An Introduction to Indium Tin Oxide

From flat screen TVs and smart phone touch screens, from computer monitors, LCD displays and solar cells, just about everything we know and use on a daily basis utilises indium, an element many have never even heard of.

About Indium

Indium is an element belonging to the basic family as aluminium. The main difference between these two elements is the fact that aluminium is the earth crust’s most abundant metal, while indium occupies position 61 in the ‘abundance league table’ of elements.

Discovery of Indium

This rare element was discovered in 1863 by German chemists Hieronymus Richter and Ferdinand Reich who, after isolating a yellow powder extracted from sphalerite (zinc ore), tested the powder with a flame. On analysing the light created in the process, Richter and Reich discovered a very distinctive, indigo coloured band within the spectrum that bore no known relation to any other, previously known element. Indium was subsequently named after this indigo spectral line.

Extraction of Indium

With actual indium ore being extremely rare and of no significant commercial value, indium is usually obtained as an extraction by-product when extracting lead and zinc from their ores, which may contain up to one percent of indium. The resulting impure indium is then purified via electrolysis.

Indium Properties

Almost unique among elements and the most abundant of isotopes, indium has stable isotopes; its atomic mass number is 115 and it is very mildly radioactive (although it has a half-life that is several thousand times longer than the universe’s present age). One of this rare metal’s more unusual properties is the fact that when it is bent, it will emit an audible squeak.

Indium Applications in Technology

During WWII, for instance, thin, lubricating films of indium were used on aircraft engine’s bearings. Condensed onto glass surfaces, indium also makes high quality mirrors. It can also be used to produce lead-free solder; in sprinkler systems and in alloys with low melting points. Liquid down to temperatures of -19 degrees C, an indium, tin and gallium (another relative of aluminium) alloy is used in thermometers and liquid mirror telescopes as a non-toxic substitute for mercury.

Modern Technology

Today’s semiconductor technology (and in particular communications) has developed new applications for indium, including LEDs (light emitting diodes), which utilise indium and gallium alloys with either phosphorus or nitrogen, and CIGS semiconductors with indium-copper-gallium-selenium combinations for flexible thin-film solar cells.

Indium Tin Oxide

Used since the early part of the 20^th Century, the most commonly applied form of indium is, however, indium tin oxide, or ITO. Consisting of 10 per cent tin oxide and 90 per cent indium oxide, ITO is conductive and transparent. This virtually unique combination of conductivity and transparency has led to indium tin oxide being used extensively as flat-screen TV and LCD (liquid crystal display) electrodes. Here, every pixel (consisting of light-absorbing material) is sandwiched between ITO electrodes, which assists in the conversion of light energy to electricity. The touch screens of new generation e-readers and mobiles also use ITO coatings.

Indium Tin Oxide Coatings

Typically applied by vapour or sputter deposition technologies, ITO coatings have excellent electronic, optical and optoelectronic properties, making them ideal for use in a broad range of applications, including:

• Electrochromic and electroluminescent displays
• Energy efficient windows
• Field emission displays
• Gas sensors
• Heat reflective coatings
• LCD displays
• Photovoltaics
• Plasma displays
• Touch panels/screens and more

Recognised as a leading manufacturer of top quality vacuum coatings, innovative and eminently experienced in the deposition of ITO coatings onto a variety of substrates, Diamond Coatings supply a broad range of ITO coated products, from ITO cover slips, EMI/RFI shielding and heated electronic display filters to electrostatic protection; active touch screen components, ITO coated films and more.

Contact us

For more detailed information on ITO coatings and our extensive range of products, please peruse our pages and/or contact us online, by calling Tel.: +44 (0) 121 550 9430 or +44 (0) 8451 360 603 (Local Rate) or e-mailing us at: enquiries@diamondcoatings.co.uk now.