Investigation on indentation scaling relationships of ITO thin films considering the indenter tip rounding defect

Abstract

To improve the applications of indium tin oxide (ITO) films, higher measurement requirements are implemented due to the significant effects of more complicated stress states and limitations of testing conditions on the mechanical properties. In this work, the effect of the tip bluntness on indentation responses and scaling relationships for film/substrate composite systems is investigated via finite-element (FE) simulations and dimensional analysis. A novel indentation method is proposed to measure the intrinsic elastic modulus of thin films based on the scaling relationship among the curvature of the loading segment in P-h curves and material properties. FE simulations indicate the significant effect of tip bluntness on indentation responses. However, the curvature is essentially independent of the dimensionless parameter of h_m/t. Furthermore, the tilt effect during the direct calibration procedure is corrected through spatial mapping transformation of atomic force microscopy data. Herein, the measured tip rounding radius fitted by 2D profile and 3D topography are 70 ± 4.8 nm and ∼72.83 nm, respectively. The indentation data acquired with the actual Berkovich indenter are used to verify the scaling relationships. The elastic modulus of ITO films is calculated as ∼135.26 GPa, and the measured error is only ∼3.59 %.