The enhancement of electron microscope resolution by use of atomic focusers

It is confirmed by computer simulation that, when an electron beam of energy 100–400 keV passes through a single heavy atom, or a row of atoms parallel to the beam (an “atomic focuser”), a very fine beam of diameter less than 0.05 nm, is formed in the region within 1 or 2 nm of the atomic focuser. This very fine beam may be used in scanning transmission electron microscopy (STEM) or in conventional transmission electron microscopy (TEM) to give image resolutions of the order of 0.05 nm if the specimen is held within 1 or 2 nm of the atomic focuser and translated with respect to it by means of, for example, a piezoelectric manipulator system such as that used for atomic probe microscopies. If a thin crystal is made to act as a multiple atomic focuser and the specimen is placed at a Fourier image distance from the crystal, the relative translations of the specimen and the atomic focuser may be more simply achieved by varying the angle of incidence for TEM or the angle of detection for STEM. The achievement of the enhanced resolution with several schemes involving relatively minor modifications of existing TEM or STEM instruments appears to be feasible.