A Current Induced Transition in atomic-sized contacts of metallic Alloys

TL;DR

This study investigates how the conductance properties of atomic-sized metallic alloy contacts change with bias voltage, revealing a bias-induced transition in their atomic composition likely due to electromigration or diffusion effects.

Contribution

It provides the first experimental evidence of bias-induced compositional changes in atomic-sized alloy contacts and discusses potential mechanisms behind this transition.

Findings

Conductance histograms shift from noble metal-like to transition metal-like at high bias.

The transition occurs above 300 mV bias voltage.

Electromigration and differential diffusion are proposed as possible explanations.

Abstract

We have measured conductance histograms of atomic point contacts made from the noble-transition metal alloys CuNi, AgPd, and AuPt for a concentration ratio of 1:1. For all alloys these histograms at low bias voltage (below 300 mV) resemble those of the noble metals whereas at high bias (above 300 mV) they resemble those of the transition metals. We interpret this effect as a change in the composition of the point contact with bias voltage. We discuss possible explanations in terms of electromigration and differential diffusion induced by current heating.