THE SEARCH FOR MATERIALS WITH SELF-ASSEMBLING PROPERTIES: THE CASE OF Si-BASED NANOSTRUCTURES

摘要

This work describes an effort to seek for new materials capable of self-assembly of nanostructures, such as dots and wires, for electron-confined devices. A good candidate is a metal-semiconductor compounds group, most notably metal silicides. As will be shown below, the disilicides of cobalt and titanium form distinct nanodot arrays on silicon, of a significantly smaller mean size, and substantially improved size and shape uniformity, as compared to Ge/Si arrays. In order to achieve that, not only the deposition parameters were carefully controlled, but the Si-substrate orientation seemed to play an important role, as well. In the case of CoSi2, small and uniform dots resulted from reactive deposition epitaxy at 800 K on Si(001), whereas TiSi'2 dots required Si(lll) substrate orientation to form even more uniform, small and isotropic nanodot array. In both cases reacting the metal with silicon in a solid state, and/or on differently oriented substrates did not produce the desired result.