Directed Assembly of Nanoparticle Threshold-Selector Arrays

The directed assembly of ordered arrays of cubic silver nanoparticles featuring distinct electrical threshold-switching characteristics is reported. Threshold selectors are key elements for nonvolatile resistive random-access-memory architectures, as they suppress sneak path currents in crosspoint arrays. Nanocubes are site-selectively immobilized on a TiO₂-coated silicon surface via a complementary molecular surface functionalization of nanoparticles and substrate based on a Cu(I)-catalyzed alkyne-azide cycloaddition without any physical template. Electrical characterization of individual silver nanocubes by conductive-probe atomic force microscopy reveals pronounced and reproducible threshold-switching behavior, featuring ultralow OFF currents below 1 pA, steep turn-on slopes of <50 mV dec⁻¹ and ON-OFF ratios in excess of 10³. Numerical simulation of Ag-ion migration dynamics in the TiO₂ electrolyte using a kinetic Monte Carlo model supports a switching mechanism based on conductive filament formation from Ag nanoclusters, and their reversible rupture in the low-voltage regime. Assembled Ag nanocube threshold selectors are proposed for applications in memristive memory architectures, in particular for future highly integrated 3D circuitry.