Domain-Wall-Mediated Polarization Switching in Ferroelectric AlScN: Strain Relief and Field-Dependent Dynamics

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid State Chemistry

Background:

• Scandium-doped aluminum nitride (AlScN) possesses strong ferroelectric properties and thermal stability.
• Its practical application is hindered by a very high coercive field (E_{c}) required for polarization switching.

Purpose of the Study:

• To investigate the atomistic mechanisms governing polarization switching in AlScN.
• To understand how Sc concentration and electric fields influence switching dynamics.
• To identify strategies for reducing the coercive field in AlScN.

Main Methods:

• Density functional theory (DFT) calculations.
• Machine-learning molecular dynamics (MLMD) simulations.
• Analysis of polarization switching under varying Sc concentrations and electric fields.

Main Results:

• Lattice strain significantly impedes collective polarization switching.
• Preexisting domain walls mitigate strain, enabling distinct, field-dependent switching behaviors.
• Low electric fields induce gradual domain-wall propagation (Kolmogorov-Avrami-Ishibashi model).
• High electric fields promote nucleation, leading to rapid, homogeneous reversal (nonlinear nucleation and growth model).

Conclusions:

• Domain wall dynamics critically influence polarization switching mechanisms in AlScN.
• Switching behavior transitions from domain-wall propagation to nucleation-driven reversal with increasing electric field.
• Domain engineering presents a promising approach to tailor coercive fields in AlScN and similar ferroelectric materials.