Predicting dislocations and grain boundaries in two-dimensional metal-disulfides from the first principles

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) materials like graphene and hexagonal boron nitride (h-BN) are typically planar.
• Understanding defects is crucial for tailoring material properties.
• Transition metal disulfides (MS2) are promising 2D materials with unique electronic characteristics.

Purpose of the Study:

• To investigate the structure and properties of dislocations and grain boundaries (GB) in single-layer MS2 (M = Mo, W).
• To explore the 3D nature of dislocations in these materials.
• To analyze the electronic behavior of GB and their potential applications.

Main Methods:

• First-principles calculations based on dislocation theory.
• Analysis of dislocation core structures, including homoelemental bonds, vacancies, interstitials, and atom substitutions.
• Investigation of grain boundary structures influenced by chemical and mechanical energies.
• Characterization of electronic properties of grain boundaries.

Main Results:

• Edge dislocations in MS2 extend into the third dimension, forming concave dreidel-shaped polyhedra.
• Dislocation cores exhibit diverse structures due to reactions with point defects and substitutions.
• Grain boundary structures are governed by local-chemical and far-field mechanical energies.
• Grain boundaries typically exhibit localized deep-level states acting as carrier sinks.
• A 60°-tilt grain boundary demonstrates metallic electronic behavior.

Conclusions:

• The 3D nature of dislocations in MS2 leads to complex core structures.
• Grain boundaries in MS2 possess versatile structures and tunable electronic properties.
• Engineered grain boundaries in MS2 hold significant potential for novel electronic and opto-electronic applications.