WTe2 thin films grown by beam-interrupted molecular beam epitaxy

The growth of WTe2 thin films by molecular beam epitaxy is demonstrated for the first time on a variety of 2D substrates including MoS2, Bi2Te3, and graphite. We demonstrate that beam interruption of the metal source enables the growth of crystalline WTe2 films in the distorted octahedral (1T') phase. As a result of the van der Waals nature of this material, a sharp interface between the WTe2 thin film and the substrate is shown with no evidence of misfit dislocations. In addition, the buckled structure expected for the semi-metallic 1T' phase is observed with transmission electron microscopy. Raman spectroscopy further confirms the growth of the 1T' phase and x-ray photoelectron spectroscopy shows the films to be stoichiometric and semi-metallic as expected.