Electron stimulated surface chemical reaction mechanism for phosphor degradation

Borates, phosphates, aluminates, silicates or sulphides are usually used as host lattices for display phosphors. These phosphors reacted similarly under electron bombardment. Nano and micron phosphors normally lose brightness upon bombardment with electron, ion or photon beams. A combination of techniques such as XPS (X-ray photoelectron spectroscopy), AES (Auger electron spectroscopy) and CL (cathodoluminescence) spectroscopy were used to show that the main reason for the degradation in luminescent intensity, of the different phosphors, 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 the result of the growing of a "dead layer" on the surface. In some cases, however, a thermodynamically stable layer formed on the surface as a result of the electron stimulated surface chemical reactions lead to CL stability of the phosphor. The formation of an altered layer (oxide layer) on the surface of the different phosphors leads to a decrease in the luminescent intensity at that specific wavelength and in some cases to an increase of the intensity at another wavelength.