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Abstract

Formation of the epitaxial iron oxide monolayer on the Pt(100)-hex substrate was studied by scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). High resolution STM images reveal a sinusoidal height modulation of the top atomic rows along the [011] direction of the original Pt(100)-hex substrate. This modulation is assigned to the buckling of the top oxygen layer due to the interaction with Pt substrate atoms. Two superstructures described as FeO(111)/Pt(100)-c(2x10) and -(2x9) coincidence structure coexist on the surface. The latter structure results in a much lower Pendry R-factor in dynamical LEED analysis than earlier reported for a c(2x10) structure. Numerous islands, having the same surface structure as the terraces, develop on the dense FeO overlayer. They are assigned to the Pt(100)-(1x1) islands formed during (hex)®(1x1) reconstruction of the Pt substrate underneath the FeO(111) bilayer. The islands are rectangular and elongated in the direction of hex-reconstruction on the original Pt(100). Combined STM and LEED data clearly indicate that anisotropy in the substrate reconstruction leads to anisotropy of the oxide overlayer.