New phase of carbon used to make diamond at room temperature

Washington: Indian-origin researchers in US have discovered a new phase of solid carbon which is harder than diamond and can be used to make diamond-related structures at room temperature.

Graphite is one of the solid phases of carbon; diamond is another.

"We've now created a third solid phase of carbon," said lead author Jagdish Narayan, from North Carolina State University in US.

"The only place it may be found in the natural world would be possibly in the core of some planets," Narayan said.

The new phase of solid carbon, called Q-carbon, is harder than diamond, and glows when exposed to even low levels of energy.

"Q-carbon's strength and low work-function - its willingness to release electrons - make it very promising for developing new electronic display technologies," Narayan said.

Q-carbon can also be used to create a variety of single-crystal diamond objects.

Researchers started with a substrate, such as sapphire, glass or a plastic polymer. The substrate is then coated with amorphous carbon - elemental carbon that does not have a regular, well-defined crystalline structure.

The carbon is then hit with a single laser pulse lasting approximately 200 nanoseconds. During this pulse, the temperature of the carbon is raised to around 3,727 degrees Celsius and then rapidly cooled.

This operation takes place at one atmosphere - the same pressure as the surrounding air.

The end result is a film of Q-carbon, and researchers can control the process to make films between 20 nanometres and 500 nanometres thick.

By using different substrates and changing the duration of the laser pulse, the researchers can also control how quickly the carbon cools.

By changing the rate of cooling, they are able to create diamond structures within the Q-carbon.

"We can create diamond needles or micro needles, nanoneedles, or large-area diamond films, with applications for drug delivery, industrial processes and for creating high-temperature switches and power electronics," Narayan said.

"These diamond objects have a single-crystalline structure, making them stronger than polycrystalline materials," he said.

"And it is all done at room temperature and at ambient atmosphere - we're basically using a laser like the ones used for laser eye surgery," he said.

NC State has filed two provisional patents on the Q-carbon and diamond creation techniques.

The work is described in two papers published in the Journal of Applied Physics and the journal ALP Materials, both of which were co-authored by NC State PhD student Anagh Bhaumik.