1
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Petrov E, Kapitanchuk O, Shevchenko Y, Gorbach V, Lyubchik A. Features of optoelectronic processes in a molecular junction based on a fluorophore with optically active Frontier π-orbitals: electrofluorochromism in a ZnPc-based junction. Phys Chem Chem Phys 2024; 26:22762-22774. [PMID: 39162092 DOI: 10.1039/d4cp01328j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/21/2024]
Abstract
A model of the optoelectronic process in a molecular junction has been developed, in which electron transfer occurs through transmission channels associated with the filling of the π and π* orbitals of the fluorophore with transferred electrons. The contribution of each channel to the formation of current and electroluminescence (EL) is determined by the probability of the realization of those electronic states of the molecule that, at a given bias voltage, are involved in electron transfer. It is shown that in the vicinity of critical bias voltage, stepwise changes in current and EL occur, and the height of each step is controlled by kinetic processes associated with both electron transfer and intramolecular transitions. Using the obtained analytical expressions for the relative intensities of the emission lines X0 and X+ and comparing theoretical results with experimental data on STM-induced EL in a ZnPc-based junction, we showed that the method for analyzing the behavior of current and EL near critical voltages can serve as an effective tool for understanding the physical mechanisms responsible for optoelectronic processes at the single-molecule level. The method also made it possible to obtain real values of the energy of the Frontier orbitals of the ZnPc molecule embedded between the electrodes, as well as the energies of those electronic states of the neutral and charged molecules that participate in the optoelectronic process, including electrofluorochromism.
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Affiliation(s)
- Elmar Petrov
- Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, Metrologichna str. 14-B, UA-03143 Kyiv, Ukraine.
| | - Oleksiy Kapitanchuk
- Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, Metrologichna str. 14-B, UA-03143 Kyiv, Ukraine.
| | - Yevgen Shevchenko
- Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, Metrologichna str. 14-B, UA-03143 Kyiv, Ukraine.
| | - Victor Gorbach
- Nanotechcenter LLC, Krzhizhanovsky str. 3, Kyiv, UA-03142, Ukraine
| | - Andriy Lyubchik
- DeepTechLab, Faculdade de Engenharia, Universidade Lusofona, Campo Grande, 376, Lisboa, 1749-024, Portugal
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2
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Bae J, Imai-Imada M, Kim HS, Lee M, Imada H, Tsuchiya Y, Hatakeyama T, Adachi C, Kim Y. Visualization of Multiple-Resonance-Induced Frontier Molecular Orbitals in a Single Multiple-Resonance Thermally Activated Delayed Fluorescence Molecule. ACS NANO 2024; 18:17987-17995. [PMID: 38934571 DOI: 10.1021/acsnano.4c04813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/28/2024]
Abstract
The spatial distribution and electronic properties of the frontier molecular orbitals (FMOs) in a thermally activated delayed fluorescence (TADF) molecule contribute significantly to the TADF properties, and thus, a detailed understanding and sophisticated control of the FMOs are fundamental to the design of TADF molecules. However, for multiple-resonance (MR)-TADF molecules that achieve spatial separation of FMOs by the MR effect, the distinctive distribution of these molecular orbitals poses significant challenges for conventional computational analysis and ensemble averaging methods to elucidate the FMOs' separation and the precise mechanism of luminescence. Therefore, the visualization and analysis of electronic states with the specific energy level of a single MR-TADF molecule will provide a deeper understanding of the TADF mechanism. Here, scanning tunneling microscopy/spectroscopy (STM/STS) was used to investigate the electronic states of the DABNA-1 molecule at the atomic scale. FMOs' visualization and local density of states analysis of the DABNA-1 molecule clearly show that MR-TADF molecules also have well-separated FMOs according to the internal heteroatom arrangement, providing insights that complement existing theoretical prediction methods.
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Affiliation(s)
- Jaehyun Bae
- Surface and Interface Science Laboratory (SISL), RIKEN, Wako, Saitama 351-0198, Japan
- Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
- Department of Applied Chemistry, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
| | - Miyabi Imai-Imada
- Surface and Interface Science Laboratory (SISL), RIKEN, Wako, Saitama 351-0198, Japan
- Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012, Japan
| | - Hyung Suk Kim
- Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
- Department of Applied Chemistry, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
| | - Minhui Lee
- Surface and Interface Science Laboratory (SISL), RIKEN, Wako, Saitama 351-0198, Japan
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 118-8656, Japan
| | - Hiroshi Imada
- Surface and Interface Science Laboratory (SISL), RIKEN, Wako, Saitama 351-0198, Japan
| | - Youichi Tsuchiya
- Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
| | - Takuji Hatakeyama
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto, Sakyo 606-8502, Japan
| | - Chihaya Adachi
- Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
- Department of Applied Chemistry, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
- International Institute for Carbon Neutral Energy Research (I2CNER), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
| | - Yousoo Kim
- Surface and Interface Science Laboratory (SISL), RIKEN, Wako, Saitama 351-0198, Japan
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 118-8656, Japan
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3
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Duan J, Wang J, Hou L, Ji P, Zhang W, Liu J, Zhu X, Sun Z, Ma Y, Ma L. Application of Scanning Tunneling Microscopy and Spectroscopy in the Studies of Colloidal Quantum Qots. CHEM REC 2023; 23:e202300120. [PMID: 37255365 DOI: 10.1002/tcr.202300120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 05/15/2023] [Indexed: 06/01/2023]
Abstract
Colloidal quantum dots display remarkable optical and electrical characteristics with the potential for extensive applications in contemporary nanotechnology. As an ideal instrument for examining surface topography and local density of states (LDOS) at an atomic scale, scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) has become indispensable approaches to gain better understanding of their physical properties. This article presents a comprehensive review of the research advancements in measuring the electronic orbits and corresponding energy levels of colloidal quantum dots in various systems using STM and STS. The first three sections introduce the basic principles of colloidal quantum dots synthesis and the fundamental methodology of STM research on quantum dots. The fourth section explores the latest progress in the application of STM for colloidal quantum dot studies. Finally, a summary and prospective is presented.
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Affiliation(s)
- Jiaying Duan
- Tianjin International Center for Nanoparticles and NanoSystems, Tianjin University, Tianjin, China, 300072
| | - Jiapeng Wang
- Tianjin International Center for Nanoparticles and NanoSystems, Tianjin University, Tianjin, China, 300072
| | - Liangpeng Hou
- Tianjin International Center for Nanoparticles and NanoSystems, Tianjin University, Tianjin, China, 300072
| | - Peixuan Ji
- Tianjin International Center for Nanoparticles and NanoSystems, Tianjin University, Tianjin, China, 300072
| | - Wusheng Zhang
- Tianjin International Center for Nanoparticles and NanoSystems, Tianjin University, Tianjin, China, 300072
| | - Jin Liu
- Tianjin International Center for Nanoparticles and NanoSystems, Tianjin University, Tianjin, China, 300072
| | - Xiaodong Zhu
- Tianjin International Center for Nanoparticles and NanoSystems, Tianjin University, Tianjin, China, 300072
| | - Zhixiang Sun
- Center for Joint Quantum Studies and Department of Physics, School of Science, Tianjin University, Tianjin, China, 300072
| | - Yanqing Ma
- Tianjin International Center for Nanoparticles and NanoSystems, Tianjin University, Tianjin, China, 300072
| | - Lei Ma
- Tianjin International Center for Nanoparticles and NanoSystems, Tianjin University, Tianjin, China, 300072
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4
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Li C, Kaspar C, Zhou P, Liu JC, Chahib O, Glatzel T, Häner R, Aschauer U, Decurtins S, Liu SX, Thoss M, Meyer E, Pawlak R. Strong signature of electron-vibration coupling in molecules on Ag(111) triggered by tip-gated discharging. Nat Commun 2023; 14:5956. [PMID: 37749099 PMCID: PMC10519934 DOI: 10.1038/s41467-023-41601-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 09/05/2023] [Indexed: 09/27/2023] Open
Abstract
Electron-vibration coupling is of critical importance for the development of molecular electronics, spintronics, and quantum technologies, as it affects transport properties and spin dynamics. The control over charge-state transitions and subsequent molecular vibrations using scanning tunneling microscopy typically requires the use of a decoupling layer. Here we show the vibronic excitations of tetrabromotetraazapyrene (TBTAP) molecules directly adsorbed on Ag(111) into an orientational glassy phase. The electron-deficient TBTAP is singly-occupied by an electron donated from the substrate, resulting in a spin 1/2 state, which is confirmed by a Kondo resonance. The TBTAP•- discharge is controlled by tip-gating and leads to a series of peaks in scanning tunneling spectroscopy. These occurrences are explained by combining a double-barrier tunneling junction with a Franck-Condon model including molecular vibrational modes. This work demonstrates that suitable precursor design enables gate-dependent vibrational excitations of molecules on a metal, thereby providing a method to investigate electron-vibration coupling in molecular assemblies without a decoupling layer.
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Affiliation(s)
- Chao Li
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland.
| | - Christoph Kaspar
- Institute of Physics, University of Freiburg, Hermann-Herder-Strasse 3, 79104, Freiburg, Germany
| | - Ping Zhou
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012, Bern, Switzerland
| | - Jung-Ching Liu
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
| | - Outhmane Chahib
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
| | - Thilo Glatzel
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland
| | - Robert Häner
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012, Bern, Switzerland
| | - Ulrich Aschauer
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012, Bern, Switzerland
- Department of Chemistry and Physics of Materials, University of Salzburg, Jakob-Haringer-Strasse 2A, 5020 Salzburg, Austria
| | - Silvio Decurtins
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012, Bern, Switzerland
| | - Shi-Xia Liu
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012, Bern, Switzerland.
| | - Michael Thoss
- Institute of Physics, University of Freiburg, Hermann-Herder-Strasse 3, 79104, Freiburg, Germany
- EUCOR Centre for Quantum Science and Quantum Computing, University of Freiburg, Hermann-Herder-Str. 3, 79104, Freiburg, Germany
| | - Ernst Meyer
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland.
| | - Rémy Pawlak
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056, Basel, Switzerland.
