Spatially Controlled Phase Transition in MoTe 2 Driven by Focused Ion Beam Irradiations.

Phase transitions play an important role in tuning the physical properties of two-dimensional (2D) materials as well as developing their high-performance device applications. Here, we reported the observation of a phase transition in few-layered MoTe 2 flakes by the irradiation of gallium (Ga + ) ions using a focused ion beam (FIB) system. The semiconducting 2H phase of MoTe 2 can be controllably converted to the metallic 1T'-like phase via Te defect engineering during irradiations. By taking advantage of the nanometer-sized Ga + ion probe proved by FIB, in-plane 1T'-2H homojunctions of MoTe 2 at submicrometer scale can be fabricated. Furthermore, we demonstrate the improvement of device performance (on-state current over 2 orders of magnitude higher) in MoTe 2 transistors using the patterned 1T'-like phase regions as contact electrodes. Our study provides a new strategy to drive the phase transitions in MoTe 2 , tune their properties, and develop high-performance devices, which also extends the applications of FIB technology in 2D materials and their devices.