Nanoindentation investigation of Ti/TiN multilayers films

The hardness of Ti/TiN nanolaminated films is investigated in this study. M onolithic Ti and TiN films and Ti/TiN multilayers were deposited on silicon substrates by radio-frequency sputtering. The period thickness of multilay ers was decreased from 20 to 2.5 nm. Grazing x-ray reflectometry showed tha t the modulation of composition of Ti/TiN multilayers exists for all the pe riod thickness considered. From nanoindentation measurements, we determined the hardness and Young's modulus of multilayers. Hardness increased with d ecreasing period thickness to go beyond the rule-of-mixture value for sampl es with period thickness of Lambda less than or equal to 5 nm. The maximum hardness, 1.6 times higher than the value obtained by the rule of mixture, is obtained for Lambda=2.5 nm. Our results are compared to a dislocation-ba sed model previously introduced by Lehoczky. (C) 2000 American Institute of Physics. [S0021-8979(00)09411-1].