New Trend of Atom Resolution Electron Microscopy—Direct observations of atoms, vacancies and impurity atoms in crystal and on-line image analysis

Recent development of atom resolution electron microscopy are described. First, the nature of electron diffraction patterns and electron microscope images appearing at the back focal plane and image plane of objective lens, respectively, is discussed. The method to eliminate the shifting of atom images due to crystal thickness and lens aberration, and the effect of beam divergence and chromatic aberration on the image contrast are discussed. Atomic structures of stacking faults and twins are observed, and migrations of atoms accompanying their movements and interactions are also recorded. Images of vacancies, impurity atoms and stacking faut tetrahedra in atomic scale are also observed, which are confirmed by comparison with the calculated contrasts. Atoms on the surface of gold (111) surface are observed. Construction of the on-line image analysis system, and applications of circular window and Hamming window to elimination of artefact streaks appearing at diffraction spots formed by the Fourier transform are shown.