Researchers Develop See-Through Circuitry

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As an result of the increase in the prices of indium, researchers have developed a technique that uses aluminum-doped zinc oxide, which is a cheaper alternative effectively used for transparent electronics.

High-performance electronic circuits developed completely from transparent materials could have limitless applications, starting from head-up displays on car windscreens to transparent TV sets and smart windows in offices and homes.

KAUST researchers have discovered a way to develop transparent transistors and various other important components of electronic circuitry using a simple fabrication technique and materials that are cost-effective and readily available.

Indium tin oxide (ITO) is the currently available material of choice for electronics as it incorporates optical transparency with electrical conductivity.

ITO is used in touch-sensitive smartphone screens, light-harvesting solar panels and various other similar applications. However, indium is in short supply and the demand for it increases resulting in price increase.

Aluminum-doped zinc oxide (AZO) is a transparent material that is considered to be a promising cost-effective ITO alternative.

The elements that make up this material are more abundant than indium, making AZO a commercially sensible option. However, electronic devices made using AZO have traditionally shown inferior performance to devices made using ITO.

Professor Husam Alshareef, KAUST

Alshareef and his team of researchers overcame this limitation by using a high-precision technology known as atomic layer deposition, which is a technique in which the circuitry is made up of a single layer of atoms at a time.

Volatile vapors of zinc and aluminum in the form of diethyl zinc and trimethyl aluminum were introduced in an alternate manner onto a substrate, where they stick to the surface in a single layer before reacting in situ to develop AZO.

Using atomic layer deposition to grow all active layers simplifies the circuit fabrication process and significantly improves circuit performance by controlling layer growth at the atomic scale.

Professor Husam Alshareef, KAUST

The thin film transistor is the main component for a number of electronic devices. When integrated in huge numbers, these devices permit computers to carry out calculations, act as active sensors and drive displays.

Hafnium oxide, a transparent material, was used by Alshareef to develop the highly-stable transistors capable of fabricating the transparent circuits. Hafnium oxide was sandwiched between zinc oxide layers.

Our transistor properties are the best reported so far for fully transparent transistors using AZO contacts.

Zhenwei Wang, Ph.D. Student, KAUST

Alshareef’s approach was considered to be even more beneficial as the atomic layer deposition only needs a temperature of 160 degrees Celsius to develop each layer, which is low enough such that transparent circuitry can be produced on flexible plastic substrates and also on rigid glass.

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