Fig. 1: CeO2/Y2O3 nanobrush and the atomic configurations of the (111) interface.
From: Colossal oxygen vacancy formation at a fluorite-bixbyite interface
a A cross-sectional HAADF-STEM image of a [(CeO2)6 u.c./(Y2O3)2 u.c.]200 nanobrush superlattice with a thickness of 1.4 μm grown on a (001) YSZ-buffered silicon substrate, taken along the [110] direction. Because of the nonuniform thickness of sublayers originating from faceting, we use the average thickness of the individual layers. Note that oxide nanostructures were grown on (001) YSZ-buffered silicon substrates, as TEM imaging for samples grown directly on YSZ was difficult because of severe charging of electrons. The scale bar corresponds to 50 nm. b Atom probe tomography (APT) reconstruction with Ce and Y atoms displayed as red and blue points, respectively, showing a three-dimensional view of the free-standing [(CeO2)6 u.c./(Y2O3)2 u.c.]200 internal structure. The scale bar corresponds to 20 nm. c Schematic of a (111) interface between CeO2 (fluorite) and Y2O3 (bixbyite), in which red and blue circles represent oxygen atoms in CeO2 and Y2O3, respectively. Cations are not shown. The (111) Y2O3/CeO2 interface is a combination of three different anion arrays, C1, C2, and C3. A cross-section of the C1 array shows a perfect match between numbers of oxygen atoms on interfacing CeO2 and Y2O3 sides. In contrast, on the Y2O3 side of the interface, a cross-section shows on average one oxygen vacancy every four sites in the C2 array and one oxygen vacancy every two sites in the C3 array.
