Search

Your search keyword '"Oliver Ochedowski"' showing total 30 results
Start Over Author "Oliver Ochedowski"
30 results on '"Oliver Ochedowski"'

1. Effect of contaminations and surface preparation on the work function of single layer MoS2

Author

Oliver Ochedowski, Kolyo Marinov, Nils Scheuschner, Artur Poloczek, Benedict Kleine Bussmann, Janina Maultzsch, and Marika Schleberger

Subjects
KPFM, MoS2, NC-AFM, surface potential, work function, Technology, Chemical technology, TP1-1185, Science, Physics, QC1-999
Abstract

Thinning out MoS2 crystals to atomically thin layers results in the transition from an indirect to a direct bandgap material. This makes single layer MoS2 an exciting new material for electronic devices. In MoS2 devices it has been observed that the choice of materials, in particular for contact and gate, is crucial for their performance. This makes it very important to study the interaction between ultrathin MoS2 layers and materials employed in electronic devices in order to optimize their performance. In this work we used NC-AFM in combination with quantitative KPFM to study the influence of the substrate material and the processing on single layer MoS2 during device fabrication. We find a strong influence of contaminations caused by the processing on the surface potential of MoS2. It is shown that the charge transfer from the substrate is able to change the work function of MoS2 by about 40 meV. Our findings suggest two things. First, the necessity to properly clean devices after processing as contaminations have a great impact on the surface potential. Second, that by choosing appropriate materials the work function can be modified to reduce contact resistance.

Published
2014
Full Text
View/download PDF

2. Plasma-enhanced chemical vapor deposition of graphene on copper substrates

Author

Nicolas Woehrl, Oliver Ochedowski, Steven Gottlieb, Kosuke Shibasaki, and Stephan Schulz

Subjects
Physics, QC1-999
Abstract

A plasma enhanced vapor deposition process is used to synthesize graphene from a hydrogen/methane gas mixture on copper samples. The graphene samples were transferred onto SiO2 substrates and characterized by Raman spectroscopic mapping and atomic force microscope topographical mapping. Analysis of the Raman bands shows that the deposited graphene is clearly SLG and that the sheets are deposited on large areas of several mm2. The defect density in the graphene sheets is calculated using Raman measurements and the influence of the process pressure on the defect density is measured. Furthermore the origin of these defects is discussed with respect to the process parameters and hence the plasma environment.

Published
2014
Full Text
View/download PDF

3. Creating nanoporous graphene with swift heavy ions

Author

Flyura Djurabekova, Kai Nordlund, Arkady V. Krasheninnikov, E. H. Åhlgren, Marika Schleberger, Marko Karlušić, Henning Lebius, Milko Jakšić, Oliver Ochedowski, Rasim Mirzayev, Jani Kotakoski, Roland Kozubek, Aleksi A. Leino, Henrique Vázquez, Department of Physics, University of Helsinki, School of Chemistry, The University of Nottingham, University Park, Nottingham, NG7 2RD, UK., School of Chemistry, The University of Nottingham, University Park, Nottingham, NG7 2RD, UK. Code (UMR, EA, ...), Fakultät für Physik (CeNIDE), Universität Duisburg-Essen [Essen], Universität Wien, Department of Physics and Center for Nanointegration, University of Duisburg-Essen (CENIDE), Matériaux, Défauts et IRradiations (MADIR), Centre de recherche sur les Ions, les MAtériaux et la Photonique (CIMAP - UMR 6252), Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU), Institut Ruđer Bošković (IRB), Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Department of Applied Physics [Aalto], Aalto University, National University of Science and Technology (MISIS), Helsingin yliopisto = Helsingfors universitet = University of Helsinki, Universität Duisburg-Essen = University of Duisburg-Essen [Essen], Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), and Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, two-temperature model, Ionic bonding, 02 engineering and technology, 114 Physical sciences, 01 natural sciences, Ion, law.invention, symbols.namesake, law, 0103 physical sciences, General Materials Science, 010306 general physics, graphene, swift heavy ions, ta114, Swift heavy-ion irradiation, Nanoporous, Graphene, Ion track, ion irradiation, General Chemistry, Physik (inkl. Astronomie), 021001 nanoscience & nanotechnology, Nanopore, Chemical physics, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], symbols, Atomic physics, 0210 nano-technology, Raman spectroscopy, atomistic simulations, Graphene nanoribbons
Abstract

This article has an erratum: DOI 10.1016/j.carbon.2017.03.065 We examine swift heavy ion-induced defect production in suspended single layer graphene using Raman spectroscopy and a two temperature molecular dynamics model that couples the ionic and electronic subsystems. We show that an increase in the electronic stopping power of the ion results in an increase in the size of the pore-type defects, with a defect formation threshold at 1.22–1.48 keV/layer. We also report calculations of the specific electronic heat capacity of graphene with different chemical potentials and discuss the electronic thermal conductivity of graphene at high electronic temperatures, suggesting a value in the range of 1 Wm−1 K−1. These results indicate that swift heavy ions can create nanopores in graphene, and that their size can be tuned between 1 and 4 nm diameter by choosing a suitable stopping power.

Published
2017
Full Text
View/download PDF

4. Tunable quantum interference in bilayer graphene in double-resonant Raman scattering

Author

Oliver Ochedowski, Christoph Tyborski, Marika Schleberger, Felix Herziger, and Janina Maultzsch

Subjects
Materials science, FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, Molecular physics, law.invention, symbols.namesake, law, 0103 physical sciences, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), General Materials Science, 010306 general physics, Line (formation), Condensed Matter - Mesoscale and Nanoscale Physics, Scattering, General Chemistry, Physik (inkl. Astronomie), 021001 nanoscience & nanotechnology, Laser, Quantum interference, symbols, 0210 nano-technology, Bilayer graphene, Raman spectroscopy, Raman scattering, Excitation
Abstract

The line shape of the double-resonant 2D Raman mode in bilayer graphene is often considered to be characteristic for a certain laser excitation energy. Here, in a joint experimental and theoretical study, we analyze the dependence of the double-resonant Raman scattering processes in bilayer graphene on the electronic broadening parameter γ. We demonstrate that the ratio between symmetric and anti-symmetric scattering processes sensitively depends on the lifetime of the electronic states, explaining the experimentally observed variation of the complex 2D -mode line shape.

