Deep Proton Insertion Assisted By Oxygen Vacancies For Long-Term Memory In Vo2 Synaptic Transistor

Reversible phase transformation of correlated oxides by field-driven ionic process present opportunity to efficiently transduce between ionic transfer and electrical currents in insertion-based reconfigurable transistors. However, the switching rate of insertion transistors is fundamentally limited by the slow rate of ionic insertion into the lattices of correlated oxides. Here, it is demonstrated that preformed oxygen vacancies in VO2-delta lattices strongly accelerate proton insertion by low gate voltage in synaptic transistors. As the degree of oxygen deficiency delta increases in VO2-delta transistors, the steepness of phase transformation and transconductance increase during the voltage sweep at the expense of the channel current modulation. Theoretical and experimental analyses reveal that the accelerated of H+ kinetics in the VO2-delta lattice occurs because immobile oxygen vacancies reduce the energy barrier to H+ migration. In an electronic synapse, this facile H+ migration in VO2-delta lattices renders "inscribed" memory by positioning the H+ neurotransmitter far from the electrolyte/VO2-delta interface. This discovery suggests a strategy to improve the learning and memory processes of artificial synaptic devices by controlling the density of intrinsic defects in the lattice framework to achieve efficient ion exchange.