Plasma enhanced chemical vapour deposition of silica onto titanium: Analysis of surface chemistry, morphology and hydroxylation

We have been developing and characterising a procedure for the deposition of thin silica films by a plasma enhanced chemical vapour deposition (PECVD) procedure using tetraethoxysilane (TEOS) as the main precursor. The silica coatings were used for improving the corrosion resistance of metals and as bioactive coatings on biomedical metallic implants. We have improved the PECVD method for producing high quality and reproducible PECVD-silica (PECVD-SiO2) coatings on metals, primarily for biomaterial applications. In order to understand the interaction of the PECVD-SiO2 coatings with biological species (such as proteins and cells), it is important to first analyse the properties of the silica films deposited using the optimised parameters. Therefore, the work presented and discussed in this paper was carried out to analyse the characteristic features of PECVD-SiO2 deposited on titanium (Ti) substrates (PECVD-SiO2-Ti). We determined that the PECVD-SiO2 coatings on Ti were conformal to the substrate surface, strongly adhered to the underlying substrate and were resistant to delamination. The PECVD-SiO2 surface was composed of stoichiometric SiO2, showed a low carbon content (below 10 at.%) and was very hydrophilic (contact angle <10°). Finally, we also showed that the PECVD-Si coatings contain surface hydroxyl groups.