Impact of metallic and vacancy-oriented filamentary switching on memristor device based on Cs₂AgInCl₆ double halide perovskite

Double halide perovskite (DHP) has become a point of significant interest in recent years due to its exceptional stability. More recently lead-free DHPs have lowered the importance of toxic lead-based halide perovskite owing to the similar diversity in fundamental properties. Herein, we have made an effort to eliminate other lead-free DHPs to observe the influence of electrode material on the memristive property of a device. Cs₂AgInCl₆ is DHP well-known as semiconducting in nature with a wider band gap. A symmetrical or non-distorted DHP structure was required to study the effect of electrode material on memristor. Thus, two types of devices have been fabricated using cubic Cs₂AgInCl₆ as the active material with a silver (Ag) and gold (Au) as top electrodes (TEs), while keeping the bottom electrode ITO common. Both the devices exhibited bipolar memory behavior with some variation in switching parameters. Further investigation showed that the device with Ag as TE could not be used for longer period of time as endurance failure occurred during the measurement due to the formation of permanent Ag-based conducting filament through functional material. On the other hand, the device with Au as the top electrode successfully demonstrated reproducible writing/erasing, high-density storage, and stability for a very long period of time. The Au TE based device also exhibited typical and essential synaptic behavior such as pair-pulsed facilitation, long-term potentiation and depression. All these changes in device conductance were attributed to the valance change mechanism in the Cs₂AgInCl₆ matrix associated with the migration of Cl⁻ ions and vacancies affirmed by the conducting atomic force microscopy (c-AFM).