Film properties and photoluminescence characteristics of hydrogenated amorphous silicon nanoball films fabricated using Ar/H₂ mixture gas plasma

Hydrogenated amorphous silicon (a-Si:H) nanoball films which include the Si nanocrystals, can be fabricated by the double tubed coaxial line type microwave plasma chemical vapor deposition (MPCVD) system. We fabricate the a-Si:H nanoball films using pure Ar gas and Ar/H₂ mixture gas as discharge gas with varying gas flow rate in order to change the Si nanocrystal size. And, the substrate table position is changed in order to change the effect of the hydrogen plasma and the diameter of the Si nanocrystal in the a-Si:H nanoball films. As a result, the photoluminescence wavelength decreases, as the H ₂ gas flow rate increases. Furthermore, when the substrate table position is approached to the discharge tube end, the photoluminescence wavelength more decreases (from about 764 to about 715 nm). The diameter of the Si nanocrystal is observed by the Transmission Electron Microscope (TEM) and the X-ray diffraction (XRD). From the observation result, it is found that the diameter of the Si nanocrystal become small (from 5.1 to 4.3 nm), as the effect of the hydrogen plasma increases.