A5036348963- Silicon and Solar Cell Technologies
- Semiconductor materials and interfaces
- Integrated Circuits and Semiconductor Failure Analysis
- Silicon Nanostructures and Photoluminescence
- Semiconductor materials and devices
- Thin-Film Transistor Technologies
- Electron and X-Ray Spectroscopy Techniques
- GaN-based semiconductor devices and materials
- Magnetic properties of thin films
- Ion-surface interactions and analysis
- Magnetic and transport properties of perovskites and related materials
- Advanced Electron Microscopy Techniques and Applications
- Surface and Thin Film Phenomena
- ZnO doping and properties
- Ga2O3 and related materials
- Semiconductor Quantum Structures and Devices
- Diamond and Carbon-based Materials Research
- Electronic and Structural Properties of Oxides
- Metallic Glasses and Amorphous Alloys
- Metal and Thin Film Mechanics
- Nanowire Synthesis and Applications
- Chalcogenide Semiconductor Thin Films
- Force Microscopy Techniques and Applications
- Quantum and electron transport phenomena
- Microstructure and mechanical properties
University of Göttingen
2015-2025
Technical University of Munich
2019-2022
Max Planck Institute for Plasma Physics
2017-2019
St Petersburg University
2018
Institute of Physics
2018
Max Planck Society
2018
Dassault Systèmes (Germany)
2013-2016
Universitätsmedizin Göttingen
1995-2015
Czech Academy of Sciences, Institute of Physics
2015
Clausthal University of Technology
2013
Using aluminum oxide (Al2O3) films deposited by atomic layer deposition (ALD), the dominant passivation mechanisms at c-Si/Al2O3 interface, as well chemical composition of interface region, are investigated. The excellent surface quality thin Al2O3 is predominantly assigned to a high negative fixed charge density Qf = − (4 ± 1) × 1012 cm−2, which located within 1nm Si/Al2O3 and independent thickness. A deterioration for ultrathin layers explained strong increase in state density, presumably...
Inorganic carbon nanomaterials, also called nanodots, exhibit a strong photoluminescence with unusual properties and, thus, have been the focus of intense research. Nonetheless, origin their is still unclear and subject scientific debates. Here, we present single particle comprehensive study nanodot photoluminescence, which combines emission lifetime spectroscopy, defocused dipole imaging, azimuthally polarized excitation scanning, nanocavity-based quantum yield measurements, high resolution...
The atomic process, kinetics, and equilibrium thermodynamics underlying the gettering of transition-metal impurities in Si are reviewed. Methods for mathematical modeling discussed illustrated. Needs further research considered.
We demonstrate electroluminescence (EL) with an external efficiency of more than 0.1% at room temperature from glide dislocations in silicon. The key to this achievement is a considerable reduction nonradiative carrier recombination due impurities and core defects by impurity gettering hydrogen passivation, respectively, which shown means deep-level transient spectroscopy. Time-resolved EL measurements reveal response time below 1.8 μs, much faster, compared the band-to-band luminescence bulk
We show that electronic states at extended defects in semiconductors can be classified as bandlike or localized using deep-level transient spectroscopy (DLTS), when electron equilibration the defect is taken into account. compare computer simulations of DLTS with data for 60\ifmmode^\circ\else\textdegree\fi{} dislocations and ${\mathrm{NiSi}}_{2}$ platelets silicon find narrow point clouds first a two-dimensional metal ring second example.
The defects leading to haze formation after diffusion of the transition metals cobalt, nickel, copper, and palladium have been studied by means transmission electron microscopy preferential etching. In all cases crystalline metal silicide particles observed. Both cobalt nickel form disilicide different morphologies in surface regions silicon wafers, whereas copper metal-rich causing a supersaturation Si self-interstitials or undersaturation vacancies extrinsic dislocation loops.
We describe how general lattice images may be used to measure the variation of potential in crystalline solids any projection, with no knowledge imaging conditions. This approach is applicable structurally perfect samples, which interfacial topography or changes composition are interest. present first atomic-level topographic map a Si/${\mathrm{SiO}}_{2}$ interface plan view, and microscopic compositional Si/GeSi/Si quantum well cross section.
Oxygen vacancies in the MgO barriers of epitaxial $\mathrm{Fe}/\mathrm{MgO}/\mathrm{Fe}$ magnetic tunnel junctions are observed to introduce symmetry-breaking scatterings and hence open up channels for noncoherent tunneling processes that follow normal WKB approximation. The evanescent waves inside barrier thus experience two-step tunneling, coherent followed by process, lead lower magnetoresistance, higher junction resistance, as well increased bias temperature dependence. characteristic...
