Field-Induced Structural Dynamics of Polarization Switching in Hf_xZr_1-xO₂ Thin Films

Area of Science:

• Materials Science
• Solid-State Physics
• Crystallography

Background:

• The functionality of hafnium-zirconium oxide (HZO) in ferroelectric (FE) and antiferroelectric (AFE) devices depends on its polarization characteristics.
• Understanding the structural evolution during polarization switching in HZO is crucial for device optimization but remains poorly understood.

Purpose of the Study:

• To elucidate the switching mechanism and phase evolution in HZO thin films during polarization switching.
• To provide unambiguous evidence of phase transitions across various HZO compositions.

Main Methods:

• Combined in situ microbeam grazing incidence X-ray diffraction (GIXRD).
• First-principles-based metadynamics simulations.

Main Results:

• Switching involves reversible transitions between nonpolar tetragonal (t) P4₂/nmc and polar orthorhombic (o) Pca2₁ phases in HZO (x=0 to 0.5).
• Zr-rich AFE compounds exhibit a complete t-phase transition during polarization reversal.
• Hf-rich FE compounds show transient t-phase formation, enabling nucleation and growth of reversed o-phase domains.

Conclusions:

• The study clarifies the switching mechanism in HZO thin films, detailing phase evolution.
• Findings promote the engineering of phase evolution in HZO for the development of advanced FE and AFE devices.