Effect of crystallographic orientation of nanocrystalline TiN on structural, electrical and mechanical properties of TiN/NiTi thin films

Nanocrystalline TiN/NiTi thin films have been grown on silicon substrate by dc magnetron sputtering to improve the surface and mechanical properties of NiTi based shape memory alloys without sacrificing the phase transformation effect. Interestingly, the preferential orientation of the TiN films was observed to change from (1 1 1) to (2 0 0) with change in nature of sputtering gas from 70% Ar + 30% N2 to 100% N2. In present study the influence of crystallographic orientation of TiN on structural, electrical and mechanical properties of TiN/NiTi thin films was investigated systematically. A series of nanoindentations was made on NiTi and TiN/NiTi thin films at millinewton loads with a Berkovich indenter at different temperatures. TiN(2 0 0)/NiTi films were found to exhibit high hardness, high elastic modulus, and thereby better wear resistance as compared to pure NiTi and TiN(1 1 1)/NiTi films. In addition the presence of TiN(2 0 0) improves the top surface quality of NiTi films while retaining the phase transformation effect.