1700356. [PMID: 29270345 PMCID: PMC5737238 DOI: 10.1002/advs.201700356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2017] [Revised: 08/06/2017] [Indexed: 05/15/2023]
Abstract
The development of nonprecious electrochemical catalysts for water splitting is a key step to achieve a sustainable energy supply for the future. Molybdenum disulfide (MoS2) has been extensively studied as a promising low-cost catalyst for hydrogen evolution reaction (HER), whereas HER is only catalyzed at the edge for pristine MoS2, leaving a large area of basal plane useless. Herein, on-surface self-assembly is demonstrated to be an effective, facile, and damage-free method to take full advantage of the large ratio surface of MoS2 for HER by using multiscale simulations. It is found that as supplement of edge sites of MoS2, on-MoS2 M(abt)2 (M = Ni, Co; abt = 2-aminobenzenethiolate) owns high HER activity, and the self-assembled M(abt)2 monolayers on MoS2 can be obtained through a simple liquid-deposition method. More importantly, on-surface self-assembly provides potential application for overall water splitting once the self-assembled systems prove to be of both HER and oxygen evolution reaction activities, for example, on-MoS2 Co(abt)2. This work opens up a new and promising avenue (on-surface self-assembly) toward the full exploitation of the basal plane of MoS2 for HER and the preparation of bifunctional catalysts for overall water splitting.
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Affiliation(s)
- Yinghe Zhao
- School of PhysicsSoutheast UniversityNanjing211189China
| | - Qiang Li
- School of PhysicsSoutheast UniversityNanjing211189China
| | - Li Shi
- School of PhysicsSoutheast UniversityNanjing211189China
| | - Jinlan Wang
- School of PhysicsSoutheast UniversityNanjing211189China
- Synergetic Innovation Center for Quantum Effects and Applications (SICQEA)Hunan Normal UniversityChangsha410081China
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39
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Kafle TR, Kattel B, Lane SD, Wang T, Zhao H, Chan WL. Charge Transfer Exciton and Spin Flipping at Organic-Transition-Metal Dichalcogenide Interfaces. ACS NANO 2017; 11:10184-10192. [PMID: 28985468 DOI: 10.1021/acsnano.7b04751] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Two-dimensional transition-metal dichalcogenides (TMD) can be combined with other materials such as organic small molecules to form hybrid van der Waals heterostructures. Because of different properties possessed by these two materials, the hybrid interface can exhibit properties that cannot be found in either of the materials. In this work, the zinc phthalocyanine (ZnPc)-molybdenum disulfide (MoS2) interface is used as a model system to study the charge transfer at these interfaces. It is found that the optically excited singlet exciton in ZnPc transfers its electron to MoS2 in 80 fs after photoexcitation to form a charge transfer exciton. However, back electron transfer occurs on the time scale of ∼1-100 ps, which results in the formation of a triplet exciton in the ZnPc layer. This relatively fast singlet-triplet transition is feasible because of the large singlet-triplet splitting in organic materials and the strong spin-orbit coupling in TMD crystals. The back electron transfer would reduce the yield of free carrier generation at the heterojunction if it is not avoided. On the other hand, the spin-selective back electron transfer could be used to manipulate electron spin in hybrid electronic devices.
