Probing the inner secrets of multi-layer carbon nanotubes

Apr 18, 2007

Researchers at the University of Surrey have shown for the first time that knowing the structure of the surface layer of a multi-layer carbon nanotube is not enough to predict its electronic properties. The contribution of inner layers is crucial, and this has serious implications when it particularly comes to fabricating electronic devices such as transistors and molecular interconnects.

The work reported in Nano Letters (DOI: 10.1021/nl070072p) addresses essential issues related to the electronic properties of carbon nanotubes, as an understanding of their behaviour at the atomic level is required to fully exploit the tremendous opportunities that these systems could offer in the development of practical nanoscale devices.

Single wall carbon nanotubes can be regarded as individual sheets (one atom thick) of graphite which are wrapped up to form tubes. It is the diameter of the tube and the degree of helicity in this wrapping which determine the electronic properties. Different configurations can result in the tube behaving either as a metallic conductor or as a semiconductor, and this theoretically-predicted relationship between the structure and electronic properties has been confirmed using scanning tunnelling microscopy.

It is also possible to form multi-wall nanotubes comprising several tubes, one inside another (like layers of an onion, or a set of Russion dolls). Whereas single-walled carbon nanotubes have been researched and well characterised for many years now, less is known about the multi-wall tubes. How strong is the electrical coupling between layers? How does the helicity of the inner layers affect electrical conduction of the multi-wall tube?

The experiments carried out at the University of Surrey used scanning tunnelling microscopy of double-walled carbon nanotubes to demonstrate an explicit correlation between the helicity of the constituent tubes, their electronic coupling and the overall electronic structure. Cristina Giusca, the lead author of the paper said: "The work is of fundamental importance to the carbon community as it shows the first evidence for a direct correlation between the electronic properties of multiwall carbon nanotubes and the diameter and chiral indices (helicity) of the inner shells".

Professor Ravi Silva, who leads the Advanced Technology Institute at the University of Surrey, indicated that "This is a fine example of the cutting edge research undertaken at the Institute which combines the very best in fundamental research with sound theoretical backing. The work is of crucial importance to all of us conducting research in carbon nanotubes and other forms of quantum transport studies in 1D structures which clearly highlights the importance of the electronic interaction between adjacent layers, which were previously considered to be less important. This work will add new vigour to those examining the use of carbon nanotubes for interconnects in the IC industry. Having only metallic carbon nanotubes may now not be necessary in the design of interconnect wires between semiconductors if multi-walled nanotubes are to be used for this application."

Source: University of Surrey

Explore further: Chemically driven micro- and nanomotors

add to favorites email to friend print save as pdf

Related Stories

Defects are perfect in laser-induced graphene

Dec 10, 2014

Researchers at Rice University have created flexible, patterned sheets of multilayer graphene from a cheap polymer by burning it with a computer-controlled laser. The process works in air at room temperature ...

Researchers take first pictures of baby nanotubes

Dec 02, 2014

Single-walled carbon nanotubes are loaded with desirable properties. In particular, the ability to conduct electricity at high rates of speed makes them attractive for use as nanoscale transistors. But this ...

Recommended for you

Chemically driven micro- and nanomotors

22 hours ago

At least since the movie "The Fantastic Voyage" in 1966, in which a submarine is shrunk down and injected into the blood stream of a human, people have been toying with the idea of sending tiny "micromachines" ...

Pyramid nanoscale antennas beam light up and down

Dec 17, 2014

Researchers from FOM Institute AMOLF and Philips Research have designed and fabricated a new type of nanoscale antenna. The new antennas look like pyramids, rather than the more commonly used straight pillars. ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.