Micromanipulation of individual InAs nanowires

We investigated methods to manipulate InAs nanowires using micromanipulators, an optical microscope as well as atomic force microscopy with the goal to produce InAs tips for scanning tunneling microscopy. Within the optical microscope, the InAs wires with diameters of approximately 100 nm and length up to 12 μm can be identified as colored stripes (1000 magnification) due to the diffraction of light. The wires, which have been grown by metalorganic vapor phase epitaxy (MOVPE) on a GaAs wafer without catalyst, could be picked up individually using the sharp corner of a doubly cleaved wafer exploiting adhesion forces. Later, the wires are placed onto a desired position at the edge of another wafer. Contacting of the wires is accomplished using indium microsoldering, which leads to a two-point resistance down to 1.5 kΩ. First STM measurements, however, did not reveal a tunneling current probably due to oxidation of the tip. Different etching procedures have been tested in order to remove the oxide of the wire.