Self-organized two-dimensional lattice of magic clusters
M. Y. Lai and Y. L. Wang
Phys. Rev. B 64, 241404(R) (2001)

Under certain deposition conditions, gallium induces almost exclusive formation of a type of especially stable clusters—magic clusters, on the 7x7-reconstructed silicon(111) surface. The cluster has a triangular closed-shell structure and resides on the center of a 7x7 half unit-cell. As the gallium coverage is increased, the cluster density increases proportionally, leading essentially to the complete filling of the 7x7 half unit cells and the creation of an unprecedented two-dimensional lattice of magic clusters. A structure model employing three silicon atoms to link six gallium atoms into a configuration with satisfied bonding is proposed to account for the cluster’s stability.