Organic One-Transistor-Type Nonvolatile Memory Gated with Thin Ionic Liquid-Polymer Film for Low Voltage Operation

As one of the most emerging next-generation nonvolatile memories, one-transistor (1T)-type nonvolatile memories are of great attention due to their excellent memory performance and simple device architecture suitable for high density memory arrays. In particular, organic 1T-type memories containing both organic semiconductors and insulators are further beneficial because of their mechanical flexibility with low cost fabrication. Here, we demonstrate a new flexible organic 1T-type memory operating at low voltage. The low voltage operation of a memory less than 10 V was obtained by employing a polymer gate insulator solution blended with ionic liquid as a charge storage layer. Ionic liquid homogeneously dissolved in a thin poly­(vinylidene fluoride-<i>co</i>-trifluoroethylene) (PVDF-TrFE) film gave rise to low voltage operation of a device due to its high capacitance. Simultaneously, stable charge trapping of either anions or cations efficiently occurred in the polymer matrix, dependent upon gate bias. Optimization of ionic liquid in PVDF-TrFE thus led to an air-stable and mechanically flexible organic 1T-type nonvolatile memory operating at programming voltage of ±7 V with large ON/OFF current margin of approximately 10³, reliable time-dependent data retention of more than 10⁴ seconds, and write/read endurance cycles of 80

Electrically Tunable Soft-Solid Block Copolymer Structural Color

One-dimensional photonic crystals based on the periodic stacking of two different dielectric layers have been widely studied, but the fabrication of mechanically flexible polymer structural color (SC) films, with electro-active color switching, remains challenging. Here, we demonstrate free-standing electric field tunable ionic liquid (IL) swollen block copolymer (BCP) films. Placement of a polymer/ionic liquid film-reservoir adjacent to a self-assembled poly(styrene-<i>block</i>-quaternized 2-vinylpyridine) (PS-<i>b</i>-QP2VP) copolymer SC film allowed the development of red (R), green (G), and blue (B) full-color SC block copolymer films by swelling of the QP2VP domains by the ionic liquid associated with water molecules. The IL–polymer/BCP SC film is mechanically flexible with excellent color stability over several days at ambient conditions. The selective swelling of the QP2VP domains could be controlled by both the ratio of the IL to a polymer in the gel-like IL reservoir layer and by an applied voltage in the range of −3 to +6 V using a metal/IL reservoir/SC film/IL reservoir/metal capacitor type device

Infrared Nanoimaging of Hydrogenated Perovskite Nickelate Memristive Devices

Solid-state devices made from correlated oxides, such as perovskite nickelates, are promising for neuromorphic computing by mimicking biological synaptic function. However, comprehending dopant action at the nanoscale poses a formidable challenge to understanding the elementary mechanisms involved. Here, we perform operando infrared nanoimaging of hydrogen-doped correlated perovskite, neodymium nickel oxide (H-NdNiO3, H-NNO), devices and reveal how an applied field perturbs dopant distribution at the nanoscale. This perturbation leads to stripe phases of varying conductivity perpendicular to the applied field, which define the macroscale electrical characteristics of the devices. Hyperspectral nano-FTIR imaging in conjunction with density functional theory calculations unveils a real-space map of multiple vibrational states of H-NNO associated with OH stretching modes and their dependence on the dopant concentration. Moreover, the localization of excess charges induces an out-of-plane lattice expansion in NNO which was confirmed by in situ X-ray diffraction and creates a strain that acts as a barrier against further diffusion. Our results and the techniques presented here hold great potential for the rapidly growing field of memristors and neuromorphic devices wherein nanoscale ion motion is fundamentally responsible for function