Geordnete Nanoteilchen-Ensembles auf Oberflächen: Herstellung, thermische Stabilität und Anwendung als Ätzmaske

Abstract

This thesis deals with the preparation and characterization of ordered nanostructures on surfaces. The basis for this preparation-process is a method developed at the University of Ulm to prepare ordered nanoparticles on surfaces by loading reverse polymer-micelles with metal salts as precursors. Gold-nanoparticles obtained by this technique were analyzed with respect to their thermal stability and the applicability as a mask to structure the underlying substrate. One main topic of this work was to determine the size-dependent heat of sublimation by means of thermal desorption spectroscopy. It could be shown that, no Ostwald-ripening or diffusion of particles occurs, when annealing gold-particles prepared by the micellar technique on sapphire. Nevertheless, the determination of the size-dependency of the heat of sublimation was not possible with the chosen system. It turned out, that due to outgassing of oxygen, an aluminium-rich surface was generated on top of the sapphire substrate. This leads to a strongly bound thin layer of gold atoms at the interface between the particle and the substrate leading to the measurement of two desorption processes with different activation energies and desorption frequencies. As a possible technological application for hexagonally ordered nanoparticles prepared using micelles, their applicability as a mask for structuring underlying substrates were tested. An anisotropic etching process was developed that makes the preparation of up to 45nm high diamond tips possible. The characterization by STM and STS as well as measurements in diode configuration showed that, tips made from boron-doped diamond exhibit enhanced field-emission of electrons. It could be shown that exploiting micellar nanoparticles, the formation of uniform field-emitters on a large substrate is possible. These tips could serve as an electron-source in future field-emission displays.