title: ZnO Luminescence and scintillation studied via photoexcitation, X-ray excitation, and gamma-induced positron spectroscopy.
abstract: The luminescence and scintillation properties of ZnO single crystals were studied by photoluminescence and X-ray-induced luminescence (XRIL) techniques. XRIL allowed a direct comparison to be made between the near-band emission (NBE) and trap emissions providing insight into the carrier recombination efficiency in the ZnO crystals. It also provided bulk luminescence measurements that were not affected by surface states. The origin of a green emission, the dominant trap emission in ZnO, was then investigated by gamma-induced positron spectroscopy (GIPS) - a unique defect spectroscopy method that enables positron lifetime measurements to be made for a sample without contributions from positron annihilation in the source materials. The measurements showed a single positron decay curve with a 175 ps lifetime component that was attributed to Zn vacancies passivated by hydrogen. Both oxygen vacancies and hydrogen-decorated Zn vacancies were suggested to contribute to the green emission. By combining scintillation measurements with XRIL, the fast scintillation in ZnO crystals was found to be strongly correlated with the ratio between the defect luminescence and NBE. This study reports the first application of GIPS to semiconductors, and it reveals the great benefits of the XRIL technique for the study of emission and scintillation properties of materials.
authors.affiliation: Department of Physics and Astronomy, Bowling Green State University, Bowling Green, Ohio 43403, USA.
authors.forename: J
authors.initials: J
authors.lastname: Ji
authors.affiliation: Department of Physics and Astronomy, Bowling Green State University, Bowling Green, Ohio 43403, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Colosimo
authors.affiliation: Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Anwand
authors.affiliation: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Boatner
authors.affiliation: Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Wagner
authors.affiliation: Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403, USA.
authors.forename: P S
authors.initials: PS
authors.lastname: Stepanov
authors.affiliation: Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden, Germany.|Technische Universität Dresden, 01062 Dresden, Germany.
authors.forename: T T
authors.initials: TT
authors.lastname: Trinh
authors.affiliation: Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden, Germany.
authors.forename: M O
authors.initials: MO
authors.lastname: Liedke
authors.affiliation: Martin-Luther University, Department of Physics, 06099 Halle, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Krause-Rehberg
authors.affiliation: Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden, Germany.|Technische Universität Dresden, 01062 Dresden, Germany.
authors.forename: T E
authors.initials: TE
authors.lastname: Cowan
authors.affiliation: Department of Physics and Astronomy, Bowling Green State University, Bowling Green, Ohio 43403, USA.|Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403, USA.
authors.forename: F A
authors.initials: FA
authors.lastname: Selim