A cold-atom scanning probe microscope is reported this week in Nature Nanotechnology. This new device could be used to make more accurate measurements of the interactions between atoms and surfaces.
Andreas Gunther and colleagues created the microscope by replacing the solid tip of an atomic force microscope with a gas of rubidium atoms that was cooled to close to absolute zero. They used magnetic fields to trap and cool the gas, which was then moved close to the surface they wanted to study. By measuring the number of atoms lost from the gas as a result of interactions with the surface, they were able to measure the position and height of structures made from carbon nanotubes and individual free-standing nanotubes. The resolution of the device was improved by cooling the atoms even more so that they formed a special type of ultracold gas called a Bose-Einstein condensate. The researchers also showed that it was possible to study the surface by measuring changes in the way the condensate moved back and forth in the magnetic trap when the microscope was moved close to the sample.
The new device cannot yet rival the resolution of the atomic force microscope, but it could be used to make more accurate measurements of the dispersion forces between atoms or between an atom and a surface.