A5030820398- Electron and X-Ray Spectroscopy Techniques
- Surface and Thin Film Phenomena
- Advanced Chemical Physics Studies
- Physics and Engineering Research Articles
- Ion-surface interactions and analysis
- nanoparticles nucleation surface interactions
- X-ray Spectroscopy and Fluorescence Analysis
- Advanced Materials Characterization Techniques
- Semiconductor materials and devices
- Magnetic properties of thin films
- Quantum and electron transport phenomena
- Semiconductor materials and interfaces
- Electronic and Structural Properties of Oxides
- Graphene research and applications
- Engineering and Materials Science Studies
- Photocathodes and Microchannel Plates
- German Literature and Culture Studies
- Molecular Junctions and Nanostructures
- Machine Learning in Materials Science
- Topological Materials and Phenomena
- Perovskite Materials and Applications
- Advanced Electron Microscopy Techniques and Applications
- Physics of Superconductivity and Magnetism
- Spectroscopy and Quantum Chemical Studies
- Laser-Matter Interactions and Applications
Friedrich-Alexander-Universität Erlangen-Nürnberg
2013-2023
Science and Technology on Surface Physics and Chemistry Laboratory
2020
Osaka University
2011
Max Planck Institute for Plasma Physics
1990-2000
Max Planck Institute of Quantum Optics
1997
Max Planck Society
1988-1996
Ludwig-Maximilians-Universität München
1994-1996
Osnabrück University
1993
University of Würzburg
1979-1986
IBM (United States)
1983-1985
Time-resolved two-photon photoemission in combination with the coherent excitation of several quantum states was used to study ultrafast electron dynamics image-potential on metal surfaces. For a (100) surface copper, spectroscopy beats made previously unresolved high-order (quantum number n ≥ 4) experimentally accessible. By exciting electrons close vacuum level, wave packets could be created and detected that described quasi-classical periodic motion weakly bound electrons. They traveled...
As they combine decent mobilities with extremely long carrier lifetimes, organic-inorganic perovskites have opened a whole new field in opto\-electronics. Measurements of their underlying electronic structure, however, are still lacking. Using angle-resolved photoelectron spectroscopy, we measure the valence band dispersion single-crystal CH$_3$NH$_3$PbBr$_3$. The highest energy is extracted applying modified leading edge method, which accounts for particular density states perovskites....
Metal halide perovskites are the first solution processed semiconductors that can compete in their functionality with conventional semiconductors, such as silicon. Over past several years, perovskite have reported breakthroughs various optoelectronic devices, solar cells, photodetectors, light emitting and memory so on. Until now, face challenges regarding stability, reproducibility, toxicity. In this Roadmap, we combine expertise of chemistry, physics, device engineering from leading...
Photoemission and inverse photoemission (or bremsstrahlung spectroscopy) are shown to be complementary techniques for probing occupied unoccupied electronic states, respectively. The momentum of delocalized valence states can measured as well their energy if low electron (photon) energies in the 10–40 eV range used. Thus, band dispersions obtained bulk, surface, adsorbate which cannot determined by other techniques. A status report is given illustrated results bulk ferromagnets silicides,...
Angle-resolved inverse photoemission with tunable photon energies has been used to map out the unoccupied bands of graphite and lithium-intercalated graphite. At Brillouin zone center bottom lowest band is found at 4.0\ifmmode\pm\else\textpm\fi{}0.5 eV above Fermi level in This shows strong dispersion normal basal plane excellent agreement recent self-consistent band-structure calculations. A similar three-dimensional shifted 3 lower energy.
Long carrier lifetimes and diffusion lengths form the basis for successful application of organic-inorganic perovskite (CH$_3$NH$_3$)PbI$_3$ in solar cells lasers. The mechanism behind long is still not completely understood. Spin-split bands a resulting indirect band gap have been proposed by theory. Using near band-gap left-handed right-handed circularly polarized light we induce photocurrents opposite directions single-crystal device at low temperature ($4~\mathrm{K}$). phenomenom known...
Two-photon photoemission spectroscopy was employed for an investigation of the image states on Pd(111) with various coverages Ag. Image state, from areas different thicknesses Ag layer can be observed simultaneously. This proves applicability concept a local work function. The decay length wave function state Ag(111) into metal determined experimentally to 7.6\ifmmode\pm\else\textpm\fi{}1.2 \AA{}, and probability find electron in is estimated as 10%.
We report time-resolved studies of image-potential states on Cu(100) and Ag(100). Femtosecond ultraviolet-pump infrared-probe techniques combined with two-photon photoemission have been used to measure relaxation dynamics $n=1,$ 2, 3 states. found the lifetimes these at room temperature be $40\ifmmode\pm\else\textpm\fi{}6,120\ifmmode\pm\else\textpm\fi{}15,$ $300\ifmmode\pm\else\textpm\fi{}20\mathrm{fs},$ respectively. The corresponding values for Ag(100) are...
