In situ atomic force microscopy imaging of structural changes in metal nanowires during feedback-controlled electromigration

Abstract

The authors present the real-time atomic force microscopy (AFM) imaging of structural changes in gold (Au) nanowires during the feedback-controlled electromigration (FCE) process. The resistance increases during the FCE process and is associated with drastic changes in the nanowire morphology, suggesting successful control of electromigration (EM) through the FCE scheme. Moreover, the AFM images taken after performing FCE indicate a redeposition of matter along the nanowire in the direction of the anode side. The grains show faceting structures at the anode side. Furthermore, to obtain quantitative information on the height of structures, cross-sections of the nanowire obtained from the AFM images during FCE were investigated. The height evolution of the narrowest part of the wire perpendicular to the electron flow was obtained, showing that void nucleation and void growth along the grain boundaries, which are located on the border of the nanowire, start in the vicinity of the nanowire constriction at the cathode side. Furthermore, a maximum relative mass transport value of 19% and a mass transport rate of 106 atoms/s were found. These results imply that the in situ AFM technique provides insight into the behavior of EM-induced voids in metal nanowires during FCE.