Capturing 3D atomic defects and phonon localization at the 2D heterostructure interface

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Heterostructure interfaces dictate crucial electronic, magnetic, optical, catalytic, and topological quantum properties.
• Direct experimental determination of 3D atomic structures and defects at these interfaces has been a significant challenge.

Purpose of the Study:

• To determine the 3D local atomic positions and defects at a Molybdenum disulfide-Tungsten diselenide (MoS2-WSe2) heterojunction interface with picometer precision.
• To correlate observed 3D atomic defects with localized vibrational properties at the epitaxial interface.

Main Methods:

• Atomic electron tomography was employed to visualize and determine the 3D atomic structure at the MoS2-WSe2 heterojunction.
• First-principles calculations were performed using experimental 3D atomic coordinates as input.
• Spatially resolved electron energy-loss spectroscopy was used for corroboration.

Main Results:

• The study achieved picometer precision in determining 3D atomic positions at the heterojunction interface.
• Point defects, bond distortion, atomic-scale ripples, and the full 3D strain tensor were measured.
• New phonon modes localized at the interface were revealed and experimentally corroborated.

Conclusions:

• This work establishes a method for correlating 3D atomic structure and defects with localized properties at heterostructure interfaces.
• The findings are expected to advance the understanding of structure-property relationships in various heterostructure systems.
• The study opens avenues for single-atom level analysis of interface phenomena.