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

•Compositional ratio of dual ion beam sputter deposition (DIBSD) grown amorphous SiC thin films were examined.•SiC films of thickness ranging from ~20 nm to ~450 nm, were characterized and studied.•Thickness dependency on compositional ratio of SiC thin films was observed through XPS analysis.•A thickness dependent distinct change in band gap as a consequence of variation in the compositional ratio in SiC films, is reported. 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 (