1
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Wu X, Néel N, Brandbyge M, Kröger J. Enhancement of Graphene Phonon Excitation by a Chemically Engineered Molecular Resonance. PHYSICAL REVIEW LETTERS 2023; 130:116201. [PMID: 37001107 DOI: 10.1103/physrevlett.130.116201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Accepted: 02/21/2023] [Indexed: 06/19/2023]
Abstract
The abstraction of pyrrolic hydrogen from a single phthalocyanine on graphene turns the molecule into a sensitive probe for graphene phonons. The inelastic electron transport measured with a scanning tunneling microscope across the molecular adsorbate and graphene becomes strongly enhanced for a graphene out-of-plane acoustic phonon mode. Supporting density functional and transport calculations elucidate the underlying physical mechanism. A molecular orbital resonance close to the Fermi energy controls the inelastic current while specific phonon modes of graphene are magnified due to their coupling to symmetry-equivalent vibrational quanta of the molecule.
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Affiliation(s)
- Xiaocui Wu
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
| | - Nicolas Néel
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
| | - Mads Brandbyge
- Center of Nanostructured Graphene, Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - Jörg Kröger
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
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2
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Cirera B, Wolf M, Kumagai T. Joule Heating in Single-Molecule Point Contacts Studied by Tip-Enhanced Raman Spectroscopy. ACS NANO 2022; 16:16443-16451. [PMID: 36197071 DOI: 10.1021/acsnano.2c05642] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Heating and cooling in current-carrying molecular junctions is a crucial issue in molecular electronics. The microscopic mechanism involves complex factors such as energy inputs, molecular properties, electrode materials, and molecule-electrode coupling. To gain an in-depth understanding, it is a desired experiment to assess vibrational population that represents the energy distribution stored within the molecule. Here, we demonstrate the direct observation of vibrational heating in a single C60 molecule by means of tip-enhanced Raman spectroscopy (TERS). The heating of respective vibrational modes is monitored by anti-Stokes Raman scattering in the TERS spectra. The precise control of the gap distance in the single-molecule junction allows us to reveal a qualitatively different heating mechanism in distinct electron transport regimes, namely, the tunneling and single-molecule point contact (SMPC) regimes. Strong Joule heating via inelastic electron-vibration scattering occurs in the SMPC regime, whereas optical heating is predominant in the tunneling regime. The strong Joule heating at the SMPC also leads to a pronounced red shift of the Raman peak position and line width broadening. Furthermore, by examining the SMPC with several types of contact surfaces, we show that the heating efficiency is related to the current density at the SMPC and the vibrational dissipation channels into the electrode.
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Affiliation(s)
- Borja Cirera
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195Berlin, Germany
| | - Martin Wolf
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195Berlin, Germany
| | - Takashi Kumagai
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195Berlin, Germany
- Center for Mesoscopic Sciences, Institute for Molecular Science, Okazaki444-8585, Japan
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3
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Homberg J, Weismann A, Markussen T, Berndt R. Resonance-Enhanced Vibrational Spectroscopy of Molecules on a Superconductor. PHYSICAL REVIEW LETTERS 2022; 129:116801. [PMID: 36154405 DOI: 10.1103/physrevlett.129.116801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 04/13/2022] [Accepted: 07/13/2022] [Indexed: 06/16/2023]
Abstract
Molecular vibrational spectroscopy with the scanning tunneling microscope is feasible but usually detects few vibrational modes. We harness sharp Yu-Shiba-Rusinov states observed from molecules on a superconductor to significantly enhance the vibrational signal. From a lead phthalocyanine molecule 46 vibrational peaks are resolved enabling a comparison with calculated modes. The energy resolution is improved beyond the thermal broadening limit and shifts induced by neighbor molecules or the position of the microscope tip are determined. Vice versa, spectra of vibrational modes are used to measure the effect of an electrical field on the energy of Yu-Shiba-Rusinov states. The method may help to further probe the interaction of molecules with their environment and to better understand selection rules for vibrational excitations.
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Affiliation(s)
- Jan Homberg
- 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
| | - Troels Markussen
- Synopsys Denmark, Fruebjergvej 3, Postbox 4, DK-2100 Copenhagen, Denmark
| | - Richard Berndt
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
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4
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Li P, Zhou L, Zhao C, Ju H, Gao Q, Si W, Cheng L, Hao J, Li M, Chen Y, Jia C, Guo X. Single-molecule nano-optoelectronics: insights from physics. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2022; 85:086401. [PMID: 35623319 DOI: 10.1088/1361-6633/ac7401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Accepted: 05/27/2022] [Indexed: 06/15/2023]
Abstract
Single-molecule optoelectronic devices promise a potential solution for miniaturization and functionalization of silicon-based microelectronic circuits in the future. For decades of its fast development, this field has made significant progress in the synthesis of optoelectronic materials, the fabrication of single-molecule devices and the realization of optoelectronic functions. On the other hand, single-molecule optoelectronic devices offer a reliable platform to investigate the intrinsic physical phenomena and regulation rules of matters at the single-molecule level. To further realize and regulate the optoelectronic functions toward practical applications, it is necessary to clarify the intrinsic physical mechanisms of single-molecule optoelectronic nanodevices. Here, we provide a timely review to survey the physical phenomena and laws involved in single-molecule optoelectronic materials and devices, including charge effects, spin effects, exciton effects, vibronic effects, structural and orbital effects. In particular, we will systematically summarize the basics of molecular optoelectronic materials, and the physical effects and manipulations of single-molecule optoelectronic nanodevices. In addition, fundamentals of single-molecule electronics, which are basic of single-molecule optoelectronics, can also be found in this review. At last, we tend to focus the discussion on the opportunities and challenges arising in the field of single-molecule optoelectronics, and propose further potential breakthroughs.
