Preparation and Characterization of Thermoelectric SiGe Thin Films Processed by Al Mediated Metal-Induced Crystallization

In this thesis, a thin film approach to thermoelectric silicon germanium (SiGe) with industrial applicable preparation methods will be presented. Instead of the commonly utilized approach of ball milling and sintering for the production of nanostructured bulk SiGe, the processes of sputter deposition and metal induced crystallization (MIC) were combined to prepare nanocrystalline SiGe thin films. MIC is a process that enables the crystallization of semiconductors like SiGe at temperatures significantly lower than their ordinary crystallization temperature. Aluminum (Al) was used as the catalytic metal for the MIC process. This provided the advantages of a low thermal budget, self-doping (p-type), and control over the crystallization process via parameters like Al thickness, annealing temperature and time. Samples were characterized regarding their morphology, composition, microstructure, and crystallinity comparing the as-deposited and post-annealing state. The results were related to the thermoelectric transport properties of electrical conductivity and Seebeck coefficient. Special emphasis was put on the influence of the Al layer thickness on the MIC process itself and the ratio of Al:SiGe with respect to the transition from metallic to semiconducting transport properties