Pressure-induced metallization in MoSe₂ under different pressure conditions

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid State Chemistry

Background:

• Molybdenum diselenide (MoSe2) is a layered transition metal dichalcogenide with unique electronic and vibrational properties.
• Understanding its behavior under extreme pressure is crucial for potential applications in electronics and optoelectronics.

Purpose of the Study:

• To investigate the vibrational and electrical transport properties of MoSe2 under non-hydrostatic and hydrostatic pressures.
• To determine the conditions and reversibility of the semiconductor-to-metal electronic phase transition in MoSe2.

Main Methods:

• Diamond anvil cell (DAC) for high-pressure generation (up to ~40.2 GPa).
• Raman spectroscopy, electrical conductivity measurements, high-resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM).
• First-principles theoretical calculations.

Main Results:

• A semiconductor-to-metal electronic phase transition was observed and characterized by changes in Raman modes, electrical conductivity, and bandgap.
• Irreversible metallization occurred at ~26.1 GPa under non-hydrostatic conditions.
• Reversible metallization occurred at ~29.4 GPa under hydrostatic conditions, confirmed by post-pressure microscopy.

Conclusions:

• The reversibility of pressure-induced metallization in MoSe2 is highly dependent on the hydrostatic environment.
• The presence of pressure medium in the layers under hydrostatic conditions mitigates interlayer van der Waals coupling and shear stress, enabling reversible metallization.
• These findings highlight the importance of pressure conditions in tuning the electronic properties of layered materials like MoSe2.