Structural and optical properties o plasma-deposited a-C:H:Si:O:N films^a

Abstract

Thin a-C:H:Si:O:N films were deposited from plasmas fed hexamethyldisiloxane, oxygen and nitrogen, and characterized as a function of the partial pressure of oxygen in the feed, R_ox. Deposition rates varied from 10 to 27 nm min^-1. Surface roughness was independent of R_ox, being around 10 nm. The films contain C=C and C=O, and also Si-C and Si-O-Si groups. Lower [C] and [N] but greater [O] and [Si] were measured in the films as R_ox was increased. Refractive indices of ~ 1.5 and optical energy gaps which fell from ~ 3.3 to ~2.3 eV were observed with increasing R_ox. The Urbach energy fell with increasing optical gap, which is characteristic of amorphous materials. Such materials have potential as transparent barrier coatings.

Keywords:
plasma enhanced chemical vapor deposition; optical band gap; urbach energy