Reflectance anisotropy spectroscopy of ordered Sb overlayers on GaAs(110) and InP(110)

Abstract The optical anisotropy of clean GaAs(110) and InP(110) cleaved surfaces, ordered Sb-p(1 × 1)-monolayers, and substrate-induced, ordered Sb multilayers was studied by means of reflectance anisotropy spectroscopy (RAS). The preparation was performed in UHV by deposition of 4–5 ML thick amorphous Sb films onto cleaved substrates and subsequent annealing steps which induce the ordering and, above 600 K, lead to the desorption of the Sb in excess of a single monolayer. In-situ Raman scattering experiments allow us to identify unambiguously the ordered multi- or monolayers by their different vibrational modes after each preparation step. RAS spectra of the clean surfaces show structures at the E 1 , E 1 + Δ 1 and the E 0 ′ , E 2 gaps. The substrate-induced, ordered Sb multilayers exhibit a strong feature at 1.7 eV. The Sb monolayers reveal pronounced anisotropies around 2–2.7 eV, 3.0 and 4.3 eV. By comparison to the results of microscopic tight binding calculations the RAS signals around 2–2.7 eV can be attributed to transitions between mainly surface electronic states, whereas in the E 1 and E 0 ′ , E 2 regions mainly surface perturbed bulk states contribute.