Projects

individual nanowires, electrical conductivity, thermal conductivity and Seebeck coefficient. Based on these data the figure of merit ZT of single nanowires will be determined. The core of the project is the development of a measurement platform with integrated heaters and thermal couples based on MEMS technology which can be applied for low-temperature measurements and investigations in the transmission electron microscopes. The individual nanowire will be placed on the predefined MEMS platform, where the local electrical connection between nanowire and platform is performed by CVD based e-beam lithography. In the final project stage both, thermoelectric and crystallographic information will be gathered from individual nanowires for a comprehensive physical analysis. Parallel to the platform developments and as a reference we will perform physical measurement on specific thermoelectric properties, e.g. Seebeck coefficient by contacting single nanowires via e-beam and optical lithography. As a Bi2Te3-like model system single crystalline Sb2Te3 will be grown in vapor liquid solid mode by a sequential chemical vapor deposition process. Two complementary approaches will be investigated for the doping of the Sb2Te3 with bismuth and other elements. The following physical questions will be investigated on individual nanowires in the course of the project: (1) The influence of the nanowire diameter on the electrical conductivity and ZT, (2) the effect of nanowire doping on the Seebeck coefficient, electrical conductivity and ZT. (3) Multi-segmented Sb2Te3/Sb2(S/Se)3 nanowires will be developed for interdiffusion studies of the Se/S- and Te-rich segments during annealing. The project goal will be a data correlation between the thermoelectric measurements and advanced TEM analysis from single wires and theoretic simulations.