An international team of researchers has developed a new magnetic carbon material that not only acts as a semiconductor but is also magnetic and could help scientists develop the next generation of microelectronic devices.
The new carbon material is based on graphene, which resembles graphite, the form of carbon found in pencil “lead”, but which exists as single sheet-like layers resembling nanoscopic chicken wire fencing. Graphene was first created by scientists in Manchester five years ago and is not only 200 times stronger than steel but because its electrons are highly mobile it has unique electro-optical properties. As such, some researchers think that graphene is the natural successor to silicon and could lead to the advent of spintronic devices that exploit electron spin and charge in computer memory and data processing.
Now, researchers from the Virginia Commonwealth University, USA, Peking University in Beijing, China, the Chinese Academy of Science in Shanghai, and Tohoku University in Sedai, Japan have used computer modelling to design a chemical cousin of graphene, which they call graphone. Experiments with the new material confirm the electromagnetic properties predicted by the computer models.
The team points out that while the properties of graphene can be modified relatively easily by introducing “defects” into its structure or by saturating it with hydrogen atoms, it has not proven easy to make it magnetic.
“The new material we are predicting – graphone – makes graphene magnetic simply by controlling how much hydrogen is put on graphene,” explains VCU’s Puru Jena. “One of the important impacts of this research is that semi-hydrogenation provides us a very unique way to tailor magnetism,” adds team member Qiang Sun, “The resulting ferromagnetic graphone sheet will have unprecedented possibilities for the applications of graphene-based materials.”
The team explains that graphene undergoes a transition from its original “metallic” state to semiconductor when all the carbon valencies are fully hydrogenated, to make graphane. However, density functional theory predicted that half hydrogenation (to make graphone) would result in a ferromagnetic semiconductor with a small indirect gap. This they confirmed experimentally.
“From graphene to graphane and to graphone, the system evolves from metallic to semiconducting and from nonmagnetic to magnetic. Hydrogenation provides a novel way to tune the properties with unprecedented potentials for applications,” the team says.
Further Reading
Nano Lett, 2009, in press