Transmission Electron Microscopy of Sodium Chloride Films Prepared by Electron Beam Flashing Thinning Technique

Abstract

A new method of electron beam flashing for preparing thin single crystal films of non-conducting substances has been developed. With use of the method, mechanically introduced and grown-in dislocations and precipitates in NaCl containing 0.00 to 2.3 mole % of CaCl₂ are observed by transmission electron microscopy. The Burgers vectors of dislocations are determined by observing their contrast change which occurs when the crystal is set for different Bragg reflections. Characteristic climb of them into helical form due to electron irradiation is observed. The rate of climb expressed by the number of vacancy pairs causing climb per incident electron of 100–150 keV is found to be of the order of 10⁻⁵ in the films of NaCl containing 0.1 mole % of CaCl₂ about 5000Å in thickness. Observations on incipient and final precipitates in NaCl containing more than 0.3 mole % of CaCl₂ are compared with the results of previous X-ray studies.