Reconstructed surfaces on Sb/GaAs(001) were investigated in situ by reflection high-energy electron diffraction and core-level photoelectron spectroscopy by heating a sample prepared by depositing Sb on an As-terminated GaAs(001) surface at room temperature. Before Sb desorption, the halo reflection high-energy electron diffraction pattern changes into 1 x 4, 1 x 3 and 2 x 4 patterns from room temperature to 560C, which was in contrast to Sb/GaAs(110) that showed only a 1 x 1 pattern. It was found that the GaAs surface with a 2 x 4 pattern was terminated by a monolayer of Sb, and that these superstructure changes were caused by As atom desorption followed by Sb atom substitution. Sb-Induced Surface Reconstruction on GaAs(001). F.Maeda, Y.Watanabe, M.Oshima: Physical Review B, 1993, 48, 14733-6