Optical Characteristics of Hydrogenated Amorphous Silicon Carbide Films Prepared at Various Gas Flow Rate Ratios

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Hydrogenated amorphous silicon carbide (a-SiC:H) films were prepared using a home-built plasma-enhanced chemical vapor deposition (PECVD) system with different flow rate ratios of methane (CH4) and silane (SiH4) gases. Fourier-transform infrared (FTIR) spectra indicate multiple bonding configurations consisting of wagging, bending and stretching modes of silicon, hydrogen and carbon atoms with a steady depletion of Si–H wagging and stretching modes as the gas flow rate ratio increases. Micro-Raman spectra show evidence of amorphous silicon structure in all the films. Only the a-SiC:H film prepared at the highest CH4 to SiH4 gas flow rate ratio shows the existence of the Si–C vibrational mode. All the samples prepared show room-temperature luminescence with two peaks centered at 467 and 698 nm. The photoluminescence (PL) intensity increases as the CH4 to SiH4 gas flow rate ratio increases but a reduction in intensity is observed for a high CH4 to SiH4 gas flow rate ratio. a-SiC:H films with higher optical energy gaps were obtained by allowing the gases to flow at higher CH4 to SiH4 gas flow rate ratios.
2007-10-15