Adsorption and structure dependent desorption of CO on Co(0001)

The adsorption of CO on the Co(0001) surface at room temperature and at 180 K has been studied using work function measurements, X-ray photoelectron s pectroscopy, thermal desorption spectroscopy (TDS) and low energy electron diffraction. At low coverages and at room temperature the standard (root 3 x root 3)R30 degrees-CO structure was observed. By decreasing the temperatu re and increasing the CO exposure, other stable structures were found on th e surface. The (root 7/3 x root 7/3)R10.9 degrees-CO structure was found in a small coverage range around theta = 0.43 ML and the (root 127 x root 12/ 7)R10.9 degrees structure with theta = 0.58 a;at saturation exposures. Each of the structures were attached to a specific desorption regime in the TDS spectrum. The position of the C 1s and O 1s core levels indicate single ad sorption site in the two lower coverage structure and two different adsorpt ion sites for the most dense adsorption layer. (C) 1998 Elsevier Science B. V. All rights reserved.