Dynamic behavior and phase transition of magic Al clusters on Si(111)-7×7 surfaces

Abstract

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Al nanocluster arrays onSi(111)−7×7surfaces: Formation process and interactions among clusters

“…In our previous studies, 17,18 the dynamic behavior of Al magic clusters on the Si͑111͒-7 ϫ 7 surface at high temperature has been investigated by variable-temperature STM. It was found that fast diffusion of magic Al clusters occurs above 500°C, with an activation energy of 2.0± 0.3 eV, together with the decomposition of the clusters into the ͱ3 ϫ ͱ 3-Al phase.…”

Trimeric precursors in formation of Al magic clusters on a Si(111)-7×7surface

“…Recently, surface-mediated magic clustering was employed as the building blocks for identicalsized nanostructures, and the results demonstrated that the fabrication of artificial cluster crystals is possible. [4][5][6][7][8][9][10][11][12][13][14][15] While the fabrication of precise surface nanostructures has made exciting progress, the formation mechanism for this kind of surface magic cluster is still poorly understood, partly because of the complexity of the process from formation to detection. Recent experiments using a variable-temperature scanning tunneling microscope (STM) have given an unprecedented view of epitaxial nucleation and island growth.…”

“…6,7 Our previous studies reported the thermal stability of Al magic cluster arrays and the interaction between arrays. [13][14][15] It was found that the Al magic cluster arrays are stable up to 500 • C, transforming into a ( √ 3 × √ 3)-Al phase above 500 • C. From the activation energy of the Al magic cluster, it was concluded that Al atoms congregate to form the Al magic cluster arrays through a single-atom diffusion process, rather than through a cluster diffusion process. An attractive interaction was found between the Al magic clusters, which is responsible for the honeycomb structure.…”

Novel Evolution Process of Zn-Induced Nanoclusters on Si(111)-(7×7) Surface

“…It was found that the atomic structures of these identical-sized nanoclusters had a characteristic of the varying valence. For instance, group IIIA metals (Al, Ga, and In) tend to form the stable Al 6 Si 3 , Ga 6 Si 3 , and In 6 Si 3 nanoclusters with six metal atoms and three displaced Si edge adatoms connecting as a hollow triangle [15][16][17][18][19][20]. However, group IIB metal, Zn, tends to form the stable Zn 7 Si 3 nanoclusters with an excess Zn atom characteristically occupying the center of the hollow triangle [14].…”

“…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.…”