Phase retrieval through focus variation for ultra-resolution in field-emission transmission electron microscopy

Abstract

The use of a coherent field-emission electron source in transmission electron microscopy is combined with phase retrieval by digital processing of a focal image series. For the first time, a dramatic improvement of the high-resolution performance of the electron microscope beyond the usual "point-to-point" resolution has been realized: Experiments on a 200-kV microscope with a point resolution of 0.24 nm reveal reconstructed information down to 0.14 nm. Examples are shown in the field of high-Tc superconductors and ferroelectric oxides. The oxygen sublattice in these structures is revealed.

Wave-front phase retrieval in transmission electron microscopy via ptychography

“…There are several methods for retrieving phase using such data. [5][6][7][8] However, because the wave intensity relies on local interference between wavelets in the Fresnel propagation integral, then-such as the bright-field image-it is also poor at measuring quantitative large-scale phase distributions across a wide field of view. To date, the only method for capturing large phase changes which also have large-scale features over a significant field of view ͑ ϳ1 m͒ is off-axis electron holography.…”

HREM on Tc=14.5 K superconducting ThPd2B2−xC

“…The technique of through-focus image reconstruction uses the information of a series of high-resolution electron microscope images taken at different defocus values with well defined defocus increments. Using algorithms developed by Van Dyck [ 10 ] and Coene [ 11 ] all useful information can be extracted from these images into one image in which the distortion introduced by the electron microscope is restored.…”

“…Through-focus image reconstruction [ 10,11 ] was applied to obtain more detailed information on the structure ofThPd2B2_ ~C. This technique is also called through-focus electron holography [10,11 ].…”

“…This technique is also called through-focus electron holography [10,11 ]. The through-focus high-resolution images and the electron-diffraction patterns were recorded using a Tietz software package and a 1024 × 1024 pixel Photometrix CCD camera having a dynamic range of 12 bits.…”

“…Cava et al [ 11 ] have reported superconductivity at 16.6 K for the compound LuNi2BEC. LUNiEBEC has a fairly simple structure, which is based on the stacking of LuC layers with NiEB 2 blocks [2,3] e.g.…”