Thin film based thermoelectric energy conversion systems

Up to now thermoelectric materials used in commercial energy conversion devices like infrared sensors, Peltier-coolers or thermogenerators do not take advantage of the enormous potentials provided by low-dimensional structures. The scope of this presentation is the experimental verification of the predicted increase of the thermoelectric figure of merit (FOM) ZT in low-dimensional systems above values of bulk materials. Concepts for the realization of devices using low dimensional structures based on the classical thermoelectric materials (V-VI-compounds for temperatures around 300 K and IV-VI-materials for temperatures up to 600 K, silicides for high temperature applications) were made. We will present briefly the preparation and thermoelectric properties of IV-VI and V-VI superlattice (SL) structures grown by molecular beam epitaxy as well as on Si-Ge SL structures grown by magnetron sputter epitaxy. An important part is the theoretical modeling of these new thin film devices. The results were used to determine the best suited geometrical dimensions and to compare the calculated device performance with the experimental results. Further more, the results will be discussed with respect to the rising industrial interest in high performance thermoelectric thin and thick film devices.