1
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Rothe K, Néel N, Kröger J. Unveiling the nature of atomic defects in graphene on a metal surface. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2024; 15:416-425. [PMID: 38655541 PMCID: PMC11035987 DOI: 10.3762/bjnano.15.37] [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: 12/31/2023] [Accepted: 03/18/2024] [Indexed: 04/26/2024]
Abstract
Low-energy argon ion bombardment of graphene on Ir(111) induces atomic-scale defects at the surface. Using a scanning tunneling microscope, the two smallest defects appear as a depression without discernible interior structure suggesting the presence of vacancy sites in the graphene lattice. With an atomic force microscope, however, only one kind can be identified as a vacancy defect with four missing carbon atoms, while the other kind reveals an intact graphene sheet. Spatially resolved spectroscopy of the differential conductance and the measurement of total-force variations as a function of the lateral and vertical probe-defect distance corroborate the different character of the defects. The tendency of the vacancy defect to form a chemical bond with the microscope probe is reflected by the strongest attraction at the vacancy center as well as by hysteresis effects in force traces recorded for tip approach to and retraction from the Pauli repulsion range of vertical distances.
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Affiliation(s)
- Karl Rothe
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
| | - Nicolas Néel
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
| | - Jörg Kröger
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
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2
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Wu X, Néel N, Brandbyge M, Kröger J. Enhancement of Graphene Phonon Excitation by a Chemically Engineered Molecular Resonance. PHYSICAL REVIEW LETTERS 2023; 130:116201. [PMID: 37001107 DOI: 10.1103/physrevlett.130.116201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Accepted: 02/21/2023] [Indexed: 06/19/2023]
Abstract
The abstraction of pyrrolic hydrogen from a single phthalocyanine on graphene turns the molecule into a sensitive probe for graphene phonons. The inelastic electron transport measured with a scanning tunneling microscope across the molecular adsorbate and graphene becomes strongly enhanced for a graphene out-of-plane acoustic phonon mode. Supporting density functional and transport calculations elucidate the underlying physical mechanism. A molecular orbital resonance close to the Fermi energy controls the inelastic current while specific phonon modes of graphene are magnified due to their coupling to symmetry-equivalent vibrational quanta of the molecule.
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Affiliation(s)
- Xiaocui Wu
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
| | - Nicolas Néel
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
| | - Mads Brandbyge
- Center of Nanostructured Graphene, Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - Jörg Kröger
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
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3
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Simon S, Voloshina E, Tesch J, Förschner F, Enenkel V, Herbig C, Knispel T, Tries A, Kröger J, Dedkov Y, Fonin M. Layer-by-Layer Decoupling of Twisted Graphene Sheets Epitaxially Grown on a Metal Substrate. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2018; 14:e1703701. [PMID: 29450969 DOI: 10.1002/smll.201703701] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Revised: 12/23/2017] [Indexed: 06/08/2023]
Abstract
The electronic properties of graphene can be efficiently altered upon interaction with the underlying substrate resulting in a dramatic change of charge carrier behavior. Here, the evolution of the local electronic properties of epitaxial graphene on a metal upon the controlled formation of multilayers, which are produced by intercalation of atomic carbon in graphene/Ir(111), is investigated. Using scanning tunneling microscopy and Landau-level spectroscopy, it is shown that for a monolayer and bilayers with small-angle rotations, Landau levels are fully suppressed, indicating that the metal-graphene interaction is largely confined to the first graphene layer. Bilayers with large twist angles as well as twisted trilayers demonstrate a sequence of pronounced Landau levels characteristic for a free-standing graphene monolayer pointing toward an effective decoupling of the top layer from the metal substrate. These findings give evidence for the controlled preparation of epitaxial graphene multilayers with a different degree of decoupling, which represent an ideal platform for future electronic and spintronic applications.
