Noise spectroscopic study of resistive switchings in NbO₂ thin films

Transition metal oxides showcase several phase transitions accessible by external parameters such as temperature, voltage, and stress. NbO₂, exhibiting a voltage-driven insulator to metal transition (IMT) at room temperature, is of great interest as a relaxation oscillator in neuromorphic computing applications. Transport and ultra-low frequency conductance noise spectroscopy measurements are employed to investigate voltage-driven Poole-Frenkel type instability accompanied by a Mott transition in nanoscale thin films of NbO₂. The power spectral density of fluctuations shows a significant deviation from Gaussian behavior in the two transition regions pointing to a possible dynamic coexistence of multiple conducting phases. The microscopic transport mechanisms in NbO₂ can be understood by the Mott-correlated and inhomogeneous transport signatures from transport and noise spectroscopy measurements. Relaxation oscillators built using these nanostructures display oscillation parameters that can be tuned through a wide range by external parameters. The transport measurements are supported by NSF-MRI award 1726303.