Investigation of vacancy-type defects in diamond-like carbon films using slow positron beam

Abstract

Positron annihilation spectroscopy (PAS) was conducted to investigate the vacancy-type defects of diamond-like carbon (DLC) films. From the Doppler broadening measurements of the γ-rays produced by annihilation and positron annihilation lifetime (PAL) using a slow positron beam on diamond-like carbon (DLC) films deposited by various deposition methods and conditions, it was found that there is a good correlation between the S-parameter that was obtained by Doppler broadening, and PAL. The result of PAL correlates well with film density and hardness, indicating that PAL measurement can be used as an indicator of these film properties. The hydrogen content in the DLC film is roughly proportional to the PAL. However, there were also cases observed where the PAL differed greatly even with almost the same hydrogen content and the sp2/(sp2+sp3) ratio of carbon in DLC films has no direct relationship with PAL.