Bias-Modified Schottky Barrier Height-Dependent Graphene/ReSe(2) van der Waals Heterostructures for Excellent Photodetector and NO(2) Gas Sensing Applications

Herein, we reported a unique photo device consisting of monolayer graphene and a few-layer rhenium diselenide (ReSe(2)) heterojunction. The prepared Gr/ReSe(2)-HS demonstrated an excellent mobility of 380 cm(2)/Vs, current on/off ratio ~ 10(4), photoresponsivity (R ~ 74 AW(−1) @ 82 mW cm(−2)), detectivity (D(*) ~ 1.25 × 10(11) Jones), external quantum efficiency (EQE ~ 173%) and rapid photoresponse (rise/fall time ~ 75/3 µs) significantly higher to an individual ReSe(2) device (mobility = 36 cm(2) V(−1)s(−1), Ion/Ioff ratio = 1.4 × 10(5)–1.8 × 10(5), R = 11.2 AW(−1), D* = 1.02 × 10(10), EQE ~ 26.1%, rise/fall time = 2.37/5.03 s). Additionally, gate-bias dependent Schottky barrier height (SBH) estimation for individual ReSe(2) (45 meV at V(bg) = 40 V) and Gr/ReSe(2)-HS (9.02 meV at V(bg) = 40 V) revealed a low value for the heterostructure, confirming dry transfer technique to be successful in fabricating an interfacial defects-free junction. In addition, HS is fully capable to demonstrate an excellent gas sensing response with rapid response/recovery time (39/126 s for NO(2) at 200 ppb) and is operational at room temperature (26.85 °C). The proposed Gr/ReSe(2)-HS is capable of demonstrating excellent electro-optical, as well as gas sensing, performance simultaneously and, therefore, can be used as a building block to fabricate next-generation photodetectors and gas sensors.