HYDROGEN MOTION IN HYDROGENATED AMORPHOUS-SILICON (A-SI-H)

Dipolar spin lattice relaxation time, T-1D, measurements of H-1 in a-S i:H have been used to probe the local motion of hydrogen in a-Si:H. Va riations of T-1D with doping level reveal a trend similar to the chang es in hydrogen diffusion constants measured in similar samples using s econdary ion mass spectroscopy (SIMS), The temperature variations of T -1D indicate that, if the local motion is thermally activated, the act ivation energies are at least an order of magnitude smaller than those measured using SIMS. The 'diffusion constants' for local hydrogen mot ion inferred from T-1D measurements are many orders of magnitude faste r than the diffusion constants obtained from SIMS. The T-1D measuremen ts an made on the timescale of milliseconds while the SIMS measurement s are performed on a scale of several hours to days. A phenomenologica l model provides a plausible connection between these two measurements . which are made on very different timescales.