Catalytic effect of Al and AlN interlayer on the growth and properties of containing carbon films

Diamond-like carbon (DLC) and carbon nitride (CNx) bilayer films with Al and AlN interlayer were fabricated by pulse cathode arc technique. The structure, composition, morphology and mechanical properties of the films were investigated by Raman, Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), Knoop sclerometer and surface profilometer. The results indicated that the complete diffusion between C and Al atoms occurs in the Al/DLC and Al/CNx bilayer. Al interlayer induces the increase of the size and ordering of Csp2 clusters in the films but AlN interlayer increases the disordering degree of Csp2 clusters. XPS results showed that a higher content of Csp3/Csp2 bonds presents in the Al/CNx bilayer, and Al and AlN interlayer decreases the atomic ratio of N/C. AFM with phase contrast mode illustrated the morphologic characteristics of the bilayer films. All the bilayers show a nano-structural surface. The morphology changes of the bilayer were well explained by the surface state of the substrate and the growth mechanism of DLC films. The hardness of Al/DLC bilayer decreases but it increases for the other bilayers compared to the corresponding DLC (CNx) monolayer. The internal stress of the bilayer is significantly lower than that of the monolayer except for the AlN/CNx bilayer. These studies could make the difference at the time of choosing a suitable functional film for certain application.