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Affiliation(s)
- Tika R Kafle
- Department of Physics and Astronomy, University of Kansas , Lawrence, Kansas 66045, United States
| | - Bhupal Kattel
- Department of Physics and Astronomy, University of Kansas , Lawrence, Kansas 66045, United States
| | - Samuel D Lane
- Department of Physics and Astronomy, University of Kansas , Lawrence, Kansas 66045, United States
| | - Ti Wang
- Department of Physics and Astronomy, University of Kansas , Lawrence, Kansas 66045, United States
| | - Hui Zhao
- Department of Physics and Astronomy, University of Kansas , Lawrence, Kansas 66045, United States
| | - Wai-Lun Chan
- Department of Physics and Astronomy, University of Kansas , Lawrence, Kansas 66045, United States
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40
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Song Z, Schultz T, Ding Z, Lei B, Han C, Amsalem P, Lin T, Chi D, Wong SL, Zheng YJ, Li MY, Li LJ, Chen W, Koch N, Huang YL, Wee ATS. Electronic Properties of a 1D Intrinsic/p-Doped Heterojunction in a 2D Transition Metal Dichalcogenide Semiconductor. ACS NANO 2017; 11:9128-9135. [PMID: 28753270 DOI: 10.1021/acsnano.7b03953] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Two-dimensional (2D) semiconductors offer a convenient platform to study 2D physics, for example, to understand doping in an atomically thin semiconductor. Here, we demonstrate the fabrication and unravel the electronic properties of a lateral doped/intrinsic heterojunction in a single-layer (SL) tungsten diselenide (WSe2), a prototype semiconducting transition metal dichalcogenide (TMD), partially covered with a molecular acceptor layer, on a graphite substrate. With combined experiments and theoretical modeling, we reveal the fundamental acceptor-induced p-doping mechanism for SL-WSe2. At the 1D border between the doped and undoped SL-WSe2 regions, we observe band bending and explain it by Thomas-Fermi screening. Using atomically resolved scanning tunneling microscopy and spectroscopy, the screening length is determined to be in the few nanometer range, and we assess the carrier density of intrinsic SL-WSe2. These findings are of fundamental and technological importance for understanding and employing surface doping, for example, in designing lateral organic TMD heterostructures for future devices.
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Affiliation(s)
- Zhibo Song
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117542
- Institute of Materials Research & Engineering (IMRE), A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, Singapore 138634
| | - Thorsten Schultz
- Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin , Brook-Taylor Straße 6, 12489 Berlin, Germany
| | - Zijing Ding
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117542
- SZU-NUS Collaborative Innovation Center for Optoelectronic Science & Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Shenzhen University , Shenzhen 518060, China
| | - Bo Lei
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117542
| | - Cheng Han
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117542
- SZU-NUS Collaborative Innovation Center for Optoelectronic Science & Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Shenzhen University , Shenzhen 518060, China
- Department of Chemistry, National University of Singapore , 2 Science Drive 3, Singapore 117542
| | - Patrick Amsalem
- Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin , Brook-Taylor Straße 6, 12489 Berlin, Germany
| | - Tingting Lin
- Institute of Materials Research & Engineering (IMRE), A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, Singapore 138634
| | - Dongzhi Chi
- Institute of Materials Research & Engineering (IMRE), A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, Singapore 138634
| | - Swee Liang Wong
- Institute of Materials Research & Engineering (IMRE), A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, Singapore 138634
| | - Yu Jie Zheng
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117542
| | - Ming-Yang Li
- Research Center for Applied Sciences, Academia Sinica , Taipei 10617, Taiwan
- Physical Sciences and Engineering, King Abdullah University of Science and Technology , Thuwal 23955-6900, Saudi Arabia
| | - Lain-Jong Li
- Physical Sciences and Engineering, King Abdullah University of Science and Technology , Thuwal 23955-6900, Saudi Arabia
| | - Wei Chen
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117542
- Department of Chemistry, National University of Singapore , 2 Science Drive 3, Singapore 117542
- Centre for Advanced 2D Materials, National University of Singapore , Block S14, Level 6, 6 Science Drive 2, Singapore 117546
| | - Norbert Koch
- Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin , Brook-Taylor Straße 6, 12489 Berlin, Germany
| | - Yu Li Huang
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117542
- Institute of Materials Research & Engineering (IMRE), A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, Singapore 138634
| | - Andrew Thye Shen Wee
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117542
- Institute of Materials Research & Engineering (IMRE), A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, Singapore 138634
- Centre for Advanced 2D Materials, National University of Singapore , Block S14, Level 6, 6 Science Drive 2, Singapore 117546
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41
