Research on Electroluminescence in Thin Film Yttrium Oxysulfide

摘要

Thin films of a rare-earth oxysulfide phosphor, yttrium oxysulfide:europium, were evaluated for use in a thin film electro-luminescent emitter (TFEL). For the first time, emission typical of the rare earth activator was observed in a rare earth host TFEL emitter. The films were characterized for optical spectrum, brightness-voltage characteristic, photoluminescence, crystal structure, and compared to efficient cathodoluminescent powder phosphors, yttrium oxysulfide:europium, as well as high efficiency TFEL emitters of zinc sulfide:manganese. The E-beam deposited films exhibited considerable photoluminescence and cathodoluminescence after a high temperature anneal (600 C). However, the anneal induced cracks in the phosphor film, which in turn limited the maximum applied voltage and electroluminescent brightness to less than 1 ft-L. Alternate substrate materials and process schedules minimized the cracking, but did not eliminate this fundamental problem.