Three-terminal memcapacitive synapses based on a thin H-TiO2 layer

Taking inspiration from the biological synapse, an ion-based memcapacitor has been considered as a promising candidate for mimicking the biological synapse. Herein, we propose an Ag/H3PO4-PVA/TiO2/MXene structure to elucidate the physical concept of the proposed three-terminal ion-based memcapacitive synapse. Under external voltage stimuli, the effect of the electrical double layer induces proton accumulation at the interface of H3PO4-PVA/TiO2, generating weak hydrogen bonds between the proton and TiO2 to form H-TiO2. According to the hydrogen bonding mechanism, which is analogous to neurotransmitter transmission in synapses, this three-terminal structure realizes the modulation of proton-enhanced and -suppressed transport behavior under voltage stimuli with different polarities by leveraging this thin H-TiO2 layer. The behavior of accumulated ions at the interfaces of the H3PO4-PVA/TiO2 and TiO2/MXene could be synchronously reflected by the bottom electrode potential, so that this three-terminal memcapacitor initially achieves the read/write separation. As a result, this three-terminal memcapacitor exhibits tunable short-term and long-term synaptic plasticity. Our study showcases the development of dynamically reconfigurable artificial synaptic memcapacitors capable of emulating neural functions.