Papers by Keyword: Visible Photoluminescence

Abstract: Hydrogenated Si nanocrystals were performed by high-dose (51017 cm-2) low-energy (24 keV) H+ ion implantation of silicon-on-insulator (SOI) layers. The formation of the nanocrystalline phase was observed in the as-implanted samples and in those annealed at the temperature of 200-400o C. Both the Raman shift and the broadening of the phonon peak corresponded to Si nanocrystals with the diameters ranging from ~2 to ~3 nm. The room-temperature photoluminescence (PL) peaked at 1.58 - 1.64 eV was observed at room temperature. The PL peak energy corresponded to the energy of quantum confined exciton in the Si nanocrystals with the diameters mentioned above. The PL intensity had the bell-shaped dependence on the measurement temperature and had its maximum near 150 K. The estimated thermal activation energy of the PL was about 12.1 meV and was in good accordance with the singlet-triplet splitting energy of the exciton states.

Abstract: Stoichiometric mercury-telluride (HgTe) nanocrystals, free from any foreign impurities, have been prepared by an electrochemical technique. Transmission electron microscopy and selected area diffraction studies confirm that the size of HgTe nanocrystals with cubic phase range from 4 – 7 nm and are preferentially oriented. Optical absorption studies indicate that the band gap of HgTe nanocrystals is 2.14 eV. Room temperature photoluminescence measurements show band edge and trap dominated luminescence in the visible regime. Micro-Raman scattering analysis of the HgTe nanocrystals sample reveals the 1LO Raman vibrational mode is at 142.5 cm-1suggesting a shift of 6 cm-1 from it’s bulk value and confirms the crystalline size to be small.