Chemical and morphological difference between TiN/DLC and a-C:H/DLC grown by pulsed vacuum arc techniques

In order to improve the adherence of DLC films, interlayers of amorphous hydrogenated carbon (a-C:H) and titanium nitride (TiN) were deposited by means of the pulsed vacuum arc technique. Bilayers were obtained by using a carbon target of 99.98% of purity in mixtures of (Ar + CH4) and (Ar + H2) for producing a-C and DLC, respectively and a target of titanium of 99.999% in a mixture of (Ar + N2) for growing TiN. After the deposition, chemical and morphological differences between TiN/DLC and a-C:H/DLC bilayers grown on silicon and stainless steel 304 were studied using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and scanning probe microscopy (SPM) techniques. XPS analysis showed a difference in sp3/(sp2+sp3) bonds ratio for each bilayer, being 0.67 for TiN/DLC and 0.45 for a-C:H/DLC bilayers. sp3 and sp2 bonds were also observed by the FTIR technique. SPM images, in atomic force microscopy (AFM) and lateral force microscopy (LFM) modes were carried out for illustrating the comparison between TiN/DLC and a-C/DLC morphologic characteristics. Roughness and grain size were studied as a function of the H2 concentration for both bilayers.