Synaptic VO2 Resistor on Glass Substrate for Neuromorphic Circuits

Vanadium dioxide (VO2) is material undergoing metal-insulator phase transition from the monoclinic insulating phase at room temperature to the high-temperature rutile metal phase. The metal-insulator phase transition is accompanied with dramatic changes in conductivity and optical characteristics of VO2. In contrast to single crystal VO2 for polycrystalline VO2 films there is a fairly wide hysteresis on conductivity temperature dependence. This makes it possible to create a synaptic resistor for neuromorphic circuits based on VO2. This paper reports on the VO2 polycrystalline film based synaptic resistor fabrication on glass substrate. By matching the sublayer composition and the annealing conditions it was shown being possible to synthesize high quality polycrystalline VO2 film on glass substrate. Synaptic resistors for a neuromorphic circuit were fabricated based on the synthesized film, with their resistances being reversibly controlled by optical stimulus. The synaptic weight value accuracy was found to be 2.9% allowing to distinguish up to 34 states of the synaptic resistor.