| AVS 55th International Symposium & Exhibition | |
| Thin Film | Thursday Sessions |
| Session TF-ThP |
| Session: | Aspects of Thin Films |
| Presenter: | P. Nachimuthu, Pacific Northwest National Laboratory |
| Authors: | P. Nachimuthu, Pacific Northwest National Laboratory S.V.N.T. Kuchibhatla, Pacific Northwest National Laboratory F. Gao, Pacific Northwest National Laboratory V. Shutthanandan, Pacific Northwest National Laboratory M.H. Engelhard, Pacific Northwest National Laboratory Z.Q. Yu, Nanjing Normal University, China C.M. Wang, Pacific Northwest National Laboratory S. Seal, University of Central Florida S. Thevuthasan, Pacific Northwest National Laboratory W. Jiang, Pacific Northwest National Laboratory |
| Correspondent: | Click to Email |
Cerium oxide based materials are widely used in catalysis, solid oxide fuel cells (SOFCs), and for microelectronic applications. Performance of this functional oxide in various applications is dependent on the crystallographic planes of ceria and their participation in various chemical reactions. High-quality ceria (CeO2) films were grown on sapphire, (Al2O3), (0001) substrates using oxygen plasma-assisted molecular beam epitaxy. The epitaxial orientation of the ceria films has been found to be (100) and (111) at low (< 8 Å/min) and higher growth rates (up to ~30 Å/min), respectively. Reflection high energy electron diffraction (RHEED) measurements show that CeO2 (100) film grows as three-dimensional islands, while CeO2 (111) proceeds with layered growth. In CeO2(100) films, although the growth appears to be 3-D island growth, Rutherford backscattering spectrometry (RBS) measurements along channeling geometry clearly demonstrates that the films have high crystalline quality in comparison to CeO2(111) films. X-ray diffraction (XRD) measurements show that there are three in-plane domains in the CeO2 (100) film and those are attributed to the three-fold symmetry in Al2O3 (0001) surface. Molecular dynamics (MD) simulations have been carried out to understand the stability of different orientations of ceria on the sapphire (0001) substrate. The experimental observations have been supported very well by the simulations. Excellent oxygen sub-lattice match between sapphire and ceria are proposed as a major driving force for achieving high quality epitaxial films, as opposed to oriented, polycrystalline films. High resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM) measurements have been carried to study the structure and surface morphology of the ceria films. X-ray photoelectron spectroscopy measurements were used to find the oxidation state of cerium in the as-grown films.