Memristive Behavior of Mixed Oxide Nanocrystal Assemblies

Recent advances in memristive nanocrystal assemblies leverage controllable colloidal chemistry to induce a broad range of defect-mediated electrochemical reactions, switching phenomena, and modulate active parameters. The sample geometry of virtually all resistive switching studies involves thin film layers comprising monomodal diameter nanocrystals. Here we explore the evolution of bipolar and threshold resistive switching across highly ordered, solution-processed nanoribbon assemblies and mixtures comprising BaZrO₃ (BZO) and SrZrO₃ (SZO) nanocrystals. The effects of nanocrystal size, packing density, and A-site substitution on operating voltage (V_SET and V_TH) and switching mechanism were studied through a systematic comparison of nanoribbon heterogeneity (i.e., BZO-BZO vs BZO-SZO) and monomodal vs bimodal size distributions (i.e., small-small and small-large). Analysis of the current-voltage response confirms that tip-induced, trap-mediated space-charge-limited current and trap-assisted tunneling processes drive the low- and high-resistance states, respectively. Our results demonstrate that both smaller nanocrystals and heavier alkaline earth substitution decrease the onset voltage and improve stability and state retention of monomodal assemblies and bimodal nanocrystal mixtures, thus providing a base correlation that informs fabrication of solution-processed, memristive nanocrystal assemblies.