A5047899572- Semiconductor Quantum Structures and Devices
- ZnO doping and properties
- Quantum Dots Synthesis And Properties
- Semiconductor materials and devices
- GaN-based semiconductor devices and materials
- Quantum and electron transport phenomena
- Chalcogenide Semiconductor Thin Films
- Plasma Diagnostics and Applications
- Gas Sensing Nanomaterials and Sensors
- Copper-based nanomaterials and applications
- Ga2O3 and related materials
- Advanced Thermoelectric Materials and Devices
- Transition Metal Oxide Nanomaterials
- Electronic and Structural Properties of Oxides
- Electrohydrodynamics and Fluid Dynamics
- Magnetic properties of thin films
- Magnetic and transport properties of perovskites and related materials
- Semiconductor Lasers and Optical Devices
- Mesoporous Materials and Catalysis
- Advanced Semiconductor Detectors and Materials
- Advancements in Semiconductor Devices and Circuit Design
- Thermal properties of materials
- Nanowire Synthesis and Applications
- Photonic and Optical Devices
- Thermal Radiation and Cooling Technologies
Justus-Liebig-Universität Gießen
2015-2024
Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)
2022-2024
Giessen School of Theology
2014-2024
Institute of Experimental Physics of the Slovak Academy of Sciences
2014-2021
Leibniz-Institut für Wissensmedien
2015
Philipps University of Marburg
2000-2009
University of Augsburg
2003-2008
Heriot-Watt University
2008
Sapienza University of Rome
2004-2007
National Interuniversity Consortium for the Physical Sciences of Matter
2006-2007
Abstract Copper‐oxide compound semiconductors provide a unique possibility to tune the optical and electronic properties from insulating metallic conduction, bandgap energies of 2.1 eV infrared at 1.40 eV, i.e., right into middle efficiency maximum for solar‐cell applications. Three distinctly different phases, Cu 2 O, 4 O 3 , CuO, this binary semiconductor can be prepared by thin‐film deposition techniques, which differ in oxidation state copper. Their material as far they are known...
We study the transformation from molecular to crystalline of (non-)graphitic carbons synthesized organic precursors by heat-treatment. Easy assessment structural properties resulting heat-treatment protocols is mandatory for industrial process monitoring. demonstrate that Raman spectroscopy, in particular, lineshape analysis G and D mode, offers quick average sheet size such carbons. validate this method performing Raman, WAXS EPR measurements series resin pitch-based synthesized. The...
Rapid evolution of miniaturized, automatic, robotized, function-centered devices has redefined space technology, bringing closer the realization most ambitious interplanetary missions and intense near-Earth exploration. Small unmanned satellites probes are now being launched in hundreds at a time, resurrecting dream satellite constellations, i.e., wide, all-covering networks small capable forming universal multifunctional, intelligent platforms for global communication, navigation,...
Various ultrathin planar optical elements, including cylindrical lens, spherical and phase holograms, are designed based on the interface modulation of antenna resonances in terahertz (THz) range. The focusing imaging performance lenses image‐reconstruction ability pure holograms demonstrated experimentally. In contrast to conventional bulky elements where curve surfaces used control light propagation, manipulations propagation for these thin achieved through arrays complementary V‐shaped...
The transition from old space to new along with increasing commercialization has a major impact on flight, in general, and electric propulsion (EP) by ion thrusters, particular. Ion thrusters are nowadays used as primary systems space. This article describes how these changes related affect various aspects that important for the development of EP systems. Starting historical overview flight technology systems, number missions underlying technologies presented. focus our discussion is radio...
The injection of spin-polarized electrons is presently one the major challenges in semiconductor spin electronics. We propose and demonstrate a most efficient using diluted magnetic semiconductors as aligners. Time-resolved photoluminescence with Cd0.98Mn0.02Te/CdTe structure proves feasibility spin-alignment mechanism.
