Electron Holography by Field Emission Electron Microscope

Abstract

A 100 kV field emission electron microscope has been developed which has lattice resolution of 0.62 Å. Electron holography was put to practical use utilizing the high coherence of this electron beam. The coherence of the electron beam was demonstrated by photographing 3, 000 bi-prism interference fringes, which is an order of magnitude greater than the number obtained previously. Spherical aberration of the electron lens, which has been the main obstacle to improving the performance of electron microscopes, was compensated for in the optical reconstruction stage of holography. Furthermore, an interference microscope was realized by means of holography. The electron microscopic image of an object contains information on object thickness in the phase of the electron beam which is not expressed in usual electron microscopic images photographed on film. Using the interference electron microscopy, the thickness distribution of fine polyhedron particles could be derived and their three-dimensional shapes determined.