Published
2018

5. Highly active single-layer MoS

Author

Lukas, Madauß, Ioannis, Zegkinoglou, Henrique, Vázquez Muiños, Yong-Wook, Choi, Sebastian, Kunze, Meng-Qiang, Zhao, Carl H, Naylor, Philipp, Ernst, Erik, Pollmann, Oliver, Ochedowski, Henning, Lebius, Abdenacer, Benyagoub, Brigitte, Ban-d'Etat, A T Charlie, Johnson, Flyura, Djurabekova, Beatriz, Roldan Cuenya, and Marika, Schleberger

Abstract

Two-dimensional molybdenum-disulfide (MoS2) catalysts can achieve high catalytic activity for the hydrogen evolution reaction upon appropriate modification of their surface. The intrinsic inertness of the compound's basal planes can be overcome by either increasing the number of catalytically active edge sites or by enhancing the activity of the basal planes via a controlled creation of sulfur vacancies. Here, we report a novel method of activating the MoS2 surface using swift heavy ion irradiation. The creation of nanometer-scale structures by an ion beam, in combination with the partial sulfur depletion of the basal planes, leads to a large increase of the number of low-coordinated Mo atoms, which can form bonds with adsorbing species. This results in a decreased onset potential for hydrogen evolution, as well as in a significant enhancement of the electrochemical current density by over 160% as compared to an identical but non-irradiated MoS2 surface.

Published
2018

6. Highly active single-layer MoS2 catalysts synthesized by swift heavy ion irradiation

Author

Sebastian Kunze, Henrique Vázquez Muíños, Philipp Ernst, Carl H. Naylor, B. Ban-d’Etat, Beatriz Roldan Cuenya, Abdenacer Benyagoub, Lukas Madauß, Marika Schleberger, Yong-Wook Choi, Flyura Djurabekova, Oliver Ochedowski, Meng-Qiang Zhao, A. T. Charlie Johnson, Ioannis Zegkinoglou, Henning Lebius, Erik Pollmann, Universität Duisburg-Essen [Essen], Ruhr-Universität Bochum [Bochum], Helsinki Institute of Physics and Department of Physics, Department of Physics and Astronomy [Philadelphia], University of Pennsylvania [Philadelphia], Matériaux, Défauts et IRradiations (MADIR), Centre de recherche sur les Ions, les MAtériaux et la Photonique (CIMAP - UMR 6252), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Department of Interface Science [Berlin], Fritz-Haber-Institut der Max-Planck-Gesellschaft (FHI), Max Planck Society-Max Planck Society, Universität Duisburg-Essen = University of Duisburg-Essen [Essen], University of Pennsylvania, Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), and Department of Physics

Subjects
GRAPHENE, MECHANISM, Materials science, Ion beam, 116 Chemical sciences, SULFUR VACANCIES, EFFICIENT, chemistry.chemical_element, 02 engineering and technology, 010402 general chemistry, Photochemistry, Electrochemistry, 114 Physical sciences, 01 natural sciences, law.invention, Catalysis, chemistry.chemical_compound, Swift heavy ion, MOLYBDENUM-DISULFIDE, law, General Materials Science, Irradiation, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], Molybdenum disulfide, [PHYS]Physics [physics], SITES, HYDROGEN EVOLUTION, Graphene, 021001 nanoscience & nanotechnology, Sulfur, 0104 chemical sciences, chemistry, 0210 nano-technology
Abstract

Two-dimensional molybdenum-disulfide (MoS2) catlysts can achieve high catalytic activity for the hydrogen evolution reaction upon appropriate modification of their surface. The intrinsic inertness of the compound´s basal planes can be overcome by either increasing the number of catalytically active edge sites or by enhancing the activity of the basal planes via controlled creation of sulfur vacancies. Here, we report a novel method of activating the MoS2 surface in this respect using swift heavy ion irradiation. The creation of nanometer-scale structures by the ion beam, in combination with the partial sulfur depletion of the basal planes, leads to a large increase of the number of low-coordinated Mo atoms, which can form bonds with adsorbing species. This results in a decreased onset potential for hydrogen evolution, as well as in a significant enhance of the electrochemical current density by over 160% as compared to an identical but non-irradiated MoS2 surface.

Published
2018
Full Text
View/download PDF

7. Application of HOPG and CVD graphene as ion beam detectors

Author

Marika Schleberger, Roland Kozubek, Igor Zagoranskiy, Oliver Ochedowski, and Marko Karlušić

Subjects
Nuclear and High Energy Physics, Materials science, Ion beam, business.industry, Graphene, Analytical chemistry, swift heavy ions, graphene, HOPG, Raman spectroscopy, Chemical vapor deposition, Ion, law.invention, symbols.namesake, law, symbols, Optoelectronics, Pyrolytic carbon, Irradiation, business, Instrumentation, Graphene nanoribbons
Abstract

Highly ordered pyrolytic graphite and graphene created via chemical vapor deposition have been irradiated with high energetic I6+ ions. By Raman mapping an increase of the ID/IG ratio could be identified which arises from the ion induced defects. This ratio grows with increasing fluence. Using this as a tool, HOPG and graphene can be utilized to determine the ion beam spot size and its homogeneity. Both systems seem to be suitable for size determination of the spot. But due to the much higher sensitivity of graphene to ion irradiation, more detailed information regarding the homogeneity of the beam can only be derived using this 2D system. By comparison of both systems we conclude, that CVD graphene is more suitable as an ion beam detector, while HOPG is sufficient for a rough spot size analysis.

