ABERRATION CORRECTION USING OFF-AXIS HOLOGRAPHY .2. BEYOND THE SCHERZER LIMIT

In order to perform aberration correction, we have to estimate the abe rration working on each hologram. We apply the procedure to estimate t he working aberration [see Part I of this series: K. Ishizuka, T. Tanj i, A. Tonomura, T. Ohno and Y. Murayama, Ultramicroscopy 54 (1994) 361 ] to holograms taken of thin crystals of tungsten niobium oxide (W8Nb1 8O69). The reconstructed images have been obtained by successfully cor recting the aberration up to 5.0 nm(-1). Thus, the procedure can be ap plied to a specimen commonly used for high-resolution electron microsc opy, nm even when a simple phase object approximation breaks down. Sin ce the Scherzer limit of the microscope used in this experiment is 3.9 nm(-1), we have for the first time corrected the aberration of struct ure images significantly beyond the Scherzer limit using the holograph y technique.