Scanning probe microscopes are widely used to study surfaces with atomic resolution in many areas of nanoscience. Ultracold atomic gases trapped in electromagnetic potentials can be used to study electromagnetic interactions between the atoms and nearby surfaces in chip-based systems. Here we demonstrate a new type of scanning probe microscope that combines these two areas of research by using an ultracold gas as the tip in a scanning probe microscope. This cold-atom scanning probe microscope offers a large scanning volume, an ultrasoft tip of well-defined shape and high purity, and sensitivity to electromagnetic forces (including dispersion forces near nanostructured surfaces). We use the cold-atom scanning probe microscope to non-destructively measure the position and height of carbon nanotube structures and individual free-standing nanotubes. Cooling the atoms in the gas to form a Bose-Einstein condensate increases the resolution of the device.

No abstract

We demonstrate an atom detector based on field ionization and subsequent ion counting. We make use of field enhancement near tips of carbon nanotubes to reach extreme electrostatic field values of up to 9 × 10 9 V/m, which ionize ground state rubidium atoms. The detector is based on a carpet of multiwall carbon nanotubes grown on a substrate and used for field ionization, and a channel electron multiplier used for ion counting. We measure the field enhancement at the tips of carbon nanotubes by field emission of electrons. We demonstrate the operation of the field ionization detector by counting atoms from a thermal beam of a rubidium dispenser source. By measuring the ionization rate of rubidium as a function of the applied detector voltage we identify the field ionization distance, which is below a few tens of nanometers in front of nanotube tips. We deduce from the experimental data that field ionization of rubidium near nanotube tips takes place on a time scale faster than 10 −10 s. This property is particularly interesting for the development of fast atom detectors suitable for measuring correlations in ultracold quantum gases. We also describe an application of the detector as partial pressure gauge.

No abstract

No abstract