Interface Effects Induced by a Zr O 2 Seed Layer on the Phase Stability and Orientation of Hf O 2 Ferroelectric Thin Films: A First-Principles Study

${\mathrm{Hf}\mathrm{O}}_{2}$-based films have attracted much attention due to their robust ferroelectric properties at the nanometer scale and their great potential for data storage. The interface between the substrate and the ${\mathrm{Hf}\mathrm{O}}_{2}$-based film has a significant effect on its ferroelectric behavior. A seed layer between the films and substrates, such as a ${\mathrm{Zr}\mathrm{O}}_{2}$ seed layer, is proved to be an effective way to realize the beneficial interface effect. However, the interfacial tuning mechanism for the ferroelectric properties of ${\mathrm{Hf}\mathrm{O}}_{2}$-based thin films brought by the substrate or seed layer remains unclear so far. By performing first-principles calculations, the phase stability and crystalline orientation of ${\mathrm{Hf}\mathrm{O}}_{2}$ thin films on ${\mathrm{Zr}\mathrm{O}}_{2}$ seed layers are systematically studied. Results indicate that the ${\mathrm{Zr}\mathrm{O}}_{2}$ seed layer, especially the [111]-oriented one, substantially stabilizes the orthorhombic ferroelectric phase and the high-symmetry tetragonal phase of the ${\mathrm{Hf}\mathrm{O}}_{2}$ thin film compared with the most stable monoclinic phase. Furthermore, the polarization magnitude of the ${\mathrm{Hf}\mathrm{O}}_{2}$ film on the ${\mathrm{Zr}\mathrm{O}}_{2}$ seed layer is in good agreement with experiment. The [100]-oriented ${\mathrm{Zr}\mathrm{O}}_{2}$ seed layer also has a great effect on the stability of the orthorhombic ferroelectric phase of the ${\mathrm{Hf}\mathrm{O}}_{2}$ thin film. These results are meaningful for the understanding of the interfacial effects of the ferroelectricity of ${\mathrm{Hf}\mathrm{O}}_{2}$-based thin films and the development of ferroelectric devices.