An angle-resolved photoemission study of the chemisorption of chalcogens on Cu(100): I. The clean surface

Abstract

We have performed angle-resolved photoemission (ARPES) experiments on Cu(100) as a first step towards studying oxygen and sulfur chemisorption on this surface. Normal emission spectra were obtained on the photon energy range hv = 9 to 34 eV using synchrotron radiation at the Stanford Synchrotron Radiation Laboratory. Both energy distribution curves and constant final state spectra were taken. Using the three-step direct-transition model, experimental dispersion curves were measured which agrees well with the band structure of Janak, Williams, and Moruzzi. Their calculation includes an 8% self-energy correction to account for electron electron interactions. The best agreement (within 0.1 eV) between theoretical and experimental results is obtained in the vicinity of the Fermi level. The largest differences (0.3 to 0.8 eV) occur for the lowest Δ 1 band. Polarization selection rules were used to identify band symmetry. Umklapp processes were apparently observed at higher photon energies where more than one final-state band was accessible. Changes in the electron analyzer angular resolution were found to affect peak positions where bands showed strong dispersion and relative peak intensity. Evidence for a surface state in the sd-hybridization gap is considered. The utility of the three-step model is evaluated.