Influence of ultra-thin YSZ layer on heteroepitaxial CeO₂/YSZ/Si(0 0 1) films analyzed by X-ray reciprocal space map

The heteroepitaxial CeO₂(0 0 1)/YSZ(0 0 1)/Si(0 0 1) films with various YSZ thicknesses, from 0.5 to 36.0 nm, were prepared by pulsed laser deposition (PLD). The film structure was characterized mainly by reciprocal space mapping performed on a high-resolution X-ray diffraction. In the case of 0.5 nm thick YSZ, the out-of-plane and in-plane lattice constants (a_n, a_p) of CeO₂ are much closer to Si, almost without tetragonal distortion. As the YSZ thickness increases above 0.5 nm, the CeO₂ lattice is a tetragonal distortion with larger a_p and smaller a_n. Besides, the CeO₂ layer with 0.5 nm thick YSZ shows a wider dispersion of smaller mosaic domains, larger crystallographic tilt, and less strain condition than other YSZ thickness.