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 electronic devices, particularly suited to addressing the miniaturization and integration challenges of traditional perovskite-structured ferroelectric memory devices. HZO exhibits complex phase competition, requiring careful stabilization to achieve the desired properties. Numerous studies have sought solutions to balance monoclinic, orthorhombic, and tetragonal phases, as their interplay influences the macroscopic ferroelectric and antiferroelectric-like behaviors of the films. While recent research has focused on phase engineering in nanolaminates and multilayers to enhance ferroelectric properties, dielectric constant, and device performance, electrostatic control in multilayers remains less explored. In this study, we systematically investigate how polarization switching and the dielectric constant are affected by electrostatic interactions in multilayer structures. We analyze a wide range of samples beginning with simple layers of varying Hf/Zr compositions and thicknesses, followed by bilayers. Special attention is given to multilayers with alternating HZO compositions and HZO/dielectric (HZO/DE) structures to disentangle the contributions of electrostatic coupling, structural changes, and oxygen vacancy effects. Our findings reveal that electrostatic interactions can enhance the effective dielectric constant in multilayers, with significant amplification observed in HZO(30/70)_HZO(50/50) with 5 nm/5 nm thickness and ZrO₂_HZO(50/50) with 7 nm/7 nm thickness structures compared with simple layers. For multilayers where amplification is not observed, the main limiting factors are the coexistence of non-polar phases or a lack of control between FE and AFE-like characteristics. These results provide key insights into tailoring the dielectric response of HZO-based thin films and improving their ferroelectric performance. Electrostatic control is a clear pathway for tuning specific properties and enabling new potential applications. However, their effects can be weakened or misinterpreted without precise control over the phase ratio in HZO. Future research should refine processing conditions to achieve better phase control and enhance the stability of HZO-based materials for advanced electronic applications. • Electrostatic coupling in HZO multilayers boosts the dielectric constant to ∼80. • Internal fields from polarization mismatch enable dielectric amplification. • Non-polar phases or charge effects limit enhancement in some multilayer structures. • Study separates electrostatic, structural, and defect effects in HZO thin films.