A5070341110- Advanced Chemical Physics Studies
- Electron and X-Ray Spectroscopy Techniques
- Surface and Thin Film Phenomena
- X-ray Diffraction in Crystallography
- Magnetic properties of thin films
- Iron oxide chemistry and applications
- nanoparticles nucleation surface interactions
- Catalytic Processes in Materials Science
- Magnetic Properties and Synthesis of Ferrites
- Advanced Materials Characterization Techniques
- Chemical and Physical Properties of Materials
- Graphene research and applications
- X-ray Spectroscopy and Fluorescence Analysis
- Semiconductor materials and devices
- Advanced Condensed Matter Physics
- Advanced X-ray Imaging Techniques
- Crystallography and Radiation Phenomena
- Theoretical and Computational Physics
- Electronic and Structural Properties of Oxides
- Minerals Flotation and Separation Techniques
- Rare-earth and actinide compounds
- Semiconductor Quantum Structures and Devices
- Optical Coatings and Gratings
- Magnetic Properties of Alloys
- Quasicrystal Structures and Properties
Ludwig-Maximilians-Universität München
2010-2022
Institut für Urheber- und Medienrecht
2005-2015
LMU Klinikum
2014
Inspire
2013
Technical University of Munich
2009
European Synchrotron Radiation Facility
2005
Paul Drude Institute for Solid State Electronics
2000
Humboldt State University
1998
Fritz Haber Institute of the Max Planck Society
1987-1993
University of California, Berkeley
1993
The structure of a single layer graphene on Ru(0001) has been studied using surface x-ray diffraction. A surprising superstructure containing 1250 carbon atoms determined, whereby $25\ifmmode\times\else\texttimes\fi{}25$ unit cells lie $23\ifmmode\times\else\texttimes\fi{}23$ Ru. Each supercell contains $2\ifmmode\times\else\texttimes\fi{}2$ crystallographically inequivalent subcells caused by corrugation. Strong intensity oscillations in the rods demonstrate that Ru substrate is also...
The atomic geometry of the (1\ifmmode\times\else\texttimes\fi{}2) and (1\ifmmode\times\else\texttimes\fi{}3) structures Pt(100) surface has been determined from a low-energy electron-diffraction intensity analysis. Both are found to be missing-row type, consisting (111) microfacets, with similar relaxations in subsurface layers. In both reconstructions top-layer spacing is contracted by approximately 20% together buckling about 0.17 A\r{} third layer small lateral shift 0.04 second layer....
The structure of the commensurate (23x23) phase graphene on Ru(0001) has been analyzed by quantitative low-energy electron diffraction (LEED)-I(V) analysis and density-functional theory calculations. I(V) uses Fourier components as fitting parameters to determine vertical corrugation lateral relaxation top Ru layers. Graphene is shown be strongly corrugated 1.5 A with a minimum C-Ru distance 2.1 A. Additionally, displacements C atoms significant buckling in underlying layers are observed,...
Using ab initio thermodynamics we compile a phase diagram for the surface of Fe3O4(001) as function temperature and oxygen pressures. A hitherto ignored polar termination with octahedral iron forming wave-like structure along [110]-direction is identified lowest energy configuration over broad range gas-phase conditions. This novel geometry confirmed in x-ray diffraction analysis. The stabilization Fe3O4(001)-surface goes together dramatic changes electronic magnetic properties, e.g.,...
Using density-functional theory we identify a new low-energy structure for GaAs(001) in an As-poor environment. The discovered geometry is qualitatively different from the usual surface-dimer based reconstructions of III-V semiconductor (001) surfaces. stability structure, which has c(8x2) periodicity, explained terms bond saturation and favorable electrostatic interactions between surface atoms. Simulated scanning tunneling microscopy images are good agreement with experimental data,...
The ordered overlayer structures formed by Cs adsorbed on a Ru(0001) surface were analyzed use of low-energy electron diffraction (LEED). phase diagram reflects the dominance dipole-dipole repulsions between adparticles and comprises quasiliquid configurations characterized rings up to coverage \ensuremath{\Theta}=0.17, followed (2\ifmmode\times\else\texttimes\fi{}2) structure with maximum intensity spots at \ensuremath{\Theta}=0.23. Beyond \ensuremath{\Theta}=0.25, series rotated unit cells...
