Amid a revolution in low-energy lighting, some scientists are returning to older ways of thinking. Now, graphene has been turned into a working filament, lighting up when it's pumped with electricity.
A team of researchers from Columbia, Seoul National University and Korea Research Institute of Standards and Science report that they have been able to use a sheet of graphene as a filament. Holding a sheet of the supermaterial between two electrodes and passing a current through it, the team was able to light up the graphene.
Speaking to PhysOrg, Wang Fon-Jen, one of the researchers, explained that they'd "created what is essentially the world's thinnest light bulb." Shrinking a light source to the nano-scale is no mean feat, especially using the incandescent bulb model of a filament with electricity pumped through it. Usually, the temperatures required for a material to emit visible light — thousands of centigrade — cause the small-scale samples to tear themselves apart.
But if there's one thing we known about graphene, it's that it's tough stuff. The researchers have shown in today's issue of Nature Nanotechnology that they're able to take a strip of graphene, held on a silicon substrate, to 2500C, in turn creating light. And despite the small scales involved — the sample of graphene used is smaller than the width of a human hair — the light it emits is visible to the naked eye.
The graphene can withstand these temperatures because as it gets warmer, it conducts heat less effectively. That means that the temperatures are confined to a small spot in the centre and don't reach the ends and edge of the sample, where they could bring the material to its knees. The researchers explain that the new findings could allow them to build tough, flexible optical displays, or chips that use optical communication as well as electrical.
Perhaps the nicest aspect of the work, though, is how it echoes the past. When Thomas Edison first created the lightbulb, he used a piece of carbon as the filament. Now, the researchers have reduced that crucial component to just a single atom in thickness.