This decrease is more obvious with the increase of Mn concentration We assign

This decrease is more obvious with the increase of mn

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undoped and doped samples, a significant decrease is observed. This decrease is more obvious with the increase of Mn concentration. We assign this behaviour to the occurrence of additional electronic levels inside the band gap, as a consequence of Mn incorporation in the SnO 2 lattice. 3.4. FT-IR Spectroscopy To obtain more details regarding the structure of Mn doped SnO 2 , FT-IR analysis was performed on all doped samples, their spectra being shown in figure 6. The peak at 1627 cm -1 corresponds to water molecules adsorbed from the environment. It can be clearly seen that all samples showed similar spectra, with typical rutile type SnO 2 peak 615 cm -1 . This band is assigned to fundamental Sn-O vibration, with Sn-O-Sn in antisymetric stretching mode [36- 38]. The inset shows that the main peak exhibits one left shoulder at 680 cm -1 , whose signal belongs to O-Sn-O vibration [39, 40], and two right shoulders, at 508cm -1 and 470 cm -1 that are also characteristic to Sn-O vibration [41]. No Mn-O characteristic peaks were observed because the Mn-O vibration is masked by the stronger Sn-O vibration, as both bonds vibrate in the same wavenumbers interval [42-44].
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50 Ana-Maria Ungureanu, Ioana Jitaru, Florinela Gosnea Fig. 6 - FTIR spectra for 2%,4% and 6% at. Mn doped SnO 2 , in comparison with a previously obtained undoped SnO 2 sample 4. Concluions Tin dioxide powders containing nanocrystallites doped with 2, 4, and 6% at. Mn were obtained through an ethylene glycol assisted sol-gel method. The thermal treatment conducted on all samples was performed in accordance with TG/DSC results, which suggest that a good calcination may be carried at 500 0 C. XRD confirms the formation of nanostructured SnO 2 , with a rutile type structure, with small crystallite size, of 6 nm. Tin dioxide easily incorporates Mn ions up to 6% concentration, when no secondary phases are observed, suggesting that at this concentration, the Mn solubility into the host lattice is not reached. UV-VIS spectra obtained for all three samples are characteristic to tin dioxide. Mn presence in the tin dioxide lattice does not significantly influence the shape of UV-VIS spectra. The calculated band gap energies decrease with the increase of dopant concentration, as a result of the occurrence of additional energetic levels in the forbidden band. Acknowledgements The work has been funded by the Sectoral Operational Programme Human Resources Development 2007-2013 of the Romanian Ministry of Labour, Family and Social Protection through the Financial Agreement POSDRU/107/1.5/S/76903 .
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Mn doped SnO 2 prepared by a sol-gel method 51 R E F E R E N C E S [1] T. Dietl, H. Ohno, F. Matsukura,J. Cibert,D. Ferrand , Science 287, 1019 (2000) [2] K. Gopinadhan, Subhash C. Kashyap, Dinesh K. Pandya, and Sujeet Chaudharya , Journal of Applied Physics 102, 113513, 2007 [3] K.Vadivel, V.Arivazhagan, S.Rajesh , Research Volume 2, Issue 4, April-2011 ISSN 2229-5518 [4] R. Brahma, M G. Krishna and A K Bhatnagar , Bull. Mater. Sci., 29(3), 2006, 317–322. [5] H. Kimura, T. Fukumura, M. Kawasaki, K. Inaba, T. Hasegawa et al , Appl. Phys. Lett. 80, 94 (2002); [6] C. B. Fitzgerald, M. Venkatesan, A. P. Douvalis, S. Huber, and J. M. D. Coey , Journal of Applied Physics 95(11), 2004 [7] S. Gnanam, V. Rajendran
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