Correlation between Tribological Properties, sp²/sp³-Ratio and H-Content of Low-Wear Diamond-Like Carbon (DLC) Layers

Abstract:

It has been established that hardness and density of diamond-like carbon (DLC) layers can be raised by increasing ion energy during deposition, decreasing H-content and by increasing sp³-fraction. To confirm differences in hydrogen content of hydrogen containing and hydrogen free DLC films deposited at different bias voltages, layers were etched in oxygen atmosphere in a capacitively coupled plasma device. By employing real-time ellipsometry measurements, the H-content of the hydrogen containing a-C:H layers were estimated by determining the optical constants n and k (n-real part and k-imaginary part of the refractive index). In addition, DLC layers were analyzed by X-ray photoelectron spectroscopy to estimate the ratio of sp^²- and sp^³-hybridization. The mechanical and tribological properties of the coatings were evaluated by means of nanoindentation and ball-on-disc-tests. Finally correlations between these properties, H-content and sp³/sp²-ratio were obtained in an effort to explain different tribological behaviors of DLC-layers.

• Periodical: Materials Science Forum (Volumes 706-709)
• Pages: 2596-2601
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.706-709.2596
• Online since: January 2012
• Authors: E. Vogli, Fabian Hoffmann, E. Bartis, G. S. Oehrlein, Wolfgang Tillmann
• Keywords: Diamond-Like Carbon (DLC), DLC, Ellipsometry, Hydrogen Content, Sp²/Sp³-Ratio, XPS

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