Ferroelastic Domain Switching and Time-Resolved Negative Capacitance in Polar-Axis-Oriented Hf_0.5Zr_0.5O₂ Grown by...

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Ferroelectric properties of Hf_0.5Zr_0.5O₂ are critically dependent on crystallographic orientation, with the [001] direction acting as the polar axis.
• Achieving epitaxial growth of Hf_0.5Zr_0.5O₂ layers with a highly polar [001] orientation and significant ferroelectricity remains a challenge.

Purpose of the Study:

• To demonstrate the epitaxial growth of (001)-oriented Hf_0.5Zr_0.5O₂ thin films using atomic layer epitaxy (ALE).
• To investigate the ferroelectric properties, domain switching mechanisms, and negative capacitance effects in these precisely engineered films.

Main Methods:

• Atomic Layer Epitaxy (ALE) for controlled thin film deposition.
• Plane-view precession electron diffraction for analyzing crystallographic orientation and reorientation.
• Ferroelectric measurements to quantify polarization and switching dynamics.
• Time-resolved measurements to study negative capacitance effects.

Main Results:

• Epitaxial (001)-oriented Hf_0.5Zr_0.5O₂ thin films were successfully grown, achieving a record ferroelectric polarization of 78.9 µC cm^-2.
• A lattice reorientation from (010) to (001) during the wake-up process was observed, explained by a two-step, 90° ferroelastic domain switching model.
• Polarization switching dynamics correlated with time-resolved negative capacitance, quantified as an equivalent high dielectric constant of -170.

Conclusions:

• ALE is a powerful technique for controlling the crystallographic orientation of Hf_0.5Zr_0.5O₂ thin films, crucial for enhancing ferroelectricity.
• The study provides fundamental insights into ferroelectric domain switching mechanisms and the manifestation of negative capacitance in ferroelectric materials.
• This work paves the way for advanced ferroelectric devices leveraging precisely oriented Hf_0.5Zr_0.5O₂ films.