Structural and optical properties of polycrystalline thin films of rare earth oxides grown on fused quartz by low pressure MOCVD

We report the structural and optical properties of oriented polycrystalline thin films of rare earth oxides (REO), namely Er2O3, Gd2O3, Eu2O3, and Yb2O3 grown on fused quartz by low-pressure metalorganic chemical vapour deposition (MOCVD) in the temperature range of 450-800 °C, using adducted β-diketonate complexes of rare earth metals as precursors. The films were characterized by X-ray diffraction (XRD) and UV-visible spectrophotometry. While the films grown at low temperatures (∼500 °C) are poorly crystalline, those grown on or above 525 °C display a significant (1 1 1) texture. Growth of textured cubic REO in (1 1 1) direction on amorphous substrate is interpreted in terms of minimization of surface energy at the film-substrate interface. The degree of misfit between the interatomic distances in the disordered fused quartz substrate and those in the crystalline REO is invoked to explain the presence (absence) of low-intensity reflections other than (1 1 1). The incorporation of carbon (from the precursor) into the films affects the optical properties of REO, as examined by UV-visible spectroscopy.