Magic nanoclusters of group III metals on Si(100) surface

Abstract

Using scanning tunneling microscopy observations, the ability of group III metals, In, Al, Ga and Tl, to form identical-size magic nanoclusters upon high-temperature adsorption on Si(100) has been examined. Magic clustering has been detected in In/Si(100) and Al/Si(100) systems. In both cases, atomic structure of the nanocluster is plausibly described by the model of Bunk et al. [Appl.Surf.Sci. 123/124, 104 (1998)], in which six metal atoms and seven Si atoms form a stable pyramid-like cluster. In the case of In/Si(100) system, the perfectly-ordered 4×3 superlattice built of magic nanoclusters can be formed. The Al/Si(100) nanoclusters has been found to form local arrays with a 4×5 periodicity. In Ga/Si(100) and Tl/Si(100) systems, no indication of magic clustering has been detected. The criteria for magic cluster formation are discussed.

Peculiarities of Al magic cluster self-assembly on Si(1 0 0) surface

“…Table 1 illustrates the bias-dependent STM appearance of the single In and Al clusters formed on Si(1 0 0)2 Â 1 surface. In agreement with the previous publications [1,17,22], STM appearance of the clusters are qualitatively similar: namely, both clusters show up as a single round-shaped protrusion in the filled-state images, as three oval protrusions in the empty-state images at +1.0 V sample bias and as a pair of oval protrusions in the empty-state images at +2.0 V. Similarity of the STM appearance was proved to be a sequence of the similar atomic arrangement. Results of the first-principles total-energy calculations [36][37][38], STM image simulation [37] and ion scattering spectroscopy analysis [39] confirmed a structural similarity of the In and Al clusters, both being described by the model proposed initially by Bunk et al [35] for the In/ Si(1 0 0) cluster.…”

“…Why does Al-cluster array have the 4  5 periodicity [21,22], while a single Al cluster occupies the 4a  3a area [22][23][24]? [a = 3.84 Å, the lattice constant of the unreconstructed Si(1 0 0)1  1 surface.]…”

Emergence of state at Fermi level due to the formation of In-Sn heterodimers on Si(100)-2×1

“…Above 250 • C, In reacts with Si atoms and forms "magic" In-Si islands. 25 Our goal was to prepare relaxed structures and reduce the role of kinetics as much as possible. Therefore we have focused on a deposition temperature of 200 • C and a deposition rate of 0.005 ML/s.…”

Nonmetallic nature ofIn-induced nanoclusters onSi(100)

“…9,10 On the silicon surfaces, while most of the nanoclusters have been found to be insulating, it is remarkable that a certain In nanocluster was reported very recently to be metallized on Si͑100͒. 10 The metallic nanoclusters are based on the In-induced cluster array in a 4 ϫ 3 long-range order, which is formed on Si͑100͒ with 0.5 ML In and a moderate annealing [the so-called Si͑100͒4 ϫ 3-In surface].…”

“…The spontaneous self-assembly is one of the most promising processes, for such positioning and ordering especially over a macroscopic scale. 4,5,[7][8][9][10] In particular, various nanoclusters have been successfully prepared on solid surfaces by the spontaneous self-assembly such as Cu on Pt(111), 5 Si 1-x Ge x on Si͑100͒, 4 In on Si͑111͒7 ϫ 7, 6,7 Ga on Si͑111͒ ͱ 3 ϫ ͱ 3R30°-Ga, 8 …”