Engineering Point-Defect States in Monolayer WSe₂

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Defect engineering is crucial for tuning properties of 2D semiconductors.
• Tungsten diselenide (WSe2) is a promising 2D semiconductor material.

Purpose of the Study:

• To investigate atomic engineering of W vacancies in monolayer WSe2 using potassium (K) decoration.
• To explore the impact of K decoration on electronic states and magnetic properties.

Main Methods:

• Experimental: Scanning tunneling spectroscopy (STS) on K-decorated WSe2.
• Theoretical: First-principle calculations to model electronic and magnetic properties.

Main Results:

• K decoration revealed previously hidden midgap states with well-resolved multiplets in STS.
• Energy levels of these states matched theoretical calculations.
• Calculations predicted local magnetic moments arising from unpaired electrons donated by K atoms.
• Experimental Fermi level pinning by the graphite substrate resulted in an 'off' magnetic state.

Conclusions:

• Atomic decoration of W vacancies in WSe2 effectively modifies electronic properties.
• The study demonstrates a potential pathway for creating gate-programmable magnetic moments in 2D materials.
• Close agreement between theory and experiment validates the proposed mechanism.