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Tuesday, August 12 • 14:30 - 16:30
Complex Oxides III

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14:30-15:00

Invited: Scott Chambers
Redox-Induced Metal-Insulator Transition in MBE-Grown SrCrO3
Co-authors: Hongliang Zhang, Peter Sushko, Robert Colby, Yingge Du, Mark Bowden

The wide range of properties exhibited by complex oxides (CO) is due to the high degree of solubility on cation sites, and the range of charges exhibited by transition metal (TM) cations. At the same time, the limitations that TM cations impose on the CO is a reality that must be dealt with in synthesizing these materials. We illustrate these principles with the cubic perovskite SrCrO3, as prepared by molecular beam epitaxy. If perfectly stoichiometric, SrCrO3 should be a metal by virtue of an incompletely filled majority spin Cr 3d t2g derived band at the top of the valence band. However, the material is a semiconductor as deposited. The reason for this unexpected behavior is that what actually nucleates is rhombohedral SrCrO2.8, which contains a mix of Cr(III) and Cr(IV). The primary driver for SrCrO2.8 nucleation is that Cr(IV) is not stable in octahedral coordination, as found in cubic perovskite, but is stable in tetrahedral coordination. SrCrO2.8 contains oxygen deficient planes of {111}-oriented SrO2 sandwiched by layers of tetrahedrally-coordinated Cr(IV). Between these lamella are layers of SrO3 and octahedrally-coordinated Cr(III). SrCrO2.8 can be reversibly oxidized to metallic perovskite SrCrO3-δ at atmospheric pressure and relatively low temperatures (250C for oxidation and 500C for reduction), thus exhibiting a metal-to-semiconductor transition. Rapid, low-temperature oxidation occurs because SrCrO2.8 forms a quasi-2D nanostructure which facilitates fast oxide anion diffusion.

15:00-15:15
Oral: A. Srivastava
Lattice Distortions in Complex Oxides & Their Relation to the Thermal Properties
Co-author: N. K. Gaur

15:15-15:30
Oral: S. Zollner
Dielectric Function of NiO from 25 meV to 6 eV: Comparison with Silicon
Co-authors: Cayla M. Nelson, Travis I. Willett-Gies, Ayana Ghosh

15:30-15:45
Oral: R. Schmidt-Grund
Electronic Transitions & Dielectric Function Tensor in the NIR-VUV Spectral Range of YMnO3 Single Crystal
Co-authors: Steffen Richter, Stefan Ebbinghaus, Michael Lorenz, Carsten Bundesmann, Marius Grundmann

15:45-16:00
Oral: R. Dargis
Chemical & Structural Properties of Multilayer Rare-Earth Oxide Buffer for GaN MOCVD on Si
Co-authors: Andrew Clark, Erdem Arkun, Robin Smith, Tomas Grinys, Agne Kalpakovaite, Roland Tomasiunas

16:00-16:15
Oral: A. Posadas
Epitaxial In-Plane Dimerized NbO2 Thin Films
Co-authors: Andrew O'Hara, Sylvie Rangan, Robert Bartynski, Alexander Demkov

16:15-16:30
Oral: A. Natan
New Metal Oxides for Photovoltaics - Experimental & Theoretical Challenges 
Co-authors: Mivsam Yekutiel, Arie Zaban 

Session Chairs
MK

Masashi Kawasaki

Professor & Deputy Director, The University of Tokyo & RIKEN Center for Emergent Matter Science
Dr. Kawasaki has contributed significantly to developing advanced technologies for realizing atomic scale control in oxide thin film epitaxy. He has developed the combinatorial epitaxy technique which facilitates efficient means of fabricating many thin films with various compositions and/or structures on a substrate simultaneously. Based on these technologies, he has expanded the physics, functionality, and applications of the field of oxide... Read More →

Speakers
SC

Scott Chambers

Materials Sciences Laboratory Fellow, Pacific Northwest National Laboratory
Dr. Chambers is the Technical Group Leader for the PNNL Oxide Epitaxy Group. He has focused on the preparation and properties of model surfaces and interfaces for his entire career. His interests have ranged from metals to conventional Group IV and Group III-V semiconductors to simple and complex oxides. His current interests focus on the effects of doping on the structure and functional properties of epitaxial oxide films of various kinds... Read More →


Tuesday August 12, 2014 14:30 - 16:30
Room 19A

Attendees (9)