Cathodoluminescence spectroscopy of silica capped Li doped ZnO nanoparticles

Katie E. McBean ,  Matthew R. Phillips 

University of Technology (UTS), PO Box 123, Broadway, NSW 2007, Sydney, Australia

Abstract

Lithium doped ZnO nanoparticles have been prepared using wet chemical methods and capped with silica by the addition of TEOS (tetraethylorthosilicate) to the reaction mixture. Solutions of zinc acetate in methanol were prepared with a nominal proportion of lithium acetate added to achieve a molar percentage of 0% to 10% Li to Zn. A solution of potassium hydroxide (KOH) in methanol was then added dropwise to these solutions, under stirring, to achieve a pH of 10. The solutions were then left to react for an hour before the addition of TEOS and milliQ water, after which the resulting powders were harvested by centrifugation, rinsed several times and re-suspended in water. Each experiment was repeated without the addition of TEOS to yield uncapped particles as well.

The specimens were characterized using cathodoluminescence (CL) spectroscopy at 80 K and 300 K. The CL spectra of the uncapped ZnO powders all display a near band-edge (NBE) emission centred at 3.27  eV at 300 K, which shifts to 3.35 eV upon cooling to 80 K. The nominally 5% Li doped ZnO powder was the only specimen that displayed any defect emission, a broad peak centred at 1.95 eV at both 300 K and 80 K with the appearance of another peak centred at 2.42 eV at 80 K.

There was no ZnO NBE emission observed for any of the silica capped ZnO particles even at 30 kV.  All spectra showed only a broad emission centred at 2.95 eV attributed to an intrinsic emission in silica. Analysis of the capped specimens by energy dispersive X-ray spectroscopy (EDS) confirmed the presence of Si in addition to Zn and O.

 

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Presentation: Oral at E-MRS Fall Meeting 2009, Symposium C, by Katie E. McBean
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-05-25 18:41
Revised:   2009-06-07 00:48