1
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Wallauer R, Raths M, Stallberg K, Münster L, Brandstetter D, Yang X, Güdde J, Puschnig P, Soubatch S, Kumpf C, Bocquet FC, Tautz FS, Höfer U. Tracing orbital images on ultrafast time scales. Science 2021; 371:1056-1059. [PMID: 33602865 DOI: 10.1126/science.abf3286] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Accepted: 02/01/2021] [Indexed: 11/02/2022]
Abstract
Frontier orbitals determine fundamental molecular properties such as chemical reactivities. Although electron distributions of occupied orbitals can be imaged in momentum space by photoemission tomography, it has so far been impossible to follow the momentum-space dynamics of a molecular orbital in time, for example, through an excitation or a chemical reaction. Here, we combined time-resolved photoemission using high laser harmonics and a momentum microscope to establish a tomographic, femtosecond pump-probe experiment of unoccupied molecular orbitals. We measured the full momentum-space distribution of transiently excited electrons, connecting their excited-state dynamics to real-space excitation pathways. Because in molecules this distribution is closely linked to orbital shapes, our experiment may, in the future, offer the possibility of observing ultrafast electron motion in time and space.
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Affiliation(s)
- R Wallauer
- Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität Marburg, Renthof 5, 35032 Marburg, Germany
| | - M Raths
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany.,Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany.,Experimentalphysik IV A, RWTH Aachen University, Otto-Blumenthal-Straße, 52074 Aachen, Germany
| | - K Stallberg
- Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität Marburg, Renthof 5, 35032 Marburg, Germany
| | - L Münster
- Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität Marburg, Renthof 5, 35032 Marburg, Germany
| | - D Brandstetter
- Institute of Physics, University of Graz, NAWI Graz, 8010 Graz, Austria
| | - X Yang
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany.,Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany.,Experimentalphysik IV A, RWTH Aachen University, Otto-Blumenthal-Straße, 52074 Aachen, Germany
| | - J Güdde
- Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität Marburg, Renthof 5, 35032 Marburg, Germany
| | - P Puschnig
- Institute of Physics, University of Graz, NAWI Graz, 8010 Graz, Austria
| | - S Soubatch
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany.,Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - C Kumpf
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany.,Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany.,Experimentalphysik IV A, RWTH Aachen University, Otto-Blumenthal-Straße, 52074 Aachen, Germany
| | - F C Bocquet
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany.,Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - F S Tautz
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany. .,Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany.,Experimentalphysik IV A, RWTH Aachen University, Otto-Blumenthal-Straße, 52074 Aachen, Germany
| | - U Höfer
- Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität Marburg, Renthof 5, 35032 Marburg, Germany.
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2
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Bocquet FC, Lin YR, Franke M, Samiseresht N, Parhizkar S, Soubatch S, Lee TL, Kumpf C, Tautz FS. Surfactant-Mediated Epitaxial Growth of Single-Layer Graphene in an Unconventional Orientation on SiC. Phys Rev Lett 2020; 125:106102. [PMID: 32955317 DOI: 10.1103/physrevlett.125.106102] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Revised: 01/08/2020] [Accepted: 07/08/2020] [Indexed: 06/11/2023]
Abstract
We report the use of a surfactant molecule during the epitaxy of graphene on SiC(0001) that leads to the growth in an unconventional orientation, namely R0° rotation with respect to the SiC lattice. It yields a very high-quality single-layer graphene with a uniform orientation with respect to the substrate, on the wafer scale. We find an increased quality and homogeneity compared to the approach based on the use of a preoriented template to induce the unconventional orientation. Using spot profile analysis low-energy electron diffraction, angle-resolved photoelectron spectroscopy, and the normal incidence x-ray standing wave technique, we assess the crystalline quality and coverage of the graphene layer. Combined with the presence of a covalently bound graphene layer in the conventional orientation underneath, our surfactant-mediated growth offers an ideal platform to prepare epitaxial twisted bilayer graphene via intercalation.
