Electron nanodiffraction technique offers atomic resolution imaging

May 29, 2003

CHAMPAIGN, Ill. -- A new imaging technique that uses electron diffraction waves to improve both image resolution and sensitivity to small structures has been developed by scientists at the University of Illinois at Urbana-Champaign. The technique works on the same principle as X-ray diffraction, but can record structure from a single nanostructure or macromolecule.

Determining the structure of materials -- such as protein crystals -- is currently performed using X-ray diffraction. However, many small structures used in nanotechnology have not been accessible to crystallography, so their structures remain unknown.

"Nature is full of objects that cannot be easily crystallized, including many proteins and nano-sized objects that lack a periodic structure," said Jian-Min (Jim) Zuo, a professor of materials science and engineering at Illinois and corresponding author of a paper to appear in the May 30 issue of the journal Science. "Our technique has the potential to image nonperiodic nanostructures, including biological macromolecules, at atomic resolution."

To demonstrate the effectiveness of their imaging technique, Zuo and his colleagues recorded and processed the diffraction pattern from a double-wall carbon nanotube.

"Carbon nanotubes are of special interest because the mechanical and electrical properties of a nanotube depend upon its structure," said Zuo, who also is a researcher at the Frederick Seitz Materials Research Laboratory on the Illinois campus. "However, only the outermost shell of a carbon nanotube has been imaged by scanning tunneling microscopy with atomic resolution."

Because carbon possesses few electrons, the scattering from an electron beam is inherently weak and typically results in an image with low contrast and poor resolution, Zuo said. Imaging carbon atoms has been a special challenge.

"While conventional electron microscopes can achieve a resolution approaching1 angstrom for many materials," Zuo said, "the resolution limit for carbon in nanotubes is only 3 angstroms."

To image a double-wall carbon nanotube, the researchers first selected a single nanotube target in a transmission electron microscope. Then they illuminated the nanotube with a narrow beam of electrons about 50 nanometers in diameter. After recording the diffraction pattern, they used an oversampling technique and iterative process to retrieve phase information and construct an image with a resolution of 1 angstrom.

"Since this process does not use a lens to form the image, the resolution is not limited by lens aberration," Zuo said. "Lens aberration is the factor that has been limiting the resolution of the best electron microscopes. It's like the blur when you look through the bottom of a wine bottle."

The complexity of the nanotube image was surprising, Zuo said. "The double-wall nanotube consists of two concentric nanotubes of different helical angles. Like two screws with different pitch, sometimes the nanotube structures line up and sometimes they don't. This results in a complicated pattern of both accidental coincidences and mismatches."

The ability to generate images from nanoscale diffraction patterns offers a way to determine the structure of nonperiodic objects, from inorganic nanostructures to biological macromolecules, much like X-ray diffraction does for crystals, Zuo said. "Since diffraction is a standard method for determining structure, our nanoarea electron diffraction technique opens a door to examining the structure of individual and highly irregular molecules and nanostructures like clusters and wires."
In addition to Zuo, the team included visiting scientist Ivan Vartanyants and postdoctoral researcher Min Gao at Illinois, and researchers Ruth Zhang and Larry Nagahara at Motorola Labs. The U.S. Department of Energy funded the work.

University of Illinois at Urbana-Champaign

Related Nanotubes Articles from Brightsurf:

Nanotubes in the eye that help us see
A new mechanism of blood redistribution that is essential for the proper functioning of the adult retina has just been discovered in vivo by researchers at the University of Montreal Hospital Research Centre (CRCHUM).

How plantains and carbon nanotubes can improve cars
Researchers from the University of Johannesburg have shown that plantain, a starchy type of banana, is a promising renewable source for an emerging type of lighter, rust-free composite materials for the automotive industry.

Exotic nanotubes move in less-mysterious ways
Rice University researchers capture the first video of boron nitride nanotubes in motion to prove their potential for materials and medical applications.

Groovy key to nanotubes in 2D
New research offers a groovy answer to the question of what causes carbon nanotubes to align in ultrathin crystalline films discovered at Rice.

Growing carbon nanotubes with the right twist
Researchers synthetize nanotubes with a specific structure expanding previous theories on carbon nanotube growth.

Clean carbon nanotubes with superb properties
Scientists at Aalto University, Finland, and Nagoya University, Japan, have found a new way to make ultra-clean carbon nanotube transistors with superior semiconducting properties.

Watching energy transport through biomimetic nanotubes
Scientists from the University of Groningen (the Netherlands) and the University of W├╝rzburg (Germany) have investigated a simple biomimetic light-harvesting system using advanced spectroscopy combined with a microfluidic platform.

Neural networks will help manufacture carbon nanotubes
A team of scientists from Skoltech's Laboratory of Nanomaterials proposed a neural-network-based method for monitoring the growth of carbon nanotubes, preparing the ground for a new generation of sophisticated electronic devices.

Photovoltaic nanotubes
Physicists discovered a novel kind of nanotube that generates current in the presence of light.

Chemical synthesis of nanotubes
For the first time, researchers used benzene -- a common hydrocarbon -- to create a novel kind of molecular nanotube, which could lead to new nanocarbon-based semiconductor applications.

Read More: Nanotubes News and Nanotubes Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.