Selective bonding effect on microstructure and mechanical properties of (Al,N)-DLC composite films by ion beam-assisted cathode arc evaporation

Using weak-carbide metal Al and carbide non-metal N elements as co-dopant, (Al,N)-DLC composite films were prepared by DC- and pulse cathode arc technique. Microstructure, compositions, morphology and mechanical properties of (Al,N)-DLC films were investigated in the dependence of pulse frequency and target current by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy, nanoindentation, surface profilometer and nano-scratch. Raman and XPS results showed that the size of Csp2 clusters decreases and the content of Csp3 bonds increases for the (Al,N)-DLC films at the low pulse frequency with low target current or the high target current with high frequency. The contents of C–N and N–sp3C bonds increase with the target current increases. The (Al,N)-DLC films at higher target current contained a high content of N atoms and Al–N bonds. Low pulse frequency with high target current improved the hardness and toughness of (Al,N)-DLC films corresponding to the variation of microstructure parameters (the size and ordering of Csp2 clusters) and compositions (N–sp3C and Al–N bonds).