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Affiliation(s)
- F C Bocquet
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - Y-R Lin
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
- Experimentalphysik IV A, RWTH Aachen University, Otto-Blumenthal-Straße, 52074 Aachen, Germany
| | - M Franke
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
- Experimentalphysik IV A, RWTH Aachen University, Otto-Blumenthal-Straße, 52074 Aachen, Germany
| | - N Samiseresht
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
- Experimentalphysik IV A, RWTH Aachen University, Otto-Blumenthal-Straße, 52074 Aachen, Germany
| | - S Parhizkar
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - S Soubatch
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - T-L Lee
- Diamond Light Source, Ltd., Didcot OX110DE, Oxfordshire, United Kingdom
| | - C Kumpf
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
- Experimentalphysik IV A, RWTH Aachen University, Otto-Blumenthal-Straße, 52074 Aachen, Germany
| | - F S Tautz
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
- Experimentalphysik IV A, RWTH Aachen University, Otto-Blumenthal-Straße, 52074 Aachen, Germany
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3
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Puschnig P, Boese AD, Willenbockel M, Meyer M, Lüftner D, Reinisch EM, Ules T, Koller G, Soubatch S, Ramsey MG, Tautz FS. Energy Ordering of Molecular Orbitals. J Phys Chem Lett 2017; 8:208-213. [PMID: 27935313 PMCID: PMC5220489 DOI: 10.1021/acs.jpclett.6b02517] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 12/09/2016] [Indexed: 05/17/2023]
Abstract
Orbitals are invaluable in providing a model of bonding in molecules or between molecules and surfaces. Most present-day methods in computational chemistry begin by calculating the molecular orbitals of the system. To what extent have these mathematical objects analogues in the real world? To shed light on this intriguing question, we employ a photoemission tomography study on monolayers of 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) grown on three Ag surfaces. The characteristic photoelectron angular distribution enables us to assign individual molecular orbitals to the emission features. When comparing the resulting energy positions to density functional calculations, we observe deviations in the energy ordering. By performing complete active space calculations (CASSCF), we can explain the experimentally observed orbital ordering, suggesting the importance of static electron correlation beyond a (semi)local approximation. On the other hand, our results also show reality and robustness of the orbital concept, thereby making molecular orbitals accessible to experimental observations.
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Affiliation(s)
- P. Puschnig
- Institute
of Physics, University of Graz, NAWI-Graz, Universitätsplatz
5, 8010 Graz, Austria
- E-mail:
| | - A. D. Boese
- Institute
of Chemistry, University of Graz, NAWI Graz, Heinrichstraße 28/IV, 8010 Graz, Austria
| | - M. Willenbockel
- Peter
Grünberg Institut (PGI-3), Forschungszentrum
Jülich, 52425 Jülich, Germany
- Jülich
Aachen
Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - M. Meyer
- Peter
Grünberg Institut (PGI-3), Forschungszentrum
Jülich, 52425 Jülich, Germany
- Jülich
Aachen
Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - D. Lüftner
- Institute
of Physics, University of Graz, NAWI-Graz, Universitätsplatz
5, 8010 Graz, Austria
| | - E. M. Reinisch
- Institute
of Physics, University of Graz, NAWI-Graz, Universitätsplatz
5, 8010 Graz, Austria
| | - T. Ules
- Institute
of Physics, University of Graz, NAWI-Graz, Universitätsplatz
5, 8010 Graz, Austria
| | - G. Koller
- Institute
of Physics, University of Graz, NAWI-Graz, Universitätsplatz
5, 8010 Graz, Austria
| | - S. Soubatch
- Peter
Grünberg Institut (PGI-3), Forschungszentrum
Jülich, 52425 Jülich, Germany
- Jülich
Aachen
Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - M. G. Ramsey
- Institute
of Physics, University of Graz, NAWI-Graz, Universitätsplatz
5, 8010 Graz, Austria
| | - F. S. Tautz
- 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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4
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Sforzini J, Hapala P, Franke M, van Straaten G, Stöhr A, Link S, Soubatch S, Jelínek P, Lee TL, Starke U, Švec M, Bocquet FC, Tautz FS. Structural and Electronic Properties of Nitrogen-Doped Graphene. Phys Rev Lett 2016; 116:126805. [PMID: 27058093 DOI: 10.1103/physrevlett.116.126805] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Indexed: 06/05/2023]
Abstract
We investigate the structural and electronic properties of nitrogen-doped epitaxial monolayer graphene and quasifreestanding monolayer graphene on 6H-SiC(0001) by the normal incidence x-ray standing wave technique and by angle-resolved photoelectron spectroscopy supported by density functional theory simulations. With the location of various nitrogen species uniquely identified, we observe that for the same doping procedure, the graphene support, consisting of substrate and interface, strongly influences the structural as well as the electronic properties of the resulting doped graphene layer. Compared to epitaxial graphene, quasifreestanding graphene is found to contain fewer nitrogen dopants. However, this lack of dopants is compensated by the proximity of nitrogen atoms at the interface that yield a similar number of charge carriers in graphene.
