Coexistence of anion and cation vacancy defects in vacuum-annealed In2O3 thin films

We report on the defect structure and composition of vacuum-annealed In2O3 (VA-In2O3) ferromagnetic thin films. VA-In2O3 is highly (∼7 at.%) oxygen deficient. High-resolution microscopy reveals disordered glassy surface layers and crystalline defect states, O and In vacancies, and In–In clustering, predominantly in the vicinity of the surface. These defects are not observed in as-deposited In2O3 films. These structural defects are important for understanding many of the novel properties found in non-stoichiometric In2O3, including high conductivity and room-temperature ferromagnetism.