MOMENTUM-BALANCE CONSIDERATIONS IN ELECTROMIGRATION REVISITED

In the past, momentum-balance considerations in electromigration have been put forward in support of different results for the magnitude of the direct force on an interstitial impurity. The result based on such considerations is shown to allow for different interpretations if one treats a system containing one single impurity or a finite density of randomly distributed impurities. In view of a recent exact derivation of the magnitude of the driving force it becomes clear why the result for the one-impurity case may lead to a reliable interpretation. For the impurity density result two different contradictory interpretations are available in the literature. However, in the interpretation, which leads to an unscreened direct force, all local information about the electronic structure at the impurity is shown to be lost. In examining the exact result, derived in a new and concise way, it is made clear also that the available weak-charge limit results are unreliable in deciding about the magnitude of the direct force. © 1990.