Surface Structures Of Mnas Grown On Gaas(111)B Substrates

Atomically flat MnAs epilayers grown on GaAs(111)B substrates by molecular-beam epitaxy present surface structures depending on the sample temperature and on the surface stoichiometry: the known (2x2) reconstruction and two new phases, i.e., a (3x1) reconstruction and a mixed phase of (2x2) and (3x1). By monitoring the reflection high-energy electron-diffraction diagram evolution as a function of the annealing temperature, it was possible to ascribe the (3x1) as being the As richest phase and the (2x2) as the As poorest phase. Two structural models for the observed reconstructions [i.e., (3x1) and (2x2)] are proposed.