Surface-sensitive Raman scattering study on a-Si:H network formation process during deposition and H2 plasma annealing

Abstract The early stages of hydrogenated amorphous Si (a-Si:H) growth from a hydrogen-diluted silane plasma at 250°C and structural change induced by a H 2 plasma treatment subsequent to the film growth have been investigated by Raman scattering under a surface sensitive condition. For films thinner than 2 nm a Raman band due to the wagging mode of silicon hydrides is observed, while Raman bands originating from amorphous silicon network increase with progressive film growth after 2 nm deposition. The result indicates that there exists a hydrogen-rich a-Si network within 2 nm from the top surface terminated mainly with SiH 3 and SiH 2 bonds. Also spectral changes caused by exposing as-grown 2 and 3 nm-thick films to a H 2 plasma at 250°C have shown that the H 2 plasma treatment promotes the chemical reactions for the desorption of bonded hydrogen on and near the surface region and resulting propagation and structural relaxation of a-Si network.