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1 Acta Physica Polonica A

1 2009

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Optical Characterization of Laser-Synthesized Anatase TiO_{2} Nanopowders by Spectroscopic Ellipsometry and Photoluminescence Measurements

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Šćepanović M. , Grujić-Brojčin M. , Mirić M. , Dohčević-Mitrović Z. , Popović Z.

Acta Physica Polonica A

2009

tom 116

nr 4

603-606

Nanosized titania (TiO_{2}) is synthesized by laser-induced pyrolysis using TiCl_{4} as a liquid precursor. X-ray diffraction and Raman scattering confirmed anatase structure of TiO_{2} nanocrystals. The dielectric function ε(ω) of TiO_{2} nanopowders has been determined by spectroscopic ellipsometry in the energy range from 1.5 to 6 eV at room temperature. The features observed in ε(ω) have been fitted to analytical line shapes by using the second derivatives of experimental spectra. The energies corresponding to different interband electronic transitions have been determined. Photoluminescence measurements have been carried out in vacuum for T = 20 K and T = 300 K. Under laser irradiation with sub-band gap photon energy, anatase nanocrystals have displayed strong visible photoluminescence emission. In this broad photoluminescence band different variations of line shape and position with excitation energy and temperature are observed for nanopowders with different crystallite size, pointing out to the various electronic transitions mediated by defect levels within the band gap.