Film-thickness dependence of structural and electrical properties of boron-doped hydrogenated microcrystalline silicon prepared by radiofrequency magnetron sputtering

Boron-doped hydrogenated microcrystalline silicon (μc-Si:H) thin films were prepared by radiofrequency magnetron sputtering and the film-thickness dependence of the structural and electrical properties was investigated. The target was a boron-doped silicon wafer on which boron grains were put or not on top of it. At room temperature, the dark conductivities of the μc-Si:H thin films prepared without boron grains were below 10− 6 S cm− 1. On the other hand, for the films prepared with boron grains having thickness above 50 nm, the conductivities were higher than 6 × 10− 1 S cm− 1 and their activation energies were about 0.05 eV. As the film thickness was decreased, the dark conductivity decreased: ∼ 10− 1 S cm− 1 for the 20 nm film and ∼ 10− 6 S cm− 1 for the 10 nm film. This decrease was caused by the decrease in the crystalline volume fraction.