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Tian T, Shih CJ. Molecular Epitaxy on Two-Dimensional Materials: The Interplay between Interactions. Ind Eng Chem Res 2017. [DOI: 10.1021/acs.iecr.7b02669] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Tian Tian
- Institute for Chemical and
Bioengineering, ETH Zürich, Vladimir Prelog Weg 1, CH-8093 Zürich, Switzerland
| | - Chih-Jen Shih
- Institute for Chemical and
Bioengineering, ETH Zürich, Vladimir Prelog Weg 1, CH-8093 Zürich, Switzerland
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42
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Xia W, Dai L, Yu P, Tong X, Song W, Zhang G, Wang Z. Recent progress in van der Waals heterojunctions. NANOSCALE 2017; 9:4324-4365. [PMID: 28317972 DOI: 10.1039/c7nr00844a] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Following the development of many novel two-dimensional (2D) materials, investigations of van der Waals heterojunctions (vdWHs) have attracted significant attention due to their excellent properties such as smooth heterointerface, highly gate-tunable bandgap, and ultrafast carrier transport. Benefits from the atom-scale thickness, physical and chemical properties and ease of manipulation of the heterojunctions formulated by weak vdW forces were demonstrated to indicate their outstanding potential in electronic and optoelectronic applications, including photodetection and energy harvesting, and the possibility of integrating them with the existing semiconductor technology for the next-generation electronic and sensing devices. In this review, we summarized the recent developments of vdWHs and emphasized their applications. Basically, we introduced the physical properties and some newly discovered phenomena in vdWHs. Then, we emphatically presented four classical vdWHs and some novel heterostructures formed by vdW forces. Based on their unique physical properties and structures, we highlighted the applications of vdWHs including in photodiodes, phototransistors, tunneling devices, and memory devices. Finally, we provided a conclusion on the recent advances in vdWHs and outlined our perspectives. We aim for this review to serve as a solid foundation in this field and to pave the way for future research on vdW-based materials and their heterostructures.
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Affiliation(s)
- Wanshun Xia
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, P.R. China. and Institute of Fundamental and Frontier Science, University of Electronic Science and Technology of China, Chengdu 610054, P. R. China.
| | - Liping Dai
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, P.R. China.
| | - Peng Yu
- Institute of Fundamental and Frontier Science, University of Electronic Science and Technology of China, Chengdu 610054, P. R. China.
| | - Xin Tong
- Institute of Fundamental and Frontier Science, University of Electronic Science and Technology of China, Chengdu 610054, P. R. China.
| | - Wenping Song
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, P.R. China.
| | - Guojun Zhang
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, P.R. China.
| | - Zhiming Wang
- Institute of Fundamental and Frontier Science, University of Electronic Science and Technology of China, Chengdu 610054, P. R. China.
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43
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Kumar A, Banerjee K, Liljeroth P. Molecular assembly on two-dimensional materials. NANOTECHNOLOGY 2017; 28:082001. [PMID: 28045007 DOI: 10.1088/1361-6528/aa564f] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Molecular self-assembly is a well-known technique to create highly functional nanostructures on surfaces. Self-assembly on two-dimensional (2D) materials is a developing field driven by the interest in functionalization of 2D materials in order to tune their electronic properties. This has resulted in the discovery of several rich and interesting phenomena. Here, we review this progress with an emphasis on the electronic properties of the adsorbates and the substrate in well-defined systems, as unveiled by scanning tunneling microscopy. The review covers three aspects of the self-assembly. The first one focuses on non-covalent self-assembly dealing with site-selectivity due to inherent moiré pattern present on 2D materials grown on substrates. We also see that modification of intermolecular interactions and molecule-substrate interactions influences the assembly drastically and that 2D materials can also be used as a platform to carry out covalent and metal-coordinated assembly. The second part deals with the electronic properties of molecules adsorbed on 2D materials. By virtue of being inert and possessing low density of states near the Fermi level, 2D materials decouple molecules electronically from the underlying metal substrate and allow high-resolution spectroscopy and imaging of molecular orbitals. The moiré pattern on the 2D materials causes site-selective gating and charging of molecules in some cases. The last section covers the effects of self-assembled, acceptor and donor type, organic molecules on the electronic properties of graphene as revealed by spectroscopy and electrical transport measurements. Non-covalent functionalization of 2D materials has already been applied for their application as catalysts and sensors. With the current surge of activity on building van der Waals heterostructures from atomically thin crystals, molecular self-assembly has the potential to add an extra level of flexibility and functionality for applications ranging from flexible electronics and OLEDs to novel electronic devices and spintronics.
