Multifunctional double active layers formed with electrochemically controlled nanoparticle dispersion for resistive switching memory arrays

A novel multi-functional active-layer that enables a self-driving resistive random-access memory is achieved by stacking two Cu2O layers having the unique structure of polycrystalline nanoparticles embedded in the amorphous matrix. This active-layer has special characteristics of self-rectifying and self-compliant so that the highest integration density of the crossbar array can be achieved without any additional devices. [Display omitted] •Multifunctional double active layer (DAL) was fabricated by stacking two Cu2O layers with different set voltages.•A stable multi-level (HRS/soft-LRS/full-LRS) was obtained through 2-step breakdown of DAL under forward bias.•Self-rectifying and self-compliance behaviors were achieved by soft-breakdown of upper layer.•4 × 4 crossbar array with DAL showed excellent self-driving characteristics without additional series transistors. Expanding resistive random-access memory (RRAM) from a single device to an array requires a selector to suppress the sneak path and an external device to control the compliance current. Thus, a unique crossbar array that can be independently driven through the novel design of a multilayer RRAM structure with intelligently controlled Cu2O consisting of nanoparticles embedded in the amorphous matrix (ANPs) is proposed. The ANPs–Cu2O active layers are prepared by electrodeposition, and the negative shift of the deposition potential induces a higher density and smaller size of the nanoparticles. The ANPs–Cu2O films show different set voltages and extremely uniform reset voltages, and thus a functional double active layer (DAL) structure consisting of two ANPs–Cu2O layers with different set voltages is proposed. The electrochemically fabricated VCu-controlled DALs effectively protected the reverse current from the self-rectifying characteristics of a large forward/reverse current ratio, thus realizing selector-less RRAMs. In addition, the soft-breakdown showing filament formation in the upper layer reveals the saturation current step acting as a self-compliance current without the assistance of transistors. Finally, a 4 × 4 crossbar DAL RRAM array with transistor-less self-rectification is demonstrated, which shows excellent memory performance and endurance without interfering with adjacent cells.