Navigation Links
Researchers peer into nanowires to measure dopant properties

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 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.

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," he says. "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," he says. "This fundamental scientific understanding establishes a basis for engineering."

Lauhon and his group performed the research at Northwestern's Center for Atom Probe Tomography, which uses a Local Electrode Atom ProbeTM 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," Lauhon says.


Contact: Kyle Delaney
Northwestern University

Related biology technology :

1. Researchers find better way to manufacture fast computer chips
2. Collexis Connects Biomedical Researchers and Clinical Scientists with the Collexis Expert Platform for Translational Research
3. Researchers create catalysts for use in hydrogen storage materials
4. Thomson Reuters Names Hottest Researchers and Papers of 2007-2008
5. Researchers discover a potential on-off switch for nanoelectronics
6. University of Alberta and NINT researchers make solar energy breakthrough
7. Seminar Will Bring ALS Researchers to Patient Groups
8. Researchers at the University of Georgia Discover Protein is Crucial to Reproduction of Parasites Involved in Disease
9. FDA Approves Clinical Studies of a Novel Anti-Cancer Drug Developed by Italian Researchers
10. In Analyst Interview, Cord Blood America Says Stem Cells Now Front and Center for Researchers and Investors
11. Researchers: Molecular forklifts overcome obstacle to smart dust
Post Your Comments:
(Date:11/25/2015)... 25, 2015 /PRNewswire/ - Aeterna Zentaris Inc. (NASDAQ:  AEZS; ... and prospects remain fundamentally strong and highlights the ... recently received DSMB recommendation to continue the ZoptEC ... of the final interim efficacy and safety data ... in men with heavily pretreated castration- and Taxane-resistant ...
(Date:11/24/2015)... 2015  Asia-Pacific (APAC) holds the third-largest share ... The trend of outsourcing to low-cost locations is ... volume share for the region in the short ... in the CRO industry will improve. ... ), finds that the market earned revenues ...
(Date:11/24/2015)... ... November 24, 2015 , ... Copper ... unless it is bound to proteins, copper is also toxic to cells. With ... Worcester Polytechnic Institute (WPI) will conduct a systematic study of copper in the ...
(Date:11/24/2015)... ... 24, 2015 , ... This fall, global software solutions leader SAP and AdVenture ... develop and pitch their BIG ideas to improve health and wellness in their schools. ... to win the title of SAP's Teen Innovator, an all-expenses paid trip to Super ...
Breaking Biology Technology:
(Date:11/17/2015)... Paris from 17 th until 19 th ... from 17 th until 19 th November 2015.   ... the first combined scanner in the world which scans both ... two different scanners were required: one for passports and one ... same surface. This innovation is an ideal solution for electronic ...
(Date:11/16/2015)... , Nov 16, 2015  Synaptics Inc. ... human interface solutions, today announced expansion of its ... ™ touch controller and display driver integration ... of smartphones. These new TDDI products add to ... (HD resolution), TD4302 (WQHD resolution), and TD4322 (FHD ...
(Date:11/11/2015)... MedNet Solutions , an innovative SaaS-based eClinical technology company that ... announce that it will be a Sponsor of the ... held November 17-19 in Hamburg , Germany.  ... iMedNet , MedNet,s easy-to-use, proven and affordable eClinical ... able to deliver time and cost savings of up to ...
Breaking Biology News(10 mins):