PNNL

Abstract

Quantum antidots (a vacancy cluster) have been proposed to account for the non-linear optical behavior of magnesium oxide (MgO) dispersed with Au nanoclusters [1,2]. In this paper, we provide convincing evidence, based on direct observation using high-angle annular dark-filed imaging in aberration corrected scanning transmission electron microscope, that vacancies in excess of Au atoms are clustering together to form antidots at the immediate neighborhood of the Au clusters, leading to a spatially associated Au nanocluter and antidot. The antidots show a terraced layer structure and are typically facetted along the MgO{100} planes. Furthermore, we also directly observed that Au atom substitutes for Mg atom in the MgO lattice, which is consistently supported by image calculations.