On the local electronic and atomic structure of Ce_1-xPr_xO_2-δ epitaxial films on Si

Journal Article · Sun Sep 28 00:00:00 EDT 2014 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4896590· OSTI ID:22305700

Niu, Gang; Schubert, Markus Andreas; Zoellner, Marvin Hartwig ^[1]; D'Acapito, Francesco ^[2]; Schroeder, Thomas ^[1]; Boscherini, Federico ^[2]

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1. IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany)
2. Consiglio Nazionale delle Ricerche, Istituto Officina dei Materiali, Operative Group in Grenoble, c/o European Synchrotron Radiation Facility, B.P. 220, 38043 Grenoble (France)

The local electronic and atomic structure of (111)-oriented, single crystalline mixed Ce_1-xPr_{xO2-δ (x = 0, 0.1 and 0.6) epitaxial thin films on silicon substrates have been investigated in view of engineering redox properties of complex oxide films. Non-destructive X-ray absorption near edge structure reveals that Pr shows only +3 valence and Ce shows only nominal +4 valence in mixed oxides. Extended x-ray absorption fine structure (EXAFS) studies were performed at K edges of Ce and Pr using a specially designed monochromator system for high energy measurements. They demonstrate that the fluorite lattice of ceria (CeO₂) is almost not perturbed for x = 0.1 sample, while higher Pr concentration (x = 0.6) not only generates a higher disorder level (thus more disordered oxygen) but also causes a significant reduction of Ce–O interatomic distances. The valence states of the cations were also examined by techniques operating in highly reducing environments: scanning transmission electron microscopy-electron energy loss spectroscopy and X-ray photoemission spectroscopy; in these reducing environments, evidence for the presence of Ce³⁺ was clearly found for the higher Pr concentration. Thus, the introduction of Pr³⁺ into CeO₂ strongly enhances the oxygen exchange properties of CeO₂. This improved oxygen mobility properties of CeO₂ are attributed to the lattice disorder induced by Pr mixing in the CeO₂ fluorite lattice, as demonstrated by EXAFS measurements. Thus, a comprehensive picture of the modifications of the atomic and electronic structure of Ce1-xPrxO2-δ epitaxial films and their relation is obtained.}

• OSTI ID: 22305700
• Journal Information: Journal of Applied Physics, Vol. 116, Issue 12; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION
ABSORPTION SPECTROSCOPY
CARRIER MOBILITY
CERIUM IONS
CERIUM OXIDES
CONCENTRATION RATIO
ELECTRONIC STRUCTURE
ENERGY-LOSS SPECTROSCOPY
EPITAXY
FINE STRUCTURE
MONOCRYSTALS
PHOTOEMISSION
PRASEODYMIUM IONS
PRASEODYMIUM OXIDES
SILICON
SUBSTRATES
THIN FILMS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY SPECTROSCOPY