Structure and thermoelectric properties of nano-crystalline Rex-Si1-x thin film composites

In this report results on phase formation and transport properties of amorphous and nano-crystalline Re-Si thin films are presented. The results imply that the partially crystallized Re-Si films, i.e. films consisting of amorphous and nano-crystalline phases form a new class of heterostructures which are essentially different from binary insulator-metal mixtures. We have found that the resistivity and thermopower of the heterogeneous films consisting of amorphous and nano-crystalline phases do not follow the well known effective medium approximation when the ratio between these two phases is varied. Both phase composition and crystalline grain size appear to be important parameters for the thermoelectric material optimization.