Atomic-scale surface morphology of epitaxial ferromagnetic MnAs thin films grown on vicinal GaAs(111)B substrates

Abstract

We have investigated the atomic-scale surface morphology and magnetic anisotropy of ferromagnetic MnAs films grown by molecular beam epitaxy on vicinal GaAs(111)B substrates misoriented 2° toward the [1̄1̄2] direction. The MnAs films were grown in a step-flow-like manner and atomically flat terraces appeared on the surface in the temperature range between 220 and 300 °C. The terrace width was elongated dramatically in comparison with the original terrace width on the GaAs buffer layer, which resulted from the macrostep formation induced by the step-bunching phenomenon during the growth of MnAs. The terrace width and the macrostep height were 70 and 2 nm, respectively, for the MnAs film grown at 250 °C and both values increased with increasing the growth temperature. The MnAs films grown on the vicinal surface were found to exhibit in-plane uniaxial magnetic anisotropy induced by the macrosteps, which was not observed in the MnAs films grown on the exact GaAs(111)B surface.