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Kaiser K, Lieske LA, Repp J, Gross L. Charge-state lifetimes of single molecules on few monolayers of NaCl. Nat Commun 2023; 14:4988. [PMID: 37591847 PMCID: PMC10435478 DOI: 10.1038/s41467-023-40692-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Accepted: 08/02/2023] [Indexed: 08/19/2023] Open
Abstract
In molecular tunnel junctions, where the molecule is decoupled from the electrodes by few-monolayers-thin insulating layers, resonant charge transport takes place by sequential charge transfer to and from the molecule which implies transient charging of the molecule. The corresponding charge state transitions, which involve tunneling through the insulating decoupling layers, are crucial for understanding electrically driven processes such as electroluminescence or photocurrent generation in such a geometry. Here, we use scanning tunneling microscopy to investigate the decharging of single ZnPc and H2Pc molecules through NaCl films of 3 to 5 monolayers thickness on Cu(111) and Au(111). To this end, we approach the tip to the molecule at resonant tunnel conditions up to a regime where charge transport is limited by tunneling through the NaCl film. The resulting saturation of the tunnel current is a direct measure of the lifetimes of the anionic and cationic states, i.e., the molecule's charge-state lifetime, and thus provides a means to study charge dynamics and, thereby, exciton dynamics. Comparison of anion and cation lifetimes on different substrates reveals the critical role of the level alignment with the insulator's conduction and valence band, and the metal-insulator interface state.
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Affiliation(s)
- Katharina Kaiser
- IBM Research Europe-Zurich, Säumerstrasse 4, 8803, Rüschlikon, Switzerland.
- Université de Strasbourg, CNRS, IPCMS, UMR 7504, F-67000, Strasbourg, France.
| | | | - Jascha Repp
- Department of Physics, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Leo Gross
- IBM Research Europe-Zurich, Säumerstrasse 4, 8803, Rüschlikon, Switzerland.
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6
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Orbital-resolved visualization of single-molecule photocurrent channels. Nature 2022; 603:829-834. [PMID: 35354999 DOI: 10.1038/s41586-022-04401-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 01/03/2022] [Indexed: 11/08/2022]
Abstract
Given its central role in utilizing light energy, photoinduced electron transfer (PET) from an excited molecule has been widely studied1-6. However, even though microscopic photocurrent measurement methods7-11 have made it possible to correlate the efficiency of the process with local features, spatial resolution has been insufficient to resolve it at the molecular level. Recent work has, however, shown that single molecules can be efficiently excited and probed when combining a scanning tunnelling microscope (STM) with localized plasmon fields driven by a tunable laser12,13. Here we use that approach to directly visualize with atomic-scale resolution the photocurrent channels through the molecular orbitals of a single free-base phthalocyanine (FBPc) molecule, by detecting electrons from its first excited state tunnelling through the STM tip. We find that the direction and the spatial distribution of the photocurrent depend sensitively on the bias voltage, and detect counter-flowing photocurrent channels even at a voltage where the averaged photocurrent is near zero. Moreover, we see evidence of competition between PET and photoluminescence12, and find that we can control whether the excited molecule primarily relaxes through PET or photoluminescence by positioning the STM tip with three-dimensional, atomic precision. These observations suggest that specific photocurrent channels can be promoted or suppressed by tuning the coupling to excited-state molecular orbitals, and thus provide new perspectives for improving energy-conversion efficiencies by atomic-scale electronic and geometric engineering of molecular interfaces.
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7
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Tao L, Zhang Y, Du S. Structures and electronic properties of functional molecules on metal substrates: From single molecule to self‐assemblies. WIRES COMPUTATIONAL MOLECULAR SCIENCE 2021. [DOI: 10.1002/wcms.1591] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Lei Tao
- Institute of Physics and University of Chinese Academy of Sciences Chinese Academy of Sciences Beijing China
| | - Yu‐yang Zhang
- Institute of Physics and University of Chinese Academy of Sciences Chinese Academy of Sciences Beijing China
- CAS Center for Excellence in Topological Quantum Computation Beijing China
| | - Shixuan Du
- Institute of Physics and University of Chinese Academy of Sciences Chinese Academy of Sciences Beijing China
- CAS Center for Excellence in Topological Quantum Computation Beijing China
- Beijing National Laboratory for Condensed Matter Physics Beijing China
- Songshan Lake Materials Laboratory Dongguan China
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8
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Tian G, Qiu F, Song C, Duan S, Luo Y. Electric Field Controlled Single-Molecule Optical Switch by Through-Space Charge Transfer State. J Phys Chem Lett 2021; 12:9094-9099. [PMID: 34520213 DOI: 10.1021/acs.jpclett.1c02578] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Controlling the photon emission property of a single molecule is an important goal for nano-optics. We propose here a new mechanism for a single-molecule optical switch that utilizes the in situ electric field (EF) in biased metallic nanojunctions to control photon emission of molecules with through-space charge transfer (TSCT) excited states. The EF-induced Stark effect is capable of flipping the order of the bright noncharge transfer state and dark TSCT state, resulting in the anticipated switching behavior. The proposed mechanism was theoretically verified by scanning tunneling microscope-induced electroluminescence from a naphtalenediimide cyclophane molecule under experimentally accessible conditions. Simulations show that the proposed switching effect can be obtained by changing either bias polarity, which alters the polarization of the field, or tip-height, which affects the magnitude of the field. Our finding indicates that the in situ EF could play an important role in the design of optoelectronic molecular devices.
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Affiliation(s)
- Guangjun Tian
- State Key Laboratory of Metastable Materials Science & Technology and Key Laboratory for Microstructural Material Physics of Hebei Province, School of Science, Yanshan University, Qinhuangdao 066004, P. R. China
| | - Feifei Qiu
- State Key Laboratory of Metastable Materials Science & Technology and Key Laboratory for Microstructural Material Physics of Hebei Province, School of Science, Yanshan University, Qinhuangdao 066004, P. R. China
| | - Ce Song
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, 230026 Anhui, P. R. China
- Department of Theoretical Chemistry and Biology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, S-106 91 Stockholm, Sweden
| | - Sai Duan
- Collaborative Innovation Center of Chemistry for Energy Materials, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, MOE Key Laboratory of Computational Physical Sciences, Department of Chemistry, Fudan University, Shanghai 200433, P. R. China
| | - Yi Luo
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, 230026 Anhui, P. R. China
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9
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Fatayer S, Albrecht F, Tavernelli I, Persson M, Moll N, Gross L. Probing Molecular Excited States by Atomic Force Microscopy. PHYSICAL REVIEW LETTERS 2021; 126:176801. [PMID: 33988431 DOI: 10.1103/physrevlett.126.176801] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 10/12/2020] [Accepted: 03/24/2021] [Indexed: 06/12/2023]
Abstract
By employing single charge injections with an atomic force microscope, we investigated redox reactions of a molecule on a multilayer insulating film. First, we charged the molecule positively by attaching a single hole. Then we neutralized it by attaching an electron and observed three channels for the neutralization. We rationalize that the three channels correspond to transitions to the neutral ground state, to the lowest energy triplet excited states and to the lowest energy singlet excited states. By single-electron tunneling spectroscopy we measured the energy differences between the transitions obtaining triplet and singlet excited state energies. The experimental values are compared with density functional theory calculations of the excited state energies. Our results show that molecules in excited states can be prepared and that energies of optical gaps can be quantified by controlled single-charge injections. Our work demonstrates the access to, and provides insight into, ubiquitous electron-attachment processes related to excited-state transitions important in electron transfer and molecular optoelectronics phenomena on surfaces.
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Affiliation(s)
- Shadi Fatayer
- IBM Research-Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - Florian Albrecht
- IBM Research-Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - Ivano Tavernelli
- IBM Research-Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - Mats Persson
- Surface Science Research Centre, Department of Chemistry, University of Liverpool, Liverpool L693BX, United Kingdom
| | - Nikolaj Moll
- IBM Research-Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - Leo Gross
- IBM Research-Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
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10
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Singh J, Singh R, Gautam SK, Gupta H, Ojha S, Singh F. Swift heavy ion irradiation induced negative differential resistance and transport of charge carriers in conducting polymer-metal oxide hybrids. Radiat Phys Chem Oxf Engl 1993 2021. [DOI: 10.1016/j.radphyschem.2020.109211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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11
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Dong X, Hu Y, Ren S, Zhang P. Spatially Resolved Investigation of Mixed Valence and Insulator-to-Metal Transition in an Organic Salt. J Phys Chem Lett 2020; 11:8352-8357. [PMID: 32914983 DOI: 10.1021/acs.jpclett.0c02303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Using scanning tunneling microscopy/spectroscopy (STM/STS), we investigate the evolution of electronic structures across the boundaries of 7,7,8,8-tetracyanoquinodimethane (TCNQ) and K-TCNQ assemblies on a weakly interacting substrate. Despite the semiconducting/insulating nature of TCNQ (TCNQ0) and K-TCNQ (TCNQ-1), a continuum metallic-like density of states extending deep (∼1.5 nm) into the TCNQ assembly is observed near the domain boundary. We attribute the formation of these states to the abrupt change of molecular valence, which perturbs the electrostatics of the junction and creates local electric fields as evidenced by the band bending near the domain boundary. To the best of our knowledge, this study provides the first microscopic understanding of the crucial physics occurring near domain boundaries of mixed valence in K-TCNQ, or broadly speaking charge-transfer complexes, which highlights these boundaries as potential "weak" points to initiate the electric field-induced insulator-to-metal transition.
