The evolution of the structure of quantum size effect Pb nanocrystals on Si(1 1 1) 7×7

We have carried out diffuse X-ray scattering measurements of the growth of Pb nanocrystalline islands on Si(1 1 1). Analysis of our data shows that islands growing on an initially rough wetting layer transforms the portion of the wetting layer below them into ordered fcc sites. Therefore, the islands grow directly on top of the Si surface with a disordered wetting layer occupying the region between the islands and, consequently, the island height responsible for the quantum well depth is one layer thicker than reported by LEED and STM. These islands have an extremely good vertical order until the islands coalesce into a closed film. At that point the disorder of the film increases consistent with misfit strain relaxation.