Spectroscopic characterization of annealed Si1-xCx films synthesized by ion implantation

Amorphous hydrogenated silicon carbon alloys were synthesized by C2H2 ions implantation in a silicon substrate at different fluences to obtain samples with different carbon atomic concentrations (10-50 at. %). As-implanted and subsequently annealed samples were investigated by using Rutherford backscattering, infrared, and Raman spectroscopies in order to follow the crystallization process, It was found that crystallization of stoichiometric SiC phase starts at 1000 degrees C both in low and high containing carbon films, while at the stoichiometric composition silicon (or carbon) was found to clusterize into homonuclear islands even at lower temperatures, The analysis of the fundamental absorption edge reveals the presence of an optical energy gap of about 1.3 eV independently on the film composition in the as-implanted samples, while after the thermal process at 1000 degrees C it increases to 2 eV for a carbon concentration below 0.5 and up to 1.8 eV for all those samples with a carbon excess.