Wind force for adatom electromigration on heterogeneous surfaces

We investigate the variation of the electromigration driving force felt by Na adatoms in the vicinity of other adatoms, adatom rows, and small planar islands. The wind valence tensor is computed by a model calculation for noncompact Na clusters on a semi-infinite flat jellium substrate that carries an electrical current. As an adatom approaches another adatom, atom row, island or a model step edge, the magnitude of the electromigration driving force experienced by an adatom is altered relative to the force felt by an isolated adatom on a large, flat, terrace. This change of the corresponding wind valence is consistent with a model in which the multiple backscattering of carriers between the adatom and the island alters the net momentum transfer between the carriers and the adatom.