Forming-Free, Low-Voltage, and High-Speed Resistive Switching in Ag/Oxygen-Deficient Vanadium Oxide(VO_<i>x</i>)/Pt Device through Two-Step Resistance Change by Ag Filament Formation

Abstract

Forming-free, low-voltage, and high-speed resistive switching is demonstrated in an Ag/oxygen-deficient vanadium oxide (VO x )/Pt device via the facilitated formation and rupture of Ag filaments. Direct current (DC) voltage sweep measurements exhibit forming-free switching from a high-resistance state (HRS) to a low-resistance state (LRS), called SET, at an average V SET of +0.23 V. The reverse RESET transition occurs at an average V RESET of −0.07 V with a low RESET current of <1 mA. Reversible switching operations are stable with an HRS/LRS resistance ratio >10 3 during repeated measurements for thousands of cycles. In pulse measurements, switching occurs within 100 ns at an amplitude of +1.5 V. Notably, a two-step resistance change is observed in the SET operation, where the resistance first partially decreases due to Ag + ion accumulation in VO x and then further decreases to the LRS after hundreds of nanoseconds upon complete filament formation. The VO x layer deposited to be mostly amorphous with oxygen deficiency from V 2 O 5 has abundant vacancies and expedites Ag + ion migration, thus realizing forming-free, high-speed, and low-voltage switching. These characteristics of the facilitated Ag filament formation using the substoichiometric VO x layer are highly beneficial for use as stand-alone nonvolatile memory and in-memory computing elements.