Impact of Pt embedded nanocrystals on the resistive switching and synaptic properties of forming free TiO_(2-x)/TiO_(2-y)-based bilayer structures

摘要

The resistive switching characteristics of forming free TiO2-x/TiO2-y memory devices containing Pt nanocrystals (NCs) beneath the top electrode were systematically investigated through experiments and numerical simulation insights. By embedding Pt nanocrystals, we have the possibility to narrow down the possible locations where the switching effect will evolve and thus significantly improve the inherent variability of the devices. Besides, the deployment of bilayer structures can tune the resistance levels, since the presence of the layer with low oxygen content (TiO2-y) acts practically as series resistance, limiting the operating currents and at the same time forcing the switching effect to evolve in the layer with the higher oxygen content (TiO2-z). A numerical model is implemented, in order to shed light into the origin of the SET/RESET transitions and illustrate the direct impact of NCs on the conducting filament (CF) shape and distribution of oxygen vacancies. It is demonstrated that a higher density of oxygen vacancies is created in the vicinity of NCs, which can directly impact the operating current values and the uniformity of the switching characteristics. The presence of NCs also facilitates the reduction of the operating voltages (similar to 3V), and, as a result, it significantly improves power consumption, without sacrificing the switching ratio (similar to 10(3)), temporal/spatial variability (sigma/mu0.2), and pulse endurance (10(8) cycles) characteristics of our memory cells. Evidence about the impact of the NCs position within the material configuration are also presented. The direct impact of Pt NCs on the depression and potentiation characteristics of the synaptic weight denotes similarly the huge applicability of our approach to tune a wide range of resistive switching properties.