Accurate determination of Young's modulus and Poisson's ratio of thin films by a combination of acoustic microscopy and nanoindentation

Abstract

Advances in nanoindentation technology have allowed easier and more accurate measurement of surface hardness and Young's modulus of thin films and multilayers. The error associated with a poorly defined contact area has been reduced by more sophisticated modelling. This includes the introduction of the gamma correction factor [J. Mater. Res. 14 (1999) 2296], which compensates for the elastic–plastic contact in real materials. Acoustic microscopy can also be used for the measurement of near surface modulus of thin films. However, both techniques are dependent on accurate appraisal of Poisson's ratio in order to calculate Young's modulus. Therefore, experimental determination of Young's modulus by both techniques was compared graphically against Poisson's ratio. Intersection of the acoustic curve with the nanoindentation curve for fused silica provided an accurate appraisal of Young's modulus and Poisson's ratio. Results for the TiN/NbN multilayer were less conclusive and further investigation on the effect of the substrate on both techniques needs to be performed.