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Affiliation(s)
- J Sforzini
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - P Hapala
- Institute of Physics of the Czech Academy of Sciences, Cukrovarnická 10, 16200 Prague, Czech Republic
| | - M Franke
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - G van Straaten
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - A Stöhr
- Max Planck Institute for Solid State Research, Heisenbergstraße, 70569 Stuttgart, Germany
| | - S Link
- Max Planck Institute for Solid State Research, Heisenbergstraße, 70569 Stuttgart, Germany
| | - S Soubatch
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - P Jelínek
- Institute of Physics of the Czech Academy of Sciences, Cukrovarnická 10, 16200 Prague, Czech Republic
| | - T-L Lee
- Diamond Light Source Ltd, Didcot OX110DE, Oxfordshire, United Kingdom
| | - U Starke
- Max Planck Institute for Solid State Research, Heisenbergstraße, 70569 Stuttgart, Germany
| | - M Švec
- Institute of Physics of the Czech Academy of Sciences, Cukrovarnická 10, 16200 Prague, Czech Republic
| | - F C Bocquet
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - F S Tautz
- 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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Sforzini J, Nemec L, Denig T, Stadtmüller B, Lee TL, Kumpf C, Soubatch S, Starke U, Rinke P, Blum V, Bocquet FC, Tautz FS. Approaching truly freestanding graphene: the structure of hydrogen-intercalated graphene on 6H-SiC(0001). Phys Rev Lett 2015; 114:106804. [PMID: 25815955 DOI: 10.1103/physrevlett.114.106804] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Indexed: 06/04/2023]
Abstract
We measure the adsorption height of hydrogen-intercalated quasifreestanding monolayer graphene on the (0001) face of 6H silicon carbide by the normal incidence x-ray standing wave technique. A density functional calculation for the full (6√3×6√3)-R30° unit cell, based on a van der Waals corrected exchange correlation functional, finds a purely physisorptive adsorption height in excellent agreement with experiments, a very low buckling of the graphene layer, a very homogeneous electron density at the interface, and the lowest known adsorption energy per atom for graphene on any substrate. A structural comparison to other graphenes suggests that hydrogen-intercalated graphene on 6H-SiC(0001) approaches ideal graphene.
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Affiliation(s)
- J Sforzini
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - L Nemec
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, 14195 Berlin, Germany
| | - T Denig
- Max Planck Institute for Solid State Research, Heisenbergstraße, 70569 Stuttgart, Germany
| | - B Stadtmüller
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - T-L Lee
- Diamond Light Source Ltd, Didcot, OX110DE Oxfordshire, United Kingdom
| | - C Kumpf
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - S Soubatch
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - U Starke
- Max Planck Institute for Solid State Research, Heisenbergstraße, 70569 Stuttgart, Germany
| | - P Rinke
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, 14195 Berlin, Germany
- COMP/Department of Applied Physics, Aalto University, P.O. Box 11100, Aalto FI-00076, Finland
| | - V Blum
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, 14195 Berlin, Germany
- Department of Mechanical Engineering and Material Science, Duke University, Durham, North Carolina 27708, USA
| | - F C Bocquet
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - F S Tautz
- 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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6
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Willenbockel M, Lüftner D, Stadtmüller B, Koller G, Kumpf C, Soubatch S, Puschnig P, Ramsey MG, Tautz FS. The interplay between interface structure, energy level alignment and chemical bonding strength at organic-metal interfaces. Phys Chem Chem Phys 2014; 17:1530-48. [PMID: 25475998 DOI: 10.1039/c4cp04595e] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
What do energy level alignments at metal-organic interfaces reveal about the metal-molecule bonding strength? Is it permissible to take vertical adsorption heights as indicators of bonding strengths? In this paper we analyse 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) on the three canonical low index Ag surfaces to provide exemplary answers to these questions. Specifically, we employ angular resolved photoemission spectroscopy for a systematic study of the energy level alignments of the two uppermost frontier states in ordered monolayer phases of PTCDA. Data are analysed using the orbital tomography approach. This allows the unambiguous identification of the orbital character of these states, and also the discrimination between inequivalent species. Combining this experimental information with DFT calculations and the generic Newns-Anderson chemisorption model, we analyse the alignments of highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) with respect to the vacuum levels of bare and molecule-covered surfaces. This reveals clear differences between the two frontier states. In particular, on all surfaces the LUMO is subject to considerable bond stabilization through the interaction between the molecular π-electron system and the metal, as a consequence of which it also becomes occupied. Moreover, we observe a larger bond stabilization for the more open surfaces. Most importantly, our analysis shows that both the orbital binding energies of the LUMO and the overall adsorption heights of the molecule are linked to the strength of the chemical interaction between the molecular π-electron system and the metal, in the sense that stronger bonding leads to shorter adsorption heights and larger orbital binding energies.
