Electromigration of single-layer clusters

Single-layer atom or vacancy clusters in the presence of electromigration a re studied theoretically assuming an isotropic medium. A variety of distinc tive behaviors distinguish the response in the three standard limiting case s of periphery diffusion (PD), terrace diffusion, and evaporation-condensat ion. A general model provides power laws describing the size dependence of the drift velocity in these limits, consistent with established results in the case of PD. The validity of the widely used quasistatic limit is calcul ated. Atom and vacancy clusters drift in opposite directions in the PD limi t but in the same direction otherwise. In absence of PD, linear stability a nalysis reveals a different type of morphological instability, not leading to island breakdown. For strong electromigration, Monte Carlo simulations s how that clusters then destabilize into slits, in contrast to splitting in the PD limit. Electromigration affects the diffusion coefficient of the clu ster and morphological fluctuations, the latter diverging at the instabilit y threshold. An intrinsic attachment-detachment bias displays the same scal ing signature as PD in the drift velocity.