Abstract: A series of AlN/SiO₂ nano-multilayers with different individual SiO₂ layer thicknesses were prepared by reactive magnetron sputtering. The microstructure and mechanical properties of these multilayers were studied by X-ray diffraction, high-resolution transmission electron microscope, scanning electron microscope and nanoindentation. The influence of SiO₂ layer thickness on the microstructure and mechanical properties of AlN/SiO₂ nano-multilayers was studied, and the high temperature oxidation resistance was investigated. The SiO₂ layer is usually amorphous under sputtering condition. Results show that when its thickness is less than 0.6nm, the SiO₂ layer is forced to crystallize into hexagonal pseudocrystal structure and grows epitaxially with AlN, and the multilayers exhibit superhardness effect. With a further increase in its layer thickness, SiO₂ layer transforms into amorphous structure and blocks the coherent growth of multilayers, accompanied with a decline in the film hardness. The results of high temperature annealing test indicate that the oxidation resistance temperature for AlN/SiO₂ nano-multilayers with high hardness is up to 800℃, equivalent to that for the AlN monolayer.
The addition of SiO₂ layer can improve the hardness of multilayers, but it will not remarkably improve the high temperature oxidation resistance of films.

Key words: AlN/SiO₂ multilayer, epitaxial growth, superhardness effect, oxidation resistance