PHOTOELECTRON DIFFRACTION IMAGING OF A SURFACE ALLOY

Photoelectron diffraction imaging (PDI) has been used to determine the surface structure of a surface alloy. Direct two-dimensional imaging of the surface plane has been achieved by Fourier transformation of ex perimental energy-dependent photoelectron diffraction (EDPD) data. Thi s imaging method, based upon the Fourier transformation of diffraction oscillations with energy and a summation over angular contributions, can provide vectorial atomic positions with atomic resolution. A new r apid data collection mode is introduced and tested by comparison with previously developed modes of photoelectron diffraction. Surface struc tural sensitivity was confirmed by comparison with multiple-scattering simulations. The previously ambiguous surface geometry of c(2 x 2) Au /Cu(001) has been determined, with clear, non-model-dependent discrimi nation of the surface alloy over the overlayer structure.