Investigation of nanoindentation on Co/Mo multilayers by the continuous stiffness measurement technique

The mechanical properties of evaporated Co/Mo multilayers with periodicity of 4-16 nm were investigated. The microstructures of the films were analyzed using X-ray diffraction and transmission electron microscopy. Continuous stiffness measurement technique was used in the nanoindentation tests to determine the hardness and elastic modulus of the films. A Hall-Petch-like behavior is observed in the Co/Mo multilayers, in which the fitting parameter n is found as large as 0.93. Other possible mechanisms are also proposed to explain this behavior. The peak hardness, approximately 2.1 times of the rule-of-mixtures value is obtained for the periodicity of 7 nm. When the periodicity is reduced to 4 nm, a hardness decrease observed is attributed to the interface alloying.