Growth of CeO2 films on sapphire and MgO by rf magnetron sputtering

Epitaxial CeO2 films on (1 bar 102) sapphire and (100) MgO were grown by rf magnetron sputtering. Substrate temperature, total pressure, and oxygen-to-argon mole ratio were varied to explore the optimal deposition condition. The X-ray diffraction spectra indicate that the degree of crystallinity of the deposited CeO2 films depends on the oxygen-to-argon mole ratio and the substrate temperature. Atomic force microscopy images of the films on sapphire and MgO showed that substrate temperature and total pressure affect surface roughness. The best film surface is smooth with a 0.89 nm root-mean-square roughness. The quality of the films on MgO showed a strong dependence on substrate pretreatments. Epitaxial CeO2 films could be grown on preannealed or pre-etched MgO if substrate temperatures reached higher than 790 C. Additionally, the effect of ion bombardment at low total pressures on the crystallinity of the films was examined by growing the films outside these plasma region. Experimental results indicate that the ion bombardment does not prevent the films from preferred orientation