Auger electron spectroscopy and X-ray photoelectron spectroscopy study of the electron-stimulated surface chemical reaction mechanism for phosphor degradation

Phosphors normally lose brightness upon bombardment with electron, ion or photon beams. A combination of techniques such as X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and cathodoluminescence (CL) spectroscopy was used to show that the main reason for the degradation in luminescent intensity under electron bombardment is the formation of a non-luminescent layer on the surface due to an 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 sulfide-based as well as oxide-based phosphors reacted similarly under electron bombardment. The formation of an altered layer (oxide layer) on the surface of the different phosphors leads to the decrease of the luminescent intensity at that specific wavelength and in some cases to an increase of the intensity at another wavelength. The mechanisms of the degradation of several rare earth and transition metal phosphors are discussed in detail.