Optical, electrical and microstructural properties of SiC thin films deposited by reactive dc magnetron sputtering

Abstract

In this study, amorphous silicon carbide (SiC) thin films of variable compositions were deposited on Si (100) and glass substrates by reactive direct current magnetron sputtering of high purity silicon target, using CH4 as reactive gas. The composition and the properties of the coatings have been modified by the change in the reactive gas flow rate from 5% to 50%. Spectrophotometer has been used to measure the optical transmittance and reflectance of silicon carbide thin films over the spectral range from 280 to 1000 nm. The optical constants such as refractive indices and the extinction coefficients of the films were calculated. The band gap values of the deposited films were further evaluated with respect to the gas flow rate. Transmittance values of SiC films changed from 85% to almost 0% in the visible light range. The optical band gap values of the films were altered from 1.7 to 2.7 eV. The activation energy was found to increase from 0.16 eV up to 1 eV and dark conductivity decreased from 7.42 x 10(-4) to 1.06 x 10(-9) Omega(-1) cm(-1) while carbon concentration in the films increased. The results demonstrated that the optical and electrical properties of SiC films could easily be tailored by modifying Si and C concentrations in the coating composition, for the same film thicknesses.