Effect of oxygen flow rate on long-term and short-term Schottky barrier modulations in Pd/IGZO/SiO2/p+-Si memristors

In this work, we investigate the long- and short-term Schottky barrier modulations in a Pd/IGZO/SiO2/p+-Si memristor under oxygen flow rate (OFR) control. The thickness of the SiO2 layer verified using transmission electron microscopy (TEM) was found to affect resistive-switching characteristics such as the on/off ratio. A high barrier was observed corresponding to a high OFR in the thermionic emission model. In addition, we present an energy band diagram considering traps and oxygen vacancies for oxygen-rich (O-rich) and oxygen-poor (O-poor) devices. Moreover, physical parameters such as a change in barrier height, activation energy, and potentiation/depression were experimentally extracted through various pulse schemes. Experimental results reveal that an O-rich device has high accuracy with a neural network on the MNIST dataset. In this study, we optimized the resistive-switching characteristics by varying OFR as an experimental factor. Further, we provide guidelines for designing hardware-based neuromorphic systems by separating short- and long-term components.