Silicon-hydrogen bond effects on aluminum-induced crystallization of hydrogenated amorphous silicon films

The effects of hydrogen dilution on aluminum-induced crystallization (AIC) of hydrogenated amorphous silicon (a-Si:H) films have been studied. The Raman spectra showed that the short-range order (SRO) and the intermedium-range order (IRO) of the as-deposited a-Si films increased with the increase of the H2 dilution from 0% to 20%. The optical microscope (OM) and X-ray diffraction (XRD) observation revealed that, compared to the a-Si:H film deposited in pure Ar, the a-Si:H films deposited with H2 dilution in the range of 3-8% possessed a lower crystallization rate while the a-Si:H films deposited with high H2 dilution in the range of 15-20% possessed a faster crystallization rate. It was found that majority of the hydrogen existed in the form of monohydride (SiH) bond in the a-Si:H films with H2 dilution ratio of 3-8%, the bonding energy of which was higher than that of Si-Si bond, leading to a lower crystallization rate of a-Si:H films. While the dihydride (SiH2) bond became dominant in the a-Si:H films with high H2 dilution of 15-20%, the bonding energy of which was lower than that of Si-Si bond, thus accelerating the crystallization rate. Therefore, it was illustrated that not the hydrogen concentration but the form of silicon-hydrogen bond determined the AIC process of a-Si:H films.