EVALUATION OF A SPHERICAL-ABERRATION CONSTANT OF THE OBJECTIVE LENS OF HVEM AT TOHOKU-UNIVERSITY

A spherical aberration constant of the objective lens of a high-voltag e electron microscope at Tohoku University (JEM-ARM1250) was evaluated by processing high-resolution electron microscope (HREM) images of an amorphous Ge thin film. The processing was carried out through a comp uter network system coupled with a highly efficient film scanner. From the intensity profiles of digital diffractograms of two HREM images, the spherical aberration constant of the objective lens (C-s) is estim ated to be C-s = 1.74 +/- 0.10 mm and their defocus values are estimat ed to be about + 77 nm and + 118 nm, respectively.