Atom Manipulation Crosses New Threshold | Chemical & Engineering News
Volume 92 Issue 29 | p. 29 | Concentrates
Issue Date: July 21, 2014

Atom Manipulation Crosses New Threshold

Researchers drag ions over insulating surface at room temperature, assemble them into Swiss icon
Department: Science & Technology
News Channels: Nano SCENE, Materials SCENE
Keywords: atomic manipulation, atoms, ions, insulator, Swiss cross, atomic-scale devices
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This 5.6-nm-wide Swiss cross, made of bromine ions (orange) on a sodium chloride surface (blue), is stable at room temperature.
Credit: Nat. Commun.
Researchers used an atomic force microscope to move bromine atoms (orange) in the shape of a Swiss cross on top of a salt surface (blue). The cross is 5.6 nanometers square.
 
This 5.6-nm-wide Swiss cross, made of bromine ions (orange) on a sodium chloride surface (blue), is stable at room temperature.
Credit: Nat. Commun.

In a teeny tiny display of patriotism, a team led by researchers at the University of Basel has created the world’s smallest Swiss national flag out of ions (Nat. Commun. 2014, DOI: 10.1038/ncomms5403). To generate the flag’s iconic cross, the scientists used the tip of an atomic force microscope (AFM) to pick up bromine ions scattered across a sodium chloride surface and move them one by one into formation. With the hope of one day creating atomic-scale electromechanical devices, physicists have been dragging single atoms around and repositioning them on surfaces with scanning probe tips since the 1990s. Usually, the atomic manipulations are carried out on metallic or semiconducting surfaces at very low temperatures. The Swiss cross, however, was generated on an insulating surface—sodium chloride—at room temperature. The researchers accomplished the more difficult task, says team leader Ernst Meyer, because of “tremendous progress” in the sensitivity and stability of AFMs. The team believes it succeeded in building the 20-ion cross because the NaCl-coated AFM tip it used had sodium ions at its apex: These positively charged particles were able to pick up the negatively charged bromines.

 
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