Electromigration in β-Sn exhibited a 10% drop in resistance due to the anisotropic properties of the material. The drop was proposed to be due to the reorientation of grains to reduce the resistance. The driving force, and the atomic mechanism of grain rotation under electromigration, were considered here. It was proposed that the anisotropic resistivity caused divergence of the vacancy fluxes at the grain boundaries and induced vacancy fluxes to/from the free surface, along the grain boundary. The vacancy gradients along the grain boundaries corresponded to the gradients of stress. The opposite sign of the stress along grain boundaries generated a torque which led to rotation of the grain by grain-boundary diffusion or creep. The rate of rotation, estimated on the base of this model, seemed to agree well with observed experimental data.

Electromigration-Induced Grain Rotation in Anisotropic Conducting Beta Tin. A.T.Wu, A.M.Gusak, K.N.Tu, C.R.Kao: Applied Physics Letters, 2005, 86[24], 241902 (3pp)