Electronic Material Properties - und Geowissenschaften ...

Theoretical Materials Science
Teaching by this division addresses the atomistic foundations of materials science,
including the concepts underlying their representation, from the theoretical physics point of
view. Research focuses on materials modelling, being a powerful tool for materials
development. Experimental results will be understood, and predictions of further
observations given, in the light of theoretical evidence, both to aid the optimization of the
properties or the performance of materials already in use and to guide the design of novel
materials with properties, or behaviour, required in future engineering applications.
Current investigations centre on the following classes of materials:
Transition metals and related alloys
For this class of materials, represented by Ta and Fe or, respectively, steels, the goal is
examining their suitability for structural components of high-power spallation neutron
sources that are exposed to intense proton beams. Irradiation-induced hydrogen
production under the operating conditions of the envisaged European spallation source is
predicted to generate high internal concentrations of atomic hydrogen which, further
enhanced by stress-driven hydrogen accumulation near microstructural cracks, may lead
to a severe degradation of the mechanical properties of steel, whereas no noticeable
deterioration is to be expected in the case of tantalum.
High-temperature superconductors
For this class of materials, typified by YBa2Cu3O7 and Bi2Sr2Ca2Cu3O10 in thin-film or bulk
form, great interest is directed towards investigating extended defects (e.g. low-angle grain
and twin boundaries) which are considered as weak-links between superconducting grains.
There are two principal aims: (i) exploring the connection between the electromagnetic
response (e.g. the current-voltage relation) and the characteristic defect morphology so as
to obtain insight into constitutive parameters of superconducting films; (ii) searching for
possibilities to improve the current-carrying capability of superconducting materials, which
is limited by the above-mentioned types of defect. Preliminary studies of novel
heterostructures involving superconductor strips with a single grain boundary defect,
placed in open magnetic cavities, show that magnetic shielding here is a promising way
forward. Another field of research addresses the interaction between electromagnetic
radiation and multilayered heterostructures made up of superconductors as well as a range
of different classes of materials with a view to examining their suitability for novel photonic
crystals. Of special interest are materials whose properties can be controlled by external
parameters and fields.
Organic semiconductors
For this class of materials, represented by Alq3, emphasis is placed on real-time modelling
of the charge transfer by injected carriers and on a theoretical analysis of thermally
stimulated luminescence phenomena with the aim of extracting, in conjunction with
experiments, information about the electronic structure of inherent traps so as to assist
technological exploitation and further materials development. Some of the most important
features to be taken into account hereby are the field-dependence of the mobilities of the
charge carriers addressed as well as the field- and temperature dependences of the
injection barriers present, apart from allowing for the variation of the distribution of traps in
space and depth.
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