Low temperature internal friction study of light-induced structural instability in hydrogenated amorphous silicon

Abstract Light-induced structural change in some different types of a-Si:H and a-Si:D films has been studied by low temperature internal friction measurements. After extended light-soaking at room temperature, the low-temperature internal friction of a-Si:H prepared by both hot-wire and plasma-enhanced chemical-vapor deposition (PECVD) increase to ∼6×10 −6 , although their initial internal friction, the amount and the microstructure of hydrogen in both types of films differ. We attribute this similarity to an increase of structural disorder. However, the effect is considerably smaller in similarly prepared hot-wire a-Si:D. Experiments conducted on a sample prepared by hot-wire chemical-vapor deposition (HWCVD) show that this change anneals out at room temperature in about 70 days. Possible relation of the light-induced structural change to the Staebler–Wronski effect (SWE) is discussed.