Synthesis of diamond-like carbon films by pulsed laser deposition in a tiny vacuum chamber

摘要

Diamond like-carbon films were fabricated by pulsed laser ablation of a liquid target (vacuum oil) in a very small (volume below 1 cm~3) vacuum chamber, where the film was deposited onto the inner surface of the chamber window. The synthesis was carried out at room temperature using 248 nm KrF excimer laser. The sp~3 hybridization carbon formation was additionally promoted by gaseous H_2O_2 flow through the reaction chamber. Deposited diamond-like carbon films were characterized by Raman scattering spectroscopy, optical and atomic force microscopy. The results indicated that higher sp~3 content was present in the film areas exposed to the laser irradiation during the deposition. The surface roughness of these areas was lower compared with that of the non-irradiated areas. Optical microscopy observations indicated that the films had interference-colored regions on laser irradiated areas. These colored regions were significantly different from their surroundings, which were grey or brown. Thus, the interference-colored regions have very wide band gap (ΔE > 3 eV) and accordingly, high sp~3 hybridized carbon content.