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Affiliation(s)
- Peihui Li
- Center of Single-Molecule Sciences, Institute of Modern Optics, Frontiers Science Center for New Organic Matter, Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology, College of Electronic Information and Optical Engineering, Nankai University, 38 Tongyan Road, Jinnan District, Tianjin 300350, People's Republic of China
| | - Li Zhou
- Center of Single-Molecule Sciences, Institute of Modern Optics, Frontiers Science Center for New Organic Matter, Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology, College of Electronic Information and Optical Engineering, Nankai University, 38 Tongyan Road, Jinnan District, Tianjin 300350, People's Republic of China
| | - Cong Zhao
- Center of Single-Molecule Sciences, Institute of Modern Optics, Frontiers Science Center for New Organic Matter, Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology, College of Electronic Information and Optical Engineering, Nankai University, 38 Tongyan Road, Jinnan District, Tianjin 300350, People's Republic of China
| | - Hongyu Ju
- Center of Single-Molecule Sciences, Institute of Modern Optics, Frontiers Science Center for New Organic Matter, Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology, College of Electronic Information and Optical Engineering, Nankai University, 38 Tongyan Road, Jinnan District, Tianjin 300350, People's Republic of China
- School of Pharmaceutical Science and Technology, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, People's Republic of China
| | - Qinghua Gao
- Center of Single-Molecule Sciences, Institute of Modern Optics, Frontiers Science Center for New Organic Matter, Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology, College of Electronic Information and Optical Engineering, Nankai University, 38 Tongyan Road, Jinnan District, Tianjin 300350, People's Republic of China
| | - Wei Si
- Center of Single-Molecule Sciences, Institute of Modern Optics, Frontiers Science Center for New Organic Matter, Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology, College of Electronic Information and Optical Engineering, Nankai University, 38 Tongyan Road, Jinnan District, Tianjin 300350, People's Republic of China
| | - Li Cheng
- Center of Single-Molecule Sciences, Institute of Modern Optics, Frontiers Science Center for New Organic Matter, Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology, College of Electronic Information and Optical Engineering, Nankai University, 38 Tongyan Road, Jinnan District, Tianjin 300350, People's Republic of China
| | - Jie Hao
- Center of Single-Molecule Sciences, Institute of Modern Optics, Frontiers Science Center for New Organic Matter, Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology, College of Electronic Information and Optical Engineering, Nankai University, 38 Tongyan Road, Jinnan District, Tianjin 300350, People's Republic of China
| | - Mengmeng Li
- Center of Single-Molecule Sciences, Institute of Modern Optics, Frontiers Science Center for New Organic Matter, Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology, College of Electronic Information and Optical Engineering, Nankai University, 38 Tongyan Road, Jinnan District, Tianjin 300350, People's Republic of China
| | - Yijian Chen
- Center of Single-Molecule Sciences, Institute of Modern Optics, Frontiers Science Center for New Organic Matter, Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology, College of Electronic Information and Optical Engineering, Nankai University, 38 Tongyan Road, Jinnan District, Tianjin 300350, People's Republic of China
| | - Chuancheng Jia
- Center of Single-Molecule Sciences, Institute of Modern Optics, Frontiers Science Center for New Organic Matter, Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology, College of Electronic Information and Optical Engineering, Nankai University, 38 Tongyan Road, Jinnan District, Tianjin 300350, People's Republic of China
- Beijing National Laboratory for Molecular Sciences, National Biomedical Imaging Center, College of Chemistry and Molecular Engineering, Peking University, 292 Chengfu Road, Haidian District, Beijing 100871, People's Republic of China
| | - Xuefeng Guo
- Center of Single-Molecule Sciences, Institute of Modern Optics, Frontiers Science Center for New Organic Matter, Tianjin Key Laboratory of Micro-Scale Optical Information Science and Technology, College of Electronic Information and Optical Engineering, Nankai University, 38 Tongyan Road, Jinnan District, Tianjin 300350, People's Republic of China
- Beijing National Laboratory for Molecular Sciences, National Biomedical Imaging Center, College of Chemistry and Molecular Engineering, Peking University, 292 Chengfu Road, Haidian District, Beijing 100871, People's Republic of China
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5
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Shein-Lumbroso O, Liu J, Shastry A, Segal D, Tal O. Quantum Flicker Noise in Atomic and Molecular Junctions. PHYSICAL REVIEW LETTERS 2022; 128:237701. [PMID: 35749205 DOI: 10.1103/physrevlett.128.237701] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2021] [Accepted: 05/02/2022] [Indexed: 06/15/2023]
Abstract
We report on a quantum form of electronic flicker noise in nanoscale conductors that contains valuable information on quantum transport. This noise is experimentally identified in atomic and molecular junctions and theoretically analyzed by considering quantum interference due to fluctuating scatterers. Using conductance, shot-noise, and flicker-noise measurements, we show that the revealed quantum flicker noise uniquely depends on the distribution of transmission channels, a key characteristic of quantum conductors. This dependence opens the door for the application of flicker noise as a diagnostic probe for fundamental properties of quantum conductors and many-body quantum effects, a role that up to now has been performed by the experimentally less-accessible shot noise.
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Affiliation(s)
- Ofir Shein-Lumbroso
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Junjie Liu
- Department of Chemistry and Centre for Quantum Information and Quantum Control, University of Toronto, 80 Saint George Street, Toronto, Ontario M5S 3H6, Canada
| | - Abhay Shastry
- Department of Chemistry and Centre for Quantum Information and Quantum Control, University of Toronto, 80 Saint George Street, Toronto, Ontario M5S 3H6, Canada
| | - Dvira Segal
- Department of Chemistry and Centre for Quantum Information and Quantum Control, University of Toronto, 80 Saint George Street, Toronto, Ontario M5S 3H6, Canada
- Department of Physics, 60 Saint George Street, University of Toronto, Toronto, Ontario M5S 1A7, Canada
| | - Oren Tal
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
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6
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Roy TR, J JDR, Sen A. Inelastic Tunnel Transport and Nanoscale Junction Thermoelectricity with Varying Electrode Topology. ADVANCED THEORY AND SIMULATIONS 2021. [DOI: 10.1002/adts.202100054] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Talem Rebeda Roy
- SRM Research Institute and Department of Physics & Nanotechnology SRM Institute of Science and Technology Chennai Tamil Nadu 603203 India
| | - John Donald Raj J
- SRM Research Institute and Department of Physics & Nanotechnology SRM Institute of Science and Technology Chennai Tamil Nadu 603203 India
| | - Arijit Sen
- SRM Research Institute and Department of Physics & Nanotechnology SRM Institute of Science and Technology Chennai Tamil Nadu 603203 India
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7
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Gu L, Wu R. Density functional study of relaxation of adsorbate vibration modes: Dominance of anharmonic interaction. J Chem Phys 2020; 153:184109. [PMID: 33187426 DOI: 10.1063/5.0027915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Formulation and density functional workflow for calculating the lifetime of vibrational modes of molecular adsorbates on solid surfaces due to vibration-phonon coupling are presented. The anharmonic coupling is invoked to give the correct description of the origin of temperature dependence. Using pyrrolidine (C4H9N) absorbed on the Cu(001) surface as a concrete example, we show that the anharmonic coupling can be one to two orders more significant than the harmonic interaction for the broadening of vibrational spectra, especially as temperature increases. These results challenge the common assumption that the anharmonic interaction is weak and call for attention of considering its effect in quantum relaxation and related problems.
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Affiliation(s)
- Lei Gu
- Department of Physics and Astronomy, University of California, Irvine, California 92697, USA
| | - Ruqian Wu
- Department of Physics and Astronomy, University of California, Irvine, California 92697, USA
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8
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Liu S, Fu R, Li G. Exploring the mechanism of olfactory recognition in the initial stage by modeling the emission spectrum of electron transfer. PLoS One 2020; 15:e0217665. [PMID: 31923248 PMCID: PMC6953861 DOI: 10.1371/journal.pone.0217665] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 11/29/2019] [Indexed: 11/19/2022] Open
Abstract
Olfactory sense remains elusive regarding the primary reception mechanism. Some studies suggest that olfaction is a spectral sense, the olfactory event is triggered by electron transfer (ET) across the odorants at the active sites of odorant receptors (ORs). Herein we present a Donor-Bridge-Acceptor model, proposing that the ET process can be viewed as an electron hopping from the donor molecule to the odorant molecule (Bridge), then hopping off to the acceptor molecule, making the electronic state of the odorant molecule change along with vibrations (vibronic transition). The odorant specific parameter, Huang–Rhys factor can be derived from ab initio calculations, which make the simulation of ET spectra achievable. In this study, we revealed that the emission spectra (after Gaussian convolution) can be acted as odor characteristic spectra. Using the emission spectrum of ET, we were able to reasonably interpret the similar bitter-almond odors among hydrogen cyanide, benzaldehyde and nitrobenzene. In terms of isotope effects, we succeeded in explaining why subjects can easily distinguish cyclopentadecanone from its fully deuterated analogue cyclopentadecanone-d28 but not distinguishing acetophenone from acetophenone-d8.
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Affiliation(s)
- Shu Liu
- Department of Anatomy, Anhui Medical University, Hefei, Anhui, China
- * E-mail:
| | - Rao Fu
- Department of Anatomy, School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Guangwu Li
- Department of Anatomy, Anhui Medical University, Hefei, Anhui, China
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9
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Montes E, Foti G, Vázquez H. Crossover in the inelastic electron tunneling spectra of conjugated molecules with direct Au-C links. Phys Chem Chem Phys 2019; 21:1564-1571. [PMID: 30620028 DOI: 10.1039/c8cp06290k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We use inelastic electron tunneling spectroscopy (IETS) first-principles simulations to identify and characterize the different vibrational modes of single conjugated molecules bonded to Au metal electrodes. The molecules are polyphenyls (with 1 to 4 benzene units) bonded to Au via highly conducting direct Au-C bonds. The short molecule shows near resonant elastic transmission, with a crossover to tunneling for the longer backbones. The calculated inelastic spectra exhibit dips in the IETS signal of the short molecule and peaks for the longer molecules. We characterize the symmetry of vibrational modes and scattering states and discuss the changes with increasing length, where the inelastic signal of different modes can be amplified, quenched or present a crossover as more benzene units are added to the molecular backbone. This analysis rationalizes the observed trends as a function of molecular length and illustrates the role of electronic and vibrational properties on Au-C bonded molecular junctions.
