Physical properties of a:DLC films and their dependence on parameters of deposition and type of substrate

In this paper, nanostructure and nanohardness studies using atomic force microscopy (AFM) were made in order to investigate the initial process of growth of diamond-like carbon DLC films on substrates (silicon, sapphire and germanium). The deposited amorphous diamond-like carbon (a:DLC) films on substrates of silicon and sapphire, of roughness (sigma) similar to 1 nm, using the optimum deposition parameters of pressure, RF power and thickness, have not produced any significant changes of sigma. A granulation structure was formed which remained practically the same as that of the substrate, but the height of the granules increased. This showed that in this case (very small sigma), the incident carbon atoms on these substrates are captured on the height of the granules, which increased it. For the germanium substrates, with larger roughness (sigma greater than or equal to 10 nm), the deposition of a:DLC films, decrease the value of a, producing a smoother surface (decrease of the granulation height). From Raman shift spectroscopy, microhardness, Auger electron spectroscopy and FTIR measurements data, indicating that the incident carbon atoms on the silicon substrates give a:DLC, with a ratio of bonds p(3)/p(2)congruent to 50% were obtained. Measurements of nanohardness using AFM, have shown that two types of granulation of different average height profile (AHP) inside cluster shaped structures, appear. The clusters with granulation of higher AHP have a higher sp(3)/sp(2) ratio than those of low AHP. This result may enable further improvement of the parameters of deposition and, as a consequence, enable the uniform deposition of a:DLC, with large sp(3)/sp(2) on large surfaces. (C) 1999 Elsevier Science S.A. All rights reserved.