Quantitative determination of the adsorption site of the OH radicals in the H2O/Si(100) system

Abstract

Using scanned-energy mode photoelectron diffraction from the O 1s level, the local structure around the adsorbed OH species resulting from the interaction of H2O with a Si(100)(2 ? 1) has been determined, by a combination of direct data inversion using a "projection" method and multiple-scattering simulations. The O atom is bonded to a surface Si atom with a Si-O bond length of 1.67?0.03 ?, the Si-O bond being tilted away from the surface normal by 19?4?. This bonding Si atom is at one end of a surface dimer, which lies parallel to the surface to within ?9?, but there appears to be a lateral offset of the dimer along the dimer direction away from the fully symmetric position by approximately 0.3 ?, possibly reflecting a residual asymmetry associated with the adsorbate bonding. The main structural parameters are in excellent agreement with the results of a previously published density-functional theory slab calculation.