Tin doped indium oxide (ITO) films are highly transparent in the visible region, exhibiting high reflectance in the infrared region, and having nearly metallic conductivity. Owing to this unusual combination of electrical and optical properties, this material is widely applied in optoelectronic devices. The association of these properties in a single material explains the vast domain of its applicability and the diverse production methods which have emerged. Although the different properties of tin doped indium oxide in the film form are interdependent, this article mainly focuses on the electrical aspects. Detailed description of the conduction mechanism and the main parameters that control the conductivity is presented. On account of the large varieties and differences in the fabrication techniques, the electrical properties of ITO films are discussed and compared within each technique.

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This article reports the fabrication of thin films of In2O3 from an aqueous sol and an organic solution. The stability of the aqueous sol with respect to the concentration of indium and pH are discussed. Thermo-gravimetric and differential thermal analysis were performed on the dried sol particles as well as the gel for better understanding of thermal events occurring during the sintering process. Microstructure, phase purity, optical, and electrical properties of the thin films deposited on glass substrates by dip-coating process from aqueous sol and organic solution were studied by transmission electron microscopy, x-ray diffractometry, visible light spectrometry, and the four-probe method, respectively. The electrical properties of the films derived from the two systems are discussed based on the differences in their morphologies.

The conduction mechanism in aluminum-doped zinc oxide has been studied. Structural investigation shows that crystallographic orientation as well as grain boundary scattering can be neglected. Based on the analysis of the Hall mobility, it has been found that scattering at neutral and ionized impurities dominates the mobility. Further improvement in the mobility can be achieved by lowering the density of neutral impurities through careful control of the film processing parameters.

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Hall effect measurements have been performed on tin-doped indium oxide thin films prepared by the dipping method. The apparent variation of electron mobility with carrier concentration in these films has been quantitatively interpreted in terms of scattering at charged and neutral impurities. An electrical resistivity as low as 3.2×10−4 Ω cm was obtained for the films doped with about 6 at. % Sn. A further increase in the doping content lead to the formation of neutral defects without contributing carriers to the material.

Thin films of dicadmium stannate spinel (Cd 2 SnO 4 ) were deposited on glass substrates using a dip-coating technique. The films were transparent to visible light (90%) and electrically conductive. X-ray diffractometry showed that annealed films consisted of a single cubic spinel phase only when they were prepared from a solution with the composition of Cd:Sn ‫؍‬ 2.5 and fired at a temperature of 400°-500°C. The Cd:Sn ratio, the firing temperature, and the post-deposition annealing sequence were crucial for the formation of a single phase, which is vital to obtain optimal optical and electrical properties. A resistivity as low as 3.3 ؋ 10 ؊4 ⍀⅐cm could be obtained after annealing.