Microstructure and nanoindentation hardness of Ti/TiN multilayered films

Ti/TiN multilayered films were deposited by a reactive magnetron sputtering method using a combination of a Ti target and an Ar–N2 mixture discharge gas. The microstructure and nanoindentation hardness was characterized by various methods. The experimental results indicated that the hardness of multilayered film depends on both the modulation period and the thickness ratio between Ti and TiN layers λTi/TiN. The hardness was considerably enhanced when the modulation period was in the range 35–60 nm for λTi/TiN=1:1 and it was up to 23 GPa. For λTi/TiN=1:3, the hardness enhancement appears in the films with the modulation period of 20–70 nm. The possible mechanism responsible for the modification of the hardness and periods of films is also discussed.