Knoop hardness anisotropy on {001} faces of germanium and gallium arsenide

Knoop hardness measurements have been carried out as a function of azimuthal angle and temperature (in the range 20°–440°C) on {001} faces of n-type, p-type, and intrinsic Ge and GaAs. The degree of hardness anisotropy shown increases with increasing temperature and for Ge is undetectable below a certain temperature which depends on doping. In GaAs, asymmetry in hardness between [110] and [110] directions was found at high temperatures. A new model of hardness anisotropy has been developed, based on detailed modeling of the plastic zone. This relates the hardness to the degree of workhardening in different regions of the plastic zone. Using this model, detailed explanations are given of the hardness anisotropy behavior and of the plastic recovery around indentations.