Resistive Switching Behavior of Naturally Sourced L‐Tryptophan‐Based Resistive Random‐Access Memory for Multistate Non‐Volatile Memory Applications

ABSTRACT Driven by the growing interest in naturally sourced materials for next‐generation memory devices, we demonstrate a 6×6 resistive random‐access memory (RRAM) crossbar array that utilizes the standard amino acid L‐tryptophan (L‐trp) as the active layer. The indole ring of L‐trp facilitates trap sites, while its carboxylic acid group enables the formation of a crucial aluminum oxide interfacial layer via reaction with the Al top electrode. The Al/L‐trp/W structured RRAM exhibits reliable bipolar resistive switching with an on/off ratio of 1.94 × 10 4 , endurance of over 1000 cycles, and stable retention characteristics for 10 5 s. Furthermore, the multistate characteristics of the L‐trp‐based RRAM are confirmed by achieving 12 distinguishable resistance states through compliance current modulation from 0.5 to 100 mA. Quantitative analysis demonstrates a minimum adjacent resistance ratio of 1.98, ensuring high state separability. This successful demonstration of 12 distinguishable resistance states in the L‐trp‐based RRAM highlights the significant potential of L‐trp in next‐generation memory devices.