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Affiliation(s)
- Enrique Montes
- Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, Prague 16200, Czech Republic.
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10
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Tsuji Y, Yoshizawa K. Effects of electron-phonon coupling on quantum interference in polyenes. J Chem Phys 2018; 149:134115. [DOI: 10.1063/1.5048955] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Yuta Tsuji
- Institute for Materials Chemistry and Engineering and IRCCS, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan
| | - Kazunari Yoshizawa
- Institute for Materials Chemistry and Engineering and IRCCS, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan
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11
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Sakai A. Admittance of Atomic and Molecular Junctions and Their Signal Transmission. MICROMACHINES 2018; 9:E320. [PMID: 30424253 PMCID: PMC6082278 DOI: 10.3390/mi9070320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 06/16/2018] [Accepted: 06/20/2018] [Indexed: 06/09/2023]
Abstract
Atom-sized contacts of metals are usually characterized by their direct current (DC) conductance. However, when atom-sized contacts are used as device interconnects and transmit high frequency signals or fast pulses, the most critical parameter is not their DC conductance but their admittance Y(ω), in particular its imaginary part ImY(ω). In this article, I will present a brief survey of theoretical and experimental results on the magnitude of Y(ω) for atom-sized contacts of metals. Theoretical contact models are first described and followed by numerical evaluation of ImY(ω) based on these models. As for experiments on Y(ω), previous experiments conducted under time-varying biases are surveyed, and then the results of direct signal transmission through atom-sized contacts are discussed. Both theoretical and experimental results indicate that ImY(ω) is negligibly small for typical atom-sized contacts for signal frequencies up to 1 GHz.
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Affiliation(s)
- Akira Sakai
- Graduate School of Engineering, Kyoto University, Kyoto 6158540, Japan.
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12
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Abstract
The oscillation frequencies of a molecule on a surface are determined by the mass distribution in the molecule and the restoring forces that occur when the molecule bends. The restoring force originates from the atomic-scale interaction within the molecule and with the surface, which plays an essential role in the dynamics and reactivity of the molecule. In 1998, a combination of scanning tunneling microscopy with inelastic tunneling spectroscopy revealed the vibrational frequencies of single molecules adsorbed on a surface. However, the probe tip itself exerts forces on the molecule, changing its oscillation frequencies. Here, we combine atomic force microscopy with inelastic tunneling spectroscopy and measure the influence of the forces exerted by the tip on the lateral vibrational modes of a carbon monoxide molecule on a copper surface. Comparing the experimental data to a mechanical model of the vibrating molecule shows that the bonds within the molecule and with the surface are weakened by the proximity of the tip. This combination of techniques can be applied to analyze complex molecular vibrations and the mechanics of forming and loosening chemical bonds, as well as to study the mechanics of bond breaking in chemical reactions and atomic manipulation.
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13
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Isshiki Y, Matsuzawa Y, Fujii S, Kiguchi M. Investigation on Single-Molecule Junctions Based on Current⁻Voltage Characteristics. MICROMACHINES 2018; 9:mi9020067. [PMID: 30393343 PMCID: PMC6187306 DOI: 10.3390/mi9020067] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Revised: 01/30/2018] [Accepted: 01/31/2018] [Indexed: 12/17/2022]
Abstract
The relationship between the current through an electronic device and the voltage across its terminals is a current–voltage characteristic (I–V) that determine basic device performance. Currently, I–V measurement on a single-molecule scale can be performed using break junction technique, where a single molecule junction can be prepared by trapping a single molecule into a nanogap between metal electrodes. The single-molecule I–Vs provide not only the device performance, but also reflect information on energy dispersion of the electronic state and the electron-molecular vibration coupling in the junction. This mini review focuses on recent representative studies on I–Vs of the single molecule junctions that cover investigation on the single-molecule diode property, the molecular vibration, and the electronic structure as a form of transmission probability, and electronic density of states, including the spin state of the single-molecule junctions. In addition, thermoelectronic measurements based on I–Vs and identification of the charged carriers (i.e., electrons or holes) are presented. The analysis in the single-molecule I–Vs provides fundamental and essential information for a better understanding of the single-molecule science, and puts the single molecule junction to more practical use in molecular devices.
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Affiliation(s)
- Yuji Isshiki
- Department of Chemistry, Graduate School of Science, Tokyo Institute of Technology, 2-12-1 W4-10 Ookayama, Meguro-ku, Tokyo 152-8551, Japan.
| | - Yuya Matsuzawa
- Department of Chemistry, Graduate School of Science, Tokyo Institute of Technology, 2-12-1 W4-10 Ookayama, Meguro-ku, Tokyo 152-8551, Japan.
| | - Shintaro Fujii
- Department of Chemistry, Graduate School of Science, Tokyo Institute of Technology, 2-12-1 W4-10 Ookayama, Meguro-ku, Tokyo 152-8551, Japan.
| | - Manabu Kiguchi
- Department of Chemistry, Graduate School of Science, Tokyo Institute of Technology, 2-12-1 W4-10 Ookayama, Meguro-ku, Tokyo 152-8551, Japan.
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14
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Weber D, Scheer E. Superconducting properties of lithographic lead break junctions. NANOTECHNOLOGY 2018; 29:045703. [PMID: 29125473 DOI: 10.1088/1361-6528/aa99b8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We have fabricated mechanically controlled break junction samples made of lead (Pb) by means of state-of-the-art nanofabrication methods: electron beam lithography and physical vapour deposition. The electrical and magnetic properties were characterized in a [Formula: see text] cryostat and showed a hard superconducting gap. Temperature and magnetic field dependence of tunnel contacts were compared and quantitatively described by including either thermal broadening of the density of states or pair breaking in the framework of a Skalski model, respectively. We show point contact spectra of few-atom contacts and present tunneling spectra exhibiting a superconducting double-gap structure.
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Affiliation(s)
- David Weber
- Universitätsstr. 10, D-78464 Konstanz, Germany
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15
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de la Torre B, Švec M, Foti G, Krejčí O, Hapala P, Garcia-Lekue A, Frederiksen T, Zbořil R, Arnau A, Vázquez H, Jelínek P. Submolecular Resolution by Variation of the Inelastic Electron Tunneling Spectroscopy Amplitude and its Relation to the AFM/STM Signal. PHYSICAL REVIEW LETTERS 2017; 119:166001. [PMID: 29099201 DOI: 10.1103/physrevlett.119.166001] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Indexed: 05/27/2023]
Abstract
Here we show scanning tunneling microscopy (STM), noncontact atomic force microscopy (AFM), and inelastic electron tunneling spectroscopy (IETS) measurements on an organic molecule with a CO-terminated tip at 5 K. The high-resolution contrast observed simultaneously in all channels unambiguously demonstrates the common imaging mechanism in STM/AFM/IETS, related to the lateral bending of the CO-functionalized tip. The IETS spectroscopy reveals that the submolecular contrast at 5 K consists of both renormalization of vibrational frequency and variation of the amplitude of the IETS signal. This finding is also corroborated by first principles simulations. We extend accordingly the probe-particle AFM/STM/IETS model to include these two main ingredients necessary to reproduce the high-resolution IETS contrast. We also employ the first principles simulations to get more insight into a different response of frustrated translation and rotational modes of the CO tip during imaging.
