Ferroelectricity and Antiferroelectricity of Doped Thin HfO₂‐Based Films

TLDR

Recent advances show that doped HfO₂ thin films exhibit ferroelectricity and antiferroelectricity, offering a promising alternative to conventional perovskite ferroelectrics that suffer from poor Si‑compatibility, environmental concerns, and large thickness. The study aims to explore the coupled electric‑thermal behavior of antiferroelectric HfO₂ films for applications such as energy harvesting, solid‑state cooling, and infrared sensing. Doping HfO₂ with elements like Si, Zr, Al, Y, Gd, Sr, or La induces ferroelectric or antiferroelectric phases. Doped HfO₂ films exhibit remanent polarization up to 45 μC cm⁻², coercive fields 1–2 MV cm⁻¹, thicknesses below 10 nm, and bandgaps above 5 eV, surpassing conventional ferroelectrics and enabling high‑performance memory devices.

Abstract

The recent progress in ferroelectricity and antiferroelectricity in HfO 2 ‐based thin films is reported. Most ferroelectric thin film research focuses on perovskite structure materials, such as Pb(Zr,Ti)O 3 , BaTiO 3 , and SrBi 2 Ta 2 O 9 , which are considered to be feasible candidate materials for non‐volatile semiconductor memory devices. However, these conventional ferroelectrics suffer from various problems including poor Si‐compatibility, environmental issues related to Pb, large physical thickness, low resistance to hydrogen, and small bandgap. In 2011, ferroelectricity in Si‐doped HfO 2 thin films was first reported. Various dopants, such as Si, Zr, Al, Y, Gd, Sr, and La can induce ferro­electricity or antiferroelectricity in thin HfO 2 films. They have large remanent polarization of up to 45 μC cm −2 , and their coercive field (≈1–2 MV cm −1 ) is larger than conventional ferroelectric films by approximately one order of magnitude. Furthermore, they can be extremely thin (<10 nm) and have a large bandgap (>5 eV). These differences are believed to overcome the barriers of conventional ferroelectrics in memory applications, including ferroelectric field‐effect‐transistors and three‐dimensional capacitors. Moreover, the coupling of electric and thermal properties of the antiferroelectric thin films is expected to be useful for various applications, including energy harvesting/storage, solid‐state‐cooling, and infrared sensors.