Kind of oxide-composed superhard nanomultilayer prepared by magnetron sputtering

Ti N ∕ Si O 2 nanomultilayers with various modulation layer thicknesses were prepared by multi-target magnetron sputtering method. The composition, growth structures, and mechanical properties of the nanomultilayers were studied by energy dispersive x-ray spectrometry, x-ray diffraction, scanning electron microscope, high-resolution transmission electron microscope, and nanoindenter. The results reveal that although SiO2 and TiN monolithic films formed amorphous and nanocrystalline structures, respectively, the TiN∕SiO2 nanomultilayers crystallized entirely and grew coherently at smaller SiO2 layer thickness (<∼1nm), and columnar crystals with (111) preferred orientation were formed. Correspondingly, the multilayers show superhardness and high elastic modulus with maximum values of 44.5 and 473GPa, respectively. With the further increase of layer thickness, SiO2 layers formed an amorphous structure and blocked the coherent growth of the multilayers, and then the hardness and elastic modulus decreased gradually. On the other hand, the increase of TiN layer thickness caused the hardness and elastic modulus of the multilayers to decrease slightly. However, a high hardness of 38GPa can still be obtained even when TiN layer thickness increases to 8.8nm.