Thermal behavior of the roughened Cu(110) surface

The roughened Cu(110) surface was prepared by annealing the clean surface at various temperatures ranging from 700 to ∼1000 K. A significant drop in intensity of reflection anisotropy spectroscopy (RAS) peak at 2.1 eV photon energy as a function of increasing sample temperature was found for annealing above the roughening transition at 900 K. The observed change of 2.1 eV peak in RAS spectra is because of the surface state Fermi level shift due to temperature change. The RAS result is in good agreement with an unoccupied surface state energy using inverse photoemission spectroscopy (IPES). New IPES results indicate that the unoccupied surface state intensity decreases with increasing annealing temperature. It was also found that the unoccupied surface state was shifted. IPES results provide that the contributions of the Y ¯ surface state to surface optical properties at 2.1 eV are relevant for the RAS technique.