Nanostructural and mechanical properties of nanocomposite nc-TiC/a-C:H films deposited by reactive unbalanced magnetron sputtering

Zehnder, T.; Schwaller, Patrick; Munnik, F.; Mikhailov, S.; Patscheider, J. (2004). Nanostructural and mechanical properties of nanocomposite nc-TiC/a-C:H films deposited by reactive unbalanced magnetron sputtering Journal of Applied Physics, 95(8), pp. 4327-4334. American Institute of Physics (AIP) 10.1063/1.1650898

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Thin films of nc-TiC/a-C:H nanocomposite have been deposited by reactive magnetron sputtering at substrate bias values of −240 and −91 V. The grain size and grain separation, which together define the nanostructure, are correlated to the amount of the amorphous phase. From the size of the TiC grains measured by x-ray diffraction and the amorphous hydrogenated carbon (a-C:H) phase content determined by x-ray photoelectron spectroscopy, the mean grain separation is estimated using a simple model for the nanostructure. Films deposited at −240 V show a hardness enhancement for a-C:H phase contents in the range 10% to 30% with TiC grain sizes around 5 nm. The mean grain separation for such films was estimated to be 0.3 nm. Films with higher a-C:H phase contents still have 5 nm small grains, but their mean grain separation is larger than 0.5 nm; their hardness is thus determined by the properties of the amorphous matrix. A less pronounced hardness enhancement is observed for films deposited at −91 V. They have larger grains and larger mean gain separations and show smaller hardness values. The hardness of the films, among other mechanical properties, is controlled by the nanostructure. Raman measurements have shown that a-C:H is present in films with mean grain separation down to 0.2 nm. Coefficients of friction against steel lower than 0.3, independent of the substrate bias, are found for films with mean grain separations as low as 0.15 nm. Self-lubrication due to a-C:H can explain the observed friction behavior, although the presence of a-C:H cannot be proved by Raman spectroscopy for films with mean grain separations smaller than 0.2 nm. It is shown that the substrate bias is crucial in obtaining increased hardness of nc-TiC/a-C:H nanocomposite thin films. In contrast to the hardness of the coatings, their friction behavior is not affected by the substrate bias.

Item Type:	Journal Article (Original Article)
Division/Institute:	School of Engineering and Computer Science > Institute for Surface Applied Laser, Phototonics and Surface Technologies ALPS School of Engineering and Computer Science
Name:	Zehnder, T.; Schwaller, Patrick; Munnik, F.; Mikhailov, S. and Patscheider, J.
ISSN:	0021-8979
Publisher:	American Institute of Physics (AIP)
Language:	English
Submitter:	Patrick Schwaller
Date Deposited:	10 Dec 2019 07:57
Last Modified:	10 Dec 2019 07:57
Publisher DOI:	10.1063/1.1650898
URI:	https://arbor.bfh.ch/id/eprint/9268