Isotopically enriched silicon heterostructures and its thermoelectric properties

• Applicants: Professor Dr. Georg Bastian; Professor Dr. Hartmut Bracht
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2011 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 185181740

In the framework of this research project we will perform proof-of-principle investigations of silicon isotope superlattice structures for thermoelectric applications. Undoped and homogenously p- and n-type doped isotopically enriched silicon multilayer structures will be grown by means of molecular beam epitaxy. The epitaxial quality will be determined with high resolution transmission electron microscopy. Depth profiling of the isotope structure before and after thermal treatments yields information about possible transient diffusion effects and thus about the structure thermal stability. The electrical properties will be characterized with van-de Pauw and Hall Effect measurements. Thermal properties such as the heat capacity, thermal conductivity and diffusivity will be measured with a physical property measurements system and a laser flash technique. In collaboration with external groups the lateral homogeneity of the Seebeck-coefficient will be mapped with a potential-Seebeck-probe technique and the lattice dynamics of the the optically excited isotope superlattice is investigated with time-resolved x-ray scattering. Finally, thermoelectric modules consisting of n- and p-type silicon with and without an isotope superlattice will be fabricated to test the overall gain of isotope superlattices for thermoelectric materials. Various theoretical investigations will accompany our experiments to better understand the thermal properties of the isotope superlattice.

• DFG Programme: Research Grants