Environmental dependence of thermal oxidation behaviour 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 that initially were only mildly oxidized before annealing, but their behaviour upon annealing in a vacuum differed substantially, depending on the environ ment in which they resided. X-ray photoelectron spectroscopy analyses revea led that the unencapsulated nanoparticles tended to oxidize quite quickly, whereas the nanoparticles sandwiched between layers of Al2O3 matrices were oxidized very slowly even under intense annealing. In the zinc/silicon nano crystalline mixture, oxidation of the Si-0 state was even faster than that of the intermediate Si (+1,+2and+3) states. Both the stability and formatio n processes of the Si-O bonds in the partially oxidized states differed con siderably 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. Copyright ( C) 2001 John Wiley & Sons, Ltd.