ABSTRACT
We discuss theoretical models for the analysis of the thermal conductivity in thin films. Crucial features of thin films in regard of the thermal transport properties are their polycrystalline structure and small film thickness. These imperfections lead to additional charge carrier and phonon scattering processes, which are not present in monocrystalline bulk materials. We analyze the influence of grain boundary and surface scattering of electrons and phonons on the thermal conductivity. For thin metal films the theoretical validity of the Wiedemann-Franz law is discussed in the framework of the Fuchs-Sondheimer and Mayadas-Shatzkes scattering models. Experimental results of thin Aluminium films are compared with the theoretical investigations. For two-band semimetal films like Bismuth and Antimony we demonstrate, how the several components of the thermal conductivity can be determined. The dependence of the charge carrier contribution, the bipolar and the lattice thermal conductivity on thickness and grain size is analyzed. A model of the lattice thermal conductivity of polycrystalline films based on phonon grain boundary and surface scattering is presented and compared with experimental results of Antimony and Bismuth films.
