Selected-Zone Dark-Field Electron Microscopy

Abstract

Selection of image‐forming electrons that have passed through a small annular zone of the objective lens drastically reduces the resolution‐limiting influence of chromatic aberration. Special objective‐lens aperture diaphragms are needed for this new method of obtaining high‐quality images. The manufacture of the diaphragms is described. High‐resolution and high‐contrast images of crystallographic specimens in the light of selected Bragg‐diffracted beams without preference to azimuthal orientations were obtained. In particular, {111}‐lattice planes of gold were observed as well as interference fringes (``pseudo'' lattice images) between two nonsymmetrical Au {111} diffracted beams, displaying spacings and azimuthal directions characteristic of regular {200}‐ and {220}‐lattice fringes, although the {200} and {220} diffracted beams were omitted by the specific annular aperture used. Such ``pseudo'' lattice images allow deposit orientation determinations in the same way as ``ordinary'' lattice images.