隨著電子元件朝向低功耗與環境永續發展，開發具備高效能與可生物分解特性的記憶體元件已成為重要研究方向。生質材料因其低成本、可溶液製程及環境友善特性，逐漸受到關注。其中，洋菜（agar）具備優異的成膜能力與內在離子傳輸特性，為電阻式隨機存取記憶體（RRAM）之潛在材料。然而，洋菜基記憶體仍面臨切換行為不穩定、操作電壓偏高及導電絲（conductive filament）形成難以控制等關鍵問題，限制其實際應用。
本研究針對上述問題，系統性探討頂電極材料與離子摻雜對洋菜基 RRAM 元件電性之影響。元件結構以 ITO/glass 為基板，採用純洋菜與摻雜硝酸銀（AgNO₃）之洋菜薄膜作為主動層，並分別搭配銀（Ag）、鋁（Al）與銦（In）作為頂電極。透過傅立葉轉換紅外光譜（FTIR）、原子力顯微鏡（AFM）及 X 光光電子能譜（XPS）分析材料特性，結果顯示 AgNO₃ 摻雜在不破壞洋菜主體結構的情況下，能有效改變局部化學環境並引入可遷移之 Ag⁺ 離子，進而參與導電絲之形成機制。
電性量測結果顯示，AgNO₃ 摻雜可顯著提升導電絲形成的可控性與切換穩定性，使 RESET 電壓由約 −5 V 降至約 −3 V，並達到 10³–10⁵ 之 on/off ratio 。此外，頂電極材料對元件表現具有決定性影響。Ag 電極因其高電化學活性，導致過度導電與切換不穩定現象；相較之下，Al 與 In 電極能有效調控導電絲生成與破壞過程，使高阻態（HRS）與低阻態（LRS）具有良好區分性。其中，採用 Al 電極並搭配 AgNO₃ 摻雜之元件，展現 μA 等級之低操作電流與穩定切換特性，顯示其於低功耗記憶體應用之潛力。
本研究釐清了生質 RRAM 系統中離子傳輸與電極材料對導電絲行為之交互影響機制，並證明結合離子工程與頂電極優化可有效實現低電壓、低功耗且穩定之電阻切換特性。此成果不僅驗證洋菜作為記憶體主動層之可行性，亦為未來綠色電子與可持續記憶體技術提供重要設計依據與發展方向。

The development of low-power and environmentally sustainable memory devices has become increasingly important for next-generation electronics. Bio-derived materials have emerged as promising candidates due to their biodegradability, low cost, and solution-processability. Among them, agar exhibits excellent film-forming capability and intrinsic ionic transport properties, making it suitable for resistive random-access memory (RRAM) applications. However, agar-based memory devices typically suffer from unstable switching behavior, high operating voltage, and poor controllability of conductive filament formation, which limit their practical applicability.
In this work, we systematically investigate the effects of top electrode engineering and ionic incorporation on the electrical performance of agar-based RRAM devices. Devices were fabricated on ITO/glass substrates using pristine agar and AgNO₃-incorporated agar as active layers, combined with Ag, Al, and In top electrodes. Material characterizations, including FTIR, AFM, and XPS, confirm that AgNO₃ incorporation modifies the local chemical environment while preserving the structural integrity of the agar matrix, and introduces mobile Ag⁺ ions that actively participate in resistive switching.
Electrical measurements reveal that AgNO₃ incorporation significantly enhances filament formation and switching stability, reducing the RESET voltage from approximately −5 V to −3 V, while achieving an on/off ratio of 10³–10⁵. The choice of top electrode is found to play a decisive role in regulating switching behavior. Devices with Ag electrodes exhibit excessive electrochemical activity, leading to overconductive behavior and degraded switching contrast. In contrast, Al and In electrodes provide more controlled filament formation, resulting in improved switching uniformity and distinguishable resistance states. Notably, the AgNO₃-incorporated devices with Al top electrodes demonstrate low operating current in the μA range and stable switching characteristics, highlighting their suitability for low-power applications.
This study provides a clear understanding of the interplay between ionic transport and electrode-dependent filament control in bio-based RRAM systems. The results demonstrate that combining ionic engineering with top electrode optimization is an effective strategy to achieve low-voltage, low-power, and stable resistive switching. These findings not only validate the feasibility of agar as an active material for memory devices but also offer valuable design guidelines for the development of sustainable and biodegradable electronic systems.

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