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June 19, 2008

Miniture scanning electron microscopes on a chip


The UK's NFAB has a new sub-miniature scanning electron microscope which is a completely new concept in electron microscopy. The microscope is 5 μm long and has atomic resolution (2 Å) at 500 eV energy and 10 nA of current. The low energy means it can identify single atoms on a surface as well as being able to make holograms of large molecules.

It has patented an enabling technology* which will allow a generation of miniature scanning electron microscopes, multiple-beam lithography machines and focussed ion beam millers to be manufactured. These are currently under development and testing at Salford University and various other European Universities and nanotechnology companies under an EU-funded collaborative research grant (CRAFT).


This is not useful for actually manipulating the molecules just for looking, but cheaper and better resolution would still be nice.

They claim the microscope will have 0.01 nm resolution. Instead of firing electrons from a tungsten filament, it will shoot them from a single atom at the peak of a tiny gold pyramid with a height of around 100 nanometres. The beam will be focused as it passes through a 2 micrometer hole in a silicon chip before it hits the target below.


The electron beam itself is just 10 micrometers long in Eastham's new microscope – the beam of a standard SEM is around 60 centimetres long. The electrostatic lens used in the new SEM still contains imperfections that will limit the microscope's resolution, says Eastham, but the effect should be much smaller. Eastham's approach
produces a beam with around 100 times less energy than usual in an SEM. Cutting power consumption addresses one of the greatest costs of SEM technology, he claims.

The new design will lack the large depth of field that lets SEMs produce images with a 3D appearance, due to the design of its aperture. Eastham's team should have a prototype of the nano-SEM completed within 3 to 6 months, he says. The microscope is expected to be available for sale within two years for a cost of approximatively $195,000. Current SEMs with a resolution of 0.05 nanometers can cost around $8 million. The price would be 40 times less and the resolution would be improved by four to five times.

"It is now possible to 'aberration correct' electron optical lenses," he says, which allows the best, current, multi-million dollar SEMs to reach about 0.04 nm resolution.

FURTHER READING
Roland Piquipaille has coverage as well

Sky news coverage of the NFAB

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