Experimental Studies on Electronic Trapping Processes Associated with Dislocation Lines in Alkali Halide Crystals

Abstract

The trapping of conduction electrons by dislocation lines in alkali halide crystals was investigated by measuring the temperature dependence of photoconductances of deformed and undeformed crystals. Furthermore, the effect was verified by observing the thermally stimulated currents. In both cases, measurements of electric currents were carried out under application of ac in order to avoid undesirable effects due to space charge formation. Special care was exerted to obtain crystals having a high degree of purity. From the first mentioned experiment, the effective width of dislocation lines for electron trapping was estimated to be 9.3×10⁻⁸ cm, by using dislocation densities determined from nuclear magnetic resonance studies. The thermal depth of dislocation lines was estimated to be 0.21 ev for KBr and 0.24 ev for KCl crystals. A current glow peak, which presumable may correspond to trapping by jogs, was also measured. The thermal depth of jogs may be roughly estimated to be 0.48 ev.