Nature of metastable and stable dangling bond defects in hydrogenated amorphous silicon

Abstract We present a new microscopic model for metastable Si dangling bond defect creation in hydrogenated amorphous silicon. Carrier localisation on short, weak Si–Si bonds causes the bond to break. One hydrogen atom from a nearby doubly hydrogenated Si–Si bond (SiHHSi) moves to the T d site of the broken Si–Si bond, leaving the remaining H atom also in a T d site. The net reaction produces two SiHD defects (intimate Si dangling bond and Si–H bond), where both the H atoms are in the T d site. The T d site is energetically favoured over the BC site, for short, weak bonds. The distance between the dangling bonds and the H atoms, in the T d sites, is in the range 4–5 A. The vast majority of silicon dangling bonds, both metastable and stable, are SiHD, with the H atom in the T d site.