Transparent materials could lead to new display technologies including car windscreen head-up displays.

Clear vision for transparent circuitry

Researchers have found a simple and inexpensive way to make transparent electronic circuitry.

High-performance electronic circuits made from transparent materials could lead to a new generation of display technologies including head-up displays on car windscreens, transparent TV sets and smart windows in homes and offices, according to researchers at Saudi Arabia’s King Abdullah University of Science and Technology (KAUST).

The team behind the development has found a way to make transistors and other essential components of electronic circuitry transparent using inexpensive and readily available materials and a simple fabrication technique.

Indium tin oxide (ITO) is the current material of choice for electronics because it combines optical transparency with electrical conductivity. Its use ranges from touch-sensitive smartphone screens to light-harvesting solar panels. However, a promising alternative appears to be the transparent material aluminium-doped zinc oxide (AZO).

"The elements that make up this material are more abundant than indium, making AZO a commercially sensible option," said Professor Husam Alshareef from the KAUST Physical Science and Engineering Division, who also led the research. "However, electronic devices made using AZO have traditionally shown inferior performance to devices made using ITO."

To overcome this, Alshareef and his research team used atomic layer deposition. Volatile vapours of aluminium and zinc in the form of trimethyl aluminium and diethyl zinc are alternately introduced onto the transparent substrate, where they adhere to the surface in a single layer before reacting in situ to form 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," Alshareef explained.

Another advantage of this approach is that atomic layer deposition only requires a temperature of 160 degrees Celsius to form each layer, which is low enough for the transparent circuitry to be formed on flexible plastic substrates as well as on rigid glass.

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