Identification of Two-dimensional FeO2 Termination of Bulk Hematite ɑ-Fe2O3(0001) Surface

Iron oxides are among the most abundant compounds on Earth and have been exploited and researched extensively. Knowing the atomic structure of their surfaces is essential for the understanding and control of their catalytic properties, electronic character and spin arrangement. By a combination of atomically resolved microscopy, electron diffraction and surface-sensitive spectroscopies, we examine the oxygen-rich superstructure grown on ɑ-Fe2O3(0001) hematite surface and reveal a continuous two-dimensional layer of iron dioxide, structurally analogous to transition metal dichalcogenides. Using total-energy density functional simulation to optimize an atomic model of the superstructure, we identify it as antiferromagnetic and conductive 1T-FeO2 attached on half-metal terminated bulk. These results open the way to the identification of epitaxial 2D layers on other similar metal-oxide surfaces and to a better understanding of their catalytic activity.