Analysis of critical doping level of sprayed SnO₂:F films

Abstract

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.

Keywords:

• FTO films
• Spray pyrolysis
• Critical doping
• Electrical properties

The authors would like to acknowledge Dr C. Sanjeeviraja, Head, Department of Physics, Alagappa University, Karaikudi, Tamil Nadu, India, for the XRD measurements. One of the authors, Dr K. Ravichandran, acknowledges the financial support by the Tamil Nadu state council for science and technology (TNSCST/S&T Projects/PS/AR/2009-2010·1016).