Transport mechanism and its relationship with heterogeneity in a-Si: H

Hydrogen evolution and dc electrical conductivity measurement have been carried out for a-Si: H prepared by d.c. and r.f. glow discharge decomposition of silane. We show that the kink in log σ vs 1/T plot can be explained in terms of the film heterogeneity. Kinks can appear or disappear after successive annealing depending on the specimens, and the upward shift in kink temperature by annealing is observed for the specimens showing kinks. These results are interpreted to be due to the structural and compositional change in heterogeneity caused by the diffusion and rearrangement of hydrogen.