Enhancement of temperature-modulated NbO 2 -based relaxation oscillator via interfacial and bulk treatments.

This work demonstrates oscillation frequency modulation in a NbO 2 -based relaxation oscillator device, in which the oscillation frequency increases with operating temperature and source voltage, and decreases with load resistance. An annealing-induced oxygen diffusion at 373 K was carried out to optimize the stoichiometry of the bulk NbO 2 to achieve consistent oscillation frequency shift with device temperature. The device exhibits stable self-sustained oscillation in which the frequency can be modulated between 2 and 33 MHz, and a wider operating voltage range can be obtained. An additional surface treatment step was employed during fabrication to reduce the surface roughness of the bottom electrode and to remove surface contaminants that affect the interfacial properties of the device. The device frequency tunability coupled with high oscillating frequency and high endurance capability of more than 1.5 × 10 8 cycles indicates that the Pt/NbO 2 /Pt device is particularly suitable for applications in an oscillatory neural network.