A5084043784- Surface and Thin Film Phenomena
- Electron and X-Ray Spectroscopy Techniques
- Physics of Superconductivity and Magnetism
- Electronic and Structural Properties of Oxides
- Semiconductor materials and devices
- X-ray Spectroscopy and Fluorescence Analysis
- Semiconductor materials and interfaces
- Magnetic properties of thin films
- Magnetic and transport properties of perovskites and related materials
- Advanced Condensed Matter Physics
- Advanced Chemical Physics Studies
- Molecular Junctions and Nanostructures
- Copper Interconnects and Reliability
- X-ray Diffraction in Crystallography
- Crystallography and Radiation Phenomena
- Ferroelectric and Piezoelectric Materials
- Anodic Oxide Films and Nanostructures
- Graphene research and applications
- Semiconductor Quantum Structures and Devices
- Advanced Materials Characterization Techniques
- Catalytic Processes in Materials Science
- Corrosion Behavior and Inhibition
- Advanced X-ray Imaging Techniques
- Copper-based nanomaterials and applications
- Electrocatalysts for Energy Conversion
Diamond Light Source
2015-2025
Didcot Community Hospital
2017
European Synchrotron Radiation Facility
2007-2016
European Science Foundation
2003-2014
Elkhorn Slough Foundation
2004-2009
CEA LETI
2009
Institut polytechnique de Grenoble
2009
S.P.E.C.I.E.S.
2009
STMicroelectronics (France)
2009
Deutsches Elektronen-Synchrotron DESY
1984-2008
The nonlocal van der Waals density functional approach is applied to calculate the binding of graphene Ir(111). precise agreement calculated mean height h = 3.41 Å C atoms with their (3.38±0.04) as measured by x-ray standing wave technique provides a benchmark for applicability functional. We find bonding Ir(111) be due interaction an antibonding average contribution from chemical interaction. Despite its globally repulsive character, in certain areas large moiré unit cell charge...
Interface energetics are of fundamental importance in organic and molecular electronics. By combining complementary experimental techniques first-principles calculations, we resolve the complex interplay among several interfacial phenomena that collectively determine electronic structure strong electron acceptor tetrafluoro-tetracyanoquinodimethane chemisorbed on copper. The combination adsorption-induced geometric distortion molecules, metal-to-molecule charge transfer, molecule-to-metal...
The interfaces formed between pentacene (PEN) and perfluoropentacene (PFP) molecules Cu(111) were studied using photoelectron spectroscopy, X-ray standing wave (XSW), scanning tunneling microscopy measurements, in conjunction with theoretical modeling. average carbon bonding distances for PEN PFP differ strongly, that is, 2.34 A versus 2.98 PFP. An adsorption-induced nonplanar conformation of is suggested by XSW (F atoms 0.1 above the plane), which causes an intramolecular dipole...
The growth of high-quality thin films is a key issue in the ability to design electronic devices based on organic materials and tune their properties. In this context, interfaces between metals play decisive role. Here, we report interface formation copper-phthalocyanine (CuPc) an Ag(111) surface using various complementary methods. High-resolution low-energy electron diffraction revealed rich phase diagram for system with disordered (two-dimensional (2D)-gas-like) ordered structures...
We have observed anisotropic flux pinning and resistivity in the substrate plane of YBa${}_{2}$Cu${}_{3}$O${}_{7\ensuremath{-}\ensuremath{\delta}}$ (YBCO) thin films grown on vicinal SrTiO${}_{3}$(001) with $c$ axis oriented along SrTiO${}_{3}$ [001] direction. Using UHV scanning tunneling microscopy transmission electron we demonstrate influence a periodic nanoscale step structure clean surface morphology defect microstructure subsequently deposited YBCO films. A linear array dislocations...
Metal-organic interfaces based on copper-phthalocyanine monolayers are studied in dependence of the metal substrate (Au versus Cu), its symmetry [hexagonal (111) surfaces fourfold (100) surfaces], as well donor or acceptor semiconducting character associated with nonfluorinated perfluorinated molecules, respectively. Comparison properties these systematically varied metal-organic provides new insight into effect each previously mentioned parameters molecule-substrate interactions.
We study the adsorption geometry of 3,4,9,10-perylene tetracarboxylic dianhydride on Ag(111) and Cu(111) using x-ray standing waves. The element-specific analysis shows that carbon core molecule adsorbs in a planar configuration, whereas oxygen atoms experience nontrivial substrate dependent distortion. On copper (silver) ring resides $2.66\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ $(2.86\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}})$ above substrate. In contrast to conformation Ag(111), where...
