US researchers make conductive thin film breakthrough

The group says that the technology could enable a simpler and cheaper manufacturing process and is already at the performance level for application in resistive touch screens. The team created conductive ITO films 146 billionths of a metre thick that allowed 93% of light to pass through, a transparency said to be comparable to the glass plates they were deposited on. The films were also made on top of bendable polyimide, showing that they could potentially be useful for making flexible displays. To make the films, the team synthesized nanoscale ITO crystals in a solution which they then dripped onto a glass plate followed by a process called spin casting. From there they baked the coated plates for several hours and then tested their transparency and conductivity. Spin casting is said to be a very simple process, but finding the chemistry to allow it to produce a high performance ITO is more difficult. The researchers said the biggest achievement was finding the materials needed to make the nanoscale ITO crystals in the first place. The best chemicals were found to be indium acetylacetonate and tin bis(acetylacetonate)dichloride, which synthesised ITO nanocrystals about 11 billionths of a metre in diameter. The result was a dense but evenly distributed array of crystals, which promotes conductivity. "The next step is to improve conductivity to a magnitude commensurate with sputtered ITO while realising the reduced cost and process efficiency benefits expected of a solution based ITO deposition method," said Melissa Petruska, senior scientist at ATMI.