History, present status and future of the contribution of high-voltage electron microscopy to the study of radiation damage and defects in solids

The research history of high-voltage electron microscopy is reviewed, placing emphasis on the study of radiation damage and defects in materials. Explanations of twenty-five research subjects are given: state of electrons passing through crystals and displacement damage, replacement sequence collision damage, confirmation of the nature of stacking fault tetrahedra, directional regular arrangement of vacancy clusters, conversion of stacking fault tetrahedra to voids, point defect processes during continued radiation damage, interstitial mobility from interstitial cluster nucleation, vacancy mobility from interstitial cluster growth, detection of vacancies by electron irradiation, electron-radiation-induced diffusion of point defects, space- and time-wise fluctuation of point defect reactions, positional instability of small interstitial clusters and the mode of interstitial motion, directional flow of interstitials along dilatational strain field gradients around a dislocation, measurement of dislocation bias-factors, electron-radiation-induced purification, annealing behavior of radiation-induced point defect clusters and identification of self-diffusion carriers, neutron irradiation of electron-radiation-induced defects and discovery of the cascade-localization-induced bias, electron-radiation-induced crystallization and mechanism of diffusion in amorphous solids, masked irradiation and free migration of point defects, and intermittent electron irradiation and measurement of short relaxation phenomena. The need for a high-voltage electron microscope which can accept radioactive samples, such as those irradiated with neutrons, is emphasized. Proposals are made for future avenues of research using the HVEM. (orig.)