We report large amplitude modulation waveforms as large as~10 V using vanadium dioxide micro-channel devices operating under current-controlled conditions. The self-sustained electrical oscillations were generated by controlling the applied current in the negative differential resistance region of the investigated devices. An appropriate value of internal capacitance was achieved as parasitic capacitance in the device structure to stabilize the electrical oscillations. This eliminates the need of an external pulsed source or any external passive component connected to the micro-channel devices. Amplitude and frequency of the oscillation were tuned by illuminating the device micro-channel with an external laser. An equivalent circuit model was developed to simulate the waveforms. A good agreement between experiment and simulation was verified.

The reversible insulator-to-metal phase transition of vanadium dioxide (VO 2 ) makes this material an ideal candidate to realize electrical oscillators with both tunable frequency and amplitude characteristics. Here we report results for VO 2 oscillators operating under voltage actuation. Large amplitude electrical oscillation waveforms with stable frequency were observed for the investigated devices. The frequency and amplitude of the waveforms were controlled by changing the values of the capacitor in the oscillator circuit, the supply voltage and by varying the temperature of the devices. An equivalent circuit model was developed to simulate the waveforms. A good agreement between simulations and experiments was verified for different oscillator circuit conditions. We also present a graphical phase portrait analysis of the differential equations governing the time-dependent external capacitor voltage in the oscillator circuit. A simple technique to analyze the operating conditions of these devices was developed based on this approach using the oscillator circuit parameters and the resistances of the VO 2 device in the insulating and metallic states.

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