Microvoids in diamond-like amorphous silicon carbide

Abstract

The correlation between composition, microstructure, and optical properties of a-Si1-xCx:H thin films with different stoichiometries was established. The alloys were deposited by radio frequency glow discharge under "starving" plasma conditions from mixtures of SiH4 and CH4. The samples were characterized by small angle x-ray scattering, ultraviolet-visible and infrared spectrometry, and Auger electron spectroscopy. The results showed the presence of microvoids with sizes between ≅3 Å and ≅8 Å. The relative microvoid volume fraction displayed a maximum for x around 55 at. % and decreased for higher values of x. High carbon content alloys (x≅70 at. %) not only have a lower relative microvoid volume fraction, but show optical gaps as high as 3.7 eV, high resistivity, and very low refractive index, indicating the presence of a diamond-like C-C structure. These remarkable results are attributed to the deposition under "starving" plasma conditions.