Zainab Jaf
Murdoch University, Australia
Title: Geometries, Electronic Properties and Stability of Molybdenum and Tungsten Nitrides Low-Index Surfaces
Biography
Biography: Zainab Jaf
Abstract
Ce-oxide thin film coatings present unique optical properties. In this study, structural, chemical bonding and optical properties of the thin films in relation to the composition of reaction gas via sputtering process were investigated. All the thin films exhibited a polycrystalline character with cubic fluorite – structure for cerium dioxide along (111), (200) and (222) orientations. XPS analysis revealed that two oxidation states of CeO2 and Ce2O3 are present in the films prepared at lower argon- oxygen flow ratios, whereas the films are totally oxidized into CeO2 as the aforementioned ratio increases. Optical parameters (α ε1, ε2, n and k) derived from UV-Vis reflectance data indicate that the thin films have indirect optical band gaps in the range of 2.25 - 3.1 eV. Density functional theory (DFT+U) implemented in the Cambridge Serial Total Energy Package (CASTEP), has been employed to model some optical properties of CeO2 cluster at ground state. The simulated electronic density of state (DOS) of the relaxed structure of CeO2 demonstrates a band gap agrees well with the measured optical band gap. The experimental and calculated absorption coefficient (α), have analogous trends and to some extent a similar range of values in the wave length. All in all, our theoretical findings consistently support the experimental results.