Optical Study of ZnS:Mn Thin Films with High Mn Concentrations

Electron-beam evaporated ZnS: Mn thin films with high Mn concentrations between 2 and 6 mol% are studied by photoluminescence emission, excitation, and decay measurements in the temperature range 28 to 300 K. The usual yellow and an additional red emission band with the same excitation spectrum are found similarly to the results for highly Mn-doped ZnS single crystals. The observed characteristic temperature and Mn-concentration dependence of both bands are quantitatively discussed on the basis of an effective-lifetime model assuming a radiationless resonance energy transfer from the primarily excited Mn2+ ions via several other Mn2+ ions by an exchange mechanism finally to red emission and nonradiative centres, respectively. Especially, by this way an explanation is proposed for the measured increase of the thermal quenching and the decrease of the decay time of the yellow emission band with increasing Mn concentration.