Quantum Devices from the Assembly of Zero- and One-Dimensional Building Blocks

This thesis describes novel methods for the fabrication of nanometer-scale electronic devices, such as single-electron transistors and resonant tunneling diodes, from wire- and dot-shaped building blocks. The first part of the thesis describes the manipulation of metal nanoparticles and carbon nanotubes using an atomic force microscope. Single-electron transistors were realized by moving nanotubes and nanoparticles in electrical contact with metal electrodes. It is shown that various forms of carbon nanotubes can be used as mobile electrodes resulting in very small electrical switches. In particular, the use of carbon nanotubes as electrodes was demonstrated by electrically contacting a sub-10 nm gold particle with two nanotubes. This device showed single-electron charging effects up to 200 K.

The second part of the thesis deals with the fabrication and electrical characterization of semiconductor nanowire devices. Nanowires in the InAs/InP material system were grown by chemical beam epitaxy from size-selected nanoparticle catalysts. The heterostructure interfaces between the InAs and InP regions were determined to be almost atomically abrupt from high-resolution transmission electron microscopy investigations. Ohmic contacts, showing linear I-V characteristics down to 4.2 K, were developed to homogeneous InAs nanowires, and transport in these wires was investigated. From electrical characterization of InAs nanowires containing a thick InP barrier, the InP barrier height was estimated to be ~0.6 eV relative to the InAs conduction band edge. Resonant tunneling diodes were fabricated by incorporating a 15 nm InAs dot between two thin InP tunnel barriers. These devices showed peak-to-valley ratios up to 50:1 at 4.2 K. It is also shown that if the InAs dot is extended to a length of 100 nm, the nanowires work as ideal single-electron transistors at 4.2 K.