By Eye² Staff
A new discovery will make it possible to create pixels just a few hundred nanometers across that could pave the way for extremely high-resolution and low-energy thin, flexible displays for applications such as 'smart' glasses, synthetic retinas, and foldable screens.
A team led by Oxford University scientists explored the link between the electrical and optical properties of phase change materials (materials that can change from an amorphous to a crystalline state). They found that by sandwiching a seven-nanometer thick layer of a phase change material (GST) between two layers of a transparent electrode they could use a tiny current to 'draw' images within the sandwich 'stack'.
Initially still images were created using an atomic force microscope but the team went on to demonstrate that such tiny 'stacks' can be turned into prototype pixel-like devices. These 'nano-pixels'—just 300 by 300 nanometers in size—can be electrically switched 'on and off' at will, creating the colored dots that would form the building blocks of an extremely high-resolution display technology.
A report of the research was published last month in
"We didn't set out to invent a new kind of display,' said Professor Harish Bhaskaran of Oxford University's Department of Materials, who led the research.
"We were exploring the relationship between the electrical and optical properties of phase change materials and then had the idea of creating this GST 'sandwich' made up of layers just a few nanometers thick. We found that not only were we able to create images in the stack but, to our surprise, thinner layers of GST actually gave us better contrast. We also discovered that altering the size of the bottom electrode layer enabled us to change the color of the image."
Although the work is still in its early stages, realizing its potential, the Oxford team has filed a patent on the discovery with the help of Isis Innovation, Oxford University's technology commercialization company. Isis is now discussing the displays with companies who are interested in assessing the technology, and with investors.
The layers of the GST sandwich are created using a sputtering technique where a target is bombarded with high energy particles so that atoms from the target are deposited onto another material as a thin film.
"Because the layers that make up our devices can be deposited as thin films they can be incorporated into very thin flexible materials—we have already demonstrated that the technique works on flexible Mylar sheets around 200 nanometers thick," said Professor Bhaskaran. "This makes them potentially useful for 'smart' glasses, foldable screens, windshield displays, and even synthetic retinas that mimic the abilities of photoreceptor cells in the human eye."
Still images of a tiger and a butterfly drawn with the technology are pictured above. At around 70 micrometers (70,000 nanometers) across each image is smaller than the width of a human hair. Oxford University researchers have shown that using this technology they can create 'nano-pixels' just 100 nanometers in size.
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