Thermal modification of wide-bandgap hydrogenated amorphous silicon-carbon alloy films grown by plasma-enhanced chemical vapour deposition from C₂H₂+SiH₄ mixtures

Abstract

The thermal stability of hydrogenated amorphous silicon-carbon (a-Si_1−xC_x: H) alloy films grown by plasma-enhanced chemical vapour deposition from C₂H₂+SiH₄ mixtures was characterized by means of infrared spectroscopy, electron spin resonance, transmittance-reflectance spectroscopy and photoluminescence (PL) spectroscopy. It is demonstrated that the network undergoes relaxation and reconstruction under the condition of low-temperature annealing. Weak C-C, Si-Si and C-Si bonds will be broken, and a new stage of hydrogen effusion and structural rearrangement will occur under the condition of high-temperature annealing. The thermal stability a-Si_1−xC_x:H of films increases with increase in carbon content. In carbon-poor a-Si_1−xC_x:H networks, the dangling bonds are the main non-radiative recombination channel, which causes a strong correlation of the PL signal with defect density. In carbon-rich a-Si_1−xC_x:H networks, π-bonded clusters play an important role in the luminescence process. The PL intensity has little dependence on defects in carbon-rich a-Si_1−xC_x:H.