DEGRADATION OF ZNS FIELD-EMISSION DISPLAY PHOSPHORS DURING ELECTRON-BEAM BOMBARDMENT

Phosphor thin films of ZnS:Mn on Si(100) have been subject to electron bombardment (0.6-4 keV) over a range of pressures from 1 x 10(-6) to 5 x 10(-8) Torr. Various gases including hydrogen, oxygen, and water v apor were introduced into the ambient during bombardment, to assess th eir effects on the phosphor surface. Auger electron spectroscopy data indicate that electron bombardment in the presence of O-2 and H2O caus ed depletion of sulfur and accumulation of oxygen on the surface. Hydr ogen also caused depletion of sulfur. Removal of sulfur was shown to b e consistent with electron-beam dissociation of molecular species to a tomic hydrogen and/or oxygen, followed by a surface reaction to form h igh vapor pressure sulfur compounds (e.g., SOx and H2S). In the case o f oxygen and water vapor, ZnS was converted to ZnO or ZnSO4. These cha nges in surface chemistry reduced the intensity of cathodoluminescence from ZnS-based phosphors. The mechanisms leading to loss of CL intens ity are discussed. (C) 1997 American Vacuum Society.