Oxidation Resistance of Ti--Si--N and Ti--Al--Si--N Films Deposited by Reactive Sputtering Using Alloy Targets

Ti--Si--N and Ti--Al--Si--N films, which possess high hardness due to the formation of a nanocomposite structure in the films, were deposited by reactive magnetron sputtering using alloy targets and then postannealed in air at temperatures ranging from 300 to 800 °C. The hardness of both the films decreased significantly as postannealing temperature increased. However, the hardness of Ti--Al--Si--N films postannealed up to 500 °C remained at more than 30 GPa, which was significantly higher than that of the Ti--Si--N films after the post annealings. Electron probe microanalyses and X-ray photoelectron spectroscopy revealed that Al 2 O 3 phases were formed in the postannealed Ti--Al--Si--N films. Transmission electron microscopy with energy-dispersive X-ray analysis showed that the Al 2 O 3 layer of the postannealed Ti--Al--Si--N films was formed 40 nm below the surface, whereas the depth of the TiO 2 --SiO 2 layer of the postannealed Ti--Si--N films was 100 nm from the surface. These results indicate that Al 2 O 3 phases existed at the surface of the Ti--Al--Si--N films and prevented the oxidation of the interior of the films during postannealing at high temperatures in air.