Improving the Ferroelectric Properties of Nd:HfO₂ Thin Films by Stacking Hf₀.₅Zr₀.₅O₂ Interlayers

In this study, Nd:HfO $_{\text{2}}$ thin films with or without the Hf $_{\text{0.5}}$ Zr $_{\text{0.5}}$ O $_{\text{2}}$ (HZO) interlayer were prepared on Pt/Ti/SiO $_{\text{2}}$ /Si substrates by the chemical solution deposition (CSD) method. It was found that the HZO interlayer could effectively improve the ferroelectric properties of the Nd:HfO $_{\text{2}}$ thin films. The thin films with the HZO interlayer have a larger remanent polarization ( $\textit{P}_{\text{r}}$ $\approx $ 20.04 $\mu $ C/cm $^{\text{2}})$ and a smaller coercive field ( $\textit{E}_{\text{c}}$ $\approx $ 1.8 MV/cm) than that of the thin films without the HZO interlayer. Moreover, the endurance and retention performance of the metal–ferroelectric–metal–semiconductor (MFMS) structure is much better than that of the thin films without the HZO interlayer. Microscopic characterizations by XRD and high-resolution transmission electron microscopy (HRTEM) indicated that stacking the HZO interlayer can increase the content of the orthogonal phase, which helps to improve the ferroelectricity of the thin film. The stacking structure overcomes the problems of high leakage current and small polarization window for ferroelectric HfO $_{\text{2}}$ -based thin films. The results provide a valuable way for the preparation of ferroelectric HfO $_{\text{2}}$ -based thin films through the CSD method.