Growth and characteristics of diamond-like carbon films with titanium and titanium nitride functional layers by cathode arc plasma

Diamond-like carbon (DLC) bilayer films were prepared on silicon substrate by direct-current and pulse cathode arc method, using nano-scaled Ti and TiN interlayer and surface layer as functional layer. All films were annealed at 500 °C in vacuum. The structural, morphological and mechanical properties of DLC bilayers were investigated in dependence of functional layer and annealing by Raman spectroscopy, Auger electron spectroscopy, scanning electron microscopy and atomic force microscopy, Knoop sclerometer and surface profilometer. The results showed that adding interlayer or surface layer on carbon layer could change the microstructure of the bilayer, including the atom diffusion at interface, the ordering and size of sp2 carbon clusters, and atomic rearrangement of carbon bonds. The interlayer introduced in the bilayer determined the growth mode of carbon layer, while the surface layer was characterized by the injection effect of Ti and N atoms/ions to the carbon layer. Moreover TiN surface layer facilitated the formation of graphitic microcrystal in the carbon layer. Some significant differences of Ti and TiN functional layers in the bilayer depended on themselves structure feature and reaction ability with carbon. The hardness and internal stress of the bilayer were affected accordingly. All bilayers after annealing showed an improved hardness especially for the case of Ti and TiN surface layers.