One of the biggest limitations of conventional carbon nanotube device fabrication techniques is the inability to scale up the processes to fabricate a large number of devices on a single chip. In this report, we demonstrate the directed and precise assembly of single-nanotube devices with an integration density of several million devices per square centimeter, using a novel aspect of nanotube dielectrophoresis. We show that the dielectrophoretic force fields change incisively as nanotubes assemble into the contact areas, leading to a reproducible directed assembly which is self-limiting in forming single-tube devices. Their functionality has been tested by random sampling of device characteristics using microprobes.

We investigate nanocontact formation by thermally assisted electromigration of gold nanowires. An automatic cycling process allows us to follow a line of constant power dissipated at the nanocontact up to resistances corresponding to 10–20 conductance quanta. The contacts are thinned in a controlled way by voltage-induced heating. In the ballistic regime, oscillations of the conductance histograms show oscillations typical for atomic discreteness.

Using indium as catalyst for growth and simultaneously as doping source, ordered arrays of n-type ZnO single crystal nanorods have been perpendicularly grown on p-GaN∕Al2O3 substrates with a vapor phase transport growth method. The low temperature photoluminescence measurements of the n-ZnO nanorods show dominant In-related neutral donor bound exciton emission in the ultraviolet region. Electrical transport measurements performed on single n-ZnO nanorods yield resistances of about 50–200kΩ and a typical specific resistivity of 2.0×10−2Ωcm. The resistivity is one order of magnitude reduced by introducing In compared to the nominally undoped ZnO nanorods.

ZnO nanorods were implanted with Ga+ ions in a combined scanning-electron-microscope/focused-ion-beam system with doses from 1011to1017cm−2. Electrical resistance measurements performed on single ZnO nanorods yield first an increase of the resistance due to defect formation which lowers the electron mobility. Implantation doses exceeding 1015cm−2 yield a strong decrease of the resistance to values significantly below the resistance before Ga+-ion implantation. Low specific resistivities of about 3×10−3Ωcm are reached without additional annealing treatment after high-dose implantation.

The spin polarization P of the transport current through the interface between superconducting Al and ferromagnetic Fe is determined by means of Andreev reflection at nanostructured point contacts. We observe a systematic decrease of P with decreasing contact resistance. Our data provide evidence for the reduction of P by spin-orbit scattering and thus establish a link between density of states and transport spin polarizations.