Contacting of individual InAs nanowires without photoresist

We investigated methods to spacially control InAs nanowires on a substrate using micromanipulators attached to an optical microscope with the goal of producing InAs tips for scanning tunneling microscopy. The wires, which were grown by metalorganic vapor phase epitaxy (MOVPE) on a GaAs wafer without catalysts, could be picked up individually using a sharp indium tip exploiting adhesion forces. Later, the wires were placed onto a desired position somewhere on or at the edge of a double cleaved wafer. Contacting the wires was accomplished using indium microsoldering or electron beam induced deposition, since standard lithographic methods are not possible close to the wafer edge due to non-uniform photoresist thickness. Several variations of contacting the wires and optimizing the InAs/metal interface were tested and ohmic contacts could be realized.