It may have won its discovers the Nobel prize, but graphene now has a serious rival.
鈥淧hosphorene鈥� 鈥� which has a similar structure to carbon-based graphene but is made of phosphorus atoms 鈥� is a natural semiconductor and so may be better at turbocharging the next generation of computers. The new material has already been used to make rudimentary transistors.
Discovered 10 years ago, graphene is a form of pure carbon just a few atoms thick. This thinness causes electrons to zip across it much faster than they do across silicon, the material at the heart of today鈥檚 computer chips. So the hope is that graphene chips could eventually replace silicon, leading to much faster computers.
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But graphene has a fundamental limitation, says at Purdue University in West Lafayette, Indiana. It conducts electricity a little too well.
Sticky tape
By contrast, silicon is a semiconductor, meaning it can be made to conduct electricity 鈥� or block its flow. This switching capability is the defining feature of transistors and makes possible the binary logic at the heart of a computer chip. 鈥淏ecause of that I don鈥檛 think graphene can really compete with silicon for integrated circuits,鈥� says Ye.
Enter phosphorene, which is ultra-thin like graphene but made of phosphorus atoms instead. Most exciting of all, like silicon, it is a natural semi-conductor. Ye, who has spent many years studying graphene, discovered the stuff after a tip-off. 鈥淥ne of my colleagues mentioned that there is a form of phosphorus called black phosphorus that might be a layered structure,鈥� he says. 鈥淲hen I looked up , within about 30 minutes I knew that it had potential.鈥�
Ye and his colleagues found that they could use ordinary sticky tape to peel away sheets just a few atoms thick from black phosphorus crystals. The same technique was famously used to peel graphene sheets from chunks of graphite 鈥� the material used to make pencil lead. 鈥淲e call it the Scotch tape technique 鈥� it鈥檚 very low-tech,鈥� says Ye.
The researchers have already fashioned simple transistors out of thin layer phosphorene, and .
Suicidal silicene
Phosphorene seems to be gaining momentum. has also been done by of Fudan University in Shanghai, China, and colleagues.
of the University of Maryland in College Park says that phosphorene鈥檚 natural semiconductor properties give it an edge over graphene. 鈥淭hat鈥檚 something that cannot yet be easily done using graphene.鈥�
Whether phosphorene can compete with silicon has yet to be seen, particularly as it is unclear how to reliably produce the larger sheets that would be required for applications. 鈥淥bviously, technology cannot depend on Scotch tape extraction,鈥� says Das Sarma.
Phosphorene seems to have advantages over rival thin-layered materials. Silicene, which consists of super-thin layers of silicon for example, is a semi-conductor like phosphorene and in theory may conduct electricity particularly efficiently, like graphene. But it is harder to make than phosphorene or graphene. You can鈥檛 just peel layers of it off a chunk of silicon 鈥� and .
And is a proposed ultra-thin material made of tin atoms that might have similar properties to graphene, but as yet it only exists only in simulation.
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