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Affiliation(s)
- M Willenbockel
- Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany
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7
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Wagner C, Fournier N, Tautz FS, Temirov R. Measurement of the binding energies of the organic-metal perylene-teracarboxylic-dianhydride/Au111 bonds by molecular manipulation using an atomic force microscope. Phys Rev Lett 2012; 109:076102. [PMID: 23006386 DOI: 10.1103/physrevlett.109.076102] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Indexed: 05/22/2023]
Abstract
Based on single molecule manipulation experiments in a combined scanning tunneling microscope/frequency modulated atomic force microscope, we quantify the individual binding energy contributions to an organic-metal bond experimentally. The method allows the determination of contributions from, e.g., local chemical bonds, metal-molecule hybridization, and van der Waals interactions, as well as the total adsorption energy.
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Affiliation(s)
- C Wagner
- Peter Grünberg Institut, Forschungszentrum Jülich, Germany.
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8
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Weiss C, Wagner C, Kleimann C, Rohlfing M, Tautz FS, Temirov R. Imaging Pauli repulsion in scanning tunneling microscopy. Phys Rev Lett 2010; 105:086103. [PMID: 20868116 DOI: 10.1103/physrevlett.105.086103] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2009] [Revised: 02/12/2010] [Indexed: 05/12/2023]
Abstract
A scanning tunneling microscope (STM) has been equipped with a nanoscale force sensor and signal transducer composed of a single D2 molecule that is confined in the STM junction. The uncalibrated sensor is used to obtain ultrahigh geometric image resolution of a complex organic molecule adsorbed on a noble metal surface. By means of conductance-distance spectroscopy and corresponding density functional calculations the mechanism of the sensor and transducer is identified. It probes the short-range Pauli repulsion and converts this signal into variations of the junction conductance.
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Affiliation(s)
- C Weiss
- Institut für Bio- und Nanosysteme 3, Forschungszentrum Jülich, 52425 Jülich, Germany
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9
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Mercurio G, McNellis ER, Martin I, Hagen S, Leyssner F, Soubatch S, Meyer J, Wolf M, Tegeder P, Tautz FS, Reuter K. Structure and energetics of azobenzene on Ag(111): benchmarking semiempirical dispersion correction approaches. Phys Rev Lett 2010; 104:036102. [PMID: 20366661 DOI: 10.1103/physrevlett.104.036102] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2009] [Indexed: 05/24/2023]
Abstract
We employ normal-incidence x-ray standing wave and temperature programed desorption spectroscopy to derive the adsorption geometry and energetics of the prototypical molecular switch azobenzene at Ag(111). This allows us to assess the accuracy of semiempirical correction schemes as a computationally efficient means to overcome the deficiency of semilocal density-functional theory with respect to long-range van der Waals (vdW) interactions. The obtained agreement underscores the significant improvement provided by the account of vdW interactions, with remaining differences mainly attributed to the neglect of electronic screening at the metallic surface.
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Affiliation(s)
- G Mercurio
- Institut für Bio- und Nanosysteme 3, Forschungszentrum Jülich, 52425 Jülich, Germany
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10
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Abstract
Systematic local spectroscopy of the affinity levels, by means of a scanning tunneling microscope, in highly ordered molecular semiconductor films of tetracene reveals strong energy level shifts by up to approximately 1.0 eV from molecule to molecule. This final state effect can be traced back to the site specificity of the polarization energy in organic materials with complex unit cells, caused by a combination of different molecular environments, the intrinsically anisotropic molecular polarizability, and the influence of the substrate.