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Affiliation(s)
- Avijit Kumar
- Department of Applied Physics Aalto, University School of Science, PO Box 15100, FI-00076 Aalto, Finland
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44
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Yin X, Wang Q, Zheng YJ, Song Z, Bin Hassan MH, Qi D, Wu J, Rusydi A, Wee ATS. Molecular Alignment and Electronic Structure of N,N'-Dibutyl-3,4,9,10-perylene-tetracarboxylic-diimide Molecules on MoS 2 Surfaces. ACS APPLIED MATERIALS & INTERFACES 2017; 9:5566-5573. [PMID: 28157294 DOI: 10.1021/acsami.6b14000] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The molecular orientation of organic semiconductors on a solid surface could be an indispensable factor to determine the electrical performance of organic-based devices. Despite its fundamental prominence, a clear description of the emergent two-dimensional layered material-organic interface is not fully understood yet. In this study, we reveal the molecular alignment and electronic structure of thermally deposited N,N'-dibutyl-3,4,9,10-perylene-dicarboximide (PTCDI-C4) molecules on natural molybdenum disulfide (MoS2) using near-edge X-ray absorption fine structure spectroscopy (NEXAFS). The average tilt angle determination reveals that the anisotropy in the π* symmetry transition of the carbon K-edge (284-288 eV range) is present at the sub-monolayer regime. Supported by ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), and resonant photoemission spectroscopy (RPES) measurements, we find that our spectroscopic measurements indicate a weak charge transfer established at the PTCDI-C4/MoS2 interface. Sterical hindrance due to the C4 alkyl chain caused tilting of the molecular plane at the initial thin film deposition. Our result shows a tunable interfacial alignment of organic molecules on transition metal dichalcogenide surfaces effectively enhancing the electronic properties of hybrid organic-inorganic heterostructure devices.
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Affiliation(s)
- Xinmao Yin
- Department of Physics, National University of Singapore , 2 Science Drive 3, 117542 Singapore
- Singapore Synchrotron Light Source, National University of Singapore , 5 Research Link, Singapore 1176033
- SZU-NUS Collaborative Innovation Center for Optoelectronic Science and Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Shenzhen University , Shenzhen 518060, China
| | - Qixing Wang
- Department of Physics, National University of Singapore , 2 Science Drive 3, 117542 Singapore
| | - Yu J Zheng
- Department of Physics, National University of Singapore , 2 Science Drive 3, 117542 Singapore
| | - Zhibo Song
- Department of Physics, National University of Singapore , 2 Science Drive 3, 117542 Singapore
| | - Mohammad H Bin Hassan
- Department of Physics, National University of Singapore , 2 Science Drive 3, 117542 Singapore
| | - Dianyu Qi
- Department of Physics, National University of Singapore , 2 Science Drive 3, 117542 Singapore
| | - Jishan Wu
- Department of Chemistry, National University of Singapore , 3 Science Drive 3, 117543 Singapore
| | - Andrivo Rusydi
- Department of Physics, National University of Singapore , 2 Science Drive 3, 117542 Singapore
- Singapore Synchrotron Light Source, National University of Singapore , 5 Research Link, Singapore 1176033
- NUSNNI-NanoCore, National University of Singapore , Singapore 117411
| | - Andrew T S Wee
- Department of Physics, National University of Singapore , 2 Science Drive 3, 117542 Singapore
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45
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Zhao Y, Zhou Q, Li Q, Yao X, Wang J. Passivation of Black Phosphorus via Self-Assembled Organic Monolayers by van der Waals Epitaxy. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1603990. [PMID: 27966825 DOI: 10.1002/adma.201603990] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 10/04/2016] [Indexed: 06/06/2023]
Abstract
An effective passivation approach to protect black phosphorus (BP) from degradation based on multi-scale simulations is proposed. The self-assembly of perylene-3,4,9,10-tetracarboxylic dianhydride monolayers via van der Waals epitaxy on BP does not break the original electronic properties of BP. The passivation layer thickness is only 2 nm. This study opens up a new pathway toward fine passivation of BP.
