Simultaneous Nanoscale Imaging of Surface and Bulk Atoms

September 23, 2009
Uranium single atoms (circled) and small crystallites on a carbon support imaged simultaneously using a scanning probe to produce forward scattering through the sample (top) and backward scattering emerging from the surface (bottom). Center panel shows superimposition of the two in red (bulk) and green (surface). Atoms not seen in the lower image are on the bottom surface of the support. Source: Brookhaven National Laboratory

Uranium single atoms (circled) and small crystallites on a carbon support imaged simultaneously using a scanning probe to produce forward scattering through the sample (top) and backward scattering emerging from the surface (bottom). Center panel shows superimposition of the two in red (bulk) and green (surface). Atoms not seen in the lower image are on the bottom surface of the support. Source: Brookhaven National Laboratory

Scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory, in collaboration with researchers from Hitachi High Technologies Corp., have demonstrated a new scanning electron microscope capable of selectively imaging single atoms on the top surface of a specimen while a second, simultaneous imaging signal shows atoms throughout the sample’s depth. This new tool, located at Brookhaven Lab’s Center for Functional Nanomaterials (CFN), will greatly expand scientists’ ability to understand and ultimately control chemical reactions, such as those of catalysts in energy-conversion devices.
Like all scanning electron microscopes, the new tool probes a sample with an electron beam focused to a tiny spot and detects so-called secondary electrons emitted by the sample to reveal its surface structure and topography. Though this technique has been a workhorse of surface imaging in industrial and academic laboratories for decades, its resolution has left much to be desired because of imperfect focusing due to lens aberrations.
Using a newly developed spherical aberration corrector, the new tool corrects these distortions to create a smaller probe with significantly increased brightness.
The new device also employs specialized electron optics to channel the emitted secondary electrons to the detector. The result is a fourfold improvement in resolution to below one tenth of a nanometer — and thus, the ability to image single atoms.
Additional detectors, located below the sample, detect electrons transmitted through the sample, revealing details about the entire structure at the exact instant the “shutter” snapped to record each pixel of the surface image. This simultaneous imaging allows the scientists to correlate information in the two images to understand precisely what is happening on the surface and throughout the sample at the same time.
Because of its extreme sensitivity, the new microscope must be kept isolated from a range of environmental effects such as variations in temperature, mechanical vibrations, and electromagnetic fields. Even the slightest waft of air could cause distortions in the images.

Original publication:
Zhu Y., Inada H., Nakamura K., Wall J.: Imaging single atoms using secondary electrons with an aberration-corrected microscope. Nat Mater. 2009 Sep 20. [Epub ahead of print]

http://www.bnl.gov


European Biophysics Congress

März 24, 2009

The 7th European Biophysics Congress will take place in Genoa, Italy from July 11-15, 2009. The congress is organized on behalf of the Italian Society of Pure and Applied Biophysics (SIBPA) and the European Biophysics Societies Association (EBSA). It address to representatives from academic and industrial institutions.

Conference topics include:

1. Single molecule biophysics
2. Lipid biophysics
3. Folding/unfolding of proteins
4. Multiscale simulation
5. Chromatin, nucleosomes and molecular machines
6. Glycobiophysics
7. Biomolecular self-assembly
8. Photosensory biophysics
9. Structure-function relationships (channels, pumps, exchangers)
10. Live cell imaging
11. Protein-ligand interactions
12. Membrane microdomains and signalling
13. Biological motility and molecular motors
14. Interaction and recognition of DNA
15. Biomaterials and drug delivery
16. Single molecule fluorescence
17. Imaging and spectroscopy
18. Fluorescent proteins
19. Solar energy conversion and photosynthesis
20. Statistical, soft matter and biological physics
21. Condensed colloidal phase in biology
22. Ion channels in channelopathies and cancer
23. RNA world
24. Stem cells

www.ebsa2009.org

biophysics-congress-genova