Mechanisms of dislocation motion and multiplication in ionic and semiconductor crystals

Abstract

The effect of successively applied compressive and tensile stresses τ (τ≈0.17τp to 95τp, where τp is the resolved yield stress) and different stress rates τ≈10-4 to 108 MPa s-1) was investigated in nominally pure NaCl, GaAs, InSb and Si crystals in the temperature range T≈(2.5× 10-3Tm to 0.73 Tm (where Tm is the melting point). Damped motion of dislocations under periodic stresses was observed. This was most clearly manifested for distinct cross-slip dislocations (screws and especially screws with β-type leading partials). The same linear relationship between the minimal stresses required to start dislocation motion, multiplication and macroscopic yielding was found in different materials and under various conditions. This proves that the main mechanisms of dislocation motion, drag, multiplication and work-hardening are the same for different crystal classes. The local stresses near the matrix defects cause dislocations to double cross slip and climb. The dislocation drag and crystal hardening are mainly concerned with conservative and non-conservative motion of atomic-scale jogs and kinks on the dislocations, the Orowan bowing of the dislocations between the obstacles. The new estimates of the lattice friction confirm the previous extremely low estimates of the Peierls–Nabarro lattice friction of τp ≤ 10-8μ–10-5μ (where μ is the shear modulus) and the universality of the above model for the main classes of solids.