Quantitative Z-contrast imaging in the scanning transmission electron microscope with size-selected clusters

Abstract

This paper describes a new approach of quantification of annular-dark-field or $Z$-contrast image intensity as a function of inner acceptance angle of the detector in a scanning transmission electron microscope. By using size-selected nanoclusters of Pd ($Z$ = 46) and Au ($Z$ = 79), it is shown experimentally that the exponent in the power law $I$ $\ensuremath{\sim}$ ${Z}^{\ensuremath{\alpha}}$ varies strongly between 1.2 and 1.8 as the collection angle changes from 14 to 103 mrad. The result is discussed in line with existing theoretical models. Factors, such as cluster size, structure, and orientation as well as the detector geometry, are also discussed for potential use of the work.