Determination of Image Aberrations in High-resolution Electron Microscopy using Diffractogram and Cross-correlation Methods

Abstract

Determination of image aberrations in high-resolution electron microscopy using diffractogram and cross-correlation methods. Methods are discussed to determine the aberration constants of image aberrations in HREM to a high accuracy, as required to obtain ultrahigh resolution. Two methods, designated as diffractogram-tableau (DT) and beam-tilt/cross-correlation BTXC, respectively, are analysed. Both methods utilize sets of images, taken with the beam tilted by several milliradians in different azimuthal directions. Experiments on a CM 200 FEG microscope, using a slow-scan CCD camera and external TEM control, show that both approaches are feasible. In order to correct all relevant aberrations, some additional correction facilities should be provided by the TEM manufacturers.