Surface, microstructure and optical properties of copper-doped diamond-like carbon coating deposited in pulsed cathodic arc plasma

• A well-adhered Cu-doped DLC coating with smooth surface was obtained by vacuum plasma deposition.
• A layered microstructure of the coating was revealed and discussed.
• Optical properties of the coating, refractive index and absorption coefficient were measured.
• The relationship between refractive index and diamond phase was established.

Diamond-like carbon (DLC) coating doped with copper has been deposited on silicon substrate by pulsed cathodic arc plasma using a composite cathode made of graphite with inserted copper rods. The surface morphology, microstructure and distribution patterns of elements in the coating and substrate have been studied by atomic force microscopy, scanning electron microcopy, Raman spectroscopy and energy dispersive spectroscopy. The results show that the studied coating is very well-adhered to the silicon substrate, with no microcracks, microvoids, localized delaminations or other defects being observed at the coating/substrate interface. It is also shown that the studied coating has layered microstructure and its surface is very smooth, however containing a few of nano-sized particle-like projections of copper oxide that seems to be a specific feature of all the pulsed methods used for deposition of DLC coatings doped with metals. The distribution patterns of elements in the microstructure of the studied coating are discussed. The relationship between refractive index of the coatings, and the intensity ratio of D and G peaks in the Raman spectrum has been established.