Mechanical Properties, Biocompatibility and Antibacterial Behaviors of TaO_0.2N_0.8 and TaO_0.2N_0.8-Ag Nanocomposite Thin Coatings

TaO_{x = 0.2}N_{y = 0.8} was reported previously to have the highest modulus (E), hardness (H), and H to E ratio attributed to the embedment of substituting oxygen atoms in the TaN crystal structure, among some TaOxNy coatings studied. In the present study, TaO_0.2N_0.8-Ag nanocomposite coatings were fabricated by reactive multi-target sputtering with O/N ratio adjusted to the expected value. The various Ag contents were doped to induce antibacterial behaviors. After deposition and annealing with rapid thermal process (RTP) at 400 °C for 4 min, the coatings’ mechanical and structural properties were studied. After these examinations, the samples were then studied for their cell attachment, cell viability, and biocompatibility with 3-T-3 cells, as well as for their antibacterial behaviors against Escherichia coli. It appeared that hardness and crack resistance could be improved further with suitable amount of Ag doped to the coatings, followed by rapid thermal annealing treatment. The coating with 1.5 at. % Ag had the highest hardness and good H/E ratio. It was also found that the antibacterial efficiency of TaO_0.2N_0.8-Ag coatings could be much improved, comparing with that of TaO_0.2N_0.8 coatings. The antibacterial efficiency increased with the increased Ag contents. There was no negative effect of Ag on the biocompatibility of TaO_0.2N_0.8-Ag. Through the cell attachment and viability testing using MTT(3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, it can be summarized that surface roughness could be the dominating factor for cell viability and attachment, which means the improvement of biocompatibility. Accordingly, the samples with 1.5 at. % and 11.0 at. % Ag show the best biocompatibility. The variation of surface roughness was affected by the incorporation of Ag and oxygen atoms after rapid thermal annealing.