This
visualisation shows layers of graphene used for membranes. Couuty: University
of Manchester.
A team of
researchers has amplified 3-D graphene's electrical properties by controlling
its curvature.
"Our
research showed the conservation and the degradation of the ultra-low
dissipative transport of Dirac electrons on the 3-D curved surface for the
first time," said Yoichi Tanabe, leading author of the study.
Graphene
is a 2-D atomic-layer material, shaped like honeycombs, which possesses
excellent electrical, chemical, thermal, and mechanical properties for a wide
range of applications such as semiconductors, electrical batteries, and
composites.
Graphene
sheets stacked together form graphite which makes up the lead in our pencils.
However, packing together graphene tightly means it loses its 2-D electronic
properties.
One way to
overcome this is to separate the graphene sheets with air-filled pores—like a
sponge—at the nanometer scale and make it into a three-dimensional structure.
This amplifies graphene's properties for practical purposes.
But doing
so is not without its challenges; converting 2-D graphene into 3-D graphene
introduces crystal defects and a host of other problems that cause it to lose
its desirable characteristics. Little is known about how the curved surface
degrades the graphene's electric transport properties and whether this is the
reason for graphene losing its Dirac fermions.
The
research team sought to investigate this by taking a single, 2-D graphene sheet
and folding it into a 3-D structure with a bicontinuous and open porous
structure.
The
structure, with a curvature radius down to 25-50 nanometers, retained the basic
electronic properties of 2-D graphene well. Meanwhile, the motion of electrons
on the 3-D curvature enhanced electron scattering that had originated from the
intrinsic curvature effects. In fact, nanoscale curvature provides a new degree
of freedom to manipulate graphene's electronic behaviors for the emergent and
unique electrical properties of 3-D graphene.