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Castrillo-Bodero R, Blanco-Rey M, Ali K, Ortega JE, Schiller F, Fernández L. Tuning the carrier injection barrier of hybrid metal-organic interfaces on rare earth-gold surface compounds. NANOSCALE 2023; 15:4090-4100. [PMID: 36744853 DOI: 10.1039/d2nr06440e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Magnetic hybrid metal-organic interfaces possess a great potential in areas such as organic spintronics and quantum information processing. However, tuning their carrier injection barriers on-demand is fundamental for the implementation in technological devices. We have prepared hybrid metal-organic interfaces by the adsorption of copper phthalocyanine CuPc on REAu2 surfaces (RE = Gd, Ho and Yb) and studied their growth, electrostatics and electronic structure. CuPc exhibits a long-range commensurability and a vacuum level pinning of the molecular energy levels. We observe a significant effect of the RE valence of the substrate on the carrier injection barrier of the hybrid metal-organic interface. CuPc adsorbed on trivalent RE-based surfaces (HoAu2 and GdAu2) exhibits molecular level energies that may allow injection carriers significantly closer to an ambipolar injection behavior than in the divalent case (YbAu2).
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Affiliation(s)
- R Castrillo-Bodero
- Centro de Física de Materiales CSIC-UPV/EHU-Materials Physics Center, 20018 San Sebastián, Spain.
| | - M Blanco-Rey
- Universidad del País Vasco UPV/EHU, Dpto. de Polímeros y Materiales Avanzados: Física, Química y Tecnología, 20018 San Sebastián, Spain
- Donostia International Physics Center, 20018 Donostia-San Sebastián, Spain
| | - K Ali
- Centro de Física de Materiales CSIC-UPV/EHU-Materials Physics Center, 20018 San Sebastián, Spain.
- Donostia International Physics Center, 20018 Donostia-San Sebastián, Spain
- Chalmers University of Technology, Chalmersplatsen 4, Götenborg, 41296, Sweden
| | - J E Ortega
- Universidad del País Vasco UPV/EHU, Dpto. Física Aplicada I, 20018 San Sebastián, Spain
- Centro de Física de Materiales CSIC-UPV/EHU-Materials Physics Center, 20018 San Sebastián, Spain.
- Donostia International Physics Center, 20018 Donostia-San Sebastián, Spain
| | - F Schiller
- Centro de Física de Materiales CSIC-UPV/EHU-Materials Physics Center, 20018 San Sebastián, Spain.
- Donostia International Physics Center, 20018 Donostia-San Sebastián, Spain
| | - L Fernández
- Centro de Física de Materiales CSIC-UPV/EHU-Materials Physics Center, 20018 San Sebastián, Spain.
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2
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Liu J, Jiang X, Li X, Ma X, Sun X, Zheng Q, Cui X, Tan S, Zhao J, Wang B. Time- and momentum-resolved image-potential states of 2H-MoS 2 surface. Phys Chem Chem Phys 2021; 23:26336-26342. [PMID: 34787611 DOI: 10.1039/d1cp03527d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Rydberg-like image potential states (IPSs) form special series surface states on metal and semiconducting surfaces. Here, using time-resolved and momentum-resolved multi-photon photoemission (mPPE), we measured the energy positions, band dispersion, and carrier lifetimes of IPSs at the 2H-MoS2 surface. The energy minima of the IPSs (n = 1 and 2) were located at 0.77 and 0.21 eV below the vacuum level. In addition, the effective masses of these two IPSs are close to the rest mass of the free electron, clearly showing nearly-free-electron character. These properties suggest a good screening effect in the MoS2 parallel to the surface. The multi-photon resonances between the valence band and IPS (n = 1) are observed, showing a k‖-momentum-dependent behavior. Our time-resolved mPPE measurements show that the lifetime of photoexcited electrons in the IPS (n = 1) is about 33 fs.
