Quantitative approach to molecular resolution electron microscopy

Abstract

MANY attempts have been made to resolve individual atoms as ions, in molecules; and in crystals using conventional and scanning transmission electron microscopy^1–5. The results have been presented in the form of photographs for essentially qualitative assessment. In order to put the technique on a quantitative basis, we have analysed images of isolated molecules on thin supporting films using a digitising microdensitometer. We report here the results for a particular test molecule with a readily identified structure containing one heavy atom (Z = 80) for reference and two medium ones (Z = 35) for determining the reliability threshold. As yet, images of lighter atoms (Z = 16) have been obtained only after extensive processing⁴, which impedes quantitative assessment.