A PHOTOEMISSION AND XAS STUDY OF OXYGEN COADSORBED WITH A (2X2) LAYEROF K ON GRAPHITE

We have studied the coadsorption of oxygen with a (2 x 2) monolayer of K on graphite. At least three different adsorption phases for oxygen have been found. Different spectroscopic techniques have been used in order to identify the different oxygen species adsorbed on the surface . For low oxygen coverage, the molecules dissociate and form a K2O spe cies. At higher oxygen doses, K2O2 and KO2 are present on the surface up to saturation coverage. XAS yields an O-2 bond length of about 1.39 Angstrom for the KO2 in this phase. This species is found to form an ionic complex which is weakly bound to the graphite. (C) 1997 Elsevier Science B.V.