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Affiliation(s)
- Xi Dong
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, United States
| | - Yong Hu
- Department of Mechanical and Aerospace Engineering, Research and Education in Energy Environment & Water Institute, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Shenqiang Ren
- Department of Mechanical and Aerospace Engineering, Research and Education in Energy Environment & Water Institute, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
- Department of Chemistry, University of Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Pengpeng Zhang
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, United States
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12
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Bouatou M, Mondal S, Chacon C, Joucken F, Girard Y, Repain V, Bellec A, Rousset S, Narasimhan S, Sporken R, Dappe YJ, Lagoute J. Direct Observation of the Reduction of a Molecule on Nitrogen Pairs in Doped Graphene. NANO LETTERS 2020; 20:6908-6913. [PMID: 32830982 DOI: 10.1021/acs.nanolett.0c03030] [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
Incorporating functional atomic sites in graphene is essential for realizing advanced two-dimensional materials. Doping graphene with nitrogen offers the opportunity to tune its chemical activity with significant charge redistribution occurring between molecules and substrate. The necessary atomic scale understanding of how this depends on the spatial distribution of dopants, as well as their positions relative to the molecule, can be provided by scanning tunneling microscopy. Here we show that a noncovalently bonded molecule such as CoPc undergoes a variable charge transfer when placed on N-doped graphene; on a nitrogen pair, it undergoes a redox reaction with an integral charge transfer whereas a lower fractional charge transfer occurs over a single nitrogen. Thus, the charge state of molecules can be tuned by suitably tailoring the conformation of dopant atoms.
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Affiliation(s)
- Mehdi Bouatou
- Laboratoire Matériaux et Phénomènes Quantiques, CNRS, Université de Paris, F-75013, Paris, France
| | - Sourav Mondal
- Theoretical Sciences Unit and School of Advanced Materials, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India
| | - Cyril Chacon
- Laboratoire Matériaux et Phénomènes Quantiques, CNRS, Université de Paris, F-75013, Paris, France
| | - Frédéric Joucken
- Research Center in Physics of Matter and Radiation (PMR), Université de Namur, 61 Rue de Bruxelles, 5000 Namur, Belgium
| | - Yann Girard
- Laboratoire Matériaux et Phénomènes Quantiques, CNRS, Université de Paris, F-75013, Paris, France
| | - Vincent Repain
- Laboratoire Matériaux et Phénomènes Quantiques, CNRS, Université de Paris, F-75013, Paris, France
| | - Amandine Bellec
- Laboratoire Matériaux et Phénomènes Quantiques, CNRS, Université de Paris, F-75013, Paris, France
| | - Sylvie Rousset
- Laboratoire Matériaux et Phénomènes Quantiques, CNRS, Université de Paris, F-75013, Paris, France
| | - Shobhana Narasimhan
- Theoretical Sciences Unit and School of Advanced Materials, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India
| | - Robert Sporken
- Research Center in Physics of Matter and Radiation (PMR), Université de Namur, 61 Rue de Bruxelles, 5000 Namur, Belgium
| | - Yannick J Dappe
- SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette Cedex France
| | - Jérôme Lagoute
- Laboratoire Matériaux et Phénomènes Quantiques, CNRS, Université de Paris, F-75013, Paris, France
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13
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Petrov EG, Gorbach VV, Ragulya AV, Lyubchik A, Lyubchik S. Gate-tunable electroluminescence in Aviram-Ratner-type molecules: Kinetic description. J Chem Phys 2020; 153:084105. [PMID: 32872853 DOI: 10.1063/5.0018574] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A theoretical study of the mechanisms of electroluminescence (EL) generation in photoactive molecules with donor and acceptor centers linked by saturated σ-bonds (molecules of the Aviram-Ratner-type) is presented. The approach is based on the kinetics of single-electron transitions between many-body molecular states. This study shows that the EL polarity arises due to asymmetric coupling of molecular orbitals of the photochromic part of the molecule to the electrodes. The gate voltage controls the power of the EL through the occupancy of the excited singlet state. The shifting of the orbital energies forms a resonant or a non-resonant path for the transmission of electrons through the molecule. The action of the gate voltage is reflected in specific critical voltages. An analytical dependence of the critical voltages on the energies of molecular states involved in the formation of EL, as well as on the gate voltage, was derived for both positive and negative polarities. Conditions under which the gate voltage lowers the absolute value of the bias voltage that is responsible for the activation of the resonance mechanism of EL formation were also established. This is an important factor in control of EL in molecular junctions.
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Affiliation(s)
- Elmar G Petrov
- Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, Metrologichna Street 14-B, UA-03680 Kiev, Ukraine
| | | | | | | | - Svetlana Lyubchik
- REQUIMTE, Departomento Quimica, FCT, Universidade Nova de Lisboa, Caparica 2829-516, Portugal
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14
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Guo C, Meng X, Fu H, Wang Q, Wang H, Tian Y, Peng J, Ma R, Weng Y, Meng S, Wang E, Jiang Y. Probing Nonequilibrium Dynamics of Photoexcited Polarons on a Metal-Oxide Surface with Atomic Precision. PHYSICAL REVIEW LETTERS 2020; 124:206801. [PMID: 32501065 DOI: 10.1103/physrevlett.124.206801] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Revised: 01/26/2020] [Accepted: 04/09/2020] [Indexed: 06/11/2023]
Abstract
Understanding the nonequilibrium dynamics of photoexcited polarons at the atomic scale is of great importance for improving the performance of photocatalytic and solar-energy materials. Using a pulsed-laser-combined scanning tunneling microscopy and spectroscopy, here we succeeded in resolving the relaxation dynamics of single polarons bound to oxygen vacancies on the surface of a prototypical photocatalyst, rutile TiO_{2}(110). The visible-light excitation of the defect-derived polarons depletes the polaron states and leads to delocalized free electrons in the conduction band, which is further corroborated by ab initio calculations. We found that the trapping time of polarons becomes considerably shorter when the polaron is bound to two surface oxygen vacancies than that to one. In contrast, the lifetime of photogenerated free electrons is insensitive to the atomic-scale distribution of the defects but correlated with the averaged defect density within a nanometer-sized area. Those results shed new light on the photocatalytically active sites at the metal-oxide surface.
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Affiliation(s)
- Chaoyu Guo
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
- Physical Science Laboratory, Huairou National Comprehensive Science Centre, Beijing 101400, People's Republic of China
| | - Xiangzhi Meng
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | - Huixia Fu
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Qin Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | - Huimin Wang
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Ye Tian
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | - Jinbo Peng
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | - Runze Ma
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | - Yuxiang Weng
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Sheng Meng
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, People's Republic of China
| | - Enge Wang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, People's Republic of China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Ying Jiang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, People's Republic of China
- CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, People's Republic of China
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15
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Kumar D, Krull C, Yin Y, Medhekar NV, Schiffrin A. Electric Field Control of Molecular Charge State in a Single-Component 2D Organic Nanoarray. ACS NANO 2019; 13:11882-11890. [PMID: 31584795 DOI: 10.1021/acsnano.9b05950] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Quantum dots (QD) with electric-field-controlled charge state are promising for electronics applications, e.g., digital information storage, single-electron transistors, and quantum computing. Inorganic QDs consisting of semiconductor nanostructures or heterostructures often offer limited control on size and composition distribution as well as low potential for scalability and/or nanoscale miniaturization. Owing to their tunability and self-assembly capability, using organic molecules as building nanounits can allow for bottom-up synthesis of two-dimensional (2D) nanoarrays of QDs. However, 2D molecular self-assembly protocols are often applicable on metals surfaces, where electronic hybridization and Fermi level pinning can hinder electric-field control of the QD charge state. Here, we demonstrate the synthesis of a single-component self-assembled 2D array of molecules [9,10-dicyanoanthracene (DCA)] that exhibit electric-field-controlled spatially periodic charging on a noble metal surface, Ag(111). The charge state of DCA can be altered (between neutral and negative), depending on its adsorption site, by the local electric field induced by a scanning tunneling microscope tip. Limited metal-molecule interactions result in an effective tunneling barrier between DCA and Ag(111) that enables electric-field-induced electron population of the lowest unoccupied molecular orbital (LUMO) and, hence, charging of the molecule. Subtle site-dependent variation of the molecular adsorption height translates into a significant spatial modulation of the molecular polarizability, dielectric constant, and LUMO energy level alignment, giving rise to a spatially dependent effective molecule-surface tunneling barrier and likelihood of charging. This work offers potential for high-density 2D self-assembled nanoarrays of identical QDs whose charge states can be addressed individually with an electric field.
