Unexpected dynamics for self-interstitial clusters in silicon.

Ab initio molecular-dynamics simulations of self-interstitial clusters in Si show that I2 and the most stable of the I3 (" I(a)(3)") clusters diffuse extremely fast. In these clusters, the I's share a single bond-centered (BC) site. The metastable I(b)(3) cluster involves three adjacent BC sites.

Molecular hydrogen in a-si:H.

It is demonstrated that in high quality hydrogenated amorphous silicon films nearly 40% of the contained hydrogen is in the form of hydrogen molecules individually trapped in the amorphous equivalent of tetragonal T sites. The majority of these molecular hydrogens are in the less-clustered component of the contained hydrogen. These results could have major implications for the understanding of light-induced defects and hydrogen mobility.