Approaching atomic-resolution electron microscopy

Abstract

The Cambridge University 600 kV high-resolution electron microscope, supported by local facilities for image simulation and processing, has been successfully used to characterise the microstructure of a wide range of materials at resolutions on, or approaching, the atomic scale. After short descriptions of the microscope and computer facilities, attention is first directed towards the problems of imaging artefacts and beam misalignment. The usefulness of Weak-Phase-Object images for preliminary assessments of image detail, such as dumbbells and possible oxygen atom resolution, is stressed. It is shown that the well-known imaging artefact, namely dumbbells, is an interference phenomenon which can be generated even when the crystal being imaged does not have the classic “atom-pair” projected structure. Methods for assessing resolving power and the validity of information beyond the resolution limit are considered. Particular applications to the study of surface rearrangements, nonstoichiometric rutile and defect annealing in cadmium telluride are briefly described.