Direct Observation of Crystal Imperfections in KCl Single Crystal by Electron Microscope

Abstract

The processes of change of a thin KCl single crystal due to electron irradiation were observed by means of an electron microscope and electron diffraction. It was found that under weak electron irradiation loop structures first appeared and then disappeared showing a lot of small bright specks over the whole crystal. In this stage, each diffraction spot had streaks in 〈100〉 directions. Under intense electron irradiation bright squares appeared initially without the appearance of loop structures. In this stage, the diffraction pattern was a perfect net‐like pattern. It was found that by using the replica technique, loop structures and large squares appeared in the crystal, and also that by using the dark‐field image method the contrast of loop structures and bright squares was due to Bragg reflection, which had resulted from the formation of voids and cubic cavities in the crystal, respectively. From the experimental results, the mechanism of coagulation of vacancies in KCl crystal with electron irradiation is discussed.