通过反应磁控溅射制备了一系列不同Si3N4层厚的TiN/Si3N4纳米多层膜,利用X射线衍射仪、高分辨透射电子显微镜、扫描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,研究了其力学性能随Si3N4层厚微小改变而显著变化的原因。结果表明,在TiN调制层晶体结构的模板作用下,溅射态以非晶存在的Si3N4层在其厚度小于0.7 nm时被强制晶化为NaCl结构的赝晶体,多层膜形成共格外延生长的(111)择优取向超晶格柱状晶,并相应产生硬度显著升高的超硬效应,最高硬度达到38.5 GPa。Si3N4随自身层厚进一步的微小增加便转变为非晶态,多层膜的共格生长结构因而受到破坏,其硬度也随之降低。
A series of TiN/Si3N4 nano-multilayers with different Si3N4 modulation thickness were reactively deposited by magnetic sputtering in order to study the sensibility of mechanical properties of TiN/Si3N4 multilayers on the change of Si3N4 thickness. The microstructure of the multilayers was characterized with X-ray diffraction, high-resolution transmission electron microscopy and scanning electron microscopy. A nanoindentor was introduced to measure the mechanical properties. Results show that when the thickness is less than 0.7 nm, Si3N4, normally amorphous in deposition state, could form a NaCl-type pseduocrystal structure due to the template effect of TiN crystal layer. Crystallized Si3N4 layers and TiN template layers grow coherently into columnar crystals with (111) preferred orientation. Correspondingly, the hardness of the films was enhanced to a maxim value of 38.5 GPa, showing a superhardness effect. Further increasing Si3N4 layers thickness, the coherent interfaces of the multilayers were damaged and Si3N4 layers become amorphous, accompanying by the decline in the hardness of the coatings.
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