Nanocrystalline-silicon superlattice produced by controlled recrystallization

Nanocrystalline-silicon superlattices are produced by controlled recrystallization of amorphous-${\mathrm{Si/SiO}}_{\mathrm{2}}$ multilayers. The recrystallization is performed by a two-step procedure: rapid thermal annealing at 600–1000 °C, and furnace annealing at 1050 °C. Transmission electron microscopy, Raman scattering, x-ray and electron diffraction, and photoluminescence spectroscopy show an ordered structure with Si nanocrystals confined between ${\mathrm{SiO}}_{\mathrm{2}}$ layers. The size of the Si nanocrystals is limited by the thickness of the $a$ -Si layer, the shape is nearly spherical, and the orientation is random. The luminescence from the $\mathrm{nc}$ -Si superlattices is demonstrated and studied.