Atomistic Structure of Transient Switching States in Ferroelectric AlScN

Area of Science:

• Materials Science
• Solid-State Physics
• Nanotechnology

Background:

• Ferroelectric materials exhibit spontaneous electric polarization that can be reversed by an external electric field.
• Wurtzite ferroelectric aluminum scandium nitride (AlScN) is a promising material for advanced electronic applications.
• Understanding the microscopic switching mechanisms is crucial for optimizing ferroelectric device performance.

Purpose of the Study:

• To elucidate the atomic-scale mechanism of polarization switching in wurtzite ferroelectric AlScN.
• To investigate the role of domain wall morphology in ferroelectric switching dynamics.
• To correlate local domain wall structure with macroscopic ferroelectric behavior.

Main Methods:

• Advanced thin-film fabrication and characterization.
• Ferroelectric switching dynamics measurements.
• High-resolution scanning transmission electron microscopy (STEM).
• Large-scale molecular dynamics simulations using a deep neural network-based interatomic potential.

Main Results:

• Evidence suggests that observed transitional regions in STEM images are projection artifacts of zigzag 180° domain walls, not a nonpolar phase.
• Atomistic simulations reveal switching occurs via collective, column-by-column atomic displacements, forming zigzag domain walls.
• Increasing scandium content reduces domain wall energy and nucleation barrier, lowering the switching field.

Conclusions:

• Polarization switching in AlScN proceeds through collective atomic displacements, forming characteristic zigzag domain walls.
• The intrinsic 3D zigzag morphology of domain walls, not a transient nonpolar phase, explains observed phenomena.
• Findings link local domain wall structure to switching dynamics and macroscopic ferroelectric properties in AlScN.