Atomically sharp interlayer stacking shifts at anti-phase grain boundaries in overlapping MoS₂ secondary layers.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Surface Science

Background:

• Molybdenum disulfide (MoS2) is a key 2D material with potential applications in electronics and optoelectronics.
• Grain boundaries (GBs) in monolayer MoS2 significantly influence its electronic and mechanical properties.
• Understanding the behavior of GBs in multilayer MoS2 structures is crucial for device fabrication.

Purpose of the Study:

• To investigate the atomic structure of overlapping antiphase grain boundaries (GBs) in MoS2 monolayer-bilayers.
• To analyze the impact of secondary bilayer domain growth on underlying monolayer GBs.
• To elucidate the relationship between GB meandering and defect structures.

Main Methods:

• Aberration-corrected annular dark-field scanning transmission electron microscopy (AC-ADF-STEM) for atomic-level imaging.
• Density Functional Theory (DFT) calculations to model interlayer stacking and interactions.
• Analysis of antiphase GB propagation and defect structures (4- and 8-member rings).

Main Results:

• Overlapping bilayer MoS2 domains create atomically sharp interfaces between 2H and 3R stacking configurations.
• Antiphase GBs exhibit micro-nanoscale meandering with directional dependence on defect density.
• Sharp turning angles (90°-100°) in GBs are mediated by specific 8-member ring defects.
• Van der Waals interactions at overlapping regions induce atomic structure modifications at GB sites.

Conclusions:

• Secondary bilayer MoS2 domains significantly alter the atomic structure of underlying antiphase GBs.
• The interplay between GBs, stacking faults, and defects dictates the material's atomic arrangement.
• This atomic-level understanding is vital for controlling MoS2 heterostructure properties.