Surface electromigration is observed in both homo- and heterosystems. In the case of homo-electromigration, the change in the current direction changes the surface morphology, in particular, the step structure. In case of hetero-electromigration, adsorbate mass transfer occurs mainly in the direction of one of the electrodes (anode or cathode).

In the formal description of surface electromigration, the effective force acting on the atom migrating on the surface is proportional to the electric field , and is written as a sum of two components:



where is the direct force acting on the atom (ion) due to its electrostatic interaction with the applied field; is the electron wind force created by the momentum transfer from charge carriers (electrons) as they are scattered off the atom; is the total effective charge of the atom measured in units of electron charge .

The force of the electron wind is predominant for the electromigration of atoms adsorbed on metal surfaces, so the direction of motion of the adatoms (which are not yet built into the atomic lattice) coincides with the direction of flow of electrons towards the anode. Electromigration on semiconductor surfaces, as the case may be, may be of either negative or positive sign . For example, silver or indium atoms on the surface of silicon migrate toward the cathode, while gold atoms on the same surface move toward the anode.