Self-organized chromium oxide monolayers on Fe(001)

The oxygen-saturated Fe(001)-p(1 × 1)O surface has been used as a template to stabilize two-dimensional Cr oxides on Fe(001). Cr deposition at 400o C leads to two different well-ordered phases, depending on the amount of Cr deposited. In the submonolayer regime a novel c(4 × 2) overlayer self-assembles on the Fe(001)-p(1 × 1)O surface, saturating for a coverage of about 0.75 monolayers. This phase becomes unstable for higher coverages, when a (sqrt5 × sqrt5)R27o superstructure emerges. The structural and electronic details of the two one-layer-thick oxides are studied by combining high-resolution scanning tunneling microscopy, low-energy electron diffraction, Auger electron spectroscopy, and density functional theory.