The Fe3O4 origin of the Biphase reconstruction on α-Fe2O3(0001)

The so-called Biphase termination on alpha-Fe2O3 has been widely accepted to be a structure with a similar to 40 angstrom unit supercell composed of coexisting islands of Fe1-x and alpha-Fe2O3. Based on thermodynamic arguments and experimental evidence, including transmission electron diffraction, imaging, magnetic and spectroscopic information, it is found that the previously proposed structure model is inaccurate. The actual Biphase structure is instead a layered structure related to the reduction of alpha-Fe2O3 to Fe3O4. A model for the Biphase termination is proposed which does not contain islands of Fe1-xO but instead consists of bulk alpha-Fe2O3 and a Fe3O4-derived overlayer. The proposed model is consistent with all current and previously reported experimental findings. (c) 2009 Elsevier B.V. All rights reserved.