OPTICAL AND STRUCTURAL-PROPERTIES OF REACTIVE ION-BEAM SPUTTER-DEPOSITED CEO2 FILMS

Optical and structural properties of reactive ion beam sputter deposit ed CeO2 films as a function of oxygen partial pressures (P-O2) and sub strate temperatures (T-s) have been investigated. The films deposited at ambient temperature with P-O2 of 0.01 Pa have shown a refractive in dex of 2.36 which increased to 2.44 at 400 degrees C. Refractive index and extinction coefficient are sensitive up to a T-s of similar to 20 0 degrees C. Raman spectroscopy and X-ray diffraction (XRD) have been used to characterise the structural properties. A preferential orienta tion of (220) was observed up to a T-s of 200 degrees C and it changed to (200) at 400 degrees C: and above. Raman line broadening, peak shi ft and XRD broadening indicate the formation of nanocrystalline phase for the films deposited up to a substrate temperature of 300 degrees C . However, crystallinity of the films were better for T-s values above 300 degrees C. In general both optical and structural properties were unusual compared to the films deposited by conventional electron beam evaporation, but were similar in some aspects to those deposited by i on-assisted deposition. Apart from thermal effects, this behavior is a lso attributed to the bombardment of backscattered ions/neutrals on th e growing film as well as the higher kinetic energy of the condensing species, together resulting in increased packing density. (C) 1997 Els evier Science S.A.