Published
2014
Full Text
View/download PDF

8. Defect engineering of single- and few-layer MoS 2 by swift heavy ion irradiation

Author

Carl H. Naylor, B. Ban-d'Etat, Lukas Madauß, Henning Lebius, Marika Schleberger, Oliver Ochedowski, Jani Kotakoski, A. T. Charlie Johnson, Fachbereich Physik [Duisburg], Universität Duisburg-Essen [Essen], Matériaux, Défauts et IRradiations (MADIR), Centre de recherche sur les Ions, les MAtériaux et la Photonique (CIMAP - UMR 6252), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Physics Department, University of Pennsylvania, U. of Penn., University of Vienna [Vienna], Universität Duisburg-Essen = University of Duisburg-Essen [Essen], Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), and Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, 02 engineering and technology, Substrate (electronics), 010402 general chemistry, 01 natural sciences, Swift heavy ion, General Materials Science, Irradiation, defects, Range (particle radiation), irradiation, business.industry, MoS 2, Mechanical Engineering, Bilayer, technology, industry, and agriculture, Defect engineering, General Chemistry, Physik (inkl. Astronomie), 021001 nanoscience & nanotechnology, Condensed Matter Physics, 0104 chemical sciences, Mechanics of Materials, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Optoelectronics, 0210 nano-technology, business, Layer (electronics)
Abstract

International audience; Wehave investigated the possibility to use swift heavy ion irradiation for nano-structuring supported and freestanding ultra-thin MoS2 samples. Our comprehensive study of the ion-induced morphological changes in various MoS2 samples shows that depending on the irradiation parameters a multitude of extended defects can be fabricated. These range from chains of nano-hillocks in bulk-like MoS2, and foldings in single and bilayer MoS2, to unique nano-incisions in supported and freestanding single layers of MoS2. Our data reveals that the primary mechanism responsible for the incisions in the ultrathin supported samples is the indirect heating by the SiO2 substrate.We thus conclude that an energy of less than 2 keV pernmtrack length is sufficient to fabricate nano-incisions in MoS2 which is compatible with the use of the smallest accelerators.

Published
2017
Full Text
View/download PDF

9. Fabrication of nanoporous graphene/polymer composite membranes

Author

Jens Schumacher, Christina Trautmann, Lukas Madauß, Marika Schleberger, Mathias Ulbricht, Jens Meyer, Mandakranta Ghosh, Oliver Ochedowski, Maria Eugenia Toimil-Molares, Henning Lebius, B. Ban-d'Etat, Rob G.H. Lammertink, Department of Physics and Center for Nanointegration, University of Duisburg-Essen (CENIDE), Center for Nanointegration Duisburg-Essen (CeNIDE), Universität Duisburg-Essen = University of Duisburg-Essen [Essen], Institute for Nanotechnology (MESA+), University of Twente, Matériaux, Défauts et IRradiations (MADIR), Centre de recherche sur les Ions, les MAtériaux et la Photonique (CIMAP - UMR 6252), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), GSI Materialforschung, Helmholtz zentrum für Schwerionenforschung GmbH (GSI), Universität Duisburg-Essen [Essen], University of Twente [Netherlands], Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), and Soft matter, Fluidics and Interfaces

Subjects
chemistry.chemical_classification, Materials science, Graphene, Nanoporous, Ion track, Graphene foam, Nanotechnology, 02 engineering and technology, Polymer, Physik (inkl. Astronomie), 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, Isotropic etching, 0104 chemical sciences, law.invention, Membrane, chemistry, law, 2023 OA procedure, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], General Materials Science, 0210 nano-technology, Graphene oxide paper
Abstract

International audience; Graphene is currently investigated as a promising membrane material in which selective pores can be created depending on the requirements of the application. However, to handle large-area nanoporous graphene a stable support material is needed. Here, we report on composite membranes consisting of large-area single layer nanoporous graphene supported by a porous polymer. The fabrication is based on ion-track nanotechnology with swift heavy ions directly creating atomic pores in the graphene lattice and damaged tracks in the polymer support. Subsequent chemical etching converts the latent ion tracks in the supporting polymer foil, here polyethylene terephthalate (PET), into open microchannels while the perfectly aligned pores in the graphene top layer remain unaffected. To avoid unintentional damage creation and delamination of the graphene layer from the substrate, the graphene is encapsulated by a protecting poly(methyl methacrylate) (PMMA) layer. By this procedure a stable composite membrane is obtained consisting of nanoporous graphene (coverage close to 100%) suspended across selfaligned track-etched microchannels in a polymer support film. Our method presents a facile way to create high quality suspended graphene of tunable pore size supported on a flexible porous polymeric support, thus enabling the development of membranes for fast and selective ultrafiltration separation processes.

