1
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Shibuta M, Nakajima A. Imaging of ultrafast photoexcited electron dynamics in pentacene nanocrystals on a graphite substrate. NANOSCALE 2024; 16:12397-12405. [PMID: 38832543 DOI: 10.1039/d4nr00720d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2024]
Abstract
Understanding molecular film growth on substrates and the ultrafast electron dynamics at their interface is crucial for advancing next-generation organic electronics. We have focused on studying the ultrafast photoexcited electron dynamics in nanoscale organic crystals of an aromatic molecule, pentacene, on a two-dimensional material of graphite substrate. Through the use of time-resolved two-photon photoelectron emission microscopy (2P-PEEM), we have visualized the ultrafast lateral evolution of photoexcited electrons. By resonantly tuning the incident photon to excite pentacene molecules, polarization-dependent 2P-PEEM has revealed that pentacene nanocrystals (sub- to several μm) on the substrate exhibit a preferential orientation, in which a molecular π-orbital contacts the substrate in a "lying flat" orientation, facilitating electron transfer to the substrate. The time-resolved 2P-PEEM captures the motion of excited electrons in a femto- to pico-second timescale, clearly imaging the ultrafast charge transfer and lateral expansion two-dimensionally on the graphite substrate. Moreover, we found that the lying-flat molecular orientation of pentacene nanocrystals is transformable into a "standing-up" one through gentle heating up to 50 °C. These experimental insights using time-resolved 2P-PEEM will be highly valuable in enhancing the photofunctionalities of organic electronic devices by controlled molecular deposition.
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Affiliation(s)
- Masahiro Shibuta
- Keio Institute of Pure and Applied Sciences (KiPAS), Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
| | - Atsushi Nakajima
- Keio Institute of Pure and Applied Sciences (KiPAS), Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
- Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
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2
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Shibuta M, Nakajima A. Two-Photon Photoemission Spectroscopy and Microscopy for Electronic and Plasmonic Characterizations of Molecularly Designed Organic Surfaces. J Phys Chem Lett 2023; 14:3285-3295. [PMID: 36988100 DOI: 10.1021/acs.jpclett.3c00043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Functional surfaces decorated with organic molecules and/or nanoclusters (NCs) composed of several tens of atoms are promising for use in future photoelectronic substrates, whose functionalities are governed by molecular local electronic/plasmonic excitations at the interfaces. Here, we combine two-photon photoemission spectroscopy (2P-PES) and microscopy (2P-PEEM) to investigate the local excited-state dynamics at organic surfaces functionalized with NCs. The 2P-PES and 2P-PEEM for organic fullerene (C60) layers on graphite and Au substrates demonstrated photophysical characterization of electronic and plasmonic properties, including propagating surface plasmon polaritons (SPPs). The SPP propagation at the Au interface buried by overlayered C60 can be visualized by Agn NC deposition, which enhances plasmon-induced hot electrons, where the threshold number of Ag atoms (n ≥ 9) for the plasmonic response is revealed by the size dependence of 2P-PES for Agn NCs on C60 layers.
