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

Abstract

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.