Nitrogen Induced Structural Evolution and the Resultant Optical Behavior of PECVD Derived Silicon Carbide Thin Films

Abstract

Nitrogen-doped Silicon Carbide (SiC) thin films were deposited on p-Si (100) and glass substrates using Radio Frequency Plasma Enhanced Chemical Vapor Deposition (RF-PECVD) technique. The structural, compositional, and linear and non-linear optical properties of the films were probed as a function of nitrogen content using various characterization techniques; like Grazing Incidence X-ray Diffraction (GIXRD), X-ray Photoelectron Spectroscopy (XPS), UV–Visible Spectroscopy, and Photoluminescence Spectroscopy. Increase in the N₂ flow rate from \(0\% \;to\; 41.2\%\) during deposition resulted in decrease in intensity of the α-SiC peak (\(1020)\) in the XRD spectra, due to formation of the Si–N bonds, indicating reduction in crystallinity. XPS confirms formation of SiC hexagonal phase in the film surface, and Nitrogen doping was found to cause oxidation due to generation of defect sites. Band-gap widening is observed with increasing N₂ concentration up to 5 sccm (2.43–2.67 eV), beyond that the value decreases. Intense visible emission was observed in N-doped films, along with the UV emission, which is observed for undoped film as well. The CIE-1931 chromaticity plot exhibits color perception close to pure white in the N-doped SiC films, the blue color perception is observed in the undoped SiC film. The value of Correlated Colour Temperature for the samples in the white light region is in between \(2500\) K and \(6500\) K which shows the high quality of the generated white light.