Nanotechnology Now

Our NanoNews Digest Sponsors


Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > New way to grow microwires

This new technique for growing microwires can produce strands that are very long in relation to their diameter. The rounded “cap” at the wire’s top is a droplet of molten copper, while the wire itself is pure silicon. Image courtesy of Tonio Buonassisi
This new technique for growing microwires can produce strands that are very long in relation to their diameter. The rounded “cap” at the wire’s top is a droplet of molten copper, while the wire itself is pure silicon. Image courtesy of Tonio Buonassisi

Abstract:
Researchers find simple, inexpensive method to produce silicon wires for sensors, batteries and solar cells.

By David L. Chandler, MIT News Office

New way to grow microwires

Cambridge, MA | Posted on February 7th, 2011

Microwires made of silicon — tiny wires with a thickness comparable to a human hair — have a wide range of possible uses, including the production of solar cells that can harvest much more sunlight for a given amount of material than a conventional solar cell made from a thin wafer of silicon crystal. Now researchers from MIT and Penn State have found a way of producing such wires in quantity in a highly controlled way that could be scaled up to an industrial-scale process, potentially leading to practical commercial applications.

Other ways of making such wires are already known, and prototypes of solar cells made from them have been produced by several researchers. But these methods have serious limitations, says Tonio Buonassisi, MIT professor of mechanical engineering and a co-author of a paper on the new work that was recently published online in the journal Small, and will soon appear in the print edition. Most require several extra manufacturing steps, provide little control over the exact sizes and spacing of the wires, and only work on flat surfaces. By contrast, the new process is simple yet allows precise control over the wire dimensions and spacing, and could theoretically be done on any kind of curved, 3-D surface.

Microwires are thought to be capable of reaching efficiencies close to those of conventional solar cells in converting sunlight to electricity, but because the wires are so tiny they would do so using only a small fraction of the amount of expensive silicon needed for the conventional cells, thus potentially achieving major reductions in cost.

In addition to microwires' potential use in solar cells, other researchers have proposed ways such microscopic wires could be used to build new kinds of transistors and integrated circuits, as well as electrodes for advanced batteries and certain kinds of environmental monitoring devices. For any of these ideas to be practical, however, there must be an efficient, scalable manufacturing method.

The new method involves heating and intentionally contaminating the surface of a silicon wafer with copper, which diffuses into the silicon. Then, when the silicon slowly cools, the copper diffuses out to form droplets on the surface. Then, when it is placed in an atmosphere of silicon tetrachloride gas, silicon microwires begin to grow outward wherever there is a copper droplet on the surface. Silicon in the gas dissolves into these copper droplets, and then after reaching a sufficient concentration begins to precipitate out at the bottom of the droplet, onto the silicon surface below. This buildup of silicon gradually elongates to form microwires each only about 10 to 20 micrometers (millionths of a meter) across, growing up from the surface. The whole process can be carried out repeatedly on an industrial manufacturing scale, Buonassisi says, or even could potentially be adapted to a continuous process.

The spacing of the wires is controlled by textures created on the surface — tiny dimples can form centers for the copper droplets — but the size of the wires is controlled by the temperatures used for the diffusion stage of the process. Thus, unlike in other production methods, the size and spacing of the wires can be controlled independently of each other, Buonassisi says.

The work done so far is just a proof of principle, he says, and more work remains to be done to find the best combinations of temperature profiles, copper concentrations and surface patterning for various applications, since the process allows for orders-of-magnitude differences in the size of the wires. For example, it remains to be determined what thickness and spacing of wires produces the most efficient solar cells. But this work demonstrates a potential for a kind of solar cell based on such wires that could significantly lower costs, both by allowing the use of lower grades of silicon (that is, less-highly refined), since the process of wire growth helps to purify the material, and by using much smaller amounts of it, since the tiny wires are made up of just a tiny fraction of the amount needed for conventional silicon crystal wafers. "This is still in a very early stage," Buonassisi says, because in deciding on a configuration for such a solar cell "there are so many things to optimize."

Michael Kelzenberg, a postdoctoral scholar at the California Institute of Technology who has spent the last five years doing research on silicon microwires, says that while others have used the copper-droplet technique for growing microwires, "What's really new here is the method of producing those liquid metal droplets." While others have had to place the droplets of molten copper on the silicon plate, requiring extra processing steps, "Buonassisi and his colleagues have shown that metal can be diffused into the growth substrate beforehand, and through careful heating and cooling, the metal droplets will actually form on their own — with the correct position and size."

Kelzenberg adds that his research group has recently demonstrated that silicon microwire solar cells can equal the efficiency of today's typical commercial solar cells. "I think the greatest challenge remaining is to show that this technique is more cost-effective or otherwise beneficial than other catalyst metal production methods," he says. But overall, he says, some version of silicon microwire technology "has the potential to enable dramatic cost reductions" of solar panels.

