Excitation process of the Tb emission center in a ZnS:Tb,F thin-film electroluminescent device
- 1 October 1988
- journal article
- research article
- Published by AIP Publishing in Journal of Applied Physics
- Vol. 64 (7) , 3650-3657
- https://doi.org/10.1063/1.341405
Abstract
The excitation spectrum for terbium (Tb) emission in a ZnS:Tb,F film varies sensitively with Tb concentration, the amount of fluorine (F) relative to Tb, post‐deposition annealing, and the temperature of measurement. There are at least three kinds of channels for the excitation of Tb3+ ions; namely, resonant energy transfer from the recombination of an electron‐hole pair, direct transitions between the 4f 8 configuration states of a Tb3+ ion, and the indirect excitation via lattice defects. A rapid quenching of photoluminescence (PL) is observed above 0.2 at. % of the Tb concentration in the case of indirect excitation of energy transfer. The PL intensity additionally reduced in the presence of F− ions, even at the same Tb concentration. In contrast, when the Tb3+ ions are directly excited to the 5D3 energy state, the PL intensity increases proportionally up to a maximum of about 2 at. %. The luminance of the electroluminescent device behaves in the same way. Another excitation band is found in an energy region slightly below the band gap of ZnS, and is identified as due to Tb‐related complexes associated with sulfur interstitials. The PL characteristics obtained with three excitation channels are also compared with the electroluminescence (EL) characteristics, concerning the effects of post‐deposition annealing and measurement temperature. The excitation mechanism of electroluminescence can be explained on the basis of the direct impact model, and the real nature of the energy transfer process is also discussed.This publication has 19 references indexed in Scilit:
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