Here, various synaptic functions and neural network simulation based pattern-recognition using novel, solution-processed organic memtransistors (memTs) with an unconventional redox-gating mechanism are demonstrated. Our synaptic memT device using conjugated polymer thin-film and redox-active solid electrolyte as the gate dielectric can be routinely operated at gate voltages (VGS) below − 1.5 V, subthreshold-swings (S) smaller than 120 mV/dec, and ON/OFF current ratio larger than 108. Large hysteresis in transfer curves depicts the signature of non-volatile resistive switching (RS) property with ON/OFF ratio as high as 105. In addition, our memT device also shows many synaptic functions, including the availability of many conducting-states (> 500) that are used for efficient pattern recognition using the simplest neural network simulation model with training and test accuracy higher than 90%. Overall, the presented approach opens a new and promising way to fabricate high-performance artificial synapses and their arrays for the implementation of hardware-oriented neural network.

Low-voltage, solution-processed organic thin-film transistors (OTFTs) have tremendous potential to be key components in low-cost, flexible and large-area electronics. However, for these devices to operate at low voltage, robust and high capacitance gate dielectrics are urgently needed. Herein, the fabrication of OTFTs that operate at 1 V is reported. These devices comprise a solution-processed, self-assembled monolayer (SAM) modified tantalum pentoxide (Ta2O5) as the gate dielectric. The morphology and dielectric properties of the anodized Ta2O5 films with and without n-octadecyltrichlorosilane (OTS) SAM treatment have been studied. The thickness of the Ta2O5 film was optimized by varying the anodization voltage. The results show that organic TFTs gated with OTS-modified tantalum pentoxide anodized at 3 V (d ~7 nm) exhibit the best performance. The devices operate at 1 V with a saturation field-effect mobility larger than 0.2 cm2 V−1 s−1, threshold voltage −0.55 V, subthreshold swing 120 mV/dec, and current on/off ratio in excess of 5 × 103. As a result, the demonstrated OTFTs display a promising performance for applications in low-voltage, portable electronics.

Nonvolatile resistive switching based memristor and memtransistor devices have emerged as a leading platform in neuromorphic computing. In this work, we have fabricated a multifunctional synaptic transistor (ST) using a conjugated polymer P3HT channel and a superionic rubidium silver iodide (RbAg4I5) thin film coated over a polyethylene oxide (PEO) layer as the gate dielectric. Large hysteresis in the transfer curve represents the memristive behavior with at least 105 current On/Off ratio. Enormously large specific capacitance induced by the electrical double layers at the interfaces of PEO/RbAg4I5 dielectric induces polaron (P3HT+) generation in the channel through bound states formation by the electrons with Ag+ ions and consequent movement of iodine (I−) counter ions toward the P3HT channel under a negative gate bias stress. This is strongly supported by the blue shift of the Raman peak from 1444.2 to 1447.9 cm−1 and the appearance of a new peak at 1464.6 cm−1. Interestingly, the proposed ST device exhibits various synaptic actions, which include an excitatory postsynaptic current, paired-pulse facilitation, and short-term potentiation to long-term potentiation after repeated rehearsal on top of standard nonvolatile data storage capability. Our ST also depicts an enhanced retention to 103 s and more than 103 discrete On- and Off-states during potentiation and depression function modulation, respectively, just by consuming a very low energy of about 2.0 pJ per synaptic event. These results are very significant to make this organic synaptic transistor as a potential candidate in terms of the desired metrics for neuromorphic computation at low cost and improved accuracy in the future.

Ultra-thin anodized aluminium dielectric films: the effect of citric acid concentration and low-voltage electronic applications. Nanotechnology.

The design of solution-processed transparent transistors with ultralow-voltage operations and a planar architecture can be a paradigm shift toward the realization of ultralow-power electronic circuits due to conformity with the existing complementary metal oxide semiconductor (CMOS) platform. We report a robust and solution-based device fabrication protocol to demonstrate near-steep-slope transparent oxide field-effect transistors (TO-FETs) with operating voltages at or below 0.5 V using a nanometer-thick amorphous indium–gallium–zinc oxide (a-IGZO) channel and an ultrathin anodized aluminum dielectric. The transmittance spectra confirm the excellent transparency (>98%) of the a-IGZO thin film for the entire visible range. Hysteresis-free transfer characteristics exhibit the film’s operation as an n-channel TO-FET with a low threshold voltage (∼96 mV), a near-thermionic subthreshold swing (SS) down to 85 mV/dec, and a high ON/OFF current ratio (>105). The consistency of these TO-FET results of ultralow-power operation with a near-steep-slope nature was demonstrated by enormously large specific capacitance values of ultrathin anodized aluminum gate dielectrics as the forcing factor. Moreover, half-volt operation of the TO-FET is also flawlessly demonstrated at room temperature with hysteresis-free characteristics. Hence, these planar TO-FETs could be a potential technological breakthrough for the future of cost-effective and high-performance transparent ultralow-power applications, including quantum and neuromorphic computation fields of research.