Delving into the electrical and optical properties of phase-change materials has unveiled a new way to develop flexible, thin-film displays with extremely high resolution and low energy consumption. A team at the University of Oxford found that by putting a 7-nm-thick layer of phase-change material between two layers of a transparent electrode, a tiny current can be used to draw images within the stack. In this case, the phase-change material was germanium-antimony-tellurium (GST), which can convert from an amorphous to a crystalline state. The electrode was made of indium tin oxide. These tiny stacks can be turned into 300 × 300-nm pixels, the researchers said. The nanopixels can draw images 70 µ wide. Courtesy of the University of Oxford. “We didn't set out to invent a new kind of display,” said Dr. Harish Bhaskaran, a professor in Oxford University's Department of Materials. “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,” Bhaskaran said. “Because the layers that make up our devices can be deposited as thin films, they can be incorporated into very thin, flexible materials.” The researchers were able to tune the nanopixel prototypes to create any color, including the primary colors that are needed for displays. Unlike conventional LCD display screens that require all pixels to constantly refresh, “you would only have to refresh those pixels that actually change — static pixels remain as they were,” said Dr. Peiman Hosseini, a postdoctoral researcher with Oxford’s Department of Materials. “This means that any display based on this technology would have extremely low energy consumption,” he added. The researchers also found that flexible, paper-thin displays based on the new technology could switch between a power-saving color e-reader mode and a backlit display capable of showing video. Such displays could be manufactured using inexpensive materials, they said. The new nanopixel technology also could be used in smart glasses, foldable screens, windshield displays and even synthetic retinas, they added. The work was funded by the UK’s Engineering and Physical Sciences Research Council, and was published in Nature (doi: 10.1038/nature13487). For more information, visit www.ox.ac.uk.