Deposition of Al onto the Si͑111͒7ϫ7 surface held at temperatures ranging from 475 to 600°C has been found to result in the formation of a superlattice of the identical-size nanoclusters ͑magic clusters͒. The Al magic clusters appear to have the structure similar to that reported recently for the magic clusters of Ga and In on Si͑111͒: each cluster contains six metal atoms linked by three Si atoms. The present results reveal that at the early stages of deposition all the group III metals demonstrate a distinct tendency for the formation of the magic clusters on Si surfaces.

A one-atom-layer compound made of one monolayer of Tl and one-third monolayer of Pb on a Si(111) surface having √3×√3 periodicity was found to exhibit a giant Rashba-type spin splitting of metallic surface-state bands together with two-dimensional superconducting transport properties. Temperature-dependent angle-resolved photoelectron spectroscopy revealed an enhanced electron-phonon coupling for one of the spin-split bands. In situ micro-four-point-probe conductivity measurements with and without magnetic field demonstrated that the (Tl, Pb)/Si(111) system transformed into the superconducting state at 2.25 K, followed by the Berezinskii-Kosterlitz-Thouless mechanism. The 2D Tl-Pb compound on Si(111) is believed to be the prototypical object for prospective studies of intriguing properties of the superconducting 2D system with lifted spin degeneracy, bearing in mind that its composition, atomic and electron band structures, and spin texture are already well established.

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