GREATLY DEFOCUSED, POINT-PROJECTION, OFF-AXIS ELECTRON HOLOGRAPHY

A practical and wave-optical description is given for two modes of gre atly defocused point-projection electron holography that have been imp lemented in a scanning transmission electron microscope. A comparison is made between these electron holographic modes and those conventiona lly employed in TEM. The resolution, field-of-view, and phase sensitiv ity is discussed in general, and for our particular implementation. A method for correcting defocus aberrations in holographic images is sho wn. Phase contrast arising from electromagnetic fields is described. Q uantitative examples are given for the determination of the mean inner potential, thickness integrated magnetization in magnetic thin films and domain structure in magnetic superlattices.