Interpretation of Oxygen 1s X-ray Photoelectron Spectroscopy of ZnO X-ray photoelectron spectroscopy (XPS) is widely used to determine the chemical and electronic states of atoms within a material. However, it is often complex to interpret the O 1s region in metal oxides, where an ∼531 eV binding energy feature appears between lattice oxygen (∼530 eV) and oxygen-containing surface species (∼532 eV). This feature has been vaguely ascribed to oxygen vacancies or oxygen deficient regions for many ...