Electroluminescence and photoluminescence in sputtered ZnS:TbFx thin films

A study has been made on the electroluminescence (EL) and photoluminescence (PL) spectra of sputtered ZnS:TbFx thin films. The brightness and EL spectra are strongly dependent on x. The highest brightness has been obtained at x=1. From a comparison of EL and PL of standard samples, we conclude that, in the case of x=1, Tb exists as a complex center composed of Tb substituted for Zn and interstitial F and this center gives high EL efficiency. In the case of x=3, on the other hand, TbF3 is doped as a molecular center in the ZnS film exhibiting inefficient EL.