Properties of fluorine-doped SnO2 films prepared by the spray pyrolysis technique

Transparent conducting amorphous films of SnO2 doped with fluorine are prepared on borosilicate glass plates heated at 400 °C by spray pyrolysis of an aqueous solution of SnCl4 and NH4F. Films of 0.7 μm thick with a sheet resistance of 3 Ω/□ show an average transmittance of 90% along 0.2 to 0.8 μm and consequently large Haack's figure of merit. The optical data obtained together with the imaginary part of the dielectric constant are used in investigating the electronic transitions. A direct allowed transition of 4.1 eV and indirect allowed transition of 2.32 eV together with an assisting phonon of 0.08 eV are observed.