Thermoelectric devices offer a simple and reliable means to convert radioisotope thermal energy into useable electrical power. Present thermoelectric devices based on bulk materials are limited by low conversion efficiencies, due to fundamental limitation of identifying materials with both a high electrical conductivity and low thermal conductivity. Nanowires provides a means to circumvent this limitation, and achieve combinations of properties not possible with bulk materials. To accomplish this task, SMI will demonstrate the formation of nanocomposite structures in a SiGe matrix by gas flow hollow cathode (GFHC) sputtering creating high ZT for the GFHC sputter deposited solid state nanocomposite thermoelectric materials. The potential for high deposition rate, and thick films for the solid state nanocomposite materials, on a range of substrates, by GFHC sputtering will be investigated and demonstated, along with a pathway forward to development of a high efficiency TE power conversion system prototype in Phase II.