Properties of 1D metal-induced structures on semiconductor surfaces

In 1965 Gordon Moore stated that every 12 months a doubling of the number density of transistors placed on an integrated circuit will take place [1]. Up to now this law still holds, however, a limit to this law will be reached soon. When using the conventional ‘top-down’ approach for fabrication of electronic circuits and devices we are limited in scaling down the lateral size of electronic devices. With optical lithography the resolution is limited by the wavelength of the light. This thesis deals mainly with the creation of 1D (but also 2D and 3D) nanostructures, produced via the ‘bottum-up’ approach. With the term ‘bottom-up’ approach we mean a self-organization approach to nanofabrication using chemical or physical forces. Nature is capable of harnessing chemical forces for the creation of all the structures that are needed for life. And we like to take this example of nature’s ability and let atoms and small clusters of atoms self-organize into nanosized structures. Three different metals deposited on semiconductor surfaces form the bulk of this thesis. Firstly, the gold (Au) on germanium (Ge)(001) system, where Au atoms together with Ge atoms self-organize into very narrow and long nanowires. These Au-induced nanowires have the potential to serve as a model system for a 1D electron system. Secondly, cobalt- (Co) induced nanostuctures on Ge(001) and Ge(111) are studied. Nanosized crystals and islands are observed of which some show metallic behavior. Finally, iridium (Ir) nanowires are studied, showing a growth behavior that is stabilized by quantum confinement of Friedel oscillations.