Alternating atomic-dipole layers and switching dynamics in Al_1-xSc_xN ferroelectrics

Area of Science:

• Materials Science
• Solid-State Physics
• Nanotechnology

Background:

• Wurtzite Aluminum Scandium Nitride (AlScN) ferroelectrics offer high polarization and thermal stability.
• Understanding the atomic-scale mechanisms behind reduced coercive fields in AlScN is crucial for advanced electronic applications.

Purpose of the Study:

• To elucidate the atomic-scale mechanism of cation substitution in AlScN ferroelectrics.
• To investigate how chemical ordering influences polarization switching energy barriers and coercive fields.

Main Methods:

• Spherical aberration-corrected transmission electron microscopy (TEM) was employed.
• In situ imaging techniques were utilized to observe polarization switching dynamics at the atomic level.

Main Results:

• Periodic modulation of cation-anion spacing was observed, forming alternating atomic dipole layers.
• Energetically favorable chemical ordering of Al and Sc atoms between layers was identified.
• Atomic-scale, stepwise polarization switching with intermediate states and local spacing fluctuations was directly captured.
• Compositional inhomogeneity in dipole layers was found to reduce the switching energy barrier.

Conclusions:

• Atomic-scale dipole structures in AlScN are directly linked to polarization switching kinetics.
• Chemical ordering and compositional inhomogeneity are key factors in reducing the coercive field.
• These findings facilitate the rational design of high-performance wurtzite ferroelectrics.