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Affiliation(s)
- Masahiro Shibuta
- Department of Physics and Electronics, Graduate School of Engineering, Osaka Metropolitan University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
- Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
- Keio Institute of Pure and Applied Sciences (KiPAS), Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - Atsushi Nakajima
- Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
- Keio Institute of Pure and Applied Sciences (KiPAS), Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
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3
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Shibuta M, Nakajima A. Spectroscopic imaging of photoexcited states at a polycrystalline copper metal surface via two-photon photoelectron emission microscopy. Chem Phys Lett 2022. [DOI: 10.1016/j.cplett.2022.139909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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4
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Shibuta M, Inoue T, Kamoshida T, Eguchi T, Nakajima A. Al13− and B@Al12− superatoms on a molecularly decorated substrate. Nat Commun 2022; 13:1336. [PMID: 35288553 PMCID: PMC8921336 DOI: 10.1038/s41467-022-29034-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 02/17/2022] [Indexed: 11/20/2022] Open
Abstract
Aluminum nanoclusters (Aln NCs), particularly Al13− (n = 13), exhibit superatomic behavior with interplay between electron shell closure and geometrical packing in an anionic state. To fabricate superatom (SA) assemblies, substrates decorated with organic molecules can facilitate the optimization of cluster–surface interactions, because the molecularly local interactions for SAs govern the electronic properties via molecular complexation. In this study, Aln NCs are soft-landed on organic substrates pre-deposited with n-type fullerene (C60) and p-type hexa-tert-butyl-hexa-peri-hexabenzocoronene (HB-HBC, C66H66), and the electronic states of Aln are characterized by X-ray photoelectron spectroscopy and chemical oxidative measurements. On the C60 substrate, Aln is fixed to be cationic but highly oxidative; however, on the HB-HBC substrate, they are stably fixed as anionic Aln− without any oxidations. The results reveal that the careful selection of organic molecules controls the design of assembled materials containing both Al13− and boron-doped B@Al12− SAs through optimizing the cluster–surface interactions. Anionic aluminium clusters are promising candidates for the fabrication of superatom-assembled nanomaterials. Here, the authors report enhanced stability for Al13− and boron-doped B@Al12− on a molecularly decorated p-type organic substrate.
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5
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Rosławska A, Merino P, Leon CC, Grewal A, Etzkorn M, Kuhnke K, Kern K. Gigahertz Frame Rate Imaging of Charge-Injection Dynamics in a Molecular Light Source. NANO LETTERS 2021; 21:4577-4583. [PMID: 34038142 PMCID: PMC8193635 DOI: 10.1021/acs.nanolett.1c00328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 04/22/2021] [Indexed: 06/12/2023]
Abstract
Light sources on the scale of single molecules can be addressed and characterized at their proper sub-nanometer scale by scanning tunneling microscopy-induced luminescence (STML). Such a source can be driven by defined short charge pulses while the luminescence is detected with sub-nanosecond resolution. We introduce an approach to concurrently image the molecular emitter, which is based on an individual defect, with its local environment along with its luminescence dynamics at a resolution of a billion frames per second. The observed dynamics can be assigned to the single electron capture occurring in the low-nanosecond regime. While the emitter's location on the surface remains fixed, the scanning of the tip modifies the energy landscape for charge injection into the defect. The principle of measurement is extendable to fundamental processes beyond charge transfer, like exciton diffusion.
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Affiliation(s)
- Anna Rosławska
- Max-Planck-Institut
für Festkörperforschung, D-70569 Stuttgart, Germany
- Université
de Strasbourg, CNRS, IPCMS, UMR 7504, F-67000 Strasbourg, France
| | - Pablo Merino
- Max-Planck-Institut
für Festkörperforschung, D-70569 Stuttgart, Germany
- Instituto
de Ciencia de Materiales de Madrid, CSIC, E-28049 Madrid, Spain
- Instituto
de Física Fundamental, CSIC, E-28006 Madrid, Spain
| | | | - Abhishek Grewal
- Max-Planck-Institut
für Festkörperforschung, D-70569 Stuttgart, Germany
| | - Markus Etzkorn
- Max-Planck-Institut
für Festkörperforschung, D-70569 Stuttgart, Germany
- Institut
für Angewandte Physik, TU Braunschweig, D-38106 Braunschweig, Germany
| | - Klaus Kuhnke
