Universal Strategy for Phase-Selective Synthesis of Monolayer TMDs via Colloidal Chemistry

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Synthesis

Background:

• Colloidal synthesis of monolayer transition metal dichalcogenides (TMDs) faces challenges in achieving uniform size, thickness, and crystalline phase.
• Existing phase engineering methods lack a unified chemical strategy for on-demand selection of both 2H and 1T' phases across diverse TMD systems.

Purpose of the Study:

• To develop a universal colloidal strategy for the selective synthesis of 2H and 1T' phases in multiple TMDs.
• To establish a generalized design principle for phase-selective colloidal synthesis of TMDs.

Main Methods:

• Utilized a colloidal synthesis approach.
• Tuned the metal-to-chalcogen precursor ratio ([M]:[X]) and ligand composition.
• Investigated phase selection mechanisms in W-based and Mo-based TMDs (MoS2, MoSe2, WS2, WSe2).

Main Results:

• Achieved selective synthesis of both 2H and 1T' phases across four representative TMDs (MoS2, MoSe2, WS2, WSe2).
• Demonstrated that W-based TMD phase selection is governed by precursor stoichiometry ([M]:[X] ratio).
• Showed that Mo-based TMDs require specific ligand environments (oleic acid in oleylamine) to yield the 1T' phase.

Conclusions:

• Presented the first general approach for phase-selective colloidal synthesis of four key TMD analogues using common precursors and ligands.
• Established a generalized design principle for phase-selective colloidal synthesis of TMDs.
• Provided a foundation for exploring phase-dependent quantum phenomena and functional properties of TMDs.