INPLANE STRUCTURE OF ARSENIC DEPOSITED ON THE SI(111) SURFACE STUDIED WITH THE GRAZING-ANGLE X-RAY STANDING-WAVE METHOD

The in-plane structure of the Si(111):As - 1 x 1 surface has been studied under ultrahigh vacuum using x-ray standing waves produced by a substrate silicon crystal in the grazing-angle diffraction geometry. The observed As fluorescence profiles are consistent with models indicating a bulklike surface with threefold-coordinated As atoms in the first layer. Evidence indicating that the As atoms occupy these high-symmetry sites with little disorder is obtained from investigation of the dependence of fluorescence profiles on the displacement and order parameters.