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Affiliation(s)
- Sabina Simon
- Department of Physics, University of Konstanz, 78457, Konstanz, Germany
| | - Elena Voloshina
- Physics Department, Shanghai University, Shanghai, 200444, China
| | - Julia Tesch
- Department of Physics, University of Konstanz, 78457, Konstanz, Germany
| | - Felix Förschner
- Department of Physics, University of Konstanz, 78457, Konstanz, Germany
| | - Vivien Enenkel
- Department of Physics, University of Konstanz, 78457, Konstanz, Germany
| | - Charlotte Herbig
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937, Köln, Germany
- Department of Physics, University of California at Berkeley, Berkeley, CA, 94720, USA
| | - Timo Knispel
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937, Köln, Germany
| | - Alexander Tries
- Institut für Physik, Technische Universität Ilmenau, 98693, Ilmenau, Germany
| | - Jörg Kröger
- Institut für Physik, Technische Universität Ilmenau, 98693, Ilmenau, Germany
| | - Yuriy Dedkov
- Physics Department, Shanghai University, Shanghai, 200444, China
| | - Mikhail Fonin
- Department of Physics, University of Konstanz, 78457, Konstanz, Germany
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4
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Dombrowski D, Jolie W, Petrović M, Runte S, Craes F, Klinkhammer J, Kralj M, Lazić P, Sela E, Busse C. Energy-Dependent Chirality Effects in Quasifree-Standing Graphene. PHYSICAL REVIEW LETTERS 2017; 118:116401. [PMID: 28368636 DOI: 10.1103/physrevlett.118.116401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Indexed: 06/07/2023]
Abstract
We present direct experimental evidence of broken chirality in graphene by analyzing electron scattering processes at energies ranging from the linear (Dirac-like) to the strongly trigonally warped region. Furthermore, we are able to measure the energy of the van Hove singularity at the M point of the conduction band. Our data show a very good agreement with theoretical calculations for free-standing graphene. We identify a new intravalley scattering channel activated in case of a strongly trigonally warped constant energy contour, which is not suppressed by chirality. Finally, we compare our experimental findings with T-matrix simulations with and without the presence of a pseudomagnetic field and suggest that higher order electron hopping effects are a key factor in breaking the chirality near to the van Hove singularity.
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Affiliation(s)
- Daniela Dombrowski
- Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
| | - Wouter Jolie
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
| | - Marin Petrović
- Center of Excellence for Advanced Materials and Sensing Devices, Institute of Physics, Bijenička 46, 10000 Zagreb, Croatia
| | - Sven Runte
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
| | - Fabian Craes
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
| | - Jürgen Klinkhammer
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
| | - Marko Kralj
- Center of Excellence for Advanced Materials and Sensing Devices, Institute of Physics, Bijenička 46, 10000 Zagreb, Croatia
| | - Predrag Lazić
- Institut Ruđer Bošković, Bijenička 54, 10000 Zagreb, Croatia
| | - Eran Sela
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Haim Levanon St 55, 6997801 Tel Aviv, Israel
| | - Carsten Busse
- Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
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5
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Müller M, Néel N, Crampin S, Kröger J. Lateral Electron Confinement with Open Boundaries: Quantum Well States above Nanocavities at Pb(111). PHYSICAL REVIEW LETTERS 2016; 117:136803. [PMID: 27715132 DOI: 10.1103/physrevlett.117.136803] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Indexed: 06/06/2023]
Abstract
We have studied electron states present at the Pb(111) surface above Ar-filled nanocavities created by ion beam irradiation and annealing. Vertical confinement between the parallel crystal and nanocavity surfaces creates a series of quantum well state subbands. Differential conductance data measured by scanning tunneling spectroscopy contain a characteristic spectroscopic fine structure within the highest occupied subband, revealing additional quantization. Unexpectedly, reflection at the open boundary where the thin Pb film recovers its bulk thickness gives rise to the lateral confinement of electrons.
