Electron-beam specular reflectivity in high-energy electron diffraction was evaluated quantitatively by measuring the reflected electron-beam current. Using this method, As desorption from a (001) GaAs surface was studied in detail. This desorption process was sensitive to the transition of surface reconstruction and the activation energy for this process changes according to the reconstruction transition. Influence of Surface Reconstruction on the As Desorption Process from a (001) GaAs Surface Evaluated by Improved High-Energy Electron-Reflectivity Measurements. H.Yamaguchi, Y.Horikoshi: Physical Review B, 1991, 44, 5897-900