Controllable 2H-to-1T′ phase transition in few-layer MoTe2

Abstract

Most two-dimensional (2D) transition metal dichalcogenides (TMDs) exhibit more than one structural phase, leading to a number of remarkable physics and potential device applications beyond graphene. Here, we demonstrated a feasible route to trigger 2H-to-1T′ phase transition in few-layer molybdenum ditelluride (MoTe₂) by laser irradiation. The effects of laser power and irradiation duration were systematically studied in this study, revealing the accumulated heating effect as the main driving force for such a phase transition. By carefully adjusting laser power and irradiation time, we could control the structural phases of MoTe₂ as 2H, 2H + 1T′, and 1T′. After thermal annealing at a rather low temperature, the laser-irradiated MoTe₂ showed a completely suppressed 2H component and a more stabilized 1T′ phase, demonstrating that the microscopic origin of the irreversible 2H-to-1T′ phase transition is the formation of Te vacancies in MoTe₂ due to laser local instantaneous heating. Our findings together with the unique properties of MoTe₂ pave the way for high-performance nanoelectronics and optoelectronics based on 2D TMDs and their heterostructures.