1
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Luo Y, Sheng S, Pisarra M, Martin-Jimenez A, Martin F, Kern K, Garg M. Selective excitation of vibrations in a single molecule. Nat Commun 2024; 15:6983. [PMID: 39143046 PMCID: PMC11324655 DOI: 10.1038/s41467-024-51419-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2024] [Accepted: 08/06/2024] [Indexed: 08/16/2024] Open
Abstract
The capability to excite, probe, and manipulate vibrational modes is essential for understanding and controlling chemical reactions at the molecular level. Recent advancements in tip-enhanced Raman spectroscopies have enabled the probing of vibrational fingerprints in a single molecule with Ångström-scale spatial resolution. However, achieving controllable excitation of specific vibrational modes in individual molecules remains challenging. Here, we demonstrate the selective excitation and probing of vibrational modes in single deprotonated phthalocyanine molecules utilizing resonance Raman spectroscopy in a scanning tunneling microscope. Selective excitation is achieved by finely tuning the excitation wavelength of the laser to be resonant with the vibronic transitions between the molecular ground electronic state and the vibrational levels in the excited electronic state, resulting in the state-selective enhancement of the resonance Raman signal. Our approach contributes to setting the stage for steering chemical transformations in molecules on surfaces by selective excitation of molecular vibrations.
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Affiliation(s)
- Yang Luo
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569, Stuttgart, Germany.
| | - Shaoxiang Sheng
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569, Stuttgart, Germany
| | - Michele Pisarra
- Dipartimento di Fisica, Università della Calabria, Via P. Bucci, Cubo 30C, 87036, Rende, CS, Italy
- INFN-LNF, Gruppo Collegato di Cosenza, Via P. Bucci, Cubo 31C, 87036, Rende, CS, Italy
| | - Alberto Martin-Jimenez
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569, Stuttgart, Germany
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA Nano), Faraday 9, Cantoblanco, 28049, Madrid, Spain
| | - Fernando Martin
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA Nano), Faraday 9, Cantoblanco, 28049, Madrid, Spain.
- Departamento de Química, Módulo 13, Universidad Autónoma de Madrid, 28049, Madrid, Spain.
| | - Klaus Kern
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569, Stuttgart, Germany
- Institut de Physique, Ecole Polytechnique Fédérale de Lausanne, 1015, Lausanne, Switzerland
| | - Manish Garg
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569, Stuttgart, Germany.
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2
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Bi L, Jamnuch S, Chen A, Do A, Balto KP, Wang Z, Zhu Q, Wang Y, Zhang Y, Tao AR, Pascal TA, Figueroa JS, Li S. Molecular-Scale Visualization of Steric Effects of Ligand Binding to Reconstructed Au(111) Surfaces. J Am Chem Soc 2024; 146:11764-11772. [PMID: 38625675 PMCID: PMC11066864 DOI: 10.1021/jacs.4c00002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2024] [Revised: 03/28/2024] [Accepted: 03/29/2024] [Indexed: 04/17/2024]
Abstract
Direct imaging of single molecules at nanostructured interfaces is a grand challenge with potential to enable new, precise material architectures and technologies. Of particular interest are the structural morphology and spectroscopic signatures of the adsorbed molecule, where modern probes are only now being developed with the necessary spatial and energetic resolution to provide detailed information at the molecule-surface interface. Here, we directly characterize the adsorption of individual m-terphenyl isocyanide ligands on a reconstructed Au(111) surface through scanning tunneling microscopy and inelastic electron tunneling spectroscopy. The site-dependent steric pressure of the various surface features alters the vibrational fingerprints of the m-terphenyl isocyanides, which are characterized with single-molecule precision through joint experimental and theoretical approaches. This study provides molecular-level insights into the steric-pressure-enabled surface binding selectivity as well as its effect on the chemical properties of individual surface-binding ligands.
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Affiliation(s)
- Liya Bi
- Department
of Chemistry and Biochemistry, University
of California, San Diego, California 92093-0309, United States
- Program
in Materials Science and Engineering, University
of California, San Diego, California 92093-0418, United States
| | - Sasawat Jamnuch
- Department
of Nano and Chemical Engineering, University
of California, San Diego, California 92093-0448, United States
| | - Amanda Chen
- Department
of Nano and Chemical Engineering, University
of California, San Diego, California 92093-0448, United States
| | - Alexandria Do
- Program
in Materials Science and Engineering, University
of California, San Diego, California 92093-0418, United States
- Department
of Nano and Chemical Engineering, University
of California, San Diego, California 92093-0448, United States
| | - Krista P. Balto
- Department
of Chemistry and Biochemistry, University
of California, San Diego, California 92093-0309, United States
| | - Zhe Wang
- Institute
of Fundamental and Frontier Sciences, University
of Electronic Science and Technology of China, Chengdu 611731, China
| | - Qingyi Zhu
- Department
of Chemistry and Biochemistry, University
of California, San Diego, California 92093-0309, United States
| | - Yufei Wang
- Program
in Materials Science and Engineering, University
of California, San Diego, California 92093-0418, United States
- Department
of Nano and Chemical Engineering, University
of California, San Diego, California 92093-0448, United States
| | - Yanning Zhang
- Institute
of Fundamental and Frontier Sciences, University
of Electronic Science and Technology of China, Chengdu 611731, China
| | - Andrea R. Tao
- Department
of Chemistry and Biochemistry, University
of California, San Diego, California 92093-0309, United States
- Program
in Materials Science and Engineering, University
of California, San Diego, California 92093-0418, United States
- Department
of Nano and Chemical Engineering, University
of California, San Diego, California 92093-0448, United States
| | - Tod A. Pascal
- Program
in Materials Science and Engineering, University
of California, San Diego, California 92093-0418, United States
- Department
of Nano and Chemical Engineering, University
of California, San Diego, California 92093-0448, United States
| | - Joshua S. Figueroa
- Department
of Chemistry and Biochemistry, University
of California, San Diego, California 92093-0309, United States
- Program
in Materials Science and Engineering, University
of California, San Diego, California 92093-0418, United States
| | - Shaowei Li
- Department
of Chemistry and Biochemistry, University
of California, San Diego, California 92093-0309, United States
- Program
in Materials Science and Engineering, University
of California, San Diego, California 92093-0418, United States
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3
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Yao J, Park Y, Shi W, Chen S, Ho W. Origin of photoinduced DC current and two-level population dynamics in a single molecule. SCIENCE ADVANCES 2024; 10:eadk9211. [PMID: 38295170 PMCID: PMC10830102 DOI: 10.1126/sciadv.adk9211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 01/02/2024] [Indexed: 02/02/2024]
Abstract
Studying the photoinduced changes of materials with atomic-scale spatial resolution can provide a fundamental understanding of light-matter interaction. A long-standing impediment has been the detrimental thermal effects on the stability of the tunneling gap from intensity-modulated laser irradiation of the scanning tunneling microscope junction. Photoinduced DC current transduces photons to an electric current and is widely applied in optoelectronics as switches and signal transmission. Our results revealed the origin of the light-induced DC current and related it to the two-level population dynamics and related nonlinearity in the conductance of a single molecule. Here, we compensated for the near-visible laser-induced thermal effects to demonstrate photoinduced DC current spectroscopy and microscopy and to observe the persistent photoconductivity of a two-level pyrrolidine molecule. The methodology can be generally applied to the coupling of light to scan probes to investigate light-matter interactions at the atomic scale.
