Confinement induced variation of composition ratio in amorphous silicon carbide thin films and effect in optical properties

Thickness dependency in the composition ratio of amorphous silicon carbide (SiC) thin films and its effect in optical properties are reported. SiC thin films (~ 20 nm to 450 nm range) with very low surface roughness (<1 nm) were grown using dual ion beam sputtered (DIBS) deposition technique. Thinnest SiC film (~ 20 nm) exhibited higher atomic concentration of silicon (Si) relative to that of carbon (C), with C:Si = 0.7, whereas carbon to silicon atomic concentration ratio (C:Si) was found to increase with increasing SiC film thickness, and reached 1:1 ratio for thickest SiC film (about 450 nm), using X-ray photoelectron spectroscopy (XPS) analysis. XPS was employed to investigate the chemical composition and bonding configuration of SiC. A thickness dependent distinct change in band gap as a consequence of variation in the composition ratio in SiC films, is reported, which indicates potential control on electrical and optical properties of the system.