RHEED ROCKING CURVES FROM FLUORIDE(111) SURFACES

Rocking curves of reflection high energy electron diffraction from the (111) face of CaF2, SrF2 and BaF2 were measured and compared with cal culated results. The calculated curves were obtained from a dynamical diffraction theory for a bulk terminated surface with the volume avera ge potential as a fitting parameter. The agreement achieved was good f or CaF2, reasonable for SrF2 and satisfactory for BaF2. This suggests that the surfaces could be close to being bulk terminated. The results also demonstrate the importance of ionic scattering potentials which will need to be considered in future studies of RHEED from fluoride su rfaces.