In this way, the complexity of the competition between what is energetically favorable and what is kinetically likely is more fully appreciated. Here, we focus on the smallest island that has rebonded step edges on both ends, as is characteristic of epitaxial rows. This island consists of three dimers, one on top of a dimer row and one in each of the two adjacent trough sites. Once growth has proceeded through the first six atoms to form this type of an island, the island can then serve as a seed for further growth by the addition of four atom units at either end. The tie structure is then observed to grow to a six-atom island, with the addition of two atoms.
Red circles represent adatoms on the surface.
Lines are drawn to indicate the electronic bonds. Segments of four substrate dimer rows are shown in the figure, running vertically. These single dimer configurations are important in describing and understanding the structures involved in epitaxial island formation. Configuration A is lowest in energy and is in epitaxial orientation. Figure 2 shows filled and empty state images of the structures important in the observed epitaxial island formation process.