Nanostructured SiGe thin films obtained through MIC processing

Silicon-germanium (SiGe) alloys are a well-known classic thermoelectric material used for high temperature applications. Recent thermoelectric research on SiGe alloys often focuses on a nanostructuring approach trying to increase its efficiency. This can be achieved by the introduction of grain boundaries and point defects, which effectively increase the scattering rate of phonons and thus reduce the lattice thermal conductivity. In this work, we present an approach to produce nanograinedSiGe thin films by means of sputter deposition and utilizing the effect of metal induced crystallization in a post annealing step. Samples were prepared in the form of Al/SiGemultilayers enabling control over both the lowered crystallization temperature and crystallite size of the SiGe by adjusting the Al interlayer thickness. Since parts of the Al are incorporated into the SiGe during crystallization, no additional efforts have to be made to reach sufficient doping levels. The microstructure of the samples was characterized using transmission electron microscopy, secondary neutral mass spectrometry, and x-ray diffraction. Measured transport properties include specific electrical resistance, Seebeck coefficient, and Hall carrier concentration.