- Max-Planck-Institut
für Festkörperforschung, D-70569 Stuttgart, Germany
| | - Klaus Kern
- Max-Planck-Institut
für Festkörperforschung, D-70569 Stuttgart, Germany
- Institut
de Physique, École Polytechnique Fédérale de
Lausanne, CH-1015 Lausanne, Switzerland
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6
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Shibuta M, Yamamoto K, Ohta T, Inoue T, Mizoguchi K, Nakaya M, Eguchi T, Nakajima A. Confined Hot Electron Relaxation at the Molecular Heterointerface of the Size-Selected Plasmonic Noble Metal Nanocluster and Layered C 60. ACS NANO 2021; 15:1199-1209. [PMID: 33411503 DOI: 10.1021/acsnano.0c08248] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The plasmonic response of metallic nanostructures plays a key role in amplifying photocatalytic and photoelectric conversion. Since the plasmonic behavior of noble metal nanoparticles is known to generate energetic charge carriers such as hot electrons, it is expected that the hot electrons can enhance conversion efficiency if they are transferred into a neighboring molecule or semiconductor. However, the method of transferring the energized charge carriers from the plasmonically generated hot electrons to the neighboring species remains controversial. Herein, we fabricated a molecularly well-defined heterointerface between the size-selected plasmonic noble-metal nanoclusters (NCs) of Agn (n = 3-55)/Aun (n = 21) and the organic C60 film to investigate hot electron generation and relaxation dynamics using time-resolved two-photon photoemission (2PPE) spectroscopy. By tuning the NC size and the polarization of the femtosecond excitation photons, the plasmonic behavior is characterized by 2PPE intensity enhancement by 10-100 times magnitude, which emerge at n ≥ 9 for Agn NCs. The 2PPE spectra exhibit contributions from low-energy electrons forming coherent plasmonic currents and hot electrons with an excitation energy up to photon energy owing to two-photon excitation of an occupied state of the Agn NC below the Fermi level. The time-resolved pump-probe measurements demonstrate that plasmon dephasing generates hot electrons which undergo electron-electron scattering. However, no photoemission occurs via the charge transfer state forming Agn+C60- located in the vicinity of the Fermi level. Thus, this study reveals the mechanism of ultrafast confined hot electron relaxation within plasmonic Agn NCs at the molecular heterointerface.
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Affiliation(s)
- Masahiro Shibuta
- Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, D-35032 Marburg, Germany
| | | | | | | | | | - Masato Nakaya
- Nakajima Designer Nanocluster Assembly Project, ERATO, Japan Science and Technology Agency (JST), 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012, Japan
| | - Toyoaki Eguchi
- Nakajima Designer Nanocluster Assembly Project, ERATO, Japan Science and Technology Agency (JST), 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012, Japan
| | - Atsushi Nakajima
- Nakajima Designer Nanocluster Assembly Project, ERATO, Japan Science and Technology Agency (JST), 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012, Japan
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7
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Yamagiwa K, Shibuta M, Nakajima A. Visualization of Surface Plasmons Propagating at the Buried Organic/Metal Interface with Silver Nanocluster Sensitizers. ACS NANO 2020; 14:2044-2052. [PMID: 31999096 DOI: 10.1021/acsnano.9b08653] [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
Visualization of surface plasmon polariton (SPP) propagation at dielectric/metal interfaces is indispensable in providing opportunities for the precise designing and controlling of the functionalities of future plasmonic nanodevices. Here, we report the visualization of SPPs propagating along the buried organic/metal interface of fullerene (C60)/Au(111), through dual-colored two-photon photoemission electron microscopy (2P-PEEM) which precisely visualizes the SPP propagation of plasmonic metal nanostructures. Although SPPs excited by near-infrared photons at the few monolayer C60/Au(111) interface are clearly visualized as interference beat patterns between the SPPs and incident light, faithfully reflecting SPP properties modulated by the overlayer, photoemission signals are suppressed for thicker C60 films, due to less valence electrons participating in 2P-photoemission processes. With the use of silver (Agn (n = 21 and 55)) nanoclusters, which exhibit enhancement of overall photoemission intensities due to localized surface plasmons functioning as SPP sensitizers, it is revealed that the 2P-PEEM is applicable to the imaging of SPPs for thick C60/Au(111) interfaces, where SPP properties are hardly modulated by the added small amount (∼0.1 monolayer) of Agn sensitizers.
