Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers develop technique that could open doors to faster nanotech commercialization

24.06.2003


Engineers at the University of California, Berkeley, have found an innovative way to grow silicon nanowires and carbon nanotubes directly on microstructures in a room temperature chamber, opening the doors to cheaper and faster commercialization of a myriad of nanotechnology-based devices.


Shown at left are carbon nanotubes grown on the sides of a microstructure. As they grow, they are oriented towards the local electrical field, marked by the "E." . (Courtesy Ron Wilson and Dane Christensen)


Shown above are oblique and closeup views of silicon nanowire growth. The nanowires are centrally located to 35 micrometers of a 100 micrometer-long microstructure. (Courtesy Bob Prohaska and Ongi Englander



The researchers were able to precisely localize the extreme heat necessary for nanowire and nanotube growth, protecting the sensitive microelectronics - which remained at room temperature - just a few micrometers away, or about one-tenth the diameter of a strand of human hair.

The new technique, described in the June 24 online issue of the journal Applied Physics Letters, eliminates cumbersome middle steps in the manufacturing process of sensors that incorporate nanotubes or nanowires. An image of the technique will be featured on the cover of the journal’s June 30 print issue.


Such devices would include early-stage disease detectors that could signal the presence of a single virus or an ultra-sensitive biochemical sensor triggered by mere molecules of a toxic agent.

"One very big problem right now is figuring out how to assemble these nanowires or nanotubes onto a microchip in a way that is commercially feasible," said Liwei Lin, associate professor of mechanical engineering at UC Berkeley.

Lin tested the new technique for processing nano-based microelectromechanical systems (MEMS) devices with his graduate students Ongi Englander, lead author of the paper, and Dane Christensen, co-author of the paper.

The steps used in creating nanowires and nanotubes are essentially the same, though different chemicals and temperatures may be used. "It’s like a recipe," said Englander. "Different ingredients are used depending upon whether you want to make a chocolate chip muffin or a banana nut muffin, but the steps are more or less the same."

The UC Berkeley researchers, in this case, used a gold-palladium alloy with silane vapor to create silicon nanowires, and a nickel-iron alloy with acetylene vapor to create carbon nanotubes.

The typical nanowire or nanotube production process occurs in a furnace at temperatures of 600 to 1,000 degrees Celsius (1,112 to 1,832 degrees Fahrenheit). The procedure begins with a 1 square centimeter silicon wafer that is coated thinly with a metal alloy. A vapor is then directed towards the substrate, and the metal alloy acts as a catalyst in a chemical reaction that eventually forms billions of nanowire or nanotube precipitates.

The nanomaterials are harvested by being placed in a liquid solvent, such as ethanol, and blasted with ultrasonic waves to loosen them from the wafer surface. Researchers must then sort through the billions of nanowires or nanotubes to find the few that meet the specifications they need for their sensor applications.

Correctly orienting a nanowire onto a 5 square millimeter microchip would be like sticking a sewing needle into a football field with an accuracy of a few micrometers.

"If I had the right pair of tweezers, I could pick out the nanowire that I wanted and manipulate it, but such tweezers don’t exist," said Englander.

So instead of finding a way to produce nanomaterials separately and then connecting them to larger scale systems, the researchers decided to grow the silicon nanowires and carbon nanotubes directly onto the circuit board.

The challenge was in protecting the sensitive microelectronics that would melt in the tremendously high temperatures needed to create the nanomaterials.

Resistive heating provided the answer. "It’s the same idea as the wires in a toaster," said Englander. "The electrical current flows through the wire to generate the heat."

The researchers passed the current through a wire to the specific locations on the microstructure where they wanted the nanowires or nanotubes to grow. In one experiment, an area was heated to 700 degrees Celsius while another spot just a few micrometers away sat comfortably at 25 degrees Celsius. The entire circuit board was placed in a vacuum chamber for the tests.

"It’s the immediate integration of the nanoscale with the microscale," said Christensen, who worked on the carbon nanotube experiments.

The experiments yielded silicon nanowires from 30 to 80 nanometers in diameter and up to 10 micrometers long, and carbon nanotubes that were 10 to 30 nanometers in diameter and up to 5 micrometers long.

"This is a very unique approach," said Lin. "This method allows the production of an entire nano-based sensor in a process similar to creating computer chips. There would be no post-assembly required."

The researchers are continuing experiments to fine-tune the temperatures and length of heating time to create desired lengths of nanowires and nanotubes.

The California State Nanotechnology Fellowship and the GAANN Fellowship helped support this research.

Sarah Yang | UC Berkeley
Further information:
http://www.berkeley.edu/news/media/releases/2003/06/23_nanotech.shtml

More articles from Physics and Astronomy:

nachricht From rocks in Colorado, evidence of a 'chaotic solar system'
23.02.2017 | University of Wisconsin-Madison

nachricht Prediction: More gas-giants will be found orbiting Sun-like stars
22.02.2017 | Carnegie Institution for Science

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: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Stingless bees have their nests protected by soldiers

24.02.2017 | Life Sciences

New risk factors for anxiety disorders

24.02.2017 | Life Sciences

MWC 2017: 5G Capital Berlin

24.02.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>