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Affiliation(s)
- Jiang Yao
- Department of Physics and Astronomy, University of California, Irvine, Irvine, CA 92697-4575, USA
| | - Youngwook Park
- Department of Physics and Astronomy, University of California, Irvine, Irvine, CA 92697-4575, USA
| | - Wenlu Shi
- Department of Physics and Astronomy, University of California, Irvine, Irvine, CA 92697-4575, USA
| | - Siyu Chen
- Department of Physics and Astronomy, University of California, Irvine, Irvine, CA 92697-4575, USA
| | - W. Ho
- Department of Physics and Astronomy, University of California, Irvine, Irvine, CA 92697-4575, USA
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697-2025, USA
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4
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Wu H, Li G, Hou J, Sotthewes K. Probing surface properties of organic molecular layers by scanning tunneling microscopy. Adv Colloid Interface Sci 2023; 318:102956. [PMID: 37393823 DOI: 10.1016/j.cis.2023.102956] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 06/21/2023] [Accepted: 06/23/2023] [Indexed: 07/04/2023]
Abstract
In view of the relevance of organic thin layers in many fields, the fundamentals, growth mechanisms, and dynamics of thin organic layers, in particular thiol-based self-assembled monolayers (SAMs) on Au(111) are systematically elaborated. From both theoretical and practical perspectives, dynamical and structural features of the SAMs are of great intrigue. Scanning tunneling microscopy (STM) is a remarkably powerful technique employed in the characterization of SAMs. Numerous research examples of investigation about the structural and dynamical properties of SAMs using STM, sometimes combined with other techniques, are listed in the review. Advanced options to enhance the time resolution of STM are discussed. Additionally, we elaborate on the extremely diverse dynamics of various SAMs, such as phase transitions and structural changes at the molecular level. In brief, the current review is expected to supply a better understanding and novel insights regarding the dynamical events happening in organic SAMs and how to characterize these processes.
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Affiliation(s)
- Hairong Wu
- State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum-Beijing, Beijing 102249, China; Unconventional Petroleum Research Institute, China University of Petroleum-Beijing, Beijing 102249, China.
| | - Genglin Li
- College of Science, China University of Petroleum-Beijing, Beijing 102249, China
| | - Jirui Hou
- State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum-Beijing, Beijing 102249, China; Unconventional Petroleum Research Institute, China University of Petroleum-Beijing, Beijing 102249, China
| | - Kai Sotthewes
- Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede, the Netherlands.
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5
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Garzón-Ramírez AJ, Franco I. Stark control of electrons across the molecule-semiconductor interface. J Chem Phys 2023; 159:044704. [PMID: 37486053 DOI: 10.1063/5.0154862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2023] [Accepted: 07/06/2023] [Indexed: 07/25/2023] Open
Abstract
Controlling matter at the level of electrons using ultrafast laser sources represents an important challenge for science and technology. Recently, we introduced a general laser control scheme (the Stark control of electrons at interfaces or SCELI) based on the Stark effect that uses the subcycle structure of light to manipulate electron dynamics at semiconductor interfaces [A. Garzón-Ramírez and I. Franco, Phys. Rev. B 98, 121305 (2018)]. Here, we demonstrate that SCELI is also of general applicability in molecule-semiconductor interfaces. We do so by following the quantum dynamics induced by non-resonant few-cycle laser pulses of intermediate intensity (non-perturbative but non-ionizing) across model molecule-semiconductor interfaces of varying level alignments. We show that SCELI induces interfacial charge transfer regardless of the energy level alignment of the interface and even in situations where charge exchange is forbidden via resonant photoexcitation. We further show that the SCELI rate of charge transfer is faster than those offered by resonant photoexcitation routes as it is controlled by the subcycle structure of light. The results underscore the general applicability of SCELI to manipulate electron dynamics at interfaces on ultrafast timescales.
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Affiliation(s)
| | - Ignacio Franco
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA
- Department of Physics, University of Rochester, Rochester, New York 14627, USA
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6
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Liang K, Bi L, Zhu Q, Zhou H, Li S. Ultrafast Dynamics Revealed with Time-Resolved Scanning Tunneling Microscopy: A Review. ACS APPLIED OPTICAL MATERIALS 2023; 1:924-938. [PMID: 37260467 PMCID: PMC10227725 DOI: 10.1021/acsaom.2c00169] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 02/23/2023] [Indexed: 06/02/2023]
Abstract
A scanning tunneling microscope (STM) capable of performing pump-probe spectroscopy integrates unmatched atomic-scale resolution with high temporal resolution. In recent years, the union of electronic, terahertz, or visible/near-infrared pulses with STM has contributed to our understanding of the atomic-scale processes that happen between milliseconds and attoseconds. This time-resolved STM (TR-STM) technique is evolving into an unparalleled approach for exploring the ultrafast nuclear, electronic, or spin dynamics of molecules, low-dimensional structures, and material surfaces. Here, we review the recent advancements in TR-STM; survey its application in measuring the dynamics of three distinct systems, nucleus, electron, and spin; and report the studies on these transient processes in a series of materials. Besides the discussion on state-of-the-art techniques, we also highlight several emerging research topics about the ultrafast processes in nanoscale objects where we anticipate that the TR-STM can help broaden our knowledge.
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Affiliation(s)
- Kangkai Liang
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
- Materials
Science and Engineering Program, University
of California, San Diego, La Jolla, California 92093-0418, United States
| | - Liya Bi
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
- Materials
Science and Engineering Program, University
of California, San Diego, La Jolla, California 92093-0418, United States
| | - Qingyi Zhu
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
| | - Hao Zhou
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
- Materials
Science and Engineering Program, University
of California, San Diego, La Jolla, California 92093-0418, United States
| | - Shaowei Li
- Department
of Chemistry and Biochemistry, University
of California, San Diego, La Jolla, California 92093-0309, United States
- Materials
Science and Engineering Program, University
of California, San Diego, La Jolla, California 92093-0418, United States
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7
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Wang L, Bai D, Xia Y, Ho W. Electrical Manipulation of Quantum Coherence in a Two-Level Molecular System. PHYSICAL REVIEW LETTERS 2023; 130:096201. [PMID: 36930940 DOI: 10.1103/physrevlett.130.096201] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 01/06/2023] [Indexed: 06/18/2023]
Abstract
We report the manipulation of ultrafast quantum coherence of a two-level single hydrogen molecular system by employing static electric field from the sample bias in a femtosecond terahertz scanning tunneling microscope. A H_{2} molecule adsorbed on the polar Cu_{2}N surface develops an electric dipole and exhibits a giant Stark effect. An avoided crossing of the quantum state energy levels is derived from the resonant frequency of the single H_{2} two levels in a double-well potential. The dephasing time of the initial wave packet can also be changed by applying the electric field. The electrical manipulation for different tunneling gaps in three dimensions allows quantification of the surface electrostatic fields at the atomic scale. Our work demonstrated the potential application of molecules as controllable two-level molecular systems.
