XPS analysis for degraded Y_2SiO_5:Ce phosphor thin films

摘要

X-ray photoelectron spectroscopy (XPS) results were obtained for standard Y_2SiO_5:Ce phosphor powders as well as undegraded and 144h electron degraded Y_2SiO_5:Ce pulsed laser deposited (PLD) thin films. The two Ce 3d peaks positioned at 877.9 ±0.3 and 882.0 ± 0.2 eV are correlated with the two different sites occupied by Ce in the Y_2SiO_5 matrix. Ce replaced the Y in the two different sites with coordination numbers of 9 and 7. The two Ce 3d XPS peaks obtained during the thin film analysis were also correlated with the luminescent mechanism of the broad band emission spectra of the Y_2SiO_5:Ce X_1 phase. These two different sites are responsible for the two main sets of cathodoluminescent (CL) and photolumines-cence (PL) peaks situated at wavelengths of 418 and 496nm. A 144h electron degradation study on the Y_2SiO_5 :Ce thin film yielded an increase in the CL intensity with a second broad emission peak emerging between 600 and 700 nm. XPS analysis showed the presence of SiO_2 on the surface that formed during prolonged electron bombardment. The electron stimulated surface chemical reaction (ESSCR) model is used to explain the formation of this luminescent SiO_2 layer.