Continuous phase tuning of vanadium dioxide films using robust feedback mechanism

Vanadium dioxide (VO{2}) undergoes a metal-insulator transition (MIT) around a temperature close to 68° C, which enables many digital-like applications including memory devices, sensors, phase change switches, etc. However, the digital-like abruptness of the MIT of VO{2} across a sharp and narrow temperature window limits its usage in the development of applications that demand an analog operation mode with continuously tunable properties. Achieving precise and continuous phase tuning of VO{2} films will enable more powerful and capable devices for analog applications in different fields. Unlike the traditional chemical doping approach which sacrifices the modulation depth, this work incorporates a robust feedback control mechanism into VO{2} films to achieve continuous phase tuning of the intermediate states within the entire phase transition region. In order to attenuate the adverse effect of hysteresis nonlinearity and manufacturing uncertainties associated with the phase transition of VO{2}, the uncertainty and disturbance estimator (UDE)-based robust output feedback control approach is developed to achieve the precise continuous phase tuning without using detailed hysteresis modeling information. The effectiveness of the proposed methodology is then verified through an experimental validation.