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Affiliation(s)
- Likun Wang
- Department of Physics and Astronomy, University of California, Irvine, Irvine, California 92697-4575, USA
| | - Dan Bai
- Department of Physics and Astronomy, University of California, Irvine, Irvine, California 92697-4575, USA
| | - Yunpeng Xia
- Department of Physics and Astronomy, University of California, Irvine, Irvine, California 92697-4575, USA
| | - W Ho
- Department of Physics and Astronomy, University of California, Irvine, Irvine, California 92697-4575, USA
- Department of Chemistry, University of California, Irvine, Irvine, California 92697-2025, USA
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8
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Iwaya K, Yokota M, Hanada H, Mogi H, Yoshida S, Takeuchi O, Miyatake Y, Shigekawa H. Externally-triggerable optical pump-probe scanning tunneling microscopy with a time resoloution of tens-picosecond. Sci Rep 2023; 13:818. [PMID: 36697458 PMCID: PMC9877009 DOI: 10.1038/s41598-023-27383-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 01/02/2023] [Indexed: 01/27/2023] Open
Abstract
Photoinduced carrier dynamics of nanostructures play a crucial role in developing novel functionalities in advanced materials. Optical pump-probe scanning tunneling microscopy (OPP-STM) represents distinctive capabilities of real-space imaging of such carrier dynamics with nanoscale spatial resolution. However, combining the advanced technology of ultrafast pulsed lasers with STM for stable time-resolved measurements has remained challenging. The recent OPP-STM system, whose laser-pulse timing is electrically controlled by external triggers, has significantly simplified this combination but limited its application due to nanosecond temporal resolution. Here we report an externally-triggerable OPP-STM system with a temporal resolution in the tens-picosecond range. We also realize the stable laser illumination of the tip-sample junction by placing a position-movable aspheric lens driven by piezo actuators directly on the STM stage and by employing an optical beam stabilization system. We demonstrate the OPP-STM measurements on GaAs(110) surfaces, observing carrier dynamics with a decay time of [Formula: see text] ps and revealing local carrier dynamics at features including a step edge and a nanoscale defect. The stable OPP-STM measurements with the tens-picosecond resolution by the electrical control of laser pulses highlight the potential capabilities of this system for investigating nanoscale carrier dynamics of a wide range of functional materials.
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Affiliation(s)
| | | | | | - Hiroyuki Mogi
- Faculty of Pure and Applied Sciences, University of Tsukuba, Ibaraki, 305-8573, Japan
| | - Shoji Yoshida
- Faculty of Pure and Applied Sciences, University of Tsukuba, Ibaraki, 305-8573, Japan
| | - Osamu Takeuchi
- Faculty of Pure and Applied Sciences, University of Tsukuba, Ibaraki, 305-8573, Japan
| | | | - Hidemi Shigekawa
- Faculty of Pure and Applied Sciences, University of Tsukuba, Ibaraki, 305-8573, Japan.
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9
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Liu S, Hammud A, Hamada I, Wolf M, Müller M, Kumagai T. Nanoscale coherent phonon spectroscopy. SCIENCE ADVANCES 2022; 8:eabq5682. [PMID: 36269832 PMCID: PMC9586471 DOI: 10.1126/sciadv.abq5682] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Accepted: 09/02/2022] [Indexed: 06/02/2023]
Abstract
Coherent phonon spectroscopy can provide microscopic insight into ultrafast lattice dynamics and its coupling to other degrees of freedom under nonequilibrium conditions. Ultrafast optical spectroscopy is a well-established method to study coherent phonons, but the diffraction limit has hampered observing their local dynamics directly. Here, we demonstrate nanoscale coherent phonon spectroscopy using ultrafast laser-induced scanning tunneling microscopy in a plasmonic junction. Coherent phonons are locally excited in ultrathin zinc oxide films by the tightly confined plasmonic field and are probed via the photoinduced tunneling current through an electronic resonance of the zinc oxide film. Concurrently performed tip-enhanced Raman spectroscopy allows us to identify the involved phonon modes. In contrast to the Raman spectra, the phonon dynamics observed in coherent phonon spectroscopy exhibit strong nanoscale spatial variations that are correlated with the distribution of the electronic local density of states resolved by scanning tunneling spectroscopy.
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Affiliation(s)
- Shuyi Liu
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany
| | - Adnan Hammud
- Department of Inorganic Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany
| | - Ikutaro Hamada
- Department of Precision Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871, Japan
| | - Martin Wolf
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany
| | - Melanie Müller
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany
| | - Takashi Kumagai
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany
- Center for Mesoscopic Sciences, Institute for Molecular Science, Okazaki 444-8585, Japan
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10
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Martín Sabanés N, Krecinic F, Kumagai T, Schulz F, Wolf M, Müller M. Femtosecond Thermal and Nonthermal Hot Electron Tunneling Inside a Photoexcited Tunnel Junction. ACS NANO 2022; 16:14479-14489. [PMID: 36027581 PMCID: PMC9527804 DOI: 10.1021/acsnano.2c04846] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 08/19/2022] [Indexed: 06/02/2023]
Abstract
Efficient operation of electronic nanodevices at ultrafast speeds requires understanding and control of the currents generated by femtosecond bursts of light. Ultrafast laser-induced currents in metallic nanojunctions can originate from photoassisted hot electron tunneling or lightwave-induced tunneling. Both processes can drive localized photocurrents inside a scanning tunneling microscope (STM) on femto- to attosecond time scales, enabling ultrafast STM with atomic spatial resolution. Femtosecond laser excitation of a metallic nanojunction, however, also leads to the formation of a transient thermalized electron distribution, but the tunneling of thermalized hot electrons on time scales faster than electron-lattice equilibration is not well understood. Here, we investigate ultrafast electronic heating and transient thermionic tunneling inside a metallic photoexcited tunnel junction and its role in the generation of ultrafast photocurrents in STM. Phase-resolved sampling of broadband terahertz (THz) pulses via the THz-field-induced modulation of ultrafast photocurrents allows us to probe the electronic temperature evolution inside the STM tip and to observe the competition between instantaneous and delayed tunneling due to nonthermal and thermal hot electron distributions in real time. Our results reveal the pronounced nonthermal character of photoinduced hot electron tunneling and provide a detailed microscopic understanding of hot electron dynamics inside a laser-excited tunnel junction.
