Si- and W-containing a-C films were deposited by dual magnetron sputtering onto polished silicon wafers. A DC source was used for carbon sputtering, and a composite RF source was applied for sputtering the Si and W additives. For comparison, carbon, silicon and C-Si films were deposited in separate experiments, using a similar source arrangement. The chemical composition and the bonding states of the constituent elements were characterised by X-ray photoelectron spectroscopy and X-ray induced Auger electron spectroscopy. Mechanical properties (dynamic hardness and reduced modulus) were estimated by using depth-sensing nanoindentation.
The silicon content of the C-Si films varied between 20-40 atomic %, depending on the applied source power. The tungsten content in the C-Si-W films varied between 25-50 atomic % while the silicon content at the same time was between 25-0 atomic %. Despite a slight surface oxidation, the oxygen content of the films was insignificant, typically below 3 atomic %. Predominant C-Si and C-W chemical bonds could be identified by the chemical shifts of the XP spectra and by the Auger parameters.
The values of nanohardness and reduced modulus for the silicon substrate were 10 GPa and 127 GPa, respectively, while those for the deposited layers were much higher: for the a-C film the corresponding values reached 16 GPa and 155 GPa, for the C-Si films 13-16 GPa and 140-185 GPa and for the C-Si-W films 12-19 GPa and 160-210 GPa, depending on the actual chemical composition.
This work was supported by the National Scientific Research Fund through the project OTKA T-043359.
Keywords: DLC-Si-W, nanocomposite, XPS, Auger parameter, nano-hardness, reduced modulus

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