Nanosystems via self-assembly: Size distribution control, spatial positioning and wiring of germanium dots on silicon(111)

We have adapted an unconventional technique called pulsed laser deposition (PLD), for the growth of Ge dots on Si(111). A laser beam ablates a Ge target which ejects high energy particles which have been identified using quadrupole time of flight mass and linear time of flight mass spectrometry as monoatomic neutral Ge and Ge+ species. The size of the Ge dots on Si produced at a deposition temperature of 600°C and fixed growth rate can be varied to achieve small dots with a narrow size distribution by varying the laser fluence (energy density). Unfortunately, characteristic of this type of self-assembly system no spatial ordering of the dots were observed.; A second approach to controlling the dot size and size distribution involved using pre-deposited C60 on the Si substrate. This addition to the surface induced Ge dots during dot growth, below the normal critical thickness. The resulting dot size distribution was narrower by 50% compared to dots growth without C60 when characterized by atomic force microscopy (AFM). Temperature studies were done in order to assess the effect of C60 on the surface kinetics of Ge adatoms during dot growth. It was found that the activation energy for diffusion on a C60/Si(111) prepared surface was 0.52 +/- 0.02eV compared to 0.35 +/- 0.09 eV for Ge on bare Si(111) meaning the presence of C60 should reduce the surface diffusion of Ge adatoms. Another allotrope of C was investigated in the form of carbon nanotubes (CNTs). Ge dots grown the Si(111) surface with pre-deposited CNTs resulted in a random spatial distribution of the dots, however a few dots were found to assemble atop the CNTs.; In order to induce predictable spatial ordering the Si(111) surface was patterned using an unconventional lithographic technique called nanosphere lithography. A colloidal solution of polystyrene nanospheres was deposited on the Si surface which conveniently led to a self-assembled monolayer with a close packed arrangement of spheres upon evaporation of the solvent. The monolayer of spheres was then used as an etch mask during reactive ion etching to produce a variety of self-wired Si nanostructures which included nanopillars, nanospikes, nanorings and rings atop nanopillars as observed by scanning electron microscopy (SEM). These structures were cleaned and then used as a new substrate for Ge dot growth.; Thin films of Ge were grown on the newly patterned Si substrates, using molecular beam epitaxy, in order for Ge dots to self-align. Using both AFM and SEM, we discovered that at 575°C single Ge dots formed atop each nanopillar. (Abstract shortened by UMI.)...