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Affiliation(s)
- Bruno de la Torre
- Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i., Cukrovarnická 10, 162 00 Prague, Czech Republic
- Regional Centre of Advanced Technologies and Materials, Palacký University, Šlechtitelů 27, 78371 Olomouc, Czech Republic
| | - Martin Švec
- Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i., Cukrovarnická 10, 162 00 Prague, Czech Republic
- Regional Centre of Advanced Technologies and Materials, Palacký University, Šlechtitelů 27, 78371 Olomouc, Czech Republic
| | - Giuseppe Foti
- Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i., Cukrovarnická 10, 162 00 Prague, Czech Republic
| | - Ondřej Krejčí
- Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i., Cukrovarnická 10, 162 00 Prague, Czech Republic
- Faculty of Mathematics and Physics, Department of Surface and Plasma Science, Charles University, V Holešovičkách 2, 180 00 Prague, Czech Republic
| | - Prokop Hapala
- Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i., Cukrovarnická 10, 162 00 Prague, Czech Republic
| | - Aran Garcia-Lekue
- Donostia International Physics Center (DIPC), Paseo Manuel Lardizabal 4, E-20018 San Sebastian, Spain
- Ikerbasque, Basque Foundation for Science, 48013 Bilbao, Spain
| | - Thomas Frederiksen
- Donostia International Physics Center (DIPC), Paseo Manuel Lardizabal 4, E-20018 San Sebastian, Spain
- Ikerbasque, Basque Foundation for Science, 48013 Bilbao, Spain
| | - Radek Zbořil
- Regional Centre of Advanced Technologies and Materials, Palacký University, Šlechtitelů 27, 78371 Olomouc, Czech Republic
| | - Andres Arnau
- Donostia International Physics Center (DIPC), Paseo Manuel Lardizabal 4, E-20018 San Sebastian, Spain
| | - Héctor Vázquez
- Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i., Cukrovarnická 10, 162 00 Prague, Czech Republic
| | - Pavel Jelínek
- Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i., Cukrovarnická 10, 162 00 Prague, Czech Republic
- Regional Centre of Advanced Technologies and Materials, Palacký University, Šlechtitelů 27, 78371 Olomouc, Czech Republic
- Donostia International Physics Center (DIPC), Paseo Manuel Lardizabal 4, E-20018 San Sebastian, Spain
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16
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Sýkora R, Novotný T. Graph-theoretical evaluation of the inelastic propensity rules for molecules with destructive quantum interference. J Chem Phys 2017; 146:174114. [DOI: 10.1063/1.4981916] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
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17
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Affiliation(s)
- Tim Hansen
- Nano-Science Center and Department of Chemistry, The University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - Gemma C. Solomon
- Nano-Science Center and Department of Chemistry, The University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - Thorsten Hansen
- Nano-Science Center and Department of Chemistry, The University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
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18
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Li BL, Chen KQ. Huge inelastic current at low temperature in graphene nanoribbons. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:075301. [PMID: 28032608 DOI: 10.1088/1361-648x/aa530a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The nonequilibrium Green's function and the generalized lowest-order expansion method with consideration of electron-phonon interactions (EPIs) are used to investigate the spin-dependent electronic transport properties of ferromagnetic zigzag graphene nanoribbons. Results show that the consideration of EPIs will lead to a 4-5 orders of magnitude increase of the current in some bias regions when the spin polarizations of two electrodes are antiparallel. This results in the vanishing of the dual spin filtration effect and a narrowing of the effective bias region of giant magnetoresistance. The increases of the current mainly from the first Born scattering process, and can be described by the Fermi's golden rule, and may be a result of the breaking of the structural symmetry by the introduction of phonons.
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Affiliation(s)
- Bo-Lin Li
- Department of Applied Physics, School of Physics and Electronics, Hunan University, Changsha 410082, People's Republic of China
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19
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Guo J, Bian K, Lin Z, Jiang Y. Perspective: Structure and dynamics of water at surfaces probed by scanning tunneling microscopy and spectroscopy. J Chem Phys 2017; 145:160901. [PMID: 27802647 DOI: 10.1063/1.4964668] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The detailed and precise understanding of water-solid interaction largely relies on the development of atomic-scale experimental techniques, among which scanning tunneling microscopy (STM) has proven to be a noteworthy example. In this perspective, we review the recent advances of STM techniques in imaging, spectroscopy, and manipulation of water molecules. We discuss how those newly developed techniques are applied to probe the structure and dynamics of water at solid surfaces with single-molecule and even submolecular resolution, paying particular attention to the ability of accessing the degree of freedom of hydrogen. In the end, we present an outlook on the directions of future STM studies of water-solid interfaces as well as the challenges faced by this field. Some new scanning probe techniques beyond STM are also envisaged.
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Affiliation(s)
- Jing Guo
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | - Ke Bian
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | - Zeren Lin
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | - Ying Jiang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, People's Republic of China
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20
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Han Z, Czap G, Xu C, Chiang CL, Yuan D, Wu R, Ho W. Probing Intermolecular Coupled Vibrations between Two Molecules. PHYSICAL REVIEW LETTERS 2017; 118:036801. [PMID: 28157347 DOI: 10.1103/physrevlett.118.036801] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Indexed: 06/06/2023]
Abstract
Intermolecular interactions can induce energy shifts and coupling of molecular vibrations. However, the detection of intermolecular coupled vibrations has not been reported at the single molecule level. Here we detected an intermolecular coupled vibration between two CO molecules, one on the surface and another on the tip within the gap of a subkelvin scanning tunneling microscope, and analyzed the results by density functional calculations. We attribute the evolution of the energy and intensity of this coupled vibration as a function of tip-sample distance to the tilting and orbital alignment of the two CO molecules.
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Affiliation(s)
- Zhumin Han
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, USA
| | - Gregory Czap
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, USA
| | - Chen Xu
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, USA
| | - Chi-Lun Chiang
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, USA
| | - Dingwang Yuan
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, USA
- Center for High Resolution Electron Microscopy, College of Materials Science and Engineering, Hunan University, Changsha 410082, China
| | - Ruqian Wu
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, USA
| | - W Ho
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, USA
- Department of Chemistry, University of California, Irvine, California 92697-2025, USA
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21
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Meierott S, Néel N, Kröger J. Spectroscopic Line Shapes of Vibrational Quanta in the Presence of Molecular Resonances. J Phys Chem Lett 2016; 7:2388-2393. [PMID: 27280313 DOI: 10.1021/acs.jpclett.6b00923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Line shapes of molecular vibrational quanta in inelastic electron tunneling spectroscopy may indicate the strength of electron-vibration coupling, the hybridization of the molecule with its environment, and the degree of vibrational damping by electron-hole pair excitation. Bare as well as C60-terminated Pb tips of a scanning tunneling microscope and clean as well as C60-covered Pb(111) surfaces were used in low-temperature experiments. Depending on the overlap of orbital and vibrational spectral ranges different spectroscopic line shapes of molecular vibrational quanta were observed. The energy range covered by the molecular resonance was altered by modifying the adsorption configuration of the molecule terminating the tip apex. Concomitantly, the line shapes of different vibrational modes were affected. The reported observations represent an experimental proof to theoretical predictions on the contribution from resonant processes to inelastic electron tunneling.
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Affiliation(s)
- Stefan Meierott
- Institut für Physik, Technische Universität Ilmenau , D-98693 Ilmenau, Germany
| | - Nicolas Néel
- Institut für Physik, Technische Universität Ilmenau , D-98693 Ilmenau, Germany
| | - Jörg Kröger
- Institut für Physik, Technische Universität Ilmenau , D-98693 Ilmenau, Germany
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22
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Xu C, Chiang CL, Han Z, Ho W. Nature of Asymmetry in the Vibrational Line Shape of Single-Molecule Inelastic Electron Tunneling Spectroscopy with the STM. PHYSICAL REVIEW LETTERS 2016; 116:166101. [PMID: 27152811 DOI: 10.1103/physrevlett.116.166101] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Indexed: 06/05/2023]
Abstract
Single molecule vibrational spectroscopy and microscopy was demonstrated in 1998 by inelastic electron tunneling with the scanning tunneling microscope. To date, the discussion of its application has mainly focused on the spatial resolution and the spectral energy and intensity. Here we report on the vibrational line shape for a single carbon monoxide molecule that qualitatively exhibits inversion symmetry when it is transferred from the surface to the tip. The dependence of the line shape on the molecule's asymmetric couplings in the tunnel junction can be understood from theoretical simulation and further validates the mechanisms of inelastic electron tunneling.
