Diverse modes regulated photoresponse and high-resolution imaging based on van der Waals semimetal PtTe2/semiconductor MoTe2 junctions

Exploration towards emerging 2D Weyl semimetals (WSMs) based van der Waals (vdWs) structures has become an efficient path for fabricating low-consumption multifunctional devices. 2D WSMs represented by 1T′-WTe2 and 1T′-MoTe2 have been extensively studied in terms of polarized photodetection, edge photocurrent, etc., but they still face great difficulties in large-scale applications of photoelectric detection owing to the high dark current and poor responsivity. Herein, a multilayered PtTe2/2H-MoTe2-based 2D/2D Schottky phototransistor by mechanical exfoliation method and dry transfer process is demonstrated. Owing to the built-in electric field at the heterojunction and low resistivity of PtTe2, a rectification ratio of up to 2 × 103 is achieved. Moreover, the device can act as a photodiode at zero/negative bias and a phototransistor at forward bias. In particular, it possesses a high photovoltaic responsivity of 1.6 A W−1, a specific detectivity of 6.1 × 1012 Jones and a response time of fewer than 22 μs under the laser of 635 nm. Finally, the single-pixel imaging measurements based on the photodiode confirmed outstanding detection capability in our photodiode at zero/negative bias conditions, which shows great potential in photodetection applications. To sum up, the above results reveal that topological semimetals such as PtTe2 can be incorporated into vdWs architectures for ultrafast photoresponse and high-contrast imaging systems.