Mimicking synaptic plasticity based on TiO2/MgO film resistive switching device

Abstract

The TiO₂/MgO composite film was prepared via atomic layer deposition, exhibiting superior resistive switching (RS) performance compared to pure MgO film, including a higher resistance ratio (R_off/R_on) and enhanced retention. The Ag/TiO₂/MgO/ITO device exhibited gradual RS characteristics, making it suitable for neuromorphic applications. The device also displayed excellent multilevel RS properties analogous to synaptic plasticity. When a series of positive or negative scanning voltages with progressively increasing amplitudes were applied, the resistance of the device switched and remained at correspondingly higher or lower states, effectively mimicking synaptic potentiation or depression in an amplitude-dependent manner. Furthermore, long-term potentiation and depression behaviors were observed under the time-dependent stimulation. As the pulse voltage amplitude increased, fewer pulses were required to set the device to a specific state. Conversely, lower voltage necessitated more pulses to facilitate Ag ions migration and conductive filament formation. This dynamic mimics synaptic weight modulation, where the evaluation of filaments over time corresponds to synaptic adjustment. Therefore, applying higher or lower amplitude voltages for longer or shorter durations aligns with the observation, where varying stimuli to the presynaptic membrane modulate synaptic weight, thereby strengthening (and weakening) the synaptic signal. The pulse amplitude and duration thresholds modulate the RS behavior of the composite TiO₂/MgO film effectively mimic the learning and forgetting processes of human brain memory.