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Affiliation(s)
- Natalia Martín Sabanés
- Department
of Physical Chemistry, Fritz Haber Institute
of the Max Planck Society, Faradayweg 4-6, 14195Berlin, Germany
- IMDEA
Nanoscience, Faraday 9, 28049Madrid, Spain
| | - Faruk Krecinic
- 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, 444-8585Okazaki, Japan
| | - Fabian Schulz
- 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
| | - Melanie Müller
- Department
of Physical Chemistry, Fritz Haber Institute
of the Max Planck Society, Faradayweg 4-6, 14195Berlin, Germany
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11
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Luo Y, Martin-Jimenez A, Gutzler R, Garg M, Kern K. Ultrashort Pulse Excited Tip-Enhanced Raman Spectroscopy in Molecules. NANO LETTERS 2022; 22:5100-5106. [PMID: 35704454 PMCID: PMC9284611 DOI: 10.1021/acs.nanolett.2c00485] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Vibrational fingerprints of molecules and low-dimension materials can be traced with subnanometer resolution by performing Tip-enhanced Raman spectroscopy (TERS) in a scanning tunneling microscope (STM). Strong atomic-scale localization of light in the plasmonic nanocavity of the STM enables high spatial resolution in STM-TERS; however, the temporal resolution is so far limited. Here, we demonstrate stable TERS measurements from subphthalocyanine (SubPc) molecules excited by ∼500 fs long laser pulses in a low-temperature (LT) ultrahigh-vacuum (UHV) STM. The intensity of the TERS signal excited with ultrashort pulses scales linearly with the increasing flux of the laser pulses and exponentially with the decreasing gap-size of the plasmonic nanocavity. Furthermore, we compare the characteristic features of TERS excited with ultrashort pulses and with a continuous-wave (CW) laser. Our work lays the foundation for future experiments of time-resolved femtosecond TERS for the investigation of molecular dynamics with utmost spatial, temporal, and energy resolutions simultaneously.
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Affiliation(s)
- Yang Luo
- Max
Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
| | - Alberto Martin-Jimenez
- Max
Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
| | - Rico Gutzler
- Max
Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
| | - Manish Garg
- Max
Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
| | - Klaus Kern
- Max
Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
- Institut
de Physique, Ecole Polytechnique Fédérale
de Lausanne, 1015 Lausanne, Switzerland
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12
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Affiliation(s)
- Takashi Kumagai
- Institute for Molecular Science, National Institutes of Natural Sciences, Myodaiji, Okazaki, Japan.
- The Graduate University for Advanced Studies, Sokendai, Okazaki, Japan.
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13
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Wang L, Xia Y, Ho W. Atomic-scale quantum sensing based on the ultrafast coherence of an H 2 molecule in an STM cavity. Science 2022; 376:401-405. [PMID: 35446636 DOI: 10.1126/science.abn9220] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
A scanning tunneling microscope (STM) combined with a pump-probe femtosecond terahertz (THz) laser can enable coherence measurements of single molecules. We report THz pump-probe measurements that demonstrate quantum sensing based on a hydrogen (H2) molecule in the cavity created with an STM tip near a surface. Atomic-scale spatial and femtosecond temporal resolutions were obtained from this quantum coherence. The H2 acts as a two-level system, with its coherent superposition exhibiting extreme sensitivity to the applied electric field and the underlying atomic composition of the copper nitride (Cu2N) monolayer islands grown on a Cu(100) surface. We acquired time-resolved images of THz rectification of H2 over Cu2N islands for variable pump-probe delay times to visualize the heterogeneity of the chemical environment at sub-angstrom scale.
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Affiliation(s)
- Likun Wang
- Department of Physics and Astronomy, University of California, Irvine, CA 92697, USA
| | - Yunpeng Xia
- Department of Physics and Astronomy, University of California, Irvine, CA 92697, USA
| | - W Ho
- Department of Physics and Astronomy, University of California, Irvine, CA 92697, USA.,Department of Chemistry, University of California, Irvine, CA 92697, USA
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14
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Cheng B, Wu D, Bian K, Tian Y, Guo C, Liu K, Jiang Y. A qPlus-based scanning probe microscope compatible with optical measurements. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:043701. [PMID: 35489886 DOI: 10.1063/5.0082369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Accepted: 03/10/2022] [Indexed: 06/14/2023]
Abstract
We design and develop a scanning probe microscope (SPM) system based on the qPlus sensor for atomic-scale optical experiments. The microscope operates under ultrahigh vacuum and low temperature (6.2 K). In order to obtain high efficiency of light excitation and collection, two front lenses with high numerical apertures (N.A. = 0.38) driven by compact nano-positioners are directly integrated on the scanner head without degrading its mechanical and thermal stability. The electric noise floor of the background current is 5 fA/Hz1/2, and the maximum vibrational noise of the tip height is below 200 fm/Hz1/2. The drift of the tip-sample spacing is smaller than 0.1 pm/min. Such a rigid scanner head yields small background noise (oscillation amplitude of ∼2 pm without excitation) and high quality factor (Q factor up to 140 000) for the qPlus sensor. Atomic-resolution imaging and inelastic electron tunneling spectroscopy are obtained under the scanning tunneling microscope mode on the Au(111) surface. The hydrogen-bonding structure of two-dimensional (2D) ice on the Au(111) surface is clearly resolved under the atomic force microscope (AFM) mode with a CO-terminated tip. Finally, the electroluminescence spectrum from a plasmonic AFM tip is demonstrated, which paves the way for future photon-assisted SPM experiments.
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Affiliation(s)
- Bowei Cheng
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Da Wu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Ke Bian
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Ye Tian
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Chaoyu Guo
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Kaihui Liu
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
| | - Ying Jiang
- International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
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15
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Garg M, Martin-Jimenez A, Luo Y, Kern K. Ultrafast Photon-Induced Tunneling Microscopy. ACS NANO 2021; 15:18071-18084. [PMID: 34723474 PMCID: PMC8613903 DOI: 10.1021/acsnano.1c06716] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Accepted: 10/26/2021] [Indexed: 05/25/2023]
Abstract
Unification of the techniques of ultrafast science and scanning tunneling microscopy (STM) has the potential of tracking electronic motion in molecules simultaneously in real space and real time. Laser pulses can couple to an STM junction either in the weak-field or in the strong-field interaction regime. The strong-field regime entails significant modification (dressing) of the tunneling barrier of the STM junction, whereas the weak-field or the photon-driven regime entails perturbative interaction. Here, we describe how photons carried in an ultrashort pulse interact with an STM junction, defining the basic fundamental framework of ultrafast photon-induced tunneling microscopy. Selective dipole coupling of electronic states by photons is shown to be controllable by adjusting the DC bias at the STM junction. An ultrafast tunneling microscopy involving photons is established. Consolidation of the technique calls for innovative approaches to detect photon-induced tunneling currents at the STM junction. We introduce and characterize here three techniques involving dispersion, polarization, and frequency modulation of the laser pulses to lock-in detect the laser-induced tunneling current. We show that photon-induced tunneling currents can simultaneously achieve angstrom scale spatial resolution and sub-femtosecond temporal resolution. Ultrafast photon-induced tunneling microscopy will be able to directly probe electron dynamics in complex molecular systems, without the need of reconstruction techniques.
