Strong radial electric field scaling near nanoscale conductive filaments and the ReRAM resistive switching mechanism

TL;DR

This paper reveals that nanoscale surface charge effects induce strong radial electric fields in conductive filaments, explaining the resistive switching mechanism in ReRAM devices and resolving longstanding controversies in the field.

Contribution

It introduces a nanoscale surface charge effect that explains the reset mechanism in filamentary memristors, reconciling previous conflicting theories and experimental data.

Findings

Radial electric fields can reach 10^5 to 10^6 V/cm at -1 V bias.

Nanoscale surface charge effects are key to resistive switching.

The proposed model explains previously conflicting experimental observations.

Abstract

The physics underlying reset in bipolar resistive memory has been the subject of decades of controversy and has been identified as the primary barrier to resistive memory technology development. This manuscript introduces a nanoscale effect in current carrying conductors, whereby surface charge induced radial electric fields are found to be inversely proportional to the radius of the conductive path. This nanoscale effect is then applied to explain the negative resistance switching (reset) mechanism in filamentary metal oxide resistive switching memory devices (memristors). Previous explanations for the negative resistive switching mechanism state that diffusion constitutes the radial driving mechanism for oxygen ions, and drift under electric fields is restricted to the direction parallel to current flow. This explanation conflicts with retention and microscopy data collected in a subset of devices presented in literature. We demonstrate that the electric field's dependency on the on the radius of a nanoscale conductive path can result in radial fields on the order of 10^5 to 10^6 V/cm at only -1 V bias, sufficient to govern the negative resistance switching mechanism in filamentary metal oxides. By accounting for this nanoscale size effect, long standing anomalous experimental data about the negative (reset) resistance switching mechanism in bipolar filamentary resistive memory devices is finally reconciled. Wide understanding of surface charges and associated electric fields in nanoscale conductive paths could prove important for further scaling of integrated circuits and aid in elucidating many nanoscale phenomena.