LAUSR

Monochromatic and aberration corrected electron microscope was developed in order to study an electronic structure of various materials, combining with a scanning transmission electron microscope (STEM) and an electron energy-loss spectroscopy (EELS) at atomic scale. [1] This microscope is equipped with a double Wien-filter monochromator, and obtained energy resolutions are selectable from 0.25 eV to 0.02 eV keeping the atom-sized electron probe on the specimen plane by the change of the width of the slit located between two filters. Since this microscope is equipped with the conventional thirdorder aberration corrector, the residual dominant geometric aberration was six-fold astigmatism. On the other hand, the higher-order aberration corrector was developed, which enable us to correct fifth-order geometric aberrations including six-fold astigmatism and to expand a uniform phase area of a Ronchigram in STEM to about 60 mrad in half angle even at lower accelerating voltages. [2-3]