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Affiliation(s)
- Kana Yamagiwa
- Department of Chemistry, Faculty of Science and Technology , Keio University , 3-14-1 Hiyoshi , Kohoku-ku, Yokohama 223-8522 , Japan
| | - Masahiro Shibuta
- Keio Institute of Pure and Applied Science (KiPAS) , Keio University , 3-14-1 Hiyoshi , Kohoku-ku, Yokohama 223-8522 , Japan
| | - Atsushi Nakajima
- Department of Chemistry, Faculty of Science and Technology , Keio University , 3-14-1 Hiyoshi , Kohoku-ku, Yokohama 223-8522 , Japan
- Keio Institute of Pure and Applied Science (KiPAS) , Keio University , 3-14-1 Hiyoshi , Kohoku-ku, Yokohama 223-8522 , Japan
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8
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Stadtmüller B, Emmerich S, Jungkenn D, Haag N, Rollinger M, Eich S, Maniraj M, Aeschlimann M, Cinchetti M, Mathias S. Strong modification of the transport level alignment in organic materials after optical excitation. Nat Commun 2019; 10:1470. [PMID: 30931921 PMCID: PMC6443800 DOI: 10.1038/s41467-019-09136-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 02/25/2019] [Indexed: 11/20/2022] Open
Abstract
Organic photovoltaic devices operate by absorbing light and generating current. These two processes are governed by the optical and transport properties of the organic semiconductor. Despite their common microscopic origin-the electronic structure-disclosing their dynamical interplay is far from trivial. Here we address this issue by time-resolved photoemission to directly investigate the correlation between the optical and transport response in organic materials. We reveal that optical generation of non-interacting excitons in a fullerene film results in a substantial redistribution of all transport levels (within 0.4 eV) of the non-excited molecules. As all observed dynamics evolve on identical timescales, we conclude that optical and transport properties are completely interlinked. This finding paves the way for developing novel concepts for transport level engineering on ultrafast time scales that could lead to novel functional optoelectronic devices.
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Affiliation(s)
- Benjamin Stadtmüller
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany.
- Graduate School of Excellence Materials Science in Mainz, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany.
| | - Sebastian Emmerich
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
- Graduate School of Excellence Materials Science in Mainz, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
| | - Dominik Jungkenn
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
| | - Norman Haag
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
| | - Markus Rollinger
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
| | - Steffen Eich
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
| | - Mahalingam Maniraj
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
| | - Martin Aeschlimann
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
| | - Mirko Cinchetti
- Experimentelle Physik VI, Technische Universität Dortmund, 44221, Dortmund, Germany
| | - Stefan Mathias
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
- International Center for Advanced Studies of Energy Conversion (ICASEC), Georg-August-Universität Göttingen, 37077, Göttingen, Germany
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9
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Ravikumar A, Kladnik G, Müller M, Cossaro A, Bavdek G, Patera LL, Sánchez-Portal D, Venkataraman L, Morgante A, Brivio GP, Cvetko D, Fratesi G. Tuning ultrafast electron injection dynamics at organic-graphene/metal interfaces. NANOSCALE 2018; 10:8014-8022. [PMID: 29667672 DOI: 10.1039/c7nr08737c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We compare the ultrafast charge transfer dynamics of molecules on epitaxial graphene and bilayer graphene grown on Ni(111) interfaces through first principles calculations and X-ray resonant photoemission spectroscopy. We use 4,4'-bipyridine as a prototypical molecule for these explorations as the energy level alignment of core-excited molecular orbitals allows ultrafast injection of electrons from a substrate to a molecule on a femtosecond timescale. We show that the ultrafast injection of electrons from the substrate to the molecule is ∼4 times slower on weakly coupled bilayer graphene than on epitaxial graphene. Through our experiments and calculations, we can attribute this to a difference in the density of states close to the Fermi level between graphene and bilayer graphene. We therefore show how graphene coupling with the substrate influences charge transfer dynamics between organic molecules and graphene interfaces.