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Affiliation(s)
- Jianyi Liu
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
| | - Xiang Jiang
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
| | - Xintong Li
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
| | - Xiaochuan Ma
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
| | - Xia Sun
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
| | - Qijing Zheng
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
| | - Xuefeng Cui
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
| | - Shijing Tan
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
| | - Jin Zhao
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
| | - Bing Wang
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information & Quantum Physics, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
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3
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Stein A, Rolf D, Lotze C, Günther B, Gade LH, Franke KJ, Tegeder P. Band Formation at Interfaces Between N-Heteropolycycles and Gold Electrodes. J Phys Chem Lett 2021; 12:947-951. [PMID: 33440118 DOI: 10.1021/acs.jpclett.0c03630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Efficient charge injection at organic semiconductor/metal interfaces is crucial for the performance of organic field effect transistors. Interfacial hybrid band formation between electronic states of the organic compound and the metal electrode facilitates effective charge injection. Here, we show that a long-range ordered monolayer of a flat-lying N-heteropolycyclic aromatic compound on Au(111) leads to dispersing occupied and unoccupied interfacial hybrid bands. Using angle-resolved two-photon photoemission we determine their energy level alignment and dispersion relations. We suggest that band formation proceeds via hybridization of a localized occupied molecular state with the d-bands of the Au substrate, where the large effective mass of the d-bands is significantly reduced in the hybrid band. Hybridization of an unoccupied molecular state with the Au sp-band leads to a band with an even smaller effective mass.
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Affiliation(s)
- Arnulf Stein
- Ruprecht-Karls-Universität Heidelberg, Physikalisch-Chemisches Institut, Im Neuenheimer Feld 253, 69120 Heidelberg, Germany
| | - Daniela Rolf
- Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany
| | - Christian Lotze
- Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany
| | - Benjamin Günther
- Ruprecht-Karls-Universität Heidelberg, Anorganisch-Chemisches Institut, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
| | - Lutz H Gade
- Ruprecht-Karls-Universität Heidelberg, Anorganisch-Chemisches Institut, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
| | - Katharina J Franke
- Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany
| | - Petra Tegeder
- Ruprecht-Karls-Universität Heidelberg, Physikalisch-Chemisches Institut, Im Neuenheimer Feld 253, 69120 Heidelberg, Germany
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4
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Yang X, Egger L, Fuchsberger J, Unzog M, Lüftner D, Hajek F, Hurdax P, Jugovac M, Zamborlini G, Feyer V, Koller G, Puschnig P, Tautz FS, Ramsey MG, Soubatch S. Coexisting Charge States in a Unary Organic Monolayer Film on a Metal. J Phys Chem Lett 2019; 10:6438-6445. [PMID: 31573816 DOI: 10.1021/acs.jpclett.9b02231] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The electronic and geometric structures of tetracene films on Ag(110) and Cu(110) have been studied with photoemission tomography and compared to that of pentacene. Despite similar energy level alignment of the two oligoacenes on these surfaces revealed by conventional ultraviolet photoelectron spectroscopy, the momentum-space resolved photoemission tomography reveals a significant difference in both structural and electronic properties of tetracene and pentacene films. Particularly, the saturated monolayer of tetracene on Ag(110) is found to consist of two molecular species that, despite having the same orientation, are electronically very different-while one molecule remains neutral, another is charged because of electron donation from the substrate.
