We investigated the degradation characteristics of a low-voltage cathodoluminescence (CL) of ZnS:Ag,CI phosphor screen under the environment of the panel sealing process. Auger electron spectroscopy and CL measurements showed that compositional changes occurred in the surface layer of the phosphor screen. The oxide layer formed during the panel sealing process influenced the initial drop in CL intensity of the phosphor screen and the carbon adsorption under electron bombardment. We used x-ray photoelectron spectroscopy and plasmon energy loss to investigate the changes of carbon bonding in the surface layer of the phosphor screen. During prolonged electron bombardment, the CL of the phosphor screen decayed due to the accumulation of carbon. The longer the electron bombardment time, the more graphitic the surface became. (C) 2003 American Vacuum Society.