Electromigration wind force at stepped Al surfaces

When an electrical current flows parallel to a stepped metal surface, each step experiences a force due to momentum transfer from the carriers that are diffusely scattered by the step edge. In this paper, a ballistic model is used to compute the wind force per unit length acting on the steps of vicinal (100) surfaces of Al. The carrier scattering at the surface is described by a potential-barrier model fit to the results of a first-principles calculation of the surface-induced resistivity of the unstepped surface. The magnitude of the wind force is an increasing function of the step terrace width and reaches a constant value as the steps move apart. For an isolated step on a Al(100) surface, the effective wind valence per unit length of the step edge is z(w) similar to - 15e Angstrom(-1). This value is equivalent to a wind valence of z(w) similar to - 43e per atom at the leading edge of each step. [S0163-1829(99)09811-2].