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Affiliation(s)
- Xiaosheng Yang
- Peter Grünberg Institut (PGI-3) , Forschungszentrum Jülich , 52425 Jülich , Germany
- Jülich Aachen Research Alliance (JARA)-Fundamentals of Future Information Technology , 52425 Jülich , Germany
- Experimental Physics IV A , RWTH Aachen University , 52074 Aachen , Germany
| | - Larissa Egger
- Institute of Physics , University of Graz , NAWI Graz, 8010 Graz , Austria
| | - Jana Fuchsberger
- Institute of Physics , University of Graz , NAWI Graz, 8010 Graz , Austria
| | - Martin Unzog
- Institute of Physics , University of Graz , NAWI Graz, 8010 Graz , Austria
| | - Daniel Lüftner
- Institute of Physics , University of Graz , NAWI Graz, 8010 Graz , Austria
| | - Felix Hajek
- Institute of Physics , University of Graz , NAWI Graz, 8010 Graz , Austria
| | - Philipp Hurdax
- Institute of Physics , University of Graz , NAWI Graz, 8010 Graz , Austria
| | - Matteo Jugovac
- Peter Grünberg Institut (PGI-6) , Forschungszentrum Jülich , 52425 Jülich , Germany
| | - Giovanni Zamborlini
- Peter Grünberg Institut (PGI-6) , Forschungszentrum Jülich , 52425 Jülich , Germany
| | - Vitaliy Feyer
- Peter Grünberg Institut (PGI-6) , Forschungszentrum Jülich , 52425 Jülich , Germany
| | - Georg Koller
- Institute of Physics , University of Graz , NAWI Graz, 8010 Graz , Austria
| | - Peter Puschnig
- Institute of Physics , University of Graz , NAWI Graz, 8010 Graz , Austria
| | - F Stefan Tautz
- Peter Grünberg Institut (PGI-3) , Forschungszentrum Jülich , 52425 Jülich , Germany
- Jülich Aachen Research Alliance (JARA)-Fundamentals of Future Information Technology , 52425 Jülich , Germany
- Experimental Physics IV A , RWTH Aachen University , 52074 Aachen , Germany
| | - Michael G Ramsey
- Institute of Physics , University of Graz , NAWI Graz, 8010 Graz , Austria
| | - Serguei Soubatch
- Peter Grünberg Institut (PGI-3) , Forschungszentrum Jülich , 52425 Jülich , Germany
- Jülich Aachen Research Alliance (JARA)-Fundamentals of Future Information Technology , 52425 Jülich , Germany
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5
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Cui X, Han D, Guo H, Zhou L, Qiao J, Liu Q, Cui Z, Li Y, Lin C, Cao L, Ji W, Petek H, Feng M. Realizing nearly-free-electron like conduction band in a molecular film through mediating intermolecular van der Waals interactions. Nat Commun 2019; 10:3374. [PMID: 31358744 PMCID: PMC6662711 DOI: 10.1038/s41467-019-11300-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 07/01/2019] [Indexed: 12/03/2022] Open
Abstract
Collective molecular physical properties can be enhanced from their intrinsic characteristics by templating at material interfaces. Here we report how a black phosphorous (BP) substrate concatenates a nearly-free-electron (NFE) like conduction band of a C60 monolayer. Scanning tunneling microscopy reveals the C60 lowest unoccupied molecular orbital (LUMO) band is strongly delocalized in two-dimensions, which is unprecedented for a molecular semiconductor. Experiment and theory show van der Waals forces between C60 and BP reduce the inter-C60 distance and cause mutual orientation, thereby optimizing the π-π wave function overlap and forming the NFE-like band. Electronic structure and carrier mobility calculations predict that the NFE band of C60 acquires an effective mass of 0.53-0.70 me (me is the mass of free electrons), and has carrier mobility of ~200 to 440 cm2V-1s-1. The substrate-mediated intermolecular van der Waals interactions provide a route to enhance charge delocalization in fullerenes and other organic semiconductors.
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Affiliation(s)
- Xingxia Cui
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan, 430072, China
| | - Ding Han
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan, 430072, China
| | - Hongli Guo
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan, 430072, China
| | - Linwei Zhou
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-Nano Devices, Department of Physics, Renmin University of China, Beijing, 100872, China
| | - Jingsi Qiao
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-Nano Devices, Department of Physics, Renmin University of China, Beijing, 100872, China
| | - Qing Liu
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan, 430072, China
| | - Zhihao Cui
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan, 430072, China
| | - Yafei Li
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan, 430072, China
| | - Chungwei Lin
- Mitsubishi Electric Research Laboratories, 201 Broadway, Cambridge, MA, 02139, USA
| | - Limin Cao
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan, 430072, China
| | - Wei Ji
- Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-Nano Devices, Department of Physics, Renmin University of China, Beijing, 100872, China.
| | - Hrvoje Petek
- Department of Physics and Astronomy and Pittsburgh Quantum Institute, University of Pittsburgh, Pittsburgh, PA, 15260, USA.
| | - Min Feng
- School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan, 430072, China.
