Fluorinated organotins as precursors of F-doped tin dioxide

Abstract

Alkoxyfluorodi(β-diketonato)tins 1, trialkynyl(fluoroorgano)tins 2 and difluorodi(β-diketonato)tin 3 have been synthesised in order to prepare F-doped tin dioxide materials by the sol-gel route. After hydrolysis and densification in air at 550°C, these compounds lead to nanocrystalline tin dioxide powders containing the required amount of doping fluorine (4-8 at%) and exhibiting a resistivity at least two times lower than that reported for similar tin dioxide materials. In the case of 2, thermally induced β- or γ-elimination reactions were evidenced by TG/MS, allowing the insertion of fluorine into the oxide network and the clean removal of the undesirable organics. The characterisation of sol-gel thin films prepared from 1 and 3 are also described. They exhibit excellent optical transparencies but resistivities (ρ > 7 10-2 Ω.cm) lower than those of thin layers prepared by pyrosol deposition from SnCl4-NH4F mixtures (ρ < 10-3 Ω.cm). The presence of polluting carbon and the porosity of the sol-gel films are thought to be responsible for these resistivities.