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Affiliation(s)
- M Müller
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
| | - N Néel
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
| | - S Crampin
- Department of Physics, University of Bath, Bath BA2 7AY, United Kingdom
| | - J Kröger
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
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6
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González-Herrero H, Pou P, Lobo-Checa J, Fernández-Torre D, Craes F, Martínez-Galera AJ, Ugeda MM, Corso M, Ortega JE, Gómez-Rodríguez JM, Pérez R, Brihuega I. Graphene Tunable Transparency to Tunneling Electrons: A Direct Tool To Measure the Local Coupling. ACS NANO 2016; 10:5131-5144. [PMID: 27110642 DOI: 10.1021/acsnano.6b00322] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The local interaction between graphene and a host substrate strongly determines the actual properties of the graphene layer. Here we show that scanning tunneling microscopy (STM) can selectively help to visualize either the graphene layer or the substrate underneath, or even both at the same time, providing a comprehensive picture of this coupling with atomic precision and high energy resolution. We demonstrate this for graphene on Cu(111). Our spectroscopic data show that, in the vicinity of the Fermi level, graphene π bands are well preserved presenting a small n-doping induced by Cu(111) surface state electrons. Such results are corroborated by Angle-Resolved Photoemission Spectra (ARPES) and Density Functional Theory with van der Waals (DFT + vdW) calculations. Graphene tunable transparency also allows the investigation of the interaction between the substrate and foreign species (such as atomic H or C vacancies) on the graphene layer. Our calculations explain graphene tunable transparency in terms of the rather different decay lengths of the graphene Dirac π states and the metal surface state, suggesting that it should apply to a good number of graphene/substrate systems.
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Affiliation(s)
- Héctor González-Herrero
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid , E-28049 Madrid, Spain
- Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid , E-28049 Madrid, Spain
| | - Pablo Pou
- Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid , E-28049 Madrid, Spain
- Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid , E-28049 Madrid, Spain
| | - Jorge Lobo-Checa
- Centro de Física de Materiales (CSIC-UPV-EHU) and Materials Physics Center (MPC) , Manuel Lardizábal 5, E-20018 San Sebastián, Spain
| | - Delia Fernández-Torre
- Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid , E-28049 Madrid, Spain
| | - Fabian Craes
- II. Physikalisches Institut, Universität zu Köln , Zülpicher Straße 77, 50937 Köln, Germany
| | - Antonio J Martínez-Galera
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid , E-28049 Madrid, Spain
- II. Physikalisches Institut, Universität zu Köln , Zülpicher Straße 77, 50937 Köln, Germany
| | - Miguel M Ugeda
- CIC nanoGUNE , 20018 Donostia-San Sebastian, Spain
- Ikerbasque, Basque Foundation for Science , 48013 Bilbao, Spain
| | - Martina Corso
- Centro de Física de Materiales (CSIC-UPV-EHU) and Materials Physics Center (MPC) , Manuel Lardizábal 5, E-20018 San Sebastián, Spain
- Ikerbasque, Basque Foundation for Science , 48013 Bilbao, Spain
| | - J Enrique Ortega
- Centro de Física de Materiales (CSIC-UPV-EHU) and Materials Physics Center (MPC) , Manuel Lardizábal 5, E-20018 San Sebastián, Spain
- Donostia International Physics Center DIPC , E-20018 San Sebastián, Spain
- Departamento de Física Aplicada I, Universidad del País Vasco , E-20018 San Sebastián, Spain
| | - José M Gómez-Rodríguez
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid , E-28049 Madrid, Spain
- Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid , E-28049 Madrid, Spain
| | - Rubén Pérez
- Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid , E-28049 Madrid, Spain
- Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid , E-28049 Madrid, Spain
| | - Iván Brihuega
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid , E-28049 Madrid, Spain
- Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid , E-28049 Madrid, Spain
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7
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Structural and electronic properties of graphene nanoflakes on Au(111) and Ag(111). Sci Rep 2016; 6:23439. [PMID: 27002297 PMCID: PMC4802307 DOI: 10.1038/srep23439] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Accepted: 03/07/2016] [Indexed: 01/07/2023] Open
Abstract
We investigate the electronic properties of graphene nanoflakes on Ag(111) and Au(111) surfaces by means of scanning tunneling microscopy and spectroscopy as well as density functional theory calculations. Quasiparticle interference mapping allows for the clear distinction of substrate-derived contributions in scattering and those originating from graphene nanoflakes. Our analysis shows that the parabolic dispersion of Au(111) and Ag(111) surface states remains unchanged with the band minimum shifted to higher energies for the regions of the metal surface covered by graphene, reflecting a rather weak interaction between graphene and the metal surface. The analysis of graphene-related scattering on single nanoflakes yields a linear dispersion relation E(k), with a slight p-doping for graphene/Au(111) and a larger n-doping for graphene/Ag(111). The obtained experimental data (doping level, band dispersions around EF, and Fermi velocity) are very well reproduced within DFT-D2/D3 approaches, which provide a detailed insight into the site-specific interaction between graphene and the underlying substrate.
