Abstract
Herein we examine the low bias electromigration wind force acting on quasi one-dimensional
nanoscale features within the Landauer-Buttiker conduction picture. Ordinarily the electromigration
force is calculated under the approximation that the non-equilibrium carrier distribution in the
vicinity of a defect is the same as that in the bulk. However, this approximation is rooted in
the assumption that atomic scale defects scatter all incident electrons weakly (just as electrons
weakly and di usely scatter in the bulk). We examine this assumption by calculating the mode
resolved transmission against Ag(111) step edges and atomic wires using density functional theory
(DFT) and the Keldysh non-equilibrium Green's function (NEGF) formalism. Furthermore we
show that those modes that scatter strongly give rise to a non-equilibrium electrochemical potential
drop across a defect and an increased wind force. The results quantitatively explain previously not
understood experimental observations of an enhanced electron wind force against Ag(111) step edges
[O. Bondarchuk et al., Phys. Rev. Lett. 99, 206801 (2007)]. In general, the results underscore the
challenging nanoscale reliability problem posed by surface electromigration in nanosturctures and
the need for a non-equilibrium quantum transport description of the electron wind force.