Surface electron motion near monatomic steps: Two-photon photoemission studies on stepped Cu(111)

The electronic structure of three surface or near-surface states on stepped Cu(775) has been investigated using angle-resolved, resonant, two-photon photoemission. Since the electron wave function in each of these electronic states has a different average distance from the crystal plane, the measurement allowed the step potential at each distance to be sampled. The energy dispersion of the $n=1\mathrm{}$ image-potential state was found to be oriented by the (111) terrace and the $n=2\mathrm{}$ state was oriented by the (775) surface plane. The band structure of the embedded $\mathrm{sp}$-like surface state $\mathrm{}(n=0\mathrm{})\mathrm{}$ was determined by the projection of the bulk band gap onto Cu(775).