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8
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Martínez-Galera AJ, Schröder UA, Huttmann F, Jolie W, Craes F, Busse C, Caciuc V, Atodiresei N, Blügel S, Michely T. Oxygen orders differently under graphene: new superstructures on Ir(111). NANOSCALE 2016; 8:1932-1943. [PMID: 26426949 DOI: 10.1039/c5nr04976h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Using scanning tunneling microscopy, the oxygen adsorbate superstructures on bare Ir(111) are identified and compared to the ones formed by intercalation in between graphene and the Ir(111) substrate. For bare Ir(111) we observe O-(2 × 2) and O-(2 × 1) structures, thereby clarifying a persistent uncertainty about the existence of these structures and the role of defects for their stability. For the case of graphene-covered Ir(111), oxygen intercalation superstructures can be imaged through the graphene monolayer by choosing proper tunneling conditions. Depending on the pressure, temperature and duration of O2 exposure as well as on the graphene morphology, O-(2 × 2), O-(√3×√3)-R30°, O-(2 × 1) and O-(2√3 × 2√3)-R30° superstructures with respect to Ir(111) are observed under the graphene cover. Two of these structures, the O-(√3 × √3)-R30° and the (2√3 × 2√3)-R30° structure are only observed when the graphene layer is on top. Phase coexistence and formation conditions of the intercalation structures between graphene and Ir(111) are analyzed. The experimental results are compared to density functional theory calculations including dispersive forces. The existence of these phases under graphene and their absence on bare Ir(111) are discussed in terms of possible changes in the adsorbate-substrate interaction due to the presence of the graphene cover.
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Affiliation(s)
| | - U A Schröder
- II. Physikalisches Institut, Universität zu Köln, Germany.
| | - F Huttmann
- II. Physikalisches Institut, Universität zu Köln, Germany.
| | - W Jolie
- II. Physikalisches Institut, Universität zu Köln, Germany.
| | - F Craes
- II. Physikalisches Institut, Universität zu Köln, Germany.
| | - C Busse
- II. Physikalisches Institut, Universität zu Köln, Germany.
| | - V Caciuc
- Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich, Germany
| | - N Atodiresei
- Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich, Germany
| | - S Blügel
- Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich, Germany
| | - T Michely
- II. Physikalisches Institut, Universität zu Köln, Germany.
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9
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Dedkov Y, Voloshina E. Graphene growth and properties on metal substrates. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:303002. [PMID: 26151341 DOI: 10.1088/0953-8984/27/30/303002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Graphene-metal interface as one of the interesting graphene-based objects attracts much attention from both application and fundamental science points of view. This paper gives a timely review of the recent experimental works on the growth and the electronic properties of the graphene-metal interfaces. This work makes a link between huge amount of experimental and theoretical data allowing one to understand the influence of the metallic substrate on the electronic properties of a graphene overlayer and how its properties can be modified in a controllable way. The further directions of studies and applications of the graphene-metal interfaces are discussed.
