Chemical vapor synthesis of fluorine-doped SnO2 (FTO) nanoparticles
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The synthesis and properties of nanocrystalline SnO2 particles and the effects of doping with fluorine are reported in this work. Simultaneous thermal decomposition of tetramethyltin and difluoromethane in the chemical vapor synthesis process was employed. The nanoparticles were analyzed with respect to their structure using X-ray diffraction followed by Rietveld refinement, transmission electron microscopy, nitrogen adsorption, X-ray photoelectron spectroscopy, and Fourier-transformed infrared spectroscopy. Based on the experimental results, a point defect model is proposed, which is supported by density functional theory calculations. At low fluorine concentrations, fluorine substitutes oxygen on a lattice site, while fluorine is located interstitially at high concentrations. The formation of an associated fluorine substitutional–interstitial pair is observed instead of isolated interstitial fluorine.
KeywordsVapor phase synthesis Tin oxide Transparent conducting oxides (TCO) Density functional theory (DFT) Point defects
The authors gratefully acknowledge the help with the photoelectron spectra measured by Erich Golusda (Surface Science Division, Technische Universität Darmstadt). Helpful discussions with Christoph Körber and Andreas Klein (Surface Science Division, Technische Universität Darmstadt) are gratefully acknowledged. The authors thank the State of Hesse for the financial support for a major equipment grant. Financial support by the Deutsche Forschungsgemeinschaft (DFG) through individual grants and through the Center for Functional Nanostructures (CFN) is gratefully acknowledged.
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