A study was made of the change in the GaAs(001) surface reconstruction, due to Si deposition, by using reflection high-energy electron diffraction and scanning tunnelling microscopy. It was found that, with increasing Si deposition below 15% of a monolayer at substrate temperatures above 600C, new reconstructions formed that were not observed on the initial surface. The initial surface, prepared by molecular-beam epitaxy, was the (2 x 4) As-stabilized reconstruction. Scanning tunnelling microscopy reveals straight missing dimer rows with two As dimers per unit cell. With an increasing amount of Si deposited on this surface, the reconstruction showed an increasing disorder due to kinks that develop in the missing dimer rows. The Si deposition led to an overall decrease of the As coverage. After a Si deposition of 5% of a ML a new Ga stable (3 x 2) reconstruction starts to develop. With further increasing the Si concentration or the substrate temperature at this Si level, the surface continues to get more Ga stable transforming via a (5 x 2) to a (4 x 2) reconstruction. Reconstruction of the GaAs(001) Surface Induced by Submonolayer Si Deposition. M.Wassermeier, J.Behrend, L.Däweritz, K.Ploog: Physical Review B, 1995, 52, R2269-72