Nucleation and growth of nanophasic CeO2 thin films by plasma-enhanced CVD

Nanophasic CeO2-based thin films were grown at low temperatures on SiO2 and Si(100) by plasma-enhanced (PE) CVD from a Ce-IV beta-diketonate first generation precursor. Film depositions were carried out in low-pressure Ar-O-2 plasmas at temperatures between 150degreesC and 300degreesC. The film microstructure was investigated by glancing incidence X-ray diffraction (GIXRD) and transmission electron microscopy (TEM), while the surface and in-depth chemical composition was studied by X-ray photoelectron spectroscopy (XPS), and secondary ion mass spectrometry (SIMS), respectively. Optical properties were analyzed by UV-vis optical absorption. Nanostructured CeO2-based films, with crystal size less than 6 nm and a controllable Ce-IV/Ce-III ratio, were obtained at temperatures even lower than that required for precursor vaporization (170 degreesC). In particular, TEM analyses showed an island growth mode and different microstructural features as a function of the substrate used.