Adsorption Site Distributions on Cu(111), Cu(221), and Cu(643) as Determined by Xe Adsorption

Xe has been used to probe the distributions of adsorption sites across three different Cu single-crystal surfaces: Cu(111), Cu(221), and Cu(643). These expose terrace, step, and kink sites, respectively. The study couples the use of scanning tunneling microscopy (STM), temperature-programmed desorption (TPD), and photo-emission of adsorbed Xe (PAX) to assess their use as methods for determining adsorption site distributions on Cu surfaces. STM shows that the Xe adsorption sites in order of energetic preference are kink, step edge, and terrace, but indicates that the binding energy differences between the three are likely very small. This is borne out by Xe TPD studies that show distinct differences in the desorption kinetics on the three surfaces but unresolvable differences in the desorption temperatures and binding energies at the terrace, step, and kink sites. PAX spectra reveal observable features that can be associated with Xe adsorption at terrace, step, and kink sites. These features can be analyzed semiquantitatively to give insight into the distributions of sites on these surfaces.