S-parameter positron beam measurements have been done on several kinds of a-Si: Kr-sputtered a-Si, PECVD a-Si, MeV ion beam amorphized Si and a-Si grown in an MBE-system at a low deposition temperature. Kr sputtered a-Si becomes denser for higher Kr concentration. PECVD a-Si:H contains micro-cavities with a size depending on growth temperature. MeV ion beam amorphized Si contains 1.2 at.% small vacancies, which decreases upon annealing (relaxation) to 0.4 at.%. This effect can be mimicked by H-implantation and subsequent annealing, showing that at least some of the dangling bonds in a-Si are located at these vacancy-type defects. Finally positron measurements show that MBE-system grown a-Si contains large open-volume defects. The positron annihilation data are supplemented by data from some other techniques.

American Institute of Physics
E. Ottewitte , A.H. Weiss

Hakvoort, R. A., van Veen, A., Schut, H., van den Boogaard, M. J., Berntsen, A., Roorda, S., … Reader, A. H. (1994). Characterization of amorphous silicon. In E. Ottewitte & A. H. Weiss (Eds.), Slow Positron Beam Techniques for Solids and Surfaces : Fifth International Workshop, Jackson Hole, WY, August 1992 (pp. 48–52).