Rotation between micrographs from the scanning electron microscope and electron channelling patterns

Abstract

When a large single crystal is examined in the scanning electron microscope, micrograph and electron channelling pattern (ECP) may be obtained simultaneously. When obtaining the selected area ECP of a small crystal, a separate micrograph must be taken. Relating the ECP to the micrograph in either case, the crystallographic direction of the centre of the micrograph is correctly indicated by the pole direction of the centre of the ECP. But the directions of planes with normals orthogonal to the optic axis may not be correctly indicated, errors of up to 30 degrees having been measured. The error may occur in any scanning electron microscope with a double-deflection scan system, whether above or below the final lens, and is due to a relative rotation of the planes of the upper and lower scan deflections. The error can be eliminated by using a single scan deflection, as in the deflection-focusing method of obtaining selected-area ECPs.