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Affiliation(s)
- Abhilash Ravikumar
- Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via Cozzi 55, 20125 Milano, Italy.
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10
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Boström EV, Mikkelsen A, Verdozzi C, Perfetto E, Stefanucci G. Charge Separation in Donor-C 60 Complexes with Real-Time Green Functions: The Importance of Nonlocal Correlations. NANO LETTERS 2018; 18:785-792. [PMID: 29266952 DOI: 10.1021/acs.nanolett.7b03995] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We use the nonequilibrium Green function (NEGF) method to perform real-time simulations of the ultrafast electron dynamics of photoexcited donor-C60 complexes modeled by a Pariser-Parr-Pople Hamiltonian. The NEGF results are compared to mean-field Hartree-Fock (HF) calculations to disentangle the role of correlations. Initial benchmarking against numerically highly accurate time-dependent density matrix renormalization group calculations verifies the accuracy of NEGF. We then find that charge-transfer (CT) excitons partially decay into charge separated (CS) states if dynamical nonlocal correlation corrections are included. This CS process occurs in ∼10 fs after photoexcitation. In contrast, the probability of exciton recombination is almost 100% in HF simulations. These results are largely unaffected by nuclear vibrations; the latter become however essential whenever level misalignment hinders the CT process. The robust nature of our findings indicates that ultrafast CS driven by correlation-induced decoherence may occur in many organic nanoscale systems, but it will only be correctly predicted by theoretical treatments that include time-nonlocal correlations.
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Affiliation(s)
- Emil Viñas Boström
- Lund University , Department of Physics and European Theoretical Spectroscopy Facility (ETSF), P.O. Box 118, 221 00 Lund, Sweden
| | - Anders Mikkelsen
- Lund University , Department of Physics and NanoLund, P.O. Box 118, 221 00 Lund, Sweden
| | - Claudio Verdozzi
- Lund University , Department of Physics and European Theoretical Spectroscopy Facility (ETSF), P.O. Box 118, 221 00 Lund, Sweden
| | - Enrico Perfetto
- CNR-ISM , Division of Ultrafast Processes in Materials (FLASHit), Area della Ricerca di Roma 1, Via Salaria Km 29.3, I-00016 Monterotondo Scalo, Italy
- Dipartimento di Fisica and European Theoretical Spectroscopy Facility (ETSF), Università di Roma Tor Vergata , Via della Ricerca Scientifica 1, 00133 Rome, Italy
| | - Gianluca Stefanucci
- Dipartimento di Fisica and European Theoretical Spectroscopy Facility (ETSF), Università di Roma Tor Vergata , Via della Ricerca Scientifica 1, 00133 Rome, Italy
- INFN, Sezione di Roma Tor Vergata , Via della Ricerca Scientifica 1, 00133 Rome, Italy
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11
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Shibuta M, Yamamoto K, Yamagiwa K, Eguchi T, Nakajima A. Photoexcited Electron-transfer Properties of C60 Film on Graphite and on Au(111) Interfaces Studied by Two-photon Photoemission Spectroscopy. CHEM LETT 2017. [DOI: 10.1246/cl.170641] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Masahiro Shibuta
- Keio Institute of Pure and Applied Science (KiPAS), Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522
| | - Kazuo Yamamoto
- Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522
| | - Kana Yamagiwa
- Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522
| | - Toyoaki Eguchi
- Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522
| | - Atsushi Nakajima
- Keio Institute of Pure and Applied Science (KiPAS), Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522
- Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522
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12
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Dąbrowski M, Dai Y, Petek H. Ultrafast Microscopy: Imaging Light with Photoelectrons on the Nano-Femto Scale. J Phys Chem Lett 2017; 8:4446-4455. [PMID: 28853892 DOI: 10.1021/acs.jpclett.7b00904] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Experimental methods for ultrafast microscopy are advancing rapidly. Promising methods combine ultrafast laser excitation with electron-based imaging or rely on super-resolution optical techniques to enable probing of matter on the nano-femto scale. Among several actively developed methods, ultrafast time-resolved photoemission electron microscopy provides several advantages, among which the foremost are that time resolution is limited only by the laser source and it is immediately capable of probing of coherent phenomena in solid-state materials and surfaces. Here we present recent progress in interference imaging of plasmonic phenomena in metal nanostructures enabled by combining a broadly tunable femtosecond laser excitation source with a low-energy electron microscope.
