Aluminum electrode modulated bipolar resistive switching of Al/fuel-assisted NiO _x/ITO memory devices modeled with a dual-oxygen-reservoir structure

Bipolar resistive switching in Al/fuel-assisted NiO _x (40 nm)/ITO devices is demonstrated in this work. XPS analysis reveals the simultaneous presence of metallic Ni, Ni ₂O ₃, and NiO components in the fuel-assisted NiO _x. The concentration, as well as spreading of the metallic Ni and accompanying oxygen vacancies, are related to the Al/NiO _x interfacial reaction, which is enhanced by the increasing thickness of the Al top electrode. Correspondingly, the preswitching-on voltage decreases while the preswitching-off voltage increases with increasing thickness (from 15 to 60 nm) of Al. However, in regular switching operation, set and reset voltages are considerably lowered for devices with an increased thickness of the Al top electrode. The bipolar resistive switching behaviors of Al/fuel-assisted NiO _x/ITO devices are therefore discussed based on the formation of conductive paths and their correlation with the Al-electrode modulated composition in the fuel-assisted NiO _x. The Al/NiO _x interfacial reaction region pairs with ITO to form a dual-oxygen-reservoir structure. Mechanisms of construction/destruction of conducting paths originating from the electrochemical redox reactions at the interface between NiO _x, and the dual oxygen reservoirs will also be explicated.