Squeezing graphene produces ‘diamondene’
Diamonds are going 2-D. The superhard form of carbon can be forged in thin films known as diamondene, new evidence suggests. While graphite, the form of carbon found in pencils, can be made into atom-thick sheets known as graphene, scientists have struggled to create two-dimensional films of its relative, diamond.
When a pair of graphene sheets are squeezed to pressures around tens of thousands of times that of Earth’s atmosphere, the crystal structure appears to change, hinting that it has morphed from graphite to diamond. Physicist Luiz Gustavo Cançado of the Universidade Federal de Minas Gerais in Belo Horizonte, Brazil, and colleagues report the new finding July 21 in Nature Communications.
“It’s the thinnest possible diamond,” says theoretical physicist Pavel Sorokin of the National University of Science and Technology MISiS in Moscow, who was not involved in the new study. Diamond is known for being extremely hard and stiff, he says, and “now we can use the exciting properties of diamond in the nanoworld.” Diamondene is also predicted to be magnetic and may be useful for spintronics, a technique that uses the spin of electrons to store data.
The scientists monitored the structure of the carbon crystal using a technique called Raman spectroscopy, shining laser light on the material to observe how the atoms’ vibrations changed under pressure (SN: 8/2/08, p. 22). This method provides indirect evidence that diamondene has formed. A next step is to scatter X-rays or electrons off the material to be sure of its structure.
Under pressure, two sheets of graphene, (illustrated at left, with carbon atoms in gray) combine into a single sheet of diamondene (right). Atoms of hydrogen (blue) and oxygen (red) come from water used to transmit the squeezing forces to the graphene.
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