- Institute for Advanced Studies, Wuhan University, Wuhan, 430072, China.
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6
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Zaitsev NL, Tonner R, Nechaev IA. Spin-orbit split two-dimensional states of BiTeI/Au(1 1 1) interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:204001. [PMID: 30776790 DOI: 10.1088/1361-648x/ab07fa] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We present an ab initio study of interfaces formed by placing a single trilayer of BiTeI on the Au(1 1 1) surface. We consider two possible interfaces with the parallel and antiparallel orientation of the trilayer dipole moment with respect to the surface normal, i.e. Te-Bi-I/Au(1 1 1) and I-Bi-Te/Au(1 1 1). We show that the resulting interface state that originates from the modified spin-orbit split surface state of the clean Au(1 1 1) surface resides at high energy above the Fermi level and acquires a large spin-splitting and reversal helicity as compared with the original surface state. The former lowest conduction state of the trilayer, which is one of the hitherto known giant Rashba spin-split states of few-atomic-layer structures, becomes partly occupied. In the I-Bi-Te/Au(1 1 1) interface, this state represents a Rashba system with strong spin-orbit interaction, where the outer branch of the spin-split state is mostly populated.
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Affiliation(s)
- N L Zaitsev
- Laboratory of Theoretical Physics, Institute of Molecule and Crystal Physics Ufa Research Center of Russian Academy of Sciences, 450075, Ufa, Russia
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7
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Stein A, Rolf D, Lotze C, Czekelius C, Franke KJ, Tegeder P. Electronic structure of an iron porphyrin derivative on Au(1 1 1). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:044002. [PMID: 30523801 DOI: 10.1088/1361-648x/aaf296] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Surface-bound porphyrins are promising candidates for molecular switches, electronics and spintronics. Here, we studied the structural and the electronic properties of Fe-tetra-pyridil-porphyrin adsorbed on Au(1 1 1) in the monolayer regime. We combined scanning tunneling microscopy/spectroscopy, ultraviolet photoemission, and two-photon photoemission to determine the energy levels of the frontier molecular orbitals. We also resolved an excitonic state with a binding energy of 420 meV, which allowed us to compare the electronic transport gap with the optical gap.
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Affiliation(s)
- Arnulf Stein
- Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 253, 69120 Heidelberg, Germany
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8
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Robertson C, González-Vázquez J, Corral I, Díaz-Tendero S, Díaz C. Nonadiabatic scattering of NO off Au3
clusters: A simple and robust diabatic state manifold generation method for multiconfigurational wavefunctions. J Comput Chem 2018; 40:794-810. [DOI: 10.1002/jcc.25764] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Revised: 10/28/2018] [Accepted: 11/01/2018] [Indexed: 01/19/2023]
Affiliation(s)
- Christopher Robertson
- Department of Chemistry and Centre for Scientific Computing; University Of Warwick, CV4 7AL; Coventry United Kingdom
| | - Jesús González-Vázquez
- Departamento de Química Módulo 13; Universidad Autónoma de Madrid, 28049; Madrid Spain
- Institute for Advanced Research in Chemistry (IAdChem); Universidad Autónoma de Madrid, 28049; Madrid Spain
| | - Ines Corral
- Institute for Advanced Research in Chemistry (IAdChem); Universidad Autónoma de Madrid, 28049; Madrid Spain
- Departamento de Química Módulo 13; Universidad Autónoma de Madrid, 28049; Madrid Spain
| | - Sergio Díaz-Tendero
- Condensed Matter Physics Center (IFIMAC); Universidad Autónoma de Madrid, 28049; Madrid Spain
- Departamento de Química Módulo 13; Universidad Autónoma de Madrid, 28049; Madrid Spain
- Institute for Advanced Research in Chemistry (IAdChem); Universidad Autónoma de Madrid, 28049; Madrid Spain
| | - Cristina Díaz
- Departamento de Química Módulo 13; Universidad Autónoma de Madrid, 28049; Madrid Spain
- Institute for Advanced Research in Chemistry (IAdChem); Universidad Autónoma de Madrid, 28049; Madrid Spain
- Condensed Matter Physics Center (IFIMAC); Universidad Autónoma de Madrid, 28049; Madrid Spain
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9
