Accession Number : AD0714691

Title :   Surface Studies by Low-Energy Electron Diffraction.

Descriptive Note : Final rept.,

Corporate Author : WISCONSIN UNIV MADISON DEPT OF PHYSICS

Personal Author(s) : Webb,Maurice B.

Report Date : OCT 1970

Pagination or Media Count : 11

Abstract : Low-energy electron diffraction offers the potential for surface crystallography analogous to x-ray and neutron studies of the bulk. This potential has not been fully realized because of the strong interactions, both elastic and inelastic, between the electron and the crystal. The report summarizes experiments done in an effort to achieve sufficient understanding of the diffraction to realize this potential. Studies on the scattering from Ni at high temperatures and from liquid Hg established that: (1) the atomic scattering factor for backward scattering is essentially the same for free atoms and those in the condensed phase; (2) multiple scattering processes are strongly attenuated by inelastic processes; (3) roughly half the elastically back scattered electrons have interacted only once; (4) penetration depths are the order of 1-3 atomic spacings. Other studies establish quantitatively a two step process for the inelastic scattering for small energy losses and allow determination of the loss function and show that the surface loss contributions are dominant. Careful studies as a function of T and all the diffraction variables have determined detailed properties of the elastic scattering from Ag(111) and Ni(111) including the azimuthal symmetry, Debye Waller factors as a function of energy, effective thermal expansion. (Author)

Descriptors :   (*ELECTRON DIFFRACTION, SURFACES), (*CRYSTAL STRUCTURE, SURFACES), MERCURY, NICKEL, SILVER, BACKSCATTERING

Subject Categories : Physical Chemistry
      Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE