Nano-environment effects on the luminescence properties of Eu(3+)-doped nanocrystalline SnO2 thin films.

Nanocrystalline tin (IV) oxide thin films doped with Eu(3+) ions are synthesized using a simple spin-coating method followed by postannealing in an O(2) flow at 700 °C. Transmission electron microscopy and x-ray photoelectron spectroscopy studies illustrate the incorporation of Eu(3+) ions in the films with a high atomic percentage of 2.7%-7.7%, which is found to be linearly dependent on the initial concentration of Eu(3+) in the precursor solution. Glancing incidence x-ray diffraction results show that the crystalline grain sizes decrease with increasing the Eu(3+) concentration and decreasing the postannealing temperature with the emergence of the Eu(2)Sn(2)O(7) phase at high Eu(3+) concentrations (≥5.3 at.%). Luminescence spectra of these doped samples show the characteristic narrow-band magnetic dipole emission at 593 nm and electric dipole emission at 614 nm of the Eu(3+) ions, arising from UV absorption at the SnO(2) band-edge followed by energy transfer to the emission centers. Manipulating the crystallite size, composition, and defect density of the samples greatly affects the absorption edge, energy transfer, and therefore the emission spectra. These modifications in the environment of the Eu(3+) ions allow the emission to be tuned from pure orange characteristic Eu(3+) emission to the broadband emission corresponding to the combination of strong characteristic Eu(3+) emission with the intense defect emissions.