On the Effect of the Film Hydrogen Content and Deposition Type on the Grain Nucleation and Grain Growth During Crystallization of A-Si:H Films

We report the effect of the initial film hydrogen content (C_H ) on the crystallization kinetics, crystallite nucleation rate and grain growth rate when HWCVD and PECVD a-Si:H films are crystallized by annealing at 600degC. For the HWCVD films, both the incubation time and crystallization time decrease, and the full width at half maximum (FWHM) of the XRD (111) peak decreases with decreasing film C_H. However, other sources of XRD line broadening exist in such materials in addition to crystallite size, including the density of crystallite defects. To address these issues, TEM measurements have also been performed on a-Si:H films deposited directly onto TEM grids. Following the procedure of Iverson and Reif (J. Appl. Phys. 62 (1987) 1675), an examination of films with low grain density enables a determination of the crystallite nucleation rate as well as grain growth rate. We compare the results for HWCVD films of different film C_H , and also for HWCVD and PECVD a-Si:H films containing the same initial film C_H. We also perform Raman measurements on fully crystallized HWCVD films to explore whether film disorder plays a role in the different XRD FWHMs when different amounts of film hydrogen are evolved