Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Nanotubes form along atmoic steps

22.12.2004


The Weizmann Institute of Science today announced that a research group headed by Dr. Ernesto Joselevich has developed a new approach to create patterns of carbon nanotubes by formation along atomic steps on sapphire surfaces. Carbon nanotubes are excellent candidates for the production of nanoelectronic circuits, but their assembly into ordered arrays remains a major obstacle toward this application.



The team was initially researching in a different direction: they were trying to give carbon nanotubes (structures reminiscent of rolled-up sheets of graphite) a preferred orientation on a wafer by applying an electrical field as the tubes were being formed. This works very well with silicon dioxide wafers. On a sapphire support (sapphire is a form of aluminum oxide), on the other hand, it didn’t work: the nanotubes were beautifully arranged in parallel, but with an orientation that was completely independent of the electrical field – even when no field was applied at all.

Closer examination of the sapphire surface solved the mystery: commercial sapphire wafers are generally not cut exactly along the plane of the crystal. Their surface is thus not completely smooth; instead, it has parallel steps – of atomic dimensions – between the different planes of the crystal. The nanotubes wind up lying along these steps. The researchers explain it like this: the nanotubes form from a catalyst of iron nanoparticles and are attracted to a local field created by the steps. It is clear that these iron particles don’t like "climbing stairs;" instead, they "glide" along the inner edge of the step, as though on a track. Thus they remain continuously in contact with two surfaces, rather than just one, which seems to stabilize the catalyst. Just as an airplane leaves behind a condensation trail, the iron particles leave the newly formed nanotubes lying along their "tracks." The nanotubes even follow kinks in the steps, which are caused by defects in the crystal. This results in either straight or zigzag-shaped tubes, which are expected to have particularly interesting electronic properties.


"The orientation and form of the atomic steps on a crystal surface can be controlled by the cutting process, and defects can be created artificially," says Joselevich. "It should thus be possible to produce different nanowire arrangements in a controlled fashion."

Yivsam Azgad | EurekAlert!
Further information:
http://www.weizmann.ac.il

More articles from Physics and Astronomy:

nachricht Shape matters when light meets atom
05.12.2016 | Centre for Quantum Technologies at the National University of Singapore

nachricht Climate cycles may explain how running water carved Mars' surface features
02.12.2016 | Penn State

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

High-precision magnetic field sensing

05.12.2016 | Power and Electrical Engineering

Construction of practical quantum computers radically simplified

05.12.2016 | Information Technology

NASA's AIM observes early noctilucent ice clouds over Antarctica

05.12.2016 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>