Understanding the role of the dielectric (DE) layer in ferroelectric (FE) Hf_0.5Zr_0.5O₂ (HZO) based devices (e.g., ferroelectric-field-effect-transistors, FE-FETs) is important to enable their application-driven optimizations. To that end, in this work, we systematically investigate the polarization switching mechanisms in FE–DE stacks and analyze their dependence on the dielectric layer thickness (T_DE). First, we fabricate a HZO–Al₂O₃ (FE–DE) stack and experimentally demonstrate a decrease in remanent polarization and an increase in coercive voltage with an increase in T_DE. As such dependencies are out of the scope of commonly used single domain polarization switching models, therefore, we argue that the consideration of the multi-domain model is essential for analyzing the polarization switching in HZO. Then, using phase-field simulations of the FE–DE stack, we show that an increase in T_DE results in a larger number of reverse domains in the FE layer to suppress the depolarization field, which leads to a decrease in the remanent polarization and an increase in the coercive voltage. Furthermore, our analysis signifies that the polarization switching mechanism in HZO can be modulated from domain-nucleation based to domain-wall motion based by increasing the T_DE and that can serve as a potential knob for application-specific optimization of FE-FETs. In addition, we show that the effective polarization–voltage characteristics of the FE layer in the FE–DE stack exhibit a negative slope region that leads to the charge enhancement effects in the FE–DE stack. While such effects are most commonly misinterpreted as either the transient effects or the stabilized single-domain negative capacitance effects, we demonstrate that the appearance of a negative slope in the hysteretic polarization–voltage characteristics is quasi-static in nature and that originates from the multi-domain polarization switching in the FE.

中文翻译：

---

Hf0.5Zr0.5O2-电介质堆栈中的极化转换：电介质层厚度的作用

了解电介质 (DE) 层在基于铁电 (FE) Hf _0.5 Zr _0.5 O ₂ (HZO) 的器件（例如，铁电场效应晶体管、FE-FET）中的作用对于实现其应用驱动的优化非常重要. 为此，在这项工作中，我们系统地研究了 FE-DE 堆叠中的极化切换机制，并分析了它们对介电层厚度 ( T _DE )的依赖性。首先，我们制造了 HZO-Al ₂ O ₃ (FE-DE) 叠层，并通过实验证明随着T _DE的增加剩余极化减少和矫顽电压增加. 由于这种依赖性超出了常用的单域极化切换模型的范围，因此，我们认为多域模型的考虑对于分析 HZO 中的极化切换至关重要。然后，使用FE-DE堆叠的相场的模拟，我们表明，增加Ť _DE导致反向域的更大数量的FE层来抑制去极化场，从而导致在剩余极化的降低和矫顽电压的增加。此外，我们的分析表示该偏振在HZO切换机构可从基于通过增加基于域的壁运动域成核调制Ť _DE这可以作为 FE-FET 特定应用优化的潜在旋钮。此外，我们表明 FE-DE 堆栈中 FE 层的有效极化电压特性表现出负斜率区域，导致 FE-DE 堆栈中的电荷增强效应。虽然这种效应最常被误解为瞬态效应或稳定的单域负电容效应，但我们证明了滞后极化电压特性中负斜率的出现本质上是准静态的，并且源于多FE中的-域极化切换。