Optical Behavior of ZnS:Cu Microcrystals Embedded in Porous Silica Gels
Emission and excitation spectra of ZnS:Cu microcrystals trapped in porous silica xerogels are presented. This system is characterized by intense, long-lived green emission at room temperature. It was observed that this emission was greatly reduced after compressing the xerogel samples.
Optical centers of cerium in silica glasses obtained by the sol-gel process
Abstract A spectral-luminescent study of Ce-containing silica gel-glasses doped at the sol stage and by impregnating porous xerogels with activator chloride salt solutions has been performed. The influence of the degree of doping and redox conditions of vitrification on the activator charge state and the content of hydroxyl ions and chlorine in the glass is considered. The preservation of the glass phase composition and the non-linear increase in the visible absorption intensity with increasing activator concentration from 5 × 1017 to 3.0 × 1020 ions/cm3 are noted. It is concluded that there are two main types of optical centre. It is assumed that they represent Ce(III) oxygen complexes whose nearest surrounding includes quadruply charged (the first type) and triply charged (the second type) ions of cerium. Evidence has been obtained in favor of the superexchange excitation transfer to the central ion of Ce(III) oxygen complexes from photoreduced to the triply charged state of the same ion name of Ce(IV) oxygen complexes.
Anomalous Annealing Behavior of Arsenic Implanted Silicon as a Function of Dose and Energy
Anomalous annealing behavior of damage in As implanted Si has been investigated by channeling effect measurements. Room temperature As implants with doses from 1014 to 2 × 1016cm-2 at energies ranging from 50 to 250 keV into Si were annealed over the range of 600°C to 1100°C. Anneal temperatures ≥ 950°C reduce the disorder for ion doses of 0.5 to 1 × 1016 cm-2 at energies between 50 and 250 keV. Anomalously high residual disorder was found for the intermediate doses of 2 × 1014 to 2 × 10/cm2 implanted above 100 keV. For this intermediate dose, annealing of implants performed at liquid nitrogen temperatures did not show significant reduction in this damage. However implants at 200° to 300°C indicate a lower amount of damage compared to the room temperature implants.