MN2-FILM ELECTROLUMINESCENT DEVICES( EPR CHARACTERIZATION OF THIN)

The manganese luminescenct center in ZnS:Mn powder and thin films have been investigated as a function of Mn concentration using EPR spectro meter. While the concentration of the isolated Mn2+ ions decreases wit h increasing Mn concentration, the concentration of the Mn clusters in creases. It is turned out that the proper Mn concentration for a good ZnS:Mn ELD is about 0.5 mole%. At high Mn concentrations, where the Zn S powder has a dominant hexagonal phase, the Mn ion still prefers to s ubstitute for Zn in ZnS:Mn at the cubic site rather than at the hexago nal site. The isolated Mn2+ ions seem to be changed to monovalent Mn1 after aging of ZnS:Nln ELD.