YSi2-x films were grown by ion-assisted evaporation in an ultrahigh vacuum (UHV) on Si(111) through a thin SiO2 layer. The films grown on the oxidized Si were changed from a polycrystalline structure with various phases of oxides and silicides into a single-crystalline silicide structure as the annealing temperature was increased in the UHV chamber. The structural change with the annealing temperature implied that various Y2O3 phases formed by the reaction between Y and SiO2 were decomposed and transformed into YSi2-x under the UHV environment. Rutherford backscattering spectroscopy/channeling showed that, although the interfacial crystallinity of the film grown on the SiO2 layer was poorer quality than the film grown on a clean Si surface, a single crystalline YSi2-x layer with high crystallinity (chi(min)=8) was grown. These results showed that the difference of the thermal energy and the formation energy between the oxides of Y2O3-SiO2 and yttrium silicide determined the evolution of the silicide layer formation and its crystal structure. (C) 2002 American Institute of Physics. References: 15
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