80 °C synthesis of thermoelectric nanocrystalline Ge film on flexible plastic substrate by Zn-induced layer exchange

Abstract

Zn-induced layer exchange allowed us to fabricate nanocrystalline Ge on insulators at 80 °C. The Ge layer had a high hole concentration (>1020 cm−3) and was degenerate, leading to a high electrical conductivity (>200 S cm−1). The power factor reached 240 and 160 μW mK−2 for Ge on glass and even flexible plastic substrates, respectively. For the sample with glass, grain boundary phonon scattering reduced the thermal conductivity to 3 W mK−1, which is an order of magnitude smaller than that of bulk Ge. These findings will accelerate the design of flexible thermoelectric devices based on reliable group IV semiconductors.