Analysis of critical doping level of sprayed SnO 2 :F films

Fluorine doped tin oxide films were deposited using a simplified spray technique. The concentration of the host precursor (SnCl₂.2H₂O) in the starting solution is varied between 0·2 and 1·0M. The critical doping level of fluorine for which the sheet resistance R_sh acquires a minimum value is observed for each host precursor concentration (HPC). It is found that for a 0·2M solution, R_sh is minimum (42·59 Ω sq⁻¹) when the fluorine doping level is 40 at-%, and the critical doping level gradually increases as the HPC increases. This variation in the critical doping level is correlated with the increase in the number of oxygen sites in the SnO₂ lattice caused by the increase in the HPC. The transmittance in the visible range is 80% when the HPC is 0·2M, and the transmittance decreases as the HPC increases.