The hydride configurations in the hydrogenated amorphous Si (a-Si:H) network were studied by means of infrared absorption spectroscopy. The results on the film mass density of a-Si:H deposited by means of an expanding thermal plasma reveal the presence of two distinct regions in terms of H content and microstructure: below approximately 14at%H a-Si:H contains predominantly divacancies decorated by H, above 14at%H a-Si:H contains microscopic voids. These two distinct regions provided additional information on the origin of the low and high hydride stretching modes at 1980 to 2010 and 2070 to 2100/cm, respectively.

Vacancies and Voids in Hydrogenated Amorphous Silicon. A.H.M.Smets, W.M.M.Kessels, M.C.M.van de Sanden: Applied Physics Letters, 2003, 82[10], 1547-9