Luminescence characterization and electron beam induced chemical changes on the surface of ZnAl2O4:Mn nanocrystalline phosphor

• Published in: Applied surface science 2011-02, Vol.257 (8), p.3298-3306
• Main Authors: Pitale, Shreyas S., Kumar, Vinay, Nagpure, I.M., Ntwaeaborwa, O.M., Swart, H.C.
• Format: Article
• Language: English
• Subjects: Auger electron spectroscopy; Cathodoluminescence; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Electron beams; Emission; Exact sciences and technology; Excitation; Luminescence; Nanocrystals; Phosphors; Physics; X-ray photoelectron spectroscopy
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2010.11.006

▶ Stable green cathodoluminescence (CL) obtained under low voltage electron beam excitation. ▶ Auger and XPS probed chemical changes on the surface of the ZnAl2O4:Mn2+. ▶ A thermodynamically stable Al2O3 layer stabilises the CL. Luminescence characteristics and surface chemical changes of nanocrystalline Mn2+ doped ZnAl2O4 powder phosphors are presented. Stable green cathodoluminescence (CL) or photoluminescence (PL) with a maximum at ∼512nm was observed when the powders were irradiated with a beam of high energy electrons or a monochromatic xenon lamp at room temperature. This green emission can be attributed to the 4T1→6A1 transitions of the Mn2+ ion. Deconvoluted CL spectra resulted in two additional emission peaks at 539 and 573nm that may be attributed to vibronic sideband and Mn4+ emission, respectively. The luminescence decay of the Mn2+ 512nm emission under 457nm excitation is single exponential with a lifetime of 5.20±0.11ms. Chemical changes on the surface of the ZnAl2O4:Mn2+ phosphor during prolonged electron beam exposure were monitored using Auger electron spectroscopy. The X-ray photoelectron spectroscopy (XPS) was used to determine the chemical composition of the possible compounds formed on the surface as a result of the prolonged electron beam exposure. The XPS data suggest that the thermodynamically stable Al2O3 layer was formed on the surface and is possibly contributing to the CL stability of ZnAl2O4:Mn phosphor.