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 ato ms parallel to the beam (an ''atomic focuser''), a very fine beam of d iameter 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 trans mission electron microscopy (STEM) or in conventional transmission ele ctron 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 piezoelectri c 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 r elative translations of the specimen and the atomic focuser may be mor e simply achieved by varying the angle of incidence for TEM or the ang le of detection for STEM. The achievement of the enhanced resolution w ith several schemes involving relatively minor modifications of existi ng TEM or STEM instruments appears to be feasible.