The adsorption position of sulfur atoms in the sulfur-passivated GaAs(001) surface is investigated by soft-x-ray standing-wave triangulation using two types of noncentrosymmetric (11¯1) and (111) diffraction planes inclined by 54° to the (001) surface. The sulfur atoms are at the bridge site on the Ga-terminated GaAs(001) surface, forming bonds with the underlying Ga atoms. The sulfur atomic layer is approximately 1.1 Å above the underlying Ga atomic layer. The existence of symmetric sulfur-sulfur dimers lining up in the [11¯0] direction is not confirmed for the 2×1 reconstructed S/GaAs(001) surface.

• Received 28 March 1994

DOI:https://doi.org/10.1103/PhysRevB.50.4905