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Lerch A, Zimmermann JE, Namgalies A, Stallberg K, Höfer U. Two-photon photoemission spectroscopy of unoccupied electronic states at CuPc/PTCDA/Ag(1 1 1) interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:494001. [PMID: 30451155 DOI: 10.1088/1361-648x/aaec53] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The unoccupied electronic structure of stacked layers of copper(II)phthalocyanine (CuPc) and perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) on Ag(1 1 1) has been investigated by means of two-photon photoemission (2PPE). We find a rich electronic structure comprising at least five unoccupied electronic states which we identify based on their energetic position and their dispersion in momentum space. More specifically, we observe the first and the second image-potential states of the modified Ag(1 1 1) surface, as well as the metal-organic interface state (IS) inherent to the PTCDA/Ag(1 1 1) interface. Moreover, two additional molecular features are observed for the CuPc/PTCDA/Ag(1 1 1) system which we attribute to an unoccupied molecular orbital (LUMO + 2) of CuPc. The 2PPE intensity of the IS exhibits a pronounced dependence on the pump photon energy, which closely follows the optical absorption of the outer molecular layer. This strongly points to charge transfer from the optically excited molecules to the interface state.
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Affiliation(s)
- A Lerch
- Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, 35032 Marburg, Germany
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10
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Model potential for the description of metal/organic interface states. Sci Rep 2017; 7:46561. [PMID: 28425444 PMCID: PMC5397854 DOI: 10.1038/srep46561] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 03/17/2017] [Indexed: 01/08/2023] Open
Abstract
We present an analytical one-dimensional model potential for the description of electronic interface states that form at the interface between a metal surface and flat-lying adlayers of π-conjugated organic molecules. The model utilizes graphene as a universal representation of these organic adlayers. It predicts the energy position of the interface state as well as the overlap of its wave function with the bulk metal without free fitting parameters. We show that the energy of the interface state depends systematically on the bond distance between the carbon backbone of the adayers and the metal. The general applicability and robustness of the model is demonstrated by a comparison of the calculated energies with numerous experimental results for a number of flat-lying organic molecules on different closed-packed metal surfaces that cover a large range of bond distances.
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11
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Tonner R, Rosenow P, Jakob P. Molecular structure and vibrations of NTCDA monolayers on Ag(111) from density-functional theory and infrared absorption spectroscopy. Phys Chem Chem Phys 2016; 18:6316-28. [PMID: 26853185 DOI: 10.1039/c5cp06619k] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The structure and vibrational properties of the metal-organic interface of 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA) on Ag(111) were analysed using Fourier-transform infrared absorption spectroscopy in conjunction with density functional theory calculations including dispersion forces (PBE-D3). Mode assignments and polarizations as well as molecular distortions were determined for four adsorption geometries of NTCDA on top and bridge sites aligned either parallel or perpendicular to the Ag rows and compared to accurate calculations of the free molecule. This enables an in-depth understanding of surface effects on the computed and experimental vibrational spectra of the adsorbed NTCDA molecule. The molecule-substrate interaction comprises two major and equally important contributions: non-directional van der Waals forces between molecule and surface, and covalent bonding of the acyl oxygen atoms with underlying Ag atoms, which is quantified by charge-transfer analysis. Furthermore, adsorption energy calculations showed that the molecular axis of flat-lying NTCDA is oriented preferably in parallel to the Ag rows. The molecule is subject to particular distortions from the planar gas phase structure with covalent bonding leading to downward bending of the acyl oxygen atoms and Pauli repulsion to upward bending of the carbon core. In parallel, strong buckling of the silver surface was identified. As found in previous studies, the lowest unoccupied molecular orbital (LUMO) of the molecule slips below the Fermi level and becomes partially populated upon adsorption. Excitation of totally symmetric vibrational modes then leads to substantial interfacial dynamical charge transfer, which is convincingly reproduced in the calculated IR spectra.
