Study on the Sensitivity of Mechanical Properties of TiN/Si3N4 Nano-structured Film to Si3N4 Layer Thickness
TiN/Si3N4纳米多层膜硬度对Si3N4层厚敏感性的研究

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.