Direct Observation of Crystal Imperfections Introduced by Weak Electron Irradiation in Water-Etched KCl Single Crystal

抄録

The changes in a water-etched KCl single crystals due to weak electron irradiation were observed by means of an electron microscope and by electron diffraction. It was found that in a crystal, the thickness of which became large with the distance from the edge, dislocation loops appeared and their development as observable. When the change of the thickness of the crystal is pronounced, it was easy to find large dislocation loops in the thin part close to the edge of the crystal. In the case in which the size of a dislocation loop is less than 0.5 μ in diameter, one dislocation loop changed abruptly into one void with weak electron irradiation. However, a larger dislocation loop changed into one void and several small dislocation loops. Interactions between two crystal imperfections were also observed in this experiment. From the experimental results, the mechanism of coagulation or dispersion of vacancies in water-etched KCl crystals under weak electron irradiation is discussed.