Surface chemistry and directed assembly of nanostructures on dielectric surfaces

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Stanley, Scott Kendyl

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Surface chemistry and nanoparticle growth relevant for flash memory applications has been investigated with a number of surface science techniques and imaging methods. Germanium chemistry on SiO2 surfaces is investigated and a series of temperature dependant sequential reactions are identified explaining how Ge reactively etches SiO2 at low temperatures. These reactions hinder the accumulation of Ge adatoms on SiO2 surfaces during chemical vapor deposition (CVD). Germanium is seen to form an unusually stable contacting oxide on HfO2 surfaces and nanoparticles may be grown on HfO2 during CVD. The surface chemistry of Si is also examined on both SiO2 and HfO2 surfaces and Si is seen to be relatively stable on both surfaces, with only slight difference in desorption kinetics. A kinetically-driven patterning scheme was developed to direct the self assembly of nanoparticles within top-down defined regions on the surface by exploiting the reaction kinetics of Si and Ge. Using this method, adatoms are corralled into top-down defined regions where they bottom-up self assemble to form nanoparticles and no nanoparticles form elsewhere. The effect of feature size on the self assembly of nanoparticles is studied and reactive pathways for adatoms in confined spaces are examined.