Reconstruction of the exit surface wave function from experimental HRTEM micrographs

Abstract

A new approach to a theoretical and experimental concept for correction of aberrations, described by the contrast transfer function (CTF) in experimental high resolution transmission electron microscopy (HRTEM), is discussed. Experimentally, the method is characterized by a sidewards shift of the objective aperture in the diffraction plane, so that only the zero beam and one sideband of the diffracted beams are transmitted. As was shown by several authors [W. Hoppe, Z. Naturforsch. 26a (1971) 1155; K.-J. Hanszen and B. Morgenstern, Z. Angew. Phys. 19 (1965) 215; F. Thon, in: Electron Microscopy in Material Science, Ed. U. Valdrè (Academic Press, New York, 1971)], the loss of information due to the zeros of the CTF may thus be avoided. Furthermore, the phase shifts of the diffracted beams resulting from defocus and spherical aberration and the corresponding lateral shifts of the lattice fringes can be calculated and inverted. This leads to a straightforward calculation of the aberration-free complex exit surface wave function or an ideal image, with resolution close to the information limit, out of one or two experimental micrographs.