Spectra of photoluminescence from silicon nanocrystals

The evolution of time-resolved photoluminescence (PL) spectra in Au-doped nanocrystalline silicon films produced by laser ablation has been studied. The PL spectra with a relaxation time of nanoseconds are broad; they lie in the energy range 1.4–3.2 eV with a peak at 2.4–2.8 eV. At the longest times of tens of microseconds, the spectra become narrower, with a peak at 1.6 eV. At intermediate times, two bands are observed: low-energy (1.6 eV) and high-energy, with the peak shifting from 2.7 to 2.1 eV with time increasing. The data are discussed in terms of quantum confinement, dielectric amplification, and manifestation of kinetically coupled electron-hole and exciton subsystems. Ions and atoms of gold passivate dangling bonds on the Si surface and serve as catalysts for the oxidation of nanocrystals. The similarity between recombination processes responsible for the visible PL in oxidized por-Si layers and in the studied Au-doped films is discussed.