Deposition of a-Si:H thin films embedded with nano-crystalline through dilution of argon

The structure of hydrogenated amorphous silicon (a-Si:H) thin films embedded with nano-crystal grains deposited by conventional radio frequency (RF) plasma enhanced chemical vapor deposition (PECVD) through decomposition of silane diluted with argon has been studied by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopy. It is observed that argon as dilution gas plays a significant role in the growth of nano-crystal grains and amorphous network in a-Si:H thin films. The structural variation of the thin films with different dilution ratios suggests that changing of plasma conditions in the chamber leads to the nanocrystallizing of the thin films. The nanocrystallization process initiating at a relatively low dilution ratio has been observed. Moreover, a positive effect of argon dilution on the nanocrystallization has also been observed. The structural changes studied under argon dilution are explained by a proposed model based on the energy exchange between argon plasma constituted of Ar^* and A⁺ radicals and the growth region of the thin films.