Incorporation of Si and SiOx into diamond-like carbon films: Impact on surface properties and osteoblast adhesion

The interaction of human osteoblast cells with diamond-like carbon films incorporating silicon and silicon oxide (SiOx, 1 ⩽ x ⩽ 1.5) and synthesized using the direct-current plasma-activated chemical vapour deposition method was investigated. Cell culture studies were performed for films with Si contents ranging from ∼4 at.% to 15 at.%. Substantial differences between Si-incorporated and SiOx-incorporated films were found for the bonding environments of Si atoms and the hybridization of underlying carbon structures. However, osteoblast-attachment studies did not show statistically significant trends in properties of cell growth (count, area and morphology) that can be attributed either to the Si content of the films or to the chemical structure of the films. The surface energy decreased by 40% as the Si content of the SiOx incorporated DLC films increased to 13 at.%. The cell adhesion properties however did not change in response to lowering of the surface energy. The incorporation of both Si and SiOx leads to a beneficial reduction in the residual stress of the films. The average roughness of the films increases and the hardness decreases when Si and SiOx are added to DLC films. The impact of these changes for load-bearing biomedical applications can be determined only by carefully controlled experiments using anatomic simulators.