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Affiliation(s)
- Yuriy Dedkov
- SPECS Surface Nano Analysis GmbH, Voltastrasse 5, 13355 Berlin, Germany
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10
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Altenburg SJ, Lattelais M, Wang B, Bocquet ML, Berndt R. Reaction of Phthalocyanines with Graphene on Ir(111). J Am Chem Soc 2015; 137:9452-8. [DOI: 10.1021/jacs.5b05558] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Simon J. Altenburg
- Institut
für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany
| | - Marie Lattelais
- Laboratoire
de Chimie, Ecole Normale Supérieure de Lyon, CNRS, Université de Lyon, F69007 Lyon, France
| | - Bin Wang
- School
of Chemical, Biological, and Materials Engineering, University of Oklahoma, 100 E. Boyd St., Norman, Oklahoma 73019-1004, United States
| | - Marie-Laure Bocquet
- Laboratoire
de Chimie, Ecole Normale Supérieure de Lyon, CNRS, Université de Lyon, F69007 Lyon, France
| | - Richard Berndt
- Institut
für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany
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11
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Martínez-Galera AJ, Brihuega I, Gutiérrez-Rubio A, Stauber T, Gómez-Rodríguez JM. Towards scalable nano-engineering of graphene. Sci Rep 2014; 4:7314. [PMID: 25472802 PMCID: PMC4255185 DOI: 10.1038/srep07314] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 11/11/2014] [Indexed: 11/17/2022] Open
Abstract
By merging bottom-up and top-down strategies we tailor graphene's electronic properties within nanometer accuracy, which opens up the possibility to design optical and plasmonic circuitries at will. In a first step, graphene electronic properties are macroscopically modified exploiting the periodic potential generated by the self assembly of metal cluster superlattices on a graphene/Ir(111) surface. We then demonstrate that individual metal clusters can be selectively removed by a STM tip with perfect reproducibility and that the structures so created are stable even at room temperature. This enables one to nanopattern circuits down to the 2.5 nm only limited by the periodicity of the Moiré-pattern, i.e., by the distance between neighbouring clusters, and different electronic and optical properties should prevail in the covered and uncovered regions. The method can be carried out on micro-meter-sized regions with clusters of different materials permitting to tune the strength of the periodic potential.
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Affiliation(s)
- A J Martínez-Galera
- Departamento Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - I Brihuega
- 1] Departamento Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain [2] Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - A Gutiérrez-Rubio
- 1] Departamento Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain [2] Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, E-28049 Madrid, Spain
| | - T Stauber
- 1] Departamento Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain [2] Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain [3] Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, E-28049 Madrid, Spain
| | - J M Gómez-Rodríguez
- 1] Departamento Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain [2] Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain
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12
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Niesner D, Fauster T. Image-potential states and work function of graphene. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:393001. [PMID: 25164535 DOI: 10.1088/0953-8984/26/39/393001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Image-potential states of graphene on various substrates have been investigated by two-photon photoemission and scanning tunneling spectroscopy. They are used as a probe for the graphene-substrate interaction and resulting changes in the (local) work function. The latter is driven by the work function difference between graphene and the substrate. This results in a charge transfer which also contributes to core-level shifts in x-ray photoemission. In this review article, we give an overview over the theoretical models and the experimental data for image-potential states and work function of graphene on various substrates.
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13
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Leicht P, Zielke L, Bouvron S, Moroni R, Voloshina E, Hammerschmidt L, Dedkov YS, Fonin M. In situ fabrication of quasi-free-standing epitaxial graphene nanoflakes on gold. ACS NANO 2014; 8:3735-3742. [PMID: 24694063 DOI: 10.1021/nn500396c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Addressing the multitude of electronic phenomena theoretically predicted for confined graphene structures requires appropriate in situ fabrication procedures yielding graphene nanoflakes (GNFs) with well-defined geometries and accessible electronic properties. Here, we present a simple strategy to fabricate quasi-free-standing GNFs of variable sizes, performing temperature programmed growth of graphene flakes on the Ir(111) surface and subsequent intercalation of gold. Using scanning tunneling microscopy (STM), we show that epitaxial GNFs on a perfectly ordered Au(111) surface are formed while maintaining an unreconstructed, singly hydrogen-terminated edge structure, as confirmed by the accompanying density functional theory (DFT) calculations. Using tip-induced lateral displacement of GNFs, we demonstrate that GNFs on Au(111) are to a large extent decoupled from the Au(111) substrate. The direct accessibility of the electronic states of a single GNF is demonstrated upon analysis of the quasiparticle interference patterns obtained by low-temperature STM. These findings open up an interesting playground for diverse investigations of graphene nanostructures with possible implications for device fabrication.