Published
2017
Full Text
View/download PDF

10. Corrigendum to 'Creating nanoporous graphene with swift heavy ions' [Carbon 114 (April 2017) 511–518]

Author

Marko Karlušić, E. H. Åhlgren, Jani Kotakoski, R. Mirzayev, Aleksi A. Leino, Marika Schleberger, Flyura Djurabekova, Roland Kozubek, Kai Nordlund, Oliver Ochedowski, Henrique Vázquez, Arkady V. Krasheninnikov, M. Jakšić, and Henning Lebius

Subjects
Materials science, Nanoporous, Graphene, chemistry.chemical_element, Nanotechnology, 02 engineering and technology, General Chemistry, Physik (inkl. Astronomie), 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, 0104 chemical sciences, Ion, law.invention, chemistry, law, General Materials Science, 0210 nano-technology, Carbon
Published
2017

11. Resonant Raman profiles and µ-photoluminescence of atomically thin layers of molybdenum disulfide

Author

Janina Maultzsch, Marika Schleberger, Nils Scheuschner, and Oliver Ochedowski

Subjects
Thin layers, Photoluminescence, Exciton, Bilayer, Analytical chemistry, Resonance, 02 engineering and technology, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Electronic, Optical and Magnetic Materials, symbols.namesake, chemistry.chemical_compound, chemistry, Stokes shift, 0103 physical sciences, symbols, 010306 general physics, 0210 nano-technology, Raman spectroscopy, Molybdenum disulfide
Abstract

We present photoluminescence and resonant Raman measurements of atomically thin layers of molybdenum disulfide (MoS2) in the energy range of the A and B optical transitions. We found a Stokes shift of the transition energies in the resonant Raman measurements compared to the photoluminescence. The Stokes shift increases for the bilayer compared to the single layer. Furthermore, in resonance with the A transition, the Raman intensity of the A1g mode of the bilayer is six times larger than that of the single layer. Schematic crystal structure of molybdenum disulfide. (a) Top view (slightly tilted). (b) Side view.

Published
2012
Full Text
View/download PDF

12. Splitting of monolayer out-of-planeA1′Raman mode in few-layerWS2

Author

Marika Schleberger, Oliver Ochedowski, Christian Thomsen, Nils Scheuschner, Felix Kampmann, Matthias Staiger, Janina Maultzsch, and Roland Gillen

Subjects
Physics, Condensed matter physics, Phonon, Resonance, Nanotechnology, Condensed Matter Physics, Electronic, Optical and Magnetic Materials, symbols.namesake, Homogeneous space, Monolayer, symbols, Density functional theory, Raman spectroscopy, Excitation, Energy (signal processing)
Abstract

We present Raman measurements of mono- and few-layer ${\mathrm{WS}}_{2}$. We study the monolayer ${A}_{1}^{\ensuremath{'}}$ mode around $420{\mathrm{cm}}^{\ensuremath{-}1}$ and its evolution with the number of layers. We show that with increasing layer number there are an increasing number of possible vibrational patterns for the out-of-plane Raman mode: in $N$-layer ${\mathrm{WS}}_{2}$ there are $N$ $\mathrm{\ensuremath{\Gamma}}$-point phonons evolving from the ${A}_{1}^{\ensuremath{'}}$ monolayer mode. For an excitation energy close to resonance with the $A$ excitonic transition energy, we were able to observe all of these $N$ components, irrespective of their Raman activity. Density functional theory calculations support the experimental findings and make it possible to attribute the modes to their respective symmetries. The findings described here are of general importance for all other phonon modes in ${\mathrm{WS}}_{2}$ and other layered transition-metal dichalcogenide systems in the few-layer regime.

Published
2015
Full Text
View/download PDF

13. Studies of surface nanostructure formation due to swift heavy ion irradiation under grazing incidence

Author

Oliver Ochedowski, C Grygief, Elisabeth Gruber, Jimmy Rangama, Abdenacer Benyagoub, Delphine Levavasseur, Y Y Wang, Henning Lebius, B. Ban d'Etat, Friedrich Aumayr, E. Lattouf, Lorenz Bergen, P. Salou, and Marika Schleberger

Subjects
History, Nanostructure, Materials science, business.industry, Physik (inkl. Astronomie), Molecular physics, Charged particle, Computer Science Applications, Education, Ion, Optics, Swift heavy ion, Quantum dot, Irradiation, Mica, Nanodot, business
Abstract

In this contribution we present new experimental results for swift heavy ion irradiation under grazing incidence. This particular collision geometry forces the track formation to a region close to the surface, sometimes visible as a chain of individual nanodots, whose length can be controlled by the angle of incidence. For irradiation of mica surfaces a new track form is observed.

Published
2015

14. Nanostructuring Graphene by Dense Electronic Excitation

Author

Andrey Turchanin, B. Ban-d'Etat, Ossi Lehtinen, Marko Karlušić, Milko Jakšić, Marika Schleberger, Henning Lebius, Ute Kaiser, Oliver Ochedowski, Fachbereich Physik [Duisburg], Universität Duisburg-Essen [Essen], Universität Ulm - Ulm University [Ulm, Allemagne], Friedrich-Schiller-Universität = Friedrich Schiller University Jena [Jena, Germany], Matériaux, Défauts et IRradiations (MADIR), Centre de recherche sur les Ions, les MAtériaux et la Photonique (CIMAP - UMR 6252), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Institut Ruđer Bošković (IRB), Universität Duisburg-Essen = University of Duisburg-Essen [Essen], Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), and Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Ion beam, FOS: Physical sciences, Bioengineering, Nanotechnology, 02 engineering and technology, 01 natural sciences, law.invention, Swift heavy ion, law, 0103 physical sciences, General Materials Science, Electrical and Electronic Engineering, 010306 general physics, Graphene oxide paper, Condensed Matter - Materials Science, Graphene, Mechanical Engineering, Bilayer, Materials Science (cond-mat.mtrl-sci), graphene, swift heavy ion, folding, General Chemistry, Physik (inkl. Astronomie), Condensed Matter Physics, 021001 nanoscience & nanotechnology, Nanopore, Mechanics of Materials, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], 0210 nano-technology, Bilayer graphene, Graphene nanoribbons
Abstract

