Hydrogen evolution in hydrogenated microcrystalline silicon carbide thin films

Evolved gas analysis (EGA), infrared attenuated reflection (ATR), and Raman spectroscopy experiments are used to study hydrogen evolution in hydrogenated microcrystalline silicon carbide (μc-Si_1-xC_x:H) films prepared by plasma-enhanced chemical vapor deposition. The results are compared with microcrystalline silicon (μc-Si:H). The effused hydrogen and carbon-hydride groups (CH, CH₂, and CH₃) are measured up to 800 °C. Their EGA curves have a peak at 410 °C, attributed to the methyl groups incorporated in the amorphous matrix during the deposition process. Moreover, hydrogen evolution curves show narrow and sharp peaks centered at 425 and 520 °C, corresponding to hydrogen desorbing from silicon hydrides at grain boundaries. While its content is more important than hydrogen bonded to silicon in the amorphous and denser crystalline regions of μc-Si_1-xC_x:H, but remains lower than in the μc-Si:H film. Raman and ATR data indicate that the μc-Si_1-xC_x:H film is composed of small size silicon crystallites embedded in a hydrogenated amorphous silicon carbide matrix and confirmed that carbon is incorporated in the amorphous matrix as methyl groups (CH₃), inducing a decrease in SiH_x groups compared to the μc-Si:H film.