Large-Scale 1T'-Phase Tungsten Disulfide Atomic Layers Grown by Gas-Source Chemical Vapor Deposition.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Metastable two-dimensional (2D), 1T-phase transition-metal dichalcogenides (TMDs) are of significant research interest.
• 1T-phase TMDs offer potential in topological quantum computing, low-resistance contacts, energy storage, and catalysis.
• Synthesizing monolayer 1T-phase TMDs is challenging due to high energy differences and phase change barriers compared to the stable 2H-phase.

Purpose of the Study:

• To develop a reliable method for growing monolayer 1T-phase tungsten disulfide (WS2) atomic layers.
• To explore the use of alkali metal assistance in chemical vapor deposition (CVD) for phase control.

Main Methods:

• Chemical vapor deposition (CVD) using gaseous precursors (H2S and WF6).
• Alkali metal (Na+) assistance to facilitate the growth of the 1T-phase.
• Atomic-resolution scanning transmission electron microscopy (STEM) for structural characterization.

Main Results:

• High-quality, submillimeter-sized crystals of 1T-phase WS2 were successfully synthesized.
• Atomic structure confirmed the characteristic zigzag chain of W atoms specific to the 1T' phase.
• The synthesized 1T-phase WS2 exhibited superconductivity with a transition temperature of 2.8–3.4 K and significant upper critical field anisotropy.

Conclusions:

• Alkali metal-assisted gas-source CVD is an effective bottom-up approach for large-scale, phase-engineered 1D-phase TMD atomic layers.
• This method facilitates the controlled synthesis of metastable phases for advanced material applications.
• The findings pave the way for utilizing 1T-phase TMDs in next-generation electronic and quantum devices.