Suppression of pesting failure in MoSi2 film by doping of Si

MoSi2 usually suffers pesting failure at 400– 700 °C due to severe oxidation of Mo, which has been a great hindrance for industrial applications. To address this issue, this work grew MoSi2(Si) thin films via magnetron co-sputtering of a Si single element target and a MoSi2 compound target on Si wafer substrates at room temperature, followed by annealing at 950 °C in an argon atmosphere. The as-annealed thin films were heated in a muffle furnace at 700 °C in air to experience different duration of oxidation. After that, the oxidation resistance was evaluated by examining the thickness, morphology, structure and composition of the as-heated thin films using field emission scanning electron microscopy and X-ray diffraction, respectively. In comparison with the MoSi2 without doping of Si, the MoSi2(Si) film is denser and exhibits a C11b crystalline structure with a smaller crystal size of 30 nm. The oxidation of Mo is effectively inhibited. There is no big bulge on the film surface after 1 h oxidation. But the oxidation of Si is severe, resulting in the continuous growth of grey SiO2 layer which help preventing the further oxidation of Mo. SiO2 islands are observed after oxidation for 9 h. The early pesting sites gradually become healed by the grown SiO2 layer during oxidation for 60 h. The mechanism for suppressing the pesting failure of MoSi2 by Si doping is discussed in details. A model is developed to explain the process.