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Affiliation(s)
- Ralf Tonner
- Fachbereich Chemie, Philipps-Universität Marburg, 35032 Marburg, Germany. and Wissenschaftliches Zentrum für Materialwissenschaften (WZMW), Philipps-Universität Marburg, 35032 Marburg, Germany
| | - Phil Rosenow
- Fachbereich Chemie, Philipps-Universität Marburg, 35032 Marburg, Germany.
| | - Peter Jakob
- Wissenschaftliches Zentrum für Materialwissenschaften (WZMW), Philipps-Universität Marburg, 35032 Marburg, Germany and Fachbereich Physik, Philipps-Universität Marburg, 35032 Marburg, Germany.
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12
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Bogner L, Yang Z, Corso M, Fitzner R, Bäuerle P, Franke KJ, Pascual JI, Tegeder P. Electronic structure and excited state dynamics in a dicyanovinyl-substituted oligothiophene on Au(111). Phys Chem Chem Phys 2015; 17:27118-26. [PMID: 26414934 DOI: 10.1039/c5cp04084a] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Dicyanovinyl (DCV)-substituted oligothiophenes are promising donor materials in vacuum-processed small-molecule organic solar cells. Here, we studied the structural and the electronic properties of DCV-dimethyl-pentathiophene (DCV5T-Me2) adsorbed on Au(111) from submonolayer to multilayer coverages. Using a multi-technique experimental approach (low-temperature scanning tunneling microscopy/spectroscopy (STM/STS), atomic force microscopy (AFM), and two-photon photoemission (2PPE) spectroscopy), we determined the energetic position of several affinity levels as well as ionization potentials originating from the lowest unoccupied molecular orbitals (LUMO) and the highest occupied molecular orbitals (HOMO), evidencing a transport gap of 1.4 eV. Proof of an excitonic state was found to be a spectroscopic feature located at 0.6 eV below the LUMO affinity level. With increasing coverage photoemission from excitonic states gains importance. We were able to track the dynamics of several electronically excited states of multilayers by means of femtosecond time-resolved 2PPE. We resolved an intriguing relaxation dynamics involving four processes, ranging from sub-picosecond (ps) to several hundred ps time spans. These show a tendency to increase with increasing coverage. The present study provides important parameters such as energetic positions of transport levels as well as lifetimes of electronically excited states, which are essential for designing organic-molecule-based optoelectronic devices.
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Affiliation(s)
- Lea Bogner
- Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, D-14195 Berlin, Germany
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Tognolini S, Ponzoni S, Sedona F, Sambi M, Pagliara S. Role of the Substrate Orientation in the Photoinduced Electron Dynamics at the Porphyrin/Ag Interface. J Phys Chem Lett 2015; 6:3632-3638. [PMID: 26722734 DOI: 10.1021/acs.jpclett.5b01528] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Photochemically activated reactions, despite being a powerful tool to covalently stabilize self-organized molecular structures on metallic surfaces, have struggled to take off due to several not yet well understood light-driven processes that can affect the final result. A thorough understanding of the photoinduced charge transfer mechanisms at the organic/metal interface would pave the way to controlling these processes and to developing on-surface photochemistry. Here, by time-resolved two-photon photoemission measurements, we track the relaxation processes of the first two excited molecular states at the interface between porphyrin, the essential chromophore in chlorophyll, and two different orientations of the silver surface. Due to the energy alignment of the porphyrin first excited state with the unoccupied sp-bands, an indirect charge transfer path, from the substrate to the molecule, opens in porphyrin/Ag(100) 250 fs after the laser pump excitation. The same time-resolved measurements carried out on porphyrin/Ag(111) show that in the latter case such an indirect path is not viable.
