Electro-deposition of adherent films of H2-free quality diamond-like carbon materials on SS-304 substrates using nanocrystalline SnO2 interlayer

H2-free diamond-like carbon (DLC) films are deposited on bare as well as nanocrystalline SnO2-coated stainless steel (SS) 304 substrates. SnO2 films are deposited by electrolysis of 10 mM SnCl2 solution in nitric acid medium and then subsequently heating the sample in oxygen-ambient condition. The carbon films, on the other hand, are prepared by dissociative cleavage of methanol under high DC potential of 1 kV. Deposition conditions are optimised to get the best quality films, which are characterized by Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). It has been observed that films grown on SnO2 interlayer are much more adherent when compared to those deposited on bare SS. Moreover, the quality of films on coated substrates is found to be much superior to those grown on bare SS. It is believed that the SnO2 layer acts both as protective barrier against carbon diffusion into the SS substrate and also promotes nucleation due to anchorage of CH3 and H+ radicals (necessary for growth of DLC film) onto its oxygen deficient sites.