Improvement of crystallinity and surface roughness in epitaxial CeO2/Ce1−xZrxO2/Y0.15Zr0.85O1.93 buffer layers deposited on a Si(100) substrate by pulsed laser deposition
Epitaxial CeO2/Ce1¹xZrxO2/Y0.15Zr0.85O1.93 (YSZ) buffer layers were fabricated on a Si(100) substrate by pulsed laser deposition, and its crystallinity and surface roughness were analyzed. When Ce1¹xZrxO2 (x = 00.6) films were directly deposited on the Si(100) substrate, the films had a (111) or (111)-preferred orientation. In contrast, (100)-oriented epitaxial films of the Ce1¹xZrxO2 (x = 00.6) were obtained by introducing a 2.5-nm-thick YSZ buffer layer between Ce1¹xZrxO2 and Si. Lattice parameters and surface roughness of the Ce1¹xZrxO2 layers on the YSZ-buffered Si(100) decreased from 0.542 to 0.525nm (in-plane) and 0.47 to 0.12 nm, respectively, as the increase of x from 0 to 0.6. After that, an epitaxial CeO2/Ce0.4Zr0.6O2/YSZ buffer layer was fabricated on the Si substrate. Differences in lattice parameters between CeO2 and Ce0.4Zr0.6O2 and also between Ce0.4Zr0.6O2 and YSZ became about half of that between CeO2 and YSZ. As a result, surface roughness of the CeO2 layer on top of the Ce0.4Zr0.6O2/YSZ/Si and full width at half maximum of the rocking curve of the CeO2 (004) reflection became 0.18nm and 0.89 degrees, respectively, which were smaller than those of CeO2 layers deposited directly on YSZ/Si.
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