Selective phase growth and precise-layer control in MoTe 2

Minor structural changes in transition metal dichalcogenides can have dramatic effects on their electronic properties. This makes the quest for key parameters that enable a selective choice between the competing metallic and semiconducting phases in the 2D MoTe 2 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 MoTe 2 films grown by chemical vapour deposition (CVD). When Mo metal is used as a seed layer, semiconducting 2H-MoTe 2 is the only product. Conversely, MoO 3 leads to the preferential growth of metallic 1T′-MoTe 2 . The control over phase growth allows for simultaneous deposition of both 2H-MoTe 2 and 1T′-MoTe 2 phases on a single substrate during one CVD reaction. Furthermore, Rhodamine 6G dye can be detected using few-layered 1T′-MoTe 2 films down to 5 nM concentration, demonstrating surface enhanced Raman spectroscopy (SERS) with sensitivity several orders of magnitude higher than for bulk 1T′-MoTe 2 .