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Affiliation(s)
- Manish Garg
- Max
Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
| | - Alberto Martin-Jimenez
- Max
Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
| | - Yang Luo
- Max
Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
| | - Klaus Kern
- Max
Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
- Institut
de Physique, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
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16
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Wang R, Bi F, Lu W, Zheng X, Yam C. Tracking Electron Dynamics of Single Molecules in Scanning Tunneling Microscopy Junctions with Laser Pulses. J Phys Chem Lett 2021; 12:6398-6404. [PMID: 34232671 DOI: 10.1021/acs.jpclett.1c01293] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
On the basis of real-time simulations, we devise a method to extend the capability of scanning tunneling microscopy (STM) to track the electronic dynamics of molecules on a material's surface with the ultrafast temporal resolution of laser pulses. The intrinsic mechanism of visualization of electronic dynamics by measuring tunneling charge is attributed to the interference between the electronic oscillations stimulated by pump and probe pulses. The charge-transfer rate from molecule to the surrounding environment can be estimated with the decay time of electronic dynamics, which can also be detected by measuring the tunneling charge across the STM junction. Moreover, it is found that the tunneling charge can be varied precisely by changing the carrier-envelope phase (CEP) of the pulses, and this phase-dependence of tunnelling diminishes as the duration of incident laser pulses increases. The proposed scheme provides an alternative means for visualization of electron dynamics of single molecules by measuring tunnelling charges.
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Affiliation(s)
- Rulin Wang
- College of Physics, Qingdao University, No. 308 Ningxia Road, Qingdao 266071, China
| | - Fuzhen Bi
- Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101, China
| | - Wencai Lu
- College of Physics, Qingdao University, No. 308 Ningxia Road, Qingdao 266071, China
| | - Xiao Zheng
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - ChiYung Yam
- Shenzhen JL Computational Science and Applied Research Institute, Shenzhen 518109, China
- Beijing Computational Science Research Center, Haidian District, Beijing 100193, China
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17
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Bian K, Gerber C, Heinrich AJ, Müller DJ, Scheuring S, Jiang Y. Scanning probe microscopy. ACTA ACUST UNITED AC 2021. [DOI: 10.1038/s43586-021-00033-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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18
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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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19
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Sub-cycle atomic-scale forces coherently control a single-molecule switch. Nature 2020; 585:58-62. [PMID: 32879499 DOI: 10.1038/s41586-020-2620-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 06/30/2020] [Indexed: 12/31/2022]
Abstract
Scanning probe techniques can leverage atomically precise forces to sculpt matter at surfaces, atom by atom. These forces have been applied quasi-statically to create surface structures1-7 and influence chemical processes8,9, but exploiting local dynamics10-14 to realize coherent control on the atomic scale remains an intriguing prospect. Chemical reactions15-17, conformational changes18,19 and desorption20 have been followed on ultrafast timescales, but directly exerting femtosecond forces on individual atoms to selectively induce molecular motion has yet to be realized. Here we show that the near field of a terahertz wave confined to an atomically sharp tip provides femtosecond atomic-scale forces that selectively induce coherent hindered rotation in the molecular frame of a bistable magnesium phthalocyanine molecule. Combining lightwave-driven scanning tunnelling microscopy21-24 with ultrafast action spectroscopy10,13, we find that the induced rotation modulates the probability of the molecule switching between its two stable adsorption geometries by up to 39 per cent. Mapping the response of the molecule in space and time confirms that the force acts on the atomic scale and within less than an optical cycle (that is, faster than an oscillation period of the carrier wave of light). We anticipate that our strategy might ultimately enable the coherent manipulation of individual atoms within single molecules or solids so that chemical reactions and ultrafast phase transitions can be manipulated on their intrinsic spatio-temporal scales.
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20
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Schultz JF, Li S, Jiang S, Jiang N. Optical scanning tunneling microscopy based chemical imaging and spectroscopy. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:463001. [PMID: 32702674 DOI: 10.1088/1361-648x/aba8c7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Accepted: 07/23/2020] [Indexed: 06/11/2023]
Abstract
Through coupling optical processes with the scanning tunneling microscope (STM), single-molecule chemistry and physics have been investigated at the ultimate spatial and temporal limit. Electrons and photons can be used to drive interactions and reactions in chemical systems and simultaneously probe their characteristics and consequences. In this review we introduce and review methods to couple optical imaging and spectroscopy with scanning tunneling microscopy. The integration of the STM and optical spectroscopy provides new insights into individual molecular adsorbates, surface-supported molecular assemblies, and two-dimensional materials with subnanoscale resolution, enabling the fundamental study of chemistry at the spatial and temporal limit. The inelastic scattering of photons by molecules and materials, that results in unique and sensitive vibrational fingerprints, will be considered with tip-enhanced Raman spectroscopy. STM-induced luminescence examines the intrinsic luminescence of organic adsorbates and their energy transfer and charge transfer processes with their surroundings. We also provide a survey of recent efforts to probe the dynamics of optical excitation at the molecular level with scanning tunneling microscopy in the context of light-induced photophysical and photochemical transformations.
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Affiliation(s)
- Jeremy F Schultz
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, United States of America
| | - Shaowei Li
- Department of Chemistry and Biochemistry, University of California, San Diego, CA 92093, United States of America
- Kavli Energy NanoScience Institute, University of California, Berkeley, CA 94720, United States of America
| | - Song Jiang
- Université de Strasbourg, CNRS, IPCMS, UMR 7504, F-67000 Strasbourg, France
| | - Nan Jiang
- Department of Chemistry, University of Illinois at Chicago, Chicago, IL 60607, United States of America
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21
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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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22
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Li S, Zhong C, Henning A, Sangwan VK, Zhou Q, Liu X, Rahn MS, Wells SA, Park HY, Luxa J, Sofer Z, Facchetti A, Darancet P, Marks TJ, Lauhon LJ, Weiss EA, Hersam MC. Molecular-Scale Characterization of Photoinduced Charge Separation in Mixed-Dimensional InSe-Organic van der Waals Heterostructures. ACS NANO 2020; 14:3509-3518. [PMID: 32078300 DOI: 10.1021/acsnano.9b09661] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Layered indium selenide (InSe) is an emerging two-dimensional semiconductor that has shown significant promise for high-performance transistors and photodetectors. The range of optoelectronic applications for InSe can potentially be broadened by forming mixed-dimensional van der Waals heterostructures with zero-dimensional molecular systems that are widely employed in organic electronics and photovoltaics. Here, we report the spatially resolved investigation of photoinduced charge separation between InSe and two molecules (C70 and C8-BTBT) using scanning tunneling microscopy combined with laser illumination. We experimentally and computationally show that InSe forms type-II and type-I heterojunctions with C70 and C8-BTBT, respectively, due to an interplay of charge transfer and dielectric screening at the interface. Laser-excited scanning tunneling spectroscopy reveals a ∼0.25 eV decrease in the energy of the lowest unoccupied molecular orbital of C70 with optical illumination. Furthermore, photoluminescence spectroscopy and Kelvin probe force microscopy indicate that electron transfer from InSe to C70 in the type-II heterojunction induces a photovoltage that quantitatively matches the observed downshift in the tunneling spectra. In contrast, no significant changes are observed upon optical illumination in the type-I heterojunction formed between InSe and C8-BTBT. Density functional theory calculations further show that, despite the weak coupling between the molecular species and InSe, the band alignment of these mixed-dimensional heterostructures strongly differs from the one suggested by the ionization potential and electronic affinities of the isolated components. Self-energy-corrected density functional theory indicates that these effects are the result of the combination of charge redistribution at the interface and heterogeneous dielectric screening of the electron-electron interactions in the heterostructure. In addition to providing specific insight for mixed-dimensional InSe-organic van der Waals heterostructures, this work establishes a general experimental methodology for studying localized charge transfer at the molecular scale that is applicable to other photoactive nanoscale systems.
