Nanotechnology Now

Our NanoNews Digest Sponsors





Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > Researchers Peer Into Nanowires to Measure Dopant Properties

Abstract:
Semiconductor nanowires -- tiny wires with a diameter as small as a few billionths of a meter -- hold promise for devices of the future, both in technology like light-emitting diodes and in new versions of transistors and circuits for the next generation of electronics. But in order to utilize the novel properties of nanowires, their composition must be precisely controlled, and researchers must better understand just exactly how the composition is determined by the synthesis conditions.

Researchers Peer Into Nanowires to Measure Dopant Properties

Evanston, IL | Posted on April 2nd, 2009

Nanowires are synthesized from elements that form bulk semiconductors, whose electrical properties are in turn controlled by adding minute amounts of impurities called dopants. The amount of dopant determines the conductivity of the nanowire.

But because nanowires are so small -- with diameters ranging from 3 to 100 nanometers -- researchers have never been able to see just exactly how much of the dopant gets into the nanowire during synthesis. Now, using a technique called atom probe tomography, Lincoln Lauhon, assistant professor of materials science and engineering at Northwestern University's McCormick School of Engineering and Applied Science, has provided an atomic-level view of the composition of a nanowire. By precisely measuring the amount of dopant in a nanowire, researchers can finally understand the synthesis process on a quantitative level and better predict the electronic properties of nanowire devices.

The results were published online March 29 in the journal Nature Nanotechnology.

"We simply mapped where all the atoms were in a single nanowire, and from the map we determined where the dopant atoms were," said Lauhon. "The more dopant atoms you have, the higher the conductivity."

Previously, researchers could not measure the amount of dopant and had to judge the success of the synthesis based on indirect measurements of the conductivity of nanowire devices. That meant that variations in device performance were not readily explained.

"If we can understand the origin of the electrical properties of nanowires, and if we can rationally control the conductivity, then we can specify how a nanowire will perform in any type of device," said Lauhon. "This fundamental scientific understanding establishes a basis for engineering."

He and his group performed the research at Northwestern's Center for Atom Probe Tomography, which uses a Local Electrode Atom Probe microscope to dissect single nanowires and identify their constituents. This instrumentation software allows 3-D images of the nanowire to be generated, so Lauhon could see from all angles just how the dopant atoms were distributed within the nanowire.

In addition to measuring the dopant in the nanowire, Lauhon's colleague, Peter Voorhees, Frank C. Engelhart Professor of Materials Science and Engineering at Northwestern, created a model that relates the nanowire doping level to the conditions during the nanowire synthesis. The researchers performed the experiment using germanium wires and phosphorous dopants -- and they will soon publish results using silicon -- but the model provides guidance for nanowires made from other elements, as well.

"This model uses insight from Lincoln's experiment to show what might happen in other systems," Voorhees says. "If nanowires are going to be used in device applications, this model will provide guidance as to the conditions that will enable us to add these elements and control the doping
concentrations."

Both professors will continue working on this research to broaden the model.

"We would like to establish the general principles for doping semiconductor nanowires," said Lauhon.

The paper is titled "Direct Measurement of Dopant Distribution in an Individual Vapour-liquid-solid Nanowire." In addition to Lauhon and Voorhees, the other authors are Daniel E. Perea, Eric R. Hemesath, Edwin J. Schwalbach and Jessica L. Lensch-Falk, all from Northwestern.

The Office of Naval Research and the National Science Foundation supported the research.

####

About Northwestern University
Research thrives at Northwestern University, with an annual budget of over $1.5 billion and more than $439 million in sponsored research. At Northwestern, and often with partners at Argonne National Laboratory, Fermilab, and local universities, interdisciplinary teams work to solve society's problems and facilitate clinical and commercial use of their innovations.

For more information, please click here

Contacts:
Megan Fellman
(847) 491-3115

Copyright © Northwestern University

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 Links

Northwestern’s Center for Atom Probe Tomography

Related News Press

News and information

Study finds long-term survival of human neural stem cells transplanted into primate brain April 23rd, 2014

High-Performance, Low-Cost Ultracapacitors Built with Graphene and Carbon Nanotubes: Future devices based on technology could bridge gap between batteries and conventional capacitors in portable electronics and hybrid electric vehicles April 23rd, 2014

Guo Lab Shows Potential of RNA as Heat-resistant Polymer Material for Nanoarchitectures April 23rd, 2014

National Space Society Congratulates SpaceX on the Success of CRS-3 and the First Flight of the Falcon 9R April 22nd, 2014

Possible Futures

Virus structure inspires novel understanding of onion-like carbon nanoparticles April 10th, 2014

Local girl does good March 22nd, 2014

Surface Characteristics Influence Cellular Growth on Semiconductor Material March 12th, 2014

The "Tipping Point" February 12th, 2014

Nanoelectronics

Progress made in developing nanoscale electronics: New research directs charges through single molecules April 21st, 2014

Better solar cells, better LED light and vast optical possibilities April 12th, 2014

Catching the (Invisible) Wave: UC Santa Barbara researchers create a unique semiconductor that manipulates light in the invisible infrared/terahertz range, paving the way for new and enhanced applications April 11th, 2014

Nanotech Business Review 2013-2014 April 9th, 2014

Announcements

Study finds long-term survival of human neural stem cells transplanted into primate brain April 23rd, 2014

High-Performance, Low-Cost Ultracapacitors Built with Graphene and Carbon Nanotubes: Future devices based on technology could bridge gap between batteries and conventional capacitors in portable electronics and hybrid electric vehicles April 23rd, 2014

Guo Lab Shows Potential of RNA as Heat-resistant Polymer Material for Nanoarchitectures April 23rd, 2014

National Space Society Congratulates SpaceX on the Success of CRS-3 and the First Flight of the Falcon 9R April 22nd, 2014

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







© Copyright 1999-2014 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE