Homogeneous Si films on CaF2/Si(1 1 1) due to boron enhanced solid phase epitaxy

The structure and morphology of Si/CaF2/Si(1 1 1) structures have been investigated by X-ray diffraction (XRD, GIXRD) and X-ray photoelectron spectroscopy (XPS). While CaF2 films were grown via molecular beam epitaxy (MBE), Si films on CaF2/Si(1 1 1) are fabricated by surfactant enhanced solid phase epitaxy (SE-SPE). Here Boron was used as a surfactant to obtain semiconductor films of homogeneous thickness. The Si films are entirely relaxed while the CaF2 films have both pseudomorphic and relaxed crystallites. After exposure to ambient conditions, the Si films have a very thin native oxide film. The homogeneous Si film partially prevents the incorporation of impurities at the interface between the Si substrate and CaF2 via migration along residual defects of the CaF2 film.