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Affiliation(s)
- S Soubatch
- JARA-Fundamentals of Future Information Technology and Institut für Bio- und Nanosysteme 3, Forschungszentrum Jülich, 52425, Germany
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11
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Kilian L, Hauschild A, Temirov R, Soubatch S, Schöll A, Bendounan A, Reinert F, Lee TL, Tautz FS, Sokolowski M, Umbach E. Role of intermolecular interactions on the electronic and geometric structure of a large pi-conjugated molecule adsorbed on a metal surface. Phys Rev Lett 2008; 100:136103. [PMID: 18517971 DOI: 10.1103/physrevlett.100.136103] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2007] [Indexed: 05/03/2023]
Abstract
The organic semiconductor molecule 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) exhibits two adsorption states on the Ag(111) surface: one in a metastable disordered phase, prepared at low temperatures, the other in the long-range ordered monolayer phase obtained at room temperature. Notably, the two states differ substantial in their vertical bonding distances, intramolecular distortions, and electronic structures. The difference is explained by intermolecular interactions, which are particularly relevant for the long-range ordered phase, and which hence require attention.
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Affiliation(s)
- L Kilian
- Universität Würzburg, Experimentelle Physik II, Am Hubland, 97074 Würzburg, Germany
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12
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Abstract
Conductance measurements of a molecular wire, contacted between an epitaxial molecule-metal bond and the tip of a scanning tunnelling microscope, are reported. Controlled retraction of the tip gradually de-hybridizes the molecule from the metal substrate. This tunes the wire into the Kondo regime in which the renormalized molecular transport orbital serves as a spin impurity at half-filling and the Kondo resonance opens up an additional transport channel. Numerical renormalization group simulations suggest this type of behaviour to be generic for a common class of metal-molecule bonds. The results demonstrate a new approach to single-molecule experiments with atomic-scale contact control and prepare the way for the ab initio simulation of many-body transport through single-molecule junctions.
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Affiliation(s)
- R Temirov
- Jacobs University Bremen, School of Engineering and Science, PO Box 750561, D-28725 Bremen, Germany. Institut für Bio- und Nanosysteme 3, JARA, Forschungszentrum Jülich, 52425 Jülich, Germany
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Schreiber F, Gerlach A, Koch N, Zojer E, Sokolowski M, Tautz FS, Rohlfing M, Umbach E. Comment on "Electron core-hole interaction and its induced ionic structural relaxation in molecular systems under x-ray irradiation". Phys Rev Lett 2007; 99:059601-059602. [PMID: 17930804 DOI: 10.1103/physrevlett.99.059601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2007] [Indexed: 05/25/2023]
Affiliation(s)
- F Schreiber
- Universität Tübingen Auf der Morgenstelle 10, 72076 Tübingen, Germany
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14
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Weinhold M, Soubatch S, Temirov R, Rohlfing M, Jastorff B, Tautz FS, Doose C. Structure and Bonding of the Multifunctional Amino Acid l-DOPA on Au(110). J Phys Chem B 2006; 110:23756-69. [PMID: 17125337 DOI: 10.1021/jp064956t] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In investigations of the proteins which are responsible for the surface adhesion of the blue mussel Mytilus edulis, an unusually frequent appearance of the otherwise rare amino acid 3-(3,4-dihydroxyphenyl)-L-alanine (L-DOPA) has been observed. This amino acid is thought to play a major role in the mechanism of mussel adhesion. Here we report a detailed structural and spectroscopic investigation of the interface between L-DOPA and a single-crystalline Au(110) model surface, with the aim of understanding fundamentals about the surface bonding of this amino acid and its role in mussel adhesion. Molecular layers are deposited by organic molecular beam deposition (OMBD) in an ultrahigh-vacuum environment. The following experimental techniques have been applied: ex situ Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), high-resolution electron energy loss spectroscopy (HREELS), and scanning tunneling microscopy (STM). Vibrational spectra of isolated L-DOPA molecules and the zwitterionic bulk have been calculated using density functional theory (DFT). The predicted modes are assigned to observed spectra, allowing conclusions regarding the molecule-substrate and molecule-molecule interactions at the L-DOPA/Au(110) interface. We find that zwitterionic L-DOPA forms a monochiral, one-domain commensurate monolayer on Au(110), with the catechol rings on top of [110] gold rows, oriented parallel to the surface. The (2 x 1)-Au(110) surface reconstruction is not lifted. The carboxylate group is found in a bidentate or bridging configuration, the amino group is tilted out of the surface plane, and the hydroxyl groups do not dehydrogenate on Au(110). Similar to the case for the bulk, molecules form dimers on Au(110). However, the number of hydrogen bridge bonds between L-DOPA molecules is reduced as compared to the bulk. Thicker layers which are deposited onto the commensurate interface do not order in the bulk structure. In conclusion, our study shows that the aromatic ring system of L-DOPA functions as a surface anchor. Since it is also known that the hydroxyl groups support cross-link reactions between L-DOPA residues in the mussel glue protein, we can conclude that the catechol ring supports surface adhesion of mussel proteins via two independent functions.
