Pop-in events induced by spherical indentation in compound semiconductors

Details of the elastic-plastic transitions in crystalline compound semiconductors have been examined using spherical indentation. Two cubic (InP and GaAs) and two hexagonally structured semiconductors (ZnO and GaN) have been studied. A series of indentations have been made in each material at a number of different loads. The resulting load-penetration curves exhibited one or more discontinuities on loading (so called pop-in events). The load at which the initial pop-in event occurred has been measured along with the corresponding indenter extension. The elastic and elastic-plastic response of each material to spherical indentation has been calculated and compared with the experiment. By taking the difference between the elastic and elastic-plastic penetration depths, it has been found that the pop-in extension at each load could be predicted for each material. The detailed deformation behavior of each of the materials during indentation has also been discussed.