Manipulation of Nanoparticles for Quantum and Single-Electron Devices

Sammanfattning: In this thesis a technique to manipulate nanoparticles with an atomic force microscope (AFM) is presented. Particles in the size range of 5-500 nm could be positioned in arbitrary two-dimensional patterns on different surfaces by mechanically pushing them with the AFM tip. The technique which is material-independent can be applied to any type of nanometer-sized particles or objects that are free to move on a surface. Results from semiconductor and metal aerosol particles, as well as metal discs defined by electron-beam lithography are presented. The AFM manipulation technique is combined with in-situ electrical measurements of device properties for the fabrication of nanodevices based on conductance quantization and single-electron charging effects. By moving gold nanoparticles into contact with gold electrodes separated by a small gap, atomic-scale contacts were fabricated, which exhibited quantized conductance steps and could be tuned to predefined quantized conductance values. In addition, two different techniques to build single-electron devices are presented: (i) The mechanical tuning of tunnel gaps with gold or palladium discs and (ii) by using oxidized indium aerosol particles as the central island. In the first technique gaps, only a couple of Å wide could be produced, with potential applications not only as tunnel junctions but also for the investigation of single molecules. Single and double-island single-electron transistors (SETs) were fabricated, with gate oscillations being observed at temperatures up to 25 K.