Structural analysis by reflectance anisotropy spectroscopy: As and Sb on GaAs(110)

We present calculated and measured reflectance anisotropy spectra (RAS) in the energy range from 1 to 6 eV of cleaved GaAs(110) surfaces covered with one monolayer of As and Sb in a (1 x 1) pattern. The spectral range and the accuracy of the data were improved and correlated for the first time with ab initio calculations of RAS spectra for the ECLS (epitaxial continued layer structure) and EOTS (epitaxial on top structure) surface models. The theoretical spectra for the two models completely differ and rule out the EOTS for both adsorbates. For Sb/GaAs(110) this finding agrees with the previous experimental and theoretical results reported on the structure. For As on GaAs(110) the ECLS structure was also suggested, but so far no direct proof for this model has been given. In this paper we show how RAS, thanks to its sensitivity to details of the surface structure and ab initio theoretical description, demonstrates its potential to conclusively determine surface structures.