Transparent and Flexible Nanowire-based Memristive Devices

Description

In recent years, as demanded by consumers aiming for enhanced device performance and bettermobile experience, the mobile device technology has been progressed at unbelievably fast pace,driving the memory chips with higher performance and smaller form factor. Unfortunately, bysimply down-scaling the memory cells with the faster programming speed and lower powerconsumption are not enough to provide the improved mobile experience that consumers need.Moreover, due to the increasing penetration of touch-based devices in consumer electronics, theemergence of miniaturized personal electronics would lead to the quest of compact, transparentand flexible systems. In this regard, to date, significant amount of work have been focused on thedevelopment of transparent and flexible memristive (resistive random-access memory, RRAM)devices, employing metal-oxide thin-films as the active channel materials and transparentconductive oxide (TCO) as the electrodes for the next-generation memory technology. Althoughthe obtained switching characteristics are far better than other competing technologies, as allthese thin-film devices still require lithography for the pattern definition, it would be extremelydifficult to achieve cell dimensions beyond the limits of lithography for the continued scalability.At the same time, because of the advent of nanotechnology, highly crystalline metal-oxidenanomaterials such as nanowires (NWs) have been utilized as promising functional blocks forfuture transparent and flexible memory devices owing to their extremely small dimensions,excellent mechanical flexibility, well-established cost-effective synthesis schemes, easymodulation of material properties and more importantly allowing one to fully exploit the scalingpotential of devices. For instance, these crystalline NWs can be readily grown on lattice-mismatchedor even amorphous substrates, and hence enabling the transfer of NWs ontotransparent and flexible substrates for the subsequent device fabrication. Also, as compared withconventional amorphous or polycrystalline thin-film based devices, this crystalline nature ofNWs can significantly improve their fabricated memristive device properties, since less grainboundaries are present to negatively impact the switching performance. Even so, there are stillmany significant challenges in controlling the NW synthesis, understanding their fundamentalproperties, integrating these high-quality NWs into transparent and flexible RRAM devices, andevaluating their corresponding performance and reliability. In this proposal, we will concentrateon the ternary In2xGa2?2xO3 NWs as the active device channels, attributable to their excellentcrystallinity, chemical, electrical and thermal stability, and superior resistive switchingperformance as demonstrated in devices configured with their thin-film counterparts. The targetis to assess their performance limits with further optimization in the NW channel stoichiometryand dimension, electrode composition, device structure, and memory operation scheme. In theend, we plan to establish relevant design guidelines based on metal-oxide NWs, to go beyond theconventional thin-film technologies, for the future memory circuit implementation.