Extracted, formulated, and processed natural Aloe vera has been used as an active layer for memory applications. The functional memory device is realized by a bottom-up structure of ITO/Aloe vera/Al in which the Aloe vera is spin-coated after mixing with different concentrations of ethanol (0-80 wt%) and subsequently dried at different temperatures (50-120 °C). From the current density-voltage measurements, the device can exhibit a reproducible bipolar switching characteristic with pure Aloe vera dried at 50 °C. It is proposed that charges are transported across the Aloe vera layer via space-charge-limited conduction (SCLC), and clusters of interstitial space formed by the functional groups of acemannans and de-esterified pectins in the dried Aloe vera contribute to the memory effect. The formation of charge traps in the Aloe vera layer is dependent on the drying temperature. The drying temperature of a memory-switching Aloe vera layer can be extended to 120 °C with the addition of appropriate amounts of ethanol. The concept of using natural Aloe vera as an active material for memory applications has been demonstrated, and the read memory window, ON/OFF ratio, and retention time are approximately 5.0 V, 10(3), and >10(4) s, respectively.

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To enable long-term progress, next-generation nonvolatile memories should function on the basis of new concepts that are different from the conventional charge storage in floating-gate transistors. [4][5][6] Of the emerging storage principles, electrically modulated resistive switching behaviors in metal-insulator-metal (MIM) structures could be an intriguing concept to redefine the frontiers of next-generation nonvolatile memories. [7][8][9][10][11][12][13][14] Such implementation offers promising advantages in several key aspects, including down-scalability, switching speed, power consumption, and fabrication cost.Resistive switching has been demonstrated in a wide variety of inorganic [7][8][9][10] and organic [11][12][13][14] materials, which are generally deposited as a continuous thin film sandwiched in between two conductive electrodes forming a MIM structure. However, careful consideration should be taken during the fabrication process, because deposition of these materials using various power-demanding methods (e.g., thermal evaporation, molecular beam epitaxy, and chemical vapor deposition) could possibly lead to an energy-imbalance situation. [15] Furthermore, utilization of materials derived from nonrenewable resources (e.g., mined minerals and fossil fuels) could raise critical issue regarding sustainability. In general, these materials are chemically robust and thus require an infinitely long period for natural decomposition after disposal, leaving behind massive volumes of electronic waste overwhelming landfills around the world. [16] In tandem with the growing environmental awareness and the proliferation of disposable electronics, there is an urgent need to develop more electronic applications based on the greener bio-organic materials, [16,17] which are generally derived from living (or once-living) organisms that are abundant in the nature. Bio-organic materials are not only biodegradable, biocompatible, and environmentally benign to provide a sustainable solution in addressing the environmental concerns, but also exotic for next-generation electronics realization. Recently, resistive switching behaviors demonstrated in several bio-organic MIM structures (Table S1, Supporting Information) have garnered considerable attention owing to their potentials as a plausible alternative for next-generation nonvolatile memories.Growing environmental awareness has prompted a paradigm shift toward using green materials for various electronic applications. Bio-organic materials are promising candidates attributable to their inherent biocompatibility, biodegradability, and environmental friendliness. Here, a nonvolatile memory device based on resistive switching in a bio-organic polysaccharides film is presented. The polysaccharides are extracted from natural Aloe vera gel using facile alcohol precipitation. Optimal film deposition is achieved through spin-coating followed by drying at 120 °C, which is higher than the usual processing temperature of commercial Aloe vera gel. Both bipolar and unipolar resistiv...

Resistive switching behaviors in Aloe vera films are being explored for nonvolatile memory applications. A simple structure in which the Aloe vera films sandwiched in between a top and bottom electrode are used. The switching behaviors of the devices in which the Aloe vera film is dried at different temperatures and the roles of top electrode materials (Al and Ag) are investigated. Current density-voltage measurements reveal that filamentary conduction is the dominant conduction process inducing resistive switching characteristics in Aloe vera films. Device with Al-top electrode requires a forming voltage higher than devices with Ag-top electrode, due to the tendency of oxide formation of these materials. The resistive switching behaviors are highly reproducible, as demonstrated by the data retention performance over an interval of 10 4 s and endurance capability of over 100 cycles.

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Formulated, processed, and dried Aloe polysaccharides thin film sandwiched between ITO as bottom electrode and Au as top electrode has been adopted as an artificial synapse to emulate behavior of neuromorphic computing. The synaptic plasticity or weight has been modulated with this simple metal-insulator-metal structure by applying voltage sweep and voltage pulse, with excitatory postsynaptic current being monitored. Synaptic potentiation and depression has been demonstrated by applying 6 consecutive sweeps of voltage in positive and negative polarity, respectively. By varying number (10 – 50) of voltage pulses, variable synaptic weight has been measured with paired pulse facilitation and post-tetanic potentiation indexes of 2.61x10-6and 1.45x10-4, respectively. The short-term plasticity and long-term potentiation can be clearly revealed when applying 40 pulses and beyond, with extracted time constants of approximately 28 s at 40 pulses and 90 s at 50 pulses.

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