Nanoclusters of Group-III Metal Atoms on Si(111)-7 x 7

The realization of perfectly ordered clusters has been achieved recently for various adsorbates using appropriate substrates such as Si(111)-7 x 7, which has great potential for future nanotechnology applications. In this article, we review the recent experimental and theoretical studies on surface magic clusters (SMCs) formed on Si(111)-7 x 7, focusing on Group III SMCs as a testing ground for an understanding of the underlying chemical and physical mechanisms. Although the atomic geometrical structures of the Al, Ga, and In clusters have been found to be identical, the Thallium cluster, formed at room temperature, is intriguing, complicated mostly by Tl atom's mobile nature. Exploiting accurate ab initio studies, we elucidate the mechanism of SMC formation for the Al, Ga, and In clusters. We also show the Tl cluster's favorable structure and origin, and estimate the hopping frequency of Tl adatoms.