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Affiliation(s)
- Shaowei Li
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208-3108, United States
| | - Chengmei Zhong
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208-3108, United States
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Alex Henning
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208-3108, United States
| | - Vinod K Sangwan
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208-3108, United States
| | - Qunfei Zhou
- Center for Nanoscale Materials, Argonne National Laboratory, Lemont, Illinois 60439, United States
- Northwestern Argonne Institute for Science and Engineering, Evanston, Illinois 60208, United States
| | - Xiaolong Liu
- Applied Physics Graduate Program, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Matthew S Rahn
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208-3108, United States
| | - Spencer A Wells
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208-3108, United States
| | - Hong Youl Park
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208-3108, United States
| | - Jan Luxa
- Department of Inorganic Chemistry, University of Chemistry and Technology Prague, Technicka 5, 166 28 Prague 6, Czech Republic
| | - Zdeněk Sofer
- Department of Inorganic Chemistry, University of Chemistry and Technology Prague, Technicka 5, 166 28 Prague 6, Czech Republic
| | - Antonio Facchetti
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Pierre Darancet
- Center for Nanoscale Materials, Argonne National Laboratory, Lemont, Illinois 60439, United States
- Northwestern Argonne Institute for Science and Engineering, Evanston, Illinois 60208, United States
| | - Tobin J Marks
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Lincoln J Lauhon
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208-3108, United States
| | - Emily A Weiss
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Mark C Hersam
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208-3108, United States
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, United States
- Applied Physics Graduate Program, Northwestern University, Evanston, Illinois 60208-3113, United States
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23
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Yang K, Paul W, Phark SH, Willke P, Bae Y, Choi T, Esat T, Ardavan A, Heinrich AJ, Lutz CP. Coherent spin manipulation of individual atoms on a surface. Science 2019; 366:509-512. [DOI: 10.1126/science.aay6779] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 10/01/2019] [Indexed: 11/03/2022]
Affiliation(s)
- Kai Yang
- IBM Almaden Research Center, San Jose, CA 95120, USA
| | - William Paul
- IBM Almaden Research Center, San Jose, CA 95120, USA
| | - Soo-Hyon Phark
- IBM Almaden Research Center, San Jose, CA 95120, USA
- Center for Quantum Nanoscience, Institute for Basic Science (IBS), Seoul 03760, Republic of Korea
- Department of Physics, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Philip Willke
- IBM Almaden Research Center, San Jose, CA 95120, USA
- Center for Quantum Nanoscience, Institute for Basic Science (IBS), Seoul 03760, Republic of Korea
- Ewha Womans University, Seoul 03760, Republic of Korea
| | - Yujeong Bae
- IBM Almaden Research Center, San Jose, CA 95120, USA
- Center for Quantum Nanoscience, Institute for Basic Science (IBS), Seoul 03760, Republic of Korea
- Ewha Womans University, Seoul 03760, Republic of Korea
| | - Taeyoung Choi
- Center for Quantum Nanoscience, Institute for Basic Science (IBS), Seoul 03760, Republic of Korea
- Department of Physics, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Taner Esat
- IBM Almaden Research Center, San Jose, CA 95120, USA
- Center for Quantum Nanoscience, Institute for Basic Science (IBS), Seoul 03760, Republic of Korea
- Ewha Womans University, Seoul 03760, Republic of Korea
| | - Arzhang Ardavan
- CAESR, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Andreas J. Heinrich
- Center for Quantum Nanoscience, Institute for Basic Science (IBS), Seoul 03760, Republic of Korea
- Department of Physics, Ewha Womans University, Seoul 03760, Republic of Korea
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24
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Kwok Y, Chen G, Mukamel S. STM Imaging of Electron Migration in Real Space and Time: A Simulation Study. NANO LETTERS 2019; 19:7006-7012. [PMID: 31509425 DOI: 10.1021/acs.nanolett.9b02389] [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
Using a simulation protocol that mimics ultrafast scanning tunneling microscopy (STM) experiments, we demonstrate how pump-probe ultrafast STM may be used to image electron migration in molecules. Two pulses are applied to a model system, and the time-integrated current through the tip is calculated versus the delay time and tip position to generate STM images. With suitable pump and probe parameters, the images can track charge migration with atomistic spatial and femtosecond temporal resolutions.
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Affiliation(s)
- YanHo Kwok
- Department of Chemistry , The University of Hong Kong , Pofkulam Road , Hong Kong
- QuantumFabless Limited , Sha Tin , Hong Kong
| | - GuanHua Chen
- Department of Chemistry , The University of Hong Kong , Pofkulam Road , Hong Kong
| | - Shaul Mukamel
- Department of Chemistry and Physics and Astronomy , University of California , Irvine , California 92617 , United States
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25
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Miwa K, Imada H, Imai-Imada M, Kimura K, Galperin M, Kim Y. Many-Body State Description of Single-Molecule Electroluminescence Driven by a Scanning Tunneling Microscope. NANO LETTERS 2019; 19:2803-2811. [PMID: 30694065 DOI: 10.1021/acs.nanolett.8b04484] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Electron transport and optical properties of a single molecule in contact with conductive materials have attracted considerable attention because of their scientific importance and potential applications. With the recent progress in experimental techniques, especially by virtue of scanning tunneling microscope (STM)-induced light emission, where the tunneling current of the STM is used as an atomic-scale source for induction of light emission from a single molecule, it has become possible to investigate single-molecule properties at subnanometer spatial resolution. Despite extensive experimental studies, the microscopic mechanism of electronic excitation of a single molecule in STM-induced light emission has yet to be clarified. Here we present a formulation of single-molecule electroluminescence driven by electron transfer between a molecule and metal electrodes based on a many-body state representation of the molecule. The effects of intramolecular Coulomb interaction on conductance and luminescence spectra are investigated using the nonequilibrium Hubbard Green's function technique combined with first-principles calculations. We compare simulation results with experimental data and find that the intramolecular Coulomb interaction is crucial for reproducing recent experiments for a single phthalocyanine molecule. The developed theory provides a unified description of the electron transport and optical properties of a single molecule in contact with metal electrodes driven out of equilibrium, and thereby, it contributes to a microscopic understanding of optoelectronic conversion in single molecules on solid surfaces and in nanometer-scale junctions.
