Vortex-Oriented Ferroelectric Domains in SnTe/PbTe Monolayer Lateral Heterostructures

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Heterostructures with complementary properties exhibit novel physics.
• Ferroelectric materials are key components in advanced electronic devices.
• Vertical heterostructures are common, but lateral ones offer new possibilities.

Purpose of the Study:

• To report the first in situ molecular beam epitaxial growth of lateral ferroelectric heterostructures.
• To characterize the electronic properties and domain structures of SnTe/PbTe lateral heterostructures.
• To investigate the mechanism behind ferroelectric domain formation and polarization orientation.

Main Methods:

• In situ molecular beam epitaxy (MBE) for atomically sharp growth.
• Scanning tunneling microscopy (STM) for atomic-scale characterization.
• First-principles calculations to support experimental findings.

Main Results:

• Successful growth of atomically sharp lateral heterostructures between SnTe and PbTe monolayers.
• Observation of bias voltage-dependent apparent heights related to type-II band alignment.
• Discovery of clockwise/counterclockwise vortex-oriented ferroelectric domains in SnTe surrounding a PbTe core.
• Identification of a preferred polarization direction (SnTe to PbTe) when polarization is not interface-parallel.
• Elucidation of vortex formation mechanism via polarization, space charge, and strain interactions.

Conclusions:

• Demonstrated the feasibility of creating 2D lateral ferroelectric heterostructures.
• Revealed unique ferroelectric domain configurations and polarization phenomena.
• Provided a fundamental understanding of the underlying physical mechanisms.
• Advanced the potential applications of 2D group-IV monochalcogenides in in-plane ferroelectric devices.