Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Unusually long and aligned ’buckytubes’ grown at Duke

23.04.2003


Duke University chemists have developed a method of growing one-atom-thick cylinders of carbon, called "nanotubes," 100 times longer than usual, while maintaining a soda-straw straightness with controllable orientation. Their achievement solves a major barrier to the nanotubes’ use in ultra-small "nanoelectronic" devices, said the team’s leader.



The researchers have also grown checkerboard-like grids of the tubes which could form the basis of nanoscale electronic devices.

The accomplishment involved sprouting the infinitesimally thin structures, also called "single walled carbon nanotubes," or "buckytubes," from tiny catalytic clusters of iron and molybdenum atoms dotted onto a small rectangle of silicon inside a quartz tube.


These growing nanotubes continue to lengthen along the silicon’s surface in the direction of the flow of a feeding gas of carbon monoxide and hydrogen that had been quick-heated to a temperature hot enough to melt normal glass. Atoms from the feeding gas are used as molecular building blocks.

The process was described by Duke assistant chemistry professor Jie Liu, his senior research associate Shaoming Huang and his graduate student Xinyu Cai in an article posted Tuesday, April 22, 2003 in the on-line edition of the Journal of the American Chemical Society (JACS). Their research was funded by NASA, the Army Research Office and Dupont.

"To the best of my knowledge these are the longest individual single-walled carbon nanotubes ever recorded, although we removed that ’longest’ statement from our paper because you can never claim longest forever," Liu said.

"In our paper, we claimed lengths of more than 2 millimeters, but in our own lab we are now growing 4 millimeter long nanotubes," he added in an interview. "We may get even longer nanotubes later on."

Nanotube lengths are normally less than 20 millionths of a meter, their JACS report said -- about 100 times shorter than the ones Liu’s team is making. If its girth could somehow be bloated to a 1-inch diameter, then a 2-millimeter-long nanotube’s length would extend proportionally to more than 31 miles, Liu estimated.

After learning they could grow the very long and straight nanotubes, the researchers then discovered they could form cross-connecting nanotube grids as well. They formed the grids by growing additional nanotubes in perpendicular directions under the guidance of a reoriented feeding gas flow.

Such grid patterning could form the basis for billionths-of-a-meter scale electronic circuitry, Liu said. Exceptionally lengthy nanotubes could also be cut up into smaller lengths for splicing into electronic nanoarrays, he added.

Moreover, "such long nanotubes make the evaporation of multiple metal electrodes on a single nanotube a relatively easy task," the authors wrote in JACS. "Thus, multiple devices can be created on the same nanotube along its length."

Nanotubes, so named because their smallest dimensions measure just billionths of a meter, were first studied in the 1990s. They are sometimes called buckytubes because their ends, when closed, take the form of soccer ball-shaped carbon molecules known as buckminsterfullerenes, or "buckyballs." Scientists are avidly studying nanotubes because of the cylindrical molecules’ exceptional lightness and strength as well as their intriguing electronic properties, Liu said.

Depending on their specific architectures, nanotubes of sufficient purity can behave either like semiconductors or like metals and could thus form the circuitry for molecular-scale nanoelectrical components of the future, Liu said.

Since coming to Duke from the Rice University laboratory of Nobel Laureate Richard Smalley, a leading researcher in the field, Liu has made a number of advances toward the goal of mass-producing electronically reliable nanotubes.

Last year, his group reported on the advantages of sprouting the nanotubes from catalytic iron and molybdenum seeds, and using a mixture of gaseous carbon monoxide and hydrogen to supply building materials for their growth.

This combination of advances allowed the Duke chemists to grow groups of nanotubes with diameters that were close to uniform. It also let them sprout tubes at locations of their choice on a surface.

But locational control still wasn’t pinpoint, said Liu. The scientists also needed to learn how to steer the direction of tube growth. An illustration in the JACS article shows such "normally"-prepared nanotubes bending in all directions like straw in a walked-on field.

Liu said that "For future electronics applications there are two major barriers in nanotube related research," he added. "One of them is control of location and orientation." The other major obstacle, he said, is tailoring nanotubes to behave consistently as pure metals or pure semiconductors.

Duke’s team has now achieved directional and orientational control by heating samples much more quickly and maintaining a growth temperature of 900 degrees centigrade, it announced in the JACS paper.

"Clearly, the fast-heating is favored for the growth of long and well-aligned nanotubes," the authors wrote. "We believe that the extremely quick growth at the initial stage is the key factor," they added.

Another illustration in that article shows long-straight nanotubes in some cases completely crossing the field of the scanning electron-microscope used to view them. Because the tubes themselves were too thin to be easily seen, the scientists traced in white parallel lines the same length as visual aids.

In their article, the authors also acknowledged that other research groups reported controlling nanotube orientation and location on a flat surface by using an electric field. "However, the introduction of a strong electrical field during the growth of nanotubes is not an easy task," they wrote.

"Furthermore, orienting (nanotube) arrays into multidimensional crossed-network structures in a controllable manner by direct growth was not demonstrated."

Monte Basgall | EurekAlert!
Further information:
http://www.duke.edu/

More articles from Life Sciences:

nachricht The balancing act: An enzyme that links endocytosis to membrane recycling
07.12.2016 | National Centre for Biological Sciences

nachricht Transforming plant cells from generalists to specialists
07.12.2016 | Duke University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

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,...

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

NTU scientists build new ultrasound device using 3-D printing technology

07.12.2016 | Health and Medicine

The balancing act: An enzyme that links endocytosis to membrane recycling

07.12.2016 | Life Sciences

How to turn white fat brown

07.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>