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Affiliation(s)
- Philipp Leicht
- Fachbereich Physik, Universität Konstanz , 78457 Konstanz, Germany
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14
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Boneschanscher MP, Hämäläinen SK, Liljeroth P, Swart I. Sample corrugation affects the apparent bond lengths in atomic force microscopy. ACS NANO 2014; 8:3006-3014. [PMID: 24559211 DOI: 10.1021/nn500317r] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Frequency modulation atomic force microscopy (AFM) allows the chemical structure of planar molecules to be determined with atomic resolution. Typically, these measurements are carried out in constant-height mode using carbon monoxide (CO) terminated tips. Such tips exhibit considerable flexibility, i.e., the CO molecule can bend laterally due to the tip-sample interaction. Using epitaxial graphene as a model system, we demonstrate experimentally that the apparent atomic positions measured by AFM depend on the sample corrugation. Using molecular mechanics simulations, we explain these observations by the interplay of the CO bending and the nonlinear background signal arising from the neighboring atoms. These effects depend nontrivially on the tip-sample distance and limit the achievable accuracy on the bond length determination based on AFM experiments.
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Affiliation(s)
- Mark P Boneschanscher
- Debye Institute for Nanomaterials Science, Utrecht University , P.O. Box 80000, 3508TA Utrecht, The Netherlands
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15
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Garcia-Lekue A, Balashov T, Olle M, Ceballos G, Arnau A, Gambardella P, Sanchez-Portal D, Mugarza A. Spin-dependent electron scattering at graphene edges on Ni(111). PHYSICAL REVIEW LETTERS 2014; 112:066802. [PMID: 24580701 DOI: 10.1103/physrevlett.112.066802] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Indexed: 06/03/2023]
Abstract
We investigate the scattering of surface electrons by the edges of graphene islands grown on Ni(111). By combining local tunneling spectroscopy and ab initio electronic structure calculations we find that the hybridization between graphene and Ni states results in strongly reflecting graphene edges. Quantum interference patterns formed around the islands reveal a spin-dependent scattering of the Shockley bands of Ni, which we attribute to their distinct coupling to bulk states. Moreover, we find a strong dependence of the scattering amplitude on the atomic structure of the edges, depending on the orbital character and energy of the surface states.
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Affiliation(s)
- A Garcia-Lekue
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, E-20018 San Sebastián, Spain and IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao, Spain
| | - T Balashov
- Catalan Institute of Nanoscience and Nanotecnology (ICN2), UAB Campus, E-08193 Bellaterra, Spain
| | - M Olle
- Catalan Institute of Nanoscience and Nanotecnology (ICN2), UAB Campus, E-08193 Bellaterra, Spain
| | - G Ceballos
- Catalan Institute of Nanoscience and Nanotecnology (ICN2), UAB Campus, E-08193 Bellaterra, Spain
| | - A Arnau
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, E-20018 San Sebastián, Spain and Centro de Física de Materiales CFM - MPC, Centro Mixto CSIC-UPV, Paseo Manuel de Lardizabal 5, E-20018, San Sebastián, Spain and Dpto. de Física de Materiales UPV/EHU, Facultad de Quimica, Paseo Manuel de Lardizabal 3, E-20018, San Sebastián, Spain
| | - P Gambardella
- Catalan Institute of Nanoscience and Nanotecnology (ICN2), UAB Campus, E-08193 Bellaterra, Spain and Instituciò Catalana de Recerca i Estudis Avancats (ICREA), E-08193 Barcelona, Spain and Department of Materials, ETH Zurich, Hönggerbergring 64, CH-8093 Zurich, Switzerland
| | - D Sanchez-Portal
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, E-20018 San Sebastián, Spain and Centro de Física de Materiales CFM - MPC, Centro Mixto CSIC-UPV, Paseo Manuel de Lardizabal 5, E-20018, San Sebastián, Spain
| | - A Mugarza
- Catalan Institute of Nanoscience and Nanotecnology (ICN2), UAB Campus, E-08193 Bellaterra, Spain
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16
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Craes F, Runte S, Klinkhammer J, Kralj M, Michely T, Busse C. Mapping image potential states on graphene quantum dots. PHYSICAL REVIEW LETTERS 2013; 111:056804. [PMID: 23952430 DOI: 10.1103/physrevlett.111.056804] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Indexed: 06/02/2023]
Abstract
Free-electron-like image potential states are observed in scanning tunneling spectroscopy on graphene quantum dots on Ir(111) acting as potential wells. The spectrum strongly depends on the size of the nanostructure as well as on the spatial position on top, indicating lateral confinement. Analysis of the substructure of the first state by the spatial mapping of the constant energy local density of states reveals characteristic patterns of confined states. The most pronounced state is not the ground state, but an excited state with a favorable combination of the local density of states and parallel momentum transfer in the tunneling process. Chemical gating tunes the confining potential by changing the local work function. Our experimental determination of this work function allows us to deduce the associated shift of the Dirac point.
