Pyramid-like nanostructures created by Si homoepitaxy on Si(0 0 1)

We report on the formation of different arrays of pyramid-like Si nanostructures at the onset of silicon homoepitaxial growth. Such nano-objects are observed to reproducibly develop in Si films grown by molecular beam epitaxy on HF-treated Si(0 0 1) substrates, for a narrow set of growth conditions. A rich variety of surface morphologies (from pyramidal island arrays to square pit distributions) is found depending on film thickness and substrate temperature. These arrangements of nano-scale entities (islands or pits) display certain self-assembly and ordering features (concerning size, shape and spacing) with interesting similarities to other homoepitaxial and heteroepitaxial material systems.