The project [1] is a continuation on our previous study of hierarchically structured multifunctional bio-composites based on chitin, proteins, and biominerals [2,3] and aims at studying fundamental mechanisms responsible for enhancing mechanical stiffness in these materials. Combining quantum-mechanical calculations in the CM department of Prof. J. Neugebauer and experimental investigation in the MU department of Prof. D. Raabe
Enhancing the brightness of LEDs to meet the increasing demand for energy-efficient high-power light sources requires to go beyond present-day materials' limits. We explore the options for improving p-doping in GaN, a common LED material, by an optimized handling of hydrogen impurities.
Solar cells made from amorphous silicon can be produced cheaply, but their conversion efficiency quickly drops in operation. We collaborate with experimentalists to identify the responsible microscopic processes with EPR.
Due to the lack of lattice and thermal matched substrates, growth of wurtzite GaN films results typically in high threading dislocation (TD) densities. Since the work by Lester et al. [1] there is a large controversial debate regarding the effect dislocations have on the electronic and optical properties of group III-Nitride based devices.
It is often assumed that vibrational contributions to the formation energy are negligible. But is this really true? We investigated this issue for a prototypical defect: the O +2 vacancy in MgO.
Due to a significant red-shift of phonons near the vacancy, not only the zero-point vibrations are reduced by more than 0.1 eV (which normally would be expected only for hydrogen), but also the vibrational entropy increases. Thus, both the zero-point vibrations as well as the finite temperature effect act in favor of defect formation.
For LED lighting industry, the efficiency is never an outdated question. Our project aims to dig out the secrets behind the inefficient performance of GaN based LEDs by using first-principles calculation.
The exceptional optoelectronic properties of ternary group-III nitrides make them a key material for modern solid-state optoelectronic devices. To further improve their optoelectronic properties, a detailed understanding of growth-structure-property relationships is required. Theory and modelling can make a significant contribution. First, we elucidate the growth processes on atomic scale using an effective crystal modelling technique.
Phase change materials are a promising candidate for fast and nonvolatile data storage on computers. We develop models for the switching of the electrical resistivity in such materials, driven by the applications of an electrical current.
