High resolution phase contrast electron microscopy:imaging of single atoms and “amorphous state”

Abstract

Using very thin films of graphite crystals as support films, we demonstrated some bright-field CTEM images of single tungsten atoms and surface structures of the graphite films. Theoretical calculation on these objects using phase object approximation supported the validity of our interpretation of the images.We made a further investigation on the similar phase objects by utilizing a JEOL-UHP objective pole-piece (Cs= 0.7mm) installed in a JEM-100B microscope. This lens gives an “interpretable resolution”,, of 2.6Å. Practically, however, the attainable resolution is restricted by chromatic aberration and illumination angle, barring operational faults. These parameters modify the ideal image transfer functions in the higher frequency region and thus become important for discussing the high resolution details. The resolution measured for the new lens from the optical diffractograms was around 3.2Å, which is slightly better than the value 3.8Å for our old lens (BLG-pole-piece, Cs= 2.0mm).