Microstructure, mechanical properties, and wetting behavior of Si-C-N thin films grown by reactive magnetron sputtering

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Silicon-carbon-nitride (Si-C-N) thin films were deposited by reactive magnetron co-sputtering of C and Si targets in a mixed Ar/N2 discharge. Films were grown to a thickness of more than 0.5 μm on graphite and Si(001) substrates held at a negative floating potential of ~ - 35 V, and substrate temperature between 100 and 700°C. The total pressure was constant at 0.4 Pa (3 mtorr), and the nitrogen fraction in the gas mixture was varied between 0 and 100%. As-deposited films were analyzed with respect to composition, state of chemical bonding, microstructure, mechanical properties, and wetting behavior by Rutherford backscattering spectroscopy (RBS), energy dispersive spectroscopy (EDS), X-ray photoelectron spectrometry (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), nanoindentation and contact angle measurements, respectively. Depending on the deposition condition, ternary SixCyNz films within the composition range 1 ≤ x ≤ 34 at.%, 34 ≤ y ≤ 81 at.%, and 16.5 ≤ z ≤ 42 at.% were prepared with a textured, amorphous-to-graphite-like microstructure. For Si-C-N films with low Si content, C-C, C-N and Si-C bonds were present. At higher Si content, N preferentially bonds to Si, while less C-N bonds were observed. Films containing more than ~ 12 at.% of Si contained widely dispersed crystallites, 2-20 nm in diameter. Incorporation of a few at.% Si resulted in a dramatic reduction of the film surface energy compared to pure CN films. The measured contact angles using distilled water and glycerol liquids were for some films comparable with those on a polytetrafluoroethylene (PTFE), Teflon® surface. The hardness of Si-C-N films could be varied over the range 9-28 GPa. © 2001 Elsevier Science B.V. All rights reserved.

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