Factors affecting high resolution fixed-beam transmission electron microscopy.

An experimental and theoretical characterization of a fixed-beam transmission electron microscope with a field emission gun has been made with regard to the factors of electron beam brightness, spatial and temporal coherence of the incident electrons, objective lens current fluctuation, mechanical stability, and specimen contamination. It has been found that mechanical stability and temporal coherence are the primary factors that prevent the contrast transfer function from extending to 2.0 A in our microscope. Different amorphous thin films have also been used in order to compare their suitability for testing the imaging capability of the microscope at atomic resolution.