Abstract
Gdolinia doped ZrO 2 and CeO 2 multi-layer films were deposited on α-Al 2O 3 (0001) using oxygen-plasma-assisted molecular-beam epitaxy. Oxygen vacancies and Gd dopant distributions were investigated in these multi-layer films using X-ray diffraction (XRD), conventional and high-resolution transmission electron microscopy (HRTEM), annular dark-field imaging in scanning transmission electron microscopy (STEM), X-ray energy dispersive spectroscopy (EDS) elemental mapping and X-ray photoelectron spectroscopy (XPS) depth profiling. EDS and XPS depth profiling reveal that the Gd concentration in the ZrO 2 layer is lower than that in the CeO 2 layer. As a result, a higher oxygen vacancy concentration exists in the CeO 2 layers compared to that in the ZrO 2 layers. In addition, Gd is found to segregate only at the interfaces formed during the deposition of CeO 2 layers on ZrO 2 layers. On the other hand, the interfaces formed during the deposition of ZrO 2 layers on CeO 2 layers did not show any Gd segregation. The Gd segregation behavior at every other interface is believed to be associated with the low solubility of Gd in ZrO 2.
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