Degradation of ZnS FED phosphors

Abstract

The degradation of cathodoluminescent brightness under prolonged electron beam excitation of phosphors has been identified as one of the outstanding critical issues for the flat-panel field emission industries. The ZnS : Cu,Al,Au phosphor powders have been subjected to electron beam bombardment of 2 keV with different electron beam current densities (2.5-88 mA cm −2 ) at an oxygen pressure of 1 × 10 −6 Torr. Auger electron spectroscopy (AES) and cathodoluminescence, both excited by the same electron beam, were used to monitor changes in surface composition and luminous efficiency during electron bombardment. Degradation was manifested by a non-luminescent ZnO layer that formed on the surface of the phosphor according to electronstimulated surface chemical reaction (ESSCR). Lower current densities lead to a higher surface reaction rate, due to a lower local temperature beneath the beam, which resulted in more severe cathodoluminescence degradation. A lower temperature beneath the electron beam may lead to an increase in the surface reaction rate due to the longer time spent by the adsorbed molecules on the surface, with a direct increase in the ESSCR probability.

Luminescence evolution of ZnO single crystal under low-energy electron beam irradiation

“…The requirements for FED phosphors are high luminescence efficiency under low-energy electron excitation and good stability under electron beam irradiation. 3 ZnO is a good candidate for this purpose. Indeed, its wide band gap, its high exciton-binding energy, and its large variety of morphology are attractive properties.…”

Effects of specimen preparation on the cathodoluminescence properties of ZnO nanoparticles

“…The decrease of the UV intensity during electron beam irradiation may be related to the surface modifications, such as adsorption/desorption or electron-simulated surface reaction. [18][19][20][21][22] Compared with high density and bulk crystal, the exposed surface and surface-tovolume ratio are larger for low density, which induces a quicker and more serious drop during irradiation. In the following, the spectra are taken after stabilization of the intensity in order to prevent the effects of the surface modification during the measurements.…”

Cathodoluminescence of Ce-doped Gd2SiO5 and Gd9.33(SiO4)6O2 phosphor under continuous electron irradiation

“…The field emission displays (FEDs) application also requires phosphors to have the high stability during continuous electron beam irradiation [3]. Many works on the degradation mechanism under the continuous electron beam irradiation (CL degradation) have been reported on sulfide and oxide phosphor materials [4][5][6][7][8][9][10][11][12].…”