Optical and magnetic properties of (Er, F) co-doped SnO_2 nanocrystals

Authors: VINOD KUMAR, SITHARAMAN UMA, RAJAMANI NAGARAJAN

Abstract: Uniformly (Er, F) co-doped SnO_2 nanocrystals, obtained by a low-temperature solution-based method, were characterized by a variety of analytical techniques. The structure, morphology, and ratio of the elements were confirmed by PXRD, SEM, and TEM analysis, respectively. From XPS analysis, atomic concentrations of Sn, O, and F were quantified. Interparticle pore size increased significantly (with a mean pore diameter of 25.82 nm) in the co-doped sample. Higher in-plane oxygen vacancies and bands due to multiphonon scattering were observed in the Raman spectrum of the sample. The defect traps in the sample were experimentally determined using TL spectroscopy. A broad intense glow curve at 485 K and a weak emission at 600 K in the TL spectrum were quenched on exposure to UV radiation. A large blue shift of the exciton absorption (due to the Moss--Burstein effect) and sharp bands due to intraconfigurational f-f transitions were observed for (Er, F) co-doped SnO_2 with an estimated band gap of 4.18 eV. From the photoluminescence spectral studies, 3 types of emission centers at 471 nm, 546 nm, and 627 nm were detected. Co-doping stabilized ferromagnetism in SnO_2 at room temperature.

Keywords: Luminescence, ferromagnetism, defects, Moss--Burstein effect, nanocrystalline

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