The effects of crystallization of SiO2 layers on the growth structure and mechanical properties of TiN/ SiO2 nanomultilayers
SiO2层晶化对TiN/SiO2纳米多层膜结构和性能的影响

Superhard and oxide-composed multilayered coatings are promising for cutting tools working under extreme conditions. In this paper, TilM/SiO2 nanomultilayers with different SiO2 layer thicknesses have been prepared by multi-target magnetron sputtering method. The growth, structure and mechanical properties of the nanomultilayers have been studied by X-ray diffraction, energy dispersive X-ray spectrometry, scanning electron microscopy, high-resolution transmission electron microscopy and nanoindentation, respectively. The results reveal that amorphous SiO2 which is more favorable under sputtering condition crystallizes at smaller SiO2 layer thickness (0.45-0.9 nm) due to the template effect of TiN layers, and multilayers exhibit coherent epitaxial growth with intensive (111) texture. Correspondingly, the multilayers show anomalous enhancement in hardness and elastic modu- lus, and the maximum hardness reaches 45 GPa. At larger layers thickness (>-1 nm), however, SiO2 layers form amorphous structure and block the coherent growth of multilayers, resulting in a layered structure that consists of amorphous SiO2 and nanocrystalline TiN layers. The hardness and elastic modulus decrease gradually with increasing SiO2 layers thickness.