Sharp Transformation across Morphotropic Phase Boundary in Sub-6 nm Wake-Up-Free Ferroelectric Films by Atomic Layer...

Area of Science:

• Materials Science
• Solid State Physics
• Thin Film Technology

Background:

• Ferroelectric materials are crucial for advanced electronic devices.
• Tailoring phase boundaries is key to optimizing ferroelectric properties.
• Atomic layer deposition (ALD) offers precise control over thin film growth.

Purpose of the Study:

• To investigate atomic layer engineering for controlling the morphotropic phase boundary (MPB) in HfO2/ZrO2 thin films.
• To achieve enhanced ferroelectric properties in sub-6 nm films.
• To elucidate the relationship between grain size and phase evolution.

Main Methods:

• Atomic layer deposition (ALD) of HfO2 seeding layers and ZrO2 films.
• Helium ion microscopy (HIM) for high-resolution surface imaging.
• Analysis of ferroelectric properties (remanent polarization, wake-up behavior).

Main Results:

• A 2-monolayer HfO2 seed layer induced a phase transition across the MPB in ZrO2.
• Record-high remanent polarization (≈60 µC cm⁻²) and wake-up-free operation were achieved in sub-6 nm films.
• In-plane tensile stress from HfO2 was identified as the cause of the antiferroelectric to ferroelectric transformation.
• Grain size reduction was shown to drive crystallization from tetragonal to polar orthorhombic phases.

Conclusions:

• Atomic layer engineering provides a pathway to tailor MPB and achieve superior ferroelectric performance.
• Understanding grain size effects on phase evolution is critical for material design.
• These findings hold promise for next-generation semiconductor devices.