Cross-sectional transmission electron microscopy investigation of the dead layer of ZnS:Ag,Al phosphors in field emission displays

The dead surface layer of blue-emitting ZnS:Ag,Al phosphor with Al metallized thin film in high-voltage field emission displays (FEDs) has been investigated by means of cross-sectional transmission electron microscopy. From these observations, it was found that electron irradiation at 6 keV excitation causes the decomposition of ZnS and the subsequent evolution of sulfur in the topmost surface layer similar to 30 rim, and also causes the formation of lattice defects within the electron penetration depth of similar to 300 nm in a life-end stage. When this evidence was taken into account, it was estimated that the decomposition rate of ZnS and the formation rate of lattice defects depend mainly on the degree of crystallinity and the atomic-scale surface roughness of ZnS phosphor particles. Necessary characteristics of ZnS:Ag,Al phosphors for longer luminescence lifetime in FEDs were suggested in this work. (C) 2001 American Vacuum Society.