Formation and Structural Evolution of Magnesium Oxide Clusters under Electron Irradiation

Magnesium oxide (MgO) clusters were formed by fracture of protrusions at the edges of MgO films under electron irradiation. The fracture was caused by pressing with gold clusters along the incident electron beam direction. The formation and subsequent surface structural evolution of the MgO clusters were observed by dynamic high-resolution transmission electron microscopy. The surface atoms on steps or edges preferentially desorbed, and chair-shaped and rectangular prism clusters appeared. An NaCl structure was stable until the cluster size was reduced to 1 nm.