SiO2层晶化对TiN/SiO2纳米多层膜结构和性能的影响

采用多靶磁控溅射法制备了一系列具有不同SiO2调制层厚的TiN/SiO2纳米多层膜.利用X射线衍射、X射线能量色散谱、扫描电子显微镜、高分辨电子显微镜和微力学探针表征和研究了多层膜的生长结构和力学性能.结果表明,具有适当厚度(0.45～0.9 nm)的SiO2调制层,在溅射条件下通常为非晶态,在TiN层的模板作用下晶化并与TiN层共格外延生长,形成具有强烈(111)织构的超晶格柱状晶多层膜;与此相应,纳米多层膜产生了硬度和弹性模量异常增高的超硬效应(最高硬度达45 GPa).随着SiO2层厚度的继续增加,SiO2层转变为非晶态,阻断了多层膜的共格外延生长,使纳米多层膜形成非晶SiO2层和纳米晶TiN层的多层结构,多层膜的硬度和弹性模量逐渐下降.

The effects of crystallization of SiO2 layers on the growth structure and mechanical properties of TiN/ SiO2 nanomultilayers

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.