Preparation and characterization of epitaxial iron oxide films

Well-ordered, pure-phase epitaxial films of FeO, Fe3O4, and gamma-Fe2O3 were prepared on MgO(001) by oxygen-plasma-assisted MBE. The stoichiometries of these thin films were controlled by varying the growth rate and oxygen partial pressure. Selective growth of gamma-Fe2O3 and alpha-Fe2O3 was achieved by controlling the growth conditions in conjunction with the choice of appropriate substrates. Growth of the iron oxide epitaxial films on MgO at greater than or equal to 350 degrees C is accompanied by significant Mg outdiffusion. The FeO(001) film surface exhibits a (2 x 2) reconstruction, which is accompanied by a significant amount of Fe3+ in the surface region. Fe3O4(001) has been found to reconstruct to a (root 2 x root 2)R45 degrees structure. gamma-Fe2O3(001) film surface is unreconstructed.