Dimensionally controlled MoS ₂ nanodiscs for optimal localized surface plasmonic resonance in nanohybrid photodetectors

Abstract Nanohybrids based on van der Waals (vdW) heterostructures of graphene (Gr) decorated with MoS 2 nanodiscs (MoS 2 -NDs) combine the advantages of high carrier mobility of graphene for high photoconductive gain and localized surface plasmonic resonance (LSPR) on MoS 2 -NDs for enhanced light absorption. Considering MoS 2 -NDs are obtained using dip-coating of (NH 4 ) 2 MoS 4 precursor followed with annealing in sulfur vapor at 450 °C, the annealing plays a critical role in controlling the MoS 2 -NDs properties. This work investigated the effect of the annealing time on the MoS 2 -NDs dimension and found the MoS 2 -ND’s thickness was increased monotonically from bilayer to multilayer and diameter reduced from ∼900 nm to 600 nm with annealing time increased from 4 to 25 min. A similar increasing photoresponsivity observed on MoS 2 -NDs/Gr with annealing time indicates the conversion of the (NH 4 ) 2 MoS 4 precursor to crystalline MoS 2 initiated at the precursor/graphene interface and continued vertically. At the annealing time of ∼20 min, the MoS 2 -NDs reached the optimal diameter (∼600 nm) and thickness (near or slightly above 4.2 nm) for LSPR while graphene remained unblemished, yielding the highest photoresponsivity up to 37 A W −1 (at 550 nm wavelength and 12 μW cm −2 light intensity) on the MoS 2 -NDs/Gr nanohybrids photodetectors which leads to enhanced detectivity D * by a factor of 320 over the quantum dots/graphene nanohybrid counterpart of comparable thickness and illustrates the benefits of LSPR induced in MoS 2 -NDs for enhanced light absorption.