Substrate disruption and surface segregation for Fe/InAs(0 0 1)

The epitaxial growth of ultrathin Fe films on InAs(0 0 1)-(2×4) and -(4×2) surfaces at room temperature is studied using reflection high-energy electron diffraction as well as ultraviolet and X-ray photoelectron spectroscopy. The InAs(0 0 1)-(2×4) and -(4×2) surfaces are obtained either by ion bombardment and annealing or by molecular beam epitaxy. For the different surfaces a detailed analysis of the In 4d core-level line shape leads to the same conclusion. The deposition of Fe onto InAs(0 0 1) induces a substrate disruption and a surface segregation: in a first step In atoms are released in the metallic overlayer and with increasing the Fe coverage these In atoms continue to segregate at the surface. At the same time, some In atoms are trapped in the Fe overlayer. A small amount of As surface segregation is also observed. Finally, the position of the Fermi level (independent of the surface reconstruction and the preparation method) at the Fe/InAs(0 0 1) interfaces is found ∼0.2 eV above the conduction band minimum.