Hydrogen bonding and migration in amorphous silicon

We present a theoretical study on the structure of hydrogenated amorphous silicon based on large-scale tight-binding molecular-dynamics simulations. The atomistic model here discussed is consistent with experimental findings and allows for a complete characterization of Si-H complexes embedded in the amorphous network. We also investigate the mechanism of migration of hydrogen in two concentration regimes and compute the activation energy for such a process. The microscopic mechanism emerging from the present investigation gives rise to a diffusion behaviour consistent with experimental results.