The ability to manufacture tailored graphene nanostructures is a key factor to fully exploit its enormous technological potential. We have investigated nanostructures created in graphene by swift heavy ion induced folding. For our experiments, single layers of graphene exfoliated on various substrates and freestanding graphene have been irradiated and analyzed by atomic force and high resolution transmission electron microscopy as well as Raman spectroscopy. We show that the dense electronic excitation in the wake of the traversing ion yields characteristic nanostructures each of which may be fabricated by choosing the proper irradiation conditions. These nanostructures include unique morphologies such as closed bilayer edges with a given chirality or nanopores within supported as well as freestanding graphene. The length and orientation of the nanopore, and thus of the associated closed bilayer edge, may be simply controlled by the direction of the incoming ion beam. In freestanding graphene, swift heavy ion irradiation induces extremely small openings, offering the possibility to perforate graphene membranes in a controlled way., Comment: 16 pages, 5 figures, submitted to Nanotechnology

Published
2015
Full Text
View/download PDF

15. Double-resonant LA phonon scattering in defective graphene and carbon nanotubes

Author

Marika Schleberger, Oliver Ochedowski, Felix Herziger, Christoph Tyborski, and Janina Maultzsch

Subjects
Phonon, FOS: Physical sciences, 02 engineering and technology, Carbon nanotube, 01 natural sciences, law.invention, Condensed Matter::Materials Science, symbols.namesake, law, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), 0103 physical sciences, 010306 general physics, Spectroscopy, Physics, Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed matter physics, Phonon scattering, Graphene, Materials Science (cond-mat.mtrl-sci), Physik (inkl. Astronomie), Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Electronic, Optical and Magnetic Materials, symbols, 0210 nano-technology, Raman spectroscopy, Energy (signal processing), Excitation
Abstract

We present measurements of the $D''$ Raman mode in graphene and carbon nanotubes at different laser excitation energies. The Raman mode around 1050 - 1150\,cm$^{-1}$ originates from a double-resonant scattering process of longitudinal acoustic (LA) phonons with defects. We investigate its dependence on laser excitation energy, on the number of graphene layers and on the carbon nanotube diameter. We assign this Raman mode to so-called 'inner' processes with resonant phonons mainly from the $\Gamma-K$ high-symmetry direction. The asymmetry of the $D''$ mode is explained by additional contributions from phonons next to the $\Gamma-K$ line. Our results demonstrate the importance of inner contributions in the double-resonance scattering process and add a fast method to investigate acoustic phonons in graphene and carbon nanotubes by optical spectroscopy., Comment: 6 pages, 3 figures, 1 page SI, accepted for publication in Phys. Rev. B

Published
2014
Full Text
View/download PDF

16. Folding two dimensional crystals by swift heavy ion irradiation

Author

Lara Brökers, B. Ban-d'Etat, Henning Lebius, Hanna Bukowska, Victor M. Freire Soler, Oliver Ochedowski, Marika Schleberger, Fachbereich Physik [Duisburg], Universität Duisburg-Essen [Essen], University of Barcelona, Matériaux, Défauts et IRradiations (MADIR), Centre de recherche sur les Ions, les MAtériaux et la Photonique (CIMAP - UMR 6252), Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU), Universität Duisburg-Essen = University of Duisburg-Essen [Essen], Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), and Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Nuclear and High Energy Physics, Materials science, Hexagonal crystal system, Graphene, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Ion, law.invention, Folding (chemistry), Crystal, Swift heavy ion, Chemical physics, law, 0103 physical sciences, Mechanical strength, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Irradiation, Atomic physics, 010306 general physics, 0210 nano-technology, Instrumentation
Abstract

International audience; Ion irradiation of graphene, the showcase model of two dimensional crystals, has been successfully applied to induce various modifications in the graphene crystal. One of these modifications is the formation of origami like foldings in graphene which are created by swift heavy ion irradiation under glancing incidence angle. These foldings can be applied to locally alter the physical properties of graphene like mechanical strength or chemical reactivity. In this work we show that the formation of foldings in two dimensional crystals is not restricted to graphene but can be applied for other materials like MoS2 and hexagonal BN as well. Further we show that chemical vapour deposited graphene forms foldings after swift heavy ion irradiation while chemical vapour deposited MoS2 does not.

Published
2014
Full Text
View/download PDF

17. Graphitic nanostripes in silicon carbide surfaces created by swift heavy ion irradiation

Author

O. Osmani, Marika Schleberger, Benedict Kleine Bussmann, Henning Lebius, B. Ban-d'Etat, Oliver Ochedowski, Martin Schade, Fachbereich Physik [Duisburg], Universität Duisburg-Essen [Essen], Donostia International Physics Center (DIPC), University of the Basque Country/Euskal Herriko Unibertsitatea (UPV/EHU), Faculty of Chemistry, University of Duisburg-Essen, Matériaux, Défauts et IRradiations (MADIR), Centre de recherche sur les Ions, les MAtériaux et la Photonique (CIMAP - UMR 6252), Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU), Universität Duisburg-Essen = University of Duisburg-Essen [Essen], Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), and Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Multidisciplinary, Materials science, General Physics and Astronomy, Nanotechnology, General Chemistry, Physik (inkl. Astronomie), General Biochemistry, Genetics and Molecular Biology, Ion, chemistry.chemical_compound, Swift heavy ion, chemistry, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Silicon carbide, Irradiation
Abstract

International audience; The controlled creation of defects in silicon carbide represents a major challenge. A wellknown and efficient tool for defect creation in dielectric materials is the irradiation with swift (EkinZ500 keV/amu) heavy ions, which deposit a significant amount of their kinetic energy into the electronic system. However, in the case of silicon carbide, a significant defect creation by individual ions could hitherto not be achieved. Here we present experimental evidence that silicon carbide surfaces can be modified by individual swift heavy ions with an energy well below the proposed threshold if the irradiation takes place under oblique angles. Depending on the angle of incidence, these grooves can span several hundreds of nanometres. We show that our experimental data are fully compatible with the assumption that each ion induces the sublimation of silicon atoms along its trajectory, resulting in narrow graphitic grooves in the silicon carbide matrix.

