Strontium silicide termination and silicate epitaxy on (001) Si

We have investigated the epitaxial growth of (Sr,Ba)-based oxides on SrSi2-terminated (001) Si using laser-molecular beam epitaxy. Reflection high-energy electron diffraction (RHEED) confirms the formation of a commensurate submonolayer of (Ba,Sr)Si-2 when strontium and barium ablation targets are used as the metal sources. Stability of the silicide RHEED peak intensity between laser ablation pulses indicates that the submonolayer SrSi2 coverage is relatively stable during formation despite the required high temperatures. While the subsequent growth of BaO via Ba metal ablation and O-2 flux on the SrSi2-terminated surface is favored at low temperatures, the formation of an epitaxial silicate is observed for oxide formation at temperatures above 550degreesC. X-ray diffraction confirms that the Ba2SiO4 film formed with elevated temperature oxidation is in-plane aligned. These results suggest that while epitaxial BaO can be realized on SrSi2-terminated Si, the interface may be susceptible to silicate formation upon thermal treatment. These results also demonstrate that laser-molecular beam epitaxy can be effective in achieving submonolayer surface coverage specifically for terminating silicon for oxide epitaxy. (C) 2002 American Vacuum Society.