Cathodoluminescence degradation of Y2SiO5:Ce thin films

Cathodoluminescence (CL) intensity of cerium-doped yttrium silicate (Y2SiO5:Ce) phosphor thin films grown by pulsed laser deposition were investigated for possible application in low voltage field emission displays (FEDs). A thin layer of tin oxide (SnO2) was ablated on some of the films in order to investigate the effect of the coated layer on the degradation of the CL intensity. Auger electron spectroscopy (AES) and CL spectroscopy were used to monitor changes in the surface chemical composition and luminous efficiency of the thin films. AES and CL spectroscopy were done with 2 keV energy electrons and with beam current densities of 26 and 52 mA cm-2. Measurements were done in high vacuum and in oxygen pressures of 1x10-8, 1x10-7, and 1x10-6 Torr. Residual gas mass analysis showed that the adventitious carbon (C) was removed from the surface as volatile gas species, which is consistent with the electron stimulated surface chemical reaction model. The SnO2 coated thin films resulted in a lower but more stable CL intensity than the uncoated thin films. The degradation of the CL intensity was much less for the thin films after the same time period than for the Y2SiO5:Ce powders