Figure 1
From: Electrolithography- A New and Versatile Process for Nano Patterning

Electromigration induced radially symmetric flow.
(a) Schematic illustration of the experimental setup for passing electric current through a thin Cr film deposited on a substrate. (b) An optical image showing formation of a typical electromigration ring around the cathode probe (solid black parts are needle probes). The ring is created on a 20 nm Cr film deposited on SiO2-Si substrate (Refer to Supporting Information for the video attached to this figure showing real time flow process).