AVS 53rd International Symposium
    Applied Surface Science Thursday Sessions
       Session AS-ThP

Paper AS-ThP28
A Short Review on the ESSCR Mechanism for Phosphor Degradation

Thursday, November 16, 2006, 5:30 pm, Room 3rd Floor Lobby

Session: Aspects of Applied Surface Science Poster Session
Presenter: H.C. Swart, University of the Free State, South Africa
Authors: H.C. Swart, University of the Free State, South Africa
J.J. Terblans, University of the Free State, South Africa
E. Coetsee, University of the Free State, South Africa
O.M. Ntwaeaborwa, University of the Free State, South Africa
M.S. Dhlamini, University of the Free State, South Africa
P.H. Holloway, University of Florida
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Standard cathodoluminescent phosphors normally lose brightness upon bombardment with electron beams. A combination of techniques such as XPS (X-ray photoelectron spectroscopy), AES (Auger electron spectroscopy) and CL (cathodoluminescence) was used to show that the main reason for the degradation in CL intensity is the formation of a non-luminescent dead layer on the surface due to a electron stimulated surface chemical reaction (ESSCR). The decrease in luminance was found to be a result of the growth of the dead layer. Different phosphors which include sulphide-based as well as oxide-based phosphors reacted similar under electron bombardment. When ZnS phosphor powder was exposed to the electron beam in a water-rich O@sub 2@ ambient, a chemically-limited ZnO layer was formed on the surface. A layer of ZnSO@sub 4@was formed on the surface during the electron beam degradation of the ZnS phosphor powder in a dry O@sub 2@ambient. The electron stimulated reaction led to the formation of a luminescent SiO@sub 2@ layer on the surface of the Y@sub 2@SiO@sub 5@:Ce phosphor powder. CeO@sub 2@ and CeH@sub 3@ were also detected on the surface. An increase in the CL intensity at a wavelength of 650 nm was measured during the formation of the luminescent SiO@sub 2@ layer. A less effective SiO@sub x@ (0