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Affiliation(s)
- Chen Xu
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, USA
| | - Chi-Lun Chiang
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, USA
| | - Zhumin Han
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, USA
| | - W Ho
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, USA
- Department of Chemistry, University of California, Irvine, California 92697-2025, USA
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23
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Mehlhorn M, Morgenstern K. Physisorption versus chemisorption of oxygen molecules on Ag(100). J Chem Phys 2016; 144:134706. [PMID: 27059584 DOI: 10.1063/1.4945339] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We compare the adsorption of oxygen molecules on Ag(100) at 60 K and at 100 K. At both temperatures, the molecules form islands. Differences between the species adsorbed at the two temperatures in both low-temperature scanning tunneling microscopy and inelastic electron tunneling spectroscopy are attributed to two different adsorption states, a chemisorbed state after 100 K adsorption and a physisorbed state after 60 K adsorption.
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Affiliation(s)
- Michael Mehlhorn
- Institut für Festkörperphysik, Abteilung ATMOS, Leibniz Universität Hannover, Appelstrasse 2, D-30167 Hannover, Germany
| | - Karina Morgenstern
- Lehrstuhl für Physikalische Chemie I, Ruhr-Universität Bochum, D-44780 Bochum, Germany
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24
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Yu X, Lovrincic R, Sepunaru L, Li W, Vilan A, Pecht I, Sheves M, Cahen D. Insights into Solid-State Electron Transport through Proteins from Inelastic Tunneling Spectroscopy: The Case of Azurin. ACS NANO 2015; 9:9955-63. [PMID: 26381112 DOI: 10.1021/acsnano.5b03950] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Surprisingly efficient solid-state electron transport has recently been demonstrated through "dry" proteins (with only structural, tightly bound H2O left), suggesting proteins as promising candidates for molecular (bio)electronics. Using inelastic electron tunneling spectroscopy (IETS), we explored electron-phonon interaction in metal/protein/metal junctions, to help understand solid-state electronic transport across the redox protein azurin. To that end an oriented azurin monolayer on Au is contacted by soft Au electrodes. Characteristic vibrational modes of amide and amino acid side groups as well as of the azurin-electrode contact were observed, revealing the azurin native conformation in the junction and the critical role of side groups in the charge transport. The lack of abrupt changes in the conductance and the line shape of IETS point to far off-resonance tunneling as the dominant transport mechanism across azurin, in line with previously reported (and herein confirmed) azurin junctions. The inelastic current and hence electron-phonon interaction appear to be rather weak and comparable in magnitude with the inelastic fraction of tunneling current via alkyl chains, which may reflect the known structural rigidity of azurin.
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Affiliation(s)
| | - Robert Lovrincic
- Institute for High Frequency Technology, TU Braunschweig, and Innovationlab , Speyerer Str. 4, 69115 Heidelberg, Germany
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25
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Tian G, Duan S, Zhang GP, Hu W, Luo Y. The effect of Duschinsky rotation on charge transport properties of molecular junctions in the sequential tunneling regime. Phys Chem Chem Phys 2015; 17:23007-16. [PMID: 26272223 DOI: 10.1039/c5cp02736e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We present here a systematic theoretical study on the effect of Duschinsky rotation on charge transport properties of molecular junctions in the sequential tunneling regime. In the simulations we assume that only two electronic charging states each coupled to a two dimensional vibrational potential energy surface (PES) are involved in the transport process. The Duschinsky rotation effect is accounted by varying the rotational angle between the two sets of displaced PESs. Both harmonic potential and anharmonic Morse potential have been considered for the cases of the intermediate to strong electron-vibration couplings. Our calculations show that the inclusion of the Duschinsky rotation effect can significantly change the charge transport properties of a molecular junction. Such an effect makes the otherwise symmetric Coulomb diamond become asymmetric in harmonic potentials. Depending on the angle of the rotation, the low bias current could be significantly suppressed or enhanced. This effect is particularly prominent in the Franck-Condon (FC) blockade regime where the electron-vibration coupling is strong. These changes are caused by the variation of the FC factors which are closely related to the rotational angle between the two sets of PESs involved in the charge transport process. For a molecular junction with Morse potentials, the changes caused by Duschinsky rotation are much more complicated. Both the amplitude and shape of the Coulomb diamond are closely dependent on the rotational angle in the whole range from 0 to 2π. One interesting result is that with a rotation angle of π (and also π/2 for certain cases) symmetric Coulomb diamonds can even be formed from the intrinsically asymmetric Morse potential. These results could be important for the interpretation of experimental observations.
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Affiliation(s)
- Guangjun Tian
- Department of Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology, SE-106 91 Stockholm, Sweden.
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26
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Zhang Y, Yam C, Chen G. A variational approach for dissipative quantum transport in a wide parameter space. J Chem Phys 2015; 143:104112. [PMID: 26619516 DOI: 10.1063/1.4930847] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Recent development of theoretical method for dissipative quantum transport has achieved notable progresses in the weak or strong electron-phonon coupling regime. However, a generalized theory for dissipative quantum transport in a wide parameter space had not been established. In this work, a variational polaron theory for dissipative quantum transport in a wide range of electron-phonon coupling is developed. The optimal polaron transformation is determined by the optimization of the Feynman-Bogoliubov upper bound of free energy. The free energy minimization ends up with an optimal mean-field Hamiltonian and a minimal interaction Hamiltonian. Hence, second-order perturbation can be applied to the transformed system, resulting in an accurate and efficient method for the treatment of dissipative quantum transport with different electron-phonon coupling strength. Numerical benchmark calculation on a single site model coupled to one phonon mode is presented.
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27
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Zhang Y, Yam C, Chen G. Dissipative time-dependent quantum transport theory: Quantum interference and phonon induced decoherence dynamics. J Chem Phys 2015; 142:164101. [DOI: 10.1063/1.4918771] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Yu Zhang
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - ChiYung Yam
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
- Beijing Computational Science Research Center, Beijing 100084, China
| | - GuanHua Chen
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
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28
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Lu SY, Lin JS. A nano Ag 5 cluster tip probing the vertical transfer of CO (ads) adsorbed on Ag(110) with simulated inelastic electron tunneling spectroscopy. RSC Adv 2015. [DOI: 10.1039/c5ra06728f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A nano Ag5 tip probing the transfer of CO(ads) on Ag(110) surface is investigated with simulated inelastic electron tunneling spectroscopy generated by combining DFT-based MD simulations with a FT-ACF of the derivative of local density of states.
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Affiliation(s)
- Shao-Yu Lu
- Department of Chemistry
- Tamkang University
- Tamsui
- Taiwan 25137
| | - Jyh-Shing Lin
- Department of Chemistry
- Tamkang University
- Tamsui
- Taiwan 25137
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29
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Ding Z, Sun Z, Li G, Meng F, Wu M, Ma Y, Chen X. The inelastic electron tunneling spectroscopy of curved finite-sized graphene nanoribbon based molecular devices. RSC Adv 2015. [DOI: 10.1039/c5ra09727d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The inelastic electron scattering properties of the molecular devices of curved finite-sized graphene nanoribbon (GNR) slices have been studied by combining the density functional theory and Green's function method.
