Internal structure refinement of porous sintered silver via electromigration

Atoms can move under high stress conditions such as temperature, mechanical pressure or electric current. Electromigration provides a driving force to move the atoms in metals conducting current usually resulting in the accumulation of atoms and void formation in anode and cathode respectively. The electromigration effect is normally considered a serious problem for electronic circuits but the recent works^1-7 show that it can be used constructively for controlled fabrication of nanostructures^2-4.We demonstrate that electromigration can be utilized to refine the porous structure of a sintered silver stripe leading to transformation of the internal pore and grain structure. The results show that pore shape, size and distribution are significantly changed after electromigration. Similarly, we have used the electromigration effect to mass produce nanorods under current densities of the order of 2.4 ×10⁺⁸ A/m². Nanorods were formed across the whole stripe contrasting with studies on non-porous substrates which show nanorod production at the anode only. The results show the internal pore structure can be transformed and refined by electromigration. The results also suggest that by controlling current densities in a porous substrate, complex patterns of porous structures and high-quality single crystal nanorods can be formed insitu with significant advantages over competing methods of nanorod formation for sensor applications.