Discrimination of individual atoms in the molecular images of chlorinated copper phthalocyanine

Abstract

For the establishment of solid approaches to the target of discriminating individual atoms in molecular images, it still seems to be necessary to deal with radiation resistant compounds with known structures. The use of thin specimen crystals renders several advantages, as they keep molecules in suitable orientations with tolerably small atomic displacements due to the thermal vibration. Rows of stacked molecules increase the contrast in the projected images, although the thickness must be such that the specimen can be regarded as a thin phase object. Two dimensional periodicity of projected images facilitates the spacial averaging which increases the s/n ratio as predicted by Kuo and Glaeser, reducing the exposure time and consequently the radiation damage. In order to realize the atomic resolution, the improvement in the instrumental characteristics is indispensable as well. The 500kV electron microscope constructed by Kobayashi et al. has the capability of achieving the ultimate resolution of 1.5A, and played the principal role in the present attempt to reach the atomic resolution.