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Affiliation(s)
- Zongling Ding
- School of Physics and Material Science
- Anhui University
- Hefei, China
- Co-operative Innovation Research Center for Weak Signal-Detecting Materials and Devices Integration
- Anhui University
| | - Zhaoqi Sun
- School of Physics and Material Science
- Anhui University
- Hefei, China
| | - Guang Li
- School of Physics and Material Science
- Anhui University
- Hefei, China
| | - Fanming Meng
- School of Physics and Material Science
- Anhui University
- Hefei, China
| | - Mingzai Wu
- School of Physics and Material Science
- Anhui University
- Hefei, China
| | - Yongqing Ma
- School of Physics and Material Science
- Anhui University
- Hefei, China
| | - Xiaoshuang Chen
- National Lab. of Infrared Physics
- Shanghai Institute for Technical Physics
- Chinese Academy of Sciences
- Shanghai, China
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30
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Motobayashi K, Kim Y, Arafune R, Ohara M, Ueba H, Kawai M. Dissociation pathways of a single dimethyl disulfide on Cu(111): Reaction induced by simultaneous excitation of two vibrational modes. J Chem Phys 2014; 140:194705. [DOI: 10.1063/1.4875537] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
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31
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Ben-Zvi R, Vardimon R, Yelin T, Tal O. Electron-vibration interaction in multichannel single-molecule junctions. ACS NANO 2013; 7:11147-55. [PMID: 24252112 DOI: 10.1021/nn404873x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The effect of electron-vibration interaction in atomic-scale junctions with a single conduction channel was widely investigated both theoretically and experimentally. However, the more general case of junctions with several conduction channels has received very little attention. Here we study electron-vibration interaction in multichannel molecular junctions, formed by introduction of either benzene or carbon dioxide between platinum electrodes. By combining shot noise and differential conductance measurements, we analyze the effect of vibration activation on conductance in view of the distribution of conduction channels. Based on the shift of vibration energy while the junction is stretched, we identify vibration modes with transverse and longitudinal symmetry. The detection of different vibration modes is ascribed to efficient vibration coupling to different conduction channels according to symmetry considerations. While most of our observations can be explained in view of the theoretical models for a single conduction channel, the appearance of conductance enhancement, induced by electron-vibration interaction, at high conductance values indicates either unexpected high electron-vibration coupling or interchannel scattering.
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Affiliation(s)
- Regev Ben-Zvi
- Department of Chemical Physics, Weizmann Institute of Science , Rehovot, 76100 Israel
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32
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Lykkebo J, Gagliardi A, Pecchia A, Solomon GC. Strong overtones modes in inelastic electron tunneling spectroscopy with cross-conjugated molecules: a prediction from theory. ACS NANO 2013; 7:9183-94. [PMID: 24067128 PMCID: PMC3807527 DOI: 10.1021/nn4037915] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Accepted: 09/19/2013] [Indexed: 05/31/2023]
Abstract
Cross-conjugated molecules are known to exhibit destructive quantum interference, a property that has recently received considerable attention in single-molecule electronics. Destructive quantum interference can be understood as an antiresonance in the elastic transmission near the Fermi energy and leading to suppressed levels of elastic current. In most theoretical studies, only the elastic contributions to the current are taken into account. In this paper, we study the inelastic contributions to the current in cross-conjugated molecules and find that while the inelastic contribution to the current is larger than for molecules without interference, the overall behavior of the molecule is still dominated by the quantum interference feature. Second, an ongoing challenge for single molecule electronics is understanding and controlling the local geometry at the molecule-surface interface. With this in mind, we investigate a spectroscopic method capable of providing insight into these junctions for cross-conjugated molecules: inelastic electron tunneling spectroscopy (IETS). IETS has the advantage that the molecule interface is probed directly by the tunneling current. Previously, it has been thought that overtones are not observable in IETS. Here, overtones are predicted to be strong and, in some cases, the dominant spectroscopic features. We study the origin of the overtones and find that the interference features in these molecules are the key ingredient. The interference feature is a property of the transmission channels of the π system only, and consequently, in the vicinity of the interference feature, the transmission channels of the σ system and the π system become equally transmissive. This allows for scattering between the different transmission channels, which serves as a pathway to bypass the interference feature. A simple model calculation is able to reproduce the results obtained from atomistic calculations, and we use this to interpret these findings.
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Affiliation(s)
- Jacob Lykkebo
- Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark
| | - Alessio Gagliardi
- Department of Electronic Engineering, Università di Roma “Tor Vergata”, Via del Politecnico 1, 00133 Rome, Italy
| | - Alessandro Pecchia
- Consiglio Nazionale delle Ricerche, ISMN, Via Salaria km 29.6, 00017 Monterotondo, Rome, Italy
| | - Gemma C. Solomon
- Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark
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33
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Kaneko S, Motta C, Brivio GP, Kiguchi M. Mechanically controllable bi-stable states in a highly conductive single pyrazine molecular junction. NANOTECHNOLOGY 2013; 24:315201. [PMID: 23851468 DOI: 10.1088/0957-4484/24/31/315201] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We report the fabrication of a highly conductive single pyrazine molecular junction with Pt leads. Mechanically controllable break-junction measurements at low temperatures show two distinct high and low conductance states. These conductance values are two orders of magnitude larger than those of a conventional single molecular junction with anchoring groups because of direct binding of the π conjugated molecule to a metal electrode with large density of states at the Fermi energy. Inelastic electron tunneling spectroscopy combined with density functional theory calculations highlights the vibration modes of the system for the two regimes. Theory allows us to assign the high and low conductance states of the molecular junction to two configurations in which the pyrazine axis is tilted and parallel with respect to the junction axis, respectively. Finally, we show that the pyrazine junction can be reversibly switched between the two bi-stable conductance states by mechanically stretching and relaxing the junction.
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Affiliation(s)
- Satoshi Kaneko
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan
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34
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Burema SR, Seufert K, Auwärter W, Barth JV, Bocquet ML. Probing nitrosyl ligation of surface-confined metalloporphyrins by inelastic electron tunneling spectroscopy. ACS NANO 2013; 7:5273-81. [PMID: 23718257 PMCID: PMC3833350 DOI: 10.1021/nn4010582] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Complexes obtained by the ligation of nitric oxide (NO) to metalloporphyrins represent important model systems with biological relevance. Herein we report a molecular-level investigation of surface-confined cobalt tetraphenyl porphyrin (Co-TPP) species and their interaction with NO under ultrahigh vacuum conditions. It is demonstrated that individual NO adducts can be desorbed using the atomically sharp tip of a scanning tunneling microscope, whereby a writing process is implemented for fully saturated regular metalloporphyrin arrays. The low-energy vibrational characteristics of individual Co-TPP-nitrosyl complexes probed by inelastic electron tunneling spectroscopy (IETS) reveal a prominent signature at an energy of ~/=31 meV. Using density functional theory-based IETS simulations-the first to be performed on such an extensive interfacial nanosystem-we succeed to reproduce the low-frequency spectrum for the NO-ligated complex and explain the absence of IETS activity for bare Co-TPP. Moreover, we can conclusively assign the IETS peak of NO-Co-TPP to a unique vibration mode involving the NO complexation site, namely, the in-plane Co-N-O rocking mode. In addition, we verify that the propensity rules previously designed on small aromatic systems and molecular fragments hold true for a metal-organic entity. This work notably permits one to envisage IETS spectroscopy as a sensitive tool to chemically characterize hybrid interfaces formed by complex metal-organic units and gaseous adducts.
