Silicon content influence on structure and photoluminescence properties of carbon rich hydrogenated amorphous silicon carbide thin films

Abstract

C-rich hydrogenated amorphous silicon carbide (a-Si1-xCx:H) thin films were grown from hydrogen diluted silane (SiH4) and methane (CH4) mixtures in a plasma-enhanced chemical vapor deposition (PE-CVD) system at different silane gas flow rates. The effects of Si content on the composition, microstructure and photoluminescence (PL) properties of the films have been systematically investigated by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HR-TEM), ultraviolet–visible (UV–Vis) transmittance and PL spectra. The multiphase structure of the grown films is confirmed as graphite-like sp2-C rich clusters embedded in a Si-C/C-C random network, and the diameter of the spherical sp2-C clusters is about 20–60 nm. As Si atoms are gradually incorporated into the films, they replace some C atoms in the Si-C/C-C random network, which results in an increase of structure disorder and brings large band tail states and narrow Eg. Furthermore, it is found that both the sp3 Si-C/C-C random network and the sp2 carbon clusters are the origin of the PL emission, and the PL properties can be tuned by changing the Si content and the sp2 carbon clusters in the C-rich a-Si1-xCx:H thin films.