European researchers say they've successfully grown single-wall carbon nanotubes that could bring ever more compact and speedier electronic devices.
Using organic precursor "seed" molecules on a platinum surface allowed the creation of nanotubes with a single, predefined structure that yielded identical electronic properties, they said.
Writing in the science journal Nature, researchers in Switzerland and Germany reported the nanotubes "assembled themselves" into homogeneous carbon nanotubes, or CNTs, of the form desired for the intended electronic properties.
The tubes, about one nanometer thick, are composed of carbon atoms held together through bonds more powerful than those found in diamonds.
While CNTs could have thousands of applications in fields such as electronics and optics, the previous lack of structural uniformity has been an obstacle to their use, as it can significantly alter their electronic properties.
Even tiny differences in their structure or configuration would lead some carbon nantoubes to act like conducting metals while other would act as a semiconductor.
That was what led the researchers to develop the process of "growing" carbon nanotubes that were completely homogeneous -- identical -- in their structure and thus their electric properties.
"The great challenge was to find the suitable starting molecule that would also actually 'germinate' on a flat surface to form the correct seed," says Roman Fasel, who led research at the Swiss Federal Laboratories for Materials Science and Technology.
Colleagues at the Max Planck Institute in Stuttgart, Germany were able to synthetically create a proper starting molecule, a 150-atom hydrocarbon.
On a flat surface of platinum, in a catalytic reaction initiated by heat of around 900 degrees Fahrenheit, the flat starter molecule transforms into a 3-dimensional "germling," to which further carbon atoms are attached in a chemical process utilizing ethanol, causing the nanotube to grow slowly upward.
The atomic structure of the nanotube is completely defined by the original seed molecule, allowing the creation of identical nanotubes from made-to-order molecular "germs," the researchers say.
Carbon nanotubes possessing unique electronic, mechanical and thermal properties will help create next-generation electronic and electro-optical components such as ultra-sensitive light detectors and ultra-small transistors, they say.
One drawback to the "seed" creation method is the cost, currently greater than other methods of creating nanotubes, but Fasel and his research colleagues say further research could provide a fuller understanding of processes by which the nanotubes populate a flat surface, and with such understanding will come better yields and lower costs.
