WATER-ADSORPTION ON CU(100) - THE EFFECT OF DEFECTS

The effect of defect sites on the adsorption of water on a Cu(100) sur face has been studied using temperature programmed desorption (TPD), t emperature programmed work function change measurements (TPDELTAphi) a nd high resolution electron energy loss spectroscopy (HREELS). The TPD and TPDELTAphi experiments show that only one desorption state at 162 K is observed from the well-ordered Cu(100) surface. Following Ar+ sp uttering, however, a second desorption state is present at 177 K and i s attributed to the desorption of water molecules from defect sites. T he nature of the adsorption at these sites was investigated using HREE LS. The HREELS spectra indicate that adsorption on the defected Cu(100 ) surface proceeds via the formation of clusters of water molecules an d rules out the formation of monomers. The observation that the high t emperature TPD peak can be isolated on the highly defected surface ind icates that the entire cluster is stabilized by the defects. A compari son with other defected and defect free copper surfaces reveals a cons istent picture for water-copper bonding.