A Universal Platform for Selective Phase Growth and Precise-Layer Control in MoTe2

Minor structural changes in transition metal dichalcogenides can have dramatic effects on their electronic properties. This makes the quest for key parameters that can enable a selective choice between the competing metallic and semiconducting phases in the 2D MoTe₂ system compelling. Herein, we report the optimal conditions at which the choice of the initial seed layer dictates the type of crystal structure of atomically-thin MoTe₂ films grown by chemical vapour deposition (CVD). When Mo metal is used as a seed layer, phase-pure semiconducting 2H-MoTe₂ is the only product. Conversely, MoO₃ leads to the preferential growth of phase-pure metallic 1Tꞌ-MoTe₂. The control over phase growth allows for simultaneous deposition of both 2H-MoTe₂ and 1Tꞌ-MoTe₂ phases on a single substrate during one CVD reaction. Furthermore, Rhodamine 6G dye can be detected using few-layered 1Tꞌ-MoTe₂ films down to 5 nM concentration which is several orders of magnitude higher than the value observed for bulk 1Tꞌ-MoTe₂.