Oxidation behavior of sputtered CrN/AlN multilayer coatings during heat treatment

CrN/AlN multilayer coatings with modulation periods of 4 nm and 20 nm were fabricated on silicon (001) substrates by RF magnetron sputtering technique. The modulation periods of the multilayer coatings was evidenced by transmission electron microscopy (TEM). To evaluate the oxidation behavior of CrN/AlN multilayer coatings, the CrN and CrN/AlN coatings were annealed at elevated temperatures ranging from 500 °C to 900 °C in air for 1 h. For the multilayer CrN/AlN with the modulation period of 4 nm, no oxide peak was revealed in the XRD spectra, yet amorphous oxide layer was visible at 900 °C. It exhibited better anti-oxidation behavior than either the monolayered CrN or multilayered CrN/AlN coating with modulation period of 20 nm. Furthermore, the microstructure of the CrN/AlN coatings exhibited a dense columnar structure and the surface roughness of the multilayer coating retained below 5 nm, which was much smoother than that of CrN coating at 800 °C.