DFT calculations and experiments of oxidation resistance research on B, N, and Si multi-doped diamond films

The oxidation resistance of diamond films is essential in maintaining their good performance in high-temperature applications. Although numerous experiments have proved that doping can improve diamond films' oxidation resistance properties, the theoretical explanation still needs to be discussed. In this study, the density functional theory (DFT) method is used to elucidate the influence mechanism of multiple doping, including B, N, and Si elements doping, on the oxidation resistance of diamond films and obtain the doped diamond films with the optimal oxidation resistance. These include the confirmation of the different doped diamond (1 1 1) models, the adsorption site of the O atoms on the various doped diamond surfaces, and the subsequent reaction process of O2 molecules with the C atom. The results show that the multi-doped diamond model has the most considerable activation energy due to the synergistic effect of the three elements, which represents better oxidation resistance properties. In addition, eight kinds of diamond films are fabricated on the silicon substrate. Their weight loss at high temperatures is conducted to evaluate oxidation resistance, indicating that multiple doping can effectively reduce the high-temperature oxidation rate of diamond films, and the experimental results are consistent with the theoretical calculations.