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Affiliation(s)
- Shiri R. Burema
- Laboratoire de Chimie, CNRS UMR 5182, Ecole Normale Supérieure de Lyon, 46 Allée d’Italie, 69364 CEDEX07 Lyon, France
| | - Knud Seufert
- Physik Department E20, Technische Universität München, James-Franck Str. D-85748 Garching, Germany
| | - Willi Auwärter
- Physik Department E20, Technische Universität München, James-Franck Str. D-85748 Garching, Germany
| | - Johannes V. Barth
- Physik Department E20, Technische Universität München, James-Franck Str. D-85748 Garching, Germany
| | - Marie-Laure Bocquet
- Laboratoire de Chimie, CNRS UMR 5182, Ecole Normale Supérieure de Lyon, 46 Allée d’Italie, 69364 CEDEX07 Lyon, France
- Address correspondence to
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35
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Zhang Y, Yam CY, Chen G. Dissipative time-dependent quantum transport theory. J Chem Phys 2013; 138:164121. [DOI: 10.1063/1.4802592] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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36
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Koslowski B, Maurer N, Stocker M, Chulkov SK, Benoit DM, Ziemann P. Analysis of rich inelastic electron tunneling spectra: case study of terthiophene on Au(111). THE REVIEW OF SCIENTIFIC INSTRUMENTS 2013; 84:043907. [PMID: 23635209 DOI: 10.1063/1.4803008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Even moderately small molecules like 2,2':5',2"-terthiophene exhibit quite rich vibrational spectra. Detection and assignment of vibronic transitions of such a single adsorbed molecule in inelastic electron tunneling spectroscopy (IETS) using scanning tunneling microscopy are notoriously hampered by noise and the low efficiency of inelastic channels of typically well below 1%. We demonstrate by a thorough statistical analysis that detection of almost all predicted transitions can be determined experimentally within the energy range 0-120 meV with an estimated detection limit for the efficiency of inelastic channels of ∼0.15%. The maximum accuracy of our transition energies is 2 meV and thus smaller than the thermal broadening at 5 K. On short time scales up to some hours, that accuracy appears to be limited by tunneling current noise. The present analysis confirms earlier results which showed that IETS obeys propensity rules rather than selection rules as observed for optical transitions. Furthermore, the previous indications that anharmonic components in the interaction potentials are important for calculating properties of molecular vibrations were corroborated.
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Affiliation(s)
- B Koslowski
- Institut für Festkörperphysik, Universität Ulm, Ulm, Germany
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37
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Pavliček N, Swart I, Niedenführ J, Meyer G, Repp J. Symmetry dependence of vibration-assisted tunneling. PHYSICAL REVIEW LETTERS 2013; 110:136101. [PMID: 23581345 DOI: 10.1103/physrevlett.110.136101] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Revised: 01/24/2013] [Indexed: 06/02/2023]
Abstract
We present spatially resolved vibronic spectroscopy of individual pentacene molecules in a double-barrier tunneling junction. It is observed that even for this effective single-level system the energy dissipation associated with electron attachment varies spatially by more than a factor of 2. This is in contrast to the usual treatment of electron-vibron coupling in the Franck-Condon picture. Our experiments unambiguously prove that the local symmetry of initial and final wave function determines the dissipation in electron transport.
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Affiliation(s)
- Niko Pavliček
- Institute of Experimental and Applied Physics, University of Regensburg, 93053 Regensburg, Germany.
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Motobayashi K, Katano S, Kim Y, Kawai M. Spectral Fitting of Action Spectra for Motions and Reactions of Single Molecules on Metal Surfaces. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2013. [DOI: 10.1246/bcsj.20120190] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Kenta Motobayashi
- Department of Advanced Materials Science, The University of Tokyo
- RIKEN Advanced Science Institute
- Catalysis Research Center, Hokkaido University
| | - Satoshi Katano
- RIKEN Advanced Science Institute
- Research Institute of Electrical Communication, Tohoku University
| | | | - Maki Kawai
- Department of Advanced Materials Science, The University of Tokyo
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39
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Abstract
Single molecular junctions, in which a single molecule bridges between metal electrodes, have attracted wide attention as novel properties can appear due to their peculiar geometrical and electronic characters. The single molecular junction has also attracted attention due to its potential application in ultrasmall single molecular electronic devices, where single molecules are utilized as active electronic components. Thus, fabrication of single molecular junctions as well as understanding and controlling their properties (e.g. conductance, optical and magnetic properties) have become long-standing goals of scientists and engineers. This review article focuses on the experimental aspects of single molecular junctions, with primary focus on the electron transport mechanism.
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Affiliation(s)
- Manabu Kiguchi
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 W4-10 Ookayama, Tokyo 152-8551, Japan.
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40
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Franke KJ, Pascual JI. Effects of electron-vibration coupling in transport through single molecules. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:394002. [PMID: 22964796 DOI: 10.1088/0953-8984/24/39/394002] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Using scanning tunneling spectroscopy, we study the transport of electrons through C(60) molecules on different metal surfaces. When electrons tunnel through a molecule, they may excite molecular vibrations. A fingerprint of these processes is a characteristic sub-structure in the differential conductance spectra of the molecular junction reflecting the onset of vibrational excitation. Although the intensity of these processes is generally weak, they become more important as the resonant character of the transport mechanism increases. The detection of single vibrational levels crucially depends on the energy level alignment and lifetimes of excited states. In the limit of large current densities, resonant electron-vibration coupling leads to an energy accumulation in the molecule, which eventually leads to its decomposition. With our experiments on C(60) we are able to depict a molecular scale picture of how electrons interact with the vibrational degrees of freedom of single molecules in different transport regimes. This understanding helps in the development of stable molecular devices, which may also carry a switchable functionality.
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Affiliation(s)
- Katharina J Franke
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
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41
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Demir F, Kirczenow G. Inelastic tunneling spectroscopy of gold-thiol and gold-thiolate interfaces in molecular junctions: the role of hydrogen. J Chem Phys 2012; 137:094703. [PMID: 22957582 DOI: 10.1063/1.4748379] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
It is widely believed that when a molecule with thiol (S-H) end groups bridges a pair of gold electrodes, the S atoms bond to the gold and the thiol H atoms detach from the molecule. However, little is known regarding the details of this process, its time scale, and whether molecules with and without thiol hydrogen atoms can coexist in molecular junctions. Here, we explore theoretically how inelastic tunneling spectroscopy (IETS) can shed light on these issues. We present calculations of the geometries, low bias conductances, and IETS of propanedithiol and propanedithiolate molecular junctions with gold electrodes. We show that IETS can distinguish between junctions with molecules having no, one, or two thiol hydrogen atoms. We find that in most cases, the single-molecule junctions in the IETS experiment of Hihath et al. [Nano Lett. 8, 1673 (2008)] had no thiol H atoms, but that a molecule with a single thiol H atom may have bridged their junction occasionally. We also consider the evolution of the IETS spectrum as a gold STM tip approaches the intact S-H group at the end of a molecule bound at its other end to a second electrode. We predict the frequency of a vibrational mode of the thiol H atom to increase by a factor ~2 as the gap between the tip and molecule narrows. Therefore, IETS should be able to track the approach of the tip towards the thiol group of the molecule and detect the detachment of the thiol H atom from the molecule when it occurs.
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Affiliation(s)
- Firuz Demir
- Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada.
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42
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Burema SR, Bocquet ML. Sensitizers in inelastic electron tunneling spectroscopy: a first-principles study of functional aromatics on Cu(111). NANOTECHNOLOGY 2012; 23:315702. [PMID: 22797417 DOI: 10.1088/0957-4484/23/31/315702] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Low sensitivity is a key problem in inelastic electron tunneling spectroscopy (IETS) with the scanning tunneling microscope. Using first-principles simulations, we predict different means to tune the IETS sensitivity of symmetrical functional aromatics on a Cu(111) surface. We show how the IET-spectra of phenyl-NO₂ compounds can be greatly enhanced as compared to pristine phenyl. More precisely, the NO₂ substituent qualifies as a sensitizer of low-frequency wagging modes, but also as a quencher of high-frequency stretching modes. At variance, the CO₂ substituent is found to suppress the whole IET-activity. The head-up (non-anchoring) and head-down (anchoring) configurations of the functional group lead to minor changes in the signals, nevertheless allowing access to discriminate configurational features. It is shown how to disentangle the electronic and steric effects of the substituent in the STM junction.
