High-Yield and Uniform NbO_<i>x</i>-Based Threshold Switching Devices for Neuron Applications

Abstract

Threshold switching (TS) devices based on NbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> materials show intriguing potential for constructing artificial neurons in a neuromorphic machine. However, the high electroforming voltage, the low TS yield, and the poor device uniformity hinder the practical application of NbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> -based TS devices. In this work, we systematically investigate the effect of film composition on device performance by adjusting the oxygen contents in the NbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> films. The electroforming voltage decreases with lowering the oxygen content, and the forming yield for activating TS behavior increases without an additional reset process. Moreover, we propose a stacked method by inserting a NbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>y</i></sub> layer with high oxygen content between the low oxygen NbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> layer and the bottom electrode. The intercalated NbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>y</i></sub> layer serves as a virtual bottom electrode after breakdown, enhancing the local electrical field and improving cycle-to-cycle stability and device-to-device uniformity. These results demonstrate that the device performances are greatly improved by optimizing the oxygen content and structure, guiding for practical applications of NbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> -based TS devices in neuromorphic computing.