Structural, optical and electronic properties of amorphous SiC: H alloys prepared by magnetron sputtering of silicon in methane-argon gas mixtures

Abstract

Amorphous Si_1−x C _x :H films have been prepared by the r.f. magnetron sputtering method using a silicon target in a gas mixture of argon and methane. The carbon content x was varied by varying the partial pressure of methane with respect to the total gas pressure. The dependence of the optical, structural and electrical properties on x has been investigated. With increasing x, the optical band gap increases owing to the hydrogenation of silicon in the region of small x and to the increase in the number of Si-C bonds in the large-x range, according to evidence from infrared spectra. While the dark conductivity decreases with increasing x, the photoconductivity shows a maximum at about x = 0·2. The photoconductivity increases in the range of x below 0·2 owing to the hydrogenation of silicon. Although it decreases in the range of x above 0·2, the values are larger than those of films prepared by glow-discharge decomposition of methane-silane gas mixtures reported in the literature. This is interpreted as being due to relatively simple bonding structures between carbon and hydrogen, owing to the deposition conditions of high power and low pressure, compared to the glow-discharge method.