Fluorine-doped tin dioxide (FTO) nanocrystals were prepared with a sol-gel process followed by a hydrothermal treatment using SnCl4 and NH4F as SnO2 and fluorine dopant, respectively The nanostructure and composition were characterized by X-ray diffraction (XRD). transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), zeta potential analysis, electrochemical measurement technology and X-ray photoelectron spectroscopy (XPS) respectively The diameter of the fluorine doped SnO2 nanocrystal in rutile-type structure is about 10 nm Compared to the pure SnO2 nanocrystals, the fluorine doped SnO2 nanocrystals can be dispersed homogeneously in H2O, forming transparent sol with high stability The powder of fluorine doped SnO2 nanocrystals could be obtained by removing the solvent, and the electrical resistivity properties were measured by a four-point probe measurement The results show that sheet resistances (Rs) of fluorine doped SnO2 decrease with the increasing NH4F/Sn molar ratio in the range from 0 to 2. However, further increase of NH4F/Sn molar ratio from 2 to 5 leads to higher sheet resistance. The F/Sn molar ratio of fluorine doped SnO2 measured by XPS is about 0 18 when NH4F/Sn molar ratio is equal to 2. and the sheet resistance of fluorine doped SnO2 powder is 110 Omega/square (C) 2010 Elsevier Inc. All rights reserved.