Controllable oscillations driven by resistive switching transitions in single crystals of vanadium oxide bronzes

Vanadium oxide bronzes (M_xV₂O₅, M = Cu, Pb, and Na) exhibit a variety of correlated electronic behavior controlled by external stimuli such as electric field and temperature. Transport characteristics of ε-Cu_xV₂O₅ and β-Cu_xPb_yV₂O₅ single crystals are studied, and the current-voltage (IV) characteristics show abrupt transitions from a low conductance to a high conductance state with distinct hysteretic behavior. The switching transitions in two-terminal devices of vanadium oxide bronzes have the potential to be exploited in neuromorphic computing applications as synaptic devices (relaxation oscillators) owing to their potential efficiency and scalability. Relaxation oscillators with sustainable oscillations are demonstrated in these bronzes using a simple RC circuit and external parameters such as switching voltage, resistor/capacitor values significantly alter the oscillations and are tuned to produce oscillators with tunable frequency range. The coexistence of conducting and non-conducting phases and the means to electrically control the switching to tune the oscillations will be discussed. In addition to applications in neuromorphic computing, the switching transitions and the resulting oscillators are excellent model systems to study nonlinear dynamics and to extract electrical and thermal transport parameters useful for computing applications.