Enhanced ferroelectric performance in Hf0.5Zr0.5O2 capacitors using ultra-thin MoS2 layer for clamping effect and oxygen vacancy suppression

Abstract

Since the discovery of ferroelectric properties in HfO2-based thin films, capping effect has been extensively researched to induce ferroelectric orthorhombic phase through mechanical clamping. However, current research on capping materials has focused on oxide-based materials to address wake-up effect resulted from 3D metallic capping electrodes, yet the challenge of achieving a large double remnant polarization value remains unresolved. Here, ultra-thin (≈ 1 nm) MoS2, one of transition metal dichalcogenides, was employed as a novel capping layer on Hf0.5Zr0.5O2 thin films. Notably, MoS2-capped Hf0.5Zr0.5O2 films exhibited a higher orthorhombic phase fraction than uncapped films, resulting in an enhanced double remnant polarization value of ≈ 42.2 μC cm−2. This represents approximately a three-fold increase compared to the uncapped Hf0.5Zr0.5O2 films (≈ 14.8 μC cm−2), attributed to volumetric suppression via the clamping effect even with ultra-thin capping. Additionally, the MoS2-capped Hf0.5Zr0.5O2 device exhibited enhanced cycling limits (>106 cycles), achieved by suppressed oxygen vacancies at the top electrode-Hf0.5Zr0.5O2 film interface, thanks to the dangling bond-free nature of transition metal dichalcogenides. This study demonstrates that ultra-thin MoS2 effectively functions as a capping layer, enhancing both remnant polarization and endurance for 1T-1C FeRAM applications while preserving the scalability of Hf0.5Zr0.5O2. © 2025 The Author(s)