Structure of (√3×√3)R30° Ag on Si(111)

The structure of ({}3×{}{}3)R30^∘{} Ag on Si(111) has been studied by polar and azimuthal x-ray photoelectron diffraction. We conclude from this data that the Ag cannot be more than 0.5 A{} below the surface, and furthermore from an R-factor analysis of the azimuthal results that the structure consists of two closely related types of Ag honeycomb domains that grow on the second Si layer, with the top Si layer missing.