Thermal Conductivity of Nanocrystalline Silicon Prepared by Chemical-Vapor Deposition

Thin film nanocrystalline silicon prepared by chemical-vapor deposition is an established material used in multijunction amorphous silicon solar cells. Its potential in low cost and scalable thermoelectric applications depends on the reducing grain sizes to nanometers while simultaneously maintaining a high crystalline to amorphous ratio. In this work, we show that by varying the hydrogen dilution of silane gas flow during deposition, we can reduce average grain sizes to a few nanometers while still maintaining $\sim$ 90{\%} crystallinity of the material. Annealing at 600 $^{\circ}$C improves crystalline content with only a small increase of the grain sizes. The values of thermal conductivity, measured from 85 K to room temperature as function of hydrogen dilution ratio from full amorphous to nanocrystalline silicon, remain at a level that is typical for amorphous silicon.