Geometric structure and electronic states of copper films on a ruthenium (0001) surface

Auger electron spectroscopy (AES), combined with thermal desorption mass spectroscopy (TDS), work function (Δφ) measurements and energy-dependent angular resolved UV photoemission using synchrotron radiation were used to investigate the geometric and electronic properties of submonolayer and monolayer copper films grown by vapor deposition on a clean Ru(0001) substrate. A pronounced influence of the deposition temperature on the morphology of the Cu films was established in that lower temperatures favor an island growth mechanism (Stranski-Krastanov or Volmer-Weber type), whereas higher deposition temperatures lead to a more uniform spreading and a layer-by-layer growth (Frank-van der Merwe type). For Cu films grown under the latter conditions angular resolved photoemission reveals the existence of two-dimensional Cu bands even before the monolayer has reached completion; the experimentally determined band dispersions agree quite well with recent theoretical calculations.