Cathodoluminescence (CL) degradation of Y2O3:Dy3+ nanophosphors prepared by the solution combustion method was explored for feasible applications in low voltage field emission displays (FEDs). Oxide materials are excellent candidates for FED fabrication due to their high melting points, chemical and radiation stability with long lifetimes, high color purity, and being environmentally friendly. Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) were used to monitor changes in the surface chemical composition and correlation fit with CL degradation. AES and CL spectroscopy (2 keV energy electrons and with a beam current of 15 μA) measurements were done in high vacuum (1.5 × 10−8 Torr) and oxygen pressures of 1 × 10−7 and 5 × 10−7 Torr. The Y2O3:Dy3+ nanophosphor showed strong yellow (572 nm) and relatively weaker blue (492 nm) CL emissions. These CL emissions increased as carbon (C) was depleted from the surface, and then it slightly decreased at a high electron dose in both the vacuum and oxygen atmospheres, for electron doses up to about 690 C/cm2. The C was depleted from the surface due to electron stimulated reactions. No significant change in the chemical state of Y 3d was observed with XPS high resolution spectra for the postirradiation sample. The change in the CL intensity was, therefore, attributed to the depletion of C from the surface.

Cathodoluminescence (CL) degradation measurements on Y2O3:Tm3+ nanoparticles were made to test for potential application as a blue phosphor in low-voltage field emission displays. The incorporation of Tm3+ into the Y3+ sites in the Y2O3 lattice was confirmed by x-ray photoelectron spectroscopy and CL spectra. The Y2O3:Tm3+ nanophosphor was investigated under vacuum and oxygen (O2) backfilled conditions in order to control surface chemical adsorption. The Auger electron spectroscopy (AES) and the CL data collection were performed simultaneously when the nanophosphor was bombarded with a beam of electrons with a 3 μA beam current and an accelerated voltage of 2 keV in both atmospheres. The Y2O3:Tm3+ nanophosphor displayed strong blue (457 nm) and relatively weak near infrared (812 nm) emissions. The CL intensity decreased as a function of electron dose in vacuum, while in the O2 backfilled pressure it only started to decrease after an electron dose of ∼250 C/cm2 after removal of C from the surface. The CL emission’s intensity increased at an initial electron dose in the O2 backfilled pressure due to the desorption of C from the surface. The removal of C and other surface impurities from the surface was ascribed to be due to electron stimulated surface chemical reactions. The AES and the thermoluminescence (TL) data suggested that an O deficient layer was formed on the surface. TL glow curves confirmed that the electron beam induced deep traps at activation energies of 1.28, 1.37, and 1.42 eV in the Y2O3:Tm3+ nanophosphor that was attributed to oxygen vacancies. Mechanisms, where O deficiency leads to an improvement in the CL intensity, were also discussed.

Monoclinic Bi2O3:Ho3+ powder was synthesized using a co-precipitation method, followed by the deposition of Bi2O3:Ho3+ thin films on Si (100) substrates at various substrate temperatures (room temperature–600 °C) and oxygen partial pressures (5–200 mT) using pulsed-laser deposition. X-ray diffraction analysis showed a single α-Bi2O3 phase at temperatures of 400 and 500 °C, while a mixed α- and β-Bi2O3 phase was obtained at 600 °C. The films deposited at the different oxygen partial pressures showed an α-Bi2O3 and non-stoichiometric phase. The influences of different substrate temperatures and oxygen partial pressures on the morphology and the thickness of the films were analyzed using a scanning electron microscope. The root mean square roughnesses of the films were determined by using an atomic force microscope. The surface components, oxidation states and oxygen vacancies in all the deposited thin films were identified by X-ray photoelectron spectroscopy. The optical band gap of the Bi2O3:Ho3+ thin films was calculated using diffused reflectance spectra and was found to vary between 2.89 and 2.18 eV for the deposited films at the different temperatures, whereas the different oxygen partial pressures showed a band gap variation between 2.97 and 2.47 eV. Photoluminescence revealed that Ho3+ was the emitting centre in the isolated thin films with the 5F4/5S2 → 5I8 transition as the most intense emission in the green region.