Thermodynamics and Kinetics Synergetic Phase-Engineering of Chemical Vapor Deposition Grown Single Crystal MoTe2 Nanosheets

Molybdenum ditelluride (MoTe2), which is stabilized in both semiconducting hexagonal (2H) and metallic distorted octahedral (1T') phases, has attracted increasing attention owing to their attractive properties for promising wide applications. Exploring the full potential of this emerging material requires a reliable synthesis approach to precisely control its phase structure. Here, we report on the growth of high crystallinity MoTe2 nanosheets with a controlled phase via the tellurization of chemical vapor deposition-grown MoO2 nanosheets. The single crystal MoO2 nanosheets with rhombus shape were converted into MoTe2 single crystal nanosheets with morphology maintained well through the tellurization process. The phase structure of as-grown MoTe2 is determined by the synergetic effect of thermodynamics and kinetics in the crystal growth process, which is based on the difference in the thermodynamic stability and the lattice strain between 2H and 1T' phases. Low growth temperature combined with a slow tellurization rate (low Te content) is favorable for growing 2H-MoTe2, while high growth temperature together with a fast tellurization rate (high Te content) is beneficial to grow 1T'-MoTe2. A phase diagram based on the thermodynamics and kinetics of MoTe2 growth was drawn, which provides significant guidance for future synthesizing of two-dimensional materials with a controlled phase structure.