The reduction and oxidation of Fe2O3(0001) surface investigated by scanning tunneling microscopy

► Fe2O3(0001) surface is reduced into Fe3O4(111) by sputtering and vacuum annealing. ► The depth of reduction increases with repeated annealing in vacuum. ► Fe3O4(111) layers are oxidized to a honeycomb superstructure by annealing in O2. ► The oxidation only occurs partially on top with FeO and Fe2O3 domainscoexisting.