Analog memory is actively investigated as an information weight pass using change in electric resistance that mimics synaptic plasticity in neuromorphic systems. Resistive memorizing by applying an electric field is an emerging technology as core devices for neuromorphic computing in the future. Among a variety type of resistive memories, transistor structures would have more advantages than two-terminal ones because information-input lines and sensing lines clearly separate and it is fully potential to reduce required power for learning and memory.

In this seminar, I will talk a new concept transistor, which is an electric field-induced resistance changes with dual functions of switch and analog memory by moving protons in a vanadium dioxide (VO2) using a paraelectric-insulating gate. A key point of memory is not gate materials but a crystal transformation between low resistive of VO2 and high resistive materials of proton-doped VO2 in a channel through a penetrating electric field during applying a gate voltage. VO2 is a material with a strongly correlated electron system inducing metal-insulator transition at room temperature. In particular, electrochemical hydrogen doping shows analog change in resistance. This phenomenon suggested the application to dynamic multivalued resistance control device. In recently, it has been experimentally discovered that a heavy hydrogenated VO2 using Pt nano-catalysis particles changes insulating HVO2 having a different crystal structure from monoclinic VO2. Using this property, we proposed a new concept transistor using crystal transformation between high resistive HVO2 and low resistive VO2 states by gate electric field control. In the behavior of temperature dependence of the electrical resistivity of the hydrogenated VO2 (HVO2) thin films and pristine VO2 thin films, HVO2 shows higher resistivity with several orders of magnitudes than that of the pristine VO2, that is, the typical hysteresis properties disappeared in VO2 and it showed insulator behavior. These two materials have stable potentials. Owing to these two minimum potentials, thus, the resistivity having non-volatile multi-state memory appears. This result has a full potential that analog transistors with effective power-less working will be realized in the near future.