Tellurization Velocity-Dependent Metallic–Semiconducting–Metallic Phase Evolution in Chemical Vapor Deposition Growth of Large-Area, Few-Layer MoTe2

Phase engineering of two-dimensional (2D) transition metal dichalcogenides (TMDs) such as MoTe 2 offers tremendous opportunities in various device applications. However, most of the existing methods so far only address the small-area local phase change or the growth of certain kinds of phases of MoTe 2 film by laser irradiation, mechanical strain, or procursor type. Obtaining facile, tunable, reversible, and continuous-phase transition and evolution between different phases in direct growth of large-area, few-layer MoTe 2 still remains challenging. Here, we develop a facile method to achieve phase control and transition and report a highly tunable, tellurization velocity-dependent metallic–semiconducting–metallic phase evolution in chemical vapor deposition (CVD) growth of large-area, few-layer MoTe 2 . We found four different phase stages, including two different types of coexistence phases of both 2H and 1 T′ phases, 100% 2H phase, and 100% 1T′ phase, would emerge, relying on the adopted tellurization velocity. Importantly, the tellurization velocity should be extremely controlled to obtain 100% 2H phase MoTe 2, while 100% 1T′ phase requires a fast tellurization velocity. We further found that such metallic–semiconducting–metallic phase evolution took place with a homogeneous spatial distribution and differs from previous reports in which obvious phase separations are usually found during the phase transition. The resulting MoTe 2 shows high quality with room-temperature mobility comparable with mechanically exfoliated materials. The results might impact large-scale phase engineering of TMDs and other 2D materials for Weyl semimetal topological physics and potential 2D semiconductor device applications.