An intrinsic property of quaternary alloys ${A}_{1\ensuremath{-}y}{B}_{y}{C}_{1\ensuremath{-}x}{D}_{x} (x\ensuremath{\approx}1--3%)$ with D being an isovalent trap is reported: a set discrete band gaps occurs due to substitution the on sites different nearest-neighbor environments. Exemplary, this phenomenon demonstrated for (Ga,In)(N,As) by experiment and explained tight-binding supercell calculations. The gap nitrogen-poor alloy blueshifted simply moving nitrogen traps from Ga-ligand rich...
Metastable $ϵ$-gallium oxide is expected to have very good properties for high-power electronics, combining the large band gap and high breakdown field of $\ensuremath{\beta}$-Ga${}_{2}$O${}_{3}$ with a spontaneous polarization. Unfortunately, synthesizing $ϵ$-Ga${}_{2}$O${}_{3}$ quite tricky, yet authors managed it. Introducing tin avoids formation volatile suboxides, which leadsto widened growth window in can beformed. Furthermore, mechanism that revealcould be relevant any binary oxide.
Lithium peroxide (Li2O2), the solid and intrinsically electronic insulating discharge product of Li-O2 batteries strongly influences charge kinetics. In a series experiments, we investigated growth Li2O2 upon corresponding reduction oxidation processes by varying depth discharge. The results indicate that particles with disc-like shape were formed during initial stage. Afterward, nucleation resulted in formation conducting shells. When voltage dropped below 2.65 V, discs evolved to...
The Raman spectrum of crystalline $\mathrm{Cu}{}_{2}\mathrm{O}$ taken off resonance is reproducible and independent the growth method conditions employed. But, in contrast to most other materials, dominated by infrared active silent lattice modes rather than only allowed phonon mode. We show that this unusual behavior likely caused presence copper vacancies so-called split configuration, a point defect particular $\mathrm{Cu}{}_{2}\mathrm{O}$. reduction symmetry due defects may lift...
Smart windows possess the potential to contribute significantly reducing world-wide energy consumption in future. The properties of thermochromic metal oxide VO2 are closest material requirements set by economic considerations for use as an active layer glazings. We show that required parameters can be achieved modifying on atomic level, i.e., simultaneous co-doping with Sr and W cation site. In particular, transition temperature ϑc adjusted range between 15 68 °C varying contents, whereas...
The preparation of carbons for technical applications is typically based on a treatment precursor, which transformed into the carbon phase with desired structural properties. During such material passes through several different stages, example, starting from precursor molecules via an amorphous crystalline-like phases. While structure non-graphitic and graphitic has been well studied, transformation stages molecular to are still not fully understood. Disordered often contains mixture sp3-,...
In an all-solid-state battery, the electrical contact between its individual components is of key relevance in addition to electrochemical stability interfaces. Impedance spectroscopy particularly suited for non-destructive investigation interfaces and their under load. Establishing a valid correlation microscopic processes macroscopic impedance signal, however, challenging prone errors. Here, we use 3D electric network model systematically investigate effect various electrode/sample...
GaN x As 1−x samples with x<3% grown by metalorganic vapor phase epitaxy were studied low-temperature photoluminescence under hydrostatic pressure and photomodulated reflectance spectroscopy. The transformation from N acting as an isoelectronic impurity to N-induced band formation takes place at x≈0.2%. level does not shift respect the valence edge of GaNxAs1−x. Concentration well hydrostatic-pressure dependence GaNxAs1−x bands can be described a three kp description conduction state...
The band-anticrossing (BAC) model has been widely applied to analyse the electronic structure of dilute nitride III-V-N alloys such as GaNxAs1−x. BAC describes strong band gap bowing observed at low N composition in GaNxAs1−x terms an interaction between GaAs host matrix conduction edge and a higher lying localized resonant states. In practice, replacing As by introduces range N-related defect levels, associated with isolated atoms, N–N pairs larger clusters atoms. We show that effect levels...
