\textbf{Self-sustained current oscillations in NbO}$_{\mathrm{\mathbf{2}}}$\textbf{ thin film vertical devices grown on TiN coated SiO}$_{\mathrm{\mathbf{2}}}$\textbf{/Si substrates using pulsed laser deposition }

Due to its relatively high MIT temperature (1081 K) and current-controlled negative differential resistance, NbO$_{\mathrm{2}}$ is a robust candidate for memory devices and electrical switching applications. Highly stable and self-sustained current oscillations can be generated in NbO$_{\mathrm{2}}$ thin films when attached to a constant voltage source. In this work, we present the self-sustained current oscillatory behavior of NbO$_{\mathrm{2}}$ thin film vertical devices grown on TiN coated SiO$_{\mathrm{2}}$/Si substrates using pulsed laser deposition (PLD). The formation of NbO$_{\mathrm{2}}$ phase was confirmed by Grazing Incidence X-ray Diffractometry (GIXRD), X-ray Photoelectron Spectroscopy (XPS) and current vs. voltage measurements. Probe station tips (tip size \textasciitilde 2$\mu $m) and TiN bottom layer were used as top and bottom contacts. Current pulse measurements, performed in response to applied triangular voltage pulses, showed a non-linear threshold switching behavior for voltage pulse durations of 100 ns and above. Self-sustained current oscillatory behavior was obtained with frequencies ranging from 5 to 12.5 MHz from the film grown in lower (1 mTorr) and 10.5 - 14.8 MHz from the film grown in higher (10 mTorr) O$_{\mathrm{2}}$/Ar mixed growth pressure (\textasciitilde 7{\%} O$_{\mathrm{2}})$ while changing V$_{\mathrm{pp}}$ of the rectangular pulse voltage from 5 -- 12.5 V and 10.5 -- 14.8 V respectively.