Researchers produce the sharpest needle in the world

The needle will be perfect for electron microscopes

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Researchers from the University of Alberta in and the National Institute for Nanotechnology in Canada have created the sharpest object ever made. The object of their attention is a tungsten needle that tapers down to about the thickness of single atom.

The needle, made by Moh'd Rezeq in the group lead by Professor Robert Wolkow at the University of Alberta and the National Institute for Nanotechnology, was initially much blunter. The needle was exposed to a pure nitrogen atmosphere that made it gradually thinner and thinner.

Tungsten is highly chemically reactive and nitrogen is used to roughen the tungsten surface. But at the tip, where the electric field created by applying a voltage to the tungsten is at its maximum, nitrogen molecules are driven away. This process reaches an equilibrium condition in which the point is very sharp.

Furthermore, when nitrogen is present near the tip this helps to stabilize the tungsten against further chemical degradation. Wolkow says that although a narrower tip will be useful in the construction of high power microscopes the real benefit of the sharp tungsten tips will be as superb electron emitters.

Wolkow explains, "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."

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