TiN/SiO_2纳米多层膜的晶体生长与超硬效应

Study on the growth and superhardness of TiN/SiO_2 nanomultilayers

高硬度的含氧化物纳米多层膜在工具涂层上具有重要的应用价值 .研究了TiN SiO2 纳米多层膜的晶体生长特征和超硬效应 .一系列具有不同SiO2 和TiN调制层厚的纳米多层膜采用多靶磁控溅射法制备 ;采用x射线衍射、x射线能量色散谱、高分辨电子显微镜和微力学探针表征了多层膜的微结构和力学性能 .结果表明 ,虽然以单层膜形式存在的TiN和SiO2 分别形成纳米晶和非晶结构 ,它们组成多层膜时会因晶体生长的互促效应而呈现共格外延生长的结构特征 .在SiO2 调制层厚度约小于 1nm时 ,多层膜呈现强烈的 (111)织构 ,并伴随着硬度和弹性模量的显著上升 ,最高硬度和弹性模量分别达到 4 4 5和 4 73GPa .进一步增加SiO2 层的厚度 ,由于SiO2 层呈现非晶态 ,多层膜的共格外延生长受到抑制 ,硬度也相应降低 .TiN调制层厚度的改变虽对多层膜的生长结构和力学性能也有影响 ,但并不明显 .

Superhard and oxide-composed multilayers are promising coatings for tools working under extreme conditions. In this paper, TiN/SiO2 nanomultilayers with various individual SiO2 and TiN layer thicknesses have been prepared by multi-targets magnetron sputtering method. The growth structure and mechanical properties of the films have been studied by x-ray diffraction, energy dispersive x-ray spectrometry, high-resolution transmission electron microscope and nanoindenter. It reveals that although SiO2 and TiN monolithic films form amorphous and nanocrystalline structures, respectively, the TiN/SiO2 multilayers exhibit coherent epitaxial growth due to the mutual growth-promoting effect. At small SiO2 layer thickness (< similar to 1 nm) the multilayers exhibit (111) preferred orientation and show abnormal enhancement of hardness and elastic modulus with maximum values of 44.5 and 473 GPa respectively. At larger layer thickness (> similar to 1 nm) SiO2 layers transform into amorphous structure and block the coherent growth of multilayers, and then the hardness and elastic modulus of the multilayers decrease gradually with increasing SiO2 layer thickness. On the other hand, the changing of TiN layer thickness shows a relatively small effect on the growth structure and mechanical properties of the nanomultilayers.