Memristors are a new class of devices that can replace integrated electronic devices in applications involving sophisticated computing, digital and analog circuits, and neuromorphic networks. In this work, we report a transparent synaptic memristor with the nano-device structure indium tin oxide/zinc oxide/ indium tin oxide (ITO/ZnO/ITO) that exhibits potentiation and depression behavior resembling the brain’s synapses. The layers of ZnO and ITO were deposited by radio frequency (RF) magnetron sputtering. Nano-dimension of the sandwiched layer results in high electric field intensity between the electrodes even at small potentials and facilitates the migration of ions. This synaptic device has spike-dependent synaptic plasticity and paired-pulse facilitation/depression. This study reveals that the synaptic weight changes are more prominent when wider pulses or shorter-interval pulses are applied. The switching behavior of the ZnO-based memristor is studied by altering the top electrodes. Devices with top electrodes made of ITO and silver (Ag) demonstrated bipolar, forming free and filament-type resistive switching. Interface-type resistive switching was observed in a device with gold (Au) as the top electrode (Au/ZnO/ITO). The conduction mechanics of these memristors were also investigated.

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