Organic compounds isolated from diatoms contain long-chain polyamines with a propylamine backbone and variable methylation levels chain lengths. These are thought to be one of the important classes molecules that responsible for formation hierarchically structured silica-based cell walls diatoms. Here we describe synthetic route based on solid-phase peptide synthesis which well-defined different lengths, patterns, subunits can obtained. Quantitative silica precipitation experiments together...
Predominant dislocation types in solar silicon are dissociated into 30°- and 90°-partials with reconstructed cores. Besides shallow 1D-band localized their strain field a quasi-2D band at the stacking fault connecting two partials, existence of several intrinsic core defects deep lying levels has been demonstrated by electron spin resonance. The majority occur nonequilibrium situations and, exception small EPR-signal assigned to reconstruction defect, vanish after careful annealing above...
Copper‐silicide precipitates in silicon obtained after copper diffusion and quench different liquids were studied by transmission electron microscopy capacitance spectroscopy techniques. A correlation between the quenching rate, geometric size, deep level spectra of copper‐silicide was established. The unusually wide are shown to be due a defect‐related band bandgap. parameters evaluated using numerical simulations. positive charge p‐type moderately doped n‐type Si is predicted simulations...
Tetrapod zinc oxide (T-ZnO) nanorods have been synthesized by evaporation and recondensation of metallic Zn under ambient conditions. The total sizes the T-ZnO nanostructures range from 300nmto15μm with leg diameters about 30to650nm, depending on deposition temperature. A detailed high-resolution electron microscopy analysis showed that center core consists four hexagonal grains a twinlike relation. nucleation growth mechanism has generated basis energy considerations during phase transition...
We report a combination of analytical transmission electron microscopy, small angle neutron scattering, and studies magnetic properties the glass-forming alloy Nd60Fe30Al10. These investigations show existence an in situ formed finely dispersed nanocrystalline Nd-rich phase embedded Fe-rich glassy matrix bulk sample. The crystalline forms extended network over whole sample but its volume fraction is compared to that compact phase. Small scattering data exhibit power law behavior with...
Abstract The precipitation behaviour of nickel in silicon after rapid cooling (at about 103 Ks−1) from high temperatures (850-850°C) has been studied using high-resolution transmission electron microscopy. It is shown that (1) coherent platelets on Si{111} planes are formed, which consist two {111} layers NiSi2 and (2) the precipitate-matrix interface built up by Si-Si bonds. proposed these precipitates, all atoms have a deficient coordination, formed as compromise to maximize energy...
Ferroelectricity in ZnO is an unlikely physical phenomenon. Here, we show ferroelectricity undoped [001] nanorods due to zinc vacancies. Generation of a nanorod effectively increases its piezoelectricity and turns the into ultrahigh-piezoelectric material. Here using piezoelectric force microscopy (PFM), it observed that increasing frequency AC excitation electric field decreases effective d33. Subsequently, existence reversible permanent dipole also found from P–E hysteresis loop nanorods....
Abstract Despite significant advancements in materials design for renewable energy devices, the fundamental understanding of underlying processes many remains limited, particularly complex, inhomogeneous systems and interfaces. In such cases, situ studies with high spatial resolution are essential uncovering new insights into excitation, dissipation, conversion processes. Recent progress atomic scale methods has greatly enhanced materials. Here, key advances reviewed, including situ,...
We report results of a detailed study structural and electrical properties copper silicide precipitates in silicon. Using conventional high-resolution transmission electron microscopy we observe that metastable platelets surrounded by extrinsic stacking faults form upon quenching from high temperatures. By ripening experiments at low temperatures as well variation cooling rates it is shown how homogeneous precipitation merges into the heterogeneous mode colony growth. The application...
We report first results on the recombination properties of structurally well defined NiSi2 precipitates in n-type silicon. Under conditions applied, form without occurrence punched out dislocations or any other secondary defects. find that minority-carrier diffusion length (LD) measured by electron beam induced current (EBIC) is related to precipitate density NV and LD ≂ 0.7 × NV−1/3. EBIC investigations individual reveal contrasts up 40% demonstrating particles be efficient centers.
Abstract We investigated correlation between concentration of deep level defects at dislocations, detected by transient spectroscopy (DLTS) and the efficiency dislocation related luminescence in Si samples with density about (3–5) × 10 8 cm –2 . show that significant reduction states dislocations achieved using combination gettering passivation, results a drastic (by several orders magnitude) increase dislocation‐related D1 high temperature range. As consequence, electroluminescence (EL)...