Robust temperature–strain coupling in phase and shape evolution of MoTe2 nanosheets

Molybdenum ditelluride (MoTe2) has a stable semiconducting hexagonal (2H) phase and a metastable metallic distorted octahedral (1T′) phase at the same time, which attracts much attention due to its attractive properties. However, the mechanism of phase and shape evolution in the preparation of MoTe2 is still unclear, which limits the controllable preparation and the wider device application of MoTe2. Here, we prepare few-layer MoTe2 with controllable phase and shape by using MoO3 and Te powders as precursors. With this method, triangle and hexagon 2H MoTe2 can be prepared, and long-strip and irregular 1T′ MoTe2 can be obtained. The phase and shape of as-prepared MoTe2 are determined by the coupling effect in the growth temperature and the lattice strain between 2H and 1T′ MoTe2. Low growth temperature combined with low Te concentration could induce small growth strain potential, leading to the growth of triangle and hexagon 2H MoTe2. While high growth temperature combined with high Te concentration could induce large strain potential, which is conducive to the preparation of long-strip and irregular 1T′ MoTe2. This study deeply investigates the evolution mechanism of phase and shape in MoTe2 growth, which has important guiding significance for the controllable preparation of phase and shape of other two-dimensional materials.