A Voltage-Driven Transport Model to Identify Ion Migration as the Rate-Limiting Step in Memristive Switching

Abstract

The physics behind the switching kinetics of memristors is gradually becoming clearer. The periods required for the onset of electromigration within memristors and the activation or deactivation of the low-resistance state—referred to as the incubation and switching times—exhibit non-linearity with applied voltage. This behavior prevails depending on the rate-limiting step comprising nucleation and filament growth, electron transfer at the electrode/electrolyte interface, and ion migration through the electrolyte. Herein, a model is introduced for ion migration as the rate-limiting step. This model analyses the incubation time and analytically correlates it with the electric field, diffusion coefficient, and temperature, facilitating the determination of threshold voltage and diffusivity from high to low resistance states for ion migration as the rate-limiting step. By exploring parallel plate cells with Yttria-Stabilized Zirconia (YSZ) of nanometer thickness, the application of the model is illustrated and the fundamental equations are applied to outstanding memristive cells in the literature. The applicability of this model to cells of various charge carriers is proposed, ranging from vacancies and electron transport to oxygen ions and metal cations, denoting its potential importance.