AbstractThe structural and optoelectronic properties of silicon thin films prepared by hot wire chemical vapor deposition and radio frequency plasma enhanced chemical vapor deposition are studied in the range of substrate temperatures (T_sub)from 100 °C to 25 °C. The defect density, structure factor and bond angle disorder of amorphous silicon films (a-Si:H) deposited by both techniques are strongly improved by the use of hydrogen dilution. Correlation of these structural properties with important optoelectronic properties, such as photo-to-dark conductivity ratio, is made. Microcrystalline silicon (μc-Si:H) is obtained using HW with a large crystalline fraction for hydrogen dilutions above 85% independently of T_sub. The deposition of μc-Si:H by RF requires increasing the hydrogen dilution and shows decreasing crystalline fraction as T_sub is decreased. The properties of the low T_sub films are compared to those of samples produced at 175 °C and 250 °C in the same reactors.