DEPENDENCE OF THERMAL OXIDATION BEHAVIOR OF SILICON NANOCRYSTALLITES

Three kinds of nanosilicon crystallites were prepared by different methods in high vacuum. All of them were composed of tiny silicon crystallites which were initially only mildly oxidized before annealing, but their behavior upon annealing in vacuum differed substantially depending on the environment in which they resided. XPS analyses revealed that the unencapsulated nanoparticles tended to oxidize quite quickly, whereas the nanoparticles sandwiched between layers of Al 2 O 3 matrices were oxidized rather slowly even under intense annealing. In the zinc/silicon nanocrystalline mixture, the oxidation of the Si 0 state was even faster than that of the intermediate Si +1,+2,+3 states. Both the stability and formation processes of the Si - O bonds in the partially oxidized states differed considerably with different environmental surroundings. However, in all cases, the Si - O bonds of the fully oxidized Si +4 state remained the most stable, to which the less oxidized states tend to gravitate eventually.