Published
2014
Full Text
View/download PDF

18. Photoluminescence of freestanding single- and few-layer MoS 2

Author

Roland Gillen, Oliver Ochedowski, Marika Schleberger, Nils Scheuschner, Janina Maultzsch, and Anne-Marie Kaulitz

Subjects
Condensed Matter - Materials Science, Photoluminescence, Materials science, Condensed matter physics, business.industry, Exciton, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, Substrate (electronics), Physik (inkl. Astronomie), Condensed Matter Physics, Electronic, Optical and Magnetic Materials, symbols.namesake, symbols, Optoelectronics, Direct and indirect band gaps, Photoluminescence excitation, van der Waals force, Trion, business, Energy (signal processing)
Abstract

We present a photoluminescence study of freestanding and Si/${\text{SiO}}_{2}$ supported single- and few-layer ${\text{MoS}}_{2}$. The single-layer exciton peak (A) is only observed in freestanding ${\text{MoS}}_{2}$. The photoluminescence of supported single-layer ${\text{MoS}}_{2}$ instead originates from the A${}^{\ensuremath{-}}$ (trion) peak as the ${\text{MoS}}_{2}$ is $n$-type doped from the substrate. In bilayer ${\text{MoS}}_{2}$, the van der Waals interaction with the substrate decreases the indirect band gap energy by up to $\ensuremath{\approx}80$ meV. Furthermore, the photoluminescence spectra of suspended ${\text{MoS}}_{2}$ can be influenced by interference effects.

Published
2014

19. Detecting swift heavy ion irradiation effects with graphene

Author

S. Akcöltekin, Marika Schleberger, Oliver Ochedowski, Henning Lebius, B. Ban-d‘Etat, Fachbereich Physik [Duisburg], Universität Duisburg-Essen [Essen], Matériaux, Défauts et IRradiations (MADIR), Centre de recherche sur les Ions, les MAtériaux et la Photonique (CIMAP - UMR 6252), Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU), Universität Duisburg-Essen = University of Duisburg-Essen [Essen], Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), and Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Nuclear and High Energy Physics, Materials science, Analytical chemistry, FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, law.invention, Swift heavy ion, law, 0103 physical sciences, Irradiation, Graphite, 010306 general physics, Instrumentation, Condensed Matter - Materials Science, Graphene, Atomic force microscopy, Materials Science (cond-mat.mtrl-sci), Physik (inkl. Astronomie), 021001 nanoscience & nanotechnology, Ion fluence, Exfoliation joint, Single layer graphene, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Atomic physics, 0210 nano-technology
Abstract

In this paper we show how single layer graphene can be utilized to study swift heavy ion (SHI) modifications on various substrates. The samples were prepared by mechanical exfoliation of bulk graphite onto SrTiO$_3$, NaCl and Si(111), respectively. SHI irradiations were performed under glancing angles of incidence and the samples were analysed by means of atomic force microscopy in ambient conditions. We show that graphene can be used to check whether the irradiation was successful or not, to determine the nominal ion fluence and to locally mark SHI impacts. In case of samples prepared in situ, graphene is shown to be able to catch material which would otherwise escape from the surface., 10 pages, 3 figures

Published
2013
Full Text
View/download PDF

20. Radiation hardness of graphene and MoS2 field effect devices against swift heavy ion irradiation

Author

Kolyo Marinov, G. Wilbs, Gregor Keller, Markus Bender, Janina Maultzsch, Marika Schleberger, Franz-Josef Tegude, Oliver Ochedowski, Daniel Severin, and Nils Scheuschner

Subjects
Materials science, General Physics and Astronomy, Field effect, FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, Fluence, law.invention, Ion, symbols.namesake, Swift heavy ion, law, 0103 physical sciences, Irradiation, 010306 general physics, Elektrotechnik, Condensed Matter - Materials Science, business.industry, Graphene, Materials Science (cond-mat.mtrl-sci), Physik (inkl. Astronomie), 021001 nanoscience & nanotechnology, symbols, Optoelectronics, Field-effect transistor, 0210 nano-technology, Raman spectroscopy, business
Abstract

We have investigated the deterioration of field effect transistors based on twodimensional materials due to irradiation with swift heavy ions. Devices were prepared with exfoliated single layers of MoS2 and graphene, respectively. They were characterized before and after irradiation with 1.14 GeV U228+2 ions using three different fluences. By electrical characterization, atomic force microscopy and Raman spectroscopy we show that the irradiation leads to significant changes of structural and electrical properties. At the highest fluence of 4 x 102^11 ions/cm^2, the MoS2 transistor is destroyed, while the graphene based device remains operational, albeit with an inferior performance.

Published
2013
Full Text
View/download PDF

21. Routes to rupture and folding of graphene on rough 6H-SiC(0001) and their identification

Author

Michael Reichling, B. Kleine Bussmann, Oliver Ochedowski, Tjeerd Rogier Johannes Bollmann, Matthias Temmen, and Marika Schleberger

Subjects
SiC, Materials science, Stacking, General Physics and Astronomy, Nanotechnology, lcsh:Chemical technology, lcsh:Technology, Molecular physics, Kelvin probe force microscopy (KPFM), local contact potential difference (LCPD), Full Research Paper, law.invention, Swift heavy ion, law, non-contact atomic force microscopy (NC-AFM), Microscopy, lcsh:TP1-1185, General Materials Science, Electrical and Electronic Engineering, lcsh:Science, Kelvin probe force microscope, lcsh:T, Graphene, graphene, Physik (inkl. Astronomie), lcsh:QC1-999, Nanoscience, Zigzag, lcsh:Q, Bilayer graphene, Volta potential, lcsh:Physics
Abstract

