Growth and characterization of compositionally graded (ca, sr)f2 layers on si(111) substrates

Epitaxial insulator films composed of compositionally fixed (Ca, Sr)F2/compositionally graded (Ca, Sr)F2/CaF2 multilayers have been grown on Si(111) substrates by the coevaporation of CaF2 and SrF2 from two separate crucibles The dependence of the channeling minimum yields on the energy of incident ions in Rutherford backscattering spectroscopy revealed that defects in the top fluoride layers were mainly dislocations. The dislocation density could be reduced by decreasing the compositional gradient of the underlying graded layers and decreasing the growth temperature. As a result of the reduced dislocation density, the generation of cracks in fluoride films could be suppressed.