Carrier recombination at the Si(100) c(4 x 2) surface and underlying electronic structure is unraveled by a combination of two-photon photoemission many-body perturbation theory: An electron excited to silicon conduction band femtosecond infrared laser pulse scatters within 220 ps unoccupied band, needs 1.5 jump bottom via emission optical phonons, finally relaxes 5 with an hole in occupied form exciton living for nanoseconds.
The position of the lowest empty orbitals CO and O chemisorbed on Ni(111) have been determined by use inverse photoemission in ultraviolet. $2{\ensuremath{\pi}}^{*}$ orbital is lowered 4.5 eV upon chemisorption broadened to a 5.5-eV-wide resonance centered 3.5 above ${E}_{\mathrm{F}}$. Chemisorbed oxygen has sharp $2{p}_{x,y}$ states at 1.4 ${E}_{\mathrm{F}}$ ${k}_{\ensuremath{\parallel}}=0$ with total density extending from ${E}_{\mathrm{F}}+2$ agreement band calculations. This state...
By use of a generalized Hubbard model, we investigate the influence electron correlations on temperature dependence quasiparticle properties ferromagnetic Ni. The one-particle energies model Hamiltonian are taken from realistic band-structure calculation. contains only two parameters, U and interband exchange J. It is approximately solved by self-consistent moment method. We find ground state, mainly caused uppermost d subband, magnetic at T=0 0.56${\ensuremath{\mu}}_{B}$, Curie...
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 resulting changes in (local) work function. The latter is driven function difference between substrate. This results charge transfer which also contributes to core-level shifts x-ray photoemission. In this review article, we give an overview over theoretical models experimental data...
The Rashba effect is fundamental to the physics of two-dimensional electron systems and underlies a variety spintronic phenomena. It has been proposed that formation Rashba-type spin splittings originates microscopically from existence orbital angular momentum (OAM) in Bloch wave functions. Here, we present detailed experimental evidence for this OAM-based origin by angle-resolved photoemission (ARPES) two-photon experiments monolayer AgTe on Ag(111). Using quantitative low-energy...
The dynamical behavior of image-potential states has been studied with two-photon photoemission for CO on Cu(100). Pure dephasing is observed as the loss coherence in quantum beats, or derived from linewidth and lifetime measurements. A correlation to surface order by low-energy electron diffraction also established.
A vicinal surface of silicon is found that exhibits an atomically accurate step pattern with a period 5.73 nm, corresponding to 17 atomic rows per (111) terrace. It can be viewed as reconstructed Si(557) surface, where triple combined single Si(111)7×7 unit. The driving forces for establishing regular patterns are discussed.
The compositional and structural stability of UHV-grown ultrathin cobalt films on Cu(111) are investigated by low-energy ion scattering. Even at room temperature migration copper substrate atoms onto the film surface diffusion occurs during after deposition process. resulting interface structure therefore depends critically rate as well time measurement. Our findings provide an explanation for controversial results magnetic properties Co/Cu multilayers.
A spectrometer for momentum-resolved and polarization-dependent bremsstrahlung spectroscopy (inverse photoemission) in the vacuum UV range is described performance of apparatus discussed. Seya–Namioka monochromator combined with a position-sensitive channel plate device parallel detection wavelength 165 Å used as photon detector covers an energy regime from 10 to 40 eV resolution 5 Å. Due reflectivity gold-coated gratings, monchromator also inherently analyzer polarization detected light....
Angle-resolved and polarization-dependent uv bremsstrahlung spectroscopy (inverse photoemission) is used to determine the energy symmetry of $2{\ensuremath{\pi}}^{*}$-derived states for CO on Ni(111). We observe a 3-eV-wide band centered at 3 eV above Fermi level. This shows that electron-hole interaction transitions C $1s\ensuremath{\rightarrow}2{\ensuremath{\pi}}^{*}$ reduced from 10 in gas phase 1 chemisorbed due screening by metal electrons. Compared with physisorbed CO, chemisorption...
The unoccupied part of the band structure topological insulators Bi$_2$Te$_{x}$Se$_{3-x}$ ($x=0,2,3$) is studied by angle-resolved two-photon photoemission and density functional theory. For all surfaces linearly-dispersing surface states are found at center Brillouin zone energies around 1.3 eV above Fermi level. Theoretical analysis shows that this feature appears in a spin-orbit-interaction induced inverted local energy gap. This inversion insensitive to variation electronic structural...
Time-resolved two-photon photoemission was used to study the electronic structure and dynamics at surface of ${\text{SnSb}}_{2}$${\text{Te}}_{4}$, a $p$-type topological insulator. The Dirac point is found $0.32\ifmmode\pm\else\textpm\fi{}0.03$ eV above Fermi level. Electrons from conduction band minimum are scattered on time scale $43\ifmmode\pm\else\textpm\fi{}4$ fs cone. From there they decay partly depleted valence with constant $78\ifmmode\pm\else\textpm\fi{}5$ fs. significant...