The adsorption of potassium on Al(111) at 90 K and 300 has been investigated by low-energy electron diffraction (LEED). Although a (\ensuremath{\surd}3 \ifmmode\times\else\texttimes\fi{} \ensuremath{\surd}3 )R30\ifmmode^\circ\else\textdegree\fi{} structure is formed each temperature, detailed LEED analysis revealed that the adsorbate positions are quite different unusual in case. At adatoms occupy on-top sites they substitutional sites. An irreversible phase transformation from former to...
The structure of the \ensuremath{\surd}3 \ifmmode\times\else\texttimes\fi{} R30\ifmmode^\circ\else\textdegree\fi{} overlayer formed by CO molecules adsorbed on a Ru(0001) was analyzed low energy electron diffraction. Anisotropic atomic motions under influence thermal excitation were taken into account adopting concept split positions. Apart from considerable improvement in structural refinement this technique provides information about dynamic processes. In particular, molecular axis found...
The geometry of adsorbed ${\mathrm{C}}_{60}$ influences its collective properties. We report the first dynamical low-energy electron diffraction study to determine a monolayer, $\mathrm{Ag}(111)\mathrm{\text{\ensuremath{-}}}(2\sqrt{3}\ifmmode\times\else\texttimes\fi{}2\sqrt{3})30\ifmmode^\circ\else\textdegree\fi{}\mathrm{\text{\ensuremath{-}}}{\mathrm{C}}_{60}$, and related density functional theory calculations. stable monolayer has molecules in vacancies that result from displacement...
From an analysis of the low-energy electron diffraction (LEED) intensities we have determined adsorption geometry two ordered H adlayers formed at T<270 K on Fe (110): a (2×1) and (3×1) structure, with ideal coverages θ= 1/2 (2)/(3) . Calculations were performed for different sites structural models, taking Fe–H bond length first Fe–Fe interlayer spacing as variable parameters. An R factor was used quantitative comparison experimental data. In both structures atoms are adsorbed highly...
The interaction of water with Fe3O4(001) is studied by density functional theory calculations including an on-site Coulomb term. For isolated molecules, dissociative adsorption strongly promoted at surface defect sites, while higher coverages a hydrogen-bonded network forms alternating molecular and dissociated species. This mixed mode suppression the (square root 2 x square 2)R45 degrees reconstruction are confirmed quantitative low energy electron diffraction analysis. Adsorbate induced...
The interaction of water with the Fe3O4(001) surface was investigated in a combined ambient pressure X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) study. uptake molecular hydroxyl species on (001) natural magnetite sample at near-ambient conditions quantified using O 1s spectra taken p(H2O) range from 10–9 to 2 Torr. At low (≤10–4–10–5 Torr) room temperature, we found that does not adsorb dissociatively surface, except defect sites. In contrast, progressive...
Silver's unique ability to selectively oxidize ethylene oxide under an oxygen atmosphere has long been known. Today it is the foundation of manufacturing. Yet, mechanism selective epoxide production unknown. Here we use a combination ultrahigh vacuum and in situ experimental methods along with theory show that only species shown produce oxide, so-called electrophilic appearing at 530.2 eV O 1s spectrum, adsorbed SO4. This adsorbate part 2D Ag/SO4 phase, where nonstoichiometric surface...
The reconstructed (1\ifmmode\times\else\texttimes\fi{}2) structure formed by saturation of a Ni(110) surface with adsorbed H atoms at T<180 K was investigated LEED. Excellent agreement between experimental and calculated I-V spectra for eleven nonequivalent beams obtained model in which parallel rows Ni the topmost layer are laterally shifted 0.3 A\r{} (``row pairing'') exhibits periodic vertical displacements (``buckling'') second layer.
The calculation of LEED intensities in a spherical-wave representation can be substantially simplified by symmetry relations. wave field around each atom is expanded symmetry-adapted functions where the local point atomic site applies. For overlayer systems with more than one per unit cell used when division crystal into monoatomic subplanes replaced containing all symmetrically equivalent positions.
From an analysis of the low-energy electron diffraction (LEED) intensities we have determined oscillatory distortion topmost interlayer spacings clean and (2×1)H covered Pd(110) surface as well exact adsorption geometry in this latter structure, which is formed at T&lt;180 K a coverage θH≤1.0. An R-factor was used for quantitative comparison with experimental data. The surface— d12=−5.1±1.5%, d23=+2.9±1.5%, d34 its bulk value 1.37 Å (with R factors RP=0.22 , RZJ=0.14 )— found to be...