Investigation of Structural, Optical and Electrical Properties of Al Doped SnO₂ Thin Films Synthesized by Sol-Gel

Among materials well known to be used as Transparent Conducting Oxide (TCO) and in the field of solar cells, SnO₂ is one of the best. In this work we investigate the doping effect with aluminum on some physical properties of SnO₂. Al doped SnO₂ thin films have been synthesized by sol–gel route using the dip coating method. The films were deposited on glass substrates with different Al concentrations (1%, 3%, 5% and 10%) and heated at 500 °C. The used precursor is SnCl₃ dissolved in ethanol. The obtained thin layers were characterized by X-ray diffraction, UV-visible spectroscopy, by AFM microscopy and electrical measurements. The XRD spectra exhibit a tetragonal crystalline structure of SnO₂ with a preferential direction along (101) for all samples, with grain sizes varying between 10.66 and 20.08 nm. On the other hand the UV-visible spectra show that: all samples of pure and Al doped SnO₂ films have a good transmittance with values between 70–95% in visible region, and an optical gap varying between 3.28 to 3.64 eV. The electrical properties (resistivity, mobility and bulk concentration of charge carriers) obtained by means of Hall Effect indicate that the SnO₂ n-type is inverted to p-type.