Silicon nanocrystals produced by adiabatic expansion of silicon vapor: emergence of body-centered cubic silicon nanocrystals

Silicon (Si) nanocrystals with diameters of 2–5 nm were produced through non-equilibrium condensation of Si vapor. Electron diffraction analysis indicated that the nanocrystals formed a bcc structure with eight atoms per primitive cell (BC-8). The optical bandgap energy of the nanocrystals was about 1.6 eV, and photoluminescence was observed in the region of the bandgap energy. The obtained energy is compared with a theoretically predicted value of the BC-8 Si crystal of the present size.