Light-induced double enhancement of resistive switching and control of ferromagnetism in ZnO film

Abstract

The ZnO film on Pt/Ti/SiO2/Si substrate has room temperature ferromagnetism. The ITO (Indium tin oxide) electrodes were prepared on ZnO film for the measurement of resistive switching. The ITO/ZnO/Pt device has stable coexistence of resistive switching (RS) and ferromagnetism regulation, and both of these phenomena can be enhanced by light illumination. The mechanism of RS behavior and the source of ferromagnetism are related to oxygen vacancies. The movement of oxygen vacancies (or the reverse movement of oxygen ions) under the electric field will cause the formation and rupture of conductive filaments, which affects the resistance state and the ferromagnetism of the device. The photo-generated electron-hole pairs will be produced in the ZnO film under light illumination, and separated by built-in electric field. The combination of photo-generated holes and chemically-adsorbed oxygen ions affects the RS behavior, while the combination of photo-generated electrons and doubly ionized oxygen vacancies enhances the ferromagnetism.