The sharp end of research

Scientists at the

(U of A) have created the sharpest ever single atom tip, which could lead to much clearer electron microscope images.

The researchers, working out of the National Research Council's National Institute of Nanotechnology (NINT) at the U of A, used a unique process to make the tungsten tip. They were able to coat peripheral atoms near the peak with nitrogen, making it effectively a one atom-thick, tough, protective paint job.

"That coating has the effect of binding the little pyramid of tungsten atoms in place," said Dr Robert Wolkow, a physics professor at the U of A and co-author on the research paper published in the Journal of Chemical Physics. "Such a pointy pyramid of metal atoms would normally just smudge away spontaneously. It's like a sand pile; you know you can't make it arbitrarily pointy. If you try to pile on more sand, it flows down and makes a more blunt pile. Metal atoms will do the same thing."

These sharp tips are needed for making contact with metals or semiconductors as well as for the manipulation and examination of atoms, molecules and small particles. Ultrafine tips could be used for future experiments where the results are directly dependent on shape of the tip.

The tips made by Wolkow and the research team, consisting of Moh'd Rezeq and Jason Pitters from NINT, are so stable they withstand about 900o Celsius. They are so sharp they appear to serve as excellent emitters of electron beams.

"The lenses in an electron microscope work more perfectly if the electron beam comes from a really small point," said Wolkow. "Since we have the smallest point source of electrons, we think we will be able to make the best electron microscopes. This is speculation, but based on pretty conventional thinking.

"If this works, and it remains to be proven, it would be like taking a modest car and making it go like a race car by just changing its spark plugs. We would take a conventional electron microscope, put in one of our tips as the electron source and render the microscope instantly improved and capable of finer resolution."

Wolkow also expects the sharp tips will allow electrical characterisation of extremely small objects, in turn allowing new device concepts to be discovered and tested.