Origin of Suppressed Ferroelectricity in k-Ga$_2$O$_3$: Interplay Between Polarization and Lattice Domain Walls

TL;DR

This study uncovers how the interaction between polarization and lattice domain walls in k-Ga2O3 explains suppressed ferroelectricity, using machine learning to reveal mechanisms affecting polarization reversal and domain wall behavior.

Contribution

It introduces a new mechanism involving polarization and lattice domain wall interplay in k-Ga2O3, explaining experimental observations through machine-learning simulations.

Findings

Reversal of polarization involves in-plane sliding and shear of Ga-O layers.

Strong anisotropy in domain wall propagation affects ferroelectric behavior.

Residual domain wall networks suppress polarization and coercive field.

Abstract

The large discrepancy between experimental and theoretical remanent polarization and coercive field limits the applications of wide-band-gap ferroelectric materials. Here, using a machine-learning potential trained on ab-initio molecular dynamics data, we identify a new mechanism of the interplay between polarization domain wall (PDW) and lattice domain wall (LDW) in ferroelectric k-phase gallium oxide (Ga2O3), which reconciles predictions with experimental observations. Our results reveal that the reversal of out-of-plane polarization is achieved through in-plane sliding and shear of the Ga-O sublayers. This pathway creates strong anisotropy in PDW propagation, and crucially leads to topologically forbidden PDW propagation across the 120 degree LDWs observed in synthesized samples. The resulting stable network of residual domain walls bypasses slow nucleation and suppresses the observable polarization and coercive field. These insights highlight the potential for tailoring the ferroelectric response in k-Ga2O3 from lattice-domain engineering.