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Affiliation(s)
- Silvia Tognolini
- I-LAMP and Dipartimento di Matematica e Fisica, Università Cattolica , 25121 Brescia, Italy
| | - Stefano Ponzoni
- I-LAMP and Dipartimento di Matematica e Fisica, Università Cattolica , 25121 Brescia, Italy
| | - Francesco Sedona
- Dipartimento di Scienze Chimiche, Università di Padova and Consorzio INSTM , Via Marzolo 1, 35131 Padova, Italy
| | - Mauro Sambi
- Dipartimento di Scienze Chimiche, Università di Padova and Consorzio INSTM , Via Marzolo 1, 35131 Padova, Italy
| | - Stefania Pagliara
- I-LAMP and Dipartimento di Matematica e Fisica, Università Cattolica , 25121 Brescia, Italy
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Zhao J, Feng M, Dougherty DB, Sun H, Petek H. Molecular electronic level alignment at weakly coupled organic film/metal interfaces. ACS NANO 2014; 8:10988-10997. [PMID: 25303040 DOI: 10.1021/nn5049969] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Electronic level alignment at interfaces of molecular materials with inorganic semiconductors and metals controls many interfacial phenomena. How the intrinsic properties of the interacting systems define the electronic structure of their interface remains one of the most important problems in molecular electronics and nanotechnology that can be solved through a combination of surface science experimental techniques and theoretical modeling. In this article, we address this fundamental problem through experimental and computational studies of molecular electronic level alignment of thin films of C(6)F(6) on noble metal surfaces. The unoccupied electronic structure of C(6)F(6) is characterized with single molecule resolution using low-temperature scanning tunneling microscopy-based constant-current distance-voltage spectroscopy. The experiments are performed on several noble metal surfaces with different work functions and distinct surface-normal projected band structures. In parallel, the electronic structures of the quantum wells (QWs) formed by the lowest unoccupied molecular orbital state of the C(6)F(6) monolayer and multilayer films and their alignment with respect to the vacuum level of the metallic substrates are calculated by solving the Schrödinger equation for a semiempirical one-dimensional (1D) potential of the combined system using input from density functional theory. Our analysis shows that the level alignment for C(6)F(6) molecules bound through weak van der Waals interactions to noble metal surfaces is primarily defined by the image potential of metal, the electron affinity of the molecule, and the molecule surface distance. We expect the same factors to determine the interfacial electronic structure for a broad range of molecule/metal interfaces.
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Affiliation(s)
- Jin Zhao
- Department of Physics and ICQD/Hefei National Laboratory for Physical Sciences at Microscale, and §Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China , Hefei, Anhui 230026, P. R. China
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15
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Caplins BW, Suich DE, Shearer AJ, Harris CB. Metal/Phthalocyanine Hybrid Interface States on Ag(111). J Phys Chem Lett 2014; 5:1679-1684. [PMID: 26270366 DOI: 10.1021/jz500571z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A phthalocyanine/Ag(111) interface state is observed for the first time using time- and angle-resolved two-photon photoemission. For monolayer films of metal-free (H2Pc) and iron phthalocyanine (FePc) on Ag(111), the state exists 0.23 ± 0.03 and 0.31 ± 0.03 eV above the Fermi level, respectively. Angle-resolved spectra show the state to be highly dispersive with an effective mass of 0.50 ± 0.15 me for H2Pc and 0.67 ± 0.14 me for FePc. Density functional theory calculations on the H2Pc/Ag(111) surface allow us to characterize this state as being a hybrid state resulting from the interaction between the unoccupied molecular states of the phthalocyanine ligand and the Shockley surface state present on the bare Ag(111) surface. This work, when taken together with the extensive literature on the 3,4,9,10-perylene tetracarboxylic dianhydride/Ag interface state, provides compelling evidence that the hybridization of metal surface states with molecular electronic states is a general phenomenon.
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Affiliation(s)
- Benjamin W Caplins
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - David E Suich
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Alex J Shearer
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Charles B Harris
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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