Structure and optical properties of Cu-DLC composite films deposited by cathode arc with double-excitation source

Copper-doped diamond-like carbon films (Cu-DLC) were fabricated on silicon and quartz substrates by cathode arc technique with direct-current and pulse double-excitation source. The microstructure, composition, morphology, hardness and optical properties of the films were studied by Raman, XPS, AFM and SEM, UV-Vis, laser ellipsometer and Vickers sclerometer. The results showed that Cu doping increases the size, ordering and amount of sp(2)-C clusters in the Cu-DLC composite films. The microstructure parameters enhance with increasing the Cu content to 22.4 wt%. All the films show specific nano-structural surface, however, the lower Cu content induces finer particle formation in the Cu-DLC films. When the arc current is higher than 60 A, the roughness and particle size of Cu-DLC composite films increase with increasing the Cu content. The average transmittance of the Cu-DLC films in Vis-NIR region is smaller than 40% when the Cu content exceeds 12.6 wt%. With increasing the Cu content, the optical band gap (E-g) of the films decreases from 3.54 eV to 0.25 eV. The relationships among the E-g, refractive index and extinction coefficient for the Cu-DLC films were found and indirectly revealed the correlation of microstructure and optical properties of the films with the Cu content variation. (C) 2016 Elsevier B.V. All rights reserved.