AVS 47th International Symposium
    Flat Panel Displays Tuesday Sessions
       Session FP+VT-TuA

Paper FP+VT-TuA5
Cathodoluminescence from Thin Film versus Powder Phosphors

Tuesday, October 3, 2000, 3:20 pm, Room 313

Session: Emissive Displays and Device Reliability
Presenter: L.C. Williams, University of Florida
Authors: L.C. Williams, University of Florida
B. Abrams, University of Florida
W. Roos, University of the Orange Free State
P.H. Holloway, University of Florida
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Thin film cathodoluminescent (CL) phosphors have a number of potential advantages over powder phosphors, such as better mechanical integrity, better thermal heat sinking, more efficient use of material, and better planarity. However most CL screens use powder phosphors due to better brightness, efficiency, and crystallinity. In the current work, we have examined the effects of thin films versus powders on the rate of degradation of ZnS:Mn in residual vacuum gases. The ZnS:Mn thin films were RF planar magnetron sputter deposited onto glass/ITO substrates at a growth temperature of 160°C. The powders were simply cold compacted into shallow stainless steel sample holders. Degradation was shown to occur by the Electron Stimulated Surface Chemical Reaction (ESSCR) mechanism, in which the electron beam dissociated adsorbed oxidizing molecular species (e.g. H@sub 2@O) to cause conversion of luminescent ZnS:Mn to non-luminescent ZnO:Mn. The degradation was faster at low primary beam energy (0.5keV) versus high energy (5keV). Degradation was dependent upon the gas pressure and electron dose (versus time of exposure). Degradation of as deposited thin films was different from that for films annealed at 750°C for 5 minutes; this will be interpreted in terms of the point defect density of as deposited versus annealed phosphor films. After correction for the true surface area of powders versus films, the rate of degradation will be compared. The mechanisms leading to the different degradation rates for films versus powders will be discussed.