Electric field and potential around localized scatterers in thin metal films studied by scanning tunneling potentiometry

TL;DR

This study uses scanning tunneling potentiometry to directly observe electric potential and field variations near local scatterers in thin platinum films, revealing significant local field enhancements that influence electromigration failure.

Contribution

It provides the first direct measurements of local electric fields around scatterers in thin metal films, highlighting the impact of grain connectivity on local field build-up.

Findings

Maximum local field at voids exceeds macroscopic field by four orders of magnitude.

Void regions are the most probable sites for electromigration failure.

Local field variations depend on grain boundary reflection coefficient.

Abstract

Direct observation of electric potential and field variation near local scatterers like grain boundaries, triple points and voids in thin platinum films studied by scanning tunneling potentiometry is presented. The field is highest at a void, followed by a triple point and a grain boundary. The local field near a void can even be four orders of magnitude higher than the macroscopic field. This indicates that the void is the most likely place for an electromigration induced failure. The field build up near a scatterer strongly depends on the grain connectivity which is quantified by the average grain boundary reflection coefficient, estimated from the resistivity.