Mechanically liberating polarization bubbles in van der Waals ferroelectrics

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Ferroelectric topological textures are crucial for advanced non-volatile and ultrahigh-density information storage.
• Current methods for creating these textures often rely on complex heterostructures with engineered layers to manage competing energies.

Purpose of the Study:

• To report the creation of high-density polarization bubbles in van der Waals ferroelectric crystals without requiring engineered heterostructures.
• To investigate the mechanisms behind the formation and manipulation of these bubble domains.

Main Methods:

• Piezoresponse force microscopy (PFM) was used to observe the formation and distribution of bubble domains.
• Density functional theory (DFT) and phase-field modelling were employed to understand the underlying physics.
• External stimuli, such as mechanical force, were used to tailor the polar phase ratio.

Main Results:

• High-density polarization bubbles were successfully formed in van der Waals ferroelectric crystals (CuInP2S6) without heterostructures.
• The formation of bubble domains was linked to the inherent coexistence of polar phases within the material.
• Labyrinth domains were controllably transformed into isolated bubbles by manipulating the polar phase ratio via mechanical force, involving polar phase competition and flexoelectricity.

Conclusions:

• The study demonstrates a novel method for creating controlled topological structures in ferroelectric materials.
• The findings highlight the potential of bubble domains in van der Waals ferroelectrics for future memory device applications.
• This work advances the understanding of polar phase competition and flexoelectricity in the formation of ferroelectric textures.