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

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 inte rnal friction of a-Si:H prepared by both hot-wire and plasma-enhanced chemi cal-vapor deposition (PECVD) increase to similar to 6 x 10(-6), although th eir initial internal friction, the amount and the microstructure of hydroge n in both types of films differ. We attribute this similarity to an increas e of structural disorder. However, the effect is considerably smaller in si milarly prepared hot-wire a-Si:D. Experiments conducted on a sample prepare d by hut-wire chemical-vapor deposition (HWCVD) show that this change annea ls out at room temperature in about 70 days. Possible relation of the light -induced structural change to the Staebler-Wronski effect (SWE) is discusse d. (C) 2000 Published by Elsevier Science B.V. All rights reserved.