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Affiliation(s)
- Dhaneesh Kumar
- School of Physics & Astronomy , Monash University , Clayton , Victoria 3800 , Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies , Monash University , Clayton , Victoria 3800 , Australia
| | - Cornelius Krull
- School of Physics & Astronomy , Monash University , Clayton , Victoria 3800 , Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies , Monash University , Clayton , Victoria 3800 , Australia
| | - Yuefeng Yin
- School of Physics & Astronomy , Monash University , Clayton , Victoria 3800 , Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies , Monash University , Clayton , Victoria 3800 , Australia
- Department of Materials Science and Engineering , Monash University , Clayton , Victoria 3800 , Australia
| | - Nikhil V Medhekar
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies , Monash University , Clayton , Victoria 3800 , Australia
- Department of Materials Science and Engineering , Monash University , Clayton , Victoria 3800 , Australia
| | - Agustin Schiffrin
- School of Physics & Astronomy , Monash University , Clayton , Victoria 3800 , Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies , Monash University , Clayton , Victoria 3800 , Australia
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16
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Limburg B, Thomas JO, Sowa JK, Willick K, Baugh J, Gauger EM, Briggs GAD, Mol JA, Anderson HL. Charge-state assignment of nanoscale single-electron transistors from their current-voltage characteristics. NANOSCALE 2019; 11:14820-14827. [PMID: 31355401 DOI: 10.1039/c9nr03754c] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The electronic and magnetic properties of single-molecule transistors depend critically on the molecular charge state. Charge transport in single-molecule transistors is characterized by Coulomb-blocked regions in which the charge state of the molecule is fixed and current is suppressed, separated by high-conductance, sequential-tunneling regions. It is often difficult to assign the charge state of the molecular species in each Coulomb-blocked region due to variability in the work-function of the electrodes. In this work, we provide a simple and fast method to assign the charge state of the molecular species in the Coulomb-blocked regions based on signatures of electron-phonon coupling together with the Pauli-exclusion principle, simply by observing the asymmetry in the current in high-conductance regions of the stability diagram. We demonstrate that charge-state assignments determined in this way are consistent with those obtained from measurements of Zeeman splittings. Our method is applicable at 77 K, in contrast to magnetic-field-dependent measurements, which generally require low temperatures (below 4 K). Due to the ubiquity of electron-phonon coupling in molecular junctions, we expect this method to be widely applicable to single-electron transistors based on single molecules and graphene quantum dots. The correct assignment of charge states allows researchers to better understand the fundamental charge-transport properties of single-molecule transistors.
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Affiliation(s)
- Bart Limburg
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Oxford OX1 3TA, UK.
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17
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Kaiser K, Gross L, Schulz F. A Single-Molecule Chemical Reaction Studied by High-Resolution Atomic Force Microscopy and Scanning Tunneling Microscopy Induced Light Emission. ACS NANO 2019; 13:6947-6954. [PMID: 31184117 PMCID: PMC6595658 DOI: 10.1021/acsnano.9b01852] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Atomic force microscopy (AFM) as well as scanning tunneling microscopy induced light emission (STM-LE) are, each on their own, powerful tools used to investigate a large variety of properties of single molecules adsorbed on a surface. However, accessing both structural information by AFM as well as optical information by STM-LE on the same molecule so far remains elusive. We present a combined high-resolution AFM and STM-LE study on single metal-oxide phthalocyanines. Using atomic manipulation, the molecules can be deliberately reduced. We demonstrate structure elucidation and adsorption geometry determination of single molecules with atomic resolution combined with optical characterization by STM-LE and the possibility of investigating the change in a molecule's exciton emission intensity by a chemical reaction.
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18
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Selective triplet exciton formation in a single molecule. Nature 2019; 570:210-213. [DOI: 10.1038/s41586-019-1284-2] [Citation(s) in RCA: 96] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 04/02/2019] [Indexed: 11/08/2022]
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19
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20
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Sowa JK, Mol JA, Briggs GAD, Gauger EM. Beyond Marcus theory and the Landauer-Büttiker approach in molecular junctions: A unified framework. J Chem Phys 2018; 149:154112. [DOI: 10.1063/1.5049537] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Affiliation(s)
- Jakub K. Sowa
- Department of Materials, University of Oxford, Parks Road, OX1 3PH Oxford, United Kingdom
| | - Jan A. Mol
- Department of Materials, University of Oxford, Parks Road, OX1 3PH Oxford, United Kingdom
| | - G. Andrew D. Briggs
- Department of Materials, University of Oxford, Parks Road, OX1 3PH Oxford, United Kingdom
| | - Erik M. Gauger
- SUPA, Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom
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21
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Fereiro JA, Porat G, Bendikov T, Pecht I, Sheves M, Cahen D. Protein Electronics: Chemical Modulation of Contacts Control Energy Level Alignment in Gold-Azurin-Gold Junctions. J Am Chem Soc 2018; 140:13317-13326. [DOI: 10.1021/jacs.8b07742] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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22
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Zhang Y, Wang Y, Liao P, Wang K, Huang Z, Liu J, Chen Q, Jiang J, Wu K. Detection and Manipulation of Charge States for Double-Decker DyPc 2 Molecules on Ultrathin CuO Films. ACS NANO 2018; 12:2991-2997. [PMID: 29485853 DOI: 10.1021/acsnano.8b00751] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Charge states of lanthanide double-decker phthalocyanines complexes significantly influence their geometrical structures and magnetic properties. In this study, the charge states of single DyPc2 molecules on an ultrathin CuO film were detected by scanning tunneling microscopy and spectroscopy in magnetic fields. Four types of adsorptions of DyPc2 molecules on CuO were experimentally observed. Without applying voltages, two of them were positively charged with the other two at the neutral state. By controlling the sample bias, two types of neutral molecules can be switched to the positively and negatively charged states, respectively. This manipulation was not realized for the DyPc2 cations. A way to precisely detect the molecular charge states with and without current is beneficial for the development of molecular electronics.
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Affiliation(s)
- Yajie Zhang
- BNLMS, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Yongfeng Wang
- Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics , Peking University , Beijing 100871 , China
| | - Peilin Liao
- School of Materials Engineering , Purdue University , West Lafayette , Indiana 47907 , United States
| | - Kang Wang
- Department of Chemistry , Beijing University of Science and Technology , Beijing 100083 , China
| | - Zhichao Huang
- BNLMS, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Jing Liu
- BNLMS, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Qiwei Chen
- BNLMS, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
| | - Jianzhuang Jiang
- Department of Chemistry , Beijing University of Science and Technology , Beijing 100083 , China
| | - Kai Wu
- BNLMS, College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China
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23
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Bouvron S, Maurand R, Graf A, Erler P, Gragnaniello L, Skripnik M, Wiedmann D, Engesser C, Nef C, Fu W, Schönenberger C, Pauly F, Fonin M. Charge transport in a single molecule transistor probed by scanning tunneling microscopy. NANOSCALE 2018; 10:1487-1493. [PMID: 29303194 DOI: 10.1039/c7nr06860c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We report on the scanning tunneling microscopy/spectroscopy (STM/STS) study of cobalt phthalocyanine (CoPc) molecules deposited onto a back-gated graphene device. We observe a clear gate voltage (Vg) dependence of the energy position of the features originating from the molecular states. Based on the analysis of the energy shifts of the molecular features upon tuning Vg, we are able to determine the nature of the electronic states that lead to a gapped differential conductance. Our measurements show that capacitive couplings of comparable strengths exist between the CoPc molecule and the STM tip as well as between CoPc and graphene, thus facilitating electronic transport involving only unoccupied molecular states for both tunneling bias polarities. These findings provide novel information on the interaction between graphene and organic molecules and are of importance for further studies, which envisage the realization of single molecule transistors with non-metallic electrodes.
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Affiliation(s)
- Samuel Bouvron
- Department of Physics, University of Konstanz, D-78457 Konstanz, Germany.
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24
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Meier T, Pawlak R, Kawai S, Geng Y, Liu X, Decurtins S, Hapala P, Baratoff A, Liu SX, Jelínek P, Meyer E, Glatzel T. Donor-Acceptor Properties of a Single-Molecule Altered by On-Surface Complex Formation. ACS NANO 2017; 11:8413-8420. [PMID: 28731327 DOI: 10.1021/acsnano.7b03954] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Electron donor-acceptor molecules are of outstanding interest in molecular electronics and organic solar cells for their intramolecular charge transfer controlled via electrical or optical excitation. The preservation of their electronic character in the ground state upon adsorption on a surface is cardinal for their implementation in such single-molecule devices. Here, we investigate by atomic force microscopy and scanning tunneling microscopy a prototypical system consisting of a π-conjugated tetrathiafulvalene-fused dipyridophenazine molecule adsorbed on thin NaCl films on Cu(111). Depending on the adsorption site, the molecule is found either in a nearly undisturbed free state or in a bound state. In the latter case, the molecule adopts a specific adsorption site, leading to the formation of a chelate complex with a single Na+ alkali cation pulled out from the insulating film. Although expected to be electronically decoupled, the charge distribution of the complex is drastically modified, leading to the loss of the intrinsic donor-acceptor character. The chelate complex formation is reversible with respect to lateral manipulations, enabling tunable donor-acceptor molecular switches activated by on-surface coordination.
