Surface reconstructions of epitaxial MnAs films grown on GaAs(111)B

This study makes reference to the surface structure of MnAs(0001) epilayers grown by molecular beam epitaxy through a multitechnical method that combines scanning tunneling microscopy (STM), x-ray photoelectron spectroscopy (XPS), grazing incidence x-ray diffraction (GIXD), and ab initio calculations. Two surface reconstructions were studied, i.e., the (2×2) and the (3×1). Photoemission measurements provided quantitative information about (i) the surface coverage of both surfaces and (ii) the atomic environment of surface atoms. An atomic structural model has been proposed for the observed reconstructions. On the basis of STM observations and ab initio calculations the (2×2) phase is constituted by As trimers adsorbed on an underlying Mn layer of bulk MnAs, while x-ray diffraction analysis, coupled with STM, showed that the (3×1) reconstructed surface is constituted of long and narrow As chains aligned with the 110 GaAs substrate equivalent directions.