Microstructure evolution and indentation cracking behavior of MoN multilayer films

Abstract

Molybdenum nitride, MoN, multilayer films tailored by MoN single layers with versatile structure features are produced through radio frequency magnetron sputtering technique. The MoN layers were manipulated to exhibit crystalline (C), preferred orientation (P) and amorphous (A) phases with gas inlet and input power control. The MoN multilayer films were successfully prepared using alternatively stacking of single layers to form C/P, C/A, and P/A assemblies, i.e. MCP, MCA, and MPA films respectively. The multilayer coatings were controlled at a total thickness of 1 μm with each building layer of 50 nm. Through microstructure analyses, the columnar crystalline structure in single layer films was suppressed by tailored layers. Intact heterostructural interfaces with building layers at early deposition stages could be observed for crystalline incorporated multilayers, like MCP and MCA assemblies. On the other hand, the continuous columnar crystalline structure could be found in multilayers containing amorphous layers, which tended to be pliant to the crystalline phases and preferred orientation during deposition. The columnar grains grew through several layer interfaces in late deposition stages for multilayers, especially for MPA film. Through Rockwell C indentation test, adhesion and cracking behaviour of the single and multilayer MoN films were evaluated. The structure tailored MoN multilayers showed better adhesion as compared to the single layer films. Adhesive cracking due to preferred orientation was suppressed by the tailoring structure with crystalline layers.