Photoinduced Vacancy Ordering and Phase Transition in MoTe₂

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid State Chemistry

Background:

• Transition metal dichalcogenides (TMDs) exhibit diverse structural phases.
• Phase transitions in TMDs are crucial for tuning their electronic and optical properties.
• Understanding photoinduced phase transitions is key for optoelectronic applications.

Purpose of the Study:

• To elucidate the mechanism of the photoinduced 2H-to-1T' phase transition in Molybdenum Ditelluride (MoTe2).
• To investigate the role of non-equilibrium dynamics and photogenerated carriers in this transition.
• To contrast the proposed mechanism with existing models for phase transitions in TMDs.

Main Methods:

• In-situ characterization of photoinduced structural changes.
• Analysis of defect dynamics (Te vacancies) under photoexcitation.
• Theoretical modeling of non-equilibrium processes in MoTe2.

Main Results:

• The 2H-to-1T' phase transition is initiated by local ordering of Te vacancies.
• Photogenerated excited carriers enhance vacancy diffusion and ordering speed.
• The transition proceeds via a seed-and-growth mechanism driven by photoexcitations.
• This mechanism differs from the collective layer sliding model.

Conclusions:

• Non-equilibrium dynamics, particularly photogenerated carriers, are central to the photoinduced 2H-to-1T' phase transition in MoTe2.
• The findings challenge existing thermodynamic models and propose a new mechanism.
• This work provides insights for controlling phase transitions in TMDs using light.