Crystallization of Si3N4 and superhardness effect of ZrN/Si3N4 nano-multilayers

The crystallization behavior of Si 3 N 4 modulation layers in the multilayers and its influences on the microstructure and mechanical properties of ZrN/Si 3 N 4 multilayers were studied. ZrN/Si 3 N 4 multilayers with different Si 3 N 4 thickness were synthesized by reactive magnetic sputtering. The microstructure of the multilayers was characterized with X-ray diffraction and high-resolution transmission electron microscopy, and a nanoindentor was introduced to measure their mechanical properties. The results show that when the thickness is less than 0.9 nm, Si 3 N 4 , normally amorphous in the deposited state, could form a NaCl-type pseudocrystal structure due to the template effect of ZrN crystal layer. Crystallized Si 3 N 4 layers and ZrN template layers grow epitaxialy into columnar crystals. Correspondingly, the hardness of the films was enhanced, showing a superhardness effect. Further increasing Si 3 N 4 layer thickness, the coherent interfaces of the multilayers were damaged and Si 3 N 4 layers become amorphous, accompanied by the decline in the hardness of the films.