Indium tin oxide
ITO
White to pale yellow solid
Fixed
7.12 g · cm -3 ( 25 ° C)
Insoluble in water
Attention
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Indium tin oxide (English indium tin oxide, ITO ) is a semiconducting, transparent in visible light largely fabric. It is a mixed oxide, usually from 90% indium (III ) oxide ( In2O3 ) and 10% tin (IV ) oxide ( SnO2 ).
Properties
Tin ( IV) oxide produced as the dopant required for a good electrical conductivity type impurity in the crystal structure of indium oxide. Thin layers of typically about 200 nm is deposited on the glass at temperatures of about 400 ° C, have a high transparency with a surface resistance of about 6 Ω.
Applications
The substance is used for the production of transparent electrodes in liquid crystal displays, organic light emitting diodes, and touch screens. Furthermore, it is used in thin-film solar cells as well as the wiring of semiconductor sensors. Since ITO infrared radiation strongly reflected, it is occasionally applied as thermal insulation on window glass. Likewise, a wide variety of surfaces, such as plastic films, are coated with ITO, so they do not become electrostatically charged. This is important in the packaging and storage of highly sensitive electronic components. Also, image sensors of high quality digital cameras are equipped with protective layers of indium tin oxide.
Coating process
ITO is commonly applied to substrates under high vacuum. Suitable substrates are glass and plastic films used. Sputtering is the process most widely used, but it can also be applied by thermal evaporation, said vaporized elements to up to 360 ° C have to be heated, which limits the applicability, especially in plastics. Also possible is the vapor deposition at room temperature, followed by aging in oxygen at 360 ° C and atmospheric pressure. See the layers after deposition of metallic and opaque. Only the oxidation gives them the desired properties of transparency and conductivity.
A further possibility is the sol -gel process, which can be used on thin, but large-scale layers. The substrates can be dipped, sprayed, printed or coated by spin coating. The disadvantage here is that for many applications (LCD and OLED) to low layer homogeneity.
Alternative materials in the semiconductor industry,
Due to the high price of indium, which have multiplied in recent years, is relatively expensive ITO. Quantities limited availability of indium is limited in the medium term, for example, the mass application in thin film solar cells. It is therefore working intensively on alternative transparent conductive coatings. Promising candidates are not limited to: