Radiation response and optical characterization of carbon based thin-films prepared by saddle field plasma enhanced chemical vapor deposition

Abstract

Carbon based thin-film materials have been attracting a lot of attention in many research fields due to their unique material properties. Detection of ionizing radiation is an important application that carbon and diamond based materials, which offer a promising detection material with low manufacturing cost and a variety of physical characteristics for different detection applications. In the current study, the direct current (DC) saddle field Plasma Enhanced Chemical Vapor Deposition (PECVD) method was used to prepare a set of nano-crystalline diamond samples. The relation between the deposition pressure, the gases mixing ratios and the resultant film characteristics were studied. The optical, microstructure and electronic properties of the prepared samples were studied using Raman spectroscopy, FTIR, UV-Visible spectroscopy and I –V characteristics methods. It was found that, an increase in the hydrogen content in the gas mixture leads to a decrease in the crystallinity of the resultant film. A set of samples were selected with different crystalline content and defect DOS to investigate the impact of these parameters on the material’s radiation response. It was determined that, the sample with relatively high degree of crystallinity and with the presence of defects close to the valence show promising responses for radiation detection applications. We attributed this results to the fact that, transport is dominated by electrons and shallow defects near the conduction band act as electron traps. On the other hand, hole-traps near the valence band do not have the same impact on the overall transport properties