Surfactant enhanced solid phase epitaxy of Ge/CaF{sub 2}/Si(111): Synchrotron x-ray characterization of structure and morphology

The structure and morphology of CaF{sub 2}/Si(111) and Ge/CaF{sub 2}/Si(111) layered structures with film thicknesses in the range of very few nanometers has been studied with synchrotron-based radiation. While the CaF{sub 2} film is grown via molecular beam epitaxy, the Ge film is fabricated by surfactant enhanced solid phase epitaxy with Sb as surfactant. The CaF{sub 2} film forms two laterally separated phases of relaxed CaF{sub 2} and pseudomorphic CaF{sub 2}, respectively, although the film thickness is very homogeneous. The Ge film is completely relaxed and forms A-oriented parts as well as B-oriented parts, due to twinning. In spite of the large surface roughness of the Ge film, it completely wets CaF{sub 2}/Si(111) also after annealing at 600 deg. C, due to the application of Sb during the annealing process.