Hydrated α-Fe2O3(11¯02) surface structure: Role of surface preparation

The surface structure of α-Fe2O3(11¯02) was studied under two different surface preparation conditions using crystal truncation rod (CTR) diffraction. Wet chemical and mechanical polishing (CMP) at 298 K results in a crystalline surface termination in which the top layer of iron atoms is absent compared to the stoichiometric bulk termination. Annealing in air at 773 K resulted in a transformation of the surface to a structure consistent with hydroxylation of the stoichiometric termination. These results agree with theoretical predictions of Lo et al. [C.S. Lo, K.S. Tanwar, A.M. Chaka, T.P. Trainor, Phys. Rev. B 75 (2007) 075425] and clearly show an ambient pressure surface preparation path leading to a stoichiometric hydroxylated surface, which is apparently a meta-stable configuration at room temperature.