Observation of the Morphology of ZnO:Al Nanocoating by Pulsed Laser Deposition on ZnS:Ag Phosphor for Degradation Repres
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OBSERVATION OF THE MORPHOLOGY OF ZnO:Al NANOCOATING BY PULSED LASER DEPOSITION ON ZnS:Ag PHOSPHOR FOR DEGRADATION REPRESSION Sanshiro Nagare* Nara Machinery Co., Ltd, 2-5-7 Jonan-jima, Ohta-ku, Tokyo, 143-0002, Japan Michael Ollinger, Rajiv Singh University of Florida, Department of Materials Science and Engineering, Gainesville, Florida, 32611, U.S.A. Mamoru Senna Keio University, Faculty of Science and Technology, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
ABSTRACT Degradation due to electron beam irradiation is a significant problem for ZnS based phosphors, particularly for flat panel displays. In this study, ZnS:Ag phosphor particles were coated by nanoparticles of ZnO:Al by pulsed laser deposition (PLD), to suppress the cathodoluminescence (CL) degradation process under electron bombardment at 15 kV. The pressure of the vacuum chamber and the deposition time were changed to control the morphology of the coating, i.e. thickness, continuity, and uniformity. CL degradation of the phosphors was slowed down for all cases by the nanocoating. The relationship between the CL degradation and the morphology of the coating material was examined by an SEM combined with a simultaneous CL measurement device. Degradation mechanisms were elucidated in terms of the morphology of the coating material and the change in the surface atomic species during irradiation of the electron beam.
INTRODUCTION Field emission display (FED) is one of the attractive flat panel display devices, which is recently studied and has drawn attention. However, degradation of the phosphor materials due to electron bombardment is a major problem for application. In another words, techniques to prevent or suppress phosphor degradation, or the decrease in the cathodoluminescence (CL) of the phosphor, is necessary. Research works related to the mechanism of phosphor degradation and methods to minimize degradation are plenty [1-4]. In this study, pulsed laser deposition (PLD) was used to coat ZnS:Ag phosphor by ZnO:Al nanoparticles in order to retard phosphor degradation due to electron bombardment. We focus on the morphology of the nanocoating by
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varying deposition pressure and the relationship between CL degradation. EXPERIMENTAL METHOD Figure 1 shows the scheme of the apparatus used for PLD. KrF excimer laser with a wavelength of 248 nm and a pulse frequency of 5 Hz was used as the laser beam source. ZnS:Ag (Osram Sylvania, standard P22B CRT) was used as the phosphor particles and ZnO:Al as the coating material. The coated phosphor particles were characterized by using SEM (JEOL 6400) combined with a simultaneous CL measurement device (Gatan PANACL6 detector with an Oxford PA3 Photo Amplifier). This combined device enables to acquire simultaneously, SEM pictures and CL images before and after electron bombardment at 15 kV, and CL degradation curves. TEM was used to observe the morphology of the coating.
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Motors
Off-set Weight
Transparent Window
Laser Pulse Plume
Phosphor Particles Vacuum Chamber
Mechanical Shake
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