graphene. It’s the first time anyone has been able to do this, and opens a new class of materials that scientists can work with.

Graphene building

Just as in the construction industry, foundation is everything when it comes to building with graphene. Left to its own devices, a graphene sheet will wrinkle like poorly torn plastic wrap. Some researchers try to get around this by suspending graphene on clips in air, like a piece of laundry hanging out to dry. Even then, though, the edges will ripple or roll themselves up, or the sheet itself will tear. So scientists are investigating new ways to lay graphene flat and keep it that way.

Early on, most research teams plopped some graphene on a slab of silicon dioxide, the stuff of everyday computer chips. But the silicon and oxygen atoms interfered with the way the graphene’s electrons zipped along. Instead, scientists have now switched their foundations to boron nitride, the stuff used to add glitter to cosmetics. Like graphene, boron nitride also has its atoms arranged in a single hexagonal sheet, with boron and nitrogen alternating in the spaces where carbon atoms sit in graphene. It’s an almost perfect match.

“Once you use a boron nitride substrate and stack it with graphene, a number of things change,” says Philip Kim, a physicist at Columbia. Compared with silicon dioxide, boron nitride lets the electrons zip along without interference, Kim and his colleagues showed last year.

To see why boron nitride works so well, scientists at UC Berkeley and the Lawrence Berkeley lab recently took a closer look at what happens when graphene and boron nitride meet. Using a scanning tunneling microscope, which can see at the level of individual atoms, the team compared graphene mounted on silicon dioxide with graphene mounted on boron nitride. The silicon dioxide version turned out to be strewn with “charge puddles,” or spots where the electron flow got hung up. In contrast,

The first integrated circuit made fully
from graphene (yellow design, bottom;
close-up, top) could herald a new age
of graphene electronics.

the boron nitride samples were practically puddle-free. Michael Crommie, Alex Zettl and colleagues reported the findings this year in Nano Letters.

With this solid foundation and new ways of stacking, researchers can now act as architects, designing devices that take advantage of graphene’s protean qualities. Though it probably won’t ever replace the industry standard of silicon, graphene could lead to new kinds of gadgets. “It’s really about what we can gain by using graphene in different applications,” Castro Neto says.

Already, the wonder sheets are mak-
ing inroads into silicon’s traditional
territory. In June in Science, IBM
scientists reported making an integrated
circuit whose components, including a
transistor, are made completely out of
graphene. Other teams have made indi-
vidual graphene components before,
and even linked hundreds of transis-
tors together on a single chip. But the
IBM group, led by Phaedon Avouris
at IBM’s Watson Research Center in
Yorktown Heights, N.Y., is the first to
make a complete circuit entirely out of
graphene. Because graphene is so cheap,
these kinds of circuits could prove
popular for use in smartphones and
other portable devices.