Enhanced resistive switching of silver copper iodide thin films prepared by interfacial phase formation

Resistive random-access memory (ReRAM), an alternative to conventional charge storage memory, employs the switching of a resistive material between high-resistance and low-resistance states, which can be generated by the formation/dissolution of metal filaments bridging the two electrodes in the cell. Silver iodide (AgI) is a promising solid electrolyte for ReRAM cells, but its application is hindered by poor photostability and low electrical conductivity. Herein, a Cu-substituted β-AgI system, β′-Ag_0.7Cu_0.3I, was successfully prepared via sequential deposition of a Cu metal layer onto a AgI thin film by a galvanic reaction, which induced the spontaneous incorporation of Cu⁺ cations into the AgI lattice. Cu substitution at the Cu–AgI heterojunction interface is a novel way to modulate the chemical composition and improve the resistive switching properties of intrinsic polycrystalline AgI thin films. We compared the resistive switching properties of a ReRAM thin film devices based on β′-Ag_0.7Cu_0.3I with those based on pristine β-AgI. This device exhibited enhanced performance with high ON/OFF ratio (∼10⁴) and low working voltage compared with the β-AgI-based device. These results strongly suggest that binary metal halide materials can serve as simple model systems for the efficient formation of metal filaments and have potential low-cost, low-power memory applications.