Effect of bias voltage on the properties of CeO2-x coatings prepared by magnetron sputtering

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

15 Scopus Citations
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Original languageEnglish
Pages (from-to)411-416
Number of pages6
Journal / PublicationSurface and Coatings Technology
Online published30 Nov 2016
Publication statusPublished - 15 Oct 2017


In this study, cerium oxide (CeO2-x) coatings were deposited onto silicon substrates by reactive unbalanced magnetron sputtering in an Ar-O2 gas mixture. The effect of substrate negative bias voltage on the surface morphology, wetting behavior, microstructure, mechanical and tribological properties of CeO2-x coatings were systematically investigated. It was found that the surface morphology and the root mean square (RMS) roughness of the coatings exhibited a non-linear evolution. The smoothest surface with a RMS roughness of about 3.3nm was obtained at a bias voltage of -60V. All deposited coatings exhibited a hydrophobic feature with the water contact angle around 100°, which was close to the value obtained from Teflon surface. X-ray diffraction (XRD) analyses revealed the best crystallinity of CeO2-x coatings in cubic CeO2 phase at a critical value of -80V bias. Cross-sectional scanning electron microscope (SEM) images displayed typical columnar-type structures with a relatively large column grain for the coating deposited at -20V and a dense, fine-grained microstructure obtained at -80V. The microstructure improvement at the optimized bias (-80V) contributed further to the enhancement in the hardness, reaching a maximum value of ~18.0GPa. The average friction coefficients of as-deposited coatings prepared between -40 and -120V were measured to be around ~0.40, whereas the coating prepared at -80V showed the best anti-wear performance. The wear volumes were two orders of magnitude lower than that of 316 stainless steel (SS) and three orders of magnitude lower than that of Teflon.

Research Area(s)

  • Anti-wear, Bias voltage, CeO2−x coatings, Magnetron sputtering, Microstructure, Wetting behavior