Ionic potential analysis of RHEED rocking curves from fluoride structures

Rocking curves of reflection high energy electron diffraction from MnF2 and CaF2(1 1 1) surfaces have been calculated with ionic scattering potentials. The potentials were derived from tabulated X-ray scattering factors and expressed in the Doyle–Turner representation. The Coulomb potential of the ions was introduced into the calculations of diffracted intensity using dynamical diffraction theory. Comparison of the calculated and measured rocking curves for CaF2(1 1 1) surface confirmed that it is bulk terminated; the correction to volume average potential was found to be 1.1 eV (much less than when using atomic potentials). Analysis of the rocking curves from ultra-thin MnF2 layers on CaF2(1 1 1) indicated that MnF2 inherits the cubic lattice of fluorides up to a thickness of three molecular layers.