Mechanical characterization for β-Sn single crystals using nanoindentation tests

Depth-sensing nanoindentation tests were made on β-Sn single crystals having different growth directions. The indentation load-displacement curves of the samples were obtained under different peak loads ranging from 10 to 50 mN. The most commonly used Oliver–Pharr method was used to analyze the unloading segments of these curves. It was found that the dynamic nanohardness (Hd) and reduced elastic modulus (Er) exhibited significant peak load dependence. The observed size dependence of the Hd was rationalized using classical Meyerʹs law, Proportional Specimen Resistance (PSR) and the Modified Proportional Specimen Resistance (MPSR) model. Reduced elastic modulus-indentation test load curves exhibited distinct transition to a plateau of constant Er. It can be concluded that the transition in such curves correspond to the intrinsic Er value of the examined materials. The examined single crystals also exhibit pop-in phenomenon attributed to the onset of dislocation nucleation activity underneath the indenter.