Properties of CeO_2 thin films prepared by oxygen-ion-assisted deposition

Thin films have been prepared by electron-beam evaporation of CeO2, where the growing film has been bombarded with oxygen ions. The packing density of the films has been increased from ∼0.55 without ion bombardment to unity with bombardment as determined by moisture adsorption measurements. The refractive index, extinction coefficient, and scattering loss are reported for a range of ion energies from 50 to 1200 eV. The ratio of ion-current density to film growth rate required to produce films that did not adsorb moisture was found to be a minimum for ion energies in the 300–600-eV range. Absorption and scatter losses are smallest for the lower ion energies and the crystal structure of CeO2 films is relatively stable under ion bombardment although ion-assisted films tend to be less crystalline than evaporated layers.