Structural and luminescence studies of CdF2single bondCaF2 superlattices on Si(111)

Symmetric short period CdF2single bondCaF2 superlattices (SLs) on Si(111) were grown by molecular beam epitaxy. Their structural perfection was studied by X-ray diffraction. Calculations of strains from measured rocking curves and subsequent simulations of the curves showed that such structures can be grown pseudomorphically at temperatures about 100°C. Studies of luminescence in non-activated SLs revealed shifts of band energy position of self-trapped excitons caused by their wave function mixing at CaF2/CdF2 interfaces. In SLs where calcium fluoride layers were doped with Eu, intensity of luminescence of Eu2+ ions was found to decrease with time. This effect was proved to be due to tunneling of electrons from the excited state of Eu2+ to the conduction band of cadmium fluoride. Unlike plain CdF2:Eu layers, well pronounced sharp Eu3+ lines were observed in cathodoluminescence spectra of all superlattices.