Twisted few layer graphene (FLG) is highly attractive from an application point of view, due to its extraordinary electronic properties. In order to study its properties, we demonstrate and discuss three different routes to in situ create and identify (twisted) FLG. Single layer graphene (SLG) sheets mechanically exfoliated under ambient conditions on 6H-SiC(0001) are modified by (i) swift heavy ion (SHI) irradiation, (ii) by a force microscope tip and (iii) by severe heating. The resulting surface topography and the surface potential are investigated with non-contact atomic force microscopy (NC-AFM) and Kelvin probe force microscopy (KPFM). SHI irradiation results in rupture of the SLG sheets, thereby creating foldings and bilayer graphene (BLG). Applying the other modification methods creates enlarged (twisted) graphene foldings that show rupture along preferential edges of zigzag and armchair type. Peeling at a folding over an edge different from a low index crystallographic direction can result in twisted BLG, showing a similar height as Bernal (or AA-stacked) BLG in NC-AFM images. The rotational stacking can be identified by a significant contrast in the local contact potential difference (LCPD) measured by KPFM. © 2013 Komkova et al; licensee Beilstein-Institut. OA platinum

Published
2013

22. Manipulation of the graphene surface potential by ion irradiation

Author

B. Kleine Bussmann, Marika Schleberger, Henning Lebius, Oliver Ochedowski, B. Ban d'Etat, Fachbereich Physik [Duisburg], Universität Duisburg-Essen [Essen], Matériaux, Défauts et IRradiations (MADIR), Centre de recherche sur les Ions, les MAtériaux et la Photonique (CIMAP - UMR 6252), Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU), Universität Duisburg-Essen = University of Duisburg-Essen [Essen], Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), and Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Physics and Astronomy (miscellaneous), FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, Molecular physics, Ion, law.invention, chemistry.chemical_compound, law, 0103 physical sciences, Silicon carbide, Work function, Irradiation, 010302 applied physics, Kelvin probe force microscope, Range (particle radiation), Condensed Matter - Materials Science, Graphene, Doping, Materials Science (cond-mat.mtrl-sci), Physik (inkl. Astronomie), 021001 nanoscience & nanotechnology, chemistry, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], 0210 nano-technology
Abstract

We show that the work function of exfoliated single layer graphene can be modified by irradiation with swift (E_{kin}=92 MeV) heavy ions under glancing angles of incidence. Upon ion impact individual surface tracks are created in graphene on SiC. Due to the very localized energy deposition characteristic for ions in this energy range, the surface area which is structurally altered is limited to ~ 0.01 mum^2 per track. Kelvin probe force microscopy reveals that those surface tracks consist of electronically modified material and that a few tracks suffice to shift the surface potential of the whole single layer flake by ~ 400 meV. Thus, the irradiation turns the initially n-doped graphene into p-doped graphene with a hole density of 8.5 x 10^{12} holes/cm^2. This doping effect persists even after heating the irradiated samples to 500{\deg}C. Therefore, this charge transfer is not due to adsorbates but must instead be attributed to implanted atoms. The method presented here opens up a new way to efficiently manipulate the charge carrier concentration of graphene., Comment: 6 pages, 4 figures

Published
2013
Full Text
View/download PDF

24. Electronic characterization of single-layer MoS2 sheets exfoliated on SrTiO3

Author

Oliver Ochedowski, Kolyo Marinov, Nils Scheuschner, Janina Maultzsch, Marika Schleberger, and Benedict Kleine Bußmann

Subjects
Kelvin probe force microscope, Dipole, symbols.namesake, Materials science, Band gap, symbols, Direct and indirect band gaps, Substrate (electronics), Thin film, Raman spectroscopy, Layer (electronics), Molecular physics
Abstract

Single layer regions of MoS2 on SiO2 and SrTiO3 were identified by Raman spectroscopy and μ-photoluminescence before Kelvin probe force microscopy was performed. For the already known system MoS2/SiO2 we find 1.839 eV for the direct bandgap, in good agreement with earlier results. On MoS2/SrTiO3 the direct bandgap was determined to be 1.829 eV. From our Kelvin probe data we infer that the SrTiO3 substrate leads to a dipole layer at the interface of the MoS2 single layer. The corresponding μ-PL measurements however show no significant decrease of the bandgap. This shows, that in the case of MoS2 the carrier type as well as concentration is not significantly influenced by the choice of SrTiO3 as the substrate compared to SiO2.

Published
2012
Full Text
View/download PDF

25. Laser cleaning of exfoliated graphene

Author

Marika Schleberger, Benedict Kleine Bußmann, and Oliver Ochedowski

Subjects
Materials science, business.industry, Graphene, Ultra-high vacuum, Analytical chemistry, chemistry.chemical_element, Laser, Exfoliation joint, Oxygen, law.invention, chemistry, law, Microscopy, Optoelectronics, Irradiation, Laser heating, business
Abstract

We have employed atomic force and Kelvin-Probe force microscopy to study graphene sheets exfoliated on TiO2 under the influence of local heating achieved by laser irradiation. Exfoliation and irradiation took place under ambient conditions, the measurements were performed in ultra high vacuum. We show that after irradiation times of 6 min, an increase of the surface potential is observed which indicates a decrease of p-type carrier concentration. We attribute this effect to the removal of adsorbates like water and oxygen. After irradiation times of 12 min our topography images reveal severe structural modifications of graphene. These resemble the nanocrystallite network which form on graphene/SiO2 but after much longer irradiation times. From our results we propose that short laser heating at moderate powers might offer a way to clean graphene without inducing unwanted structural modifications.