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Affiliation(s)
- Yinghe Zhao
- Department of Physics, Southeast University, Nanjing, 211189, China
| | - Qionghua Zhou
- Department of Physics, Southeast University, Nanjing, 211189, China
| | - Qiang Li
- Department of Physics, Southeast University, Nanjing, 211189, China
| | - Xiaojing Yao
- Department of Physics, Southeast University, Nanjing, 211189, China
| | - Jinlan Wang
- Department of Physics, Southeast University, Nanjing, 211189, China
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46
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Epitaxy of highly ordered organic semiconductor crystallite networks supported by hexagonal boron nitride. Sci Rep 2016; 6:38519. [PMID: 27929042 PMCID: PMC5143978 DOI: 10.1038/srep38519] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 11/09/2016] [Indexed: 01/13/2023] Open
Abstract
This study focuses on hexagonal boron nitride as an ultra-thin van der Waals dielectric substrate for the epitaxial growth of highly ordered crystalline networks of the organic semiconductor parahexaphenyl. Atomic force microscopy based morphology analysis combined with density functional theory simulations reveal their epitaxial relation. As a consequence, needle-like crystallites of parahexaphenyl grow with their long axes oriented five degrees off the hexagonal boron nitride zigzag directions. In addition, by tuning the deposition temperature and the thickness of hexagonal boron nitride, ordered networks of needle-like crystallites as long as several tens of micrometers can be obtained. A deeper understanding of the organic crystallites growth and ordering at ultra-thin van der Waals dielectric substrates will lead to grain boundary-free organic field effect devices, limited only by the intrinsic properties of the organic semiconductors.
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47
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Wee ATS, Hersam MC, Chhowalla M, Gogotsi Y. An Update from Flatland. ACS NANO 2016; 10:8121-8123. [PMID: 27669757 DOI: 10.1021/acsnano.6b06087] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
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48
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Van Der Waals Heterostructures between Small Organic Molecules and Layered Substrates. CRYSTALS 2016. [DOI: 10.3390/cryst6090113] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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49
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Liu X, Luo X, Nan H, Guo H, Wang P, Zhang L, Zhou M, Yang Z, Shi Y, Hu W, Ni Z, Qiu T, Yu Z, Xu JB, Wang X. Epitaxial Ultrathin Organic Crystals on Graphene for High-Efficiency Phototransistors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2016; 28:5200-5205. [PMID: 27146896 DOI: 10.1002/adma.201600400] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 03/24/2016] [Indexed: 06/05/2023]
Abstract
Epitaxially grown ultrathin organic semiconductors on graphene show great promise as highly efficient phototransistors. The devices exhibit a strong photoresponse down to the limit of a monolayer organic crystal, with a photoresponsivity higher than 10(4) A W(-1) and a photoconductive gain over 10(8) . The excellent performance is attributed to the high quality of the organic crystal and interface, a unique feature of van der Waals epitaxy.