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Affiliation(s)
- Maciej Dąbrowski
- Department of Physics and Astronomy and Pittsburgh Quantum Institute, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
| | - Yanan Dai
- Department of Physics and Astronomy and Pittsburgh Quantum Institute, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
| | - Hrvoje Petek
- Department of Physics and Astronomy and Pittsburgh Quantum Institute, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States
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13
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Shibuta M, Hirata N, Eguchi T, Nakajima A. Photoexcited State Confinement in Two-Dimensional Crystalline Anthracene Monolayer at Room Temperature. ACS NANO 2017; 11:4307-4314. [PMID: 28399361 DOI: 10.1021/acsnano.7b01506] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Organic thin film electronics place a high demand on bottom-up technology to form a two-dimensionally (2D) functional unit consisting of a single molecular crystalline layer bound to a layered structure. As the strong interaction between a substrate and molecules makes it difficult to evaluate the electronic properties of organic films, the nature of electronic excited states has not been elucidated. Here, we study a 2D crystalline anthracene monolayer electronically decoupled by alkanethiolates on a gold substrate using scanning tunneling microscopy and time-resolved two-photon photoemission spectroscopy and unravel the geometric/electronic structures and excited electron dynamics. Our data reveal that dispersive 2D excited electrons on the surface can be highly coupled with an annihilation of nondispersive excitons that facilitate electron emission with vibronic interaction. Our results provide a fundamental framework for understanding photoexcited anthracene monolayer and show how the coupling between dispersive and nondispersive excited states may assist charge separation in crystalline molecular layers.
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Affiliation(s)
- Masahiro Shibuta
- Keio Institute of Pure and Applied Science (KiPAS), Keio University , 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - Naoyuki Hirata
- Nakajima Designer Nanocluster Assembly Project, ERATO, Japan Science and Technology Agency (JST) , 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012, Japan
- Department of Chemistry, Faculty of Science and Technology, Keio University , 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - Toyoaki Eguchi
- Nakajima Designer Nanocluster Assembly Project, ERATO, Japan Science and Technology Agency (JST) , 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012, Japan
- Department of Chemistry, Faculty of Science and Technology, Keio University , 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - Atsushi Nakajima
- Keio Institute of Pure and Applied Science (KiPAS), Keio University , 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
- Nakajima Designer Nanocluster Assembly Project, ERATO, Japan Science and Technology Agency (JST) , 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012, Japan
- Department of Chemistry, Faculty of Science and Technology, Keio University , 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
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14
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Tan S, Liu L, Dai Y, Ren J, Zhao J, Petek H. Ultrafast Plasmon-Enhanced Hot Electron Generation at Ag Nanocluster/Graphite Heterojunctions. J Am Chem Soc 2017; 139:6160-6168. [DOI: 10.1021/jacs.7b01079] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Shijing Tan
- Department
of Physics and Astronomy and Pittsburgh Quantum Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Liming Liu
- ICQD/Hefei
National Laboratory for Physical Sciences at Microscale, and Key Laboratory
of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences,
and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yanan Dai
- Department
of Physics and Astronomy and Pittsburgh Quantum Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Jindong Ren
- Department
of Physics and Astronomy and Pittsburgh Quantum Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Jin Zhao
- Department
of Physics and Astronomy and Pittsburgh Quantum Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
- ICQD/Hefei
National Laboratory for Physical Sciences at Microscale, and Key Laboratory
of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences,
and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Hrvoje Petek
- Department
of Physics and Astronomy and Pittsburgh Quantum Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
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