Control over electrically bistable properties of layer-by-layer-assembled polymer/organometal multilayers

We demonstrate that nonvolatile memory devices can be prepared using electrostatic layer-by-layer (LbL)-assembled nanocomposite films, and additionally that their performance can be easily enhanced by an additional insertion of charge trap elements within the films. For this study, cationic poly(allylamine hydrochloride) (PAH) and anionic titania precursors (titanium(IV) bis(ammonium lactato) dihydroxide, TALH) were used for the preparation of electrostatic LbL-assembled nanocomposite films on a Pt-coated silicon wafer. The formed multilayer nanocomposites were converted into the transition metal oxide films (that is, TiO_x nanocomposites) after thermal annealing at 450 °C, and then, the top electrodes were deposited onto the TiO_x films to complete the device fabrication. When external bias was applied to the devices, these TiO_x -based devices displayed bipolar resistive switching property with an ON/OFF current ratio of ∼10. However, the insertion of anionic graphene oxide (GO) nanosheets into the PAH/TALH multilayers produced GO-incorporated TiO_x films after thermal annealing, which exhibited memory performance with a high ON/OFF current ratio of ∼10⁴. Furthermore, we demonstrate that the switching mechanism of GO-incorporated TiO_x devices can be explained by the charge trap model.