We report first principles ab initio density functional calculations of hydrogen dynam- ics in hydrogenated amorphous silicon. Thermal motion of the host Si atoms drives H diffusion, as we demonstrate by direct simulation and explain with simple models. Si-Si bond centers and Si ring centers are local energy minima as expected. We also describe a new mechanism for break- ing Si-H bonds to release free atomic H into the network: a fluctuation bond center detachment (FBCD) assisted diffusion. H dynamics in a-Si:H is dominated by structural fluctuations intrinsic to the amorphous phase not present in the crystal.
@article{arxiv.cond-mat/0611375,
title = {Thermally stimulated H emission and diffusion in hydrogenated amorphous silicon},
author = {T. A. Abtew and F. Inam and D. A. Drabold},
journal= {arXiv preprint arXiv:cond-mat/0611375},
year = {2009}
}