A5037891733- Semiconductor Quantum Structures and Devices
- Chalcogenide Semiconductor Thin Films
- Quantum Dots Synthesis And Properties
- Advanced Semiconductor Detectors and Materials
- Semiconductor materials and devices
- Quantum and electron transport phenomena
- Semiconductor materials and interfaces
- ZnO doping and properties
- Electronic and Structural Properties of Oxides
- Surface and Thin Film Phenomena
- Multiferroics and related materials
- Magnetic and transport properties of perovskites and related materials
- Nanowire Synthesis and Applications
- Semiconductor Lasers and Optical Devices
- Copper-based nanomaterials and applications
- Spectroscopy and Quantum Chemical Studies
- Advanced Chemical Physics Studies
- Organic Electronics and Photovoltaics
- Phase-change materials and chalcogenides
- Advancements in Semiconductor Devices and Circuit Design
- Magnetic properties of thin films
- Thin-Film Transistor Technologies
- Solid-state spectroscopy and crystallography
- Silicon Nanostructures and Photoluminescence
- Ion-surface interactions and analysis
University of Würzburg
2010-2020
Leibniz Institute for Analytical Sciences - ISAS
2012
RWTH Aachen University
1991-2007
FH Aachen
1995-2002
Technische Universität Berlin
1989-1994
Westfälische Hochschule
1984-1991
IBM Research - Zurich
1987-1989
An investigation into the stability of metal-insulator-semiconductor (MIS) transistors based on α-sexithiophene is reported. In particular, kinetics threshold voltage shift upon application a gate bias has been determined. The follow stretched-hyperbola-type behavior, in agreement with formalism developed to explain metastability amorphous-silicon thin-film transistors. Using this model, quantification device possible. Temperature-dependent measurements show that there are two processes...
Abstract The lattice parameters of the hexagonal unit cell, atomic parameters, and shift Raman active vibrations are measured p‐Bi 2 Te 3 under uniaxial hydrostatic pressure. structural investigations performed by neutron diffraction, studied scattering. results diffraction experiments constitute a direct experimental confirmation weak bonding between sandwiches in this narrow gap semiconductor with sandwich structure. As consequence, some phonon modes show rather strong dependence upon...
We provide an experimental evidence and a theoretical substantiation for strong reduction of the $s\ensuremath{-}d$ exchange interaction between electrons Mn-ion spins with increasing degree confinement in nanostructures diluted magnetic semiconductors. By spin-flip Raman scattering (up to $25%$) parameter is observed $(\mathrm{Cd},\mathrm{Mn})\mathrm{Te}/(\mathrm{Cd},\mathrm{Mn},\mathrm{Mg})\mathrm{Te}$ quantum well structures. As responsible mechanism we suggest switching-on kinetic...
We present a systematic analysis of the structural properties Mn implanted ZnO by Raman scattering and complementary methods in composition range 0.2–8 at.% (relative to Zn) with an implantation step profile about 300 nm depth. ions are substitutionally incorporated on Zn sites wurtzite lattice no secondary phases detected. Beside common eigenmodes host lattice, we observe additional modes related implantation, which studied for different concentrations annealing procedures. distinguish...
Vibrations of Sb on (110) surfacesof III-V semiconductors (InP,GaAs,GaP) were investigated by Raman scattering from the submonolayer range up to a few monolayers. Interface phonons, involving epitaxial first monolayer and upper substrate layer, are observed. They clearly identified their coverage dependence. The peaks most pronounced for InP. fulfill polarization selection rules chains along (11\ifmmode\bar\else\textasciimacron\fi{}0). Moreover, they reveal that thicker coverages structure...
We have fabricated organic thin-film transistors (OTFTs) using a microcontact printing technique (μCP) that employs thin polydimethylsiloxane stamps on rigid silicon substrate in order to reduce macroscopic distortions. Systematic variation of the pressure, time, and concentration eicosanethiol, “molecular ink” μCP process, permits fabrication devices with smaller channel lengths (Leff) than nominally defined by stamp. Interdigitated Ti/Au electrode structures Leff down 100 nm could be...
The formation of a thin interfacial layer indium telluride in InSb-CdTe heterostructures has been previously suggested by soft x-ray photoemission (SXPS) results. However, the detailed nature this was difficult to interpret SXPS. Therefore, samples being investigated SXPS were studied Raman spectroscopy. Spectra taken grown deposition CdTe on (100) InSb substrates at room and elevated temperatures. For room-temperature sample vibrational modes crystalline Te detected. In case substrate...
With micro-Raman spectroscopy and x-ray diffraction (XRD), we studied ZnO crystals implanted with Mn, Fe, Co, Ni, respectively, implantation concentrations from 4 up to 16 at. %. Using thermal treatments in air 700 °C, analyzed the annealing effect on crystal lattice as well onset of secondary phases their microstructure sample surface. While 500 °C treatment induces a considerable annealing, are observed for transition metal (TM) ≥8 % after at °C. Their strongly depends TM species. Various...
Be-chalcogenides take a special place among II–VI compounds due to their expected reduced polarity. We report on an investigation of the phonon properties and dielectric constants BeSe BeTe by far- mid-infrared reflectance Raman spectroscopy. For comparison with our experimental results we performed first-principles calculations (LDA) obtain charge distribution TO-phonon frequencies within frozen approximation. From spectroscopic data derive bond polarities, which are distinctly respect...
In this paper it is demonstrated that Raman spectroscopy can be used for in situ online monitoring of semiconductor layer growth. For purpose an ultra-high-vacuum chamber was designed to suit molecular beam epitaxial growth as well simultaneous optical measurements utilizing a multichannel detection system. As result spectra taken while progresses. shown by the example InSb growth, they provide information on interface chemistry, crystal quality growing layer, and mode well.
The excitations of a two-dimensional electron gas in quantum wells with intermediate carrier density (${n}_{e}\ensuremath{\sim}{10}^{11}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}2}$), i.e., between the exciton-trion and Fermi-sea range, are so far poorly understood. We report on an approach to bridge this gap by magnetophotoluminescence study modulation-doped (Cd,Mn)Te well structures. Employing their enhanced spin splitting, we analyzed characteristic magnetic-field behavior individual...
The structural and optical properties of thin lead oxide films were studied. Thin prepared by reactive dc magnetron sputtering (Pb) targets in an Ar/O2 mixture. structure has been determined x-ray diffraction measurements, which show that crystalline different composition (PbO, PbO1.44, Pb2O3, PbO2) have formed upon increasing oxygen flow (partial pressure). This result is confirmed Raman spectroscopy. effect postdeposition annealing on the PbO reveals film governed both energetics kinetics....
We have studied the surface phonon modes of reconstructed Si(111)-($7\ifmmode\times\else\texttimes\fi{}7$) by polarized Raman spectroscopy. Six vibration are observed in frequency range between 62.5 and 420.0 cm${}^{\ensuremath{-}1}$. The mode frequencies agree very well with reported calculation results. This enables their attribution to calculated eigenmodes, whose elongation patterns dominated specific atomic sites: two most characteristic novel fingerprints...