Thin films of indium tin oxide (ITO) are of interest because of their high transparency and low electrical resistivity. Applications include use as electrodes for liquid crystal display and as heat mirrors for solar energy devices. We have developed totally aqueous routes to indium oxide (IO) and ITO materials because, (1) the particulate sols afford a longer shelf life than for alkoxyide derived materials, (2) organics do not have to be removed from the films by baking, and (3) the starting materials are cheaper than the corresponding alkoxides. Indium and mixed indium/tin sols have been prepared form inorganic solutions and treated with alkali to produce white thixotropic sols ca. 0.64 in Mz+ ions. This films were prepared by spinning on low iron or pure silica slides previously cleaned with DECON and washed with distilled water. Films were subsequently heated at 773K in air, or 1173K in air or nitrogen. The film with the lowest resistivity contained ca. 5 percent Sn and had an average optical transmittance between 400 and 600nm of 95 percent. The film was non-porous, smooth in texture, approximately 300nm thick and had a band gap energy of 3.22eV.
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