Effect of the Substrate on Image Contrast in High Resolution

A high resolution electron microscope intended for the study of thin biological molecules is currently under development at Cornell University. Previously reported computer calculations of the molecular images to be expected from this instrument indicate that considerable atomic structural detail would be visible in the image, specifically that atoms having Z≥6 would exhibit sufficient phase contrast to be observed and interatomic spacings ≳2Åwould be resolved. These earlier calculations did not consider the effect on the image of the substrate supporting the specimen. Results of a theoretical investigation of the substrate and computer calculations are presented here.