SIMS and auger investigation of thin a-SiC and a-SiC:H films by Up-Down sputtering DC magnetron, impact on optical properties

This article deals with an early growth study of hydrogenated and non-hydrogenated amorphous silicon carbide thin films (a-SiC:H, a-SiC). Sample have been elaborated at room temperature by a new configuration (Up-down) sputtering d.c. magnetron technique, using a 6H-SiC polycrystalline target onto p-Si(100) and glass substrates. The infrared spectra reveal the existence of a band located at 740 cm^-1, which corresponds to Si-C stretching mode of amorphous silicon carbide. The SIMS and AES profiles show a c-face for both a-SiC:H and a-SiC. Films elaborated with this configuration (Up-down) are stoichiometric, with a ratio ²⁸Si/¹²C = 0.95, compared to the one elaborated with conventional configuration (Down-up), which is 1.75. The optical gap is 1.84 eV and 1.48 eV for a-SiC: H and a-SiC respectively. This behavior of optical gap may be related to the hydrogen concentration present in the films or other impurities inducing such a decrease in optical gap.