Structural and optical properties of plasma-deposited amorphous hydrogenated oxygenated carbon films

Abstract

Amorphous hydrogenated oxygenated carbon (a-C:O:H) films were deposited from C6H6/O2/He/Ar mixtures in a deposition system fed rf power. The principal variable was the percentage of oxygen in the feed, Rox. Film structure and composition were investigated as a function of Rox using transmission infrared- and x-ray photoelectron spectroscopy. To some degree, greater values of Rox lead to greater incorporation of oxygen functionalities such as OH, C–O, and C=O into the deposited material. As revealed by ultraviolet-visible spectrophotometry, the optical gap E04 increased from ∼3.1 to ∼3.5 eV as Rox was increased from 0% to ∼50%. Semiempirical methods (PM3 and ZINDO-S/CI) allow modeling of the dependence of E04 on Rox. Broad agreement between the results of the experimental and theoretical analyses was obtained.