Germanium microhardness and the correlation of indentation creep with dislocation velocity

Temperature-dependent hardness of zinc-blende structured covalent materials

“…2b-d, respectively (see Fig. S3 for the temperature-dependent lattice constant, shear moduli, and Poisson's ratio) and are in good agreement with the experimental hardness values measured over a wide temperature range [1,[11][12][13][14]. In addition, the temperature-dependent Vickers hardnesses of polar covalent materials, cubic BN and SiC, are plotted in Fig.…”

“…By evaluating the dominant dislocations at different temperatures, it was found that the primary dislocation changed from shuffle-set dislocations to glide-set dislocations at this critical temperature. Moreover, the calculated transition temperatures where the shuffle-set dislocation- controlled deformation changed to a glide-set dislocation-controlled deformation (T s−g ) were 1402.6, 676.8, and 560.2 K for diamond, Si, and Ge, respectively, which are comparable to the experimental values, 1450 K for diamond [10], 650 K for Si [1], and 600 K for Ge [13]. At low temperatures, the dislocation motions caused by thermal activation can be ignored.…”

“…The Vickers hardness of diamond-structured covalent material is about 2.74 times of the yield strength [24], and the yield strength is roughly 3.1 (Taylor factor for an fcc structure) times of the critical shear stress [25]. Therefore, the temperature dependent Vickers hardness for diamond-structured covalent materials can be estimated as K for diamond, Si and Ge, respectively, which are comparable with the experimental values, i.e., 1450 K for diamond [11], 650 K for Si [1], and 600 K for Ge [15].…”

“…Experimentally, it is challenging to perform temperaturedependent hardness measurements due to the complexities in sample preparation while maintaining a stable temperature during the measurement, which usually results in substantial errors in the measured hardness values. Nonetheless, for zinc-blende structured covalent materials, an intensified softening behavior is clearly observed with increasing temperature [1,[10][11][12][13][14]. Using parameters fitted from the experimental data, formulas have been developed to understand this softening behavior [1,15].…”

The relationship of time-dependent hardness and scratch hardness

“…Scratch hardness and time-dependent hardness measurements were made upon a (1 11) face of 40 Q cm single crystal germanium using a Leitz Miniload Hardness Tester equipped with a standard microscope hot stage. The apparatus has been previously used for hot hardness measurements by Gerk (1975). This work in fact showed that germanium would be a convenient material to use for the present purposes because of the strong time dependence of its indentation hardness at slightly elevated temperatures.…”