"When you make nanocircuits, you only want the semiconducting ones, so it's very important to have a method to identify the metallic nanotubes," Yang said.
The paper was written by Purdue physics doctoral student Yookyung Jung; biomedical engineering research scientist Mikhail N. Slipchenko; Chang-Hua Liu, an electrical engineering graduate student at the University of Michigan; Alexander E. Ribbe, manager of the Nanotechnology Group in Purdue's Department of Chemistry; Zhaohui Zhong, an assistant professor of electrical engineering and computer science at Michigan; and Yang and Cheng. The Michigan researchers produced the nanotubes.
Semiconductors such as silicon conduct electricity under some conditions but not others, making them ideal for controlling electrical current in devices such as transistors and diodes.
The nanotubes have a diameter of about 1 nanometer, or roughly the length of 10 hydrogen atoms strung together, making them far too small to be seen with a conventional light microscope.
"They can be seen with an atomic force microscope, but this only tells you the morphology and surface features, not the metallic state of the nanotube," Cheng said.
The transient absorption imaging technique represents the only rapid method for telling the difference between the two types of nanotubes. The technique is "label free," meaning it does not require that the nanotubes be marked with dyes, making it potentially practical for manufacturing, he said.
The researchers performed the technique with nanotubes placed on a glass surface. Future work will focus on performing the imaging when nanotubes are on a silicon surface to determine how well it would work in industrial applications.
"We have begun this work on a silicon substrate, and preliminary results are very good," Cheng said.
|Contact: Emil Venere|