PHOTOEMISSION OF THIN AND ULTRATHIN FILMS OF CALCIUM

We have investigated the differences between thick films and thin films. The thin calcium film was obtained by means of thermal evaporation and condensation under ultrahigh vacuum. The vacuum was in the range of 10-11 Torr and was obtained with an ion-pump, a titanium getter-pump and a helium cooled cryopump. The film structure depends on the quantity of metal deposited on the substrate. Three main structures were observed: granular, lacunar and continuous. Photoemission measurements were made with photons of 2 to 5.6 eV. Thus we were able to determine the density of electronic states just below the Fermi level and to study the dependence of the work function on structure. © 1979.