Blue and near infrared luminescence degradation by electron beam irradiation in Y2O3:Tm3+ nanophosphors

Abstract

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.