PNNL

Abstract

Multi-layer films of pure ZrO2 and CeO2 were grown using molecular beam epitaxy on a yttria-stabilized zirconia (YSZ) substrate. Distinctive forbidden diffraction spots of (odd, odd, even) type were observed on the selected area electron diffraction patterns of the film. Dark-field imaging clearly revealed that these forbidden diffraction spots were solely due to the ZrO2 layers. Comparison of the electron diffraction pattern with one simulated by dynamical calculations suggest that the pure ZrO2 layers possess a cubic structure of space group with the oxygen sub-lattice being displaced diagonally, rather than along the c-axis as suggested for YSZ. Our results further suggest that the displacement of the oxygen from the ideal (¼,¼,¼) position might have been introduced during the film growth process.