Alcohol-Dependent CuI Iodization Kinetics toward In Situ Repairable and Fault-Tolerant RRAM Switching

We report a solvent-engineered, low-temperature solution process for fabricating device-grade copper iodide (CuI) thin films for resistive random-access memory (RRAM) applications. Copper films deposited by thermal evaporation were iodized by using methanol, ethanol, and isopropanol (IPA) to yield CuI layers with distinct microstructures and defect states. Solvent-dependent iodization kinetics modulated the film stoichiometry, grain morphology, and defect density, resulting in tunable resistive switching behavior. Among the tested solvents, IPA produced the most uniform and densely packed films, achieving a high current ON/OFF ratio (∼10⁴), excellent endurance (∼10³ cycles), and stable device yield. The current conduction and defect-mediated switching mechanisms were systematically analyzed, revealing the influence of solvent-induced microstructural variations on the device reliability. Importantly, solvent mediation is identified as a key parameter governing both the morphology and long-term stability of CuI layers. By correlating process parameters with device performance and implementing an integrated in situ faulty-cell repair concept, this work highlights practical pathways for integrating CuI devices into self-healing and large-scale neuromorphic and memory systems.