Nanomechanical properties of copper thin films on different substrates using the nanoindentation technique

The nanoindentation technique is used to measure the hardness and Young's modulus of copper thin films with substrates of Si, SiO2 and LiNbO3. The results show that in all instances with increasing applied load the penetration depth increases while the hardness at first decreases, and then slowly approaches different constant values depending on the effect of the substrate. The hardness of the film with a LiNbO3 substrate is the highest and that of a film with a Si substrate is the lowest under the same load. The obtained values of the hardness and the Young's modulus of the copper films are compared with previous data, which show that the values obtained from this study are reasonable. The ratio of the critical depth to the film thickness for copper film is about 1:8 and this is also compared with that of different materials obtained by previous researchers. The relationship between the Young's modulus and the hardness for a film is also derived. From this relationship, it can be found that the Young's modulus increases with increasing hardness for different composite materials and shows different increasing ratios under different applied loads. For any given hardness, the modulus value of the Cu him on LiNbO3 is the highest and that of the film on Si is the lowest. (C) 2003 Elsevier Science B.V. All rights reserved.