Growth and etching on silicon(113) and silicon(5 5 12) surfaces

• Main Author: Dickinson, Jonathan W
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2004
• Subjects: Chemistry; Condensation; Condensed matter physics; Physical chemistry
• ISBN: 9780496880485; 0496880489

This dissertation concerns morphological studies of self-assembled structures formed on silicon surfaces. Real-space images of the surfaces are obtained using the techniques of scanning tunneling microscopy (STM) and atomic force microscopy (AFM). The studies concern the growth of a rare earth metal (Gd), noble metal (Au) and oxygen nucleation and etching on the high-index Si(113) and Si(5 5 12) surfaces. These anisotropic surfaces are two of the three stable orientations existing between the low-index (001) and (111) planes. In general, it is found that the Si(5 5 12) surface is not stable after metal growth or oxygen etching, instead forming facets in most cases to the nearby (113) plane. In contrast, the (113) surface does not form facets after growth or etching, indicating the stability of this high-index orientation. In the case of Au deposition, the Si(5 5 12) surface forms sawtooth facets that typically incorporate (113) planes opposed by (7 7 15), (337), or (5 5 11) planes. The Au coverage and annealing temperature determine the resulting structures, which always incorporate single-domain, row-like surface structures with inter-row spacings ranging from 2.2 nm to 3.5 nm. The Au/Si(113) system is found to remain planar, but does not form any well-ordered surface reconstructions. With regard to Gd growth on these surfaces, it is found that both Si(113) and Si(5 5 12) provide interesting templates for the growth of silicide nanowires, similar to that seen earlier for Si(001). Here, the Si(113) surface is more interesting because the nanowires grow on well-ordered terraces terminated by a 2 x 2 surface reconstruction. The Si(5 5 12) surface is found to be unstable and forms (113) facets that disrupt the overall surface morphology. Finally, the oxygen etching behavior of both surfaces is examined for a range of sample temperatures (675 to 800°C) and exposures (10 to 400 L). At lower temperatures and exposures, both surfaces show oxide-induced pinning sites or islands that affect etching of the surrounding terrace structure. Due to the anisotropic nature of these surfaces, such islands preferentially occur at the more reactive step edges. At higher temperatures and exposures, the surfaces show significantly different behavior. The Si(113) surface appears to be more thermodynamically stable and remains planar with some anisotropic islands being produced. In contrast, the Si(5 5 12) surface is not stable to prolonged etching and produces a sawtooth structure composed of (113) and (111) facets.