The paper was co-authored by Vidya Ganapati '10, doctoral student David Fenning, postdoctoral fellow Mariana Bertoni, and research specialist Alexandria Fecych, all in MIT's Department of Mechanical Engineering, and postdoctoral researcher Chito Kendrick and Professor Joan Redwing of Pennsylvania State University. The work was supported by the U.S. Department of Energy, the Chesonis Family Foundation and the National Science Foundation.

####

For more information, please click here

Copyright © MIT

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Superheroes are real: Ultrasensitive nonlinear metamaterials for data transfer June 25th, 2016

Russian physicists create a high-precision 'quantum ruler': Physicists have devised a method for creating a special quantum entangled state June 25th, 2016

Nanoscientists develop the 'ultimate discovery tool': Rapid discovery power is similar to what gene chips offer biology June 25th, 2016

Ultrathin, flat lens resolves chirality and color: Multifunctional lens could replace bulky, expensive machines June 25th, 2016

Possible Futures

Superheroes are real: Ultrasensitive nonlinear metamaterials for data transfer June 25th, 2016

Russian physicists create a high-precision 'quantum ruler': Physicists have devised a method for creating a special quantum entangled state June 25th, 2016

Nanoscientists develop the 'ultimate discovery tool': Rapid discovery power is similar to what gene chips offer biology June 25th, 2016

Nanotechnology and math deliver two-in-one punch for cancer therapy resistance June 24th, 2016

Academic/Education

JPK’s NanoWizard® AFM and ForceRobot® systems are being used in the field of medical diagnostics in the Supersensitive Molecular Layer Laboratory of POSTECH in Korea June 21st, 2016

Weizmann Institute of Science Presents: Weizmann Wonder Wander - 4G - is Online June 21st, 2016

NanoLabNL boosts quality of research facilities as Dutch Toekomstfonds invests firmly June 10th, 2016

The Institute for Transfusion Medicine at the University Hospital of Duisburg-Essen in Germany uses the ZetaView from Particle Metrix to quantify extracellular vesicles June 7th, 2016

Sensors

Researchers discover new chemical sensing technique: Technique allows sharper detail -- and more information -- with near infrared light June 24th, 2016

Artificial synapse rivals biological ones in energy consumption June 21st, 2016

A new form of hybrid photodetectors with quantum dots and graphene June 19th, 2016

Drum beats from a one atom thick graphite membrane June 15th, 2016

Discoveries

Superheroes are real: Ultrasensitive nonlinear metamaterials for data transfer June 25th, 2016

Russian physicists create a high-precision 'quantum ruler': Physicists have devised a method for creating a special quantum entangled state June 25th, 2016

Nanoscientists develop the 'ultimate discovery tool': Rapid discovery power is similar to what gene chips offer biology June 25th, 2016

Ultrathin, flat lens resolves chirality and color: Multifunctional lens could replace bulky, expensive machines June 25th, 2016

Announcements

Superheroes are real: Ultrasensitive nonlinear metamaterials for data transfer June 25th, 2016

Russian physicists create a high-precision 'quantum ruler': Physicists have devised a method for creating a special quantum entangled state June 25th, 2016

Nanoscientists develop the 'ultimate discovery tool': Rapid discovery power is similar to what gene chips offer biology June 25th, 2016

Ultrathin, flat lens resolves chirality and color: Multifunctional lens could replace bulky, expensive machines June 25th, 2016

Battery Technology/Capacitors/Generators/Piezoelectrics/Thermoelectrics/Energy storage

Stanford researchers find new ways to make clean hydrogen and rechargable zinc batteries June 18th, 2016

Efficient hydrogen production made easy: Sticking electrons to a semiconductor with hydrazine creates an electrocatalyst June 17th, 2016

A New Approach To Building Efficient Thermoelectric Nanomaterials June 17th, 2016

Novel energy inside a microcircuit chip: VTT developed an efficient nanomaterial-based integrated energy June 10th, 2016

Research partnerships

Superheroes are real: Ultrasensitive nonlinear metamaterials for data transfer June 25th, 2016

Soft decoupling of organic molecules on metal June 23rd, 2016

FEI and University of Liverpool Announce QEMSCAN Research Initiative: University of Liverpool will utilize FEI’s QEMSCAN technology to gain a better insight into oil and gas reserves & potentially change the approach to evaluating them June 22nd, 2016

Tailored DNA shifts electrons into the 'fast lane': DNA nanowire improved by altering sequences June 22nd, 2016

Solar/Photovoltaic

Nanoscientists develop the 'ultimate discovery tool': Rapid discovery power is similar to what gene chips offer biology June 25th, 2016

New generation of high-efficiency solar thermal absorbers developed June 20th, 2016

Novel capping strategy improves stability of perovskite nanocrystals: Study addresses instability issues with organometal-halide perovskites, a promising class of materials for solar cells, LEDs, and other applications June 13th, 2016

Perovskite solar cells surpass 20 percent efficiency: EPFL researchers are pushing the limits of perovskite solar cell performance by exploring the best way to grow these crystals June 13th, 2016

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







Car Brands
Buy website traffic