A TEM in situ investigation of dislocation mobility in the II–VI semiconductor compound ZnS A quantitative study of the cathodoplastic effect

Abstract

The cathodoplastic effect has been studied in ZnS by in situ transmission electron microscopy (TEM) deformation experiments in the temperature (T) range 290–470K and for electron beam intensities (I) varying from 35 to 5600 Am⁻². The dislocation glide governed by the Peierls mechanism is greatly enhanced by increasing I. The velocity per unit length (P) of screw and both types of 60° dislocations varies linearly with I below a critical intensity I _s; then, it tends to saturate. These results are consistent with a radiation-enhanced dislocation glide (REDG) mechanism. Thermal activation energies for dislocation motion are estimated to 1·16 ± 0·10 eV in the absence of electronic excitation and 0·30 ± 0·10 eV under electron irradiation. For I < I _s, screw and both kinds of 60° dislocations (α β), have similar activation energies unlike the other semiconductor compounds. In the frame of the REDG model, the reduction in activation energy is attributed to the energy released upon non-radiative capture of excited carriers at straight dislocation sites.