Digital versus analog resistive switching depending on the thickness of nickel oxide nanoparticle assembly

Abstract

The thickness-dependent digital versus analog resistive switching of nickel oxide (NiO_x) nanoparticle assemblies was investigated in a Ti/NiO_x/Pt structure. The NiO_x nanoparticles were chemically synthesized with ∼5 nm diameter. The Ti/NiO_x/Pt structure with assembly thickness of ∼60 nm exhibited the digital-type bipolar resistive switching. However, the assembly with a thickness of ∼90 nm presented analog resistive switching with gradually decreasing resistance when sweeping −V while increasing resistance after applying +V. Repeating −V pulses decreased the resistance sequentially, but the high resistance was restored sequentially by repeating +V pulses, which is analogous to the potentiation and depression of adaptive synaptic motion.