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Affiliation(s)
- M Weinhold
- School of Engineering and Science, International University Bremen, Campus Ring 8, 28759 Bremen, Germany
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15
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Temirov R, Soubatch S, Luican A, Tautz FS. Free-electron-like dispersion in an organic monolayer film on a metal substrate. Nature 2006; 444:350-3. [PMID: 17108961 DOI: 10.1038/nature05270] [Citation(s) in RCA: 234] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2006] [Accepted: 09/18/2006] [Indexed: 11/08/2022]
Abstract
Thin films of molecular organic semiconductors are attracting much interest for use in electronic and optoelectronic applications. The electronic properties of these materials and their interfaces are therefore worth investigating intensively, particularly the degree of electron delocalization that can be achieved. If the delocalization is appreciable, it should be accompanied by an observable electronic band dispersion. But so far only limited experimental data on the intermolecular dispersion of electronic states in molecular materials is available, and the mechanism(s) of electron delocalization in molecular materials are also not well understood. Here we report scanning tunnelling spectroscopy observations of an organic monolayer film on a silver substrate, revealing a completely delocalized two-dimensional band state that is characterized by a metal-like parabolic dispersion with an effective mass of m* = 0.47m(e), where m(e) is the bare electron mass. This dispersion is far stronger than expected for the organic film alone, and arises as a result of strong substrate-mediated coupling between the molecules within the monolayer.
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Affiliation(s)
- R Temirov
- School of Engineering and Science, International University Bremen, P. O. Box 750561, 28725 Bremen, Germany
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Hauschild A, Karki K, Cowie BCC, Rohlfing M, Tautz FS, Sokolowski M. Molecular distortions and chemical bonding of a large pi-conjugated molecule on a metal surface. Phys Rev Lett 2005; 94:036106. [PMID: 15698289 DOI: 10.1103/physrevlett.94.036106] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2004] [Indexed: 05/24/2023]
Abstract
Normal incidence x-ray standing wave experiments and density functional theory reveal that 3,4,9,10-perylene-tetracarboxylic-dianhydride chemisorbs on Ag(111) in a nonplanar but vertically distorted configuration. The carboxylic O atoms are 0.18 +/- 0.03 angstroms closer to the surface than the perylene core. The distortion is related to weak, local bonds between carboxylic O atoms and the Ag surface which are coupled--through charge transfer into the former lowest unoccupied molecular orbital--to the primary, extended chemisorption bond via the perylene skeleton.
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Affiliation(s)
- A Hauschild
- Institut für Physikalische und Theoretische Chemie der Universität Bonn, Wegelerstrasse 12, 53115 Bonn, Germany
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17
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Eremtchenko M, Schaefer JA, Tautz FS. Understanding and tuning the epitaxy of large aromatic adsorbates by molecular design. Nature 2003; 425:602-5. [PMID: 14534582 DOI: 10.1038/nature01901] [Citation(s) in RCA: 227] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2003] [Accepted: 07/10/2003] [Indexed: 11/09/2022]
Abstract
If the rich functionality of organic molecules is to be exploited in devices such as light-emitting diodes or field-effect transistors, interface properties of organic materials with various (metallic and insulating) substrates must be tailored carefully. In many cases, this calls for well-ordered interfaces. Organic epitaxy-that is, the growth of molecular films with a commensurate structural relationship to their crystalline substrates--relies on successful recognition of preferred epitaxial sites. For some large pi-conjugated molecules ('molecular platelets') this works surprisingly well, even if the substrate exhibits no template structure into which the molecules can lock. Here we present an explanation for site recognition in non-templated organic epitaxy, and thus resolve a long-standing puzzle. We propose that this form of site recognition relies on the existence of a local molecular reaction centre in the extended pi-electron system of the molecule. Its activity can be controlled by appropriate side groups and--in a certain regime--may also be probed by molecularly sensitized scanning tunnelling microscopy. Our results open the possibility of engineering epitaxial interfaces, as well as other interfacial nanostructures for which specific site recognition is essential.
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Affiliation(s)
- M Eremtchenko
- Institut für Physik und Zentrum für Mikro- und Nanotechnologien, Technische Universität Ilmenau, PO Box 100565, 98684 Ilmenau, Germany
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