Memristor Kinetics and Diffusion Characteristics for Mixed Anionic‐Electronic SrTiO_3‐δ Bits: The Memristor‐Based Cottrell Analysis Connecting Material to Device Performance

Abstract

Memristors based on mixed anionic‐electronic conducting oxides are promising devices for future data storage and information technology with applications such as non‐volatile memory or neuromorphic computing. Unlike transistors solely operating on electronic carriers, these memristors rely, in their switch characteristics, on defect kinetics of both oxygen vacancies and electronic carriers through a valence change mechanism. Here, Pt|SrTiO3‐δ|Pt structures are fabricated as a model material in terms of its mixed defects which show stable resistive switching. To date, experimental proof for memristance is characterized in hysteretic current–voltage profiles; however, the mixed anionic‐electronic defect kinetics that can describe the material characteristics in the dynamic resistive switching are still missing. It is shown that chronoamperometry and bias‐dependent resistive measurements are powerful methods to gain complimentary insights into material‐dependent diffusion characteristics of memristors. For example, capacitive, memristive and limiting currents towards the equilibrium state can successfully be separated. The memristor‐based Cottrell analysis is proposed to study diffusion kinetics for mixed conducting memristor materials. It is found that oxygen diffusion coefficients increase up to 3 × 10–15 m2s–1 for applied bias up to 3.8 V for SrTiO3‐δ memristors. These newly accessible diffusion characteristics allow for improving materials and implicate field strength requirements to optimize operation towards enhanced performance metrics for valence change memristors.

How Does Moisture Affect the Physical Property of Memristance for Anionic–Electronic Resistive Switching Memories?

“…Based on this experimental evidence we deduced that the capacitive contributions are not linked to the resistive switching mechanism itself. The capacitive contributions fit well with our earlier reported chronoamperometry results and the suggested equivalent circuit models a memristor in parallel with a capacitor for such devices …”

Design of Oxygen Vacancy Configuration for Memristive Systems

“…By increasing the cycling speed from 250 mV/s to 1 V/s, the resistance ratio decreases by approximately a factor of 5. Similar behavior was observed for Pt–SrTiO 3 –Pt devices . Importantly, the resistance × area of our devices is independent of the electrode area for both the high and low resistive state (Figure d).…”

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

“…The diffusion coefficient for the VCM Pt/SrTiO 3-𝛿(600 nm) /Pt cell [28] was determined to be 2.19 × 10 −14 cm −2 s −1 , consistent with values reported in the literature on oxygen vacancies diffusion in SrTiO 3 . [30] For the ECM Cu/Ta 2 O 5(15 nm) /Pt cell, [17] the calculated diffusivity is 1.94 × 10 −18 cm −2 s −1 , with a magnitude similar to that measured by ion mass spectroscopy for nano-thick Ta 2 O 5 .…”