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Affiliation(s)
- S R Burema
- Laboratoire de Chimie, Ecole Normale Supérieure de Lyon, Université de Lyon, CNRS, France
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43
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Hsu BC, Chiang CW, Chen YC. Effect of electron-vibration interactions on the thermoelectric efficiency of molecular junctions. NANOTECHNOLOGY 2012; 23:275401. [PMID: 22706566 DOI: 10.1088/0957-4484/23/27/275401] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
From first-principles approaches, we investigate the thermoelectric efficiency of a molecular junction where a benzene molecule is connected directly to the platinum electrodes. We calculate the thermoelectric figure of merit ZT in the presence of electron-vibration interactions with and without local heating under two scenarios: linear response and finite bias regimes. In the linear response regime, ZT saturates around the electrode temperature T(e) = 25 K in the elastic case, while in the inelastic case we observe a non-saturated and a much larger ZT beyond T(e) = 25 K attributed to the tail of the Fermi-Dirac distribution. In the finite bias regime, the inelastic effects reveal the signatures of the molecular vibrations in the low-temperature regime. The normal modes exhibiting structures in the inelastic profile are characterized by large components of atomic vibrations along the current density direction on top of each individual atom. In all cases, the inclusion of local heating leads to a higher wire temperature T(w) and thus magnifies further the influence of the electron-vibration interactions due to the increased number of local phonons.
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Affiliation(s)
- Bailey C Hsu
- Department of Electrophysics, National Chiao Tung University, 1001 University Road, Hsinchu 30010, Taiwan
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44
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Burema SR, Lorente N, Bocquet ML. A theoretical rationalization of a total inelastic electron tunneling spectrum: the comparative cases of formate and benzoate on Cu(111). J Chem Phys 2012; 136:244507. [PMID: 22755587 DOI: 10.1063/1.4730168] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Inelastic electron tunneling spectroscopy (IETS) performed with the scanning tunneling microscope (STM) has been deemed as the ultimate tool for identifying chemicals at the atomic scale. However, direct IETS-based chemical analysis remains difficult due to the selection rules that await a definite understanding. We present IETS simulations of single formate and benzoate species adsorbed in the same upright bridge geometry on a (111)-cleaved Cu surface. In agreement with measurements on a related substrate, the simulated IET-spectra of formate/Cu(111) clearly resolve one intense C-H stretching mode whatever the tip position in the vicinity of the molecular fragment. At variance, benzoate/Cu(111) has no detectable IET signal. The dissimilar IETS responses of chemically related molecules--formate and benzoate adsorbates--permit us to unveil another factor that complements the selection rules, namely the degree of the vacuum extension of the tunneling active states perturbed by the vibrations. As a consequence, the lack of a topmost dangling bond orbital is entirely detrimental for STM-based inelastic spectroscopy but not for STM elastic imaging.
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Affiliation(s)
- S R Burema
- Ecole Normale Supérieure de Lyon, Laboratoire de Chimie, CNRS UMR 5182, 46 Allée d'Italie, 69364 Lyon Cedex 07, France
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Reuter MG, Hersam MC, Seideman T, Ratner MA. Signatures of cooperative effects and transport mechanisms in conductance histograms. NANO LETTERS 2012; 12:2243-2248. [PMID: 22494042 DOI: 10.1021/nl204379j] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We present a computational investigation into the line shapes of peaks in conductance histograms, finding that they possess high information content. In particular, the histogram peak associated with conduction through a single molecule elucidates the electron transport mechanism and is generally well-described by beta distributions. A statistical analysis of the peak corresponding to conduction through two molecules reveals the presence of cooperative effects between the molecules and also provides insight into the underlying conduction channels. This work describes tools for extracting additional interpretations from experimental statistical data, helping us better understand electron transport processes.
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Affiliation(s)
- Matthew G Reuter
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA.
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Kumar M, Avriller R, Yeyati AL, van Ruitenbeek JM. Detection of vibration-mode scattering in electronic shot noise. PHYSICAL REVIEW LETTERS 2012; 108:146602. [PMID: 22540815 DOI: 10.1103/physrevlett.108.146602] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Indexed: 05/31/2023]
Abstract
We present shot noise measurements on Au nanowires showing very pronounced vibration-mode features. In accordance to recent theoretical predictions the sign of the inelastic signal, i.e., the signal due to vibration excitations, depends on the transmission probability becoming negative below a certain transmission value. We argue that the negative contribution to noise arises from coherent two-electron processes mediated by electron-phonon scattering and the Pauli exclusion principle. These signals can provide unique information on the local phonon population and lattice temperature of the nanoscale system.
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Affiliation(s)
- Manohar Kumar
- Kamerlingh Onnes Laboratorium, Universiteit Leiden, PO Box 9504, 2300 RA Leiden, The Netherlands
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47
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Dash LK, Ness H, Verstraete MJ, Godby RW. Functionality in single-molecule devices: Model calculations and applications of the inelastic electron tunneling signal in molecular junctions. J Chem Phys 2012; 136:064708. [DOI: 10.1063/1.3684627] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
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48
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Demir F, Kirczenow G. Identification of the atomic scale structures of the gold-thiol interfaces of molecular nanowires by inelastic tunneling spectroscopy. J Chem Phys 2012; 136:014703. [DOI: 10.1063/1.3671455] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
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49
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Morgenstern K. On the interpretation of IETS spectra of a small organic molecule. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:484007. [PMID: 22086063 DOI: 10.1088/0953-8984/23/48/484007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We have investigated vibrational spectra of nitrobenzene molecules adsorbed on Cu(111) by low temperature inelastic electron tunneling spectroscopy. This molecule, which should support 39 internal modes, only gives rise to seven peaks in the spectra. We outline a comparison with ensemble IR data and interpret the small number of vibrational peaks by the superposition of a multitude of almost isoenergetic vibrational modes. The non-detectability of further modes cannot be understood in terms of symmetry considerations. Additional modes in the spectra are attributed to external molecular-metal vibrations.
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Affiliation(s)
- Karina Morgenstern
- Institut für Festkörperphysik, Abteilung ATMOS, Leibniz Universität Hannover, Hannover, Germany
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50
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Bruot C, Hihath J, Tao N. Mechanically controlled molecular orbital alignment in single molecule junctions. NATURE NANOTECHNOLOGY 2011; 7:35-40. [PMID: 22138861 DOI: 10.1038/nnano.2011.212] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Accepted: 10/31/2011] [Indexed: 05/31/2023]
Abstract
Research in molecular electronics often involves the demonstration of devices that are analogous to conventional semiconductor devices, such as transistors and diodes, but it is also possible to perform experiments that have no parallels in conventional electronics. For example, by applying a mechanical force to a molecule bridged between two electrodes, a device known as a molecular junction, it is possible to exploit the interplay between the electrical and mechanical properties of the molecule to control charge transport through the junction. 1,4'-Benzenedithiol is the most widely studied molecule in molecular electronics, and it was shown recently that the molecular orbitals can be gated by an applied electric field. Here, we report how the electromechanical properties of a 1,4'-benzenedithiol molecular junction change as the junction is stretched and compressed. Counterintuitively, the conductance increases by more than an order of magnitude during stretching, and then decreases again as the junction is compressed. Based on simultaneously recorded current-voltage and conductance-voltage characteristics, and inelastic electron tunnelling spectroscopy, we attribute this finding to a strain-induced shift of the highest occupied molecular orbital towards the Fermi level of the electrodes, leading to a resonant enhancement of the conductance. These results, which are in agreement with the predictions of theoretical models, also clarify the origins of the long-standing discrepancy between the calculated and measured conductance values of 1,4'-benzenedithiol, which often differ by orders of magnitude.
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Affiliation(s)
- Christopher Bruot
- Center for Bioelectronics and Biosensors, Biodesign Institute, School of Electrical, Energy and Computer Engineering, Arizona State University, Tempe, Arizona 85287-5801, USA
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