Thermal effects on structure and photoluminescence properties of diamond-like carbon films prepared by pulsed laser deposition

Un-hydrogenated Diamond-like Carbon (DLC) films were prepared by pulsed laser deposition technique at different substrate temperature. The Raman spectra, the absorption and the photoluminescence spectra were measured. The dependence of structure and photoluminescence properties on deposition temperature were studied in detail. The experimental results indicate that the sp2 sites form small clusters that consist of both olefinic chains and aromatic ring groups within the sp3 matrix. With raising deposition temperature, the optical band gaps increase from 1.87 to 2.85 eV. The main band of photoluminescence centered at around 700 nm shifts to short wavelength, and the intensity of this band increases. The photoluminescence can be attributed to carrier localization within an increasing sp2 clusters. It was clarified that the DLC films are ordered with increasing deposition temperature.