Study on electrode modification in NbOx-based threshold switching device and its electrical characteristics and oscillation

Abstract

The self-oscillating behavior of the threshold switching devices is widely investigated due to its novel emerging applications such as a spike generator in neuromorphic computing, stochastic computing device, and security device. The NbO$_x$-based threshold switching (TS) device is one of the most promising candidates for those applications. One of the issues for the applications is the limited amplitude of the output spike waves, while its frequency modulation is quite flexible. In this study, we propose an electrode-modified NbO$_x$-based TS device generating a high amplitude spike. We fabricated a conventional TS device (Ti/NbO$_x$/Pt) and the electrode-modified TS device (Ti/Au nanodots/NbO$_x$/Pt) and compared their threshold switching and self-oscillation characteristics. The electrode-modified device showed a wider difference between the threshold voltage and hold voltage and a higher on/off ratio, allowing a higher maximum current with a lower oscillation frequency. Based on the thermodynamic simulation-based modeling and in-depth analysis, we suggest a threshold filament model which compares the width and length of the conduction of the two devices, which can plausibly explain the results. Such spike amplifying feature may enhance the use of the NbO$_x$-based TS device for emerging neuromorphic applications.