Carbon nanotubes grown on Cu
nanowires grown on carbon nanotubes
Schematic illustration of carbon
nanowalls filled by 20nm Fe particles
Assoc Prof YH Wu has succeeded in growing and observing
the first two- dimensional carbon nanostructures - dubbed
carbon nanowalls. We believe this is a world first.
nanowalls which are aligned almost vertically on the
substrates exhibit a lateral dimension of 0.1 to several
microns and a thickness of several nanometers. In the
nanoworld, both the dimension and dimensionality play
important roles in determining the properties of the
materials. The lowest dimensionality for a material is called
zero-dimensional, or simply 0D, which refers to the situation
that the movement of both electrons and atoms are confined by
a "sensible" boundary from every directions.
existence of boundaries will not be "felt" by the electrons or
atoms, however, when the dimension of the material is large.
This is just like the situation that the water inside the sea
far away from the coast can hardly sense the existence of the
coast, but the water everywhere inside a small basket can feel
the existence of the latter. That explains why both the
dimensionality and dimension are important. The most typical
carbon in the 0D form is the buckminsterfullerene, in which
the carbon atoms are arranged into a shape of soccer ball.
After the discovery of buckminsterfullerene by Kroto
and Smalley, Iijima discovered the one-dimensional carbon
nanostructures - carbon
nanotubes. The successful growth of carbon nanowalls makes
it possible for the first time to grow carbon nanostructures
in all three dimensionalities, i.e., from 0D to 2D.
The work has been started as a small project at the Data
Storage Institute to explore the possibility of using carbon
nanotubes in probe recording and nano-memories.
The nanowall was found accidentally during the process of
refining the nanotube structures. After the first finding, a
detailed study of the growth mechanism has been carried out,
and we are now able to grow both the nanotubes and nanowalls
in a well-controlled fashion. In addition to the bare carbon
nanowalls, a class of nanostructured materials using carbon
nanowalls as the templates has also been fabricated and their
potential applications in several strategic areas are being
explored. Following are some scanning electron microscopy
images of carbon nanotubes, nanowalls and the associated
Publications: Y.H. Wu and T.C. Chong, paper
presented at the MRS 2001 Spring Meeting, abstract No. W8.3,
San Francisco, USA, April 16-20, 2001. Y.H. Wu, P.W. Qiao,
T.C. Chong, Z.X. Shen, Adv.Mater.14, 64 (2002). Y.H. Wu, P.W.
Qiao, J.J. Qiu, T. C. Chong, and T. S. Low, Nano Letters 2,
161 (2002). Y.H. Wu and B.J. Yang, Nanoletters, Articles ASAP,
released on January 24, 2002. Y.H. Wu, B. J. Yang, G.C. Han,
B.Y. Zong, H.Q. Ni, P. Luo, T. C. Chong, T.S. Low, Z. X. Shen,
Accepted by Advanced Functional Materials.