Structure analysis, mechanical property, and biocompatibility of TaOxNy thin films

•H, E, H/E of TaOxNy reach maximum with 0.3 sccm oxygen flow rate (O:N = 1:2).•Roughness of TaOxNy reaches the maximum with 0.9 sccm oxygen flow rate (O:N = 1:1).•Grain size also reaches the maximum with 0.9 sccm oxygen flow rate (O:N = 1:1).•Biocompatibility is mainly related to roughness but other factors cannot be ruled out.•Except TaON or Ta2O5, TaOxNy contains individual TaN phase surrounded by Ta-oxide phase.

TaOxNy films were deposited by reactive co-sputtering with various oxygen flow rates. After deposition, the films' structural and mechanical properties were examined. Then, the samples were tested for their biocompatibility and cell viability using 3T3 cells. With the increase of oxygen flow rate, the film transformed from crystalline TaN to crystalline TaON, eventually to amorphous Ta-oxide. The film deposited with 0.3 sccm oxygen flow rate has the highest hardness (H), modulus (E), and H/E ratio due to the substitution of nitrogen atoms with oxygen without changing the crystal structure. When the film was deposited with 0.9 sccm oxygen flow rate, the grain size and surface roughness reached the maximum value. Accordingly, this film had the highest biocompatibility and cell viability, while the film with high oxygen contents showed poor cell viability due to its low roughness and surface energy. It is shown TaOxNy films with tailored properties can be obtained as a function of oxygen flow rate set during deposition.