Effects of drying temperature and ethanol concentration on bipolar switching characteristics of natural Aloe vera-based memory devices

Abstract

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.

Effects of Electrode Materials on Charge Conduction Mechanisms of Memory Device Based on Natural Aloe Vera

“…Moreover, the set and reset voltages use, available at https:/www.cambridge.org/core/terms. https://doi.org/10.1557/adv.2016.522 reported here occur at lower magnitude and at opposite polarity of the previous report [11], suggesting that the resistive switching behaviors can be induced by different conduction mechanisms.…”

“…Subsequent state transition (set process) can only occur in the fourth voltage sweep, where a smaller bias voltage (0.3 V and 0.6 V for devices using Al and Ag as top electrode respectively) is required to toggle the device as compared to the first voltage sweep. The sequence of voltage sweeps employed here is different from the previous report [11] causing significant differences in the J-V characteristics. In this paper, a forming process is required to prepare the pristine device for subsequent switching cycles.…”

“…The Aloe vera gel and samples were prepared according to the procedures described elsewhere [11]. Two sets of samples were prepared, using Al and Ag as the top electrodes of the devices.…”

“…Recently, the demonstration of inducing responses that mimic memristor behaviors in living Aloe vera plants has further expanded its potentials for electronic memory applications [9]. The notion has been conceptualized when thin films of commercial [10] and natural [11] Aloe vera gel are explored for nonvolatile memory applications.…”

“…The bipolar switching in thin films of natural Aloe vera gel are attributed to charge trapping and detrapping processes as charges are transported across the Aloe vera film via spacecharge-limited conduction (SCLC) [11]. In contrary, many reports [12][13][14][15][16][17][18][19][20] attribute the resistive switching behaviors in thin films of bio-organic materials to the formation and dissolution of a conductive filament bridging the top and bottom electrodes.…”