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

Abstract

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.