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Affiliation(s)
- Tobias Meier
- Department of Physics, University of Basel , Klingelbergstr. 82, 4056 Basel, Switzerland
| | - Rémy Pawlak
- Department of Physics, University of Basel , Klingelbergstr. 82, 4056 Basel, Switzerland
| | - Shigeki Kawai
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science , 1-1, Namiki, Tsukuba, Ibaraki 305-0044, Japan
- PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
| | - Yan Geng
- Department of Chemistry and Biochemistry, University of Bern , Freiestr. 3, 3012 Bern, Switzerland
| | - Xunshan Liu
- Department of Chemistry and Biochemistry, University of Bern , Freiestr. 3, 3012 Bern, Switzerland
| | - Silvio Decurtins
- Department of Chemistry and Biochemistry, University of Bern , Freiestr. 3, 3012 Bern, Switzerland
| | - Prokop Hapala
- Institute of Physics, Academy of Sciences of the Czech Republic , v.v.i., Cukrovarnická 10, 162 00 Prague, Czech Republic
| | - Alexis Baratoff
- Department of Physics, University of Basel , Klingelbergstr. 82, 4056 Basel, Switzerland
| | - Shi-Xia Liu
- Department of Chemistry and Biochemistry, University of Bern , Freiestr. 3, 3012 Bern, Switzerland
| | - Pavel Jelínek
- Institute of Physics, Academy of Sciences of the Czech Republic , v.v.i., Cukrovarnická 10, 162 00 Prague, Czech Republic
| | - Ernst Meyer
- Department of Physics, University of Basel , Klingelbergstr. 82, 4056 Basel, Switzerland
| | - Thilo Glatzel
- Department of Physics, University of Basel , Klingelbergstr. 82, 4056 Basel, Switzerland
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25
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Hollerer M, Lüftner D, Hurdax P, Ules T, Soubatch S, Tautz FS, Koller G, Puschnig P, Sterrer M, Ramsey MG. Charge Transfer and Orbital Level Alignment at Inorganic/Organic Interfaces: The Role of Dielectric Interlayers. ACS NANO 2017; 11:6252-6260. [PMID: 28541656 PMCID: PMC5492217 DOI: 10.1021/acsnano.7b02449] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2017] [Accepted: 05/25/2017] [Indexed: 05/17/2023]
Abstract
It is becoming accepted that ultrathin dielectric layers on metals are not merely passive decoupling layers, but can actively influence orbital energy level alignment and charge transfer at interfaces. As such, they can be important in applications ranging from catalysis to organic electronics. However, the details at the molecular level are still under debate. In this study, we present a comprehensive analysis of the phenomenon of charge transfer promoted by a dielectric interlayer with a comparative study of pentacene adsorbed on Ag(001) with and without an ultrathin MgO interlayer. Using scanning tunneling microscopy and photoemission tomography supported by density functional theory, we are able to identify the orbitals involved and quantify the degree of charge transfer in both cases. Fractional charge transfer occurs for pentacene adsorbed on Ag(001), while the presence of the ultrathin MgO interlayer promotes integer charge transfer with the lowest unoccupied molecular orbital transforming into a singly occupied and singly unoccupied state separated by a large gap around the Fermi energy. Our experimental approach allows a direct access to the individual factors governing the energy level alignment and charge-transfer processes for molecular adsorbates on inorganic substrates.
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Affiliation(s)
- Michael Hollerer
- Institute
of Physics, University of Graz, NAWI Graz, Universitätsplatz 5, 8010 Graz, Austria
| | - Daniel Lüftner
- Institute
of Physics, University of Graz, NAWI Graz, Universitätsplatz 5, 8010 Graz, Austria
| | - Philipp Hurdax
- Institute
of Physics, University of Graz, NAWI Graz, Universitätsplatz 5, 8010 Graz, Austria
| | - Thomas Ules
- Institute
of Physics, University of Graz, NAWI Graz, Universitätsplatz 5, 8010 Graz, Austria
| | - Serguei Soubatch
- Peter
Grünberg Institut (PGI-3), Forschungszentrum
Jülich, 52425 Jülich, Germany
- Fundamentals
of Future Information Technology, Jülich
Aachen Research Alliance (JARA), 52425 Jülich, Germany
| | - Frank Stefan Tautz
- Peter
Grünberg Institut (PGI-3), Forschungszentrum
Jülich, 52425 Jülich, Germany
- Fundamentals
of Future Information Technology, Jülich
Aachen Research Alliance (JARA), 52425 Jülich, Germany
| | - Georg Koller
- Institute
of Physics, University of Graz, NAWI Graz, Universitätsplatz 5, 8010 Graz, Austria
| | - Peter Puschnig
- Institute
of Physics, University of Graz, NAWI Graz, Universitätsplatz 5, 8010 Graz, Austria
| | - Martin Sterrer
- Institute
of Physics, University of Graz, NAWI Graz, Universitätsplatz 5, 8010 Graz, Austria
- E-mail:
| | - Michael G. Ramsey
- Institute
of Physics, University of Graz, NAWI Graz, Universitätsplatz 5, 8010 Graz, Austria
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26
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Off-Center Rotation of CuPc Molecular Rotor on a Bi(111) Surface and the Chiral Feature. Molecules 2017; 22:molecules22050740. [PMID: 28471385 PMCID: PMC6154302 DOI: 10.3390/molecules22050740] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 04/30/2017] [Accepted: 05/02/2017] [Indexed: 12/02/2022] Open
Abstract
Molecular rotors with an off-center axis and the chiral feature of achiral CuPc molecules on a semi-metallic Bi(111) surface have been investigated by means of a scanning tunneling microscopy (STM) at liquid nitrogen (LN2) temperature. The rotation axis of each CuPc molecular rotor is located at the end of a phthalocyanine group. As molecular coverage increases, the CuPc molecules are self-assembled into various nanoclusters and finally into two-dimensional (2D) domains, in which each CuPc molecule exhibits an apparent chiral feature. Such chiral features of the CuPc molecules can be attributed to the combined effect of asymmetric charge transfer between the CuPc and Bi(111) substrate, and the intermolecular van der Waals interactions.
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27
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Quinn T, Choudhury P. Direct oxidation of methane to methanol on single-site copper-oxo species of copper porphyrin functionalized graphene: A DFT study. MOLECULAR CATALYSIS 2017. [DOI: 10.1016/j.mcat.2017.01.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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28
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Kocić N, Decurtins S, Liu SX, Repp J. Forces from periodic charging of adsorbed molecules. J Chem Phys 2017. [DOI: 10.1063/1.4975607] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- N. Kocić
- Institute of Experimental and Applied Physics, University of Regensburg, 93053 Regensburg, Germany
| | - S. Decurtins
- Departement für Chemie und Biochemie, Universität Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - S.-X. Liu
- Departement für Chemie und Biochemie, Universität Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - J. Repp
- Institute of Experimental and Applied Physics, University of Regensburg, 93053 Regensburg, Germany
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29
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Große C, Merino P, Rosławska A, Gunnarsson O, Kuhnke K, Kern K. Submolecular Electroluminescence Mapping of Organic Semiconductors. ACS NANO 2017; 11:1230-1237. [PMID: 28085244 DOI: 10.1021/acsnano.6b08471] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The electroluminescence of organic films is the central aspect in organic light emitting diodes (OLEDs) and widely used in current display technology. However, its spatial variation on the molecular scale is essentially unexplored. Here, we address this issue by using scanning tunneling microscopy (STM) and present an in-depth study of the electroluminescence from thin C60 films (<10 monolayers) on Ag(111) and Au(111) surfaces. Similar to an OLED, the metal substrate and STM tip inject complementary charge carriers that may recombine within the molecular film; however, the atomically defined charge injection by the tip enables mapping of the local electroluminescence down to the submolecular scale. We show that the radiative recombination in solid C60 is restricted to various structural defects, whose emission characteristics can be addressed individually. The emission fine structure reveals a coupling to Jahn-Teller active vibrational modes of C60, which implies that its parity-forbidden lowest singlet transition becomes locally allowed at the emission centers. At lateral distances of a few nanometers, only a weak emission from tip-induced plasmons is detectable. Their excitation evidences the injection of both charge carrier types and confirms that they are unable to recombine radiatively at positions far from structural defects. Finally, we demonstrate that the molecular orbital pattern visible in electroluminescence maps enables an unambiguous discrimination between the intrinsic radiative recombination of electron-hole pairs in the organic film and the technique-related emission of tip-induced plasmons. This capability is essential to consolidate STM as a tool to explore the light generation from organic films on the nanoscale.
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Affiliation(s)
- Christoph Große
- Max-Planck-Institut für Festkörperforschung , Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Pablo Merino
- Max-Planck-Institut für Festkörperforschung , Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Anna Rosławska
- Max-Planck-Institut für Festkörperforschung , Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Olle Gunnarsson
- Max-Planck-Institut für Festkörperforschung , Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Klaus Kuhnke
- Max-Planck-Institut für Festkörperforschung , Heisenbergstraße 1, 70569 Stuttgart, Germany
| | - Klaus Kern
- Max-Planck-Institut für Festkörperforschung , Heisenbergstraße 1, 70569 Stuttgart, Germany
- Institut de Physique, École Polytechnique Fédérale de Lausanne , 1015 Lausanne, Switzerland
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Koslowski S, Rosenblatt D, Kabakchiev A, Kuhnke K, Kern K, Schlickum U. Adsorption and electronic properties of pentacene on thin dielectric decoupling layers. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2017; 8:1388-1395. [PMID: 28900594 PMCID: PMC5530602 DOI: 10.3762/bjnano.8.140] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 06/22/2017] [Indexed: 05/22/2023]
Abstract
With the increasing use of thin dielectric decoupling layers to study the electronic properties of organic molecules on metal surfaces, comparative studies are needed in order to generalize findings and formulate practical rules. In this paper we study the adsorption and electronic properties of pentacene deposited onto h-BN/Rh(111) and compare them with those of pentacene deposited onto KCl on various metal surfaces. When deposited onto KCl, the HOMO and LUMO energies of the pentacene molecules scale with the work functions of the combined KCl/metal surface. The magnitude of the variation between the respective KCl/metal systems indicates the degree of interaction of the frontier orbitals with the underlying metal. The results confirm that the so-called IDIS model developed by Willenbockel et al. applies not only to molecular layers on bare metal surfaces, but also to individual molecules on thin electronically decoupling layers. Depositing pentacene onto h-BN/Rh(111) results in significantly different adsorption characteristics, due to the topographic corrugation of the surface as well as the lateral electric fields it presents. These properties are reflected in the divergence from the aforementioned trend for the orbital energies of pentacene deposited onto h-BN/Rh(111), as well as in the different adsorption geometry. Thus, the highly desirable capacity of h-BN to trap molecules comes at the price of enhanced metal-molecule interaction, which decreases the HOMO-LUMO gap of the molecules. In spite of the enhanced interaction, the molecular orbitals are evident in scanning tunnelling spectroscopy (STS) and their shapes can be resolved by spectroscopic mapping.
