Control of Optical Gap in a-SixC1-x: H Alloy Films Produced by Reactive Sputtering Method

Abstract

Hydrogenated amorphous silicon-carbon alloy (a-SixC1-x: H) films are prepared by simultaneous if reactive sputtering of silicon and graphite in a H2–Ar gas mixture. The optical gap E0 of a-SixC1-x: H depends on alloy composition x and preparation conditions. The optical gap E0 of a-SixC1-x: H prepared under a same condition is ∼1.7 eV at x=1.0 (a-Si: H), increases with the decrease in x, reaches a maximum value of 2.2 eV at x=0.6 and then decreases with decrease in x, reaching ∼1.4 eV at x=0 (a-C: H). For films prepared at lower substrate temperature, the optical gap becomes larger. This behavior of the optical gap is discussed referring to the results of X-ray photoemission spectroscopy, infrared absorption measurements, etc., on a-SixC1-x: H.