Mind the Gap-Imaging Buried Interfaces in Twisted Oxide Moirés.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Twisted stacks of 2D materials enable tuning of electronic structure via moiré physics.
• Exploring similar moiré physics in twisted oxide membranes is motivated by this success.
• Oxides' 3D bonding nature presents challenges for atomic-level interface coupling compared to 2D materials.

Purpose of the Study:

• Investigate the impact of surface roughness on atomic-scale proximity in stacked oxide membranes.
• Evaluate imaging techniques for characterizing interfaces in oxide membrane stacks.
• Identify key challenges for realizing oxide twistronics.

Main Methods:

• Fabrication of stacked oxide membranes.
• Cross-sectional imaging for interface morphology analysis.
• Comparison of conventional through-focal imaging and electron ptychography for interface characterization.

Main Results:

• Surface roughness restricts atomic-scale proximity to isolated patches, even without contaminants.
• 2D materials' limited conformability to step-terrace topography further reduces atomic contact.
• Electron ptychography reliably resolves nanometer-scale structural variations at buried interfaces, unlike conventional imaging.

Conclusions:

• Interface topography is a critical factor limiting atomic coupling in stacked oxide membranes.
• Achieving atomic-level proximity in oxide membrane interfaces is significantly challenged by surface roughness.
• Interface characterization using advanced imaging is essential for advancing oxide twistronics research.