Tailoring polarization and dielectric properties in HZO multilayers: Electrostatic Effects vs. structural instabilities

Ferroelectric hafnium-zirconium oxide (HZO) is a promising material for next-generation electronics, well-suited to address the miniaturization and integration challenges of traditional perovskite-based ferroelectric memories. Due to complex phase competition, HZO requires careful stabilization to obtain the desired properties. Many studies have aimed to balance the monoclinic, orthorhombic, and tetragonal phases, whose interplay governs the macroscopic ferroelectric and antiferroelectric-like behavior of the films. While recent work has focused on phase engineering in nanolaminates to enhance performance, electrostatic control in multilayers remains underexplored. In this study, we systematically investigate how electrostatic interactions in multilayer structures affect polarization switching and dielectric constant. We analyze a broad set of samples, from simple layers with varying Hf/Zr ratios and thicknesses to bilayers. Special focus is placed on multilayers with alternating HZO compositions and HZO/dielectric (HZO/DE) stacks to separate the effects of electrostatic coupling, structural changes, and oxygen vacancies. Our results show that electrostatic interactions can enhance the effective dielectric constant, with notable amplification in HZO(30/70)_HZO(50/50) (5 nm/5 nm) and ZrO₂_HZO(50/50) (7 nm/7 nm) compared to simple layers. In cases where no amplification is observed, the main limiting factors are the presence of non-polar phases or insufficient control over FE and AFE-like traits. These findings offer valuable insights for tuning the dielectric response of HZO-based films and improving ferroelectric performance. While electrostatic control can unlock new functionalities, it relies on precise phase ratio control in HZO.