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 expl
|Contact: Kyle Delaney|