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Affiliation(s)
- Fabian Craes
- II Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany.
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17
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Li Y, Zhang W, Morgenstern M, Mazzarello R. Electronic and magnetic properties of zigzag graphene nanoribbons on the (111) surface of Cu, Ag, and Au. PHYSICAL REVIEW LETTERS 2013; 110:216804. [PMID: 23745911 DOI: 10.1103/physrevlett.110.216804] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Indexed: 06/02/2023]
Abstract
We carry out an ab initio study of the structural, electronic, and magnetic properties of zigzag graphene nanoribbons on Cu(111), Ag(111), and Au(111). Both, H-free and H-terminated nanoribbons are considered revealing that the nanoribbons invariably possess edge states when deposited on these surfaces. In spite of this, they do not exhibit a significant magnetization at the edge, with the exception of H-terminated nanoribbons on Au(111), whose zero-temperature magnetic properties are comparable to those of free-standing nanoribbons. These results are explained by the different hybridization between the graphene 2p orbitals and those of the substrates and, for some models, also by the charge transfer between the surface and the nanoribbon. Interestingly, H-free nanoribbons on Au(111) and Ag(111) exhibit two main peaks in the local density of states around the Fermi energy, which originate from different states and, thus, do not indicate edge magnetism.
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Affiliation(s)
- Yan Li
- Institute for Theoretical Solid State Physics and JARA, RWTH Aachen University, D-52074 Aachen, Germany
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18
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Li Y, Subramaniam D, Atodiresei N, Lazić P, Caciuc V, Pauly C, Georgi A, Busse C, Liebmann M, Blügel S, Pratzer M, Morgenstern M, Mazzarello R. Absence of edge states in covalently bonded zigzag edges of graphene on Ir(111). ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2013; 25:1967-1972. [PMID: 23382024 DOI: 10.1002/adma.201204539] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Revised: 12/20/2012] [Indexed: 06/01/2023]
Abstract
The zigzag edges of graphene on Ir(111) are studied by ab initio simulations and low-temperature scanning tunneling spectroscopy, providing information about their structural, electronic, and magnetic properties. No edge state is found to exist, which is explained in terms of the interplay between a strong geometrical relaxation at the edge and a hybridization of the d orbitals of Ir atoms with the graphene orbitals at the edge.
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Affiliation(s)
- Yan Li
- Institute for Theoretical Solid State Physics and JARA, RWTH Aachen University, 52074 Aachen, Germany
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19
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Voloshina EN, Fertitta E, Garhofer A, Mittendorfer F, Fonin M, Thissen A, Dedkov YS. Electronic structure and imaging contrast of graphene moiré on metals. Sci Rep 2013; 3:1072. [PMID: 23330062 PMCID: PMC3547320 DOI: 10.1038/srep01072] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2012] [Accepted: 01/03/2013] [Indexed: 11/24/2022] Open
Abstract
Realization of graphene moiré superstructures on the surface of 4d and 5d transition metals offers templates with periodically modulated electron density, which is responsible for a number of fascinating effects, including the formation of quantum dots and the site selective adsorption of organic molecules or metal clusters on graphene. Here, applying the combination of scanning probe microscopy/spectroscopy and the density functional theory calculations, we gain a profound insight into the electronic and topographic contributions to the imaging contrast of the epitaxial graphene/Ir(111) system. We show directly that in STM imaging the electronic contribution is prevailing compared to the topographic one. In the force microscopy and spectroscopy experiments we observe a variation of the interaction strength between the tip and high-symmetry places within the graphene moiré supercell, which determine the adsorption sites for molecules or metal clusters on graphene/Ir(111).
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Affiliation(s)
- E N Voloshina
- Physikalische und Theoretische Chemie, Freie Universität Berlin, 14195 Berlin, Germany
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