Structural and electronic properties of identical-sized Zn nanoclusters grown on Si(111)-(7x7) surfaces

Identical-sized Zn nanoclusters have been grown on Si(111)-(7x7) surfaces at room temperature. In situ scanning tunneling microscopy (STM) studies and first-principles total energy calculations show that room-temperature grown Zn nanoclusters tend to form the seven-Zn-atom structure with one excess Zn atom occupying characteristically the center of the cluster. The evolution of the surface electronic structures measured by scanning tunneling spectroscopy reveals that the formation of Zn nanoclusters is responsible for the saturation of the metallic Si adatom dangling bond states at about -0.3 and +0.5 V and causes the semiconducting characteristics of the nanoclusters. Furthermore, the Zn nanocluster in a faulted half unit cell empties the filled surface dangling bond state of the closest edge Si adatoms in the nearest neighboring uncovered unfaulted half unit cells at about -0.3 V, leading to the suppressed height of the closest edge Si adatoms in the filled-state STM images.