Influence of vacuum environment on the aging of phosphors at low electron energies

Screened samples of two different commercial phosphors were aged at 1.5 keV under nominally identical conditions in five different vacuum systems. Aft er aging to doses of similar to 5 C/cm(2) the changes in cathodoluminescenc e (CL) spectral output and photoluminescence properties were determined, an d x-ray photoemission spectroscopy (XPS) and Auger analyses were performed. We observed that while the CL degradation was similar for all systems at l ow electron doses, the aging rates diverged at high doses, suggesting an in creasing importance of the vacuum environment. Post-aged CL spectra showed distinct redshifts in all cases, and the most heavily degraded samples disp layed XPS-determined increases in surface carbon levels. The data suggest a n extrinsic CL aging mechanism; a model involving the conversion of surface hydrocarbons to a metallic graphite phase agrees with the data. (C) 1999 A merican Vacuum Society. [S0734-2101(99)04006-3].