MoS2-functionalized conductive carbon heterostructure embedded with ferroelectric polymers for bipolar memristive applications

Abstract

Heterostructures of two-dimensional layered materials, integrating two or more building blocks with complementing counterparts, can regulate the confinement and transportation of charge carriers via vacancy-induced defect and interfacial states. Herein, reduced graphene oxide-molybdenum disulfide (rGO-MoS2) nanohybrid were fabricated and reinforced with various polymers [poly methyl methacrylate (PMMA), poly (vinylidene fluoride) (PVDF), and PMMA-PVDF (20:80) blend] to study the resistive memory properties in a metal–insulator-metal configuration. The scanning electron microscopy analysis presents a hierarchical 3D flower-like MoS2 intercalated with rGO nanosheets. Transmission electron microscopy image exhibits MoS2 nanoflakes well interspersed and grafted on layered rGO sheets, forming sandwich heterostructures. Raman analysis shows a higher I D/I G ratio for rGO-MoS2 than rGO, demonstrating numerous defect states in rGO. The x-ray diffraction analysis of the polymer blend containing rGO-MoS2 exhibits β-crystal phases with a polarity-dependent internal electric field (E-field). The J-V characteristics of pure MoS2-polymer films display a write-once-read-many behavior with a current I ON/I OFF ratio of ∼102–103, in contrast to pristine polymer films exhibiting repeatable electrical hysteresis. Instead, the rGO-MoS2-based devices display bipolar characteristics (I ON/I OFF ratio of ∼103–104) due to charge transfer interaction with the conductive carbon substrates. The ferroelectric polarization-induced E-field coupled with the external bias is responsible for the improved memristive performances. A plausible conduction mechanism is proposed to discuss the carrier transport through the devices.