Structure determination for saturated (1×1) oxygen on W(110) from full solid angle photoelectron diffraction with chemical-state resolution

Abstract

The local atomic geometry of oxygen adsorbed in a stable one monolayer (1×1) structure on W(110) has been determined for the first time from full solid angle site-resolved photoelectron diffraction (PD). This structure also exhibits an additional (1×12) periodicity, but PD allows determination of the local structure within this periodicity. The data were obtained with a new beamline and experimental system at the Advanced Light Source. W 4f7/2 spectra excited at kinetic energies of approximately 140eV were resolved into bulk and ‘oxide’ components, with the latter corresponding to the first layer of tungsten atoms bound directly to three oxygen atoms each. Analyzing these data with multiple scattering theory and R-factor analysis shows that the oxygen atoms sit in pseudo-threefold hollow sites at a vertical distance of 0.91±0.05Å above the first tungsten layer, and with a lateral position shifted by 0.1Å along [11̄0] or [1̄10] directions and away from that yielding three equal bond distances. Future applications of this method to systems with large unit cells which make beam-in/beam-out diffraction analyses difficult and/or with a lack of long range order are thus suggested.