Interaction of oxygen with Pt(210): formation of new oxygen states at higher exposures

The interaction of oxygen with Pt(210) was investigated by means of thermal desorption spectroscopy (TDS) and work function Delta Phi measurements. Tw o TD states reflecting chemisorbed O atoms appear after moderate O-2, expos ures at 413 K. Higher oxygen exposures (3 x 10(1) and 3 x 10(6) L) produce two additional TD states on the low-temperature tail of the TD peaks of che misorbed O; these additional states cannot be saturated, their filling is t hermally activated. Absolute coverages and sticking coefficients (s(0)= 0.4 ) are evaluated from the TD spectra. The low-exposure oxygen states cause a n increase in work function of Pt(210), whereas high-exposure states cause a decrease of the work function. The nature of the oxygen states is discuss ed and the existence of the high-exposure states is tentatively attributed to subsurface oxygen. (C) 2000 Elsevier Science B.V. All rights reserved.