Scanning probe microscopy imaging of metallic nanocontacts

TL;DR

This paper uses scanning probe microscopy to study the formation and evolution of metallic nanocontacts during electromigration, revealing detailed structural changes at nanometer resolution.

Contribution

It provides high-resolution imaging of nanocontact formation and details the electromigration process in metallic nanowires fabricated by shadow evaporation.

Findings

Nanocontacts form along grain boundaries initially.

The slit in the nanowire progresses vertically, consuming grains.

Current distribution shifts as the nanowire thins and heats.

Abstract

We show scanning probe microscopy measurements of metallic nanocontacts between controlled electromigration cycles. The nanowires used for the thinning process are fabricated by shadow evaporation. The highest resolution obtained using scanning force microscopy is about 3 nm. During the first few electromigration cycles the overall slit structure of the nanocontact is formed. The slit first passes along grain boundaries and then at a later stage vertically splits grains in the course of consuming them. We find that first the whole wire is heated and later during the thinning process as the slit forms the current runs over several smaller contacts which needs less power.