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Affiliation(s)
- Kuniyuki Miwa
- Surface and Interface Science Laboratory , RIKEN , Wako , Saitama 351-0198 , Japan
- Department of Chemistry and Biochemistry , University of California, San Diego , La Jolla , California 92093 , United States
| | - Hiroshi Imada
- Surface and Interface Science Laboratory , RIKEN , Wako , Saitama 351-0198 , Japan
| | - Miyabi Imai-Imada
- Surface and Interface Science Laboratory , RIKEN , Wako , Saitama 351-0198 , Japan
- Department of Advanced Materials Science, Graduate School of Frontier Science , The University of Tokyo , Kashiwa , Chiba 277-8651 , Japan
| | - Kensuke Kimura
- Surface and Interface Science Laboratory , RIKEN , Wako , Saitama 351-0198 , Japan
- Department of Advanced Materials Science, Graduate School of Frontier Science , The University of Tokyo , Kashiwa , Chiba 277-8651 , Japan
| | - Michael Galperin
- Department of Chemistry and Biochemistry , University of California, San Diego , La Jolla , California 92093 , United States
| | - Yousoo Kim
- Surface and Interface Science Laboratory , RIKEN , Wako , Saitama 351-0198 , Japan
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26
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Li S, Czap G, Wang H, Wang L, Chen S, Yu A, Wu R, Ho W. Bond-Selected Photodissociation of Single Molecules Adsorbed on Metal Surfaces. PHYSICAL REVIEW LETTERS 2019; 122:077401. [PMID: 30848644 DOI: 10.1103/physrevlett.122.077401] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2018] [Revised: 12/02/2018] [Indexed: 06/09/2023]
Abstract
We report the photoassisted activation of selected C─H bonds in individual molecules adsorbed on metal surfaces within the junction of a scanning tunneling microscope. Photons can couple to the C─H bond activation of specific hydrocarbons through a resonant photoassisted tunneling process. The molecule to be activated can be selected by positioning the tip with subangstrom resolution. Furthermore, structural tomography of the molecule and its dissociation products are imaged at different heights by the inelastic tunneling probe. The demonstration of single bond dissociation induced by resonant photoassisted tunneling electrons implies the attainment of atomic scale spatial resolution for bond-selected photochemistry.
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Affiliation(s)
- Shaowei Li
- 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
| | - Hui Wang
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, USA
| | - Likun Wang
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, USA
| | - Siyu Chen
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, USA
| | - Arthur Yu
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, USA
| | - 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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Beane G, Devkota T, Brown BS, Hartland GV. Ultrafast measurements of the dynamics of single nanostructures: a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2019; 82:016401. [PMID: 30485256 DOI: 10.1088/1361-6633/aaea4b] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The ability to study single particles has revolutionized nanoscience. The advantage of single particle spectroscopy measurements compared to conventional ensemble studies is that they remove averaging effects from the different sizes and shapes that are present in the samples. In time-resolved experiments this is important for unraveling homogeneous and inhomogeneous broadening effects in lifetime measurements. In this report, recent progress in the development of ultrafast time-resolved spectroscopic techniques for interrogating single nanostructures will be discussed. The techniques include far-field experiments that utilize high numerical aperture (NA) microscope objectives, near-field scanning optical microscopy (NSOM) measurements, ultrafast electron microscopy (UEM), and time-resolved x-ray diffraction experiments. Examples will be given of the application of these techniques to studying energy relaxation processes in nanoparticles, and the motion of plasmons, excitons and/or charge carriers in different types of nanostructures.
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Affiliation(s)
- Gary Beane
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, United States of America
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Liu S, Wolf M, Kumagai T. Plasmon-Assisted Resonant Electron Tunneling in a Scanning Tunneling Microscope Junction. PHYSICAL REVIEW LETTERS 2018; 121:226802. [PMID: 30547648 DOI: 10.1103/physrevlett.121.226802] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Indexed: 05/25/2023]
Abstract
We report plasmon-assisted resonant electron tunneling from a Ag or Au tip to field emission resonances (FERs) of a Ag(111) surface induced by cw laser excitation of a scanning tunneling microscope (STM) junction at visible wavelengths. As a hallmark of the plasmon-assisted resonant tunneling, we observe a downshift of the first peak in the FER spectra by a fixed amount equal to the incident photon energy. STM-induced luminescence measurement for the Ag and Au tip reveals the clear correlation between the laser-induced change in the FER spectra and the plasmonic properties of the junction. Our results clarify a novel resonant electron transfer mechanism in a plasmonic nanocavity.
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Affiliation(s)
- Shuyi Liu
- Department of Physical Chemistry, Fritz-Haber Institute of the Max-Planck Society, Faradayweg 4-6, 14195 Berlin, Germany
| | - Martin Wolf
- Department of Physical Chemistry, Fritz-Haber Institute of the Max-Planck Society, Faradayweg 4-6, 14195 Berlin, Germany
| | - Takashi Kumagai
- Department of Physical Chemistry, Fritz-Haber Institute of the Max-Planck Society, Faradayweg 4-6, 14195 Berlin, Germany
- JST-PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
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29
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Wu ZB, Gao ZY, Chen XY, Xing YQ, Yang H, Li G, Ma R, Wang A, Yan J, Shen C, Du S, Huan Q, Gao HJ. A low-temperature scanning probe microscopy system with molecular beam epitaxy and optical access. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:113705. [PMID: 30501315 DOI: 10.1063/1.5046466] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 10/18/2018] [Indexed: 05/24/2023]
Abstract
A low-temperature ultra-high vacuum scanning probe microscopy (SPM) system with molecular beam epitaxy (MBE) capability and optical access was conceived, built, and tested in our lab. The design of the whole system is discussed here, with special emphasis on some critical parts. The SPM scanner head takes a modified Pan-type design with improved rigidity and compatible configuration to optical access and can accommodate both scanning tunneling microscope (STM) tips and tuning-fork based qPlus sensors. In the system, the scanner head is enclosed by a double-layer cold room under a bath type cryostat. Two piezo-actuated focus-lens stages are mounted on both sides of the cold room to couple light in and out. The optical design ensures the system's forward compatibility to the development of photo-assisted STM techniques. To test the system's performance, we conducted STM and spectroscopy studies. The herringbone reconstruction and atomic structure of an Au(111) surface were clearly resolved. The dI/dV spectra of an Au(111) surface were obtained at 5 K. In addition, a periodic 2D tellurium (Te) structure was grown on the Au(111) surface using MBE and the atomic structure is clearly resolved by using STM.
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Affiliation(s)
- Ze-Bin Wu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Zhao-Yan Gao
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Xi-Ya Chen
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yu-Qing Xing
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Huan Yang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Geng Li
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Ruisong Ma
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Aiwei Wang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Jiahao Yan
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Chengmin Shen
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Shixuan Du
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Qing Huan
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Hong-Jun Gao
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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30
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Rosławska A, Merino P, Große C, Leon CC, Gunnarsson O, Etzkorn M, Kuhnke K, Kern K. Single Charge and Exciton Dynamics Probed by Molecular-Scale-Induced Electroluminescence. NANO LETTERS 2018; 18:4001-4007. [PMID: 29799760 DOI: 10.1021/acs.nanolett.8b01489] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Excitons and their constituent charge carriers play the central role in electroluminescence mechanisms determining the ultimate performance of organic optoelectronic devices. The involved processes and their dynamics are often studied with time-resolved techniques limited by spatial averaging that obscures the properties of individual electron-hole pairs. Here, we overcome this limit and characterize single charge and exciton dynamics at the nanoscale by using time-resolved scanning tunneling microscopy-induced luminescence (TR-STML) stimulated with nanosecond voltage pulses. We use isolated defects in C60 thin films as a model system into which we inject single charges and investigate the formation dynamics of a single exciton. Tunable hole and electron injection rates are obtained from a kinetic model that reproduces the measured electroluminescent transients. These findings demonstrate that TR-STML can track dynamics at the quantum limit of single charge injection and can be extended to other systems and materials important for nanophotonic devices.
