Reduction of an α-Fe2O3(0001) Film Using Atomic Hydrogen

The α-Fe2O3(0001)-biphase surface consists of an ordered arrangement of FeO(111) and α-Fe2O3(0001) surface domains on a Fe2O3 bulk [N.G. Condon et al., Phys. Rev. Lett. 75, 1961, 1995]. The interaction of atomic hydrogen Hat with this surface has been investigated at room temperature (RT, 300 K) by means of low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS) and thermal desorption mass spectroscopy (TDS). The surface is easily hydroxylated by Hat. Upon heating, the OH groups react to produce hydrogen and water, the latter of which results in the partial reduction of the surface. In a parallel but slower process, bulk reduction proceeds already during exposure at RT. First, Fe3O4(111) domains, embedded in the α-Fe2O3(0001) matrix are formed. Finally, the film is completely reduced to Fe3O4. Further reduction towards FeO or metallic Fe appears kinetically hindered and is not observed under the low exposures used in our experiments