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Channeling Studies of CeO2 and Ce1-xZrxO2 Films on Yttria-Stabilized ZrO2(111) V. Shutthanandan1, S. Thevuthasan1, Y. J. Kim2, and C.H.F. Peden1 1 Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352, USA 2 Department of Chemical Technology, Taejon National University of Technology, South Korea

ABSTRACT

Rutherford backscattering spectrometry and channeling techniques have been used to investigate the crystalline quality and interfacial properties of epitaxially grown CeO2 and Ce0.7Zr0.3O2 films on yttria-stabilized ZrO2(111) substrates. Both films appear to have high crystalline quality with minimum yield of Ce in the CeO2 and Ce0.7Zr0.3O2 films determined to be 4.7% and 12.1% respectively. Visibility of more Ce atoms to the ion beam at the interface compared to the bulk of the film indicates that both films show significant disorder at the interface. The normalized angular yield curves obtained from Ce and Zr indicate that the Ce atomic rows in the CeO2 film are parallel to the Zr atomic rows in the substrates. Approximately 88% of the Zr atoms substitutionally occupy the Ce cation lattice sites in the Ce0.7Zr0.3O2 film.

INTRODUCTION

There is a growing interest in the epitaxial growth of model oxides on various oxide and metal substrates to obtain high-quality surfaces and films. A number of single crystal oxide films on various substrates have been recently synthesized in our laboratory using molecular beam epitaxial growth. Cerium oxide and Ce1-xZrxO2 have received much attention in the recent past because of their technological application in noble-metal/alumina based automotive exhaust catalysts [1]. Pure CeO2 has the ability to store and release oxygen under reaction conditions and its thermal stability as well as its storage and release properties can be significantly improved by adding ZrO2. In addition, CeO2 is an attractive candidate for high-dielectric materials on semiconductors because of its large band gap and high dielectric constant [2]. Recently, we have synthesized several high-quality, well-oriented single crystal CeO2 and Ce1-xZrxO2 films with various stoichiometries and thicknesses using molecular beam epitaxial (MBE) growth methods [3,4]. Although these films are well characterized using surface science techniques [3,4], bulk characterization associated with crystalline quality and the film/substrate interface is somewhat limited. The goal of the present work is to investigate the crystalline quality and the nature of the film/substrate interface in CeO2 and Ce1-xZrxO2 thin films grown on yttria-stabilized ZrO2 substrates using Rutherford backscattering spectrometry and channeling (RBS/C) techniques. Rutherford backscattering spectrometry, when used in the channeling mode, provides a powerful tool to probe the substrate surface structure, as well as overlayer and interface structures [5,6]. In the channeling geometry, the ion beam is incident along a low-index crystallographic direction of the substrate, and the energy spectrum of backscatte