STRUCTURE OF THE SULFUR-PASSIVATED GAAS(001) SURFACE

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 (1 $($) over bar$$ 11) and (111 ) diffraction planes inclined by 54 degrees to the (001) surface. The sulfur atoms are at the bridge site on the Ga-terminated GaAs(001) sur face, forming bonds with the underlying Ga atoms. The sulfur atomic la yer is approximately 1.1 Angstrom above the underlying Ga atomic layer . The existence of symmetric sulfur-sulfur dimers lining up in the [1 $($) over bar$$ 10] direction is not confirmed for the 2 X I reconstru cted S/GaAs(001) surface.