Time-of-flight scattering and recoiling spectrometry. II. The structure of oxygen on the W(211) surface

The technique of time-of-flight scattering and recoiling spectrometry (TOF-SARS) with detection of both neutrals and ions is applied to structural analysis of oxygen adsorbed on a W(211) surface. The site position for oxygen in the high-dose [Θ=1.5 monolayers (ML), saturation coverage] p(1×2) low energy electron diffraction (LEED) pattern is determined; a preliminary study of oxygen in the low-dose (Θ=0.5 ML) p(2×1) LEED pattern is also presented. Both Ar and Ne backscattering (BS) and oxygen recoiling spectra, induced by pulsed 4-keV ${\mathrm{Ar}}^{+}$ and 5-keV ${\mathrm{Ne}}^{+}$ primary-ion beams, are monitored as a function of polar beam incident angle α, surface azimuthal angle δ, scattering angle θ, and recoiling angle φ. Plots of BS (or recoil) intensities in (α,δ) space provide scattering (or recoiling) structural contour maps and three-dimensional scattering (or recoiling) structural plots which are representative of the adsorption sites of oxygen on the W(211) surface; the symmetry of the adsorption sites is determined from these plots.