A process that uses vapor rather than liquid to grow designer crystals could lead to a new breed of faster, more powerful electronic devices. Until now the designer crystals known as metal organic frameworks (MOFs) could be grown and applied only using a liquid solvent. That made them largely unsuitable for electronics applications, says Commonwealth Scientific and Industrial Research Organization (CSIRO) researcher Mark Styles.

"Just like your smartphone doesn’t like being dropped in water, electronic devices don’t like the liquid solvent that’s used to grow MOF crystals," Styles says. It can corrode and damage the circuitry, he says.

The advance suggests that many more transistors may be fit onto a microchip, says Mark Styles. Image credit: CSIRO.The advance suggests that many more transistors may be fit onto a microchip, says Mark Styles. Image credit: CSIRO.The new process, invented by an international team of scientists from the University of Leuven in Belgium, the National University of Singapore and Australia's CSIRO, uses a vapor method similar to steam hovering over a pot of hot water to grow the crystals. The team drew on specialist X-ray analysis techniques from CSIRO and the Australian Synchrotron to understand how the vapor process works and how it could be used to grow the MOF crystals.

On the atomic scale, MOF crystals resemble bird cages that can be made to be different shapes and sizes. They have a large surface area, meaning they can be up to 80% empty inside. The net result is a structure in which almost every atom is exposed to empty space: one gram of MOF crystals has a surface area of more than 5,000 square meters.

"Crucially, we can use this vast space to trap other molecules, which can change the properties of a material," says Styles. "In the case of electronics, this means we can fit a lot more transistors on a microchip, making it faster and far more powerful."

Styles says that another potential application for the technology is in portable chemical sensing devices that could be used in hazardous environments such as chemical processing plants and mines.

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