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nanotimes News in Brief

Microscopes // Microscopy with a Quantum Tip

G

erman researchers have been able to create a microscope tip out of an ultra-cold, dilute gas

of atoms. They cooled an especially pure gas of rubi- dium atoms to a temperature less than a millionth of a degree above absolute zero temperature, and sto- red the atoms in a magnetic trap. This “quantum tip” can be precisely positioned and enables the probing of nanostructured surfaces. With this method, more accurate measurements of the interactions between atoms and surfaces are possible and further cooling of the probe tip gives rise to a so-called Bose-Einstein condensate, which allows a significant increase in the resolution of the microscope. The work was led by Prof. Dr. József Fortágh, head of the Nano-Atom- Optics group in Tuebingen, Germany, and his co- worker Dr. Andreas Günther. PhD student Michael Gierling is first author of the study.

The scientists demonstrated the use of their cold- atom scanning probe tip by testing a surface with ver- tically grown carbon nanotubes. The tip was scanned over the sample using a type of magnetic conveyor belt. The first measurements in the so-called “contact mode” revealed how the tall tubes stripped some atoms out of the atom cloud. These atom losses told the researchers about the location and height of the nanotubes and enabled the imaging of the surface topography.

11-05 :: May/June 2011

When the temperature of an atomic gas approaches absolute zero, a quantum mechanical phenomenon occurs, turning the cloud into what’s known as a Bose-Einstein condensate. In this state it is no lon- ger possible to distinguish between the atoms. They become, so to speak, a single, giant “super-atom”. With such a Bose-Einstein condensate it was possible for the Tübingen scientists to microscopically resolve individual freestanding nanotubes. According to the