Diamond-like coating improves electron microscope images

This is according to a study led by scientists at SLAC National Accelerator Laboratory and Stanford University.

The group have reported a nearly three-fold improvement in the quality of photoelectron emission microscope (PEEM) images when they used the coating.

PEEM images reveal important aspects of the sample’s surface structure, chemical bonding and magnetic properties.

The technique involves shining intense ultraviolet or X-ray light onto a sample and recording electrons emitted from just below its surface, which are used to form an image.

Diamondoids capture electrons emitted from the sample and re-emit them within a very narrow energy range

However, the high X-ray energies often used in these studies trigger emissions of electrons with a wide range of energies - and this limits the resolution of the image.

Although the image can be sharpened with complex electronics, the Stanford/SLAC team thought a simple coating of diamondoids might work just as well - and it did.

“Earlier lab tests had shown that diamondoids should be excellent electron emitters,” said Nicholas Melosh, an associate professor of materials science and engineering at Stanford.

Diamondoids are made of 10 or more carbon atoms arranged in the same way as a diamond.

Known since the 1930s to exist in many oil and gas wells - where they are considered a nuisance - diamondoids are relatively cheap, readily available.

“This is the first published paper demonstrating that diamondoids can directly improve PEEM imaging,” said Melosh.

Adding a single layer of diamondoid crystals to the surface of a cobalt-platinum magnetic alloy improved the resolution of the microscope image - the size of the smallest perceivable detail - from 25 nanometers, or billionths of a meter, to 10 nanometers.

The diamondoids capture electrons emitted from the sample and re-emit them within a very narrow energy range, which can then be focused precisely.

“Our study exemplifies how the unique properties of a nanoparticle can help solve a problem not suited to conventional engineering solutions,” said SLAC microscopist Hendrik Ohldag.

“With 10-nanometer resolution, we can start to identify and analyse the structures of domain walls - the critical transition regions between magnetic orientations in ferromagnetic or ferroelectric materials.

“It also enables us to significantly reduce the exposure time without sacrificing resolution, which is important when looking at organic materials, such as polymers, which degrade quickly in the X-ray beam.”

Future research aims to make the diamondoid coating more durable and find ways to use it on more materials, including non-metals.

Ultimately, the researchers believe diamondoids could also improve the resolution of scanning electron microscopes, electron-beam writing and nanolithography tools.