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Standard cathodoluminescent phosphors normally lose brightness upon bombardment with electron beams. A combination of techniques such as x-ray photoelectron spectroscopy, Auger electron spectroscopy, and cathodoluminescence (CL) spectroscopy was used to show that the main reason for the degradation in CL intensity is the formation of a nonluminescent “dead layer” on the surface due to an electron stimulated surface chemical reaction. The decrease in luminance was found to be a result of the growth of the dead layer. Different phosphors which include sulfide-based as well as oxide-based phosphors reacted similarly under electron bombardment. When ZnS phosphor powder was exposed to the electron beam in a water-rich O2 ambient, a chemically limited ZnO layer was formed on the surface. A layer of ZnSO4 was formed on the surface during the electron beam degradation of the ZnS phosphor powder in a dry O2 ambient. The electron stimulated reaction led to the formation of a luminescent SiO2 layer on the surface of the Y2SiO5:Ce phosphor powder. An increase in the CL intensity at a wavelength of 650 nm was measured during the formation of a luminescent SiO2 layer. [ABSTRACT FROM AUTHOR]

Abstract: The green photoluminescence (PL) peak from SrAl2O4:Eu2+, Dy3+ phosphor is normally asymmetrical and tails towards the longer wavelengths. Previous Gaussian de-convolution resulted in two peaks attributed to Eu2+ occupying the two different crystallographic Sr2+ sites. In this letter two resolved peaks through cathodoluminescence (CL) measurements are reported. The intensity degradation upon the phosphor charging when exposed to electron beam reveals additional information about the electronic transitions. The observed peak in the longer wavelength is associated with preferential alignment of one of the Eu2+ d-orbital. The observations are used to modify Clabau et al.''s model of afterglow mechanism. [Copyright &y& Elsevier]