In this study, a novel process for depositing tin oxide thin films by electrodeposition has been developed. Amorphous phase of the as-deposited film was obtained at the temperature of 85°C. Nanocrystalline SnO 2 having tetragonal structure with a grain size in the range of 4 to 7 nm was obtained by heat-treatment at 400°C in a vacuum for 4 h. Porous, dense, and uniform morphologies for the deposits can be obtained by controlling current density during deposition. Results of infrared spectra, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy analyses were described and correlated with the process of deposition and characteristics of the resulting SnO 2 films.Electrodeposition is a powerful and interesting process that can be applied in numerous fields. Films and powders can be synthesized at a low temperature by electrodeposition because of the high energy density accumulated in solution near the electrode surface. The advantages of electrodeposition compared with other techniques include low process temperature, low cost for raw materials and equipment, capability of controlling composition and morphology by electrochemical parameters, and the ability to deposit films on a complex surface. Electrodeposition has already been commonly employed to prepare metallic coatings for more than one hundred years. In recent years, metal oxides synthesized by electrodeposition including zinc oxide, 1,2 zirconium oxide, 3 bismuth oxide, 4 tungsten oxide, 5 and metal oxide composites 6 have been an active research area. In particular, through proper parameter control, deposited materials from nanostructured coatings to even epitaxial films 7 with superior properties can also be achieved.Tin oxide is one of the ceramic materials that is widely used because of its excellent properties for catalysis, gas sensor as anode materials of secondary lithium batteries, and as transparent conductive films for displays and solar cells. The interesting characteristics and related applications were dominated by several factors, such as morphology, grain size, crystallinity, and so on. For the electrodeposition of metal oxides, it is necessary for the hydroxyl ions or O Ϫ radicals to be present near the electrode surface. Previous research reported several oxygen sources, including hydrogen peroxide, 2 nitric acid, 1 and blown oxygen, 8 which are the necessary components for electrodepositing metal oxides. If nitric acid is chosen as the oxygen source, the half-reaction on the cathode electrode surface is expressed as follows 9The hydroxyl groups are formed on the electrode surface and contact with metal ions coming from the solution to synthesize metal hydroxide or metal oxide according to Reaction 3Because of low solubility, the metal hydroxide precipitates on the electrode surface rapidly. If the deposition temperature is higher than a critical temperature, metal hydroxide dehydrates and then metal oxide is synthesized. Because Sn is an amphoteric element, 10 stannic or stannous ions react with hydroxyl g...
