Ultrafast and stable phase transition realized in MoTe 2 -based memristive devices.

Phase engineering of two-dimensional transition metal dichalcogenides has received increasing attention in recent years due to its atomically thin nature and polymorphism. Here, we first realize an electric-field-induced controllable phase transition between semiconducting 2H and metallic 1T' phases in MoTe 2 memristive devices. The device performs stable bipolar resistive switching with a cycling endurance of over 10 5 , an excellent retention characteristic of over 10 5 s at an elevated temperature of 85 °C and an ultrafast switching of ∼5 ns for SET and ∼10 ns for RESET. More importantly, the device works in different atmospheres including air, vacuum and oxygen, and even works with no degradation after being placed in air for one year, indicating excellent surrounding and time stability. In situ Raman analysis reveals that the stable resistive switching originates from a controllable phase transition between 2H and 1T' phases. Density functional theory calculations reveal that the Te vacancy facilitates the phase transition in MoTe 2 through decreasing the barrier between 2H and 1T' phases, and serving as nucleation sites due to the elimination of repulsive forces. This electric-field-induced controllable phase transition in MoTe 2 devices offers new opportunities for developing reliable and ultrafast phase transition devices based on atomically thin membranes.