Electronic imitation of behavioral and psychological synaptic activities using TiO_x/Al₂O₃-based memristor devices

Seeking an effective electronic synapse to emulate biological synaptic behavior is fundamental for building brain-inspired computers. An emerging two-terminal memristor, in which the conductance can be gradually modulated by external electrical stimuli, is widely considered as the strongest competitor of the electronic synapse. Here, we show the capability of TiO_x/Al₂O₃-based memristor devices to imitate synaptic behaviors. Along with analog resistive switching performances, the devices replicate the bio-synapse behaviors of potentiation/depression, short-term-plasticity, and long-term-potentiation, which show that TiO_x/Al₂O₃-based memristors may be useful as electronic synapses. The essential memorizing capabilities of the brain are dependent on the connection strength between neurons, and the memory types change from short-term memory to long-term memory. In the TiO_x/Al₂O₃-based electronic synaptic junction, the memorizing levels can change their state via a standard rehearsal process and also via newly introduced process called "impact of event" i.e. the impact of pulse amplitude, and the width of the input pulse. The devices show a short-term to long-term memory effect with the introduction of intermediate mezzanine memory. The experimental achievements using the TiO_x/Al₂O₃ electronic synapses are finally psychologically modeled by considering the mezzanine level. It is highly recommended that similar phenomena should be investigated for other memristor systems to check the authenticity of this model.