Highly Enhanced Polarization Switching Speed in HfO₂-based Ferroelectric Thin Films via a Composition Gradient Strategy

The next-generation semiconductor memories are essentially required for the advancements in modern electronic devices. Ferroelectric memories by HfO2-based ferroelectric thin films (FE-HfO2) have opened promising directions in recent years. Nevertheless, improving the polarization switching speed of FE-HfO2 remains a critical task. In this study, it is demonstrated that the composition-graded Hf1-xZrxO2 (HZO) ferroelectric thin film has more than two times faster polarization switching speed than the conventional composition-uniform one. Meanwhile, it has excellent ferroelectricity and improved endurance characteristics. It is also discovered that when the HZO thin film has a gradient composition, the polarization-switching dynamics shifts from the nucleation-limited-switching mechanism to the domain-wall growth mechanism. Moreover, the transition of switching dynamics is responsible for the faster speed and better endurance of the composition-graded HZO thin film. These findings not only reveal the physical mechanisms of this material system but also provide a new strategy for memory devices having faster speed and higher endurance.