The structural chemistry and reactivity of 1,3,8,10-tetraazaperopyrene (TAPP) on Cu(111) under ultra-high-vacuum (UHV) conditions has been studied by a combination experimental techniques (scanning tunneling microscopy (STM) X-ray photoelectron spectroscopy, XPS) DFT calculations. Depending the deposition conditions, TAPP forms three main assemblies, which result from initial submonolayer coverages based different intermolecular interactions: close-packed assembly similar to projection bulk...
Atomic-layer 2D crystals have unique properties that can be significantly modified through interaction with an underlying support. For epitaxial graphene on SiC(0001), the interface strongly influences electronic of overlaying graphene. We demonstrate a novel combination x-ray scattering and spectroscopy for studying complexities such buried structure. This approach employs standing wave-excited photoelectron in conjunction reflectivity to produce highly resolved chemically sensitive atomic...
We present the atomic structure of c(8 x 2) reconstructions InSb-, InAs-, and GaAs-(001) surfaces as determined by surface x-ray diffraction using direct methods. Contrary to common belief, group III dimers are not prominent on surface, instead subsurface dimerization atoms takes place in second bilayer, accompanied a major rearrangement above form linear arrays. By varying occupancies four sites (001)-c(8 III-V semiconductors can be described unified model.
The adsorption geometry of perfluorinated copper-phthalocyanine molecules $({\mathrm{F}}_{16}\mathrm{CuPc})$ on Cu(111) and Ag(111) is studied using x-ray standing waves. A detailed, element-specific analysis taking into account nondipolar corrections to the photoelectron yield shows that both surfaces adsorb in a lying down, but significantly distorted configuration. While copper (silver) central carbon rings reside 2.61 \AA{} (3.25 \AA{}) above substrate, outer fluorine atoms are located...
We performed optical absorption and temperature-dependent extended x-ray-absorption fine-structure (EXAFS) measurements on 55-atom gold clusters made by the Schmid process. The results are consistent with a fcc cuboctahedron structure, but first-neighbor distances contracted 0.075 \AA{}. electronic properties, as detected x-ray absorption, expected for small chunk of gold. EXAFS Debye-Waller factor shows that have 40% less thermal vibration than does bulk. present theory this effect, based...
The position of gallium atoms on a silicon (111) surface has been completely determined using the tunneling microscope and x-ray standing-wave methods. (\ensuremath{\surd}3 \ifmmode\times\else\texttimes\fi{} \ensuremath{\surd}3 )R30\ifmmode^\circ\else\textdegree\fi{} electron diffraction pattern observed with (1/3-monolayer coverages is shown to result from simple adatom lattice adatoms at distance 1.49 A\r{} above bulk extrapolated plane filled threefold sites. Total-energy calculations...
With use of x-ray standing waves in UHV and synchrotron radiation, the early stages growth ${\mathrm{CaF}}_{2}$ on Si(111) were investigated. A new subtle arrangement Si(111)/${\mathrm{CaF}}_{2}$ interface emerges from this study. For deposition at high substrate temperatures, first monolayer dissociates, CaF is formed surface with Ca ${\mathit{T}}_{4}$ ${\mathit{H}}_{3}$ sites. At lower temperature, a larger fraction remains undissociated, third site sevenfold F coordinated addition to...
Surface x-ray diffraction has been employed to elucidate the surface structure of $(011)\ensuremath{-}(2\ifmmode\times\else\texttimes\fi{}1)$ termination rutile ${\mathrm{TiO}}_{2}$. The data are inconsistent with previously proposed structures. Instead, an entirely unanticipated geometry emerges from determination, which is terminated by zigzag rows twofold coordinated oxygen atoms asymmetrically bonded fivefold titanium atoms. energetic stability this demonstrated ab initio total energy...
We present a detailed experimental and theoretical characterization of the adsorption perylene derivative 4,9-diaminoperylene-quinone-3,10-diimine (DPDI) on Cu(111) compare it to its threefold dehydrogenated 3deh-DPDI, which forms in surface reaction upon annealing. While DPDI itself does not give rise long-range ordered structures due lack appropriate functional groups, 3deh-DPDI acts as an exoligand Cu-coordinated honeycomb network Cu(111). The main focus this work lies analysis...