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Single atoms viewed thanks to super-material
July 21, 2008
World Science staff
A material that has become one of the hottest subjects of physics research has yielded two surprising new findings, scientists say. Individual atoms of hydrogen
and carbon (courtesy Zettl et al./Nature) Diagram of a graphene
layer poked by a diamond tip (courtesy Science)
First, the material, graphene, has let experimenters create the first images of small, individual atoms such as hydrogen. As if that weren’t enough, a second group of scientists claims graphene is the strongest material known, adding to its already record-breaking status as the thinnest.
Graphene is an ultra-thin—just one atom thick—layer of ordinary graphite, the form of carbon used as the writing material in pencils.
Graphene grabbed the scientific community’s attention starting in 2005 when researchers reported exotic electronic behavior in the material.
For instance, in graphene, electrons—the subatomic particles that carry electric charge—act as though they are weightless.
Graphene’s surprising attributes have made researchers view it as a possibly ideal material for use in minuscule electronic devices.
In a paper in the July 17 issue of the research journal Nature, scientists reported that graphene had allowed them the unusual achievement of imaging single small atoms.
A device known as the transmission electron microscope has revealed a wealth of important features at a scale nearly that small, but but catching a glimpse of lightweight individual atoms such as hydrogen and carbon has been beyond its grasp. The difficulty arises because their signals are drowned out by background signals from whatever is around and behind the atoms.
Alex Zettl of the University of California, Berkeley and colleagues reported in the
Nature paper that they had solved the problem by using a single-layer sheet of graphene as a support material. Graphene is all but invisible under the microscope, they explained, thanks in part to its near-perfect uniformity.
As a result, individual hydrogen and carbon atoms under the microscope appeared as though suspended in space, the researchers
said. These atoms could also be watched as they interacted with occasional irregularities that arose in the graphene structure. This means the new technique could be used for deeper study of graphene itself, Zettl and colleagues
argued.
In a second paper published in the July 18 issue of the journal Science, Changgu Lee of Columbia University in New York and colleagues poked at stretched-out layers of graphene with a sharp diamond tip to determine its stiffness. “These experiments establish graphene as the strongest material ever measured,” they wrote, thanks again to the extraordinary uniformity of its structure and to the strength of the bonds between its atoms.
Graphene is a single layer of carbon atoms arranged in hexagons, like a sheet of chicken wire with an atom at each nexus. As free-standing objects, such two-dimensional crystals were believed impossible to create until physicists at the University of Manchester, U.K. actually made
graphene in 2004.
The familiar pencil-lead form of carbon, graphite, consists of layers of carbon atoms tightly bonded in flat sheets, or planes, but only loosely bonded between those planes. Because the layers move easily over one another, graphite is a good lubricant. In fact these graphite layers are
graphene. After its discovery, research immediately took off, inspired by the material’s unexpected electronic properties. Experiments continue unabated.
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A material that has become one of the hottest subjects of physics research has yielded two surprising new findings, scientists say. First, the material, graphene, has allowed experimenters to create the first images of small, individual atoms such as hydrogen. As if that weren’t enough, a second group of scientists claims graphene is the strongest material known, adding to its already record-breaking status as the thinnest. Graphene is an ultra-thin—just one atom thick—layer of ordinary graphite, the form of carbon used as the writing material in pencils. Graphene grabbed the scientific community’s attention starting in 2005 when researchers reported exotic electronic behavior in the material. For instance, in graphene, electrons—the subatomic particles that carry electric charge—act as though they are weightless. Graphene’s surprising attributes have made researchers view it as a possibly ideal material for use in minuscule electronic devices. In a paper in the July 17 issue of the research journal Nature, scientists reported that graphene had allowed them the unusual achievement of imaging single small atoms. A device known as the transmission electron microscope has revealed a wealth of important features at a scale nearly that small, but but catching a glimpse of lightweight individual atoms such as hydrogen and carbon has been beyond its grasp. The difficulty arises because their signals are drowned out by background signals from whatever is around and behind the atoms. Alex Zettl of the University of California, Berkeley and colleagues reported in the Nature paper that they had solved the problem by using a single-layer sheet of graphene as a support material. Graphene is all but invisible under the microscope, they explained, thanks in part to its near-perfect uniformity. As a result, individual hydrogen and carbon atoms under the microscope appeared as though suspended in space, the researchers said. These atoms could also be watched as they interacted with occasional irregularities that arose in the graphene structure. This means the new technique could be used for deeper study of graphene itself, Zettl and colleagues said. In a second paper published in the July 18 issue of the journal Science, Changgu Lee of Columbia University in New York and colleagues poked at stretched-out layers of graphene with a sharp diamond tip to determine its stiffness. “These experiments establish graphene as the strongest material ever measured,” they wrote, thanks again to the extraordinary uniformity of its structure and to the strength of the bonds between its atoms. Graphene is a single layer of carbon atoms arranged in hexagons, like a sheet of chicken wire with an atom at each nexus. As free-standing objects, such two-dimensional crystals were believed impossible to create until physicists at the University of Manchester, U.K. actually made graphene in 2004. The familiar pencil-lead form of carbon, graphite, consists of layers of carbon atoms tightly bonded in flat sheets, or planes, but only loosely bonded between those planes. Because the layers move easily over one another, graphite is a good lubricant. In fact these graphite layers are graphene. After its discovery, research immediately took off, inspired by the material’s unexpected electronic properties. Experiments continue unabated.