Strained islands as step bunches: shape and growth kinetics

We describe the growth of strained heteroepitaxial islands by the motion of atomic steps forming the island surface. The adatom attachment to a step from the down terrace and the detachment to the up terrace provide the mass transport mechanism to the island top. As the island increases in size, the bulk stress concentration at the island edges and the stress relaxation at the island top lead to steeper island sides and a flatter top. This effect is treated as a primary source for the shape transformation from “pyramids” to “domes”, with subsequent faceting by a slight rearrangement of steps.