The oxidation process of NiSi_x film at high temperature in air and the antioxidant effect of SiO_xN_y/NiSi_x film

The NiSi_x film was deposited onto the quartz substrates by the direct current pulsed magnetron sputtering technique. With the increase of annealing temperature from 100 to 800 °C in air, the NiSi_x films with different properties were obtained. The characterization by Hall effect system showed that the electrical property of NiSi_x film was abrupltly deteriorated at the annealing temperature over 500 °C in air. The characterization by X-ray diffraction (XRD) system showed that the oxidation of Ni in NiSi_x film started and completed at the temperature of 400 and 600 °C in air, respectively. The scanning electron microscopy resuls showed that the oxidation of NiSi_x film started at the pin-holes/defects on film surface, and then diffused to the whole film. In order to avoid the oxidation of NiSi_x film at high temperature in air, the SiO_xN_y film was deposited onto the NiSi_x film by the same technique. The XRD results showed that the dense SiO_xN_y film could prevent the NiSi_x film from the oxidation at temperature of 800 °C in air. With the SiO_xN_y film, the NiCr_x–NiSi_x film thermocouple could normally service at temperature of 800 °C in air.