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Affiliation(s)
- Anna Rosławska
- Max Planck Institute for Solid State Research , Heisenbergstraße 1 , 70569 Stuttgart , Germany
| | - Pablo Merino
- Max Planck Institute for Solid State Research , Heisenbergstraße 1 , 70569 Stuttgart , Germany
| | - Christoph Große
- Max Planck Institute for Solid State Research , Heisenbergstraße 1 , 70569 Stuttgart , Germany
| | - Christopher C Leon
- Max Planck Institute for Solid State Research , Heisenbergstraße 1 , 70569 Stuttgart , Germany
| | - Olle Gunnarsson
- Max Planck Institute for Solid State Research , Heisenbergstraße 1 , 70569 Stuttgart , Germany
| | - Markus Etzkorn
- Max Planck Institute for Solid State Research , Heisenbergstraße 1 , 70569 Stuttgart , Germany
| | - Klaus Kuhnke
- Max Planck Institute for Solid State Research , Heisenbergstraße 1 , 70569 Stuttgart , Germany
| | - Klaus Kern
- Max Planck Institute for Solid State Research , Heisenbergstraße 1 , 70569 Stuttgart , Germany
- Institut de Physique , École Polytechnique Fédérale de Lausanne , 1015 Lausanne , Switzerland
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31
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Lang D, Döring J, Nörenberg T, Butykai Á, Kézsmárki I, Schneider H, Winnerl S, Helm M, Kehr SC, Eng LM. Infrared nanoscopy down to liquid helium temperatures. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:033702. [PMID: 29604801 DOI: 10.1063/1.5016281] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
We introduce a scattering-type scanning near-field infrared microscope (s-SNIM) for the local scale near-field sample analysis and spectroscopy from room temperature down to liquid helium (LHe) temperature. The extension of s-SNIM down to T = 5 K is in particular crucial for low-temperature phase transitions, e.g., for the examination of superconductors, as well as low energy excitations. The low temperature (LT) s-SNIM performance is tested with CO2-IR excitation at T = 7 K using a bare Au reference and a structured Si/SiO2-sample. Furthermore, we quantify the impact of local laser heating under the s-SNIM tip apex by monitoring the light-induced ferroelectric-to-paraelectric phase transition of the skyrmion-hosting multiferroic material GaV4S8 at Tc = 42 K. We apply LT s-SNIM to study the spectral response of GaV4S8 and its lateral domain structure in the ferroelectric phase by the mid-IR to THz free-electron laser-light source FELBE at the Helmholtz-Zentrum Dresden-Rossendorf, Germany. Notably, our s-SNIM is based on a non-contact atomic force microscope (AFM) and thus can be complemented in situ by various other AFM techniques, such as topography profiling, piezo-response force microscopy (PFM), and/or Kelvin-probe force microscopy (KPFM). The combination of these methods supports the comprehensive study of the mutual interplay in the topographic, electronic, and optical properties of surfaces from room temperature down to 5 K.
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Affiliation(s)
- Denny Lang
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, 01328 Dresden, Germany
| | - Jonathan Döring
- Institute of Applied Physics, Technische Universität Dresden, 01062 Dresden, Germany
| | - Tobias Nörenberg
- Institute of Applied Physics, Technische Universität Dresden, 01062 Dresden, Germany
| | - Ádám Butykai
- Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Magneto-Optical Spectroscopy Research Group, 1111 Budapest, Hungary
| | - István Kézsmárki
- Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Magneto-Optical Spectroscopy Research Group, 1111 Budapest, Hungary
| | - Harald Schneider
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, 01328 Dresden, Germany
| | - Stephan Winnerl
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, 01328 Dresden, Germany
| | - Manfred Helm
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, 01328 Dresden, Germany
| | - Susanne C Kehr
- Institute of Applied Physics, Technische Universität Dresden, 01062 Dresden, Germany
| | - Lukas M Eng
- Institute of Applied Physics, Technische Universität Dresden, 01062 Dresden, Germany
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32
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Böckmann H, Gawinkowski S, Waluk J, Raschke MB, Wolf M, Kumagai T. Near-Field Enhanced Photochemistry of Single Molecules in a Scanning Tunneling Microscope Junction. NANO LETTERS 2018; 18:152-157. [PMID: 29266954 DOI: 10.1021/acs.nanolett.7b03720] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Optical near-field excitation of metallic nanostructures can be used to enhance photochemical reactions. The enhancement under visible light illumination is of particular interest because it can facilitate the use of sunlight to promote photocatalytic chemical and energy conversion. However, few studies have yet addressed optical near-field induced chemistry, in particular at the single-molecule level. In this Letter, we report the near-field enhanced tautomerization of porphycene on a Cu(111) surface in a scanning tunneling microscope (STM) junction. The light-induced tautomerization is mediated by photogenerated carriers in the Cu substrate. It is revealed that the reaction cross section is significantly enhanced in the presence of a Au tip compared to the far-field induced process. The strong enhancement occurs in the red and near-infrared spectral range for Au tips, whereas a W tip shows a much weaker enhancement, suggesting that excitation of the localized plasmon resonance contributes to the process. Additionally, using the precise tip-surface distance control of the STM, the near-field enhanced tautomerization is examined in and out of the tunneling regime. Our results suggest that the enhancement is attributed to the increased carrier generation rate via decay of the excited near-field in the STM junction. Additionally, optically excited tunneling electrons also contribute to the process in the tunneling regime.
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Affiliation(s)
- Hannes Böckmann
- Department of Physical Chemistry, Fritz-Haber Institute of the Max-Planck Society , Faradayweg 4-6, 14195 Berlin, Germany
| | - Sylwester Gawinkowski
- Institute of Physical Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, Warsaw 01-224, Poland
| | - Jacek Waluk
- Institute of Physical Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, Warsaw 01-224, Poland
- Faculty of Mathematics and Natural Sciences, College of Science, Cardinal Stefan Wyszyński University , Dewajtis 5, 01-815 Warsaw, Poland
| | - Markus B Raschke
- Department of Physics, Department of Chemistry, and JILA, University of Colorado , Boulder, Colorado 80309, United States
| | - Martin Wolf
- Department of Physical Chemistry, Fritz-Haber Institute of the Max-Planck Society , Faradayweg 4-6, 14195 Berlin, Germany
| | - Takashi Kumagai
- Department of Physical Chemistry, Fritz-Haber Institute of the Max-Planck Society , Faradayweg 4-6, 14195 Berlin, Germany
- JST-PRESTO , 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
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