Low-cost fabrication and polar-dependent switching uniformity of memory devices using alumina interfacial layer and Ag nanoparticle monolayer

摘要

A facile and low-cost process was developed for fabricating write-once-read-manytimes(WORM) Cu/Ag NPs/Alumina/Al memory devices, where the alumina passivationlayer formed naturally in air at room temperature, whereas the Ag nanoparticlemonolayer was in situ prepared through thermal annealing of a 4.5 nm Ag film inair at 150 C. The devices exhibit irreversible transition from initial high resistance(OFF) state to low resistance (ON) state, with ON/OFF ratio of 107, indicating theintroduction of Ag nanoparticle monolayer greatly improves ON/OFF ratio by fourorders of magnitude. The uniformity of threshold voltages exhibits a polar-dependentbehavior, and a narrowrange of threshold voltages of 0.40Vamong individual deviceswas achieved upon the forward voltage. The memory device can be regarded as twoswitching units connected in series. The uniform alumina interfacial layer and the nonuniformdistribution of local electric fields originated from Ag nanoparticles mightbe responsible for excellent switching uniformity. Since silver ions in active layer canact as fast ion conductor, a plausible mechanism relating to the formation of filamentssequentially among the two switching units connected in series is suggested for thepolar-dependent switching behavior. Furthermore, we demonstrate both alumina layerand Ag NPs monolayer play essential roles in improving switching parameters basedon comparative experiments. ? 2017 Author(s). All article content, except where otherwisenoted, is licensed under a Creative Commons Attribution (CC BY) license.