Plastic deformation of gallium antimonide single crystals: Yield stresses, activation parameters and dislocation structures

Abstract

Single crystals of undoped GaSb were deformed by compression at low strain rates from 0.48 Tm to 0.3 T _m (where T _m is the melting temperature). The activation enthalpy derived by standard techniques at the yield stress in pre-strained GaSb is about 1.6eV in fair agreement with activation energies for dislocation velocities. The dislocation structures were estimated by transmission electron microscopy. A progressive transition is observed from curved dislocations and edge-type lenticular loops and dipoles at high temperatures and low stresses to predominant long screw dislocations at low temperatures and high stresses. This transition is explained in terms of dislocation-dislocation interactions as against Peierls lattice friction, the onset of thermally activated cross-slip and the large anisotropy of dislocation velocities. Quantitative estimates show that screw dislocations are rate controlling and give the major contribution to the plastic strain at T<620 K, τ_y>10MPa.