A study on the correlation between the photoinduced volume expansion and the internal stress in hydrogenated amorphous silicon

A photoinduced volume expansion phenomenon in hydrogenated amorphous silicon (a-Si:H) films has been studied from a viewpoint of the initial stress in the film by using the optical-lever bending method. The dependence on deposition temperature for the photoinduced expansion and the initial stress is similar, that is, both have maximum stress at a deposition temperature of 300°C. On the other hand, little difference in the photoinduced expansion was observed among films prepared at the same substrate temperature which have different initial stresses. These results indicate that an internal stress does not affect the photoinduced expansion and that intrinsic stress due to the structure of a-Si:H is the origin of the phenomenon.