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Affiliation(s)
- Xiaolong Liu
- National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Xiaoguang Luo
- Department of Physics, Southeast University, Nanjing, 211189, China
- Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Haiyan Nan
- Department of Physics, Southeast University, Nanjing, 211189, China
| | - Hui Guo
- School of Microelectronics, Xidian University, Xian, 710071, China
| | - Peng Wang
- National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yu Tian Road, Shanghai, 200083, China
| | - Linglong Zhang
- National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Minmin Zhou
- National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Ziyi Yang
- National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Yi Shi
- National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Weida Hu
- National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yu Tian Road, Shanghai, 200083, China
| | - Zhenhua Ni
- Department of Physics, Southeast University, Nanjing, 211189, China
| | - Teng Qiu
- Department of Physics, Southeast University, Nanjing, 211189, China
| | - Zongfu Yu
- Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Jian-Bin Xu
- Department of Electronic Engineering and Materials Science and Technology Research Center, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Xinran Wang
- National Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
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50
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Huang YL, Ding Z, Zhang W, Chang YH, Shi Y, Li LJ, Song Z, Zheng YJ, Chi D, Quek SY, Wee ATS. Gap States at Low-Angle Grain Boundaries in Monolayer Tungsten Diselenide. NANO LETTERS 2016; 16:3682-3688. [PMID: 27140667 DOI: 10.1021/acs.nanolett.6b00888] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Two-dimensional (2D) transition metal dichalcogenides (TMDs) have revealed many novel properties of interest to future device applications. In particular, the presence of grain boundaries (GBs) can significantly influence the material properties of 2D TMDs. However, direct characterization of the electronic properties of the GB defects at the atomic scale remains extremely challenging. In this study, we employ scanning tunneling microscopy and spectroscopy to investigate the atomic and electronic structure of low-angle GBs of monolayer tungsten diselenide (WSe2) with misorientation angles of 3-6°. Butterfly features are observed along the GBs, with the periodicity depending on the misorientation angle. Density functional theory calculations show that these butterfly features correspond to gap states that arise in tetragonal dislocation cores and extend to distorted six-membered rings around the dislocation core. Understanding the nature of GB defects and their influence on transport and other device properties highlights the importance of defect engineering in future 2D device fabrication.
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Affiliation(s)
- Yu Li Huang
- Institute of Materials Research & Engineering (IMRE), A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117551, Singapore
| | - Zijing Ding
- SZU-NUS Collaborative Innovation Center for Optoelectronic Science & Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Shenzhen University , Shenzhen 518060, China
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117551, Singapore
| | - Wenjing Zhang
- SZU-NUS Collaborative Innovation Center for Optoelectronic Science & Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Shenzhen University , Shenzhen 518060, China
| | - Yung-Huang Chang
- Department of Electrophysics, National Chiao Tung University , Hsinchu 300, Taiwan
| | - Yumeng Shi
- Physical Sciences and Engineering, King Abdullah University of Science and Technology , Thuwal 23955-6900, Saudi Arabia
| | - Lain-Jong Li
- Physical Sciences and Engineering, King Abdullah University of Science and Technology , Thuwal 23955-6900, Saudi Arabia
| | - Zhibo Song
- Institute of Materials Research & Engineering (IMRE), A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117551, Singapore
| | - Yu Jie Zheng
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117551, Singapore
| | - Dongzhi Chi
- Institute of Materials Research & Engineering (IMRE), A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis, Singapore 138634, Singapore
| | - Su Ying Quek
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117551, Singapore
- Centre for Advanced 2D Materials, National University of Singapore , Block S14, Level 6, 6 Science Drive 2, Singapore 117546, Singapore
| | - Andrew T S Wee
- Department of Physics, National University of Singapore , 2 Science Drive 3, Singapore 117551, Singapore
- Centre for Advanced 2D Materials, National University of Singapore , Block S14, Level 6, 6 Science Drive 2, Singapore 117546, Singapore
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