Abstract:In order to study the indentation size effect (ISE) of germanium single crystals, nano-indentation experiments were carried out on the (100), (110) and (111) plane-orientated germanium single crystals. The true hardness of each crystal plane of germanium single crystals was calculated based on the Meyer equation, proportional sample resistance (PSR) model and Nix-Gao model, and the indentation size effect (ISE) factor of each crystal plane was calculated. Results show that, the germanium single crystals experience elastic deformation, plastic deformation and brittle fracture during the loading process, and the three crystal planes all show obvious ISE phenomenon. All three models can effectively describe the ISE of germanium single crystals, and the calculated value of Nix-Gao model is the most accurate. Compared with the other two crystal planes, Ge (110) has the highest size effect factor m and the highest hardness, which indicates that Ge (110) has the worst plasticity.

Key words: germanium single crystal; indentation size effect; Meyer equation; proportional sample resistance (PSR) model; Nix-Gao model