Optical properties of ion assisted deposited CeO2 films

Abstract

Single layer films of CeO2 have been deposited both by conventional electron beam evaporation and ion assisted deposition with oxygen and argon ions. A broad beam Kaufman ion source (3 cm diam) has been used to generate the ions. A systematic study has been made on optical properties such as refractive index, extinction coefficient and inhomogeneity of the films as a function of: (1) oxygen partial pressure in the range 1×10−4 to 1×10−5 mbar. (2) Incidence of oxygen ions with energy in the range 300–700 eV and current density in the range 50–220 μA/cm2. (3) Incidence of mixed argon and oxygen ions of different ratios. The refractive index of the films deposited under the influence of ion bombardment showed higher indices than the conventionally evaporated films. The maximum index obtained with an oxygen ion bombardment was 2.3 at an ion energy of 600 eV and current density of 220 μA/cm2. The bombardment of the films with a mixed argon–oxygen (25% Ar) ion beam of the same energy and current density was found to further increase the refractive index. The extinction coefficient in both cases was negligible.