Atomic-resolution STM of a system with strongly correlated electrons:NiO(001) surface structure and defect sites

Abstract

Elevated-temperature scanning tunneling microscopy has been used to obtain atomic resolution images of (001) surfaces of NiO single crystals. Empty-state images of the (1\ifmmode\times\else\texttimes\fi{}1) surface show the nickel-atom sites and filled-state images show the oxygen ions in agreement with recent theoretical studies of the electronic structure of NiO. Empty-state and filled-state images of point defects and patterning effects observed on the upper terraces of 〈100〉 step edges are explained by directional 2p-3d covalent bonding between the oxygen and nickel sublattices.