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Affiliation(s)
- Sebastian Koslowski
- Max-Planck-Institut for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Daniel Rosenblatt
- Max-Planck-Institut for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Alexander Kabakchiev
- Max-Planck-Institut for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Klaus Kuhnke
- Max-Planck-Institut for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Klaus Kern
- Max-Planck-Institut for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
- Institut de Physique, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Uta Schlickum
- Max-Planck-Institut for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
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Sessi P, Bathon T, Kokh KA, Tereshchenko OE, Bode M. Single Electron Gating of Topological Insulators. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2016; 28:10073-10078. [PMID: 27677534 DOI: 10.1002/adma.201602413] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 08/01/2016] [Indexed: 06/06/2023]
Abstract
The effective gating of topological insulators is demonstrated, through the coupling of molecules to their surface. By using electric fields, they allow for dynamic control of the interface charge state by adding or removing single electrons. This process creates a robust transconductance bistability resembling a single-electron transistor. These findings make hybrid molecule/topological interfaces functional elements while at the same time pushing miniaturization to its ultimate limit.
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Affiliation(s)
- Paolo Sessi
- Physikalisches Institut, Experimentelle Physik II, Universität Würzburg Am Hubland, 97074, Würzburg, Germany
| | - Thomas Bathon
- Physikalisches Institut, Experimentelle Physik II, Universität Würzburg Am Hubland, 97074, Würzburg, Germany
| | - Konstantin Aleksandrovich Kokh
- V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch Russian Academy of Sciences, 630090, Novosibirsk, Russia
- Physics Department, Novosibirsk State University, 630090, Novosibirsk, Russia
- Saint-Petersburg State University, 198504, Saint-Petersburg, Russia
| | - Oleg Evgenievich Tereshchenko
- Physics Department, Novosibirsk State University, 630090, Novosibirsk, Russia
- Saint-Petersburg State University, 198504, Saint-Petersburg, Russia
- A.V. Rzanov Institute of Semiconductor Physics, Siberian Branch Russian Academy of Sciences, 630090, Novosibirsk, Russia
| | - Matthias Bode
- Physikalisches Institut, Experimentelle Physik II, Universität Würzburg Am Hubland, 97074, Würzburg, Germany
- Wilhelm Conrad Röntgen-Center for Complex Material Systems (RCCM), Am Hubland, 97074, Würzburg, Germany
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32
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Tuning charge and correlation effects for a single molecule on a graphene device. Nat Commun 2016; 7:13553. [PMID: 27886170 PMCID: PMC5133630 DOI: 10.1038/ncomms13553] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 10/14/2016] [Indexed: 01/04/2023] Open
Abstract
The ability to understand and control the electronic properties of individual molecules in a device environment is crucial for developing future technologies at the nanometre scale and below. Achieving this, however, requires the creation of three-terminal devices that allow single molecules to be both gated and imaged at the atomic scale. We have accomplished this by integrating a graphene field effect transistor with a scanning tunnelling microscope, thus allowing gate-controlled charging and spectroscopic interrogation of individual tetrafluoro-tetracyanoquinodimethane molecules. We observe a non-rigid shift in the molecule's lowest unoccupied molecular orbital energy (relative to the Dirac point) as a function of gate voltage due to graphene polarization effects. Our results show that electron–electron interactions play an important role in how molecular energy levels align to the graphene Dirac point, and may significantly influence charge transport through individual molecules incorporated in graphene-based nanodevices. The development of single-molecule electronics calls for precise tuning of the electronic properties of individual molecules that go beyond two-terminal control. Here, Wickenburg et al. show gate-tunable switch of charge states of an isolated molecule using a graphene-based field-effect transistor.
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Yu A, Li S, Czap G, Ho W. Tunneling-Electron-Induced Light Emission from Single Gold Nanoclusters. NANO LETTERS 2016; 16:5433-5436. [PMID: 27529568 DOI: 10.1021/acs.nanolett.6b01824] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The coupling of tunneling electrons with the tip-nanocluster-substrate junction plasmon was investigated by monitoring light emission in a scanning tunneling microscope (STM). Gold atoms were evaporated onto the ∼5 Å thick Al2O3 thin film grown on the NiAl (110) surface where they formed nanoclusters 3-7 nm wide. Scanning tunneling spectroscopy (STS) of these nanoclusters revealed quantum-confined electronic states. Spatially resolved photon imaging showed localized emission hot spots. Size dependent study and light emission from nanocluster dimers further support the viewpoint that coupling of tunneling electrons to the junction plasmon is the main radiative mechanism. These results showed the potential of the STM to reveal the electronic and optical properties of nanoscale metallic systems in the confined geometry of the tunnel junction.
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Affiliation(s)
- Arthur Yu
- Department of Physics and Astronomy, University of California , Irvine, California 92697-4575, United States
| | - Shaowei Li
- Department of Physics and Astronomy, University of California , Irvine, California 92697-4575, United States
| | - Gregory Czap
- Department of Physics and Astronomy, University of California , Irvine, California 92697-4575, United States
| | - W Ho
- Department of Physics and Astronomy, University of California , Irvine, California 92697-4575, United States
- Department of Chemistry, University of California , Irvine, California 92697-2025, United States
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34
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Kislitsyn DA, Mills JM, Kocevski V, Chiu SK, DeBenedetti WJI, Gervasi CF, Taber BN, Rosenfield AE, Eriksson O, Rusz J, Goforth AM, Nazin GV. Communication: Visualization and spectroscopy of defects induced by dehydrogenation in individual silicon nanocrystals. J Chem Phys 2016; 144:241102. [DOI: 10.1063/1.4954833] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Dmitry A. Kislitsyn
- Department of Chemistry and Biochemistry, Materials Science Institute, Oregon Center for Optical, Molecular and Quantum Science, University of Oregon, 1253 University of Oregon, Eugene, Oregon 97403, USA
| | - Jon M. Mills
- Department of Chemistry and Biochemistry, Materials Science Institute, Oregon Center for Optical, Molecular and Quantum Science, University of Oregon, 1253 University of Oregon, Eugene, Oregon 97403, USA
| | - Vancho Kocevski
- Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala, Sweden
| | - Sheng-Kuei Chiu
- Department of Chemistry, Portland State University, Portland, Oregon 97201, USA
| | | | - Christian F. Gervasi
- Department of Chemistry and Biochemistry, Materials Science Institute, Oregon Center for Optical, Molecular and Quantum Science, University of Oregon, 1253 University of Oregon, Eugene, Oregon 97403, USA
| | - Benjamen N. Taber
- Department of Chemistry and Biochemistry, Materials Science Institute, Oregon Center for Optical, Molecular and Quantum Science, University of Oregon, 1253 University of Oregon, Eugene, Oregon 97403, USA
| | - Ariel E. Rosenfield
- Department of Chemistry and Biochemistry, Materials Science Institute, Oregon Center for Optical, Molecular and Quantum Science, University of Oregon, 1253 University of Oregon, Eugene, Oregon 97403, USA
| | - Olle Eriksson
- Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala, Sweden
| | - Ján Rusz
- Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala, Sweden
| | - Andrea M. Goforth
- Department of Chemistry, Portland State University, Portland, Oregon 97201, USA
| | - George V. Nazin
- Department of Chemistry and Biochemistry, Materials Science Institute, Oregon Center for Optical, Molecular and Quantum Science, University of Oregon, 1253 University of Oregon, Eugene, Oregon 97403, USA
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Zhang Y, Luo Y, Zhang Y, Yu YJ, Kuang YM, Zhang L, Meng QS, Luo Y, Yang JL, Dong ZC, Hou JG. Visualizing coherent intermolecular dipole–dipole coupling in real space. Nature 2016; 531:623-7. [DOI: 10.1038/nature17428] [Citation(s) in RCA: 223] [Impact Index Per Article: 27.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 02/11/2016] [Indexed: 12/29/2022]
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Schmidt H, Giustiniano F, Eda G. Electronic transport properties of transition metal dichalcogenide field-effect devices: surface and interface effects. Chem Soc Rev 2016; 44:7715-36. [PMID: 26088725 DOI: 10.1039/c5cs00275c] [Citation(s) in RCA: 158] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Recent explosion of interest in two-dimensional (2D) materials research has led to extensive exploration of physical and chemical phenomena unique to this new class of materials and their technological potential. Atomically thin layers of group 6 transition metal dichalcogenides (TMDs) such as MoS2 and WSe2 are remarkably stable semiconductors that allow highly efficient electrostatic control due to their 2D nature. Field effect transistors (FETs) based on 2D TMDs are basic building blocks for novel electronic and chemical sensing applications. Here, we review the state-of-the-art of TMD-based FETs and summarize the current understanding of interface and surface effects that play a major role in these systems. We discuss how controlled doping is key to tailoring the electrical response of these materials and realizing high performance devices. The first part of this review focuses on some fundamental features of gate-modulated charge transport in 2D TMDs. We critically evaluate the role of surfaces and interfaces based on the data reported in the literature and explain the observed discrepancies between the experimental and theoretical values of carrier mobility. The second part introduces various non-covalent strategies for achieving desired doping in these systems. Gas sensors based on charge transfer doping and electrostatic stabilization are introduced to highlight progress in this direction. We conclude the review with an outlook on the realization of tailored TMD-based field-effect devices through surface and interface chemistry.