Engineered metal nanoparticles are increasingly used in consumer products, part as additives that exhibit advantageous antimicrobial properties. Conventional nanoparticle susceptibility testing is based largely on determination of nontemporal growth profiles such measurements inhibition zones common agar diffusion tests, counting colony-forming units, or endpoint regular-interval via optical density measurements. For better evaluation the dynamic effects from exposure to nanoparticles, a...
Although tungsten trioxide (WO3) has been extensively studied since its electrochromic properties were first discovered, the mechanism responsible for coloration or bleaching effect is still disputed. New insights into of electrochromic, nanocrystalline WO3 are provided in this paper by studying thin films combining electrochemical and spectroscopic techniques. By employing situ UV-Vis transmission spectroscopy at a fixed spectral band pass during experiments, such as cyclic voltammetry,...
The existence of an intermediate phase tin oxide was first reported in 1882. However, its stoichiometry and crystal structure have been dubious heavily debated ever since, despite a multitude structural investigations. We show that Raman spectroscopy combined with ab initio theory offers viable alternative for determination cases where diffraction studies are inconclusive. unambiguously identify the as ${\mathrm{Sn}}_{3}{\mathrm{O}}_{4}$ rule out other likely candidate,...
Thin films of doped VO2 were deposited, analyzed, and optimized with regard to their solar energy transmittance (Tsol) visible/luminous light (Tlum) which are important parameters in the context smart window applications buildings. The doping alkaline earth metals (AEM) like Mg, Ca, Sr, or Ba increased both Tsol Tlum due a bandgap widening an associated absorption edge blue-shift. Thereby, brown-yellowish color impression pure thin films, is one major hindrance limiting usage as...
We present a technique for systematically investigating electronic and ionic charge transport in single Li(Ni1/3Co1/3Mn1/3)O2 (NCM 111) secondary particles as function of size. perform electrochemical impedance spectroscopy employing ion-blocking electrodes. Micrometer-sized spherical are arranged cylindrical particle traps on patterned substrate. A specially designed cell is used to contact measure individual immobilized defined geometry. The obtained resistances the size compared with...
A non-ideal contact at the electrode/solid electrolyte interface of a solid-state battery arising due to pores (voids) or inclusions results in geometric constriction effect that severely deteriorates electric transport properties cell. The lack understanding this phenomenon hinders optimization process novel components, such as reversible and high-rate metal anodes. Deeper insight into is necessary correctly monitor degradation accelerate successful use anodes batteries. Here, we 3D network...
Abstract Impedance spectroscopy is widely used in operando studies of solid‐state batteries for characterizing charge transport and correlating it with structural features. A typical impedance spectrum reveals, addition to signals the solid electrolyte, one or more contributions due processes taking place at electrode interfaces. The focus this study on reversible (parent) metal anodes a 3D electric network model analyze variation their as function pressure, temperature, aging during...
The electron effective mass, ${m}_{\mathrm{e}}$, has been determined by magnetophotoluminescence in as-grown and hydrogenated $\mathrm{Ga}{\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{N}}_{x}$ samples for a wide range of nitrogen concentrations (from $x<0.01%$ to $x=1.78%$). A modified $\mathbf{k}\mathbf{∙}\mathbf{p}$ model, which takes into account hybridization effects between N cluster states the conduction band edge, reproduces quantitatively experimental ${m}_{\mathrm{e}}$ values up...
We derive an analytical model to describe the conduction-band states of GaNAs-based quantum well structures, including band anticrossing effect between $N$ resonant and edge. The predictions are compared those obtained using a full ten-band $\mathbf{k}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbf{p}$ based on same set parameters. Both methods then tested by comparison with experimentally determined ground- excited-state interband transition energies...
The first syntheses of highly ordered bifunctional periodic mesoporous organosilicas (PMOs) containing different amounts aromatic thiophene and benzene bridging groups are reported. Employing the triblock copolymer Pluronic P123 as well oligomeric Brij 76 surfactant under acidic conditions supramolecular structure-directing agents, two series PMO materials with pore sizes in range 4.8–5.4 3.3 nm, respectively, have been realized. Independent molar ratios organosilanes initial reaction...