Percolation transition of thermoelectric properties in PbTe thin films

Extrema were observed in the film thickness d dependence of various thermoelectric parameters (Seebeck coefficient S, electrical conductivity sigma, Hall coefficient R-H, charge carrier mobility mu, and power factor P) of epitaxial PbTe/(001) KCl thin films prepared by thermal evaporation in vacuum and protected from oxidation by an EuS layer. We attribute the observed extrema in properties and the high values of mu and P at d approximate to 50 nm to the percolation transition from an island-like to a continuous film and to the self-organization of the islands, which can occur not only in quantum dot superlattices but also in an individual layer. (C) 2001 American Institute of Physics.