Published
2012
Full Text
View/download PDF

26. Doping of graphene exfoliated on SrTiO3

Author

Benedict Kleine Bußmann, Marika Schleberger, and Oliver Ochedowski

Subjects
Kelvin probe force microscope, Materials science, Condensed matter physics, Graphene, Mechanical Engineering, Bioengineering, Nanotechnology, General Chemistry, Physik (inkl. Astronomie), law.invention, Mechanics of Materials, law, General Materials Science, Work function, Graphite, Electrical and Electronic Engineering, Bilayer graphene, Volta potential, Graphene nanoribbons, Graphene oxide paper
Abstract

We present atomic force microscopy and scanning Kelvin probe data obtained under ultra-high vacuum conditions from graphene exfoliated on crystalline SrTiO(3) substrates. The contact potential difference shows a monotonic increase with the number of graphene layers until after five layers of saturation is reached. By identifying the saturation value with the work function of graphite we determine the work function of single and bilayer graphene to be Φ(SLG) = 4.409 ± 0.039 eV and Φ(BLG) = 4.516 ± 0.035 eV, respectively. In agreement with the higher work function of single-layer graphene with respect to free-standing graphene, our measurements indicate an accumulation of charge carriers corresponding to a doping of the exfoliated graphene layer with electrons.

Published
2011

27. Hydration layers trapped between graphene and a hydrophilic substrate

Author

Matthias Temmen, Marika Schleberger, Tjeerd Rogier Johannes Bollmann, Michael Reichling, and Oliver Ochedowski

Subjects
Physics, Ostwald ripening, Graphene, Annealing (metallurgy), General Physics and Astronomy, Nanotechnology, Interfacial adhesion, Physik (inkl. Astronomie), law.invention, symbols.namesake, Chemical engineering, law, Homogeneous, Transfer printing, Monolayer, symbols
Abstract

Graphene is mechanically exfoliated on (111) under ambient conditions. We demonstrate the formation of a several monolayer thick hydration layer on the hydrophilic substrate and its response to annealing at temperatures up to 750 K in an ultra-high vacuum environment. Upon heating, water is released, however, it is impossible to remove the first layer. The initially homogeneous film separates into water-containing and water-free domains by two-dimensional Ostwald ripening. Upon severe heating, thick graphene multilayers undergo rupture, while nanoblisters confining sealed water appear on thinner sheets, capable of the storage and release of material. From modeling the dimensions of the nanoblisters, we estimate the graphene/(111) interfacial adhesion energy to be , thereby viable for polymer-assisted transfer printing.

Published
2014
Full Text
View/download PDF

28. Graphene on Si(111)7×7

Author

Janina Maultzsch, M. El Kharrazi, Marika Schleberger, Nils Scheuschner, G. Begall, and Oliver Ochedowski

Subjects
Kelvin probe force microscope, Condensed Matter - Materials Science, Materials science, Graphene, Mechanical Engineering, Spatially resolved, Ultra-high vacuum, Doping, Bioengineering, General Chemistry, Physik (inkl. Astronomie), Molecular physics, law.invention, Mechanics of Materials, law, General Materials Science, Nanometre, Crystalline silicon, Electrical and Electronic Engineering, Well-defined
Abstract

We demonstrate that it is possible to mechanically exfoliate graphene under ultra high vacuum conditions on the atomically well defined surface of single crystalline silicon. The flakes are several hundred nanometers in lateral size and their optical contrast is very faint in agreement with calculated data. Single layer graphene is investigated by Raman mapping. The G and 2D peaks are shifted and narrowed compared to undoped graphene. With spatially resolved Kelvin probe measurements we show that this is due to p-type doping with hole densities of n_h \simeq 6x10^{12} cm^{-2}. The in vacuo preparation technique presented here should open up new possibilities to influence the properties of graphene by introducing adsorbates in a controlled way., Comment: 8 pages, 7 figures

Published
2012
Full Text
View/download PDF

29. Raman spectra of graphene exfoliated on insulating crystalline substrates

Author

Marika Schleberger, Volker Buck, M. Neubert, Hanna Bukowska, Oliver Ochedowski, F. Meinerzhagen, and S. Akcöltekin

Subjects
Physics, business.industry, Graphene, Bilayer, General Physics and Astronomy, Substrate (electronics), Physik (inkl. Astronomie), law.invention, symbols.namesake, law, symbols, Optoelectronics, business, Raman spectroscopy, Bilayer graphene, Single crystal, Graphene nanoribbons, Graphene oxide paper
Abstract

We have investigated single layer, bilayer and few-layer graphene exfoliated on SiO2 and on single crystal surfaces of SrTiO3, Al2O3 and TiO2 using Raman spectroscopy. The typical 'fingerprint' 2D peak turns out to be indicative of the number of graphene layers independent of the substrate material. The morphological quality of the graphene is as good as on SiO2 substrates for all the materials. We find evidence for substrate-induced changes due to doping. With most substrates, hole doping is observed, but with SrTiO3 we have identified a dielectric substrate with which electron accumulation in graphene can be achieved.

Published
2011
Full Text
View/download PDF

30. Doping of graphene exfoliated on SrTiO3.

Author

Benedict Kleine, Oliver Ochedowski, and Marika Schleberger

Subjects
*GRAPHENE, *STRONTIUM compounds, *ATOMIC force microscopy, *ELECTRON work function, *VACUUM technology, *SUBSTRATES (Materials science)
Abstract

We present atomic force microscopy and scanning Kelvin probe data obtained under ultra-high vacuum conditions from graphene exfoliated on crystalline SrTiO3 substrates. The contact potential difference shows a monotonic increase with the number of graphene layers until after five layers of saturation is reached. By identifying the saturation value with the work function of graphite we determine the work function of single and bilayer graphene to be PhSLG = 4.409 +- 0.039 eV and PhBLG = 4.516 +- 0.035 eV, respectively. In agreement with the higher work function of single-layer graphene with respect to free-standing graphene, our measurements indicate an accumulation of charge carriers corresponding to a doping of the exfoliated graphene layer with electrons. [ABSTRACT FROM AUTHOR]

Published
2011

Catalog

Books, media, physical & digital resources
See catalog results