Real-space surface crystallography: Experimental stereographic projectionsfrom ion scattering

Scattering and recoiling imaging spectrometry (SARIS) in the blocking confi guration is used to obtain experimental two-dimensional stereographic proje ctions of the Ni(110) and Pt(111) surfaces. The development of this techniq ue as an element-specific real-space surface crystallography that is sensit ive to interatomic spacings in the surface and subsurface layers of a cryst al is described. This projection imaging method is based on the blocking of atomic trajectories scattered from subsurface layers by atoms in layers ne arer to the surface. The resulting magnification of the blocking cones, as captured by a gated position-sensitive microchannel plate detector, is simi lar to 10(9). The images of the blocking patterns provide direct informatio n on interatomic spacings and surface symmetry and structure. Classical ion trajectory simulations using the three-dimensional scattering and recoilin g imaging code (SARIC) are used to simulate the stereographic projections a nd blocking patterns and to provide quantitative interpretations. The metho d is sensitive to interatomic spacings in the surface and subsurface layers . The physical properties of the blocking process are derived from analysis of the data and a simplified, approximate, two-atom model of the scatterin g/blocking process is developed. (C) 2000 American Institute of Physics. [S 0021-9606(00)71216-5].