Effect of Substrate Temperature on Structural and Optical Properties of Un-Doped Diamond Thin Film

Abstract

Un-doped diamond thin films were deposited at various substrate temperatures (from 300 °C to 500 °C) onto glass substrates by using direct current plasma enhanced chemical vapour deposition (DC-PECVD) system. The fabricated films were having amorphous phase which shown by X-ray diffraction (XRD). Atomic force microscopy (AFM) has discovered that the RMS surface roughness and the thickness which were obtained in the range of 0.69 nm to 1.67 nm and 4.8 nm to 0.83 nm, respectively as increasing substrate temperatures. From UV visible spectroscopy (UV-VIS), it was found that the optical transition had changed from forbidden indirect transition to allowed indirect transition as the substrate temperature increased. The optical band gaps were increased (3.14 eV, 3.93 eV and 4.09 eV) when the substrate temperatures increased. Hence, the higher the substrate temperatures, the larger the cluster size and RMS surface roughness and result in decreasing of films thickness and increasing the optical band gap.