Observation of lateral superlattice effects on stepped Cu(001)

Lateral superlattice effects are observed for image-state electrons on a stepped Cu(001) surface via angle-resolved two-photon photoemission. Adsorption of Na atoms (∼0.01 ML) on the stepped surface enhances the step regularity, yielding clear zone folding with a reduced Brillouin zone given by the reciprocal step lattice. © 1996 The American Physical Society.