The Fe 3 O 4 origin of the ‘ ‘ Biphase ” reconstruction on a - Fe 2 O 3 ( 0 0 0 1 )

0039-6028/$ see front matter 2009 Elsevier B.V. A doi:10.1016/j.susc.2009.06.006 * Corresponding author. Address: Department of neering, Northwestern University, 2220 N Campus Dr E-mail address: [email protected] (L.D. M The so-called Biphase termination on a-Fe2O3 has been widely accepted to be a structure with a 40 Å unit supercell composed of coexisting islands of Fe1 xO and a-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 a-Fe2O3 to Fe3O4. A model for the Biphase termination is proposed which does not contain islands of Fe1 xO but instead consists of bulk a-Fe2O3 and a Fe3O4-derived overlayer. The proposed model is consistent with all current and previously reported experimental findings. 2009 Elsevier B.V. All rights reserved.