In situ edge engineering in two-dimensional transition metal dichalcogenides

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Controlling the edge structure and chemistry of two-dimensional (2D) materials is crucial for tuning their properties.
• Existing methods often lack atomic precision in manipulating these edges for specific functionalities.

Purpose of the Study:

• To directly image and understand the atomic evolution of pore edges in Mo$_{1-x}$W$_{x}$Se$_{2}$ monolayers.
• To demonstrate the structural transformation of these edges into predicted metastable configurations.
• To establish a pathway for controlled atomic-scale manipulation of 2D material edges.

Main Methods:

• Atomic-resolution in situ scanning transmission electron microscopy (STEM) for direct imaging of edge evolution.
• Density functional theory (DFT) calculations to model atomic structures and energetics.
• Ab initio molecular dynamics (AIMD) simulations to understand thermally induced structural changes.

Main Results:

• Direct observation of edge structure transformation in Mo$_{1-x}$W$_{x}$Se$_{2}$ monolayers under thermal and chemical stimuli.
• Identification of four stable edge configurations driven by changing chemical potential during annealing.
• Validation of theoretically predicted metastable atomic configurations through in situ experiments.

Conclusions:

• The study provides a combined experimental and computational approach for understanding and controlling 2D material edge structures.
• Demonstrated pathway for predictive synthesis of specific edge configurations in Mo$_{1-x}$W$_{x}$Se$_{2}$.
• Enables the directed design of 2D materials with tailored magnetic, optical, electrical, and catalytic properties.