Photon-stimulated desorption and other spectroscopic studies of the interaction of oxygen with a titanium (001) surface

Synchrotron radiation at the Synchrotron Ultraviolet Radiation Facility at the National Bureau of Standards has been employed to study the adsorption of oxygen on a Ti(001) surface using photon-stimulated desorption (PSD), electron-stimulated desorption (ESD), and ultraviolet photoemission spectroscopy (UPS). The dominant ESD and PSD products observed for oxygen exposures greater than one langmuir are ${\mathrm{O}}^{+}$ ions having a most probable kinetic energy of about 3 eV. The photon energy dependence of the PSD ion yield is similar to the major features of the constant final-state secondary-electron yield although there are some differences in detail. This similarity is consistent with the ${\mathrm{O}}^{+}$ desorption being initiated by the production of a Ti $3p$ core hole as suggested by the Knotek-Feibelman Auger decay mechanism. The dependence of the ${\mathrm{O}}^{+}$ ion yield on oxygen exposure and surface temperature is compared with UPS and work-function measurements. These data indicate that surface oxidation occurs at temperatures as low as 90 K and that at least a fraction of the surface oxide is electronically similar to the maximal valency compound Ti${\mathrm{O}}_2$.