Thermally stimulated H emission and diffusion in hydrogenated amorphous siliconT. A. Abtew, F. Inam and D. A. Drabold
Department of Physics and Astronomy, Ohio University - Athens, OH 45701, USA
received 29 March 2007; accepted in final form 15 June 2007; published August 2007
published online 13 July 2007
We report first principles ab initio density functional calculations of hydrogen dynamics 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 breaking Si-H bonds to release free atomic H into the network: fluctuating bond center detachment (FBCD)-assisted diffusion, in which a bond center H may be liberated by intercession of a third nearby Si. H dynamics in a-Si:H is dominated by structural fluctuations intrinsic to the amorphous phase not present in the crystal.
66.30.Jt - Diffusion of impurities.
66.30.-h - Diffusion in solids.
61.43.Dq - Amorphous semiconductors, metals, and alloys.
© Europhysics Letters Association 2007