Performance improvement of organic resistive memories by exploiting synergistic layered nanohybrid dispersed polymer composites

Abstract

Functionalized layered nanohybrid materials have been thoroughly explored in numerous practical applications including photocatalysis, supercapacitors, and sensors, and have inherent potential to excel in the field of organic resistive random access memory devices as well. Herein, we report an efficient, facile, and cost-effective in situ synthesis route to prepare a layered nanohybrid by grafting cadmium sulfide (CdS) nanorods with exfoliated graphene oxide (GOs) sheets via the one-step hydrothermal functionalization technique. Such a nanohybrid material displays advantageous characteristics possessed by them due to the formation of organic–inorganic heterojunctions at their interface. Sandwiched devices, with a configuration of ITO/reduced graphene oxide–CdS/poly-methyl methacrylate (PMMA)/Al, are fabricated by dispersing different wt. % of the layered nanohybrid in a poly-methyl methacrylate (PMMA) matrix. Detailed current density vs voltage (J–V) studies exhibit excellent bipolar resistive switching characteristics reaching a very low set voltage of ∼−0.48V, high current ION/IOFF ratios of ∼106, and ultralow set/reset power densities of ∼10−8/10−6W/cm2 for devices containing 0.4 wt. % nanohybrid nanofillers. Partial reduction of GOs and the formation of heterojunctions during the synthesis process undoubtedly boost the resistive memory performances resulting from the synergistic effect in layered nanohybrid materials. The fabricated devices have been subjected to various analyses in order to test their stability, repeatability, and reliability, all of which have been found to display encouraging results.

Semiconductor-Grafted Polymer-Embedded Reduced Graphene-Oxide Nanohybrid for Power-Efficient Nonvolatile Resistive Memory Applications

“…This is due to the excellent weather resistance of PMMA, which protects the nanohybrid materials from the environmental impurities and maintains the device performance under repeated bias . In a previous work, no degradation in device performance was observed even after a duration of 4 months . The I ON / I OFF ratio for all the nanohybrid devices ranges from 10 3 to 10 4 irrespective of the type or amount of nanofillers.…”

“…These peaks correspond to energies of ∼2.39 eV (pure ZnS) and 2.37 eV (rGO-ZnS) and can be attributed to the presence of zinc vacancies in both pure and nanohybrid materials . However, as compared to pure ZnS, the rGO-ZnS nanohybrid exhibits quenching of peak intensity, which suggests an efficient charge-transfer interaction between the rGO sheets and grafted ZnS . Furthermore, a small peak at ∼328 nm appears in the spectrum of pure ZnS, which can be attributed to the band edge emission in the metal sulfide.…”

“…Also, the removal of oxygen functionalities from the GO structure reduces the separation between the GO layers, which results in an overall decrease in the band-gap energy. This causes red-shifting of the peak position upon conversion from GO (∼237 nm) to rGO (∼277 nm) . Apart from the intense UV peak of rGO, the nanohybrids also display additional peaks, which are characteristic of the metal-sulfide components.…”

“…A comparison between the recently reported graphene/GO/rGO-based RRAM with the present work is shown in Table T5. − ,,,,,,− Finally, to get insights into the probable conduction mechanism, J–V curves of all nanohybrid devices were plotted in a log–log plot (Figure and Figures S14–S16) and linearly fitted to satisfy the equation where J is the current density, V is the applied external bias, and α (exponent) is the slope of the linear fitting. Before switching (0 → − V < V SET ), all the devices initially display a slope of ∼2 at lower voltage values (green line), which corresponds to the space-charge-limited conduction (SCLC) mechanism . The space charges are created due to the resistance from the insulating PMMA layer to the electrons coming from the Al electrode.…”

Reduced Graphene Oxide Inserted into PEDOT:PSS Layer to Enhance the Electrical Behaviour of Light-Emitting Diodes

“…On the other hand, Cadmium sulphide (CdS) nanocrystals (NCs) have been studied in recent years [ 15 ] due to their ability to modify the optical and electrical properties of the organic devices [ 16 ]. Cadmium sulphide nanoparticles have been used to improve or modify the properties of different devices, such as organic solar cells [ 17 ], light-emitting devices [ 18 ], hybrid memory devices as a compound of polymer composites and CdS nanocrystals [ 19 , 20 ], and memory devices with other nanoparticles, such as graphene oxide nanocrystals [ 21 ]. CdS is a semiconductor with a direct bandgap energy of 2.4 eV.…”