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 MoTe2 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 MoTe2 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 MoTe2 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 MoTe2. 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 MoTe2, 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 MoTe2 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.