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.