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 a berrations 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 analyzed. Both me thods utilize sets of images, taken with the beam tilted by several mi lliradians 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 relev ant aberrations, some additional correction facilities should be provi ded by the TEM manufacturers.