Bulk and Surface Nucleation Processes in Ag2S Conductance Switches

TL;DR

This paper investigates the mechanisms of Ag nucleation in Ag2S thin films under electric fields, distinguishing surface cluster formation at low bias from full conductance switching at higher bias, and proposes a model for these processes.

Contribution

It introduces a model for Ag cluster formation at low bias and analyzes the transition to conductance switching, enhancing understanding of memristive device mechanisms.

Findings

Cluster formation occurs at low bias voltages.

Conductance switching happens at bias > 70mV.

Cluster growth depends on STM tip geometry.

Abstract

We studied metallic Ag formation inside and on the surface of Ag2S thin films, induced by the electric field created with a STM tip. Two clear regimes were observed: cluster formation on the surface at low bias voltages, and full conductance switching at higher bias voltages (V > 70mV). The bias voltage at which this transition is observed is in agreement with the known threshold voltage for conductance switching at room temperature. We propose a model for the cluster formation at low bias voltage. Scaling of the measured data with the proposed model indicates that the process takes place near steady state, but depends on the STM tip geometry. The growth of the clusters is confirmed by tip retraction measurements and topography scans. This study provides improved understanding of the physical mechanisms that drive conductance switching in solid electrolyte memristive devices.