Reliable Memristive Switching Memory Devices Enabled by Densely Packed Silver Nanocone Arrays as Electric-Field Concentrators.

Memristor devices based on electrochemical metallization operate through electrochemical formation/dissolution of nanoscale metallic filaments, and they are considered a promising future nonvolatile memory because of their outstanding characteristics over conventional charge-based memories. However, nanoscale conductive paths or filaments precipitated from the redox process of metallic elements are randomly formed inside oxides, resulting in unexpected and stochastic memristive switching parameters including the operating voltage and the resistance state. Here, we present the guided formation of conductive filaments in Ag nanocone/SiO2 nanomesh/Pt memristors fabricated by high-resolution nanotransfer printing. Consequently, the uniformity of the memristive switching behavior is significantly improved by the existence of electric-field concentrator arrays consisting of Ag nanocones embedded in SiO2 nanomesh structures. This selective and controlled filament growth was experimentally supported by analyzing simultaneously the surface morphology and current-mapping results using conductive atomic force microscopy. Moreover, stable multilevel switching operations with four discrete conduction states were achieved by the nanopatterned memristor device, demonstrating its potential in high-density nanoscale memory devices.