Energy transfer processes and photoluminescence properties of homogeneously- and delta-doped ZnS:Mn

An investigation is reported of the energy transfer processes in ZnS:Mn by photoluminescence spectroscopy. At temperatures >50 K, the luminescence decay of homogeneously doped ZnS : Mn was strongly non-exponential due to non-radiative energy transfer processes. The concentration dependence of the effective lifetime was found to change with temperature. Analysis of the temperature dependence showed that the energy transfer between Mn ions was active only for Mn concentrations >2%, and that the energy transfer between Mn ions was mediated by an electric dipole-dipole interaction. The delta-doped ZnS : Mn showed a faster decay due to the enhanced overlap between 3d and s-p host states caused by lattice strain. From the temperature dependence, the two-dimensional confinement of energy transfer was observed for large spacings between doping planes. When the doping planes were brought close together, the delta-doped samples behaved similarly to the homogeneously doped ZnS:Mn, indicating that the energy transfer was no longer two-dimensionally confined. (C) 1998 Published by Elsevier Science B.V. All rights reserved.