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Affiliation(s)
- Hennrik Schmidt
- Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546 and Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542
| | - Francesco Giustiniano
- Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546 and Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542
| | - Goki Eda
- Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546 and Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542
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37
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Sotthewes K, Heimbuch R, Zandvliet HJW. Dynamics of copper-phthalocyanine molecules on Au/Ge(001). J Chem Phys 2015; 143:134303. [PMID: 26450310 DOI: 10.1063/1.4932190] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Spatially resolved current-time scanning tunneling spectroscopy combined with current-distance spectroscopy has been used to characterize the dynamic behavior of copper-phthalocyanine (CuPc) molecules adsorbed on a Au-modified Ge(001) surface. The analyzed CuPc molecules are adsorbed in a "molecular bridge" configuration, where two benzopyrrole groups (lobes) are connected to a Au-induced nanowire, whereas the other two lobes are connected to the adjacent nanowire. Three types of lobe configurations are found: a bright lobe, a dim lobe, and a fuzzy lobe. The dim and fuzzy lobes exhibit a well-defined switching behavior between two discrete levels, while the bright lobe shows a broad oscillation band. The observed dynamic behavior is induced by electrons that are injected into the LUMO+1 orbital of the CuPc molecule. By precisely adjusting the tip-molecule distance, the switching frequency of the lobes can be tuned accurately.
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Affiliation(s)
- K Sotthewes
- Physics of Interfaces and Nanomaterials, MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands
| | - R Heimbuch
- Physics of Interfaces and Nanomaterials, MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands
| | - H J W Zandvliet
- Physics of Interfaces and Nanomaterials, MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands
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38
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Xu B, Dubi Y. Negative differential conductance in molecular junctions: an overview of experiment and theory. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:263202. [PMID: 26075799 DOI: 10.1088/0953-8984/27/26/263202] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
One of the ultimate goals of molecular electronics is to create technologies that will complement-and eventually supersede-Si-based microelectronics technologies. To reach this goal, electronic properties that mimic at least some of the electrical behaviors of today's semiconductor components must be recognized and characterized. An outstanding example for one such behavior is negative differential conductance (NDC), in which an increase in the voltage across the device terminals results in a decrease in the electric current passing through the device. This overview focuses on the NDC phenomena observed in metal-single molecule-metal molecular junctions, and is roughly divided into two parts. In the first part, the central experiments which demonstrate NDC in single-molecule junctions are critically reviewed, with emphasis on the main observations and their possible physical origins. The second part is devoted to the theory of NDC in single-molecule junctions, where simple models are employed to shed light on the different possible mechanisms leading to NDC.
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Affiliation(s)
- Bingqian Xu
- Single Molecule Study Laboratory, College of Engineering and Nanoscale Science and Engineering Center, University of Georgia, Athens, GA 30602, USA
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39
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Karan S, Jacob D, Karolak M, Hamann C, Wang Y, Weismann A, Lichtenstein AI, Berndt R. Shifting the Voltage Drop in Electron Transport Through a Single Molecule. PHYSICAL REVIEW LETTERS 2015; 115:016802. [PMID: 26182113 DOI: 10.1103/physrevlett.115.016802] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Indexed: 06/04/2023]
Abstract
A Mn-porphyrin was contacted on Au(111) in a low-temperature scanning tunneling microscope (STM). Differential conductance spectra show a zero-bias resonance that is due to an underscreened Kondo effect according to many-body calculations. When the Mn center is contacted by the STM tip, the spectrum appears to invert along the voltage axis. A drastic change in the electrostatic potential of the molecule involving a small geometric relaxation is found to cause this observation.
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Affiliation(s)
- Sujoy Karan
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - David Jacob
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle, Germany
| | - Michael Karolak
- Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Christian Hamann
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Yongfeng Wang
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Alexander Weismann
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | | | - Richard Berndt
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
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40
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Warner B, El Hallak F, Prüser H, Sharp J, Persson M, Fisher AJ, Hirjibehedin CF. Tunable magnetoresistance in an asymmetrically coupled single-molecule junction. NATURE NANOTECHNOLOGY 2015; 10:259-263. [PMID: 25622229 DOI: 10.1038/nnano.2014.326] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 12/10/2014] [Indexed: 06/04/2023]
Abstract
Phenomena that are highly sensitive to magnetic fields can be exploited in sensors and non-volatile memories. The scaling of such phenomena down to the single-molecule level may enable novel spintronic devices. Here, we report magnetoresistance in a single-molecule junction arising from negative differential resistance that shifts in a magnetic field at a rate two orders of magnitude larger than Zeeman shifts. This sensitivity to the magnetic field produces two voltage-tunable forms of magnetoresistance, which can be selected via the applied bias. The negative differential resistance is caused by transient charging of an iron phthalocyanine (FePc) molecule on a single layer of copper nitride (Cu2N) on a Cu(001) surface, and occurs at voltages corresponding to the alignment of sharp resonances in the filled and empty molecular states with the Cu(001) Fermi energy. An asymmetric voltage-divider effect enhances the apparent voltage shift of the negative differential resistance with magnetic field, which inherently is on the scale of the Zeeman energy. These results illustrate the impact that asymmetric coupling to metallic electrodes can have on transport through molecules, and highlight how this coupling can be used to develop molecular spintronic applications.
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Affiliation(s)
- Ben Warner
- 1] London Centre for Nanotechnology, University College London (UCL), London WC1H 0AH, UK [2] Department of Physics &Astronomy, UCL, London WC1E 6BT, UK
| | - Fadi El Hallak
- London Centre for Nanotechnology, University College London (UCL), London WC1H 0AH, UK
| | - Henning Prüser
- London Centre for Nanotechnology, University College London (UCL), London WC1H 0AH, UK
| | - John Sharp
- Surface Science Research Centre and Department of Chemistry, University of Liverpool, Liverpool L69 3BX, UK
| | - Mats Persson
- 1] Surface Science Research Centre and Department of Chemistry, University of Liverpool, Liverpool L69 3BX, UK [2] Department of Applied Physics, Chalmers University of Technology, SE-412 96, Göteborg, Sweden
| | - Andrew J Fisher
- 1] London Centre for Nanotechnology, University College London (UCL), London WC1H 0AH, UK [2] Department of Physics &Astronomy, UCL, London WC1E 6BT, UK
| | - Cyrus F Hirjibehedin
- 1] London Centre for Nanotechnology, University College London (UCL), London WC1H 0AH, UK [2] Department of Physics &Astronomy, UCL, London WC1E 6BT, UK [3] Department of Chemistry, UCL, London WC1H 0AJ, UK
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41
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Chiaravalloti F, Dujardin G, Riedel D. Atomic scale control of hexaphenyl molecules manipulation along functionalized ultra-thin insulating layer on the Si(1 0 0) surface at low temperature (9 K). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:054006. [PMID: 25414151 DOI: 10.1088/0953-8984/27/5/054006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Ultra-thin CaF2 layers are grown on the Si(1 0 0) surface by using a Knudsen cell evaporator. These epitaxial structures are studied with a low temperature (9 K) scanning tunneling microscope and used to electronically decouple hexaphenyl molecules from the Si surface. We show that the ultra-thin CaF2 layers exhibit stripe structures oriented perpendicularly to the silicon dimer rows and have a surface gap of 3.8 eV. The ultra-thin semi-insulating layers are also shown to be functionalized, since 80% of the hexaphenyl molecules adsorbed on these structures self-orients along the stripes. Numerical simulations using time-dependent density functional theory allow comparison of computed orbitals of the hexaphenyl molecule with experimental data. Finally, we show that the hexaphenyl molecules can be manipulated along or across the stripes, enabling the molecules to be arranged precisely on the insulating surface.
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Affiliation(s)
- Franco Chiaravalloti
- Institut des Sciences Moléculaires d'Orsay, ISMO, UMR 8214, CNRS, Université Paris Sud, 91405 Orsay Cedex, France
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42
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Cui Y, Tosoni S, Schneider WD, Pacchioni G, Nilius N, Freund HJ. Phonon-mediated electron transport through CaO thin films. PHYSICAL REVIEW LETTERS 2015; 114:016804. [PMID: 25615494 DOI: 10.1103/physrevlett.114.016804] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Indexed: 06/04/2023]
Abstract
Scanning tunneling microscopy has developed into a powerful tool for the characterization of conductive surfaces, for which the overlap of tip and sample wave functions determines the image contrast. On insulating layers, as the CaO thin film grown on Mo(001) investigated here, direct overlap between initial and final states is not enabled anymore and electrons are transported via hopping through the conduction-band states of the oxide. Carrier transport is accompanied by strong phonon excitations in this case, imprinting an oscillatory signature on the differential conductance spectra of the system. The phonons show a characteristic spatial dependence and become softer around lattice irregularities in the oxide film, such as dislocation lines.
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Affiliation(s)
- Yi Cui
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Sergio Tosoni
- Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via Cozzi 53, 20125 Milano, Italy
| | - Wolf-Dieter Schneider
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany and Ecole Polytechnique Fédérale de Lausanne, Institute of Physics, CH-1015 Lausanne, Switzerland
| | - Gianfranco Pacchioni
- Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via Cozzi 53, 20125 Milano, Italy
| | - Niklas Nilius
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany and Carl von Ossietzky Universität Oldenburg, Institut für Physik, D-26111 Oldenburg, Germany
| | - Hans-Joachim Freund
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
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43
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Kislitsyn DA, Hackley JD, Nazin GV. Vibrational Excitation in Electron Transport through Carbon Nanotube Quantum Dots. J Phys Chem Lett 2014; 5:3138-3143. [PMID: 26276325 DOI: 10.1021/jz5015967] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Electron transport in single-walled carbon nanotubes (SWCNTs) is extremely sensitive to environmental effects. SWCNTs experiencing an inhomogeneous environment are effectively subjected to a disorder potential, which can lead to localized electronic states. An important element of the physical picture of such states localized on the nanometer-scale is the existence of a local vibronic mainfold resulting from the localization-enhanced electron-vibrational coupling. In this Letter, scanning tunneling spectroscopy (STS) is used to study the quantum-confined electronic states in SWCNTs deposited on the Au(111) surface. STS spectra show the vibrational overtones identified as D-band Kekulé vibrational modes and K-point transverse out-of plane phonons. The presence of these vibrational modes in the STS spectra suggests rippling distortion and dimerization of carbon atoms on the SWCNT surface. The present study thus, for the first time, experimentally connects the properties of well-defined localized electronic states to the properties of their associated vibronic states.
