Telluride-Based Atomically Thin Layers of Ternary Two-Dimensional Transition Metal Dichalcogenide Alloys

Alloying in two-dimensional (2D) transition metal dichalcogenides (TMDCs) has allowed band gap engineering and phase transformation, as well as modulation of electronic properties. However, most of the efforts have been focused on alloying between transition metal cations. Among those that emphasize alloying between chalcogenide anions, the sulfide- selenide combinations are popular with a few reports on selenide-telluride combinations. In this work, we show a facile chemical vapor deposition method to obtain stable alloying between selenide and telluride anions in monolayer Mo-Se2(1-x)Te2x alloy. These alloys retain the monolayer 2H symmetry and show good photoluminescence and band gap tunability in the near-infrared region. The nature and percentage of alloying is further confirmed and quantified via AFM, XPS, and HAADF-STEM imaging and polarized Raman spectroscopy. The stability of the two chalcogens in the monolayer 2H lattice is also consistent with thermodynamic phase mixing via DFT simulations. The work demonstrates a straightforward method of synthesizing telluride-based 2D TMDC alloys for further studies and emerging applications.