PROVIDENCE, R.I. [Brown University] In a touch-screen display or a solar panel, any conductive overlay had better be clear. Engineers employ transparent thin films of indium tin oxide (ITO) for the job, but a high-tech material's properties are only half its resume. They must also be as cheap and easy to manufacture as possible. In a new study, researchers from Brown University and ATMI Inc. report the best-ever transparency and conductivity performance for an ITO made using a chemical solution, which is potentially the facile, low-cost method manufacturers want.
"Our technology is already at the performance level for application in resistive touch screens," said Jonghun Lee, a Brown chemistry graduate student and lead author of the paper posted online Aug. 1 by the Journal of the American Chemical Society.
The group made conductive ITO films 146 billionths of a meter thick that allowed 93 percent of light to pass through, a transparency comparable to the glass plates they were deposited on. The team also made their films on top of bendable polyimide, showing that it could potentially be useful for making flexible display technologies.
In several experiments they showed that by varying the thickness and the tin content (between 5 and 10 percent was best) they could vary the transparency and resistance to find the best combination.
"By controlling the concentration of the nanocrystal solution, we could control the thickness of the film from 30 nanometers to 140 nanometers," Lee said.
To make the films, the team synthesized nanoscale ITO crystals in a solution. Then they made a flat and smooth film of them by dripping the solution onto a glass plate followed by rapid spinning, a process called spin casting. From there they baked, or annealed, the coated plates for several hours (the best length of time turned out to be six hours) and then tested their transparency and conductivi
|Contact: David Orenstein|