Publications
Effects of coatings on temporal cathodoluminescence quenching in ZnS:Ag,Cl phosphors
Powder phosphors of ZnS:Ag,Cl coated with SiO{sub 2} (22 or 130 nm nanoparticles), SnO{sub 2} or Al{sub 2}O{sub 3} showed different cathodoluminescent (CL) brightness versus time (temporal CL quenching) behavior as compared to noncoated phosphors. At high current density (e.g., 300-800 {micro}A/cm{sup 2}), the CL emission intensity of coated ZnS:Ag,Cl decayed over the first {approx}15 s of electron beam irradiation, which was postulated to result from a large concentration of nonradiative surface centers generated during surface modification of the phosphor, and from localization of generated electrons at the surface due to primary beam-induced internal electric fields. During the first {approx}15 s of excitation, generated electrons are postulated to be redistributed by this induced internal electric fields, resulting in increased nonradiative surface recombination between electrons and holes. The formation of a nonradiative surface layer either from electron-stimulated surface chemical reactions on coated or from heat treatment of noncoated ZnS:Ag,Cl powder phosphors were shown to affect temporal CL quenching.