Stacking-mode confined growth of 2H-MoTe2/MoS2 bilayer heterostructures for UV-vis-IR photodetectors

The atomic thin, vertically-stacked 2H-MoTe2/MoS2 heterostructures are successfully synthesized using the single step chemical vapor deposition (CVD) method and a magnet-assisted secondary precursor delivery tool. The second material (MoTe2) was grown in a well-controlled, unique and epitaxial 2H-stacking mode atop the first material (MoS2), starting from the edges. This led to the construction of a vertical p-n junction with a broadband photoresponse from the ultraviolet (UV, 200 nm) to the near-infrared (IR, 1100 nm) regions. The high crystallinity of MoTe2/MoS2 heterostructures with a modulation of sulfur and tellurium distribution is corroborated by multiple characterization methods, including Raman spectroscopy, photoluminescence (PL) spectroscopy and high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). Furthermore, the photoelectrical measurements exhibit a tremendous photoresponsivity with an external quantum efficiency (EQE) as high as 4.71 A/W and 532% at 1100 nm, while as 4.67 A/W and 1935% at 300 nm, one to two orders of magnitude higher than other exfoliated MoTe2 heterostructure devices have been reported so far. This synthetic method is a controllable stacking mode confined synthesis approach for 2D heterostructures, and paves the way for the fabrication of high-performance functional telluride-based broadband photodetectors.