Structure and Properties of Silicon Thin Films Deposited at Low Substrate Temperatures

Silicon thin films were grown near the microcrystalline/amorphous boundary at substrate temperatures TS = 35–200°C and dilutions [H2]/[SiH4] = 25–167. The conductivity percolation threshold occurred at crystallinity ~60%, above the random composite threshold 33.3%, due to amorphous tissue coating crystalline grains and limiting the electronic transport. Higher content of hydrogen at lower TS facilitates formation of ordered silicon phase even close to room temperature (the sample grown at 35°C had 30 at% of hydrogen and crystallinity ~60%), providing a technological window for deposition of silicon thin films on cheap polymer substrates with electronic properties suitable for solar cells.