Surface modification of chalcogenide glass for diamond-like-carbon coating

Abstract

Property controllability via compositional adjustment as well as moldability intrinsically bestowed to chalcogenide glass is garnering attention for use in thermal cameras operating at the long-wavelength infrared spectral range. Since chalcogenide glass lens features in general relatively higher refractive index and lower hardness, as compared with SiO2-based oxide glass counterpart, it necessitates functional coating(s) for anti-reflection and hardness improvement, respectively. Diamond-like carbon can act as a much-hardened antireflective coating layer of chalcogenide glass, but interface between these two materials seems to lack adhesion sufficient for practical use. In an effort to alleviate this poor adhesion issue, prototypical Ge-Sb-Se and Ge-Ga-Se chalcogenide glasses were doped with small amount (up to 0.5 at.%) of carbon in this study. The surface of these carbon-doped chalcogenide glasses was then verified to be more hydrophobic and more compatible with diamond-like-carbon coating. Changes in infrared transmittance, Vickers hardness, water wettability and durability of diamond-like-carbon layer accompanied with the carbon doping are delineated in comparison with those of the undoped glasses.