TiN／Si_3N_4纳米多层膜硬度对Si_3N_4层厚敏感性的研究

STUDY ON THE SENSITIVITY OF HARDNESS OF TiN/Si_3N_4 NANO-MULTILAYERS TO Si_3N_4 LAYER THICKNESS

通过反应磁控溅射制备了一系列不同Si_3N_4层厚的TiN/Si_3N_4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硬度,研究了其硬度随Si_3N_4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Si_3N_4层在其厚度小于0．7nm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．Si_3N_4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．

TiN/Si3N4 nano-multilayers with different Si3N4 modulation thicknesses were reactively deposited by magnetic sputtering in order to study the sensibility of hardness of TiN/Si3N4 multilayers on the change of Si3N4 thickness. The microstructure of the multilayers was characterized with XRD, HRTEM and SEM. A nanoindentor was introduced to measure the hardness. Results show that Si3N4, normally amorphous in deposition state, could form a NaCl-type pseudo-crystal structure due to the template effect of TiN crystal layer when the thickness is less than 0.7 nm. Crystallized Si3N4 layers and TiN template layers grow coherently into columnar crystals with {111} preferred orientation growth. Correspondingly, the hardness of the films was enhanced to a maximum 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.