THERMAL MODIFICATION OF WIDE-BANDGAP HYDROGENATED AMORPHOUS SILICON-CARBON ALLOY-FILMS GROWN BY PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION FROM C2H2+SIH4 MIXTURES

The thermal stability of hydrogenated amorphous silicon-carbon (aSi(1- x)C(x):H) alloy films grown by plasma-enhanced chemical vapour deposit ion from C2H2+SiH4 mixtures was characterized by means of infrared spe ctroscopy, electron spin resonance, transmittance-reflectance spectros copy and photoluminescence (PL) spectroscopy. It is demonstrated that the network undergoes relaxation and reconstruction under the conditio n 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 rearrange ment will occur under the condition of high-temperature annealing. The thermal stability a-Si1-xCx:H of films increases with increase in car bon content. In carbon-poor a-Si1-xCx:H networks, the dangling bonds a re the main non-radiative recombination channel, which causes a strong correlation of the PL signal with defect density. In carbon-rich a-Si 1-xCx:H networks, pi-bonded clusters play an important role in the lum inescence process. The PL intensity has little dependence on defects i n carbon-rich a-Si1-xCx:H.