Effect of applied electric field on the chemical structure and thermal diffusion of DLC film irradiated by laser

Abstract

Diamond-like carbon (DLC) films have attracted much attention because of their excellent performance; however, the low anti-laser damage ability of such films seriously restricts their applicability to high-power infrared optical windows or laser system, etc. To overcome this problem, in this study, Titanium (Ti) electrodes were deposited on DLC films directly, forming a transverse bias field on films' surfaces. The damage morphology under laser irradiation was observed both before and after the bias field was applied, and Raman spectroscopy was used to analyse chemical structure of DLC films. It was shown that as the I(D)/I(G) ratio increased, the sp3 content decreased in laser-irradiated regions of DLC films when a bias electric field was not applied. When the bias electric field was applied to DLC films, it could effectively stop the content changing from sp3-bonding carbon to sp2-bonding carbon, prevent the formation of sp2 clusters, and slow down the films graphitisation process. The fast thermal diffusion improves the DLC films' anti-laser damage ability ultimately.