Water adsorption on Cu(100): The effect of defects

The effect of defect sites on the adsorption of water on a Cu(100) surface has been studied using temperature programmed desorption (TPD), temperature programmed work function change measurements (TPΔφ) and high resolution electron energy loss spectroscopy (HREELS). The TPD and TPΔφ experiments show that only one desorption state at 162 K is observed from the well-ordered Cu(100) surface. Following Ar+ sputtering, however, a second desorption state is present at 177 K and is attributed to the desorption of water molecules from defect sites. The nature of the adsorption at these sites was investigated using HREELS. The HREELS spectra indicate that adsorption on the defected Cu(100) surface proceeds via the formation of clusters of water molecules and rules out the formation of monomers. The observation that the high temperature TPD peak can be isolated on the highly defected surface indicates that the entire cluster is stabilized by the defects. A comparison with other defected and defect free copper surfaces reveals a consistent picture for water-copper bonding.