Ellipsometric investigation of nitrogen doped diamond thin films grown in microwave CH4/H2/N2 plasma enhanced chemical vapor deposition

The influence of N-2 concentration ( 1%-8%) in CH4/H-2/N-2 plasma on structure and optical properties of nitrogen doped diamond ( NDD) films was investigated. Thickness, roughness, and optical properties of the NDD films in the VIS-NIR range were investigated on the silicon substrates using spectroscopic ellipsometry. The samples exhibited relatively high refractive index ( 2.6+/-0.25 at 550nm) and extinction coefficient ( 0.05+/-0.02 at 550nm) with a transmittance of 60%. The optical investigation was supported by the molecular and atomic data delivered by Raman studies, bright field transmission electron microscopy imaging, and X-ray photoelectron spectroscopy diagnostics. Those results revealed that while the films grown in CH4/H-2 plasma contained micron-sized diamond grains, the films grown using CH4/H-2/(4%)N-2 plasma exhibited ultranano-sized diamond grains along with n-diamond and i-carbon clusters, which were surrounded by amorphous carbon grain boundaries. Published by AIP Publishing.