Channelling measurements on single crystal caf₂overlaid with gold and calcium fluoride films

Abstract

Backscattering measurements on (1 1 I)-oriented CaF, crystals covered with evaporated films of gold or calcium fluoride have been made using 2.0 MeV 4He ions and 4.0 MeV protons. Measured angular yield profiles' for different layer thicknesses have been compared with calculated profiles obtained from scattered particle distributions due to Sigmund and Winterbon but using different assumptions about the de-channelling process. For gold films the calculated aligned yields and half angles of the angular yield profiles are in good agreement with measurements. For calcium fluoride films good agreement is obtained between the measured and calculated aligned yields if the scattering contribution from the fluorine atoms is treated as a correction to the dominating scattering from the Ca atoms.