Abstract
A tiny number of Zn atoms were deposited on Si(111)-(7×7) surface to study the evolution process of Zn-induced nanoclusters. After the deposition, three types (type I, II, and III) of Zn-induced nanoclusters were observed to occupy preferably in the faulted half-unit cells. These Zn-induced nanoclusters are found to be related to one, two, and three displaced Si edge adatoms, and simultaneously cause the depression of one, two, and three closest Si edge adatoms in the neighboring unfaulted half-unit cells at negative voltages, respectively. First-principles adsorption energy calculations show that the observed type I, II, and III nanoclusters can reasonably be assigned as the Zn3Si1, Zn5Si2, and Zn7Si3 clusters, respectively. And Zn3Si1, Zn5Si2, and Zn7Si3 clusters are, respectively, the most stable structures in cases of one, two, and three displaced Si edge adatoms. Based on the above energy-preferred models, the simulated bias-dependent STM images are all well consistent with the experimental observations. Therefore, the most stable Zn7Si3 nanoclusters adsorbed on the Si(111)-(7×7) surface should grow up on the base of Zn3Si1 and Zn5Si2 clusters. A novel evolution process from Zn3Si1 to Zn5Si2, and finally to Zn7Si3 nanocluster is unveiled.
Highlights
Design and fabrication of nanoclusters is a new inspiring field because of their amazing features that are remarkably different from classical materials [1,2,3,4]
A tiny number of Zn atoms were deposited on Si(111)-(797) surface to study the evolution process of Zninduced nanoclusters
For the filled-state scanning tunneling microscopy (STM) images of type I nanoclusters, as shown in Fig. 1b, it seems that one Si edge adatom is pushed toward the center of the faulted half-unit cells (FHUCs)
Summary
Design and fabrication of nanoclusters is a new inspiring field because of their amazing features that are remarkably different from classical materials [1,2,3,4]. From the viewpoint of practical applications, it is necessary to fabricate stable, ordered, and identical-sized nanoclusters. In the past decade, utilizing the natural template of Si(111)-(797) surface, a number of metal nanoclusters with identical sizes and shapes have been successfully fabricated, such as group IA metals (Na) [11, 12], group IB metals (Au) [13], group IIB metals (Zn) [14], group IIIA metals (Al, Ga, Tl, and In) [15,16,17,18,19,20], group IV metals (Pb) [21], and even some 3d ferromagnetic metals (Fe, Co, and Ni) [22,23,24]. By using the ultrahigh-vacuum (UHV) scanning tunneling microscopy (STM) technology combined with the first-principle theoretical simulations, the stable structural configurations of the identical-sized nanoclusters on Si(111)-(797) surface have been clearly illustrated. Group IIIA metals (Al, Ga, and In) tend to form the stable Al6Si3, Ga6Si3, and In6Si3 nanoclusters with six metal atoms and three displaced Si
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