New technique probes electron properties of individual atoms


15 December 2010

A new, low voltage electron microscopy technique allows scientists to discriminate not just between atoms of different elements but between atoms of the same element in different electronic states. The researchers who developed it say it could be broadly applied to analyse the fine structures of nanomaterials and important biological molecules.

Carbon atom bonds
The new technique can discriminate between carbon atoms with different numbers of bonds

© Masanori Koshino
Kazu Suenaga and Masanori Koshino at the National Institute of Advanced Industrial Science and Technology in Tsukuba, Japan, used a low voltage, scanning transmission electron microscope (Stem) to probe carbon atoms in graphene. By measuring the energy lost when electrons hit individual atoms, they were able to tell a carbon atom with one bond from others with two or three.

The team used a probe just 0.1nm in diameter to zone in on single atoms. 'In the past, if you were using some other technique, you could do spectroscopy for a local area of 1,000 atoms or a million atoms, something like that,' explains Suenaga. 'Now, with a very tiny probe, we can measure from single atoms.'

Achieving such high spatial resolution has traditionally required big, powerful electron microscopes operating at high accelerating voltages that blast atoms and can destroy specimens. But Suenaga and Koshino's low voltage (60kV) set-up produces the necessary short wavelength electrons for high resolution spectroscopy, whilst leaving samples intact. 

Although there have been previous reports of identifying elements from a single atom using similar methods, this is the first time specific spectral peaks have been obtained from specific atoms, according to Stephen Pennycook, a Stem specialist at Oak Ridge National Laboratory, Tennessee, US. 'It's almost like seeing bonds one by one,' he says. 

The achievements are impressive, says Pratibha Gai, chair of electron microscopy at the University of York's Jeol Nanocentre in the UK. 'The ability to record the reported data is a remarkable feat given the instabilities and inevitably very weak signal,' she adds. 

Gai thinks the method should be applicable to other nanomaterials. And as Suenaga points out, exploring the atomic level structures of nanodevices will become increasingly important. But for now, he has other plans for the technique - for instance, in identifying the active atoms in individual molecules in order to predict how chemical reactions will occur. Previously this has only been possible through theoretical calculations, which would take too long in big molecules like proteins. Another idea is to use the technique to understand why, in solar cells, some silicon atoms perform less well than others. 

Hayley Birch 

 

Interesting? Spread the word using the 'tools' menu on the left.

References

K Suenaga and M Koshino, Nature Chem.,  2010, DOI: 10.1038/nature09664

Also of interest

Precession

Images show atom 'spinning top' control

12 December 2010

Precession of quantum mechanical angular momentum in atomic oxygen can be directed and pictured, potentially allowing more detailed reaction studies


Intermolecular bonds image

Zooming in on intermolecular bonds

13 August 2010

Researchers capture clear images of intermolecular bonds for the first time using a modified form of scanning tunnelling microscopy


Revealing the structure of cephalandole A

Snapshots of mystery molecular structures

01 August 2010

Researchers use atomic force microscopy to produce clear molecular images and help determine the correct atomic structure of unknown molecules


Molecular structures revealed

Molecules in close-up

27 August 2009

A tuning-fork-like device that measures atomic forces can image every single atom in a molecule, according to its Swiss inventors


Related Links

Link icon Comment on this story at the Chemistry World blog
Read other posts and join in the discussion


External links will open in a new browser window