Structure and mechanical properties of diamond-like carbon films with copper functional layer by cathode arc evaporation

Using direct-current and pulsed cathode arc plasma technique, diamond-like carbon (DLC) bilayer films with Cu functional layer (interlayer and surface layer) were prepared on silicon substrate and annealed at various temperatures in vacuum. The effects of Cu functional layer and annealing temperature on the structure, morphology and mechanical properties of the films were investigated. The results showed that Cu functional layer changed the bilayers microstructure, including the size of sp2 carbon clusters and the thickness and element distribution of diffusion layer. A simple three-layer model was used to describe the interdiffusion between Cu and C layers. Cu interlayer facilitated the graphitic rearrangement in bilayer films due to weak Cu/C bonds and Cu surface layer could be more effective against graphitization. Cu/DLC and DLC/Cu bilayers showed highly dispersed nano-agglomerates on the surface, and the particle size and surface roughness of the bilayers were largely affected by annealing temperature. The hardness and stress of the bilayer were dependent on the location of Cu functional layer. DLC/Cu bilayer possessed a relatively higher hardness and a lower stress at low annealing temperature of 100–400 °C. The results may be of interest for studying the relaxation of stress in the DLC bilayer films and can be used in advancing the development of DLC based engineering materials with high mechanical properties.