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By means of in situ high-temperature scanning tunnelling microscopy (STM), the thermal stability of highly ordered artificial Al nanocluster arrays, so-called two-dimensional nanocluster crystals, on vicinal Si (111)-7 × 7 surfaces has been investigated. It was found that Al nanocluster crystals are stable below 500 °C. Above 500 °C, the Al nanocluster crystal transforms into a surface phase with singular triangle shapes on down-terraces (the down-step side of a terrace). However, on up-terraces (the up-step side of a terrace), Al nanoclusters can move on Si (111)-7 × 7 surfaces over a large distance and the Al nanocluster crystal retracts toward the phase until the bare Si (111)-7 × 7 surface is completely recovered on up-terraces. The thermally activated motion of Al nanoclusters was not observed apparently below 400 °C, though Al nanocluster crystals can be formed even at 200 °C. This indicates that it is atom diffusion, not cluster diffusion, which is responsible for the formation process of metal cluster crystals on Si (111)-7 × 7 surfaces.

1D indium islands have been formed by epitaxial growth on a self-assembled template. The templates are formed from Bi nanolines, which are 1.5 nm wide, and can be over 500 nm in length. The islands conform to the template width and are over 100 nm long. The first layer of the island forms a novel chain structure of In and Bi atoms, which accounts for the epitaxial growth of the nanocrystals on the template. The second layer shows a hexagonal structure 19 A or 2.5 dimer rows wide. Epitaxial growth saturates after two layers of In have been deposited. With further deposition, a transition to the growth of 3D In droplets is observed.

A recent article (Miwa et al 2005 Nanotechnology 16 2427) casts doubt on the four-dimer-wide Haiku model for the Bi nanoline on Si(001), suggesting instead that the three-dimer-wide Miki model (which had been ruled out) is a better fit in particular to x-ray data. The reasons why the Haiku model provides the best fit to all published data among currently proposed structures are discussed, concentrating on the width and registry of the Bi nanoline, and mentioning new data which shows that under appropriate conditions the two structures coexist in the same surface.