Characterization of SnO₂ thin films through thermoelectric power measurements

High transparent and conductive SnO₂ thin films deposited by spray pyrolisis using SnCl₂ as precursor solution and HF as source of the doping impurities were characterized through thermoelectric power, Hall voltage and conductivity measurements, in order to determine the influence of the F-content on the electrical transport properties. No doped SnO₂ samples with high carrier concentrations (about 3×10¹⁹ cm^-3) were obtained, possibly as consequence of incorporation of Cl^- impurities in anion sites of the SnO₂ lattice during the film deposition. Adding HF to the precursor solution the carrier concentration was increased in about two order of magnitude. It was found that the very low values of resistivity (about 1.7×10^-4 Ωcm) presented by the SnO₂:F thin films are mainly due to a very high concentration of free carriers (about 5×10²¹cm^-3) generated by doping at anion sites with Cl^- and/or F^--impurities. The study revealed additionally that the mobility of the free carriers is significantly reduced by increasing of F^-- concentration, indicating that at room temperature the interaction of free carriers with ionized impurities could be the dominant scattering mechanism.