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High quality ITO thin films grown by dc and RF sputtering without oxygen
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High quality indium tin oxide (ITO) thin films were grown without oxygen by both dc and RF magnetron sputtering techniques on glass substrates. The effects of substrate temperature, film thickness and sputtering method on the structural, electrical and optical properties of the as-grown films were investigated. The results showed that the substrate temperature had substantial effects on the film properties, in particular on the crystallization and resistivity. When the substrate temperature was increased to 150 °C, crystallization in the (2 2 2) plane started appearing for both dc and RF sputtered films. We additionally found that with further increments of substrate temperature, the preferred crystallization orientation changed differently for dc and RF sputtered films. Optical transmission in the visible region for a film thickness of 70 nm was found to be above 85%. The bandgap was calculated to be about 3.64 eV for the substrate temperature of 150 °C for a 70 nm thick film. The value of the bandgap increased with respect to the increment in film thickness as well as substrate temperature. We also measured the temperature dependence of the resistivity and Hall coefficient of the films, and calculated the carrier concentration and Hall mobility. Very low room temperature resistivities for dc and RF magnetron sputtered grown films of about 1.28 × 10-4 Ω cm and 1.29 × 10-4 Ω cm, respectively, were obtained. © 2010 IOP Publishing Ltd.