Publications [#331965] of Henry Everitt

Papers Published

1. Simmons, JG; Reish, ME; Foreman, JV; Liu, J; Everitt, HO, How sulfidation of ZnO powders enhances visible fluorescence, Journal of Materials Chemistry C, vol. 5 no. 41 (January, 2017), pp. 10770-10776, Royal Society of Chemistry (RSC) [doi]
   (last updated on 2025/11/07)

   Abstract:
   The mechanism for producing efficient white light phosphors from sulfidated zinc oxide (ZnO) powders is elucidated. ZnO powders prepared by vacuum annealing produce powders of oxygen-deficient ZnO:Zn, while ZnO powders annealed in a sulfur atmosphere produce a doped ZnO core with a radially-increasing sulfur concentration gradient capped by a shell of zinc sulfide (ZnS) domains, ZnO:S/ZnS. As compared to ZnO:Zn powders, the intensity and quantum efficiency of the broad, green-tinted white defect fluorescence more than doubled for the ZnO:S/ZnS powders. This fluorescence is mediated by certain neutral donor-bound excitons (DBEs), and it is found that the DBE lifetime and the rate of energy transfer to the defect emission band increases for the ZnO:S/ZnS powders. These DBEs are destroyed by photoexcited free holes, and the hypothesis that they are removed by the type-II band alignment of the ZnS cap with the ZnO:S core is confirmed when ZnO:Zn and ZnO:S/ZnS powders under vacuum are dosed with the hole scavenger methanol: defect emission increases as the free hole concentration decreases. The highest ZnO:S/ZnS quantum efficiency occurs when excited through an impurity band, also produced by sulfur doping, whose energy coincides with the light emitting diodes used for commercial solid state lighting.