Effects of thermal coefficient and lattice constant mismatches on mosaic dispersion of heteroepitaxial YSZ/Si(001) thin films

The heteroepitaxial yttria-stabilized ZrO2 (YSZ) films on Si(001) substrates with various nano-grade thicknesses from 1.5 to 145 nm were prepared by pulsed laser deposition. Both the thermal coefficient mismatch and lattice constant mismatch effects on the high-thermal- and lattice- mismatch YSZ/Si(001) films have been studied mainly by the high-resolution x-ray diffraction. The curvatures and in-plane and out-of-plane lattice constants of film and substrate were measured by the high-resolution x-ray diffraction. The experimental radius of the overall curvature has a good agreement with the thermal coefficient mismatch model, indicating that the thermal residual stress similar to1.7 GPa is the main stress source in this kind of film system. Furthermore, the film mosaic structure shows a fan-like uniform tilt with a radius in the inversed direction with respect to that of substrate. The huge tension stress of thermal coefficient mismatch provides an enhanced effect on the intrinsic mosaic dispersion of film geometrically. A possible misfit dislocation distribution was described for the huge mosaic tilt.