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Affiliation(s)
- Dmitry A Kislitsyn
- Department of Chemistry and Biochemistry, University of Oregon, 1253 University of Oregon, Eugene, Oregon 97403, United States
| | - Jason D Hackley
- Department of Chemistry and Biochemistry, University of Oregon, 1253 University of Oregon, Eugene, Oregon 97403, United States
| | - George V Nazin
- Department of Chemistry and Biochemistry, University of Oregon, 1253 University of Oregon, Eugene, Oregon 97403, United States
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44
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Kalashnyk N, Ganesh Nagaswaran P, Kervyn S, Riello M, Moreton B, Jones TS, De Vita A, Bonifazi D, Costantini G. Self-assembly of decoupled borazines on metal surfaces: the role of the peripheral groups. Chemistry 2014; 20:11856-62. [PMID: 25079120 PMCID: PMC4449113 DOI: 10.1002/chem.201402839] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2014] [Indexed: 11/11/2022]
Abstract
Two borazine derivatives have been synthesised to investigate their self-assembly behaviour on Au(111) and Cu(111) surfaces by scanning tunnelling microscopy (STM) and theoretical simulations. Both borazines form extended 2D networks upon adsorption on both substrates at room temperature. Whereas the more compact triphenyl borazine 1 arranges into close-packed ordered molecular islands with an extremely low density of defects on both substrates, the tris(phenyl-4-phenylethynyl) derivative 2 assembles into porous molecular networks due to its longer lateral substituents. For both species, the steric hindrance between the phenyl and mesityl substituents results in an effective decoupling of the central borazine core from the surface. For borazine 1, this is enough to weaken the molecule-substrate interaction, so that the assemblies are only driven by attractive van der Waals intermolecular forces. For the longer and more flexible borazine 2, a stronger molecule-substrate interaction becomes possible through its peripheral substituents on the more reactive copper surface.
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Affiliation(s)
- Nataliya Kalashnyk
- Department of Chemistry, University of WarwickGibbet Hill Road, Coventry, CV4 7AL (UK)
| | - Praveen Ganesh Nagaswaran
- Namur Research College (NARC) and Department of Chemistry, University of Namur (UNamur)Rue de Bruxelles 61, 5000 Namur (Belgium)
| | - Simon Kervyn
- Namur Research College (NARC) and Department of Chemistry, University of Namur (UNamur)Rue de Bruxelles 61, 5000 Namur (Belgium)
| | - Massimo Riello
- Physics Department, King's College LondonLondon, WC2R 2LS (UK)
| | - Ben Moreton
- Department of Chemistry, University of WarwickGibbet Hill Road, Coventry, CV4 7AL (UK)
| | - Tim S Jones
- Department of Chemistry, University of WarwickGibbet Hill Road, Coventry, CV4 7AL (UK)
| | | | - Davide Bonifazi
- Namur Research College (NARC) and Department of Chemistry, University of Namur (UNamur)Rue de Bruxelles 61, 5000 Namur (Belgium)
- Department of Pharmaceutical and Chemical Sciences and INSTM UdR Trieste, University of TriestePiazzale Europa 1, 34127 Trieste (Italy)
| | - Giovanni Costantini
- Department of Chemistry, University of WarwickGibbet Hill Road, Coventry, CV4 7AL (UK)
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45
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Zhang ZD, Wang J. Curl flux, coherence, and population landscape of molecular systems: Nonequilibrium quantum steady state, energy (charge) transport, and thermodynamics. J Chem Phys 2014; 140:245101. [DOI: 10.1063/1.4884125] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Z. D. Zhang
- Department of Physics and Astronomy, SUNY Stony Brook, New York 11794, USA
| | - J. Wang
- Department of Physics and Astronomy, SUNY Stony Brook, New York 11794, USA
- Department of Chemistry, SUNY Stony Brook, New York 11794, USA
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, People's Republic of China
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46
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Freund HJ, Nilius N, Risse T, Schauermann S. A fresh look at an old nano-technology: catalysis. Phys Chem Chem Phys 2014; 16:8148-67. [DOI: 10.1039/c3cp55231d] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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47
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Sáfar GAM, Malachias A, Magalhães-Paniago R, Martins DCS, Idemori YM. Unravelling the molecular structure and packing of a planar molecule by combining nuclear magnetic resonance and scanning tunneling microscopy. Phys Chem Chem Phys 2013; 15:20691-7. [PMID: 24192713 DOI: 10.1039/c3cp53542h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The determination of the molecular structure of a porphyrin is achieved by using nuclear magnetic resonance (NMR) and scanning tunneling microscopy (STM) techniques. Since macroscopic crystals cannot be obtained in this system, this combination of techniques is crucial to solve the molecular structure without the need for X-ray crystallography. For this purpose, previous knowledge of the flatness of the reagent molecules (a porphyrin and its functionalizing group, a naphthalimide) and the resulting molecular structure obtained by a force-field simulation are used. The exponents of the I-V curves obtained by scanning tunneling spectroscopy (STS) allow us to check whether the thickness of the film of molecules is greater than a monolayer, even when there is no direct access to the exposed surface of the metal substrate. Photoluminescence (PL), optical absorption, infrared (IR) reflectance and solubility tests are used to confirm the results obtained here with this NMR/STM/STS combination.
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Affiliation(s)
- Gustavo A M Sáfar
- Departamento de Química, ICEx, Universidade Federal de Minas Gerais, Belo Horizonte-MG, 31270-901, Brazil.
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48
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Breitwieser R, Marsault M, Repain V, Lagoute J, Chacon C, Girard Y, Rousset S, Qin Z, Battaglini N, Zrig S, Lang P. Long-range ordered nanodomains of grafted electroactive molecules. J Chem Phys 2013; 139:204703. [PMID: 24289365 DOI: 10.1063/1.4830402] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We demonstrate the capability to build zero and one-dimensional electroactive molecular nanostructures ordered over a macroscopic scale and stable under ambient conditions. To realize these arrays, we use the selective grafting of functionalized thiols (juglon and terthiophene based) on a self-organized metallic template. The nanoscale patterning of the molecular conductance is demonstrated and analyzed by scanning tunneling spectroscopy. Finally, the influence of the nanostructuring on electro-chemical properties is measured, paving the way to an all-bottom-up fabrication of nanostructured templates for nanosciences.
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Affiliation(s)
- R Breitwieser
- MPQ, Université Paris Diderot-Paris 7, Sorbonne Paris Cité, CNRS, UMR 7162, 10 rue A. Domon et L. Duquet, 75205 Paris 13, France
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49
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Münnich G, Donarini A, Wenderoth M, Repp J. Fixing the energy scale in scanning tunneling microscopy on semiconductor surfaces. PHYSICAL REVIEW LETTERS 2013; 111:216802. [PMID: 24313511 DOI: 10.1103/physrevlett.111.216802] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Indexed: 06/02/2023]
Abstract
In scanning tunneling experiments on semiconductor surfaces, the energy scale within the tunneling junction is usually unknown due to tip-induced band bending. Here, we experimentally recover the zero point of the energy scale by combining scanning tunneling microscopy with Kelvin probe force spectroscopy. With this technique, we revisit shallow acceptors buried in GaAs. Enhanced acceptor-related conductance is observed in negative, zero, and positive band-bending regimes. An Anderson-Hubbard model is used to rationalize our findings, capturing the crossover between the acceptor state being part of an impurity band for zero band bending and the acceptor state being split off and localized for strong negative or positive band bending, respectively.
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Affiliation(s)
- Gerhard Münnich
- Institute of Experimental and Applied Physics, University of Regensburg, 93053 Regensburg, Germany
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50
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Schofield SR, Studer P, Hirjibehedin CF, Curson NJ, Aeppli G, Bowler DR. Quantum engineering at the silicon surface using dangling bonds. Nat Commun 2013; 4:1649. [PMID: 23552064 PMCID: PMC3644071 DOI: 10.1038/ncomms2679] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Accepted: 02/28/2013] [Indexed: 11/25/2022] Open
Abstract
Individual atoms and ions are now routinely manipulated using scanning tunnelling microscopes or electromagnetic traps for the creation and control of artificial quantum states. For applications such as quantum information processing, the ability to introduce multiple atomic-scale defects deterministically in a semiconductor is highly desirable. Here we use a scanning tunnelling microscope to fabricate interacting chains of dangling bond defects on the hydrogen-passivated silicon (001) surface. We image both the ground-state and the excited-state probability distributions of the resulting artificial molecular orbitals, using the scanning tunnelling microscope tip bias and tip-sample separation as gates to control which states contribute to the image. Our results demonstrate that atomically precise quantum states can be fabricated on silicon, and suggest a general model of quantum-state fabrication using other chemically passivated semiconductor surfaces where single-atom depassivation can be achieved using scanning tunnelling microscopy. The ability to add and move individual atoms on a surface with a scanning tunnelling microscope enables precise control over the electronic quantum states of the surface. Schofield et al. show that removing hydrogen atoms from a passivated silicon surface can be used to generate and control such states.
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Affiliation(s)
- S R Schofield
- London Centre for Nanotechnology, University College London, London WC1H 0AH, UK.
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