Indium tin oxide thin films elaborated by sol-gel routes: The effect of oxalic acid addition on optoelectronic properties

Single layer indium tin oxide (ITO) thin films were deposited on glass using modified sol-gel formulations. The coating sols were prepared using indium (InCl3 center dot 4H(2)O) and tin salts (SnCl4 center dot 5H(2)O). The stable sols were obtained using ethanol (C2H5OH) and acetylacetone (C5H8O2) as solvents and by the addition of oxalic acid dihydrate (C2H2O4 center dot 2H(2)O) in different amounts. The effect of oxalic acid content in the sol formulation and post-coating calcination treatment (in air at 300-600 degrees C) on electrical/optical properties of ITO films have been reported. It was shown that film formation efficiency, surface coverage and homogeneity were all enhanced with oxalic acid addition. Oxalic acid modification also leads to a significant improvement in electrical conductivity without affecting the film thickness (45 +/- 3 nm). ITO films exhibiting high transparency (approximate to 93%, visible region) with a sheet resistance as low as 3.8 +/- 0.4 k Omega/sqr have been formed by employing coating sols with optimized oxalic acid amount. The mechanisms and factors affecting the functional performance of oxalic acid-modified films have been thoroughly discussed and related to the microstructural and chemical characteristic of the films achieved by oxalic acid addition. (C) 2013 Elsevier B. V. All rights reserved.