<title>Color center formation in thin film electroluminescent (EL) and cathodoluminescent (CL) phosphors by ion implantation</title>

Abstract

Ion implantation can introduce color centers into thin film phosphors for electroluminescent (EL) and cathodoluminescent (CL) displays. Color pixel patterns are defined through a simple shadow mask that is translated across the thin film phosphor host. Thin film samples of the traditional EL and CL hosts ZnS and Zn<SUB>2</SUB>SiO<SUB>4</SUB> and thin film CaGa<SUB>2</SUB>S<SUB>4</SUB> were prepared on conducting glass substrates. The samples were implanted with various doses of Cu, Mn, Tb, Sm, Ce, and Eu ions; effects of cation-anion stoichiometry were studied through co-implantation of S, O, F, and Al in combination with the activator ion. Post implant anneals were used to redistribute the implanted ions and remove any residual damage. We have demonstrated four-color EL emission (RGBY) in a single thin film panel by implanting Sm, Mn, Tb, and Tm into ZnS. The Mn yellow brightness equaled that of co-evaporated films. CaGa<SUB>2</SUB>S<SUB>4</SUB> implanted with Ce showed blue emission of about 1 fL 60 Hz. For thin film CL phosphor studies, we implanted Cu and Al at different relative doses in ZnS, followed by annealing. CL measurements at 1500 eV showed that emission changed from blue (470 nm) to green (520 nm), depending on the implanted Cu/Al ratio. Bright green CL (531 nm) was achieved by implanting Mn in Zn<SUB>2</SUB>SiO<SUB>4</SUB> followed by a relatively high temperature anneal, to form the standard P-1 phosphor as a thin film.