Oxidation and interface states in a-Si: H

In a-Si: H films with columnar growth morphology, the material between the columns reacts with air, leaving an Si–O suboxide coating on the columns of estimated thickness 5–10 Å. At the a-Si: H/oxide interface a dangling-bond density of ∼3 × 1011 cm−2 develops with time. We suggest that the oxide layer and the surface defects are characteristic of exposed surfaces of any a-Si: H film. It is emphasized that the surface defect states can have a strong influence on the electronic properties of the material.