SURFACE-CONFINED ALLOY FORMATION IN IMMISCIBLE SYSTEMS

Elements which are immiscible in the bulk have been found to form stable two-dimensional mixtures at the free surface. Here we show that such surface-confined mixing is expected quite generally in systems which are dominated by the atomic size mismatch. Mismatch renders the elements immiscible in the bulk, and confines the minority species to the surface, while inhibiting it from segregating within the surface layer. However, a large interface energy will cause clustering within the surface layer. This strain-dominated scenario is consistent with a variety of experimental observations. © 1995 The American Physical Society.