We were able to synthesize an epitaxial metastable FeSi1-x (x = 0.15) phase with the defective CsCl structure on Si(111) as well as on MgO(100) with an iron buffer layer. We compared CEMS and RBS/channeling measurements for samples with different film thicknesses. From X-ray diffraction measurements, we could derive the lattice parameter of the cubic structure on the different substrates. On Si(100) the FeSi1-x phase with defective CsCl structure was not observed. CEMS measurements revealed a lower than cubic site symmetry for the iron atoms and no epitaxy was observed for the latter samples.