Fluorine-doped tin oxide (FTO) films were prepared at different substrate temperatures by ultrasonic spray pyrolysis technique on glass substrates. Among F-doped tin oxide films, the lowest resistivitiy was found to be 6.2 x 10(-4) Omega-cm for a doping percentage of 50 mol% of fluorine in 0.5 M solution, deposited at 400 degrees C. Hall coefficient analyses and secondary ion mass spectrometry (SIMS) measured the electron carrier concentration that varies from 3.52 x 10(20) cm(-3) to 6.21 x 10(20) cm(-3) with increasing fluorine content from 4.6 x 10(20) cm(-3) to 7.2 x 10(20) cm(-3) in FTO films deposited on various temperatures. Deposition temperature on FTO films has been optimized for achieving a minimum resistivity and maximum optical transmittance. (C) 2009 Elsevier B.V. All rights reserved.