Quantum confinement in nanometer-sized silicon crystallites

Picosecond decay and temperature-dependence measurements of violet and blue-light emissions from nanocrystalline-silicon thin films were carried out. The luminescence band exhibits separated peaks at a wavelength region from 350 to 500 nm and shows no intensity degradation. The emission energies of the peaks shift towards the high-energy side at low temperatures by a temperature coefficient similar to single-crystalline silicon. The photoluminescence decays of these emissions can be completely fitted by a double-exponential equation. The two components of the lifetime ${\mathrm{\tau }}_1$ and ${\mathrm{\tau }}_2$ determined from the decay curves are 170 and 600 ps, respectively. All the optical events finish within 5 ns. The short lifetimes are suggested to be caused by an enhancement effect on the oscillator strength of the confined levels in zero-dimensionally confined silicon nanometer-sized crystallites.