3-DIMENSIONAL FOCUSING PATTERNS OF HE+ IONS SCATTERING FROM A AU(110)SURFACE

Three-dimensional focusing patterns have been observed for 4 keV He+ s cattering from a Au{110}-(1 x 2) surface for beam incident angles high er than the Lindhard critical angle. Under these conditions, the scatt ered atoms are highly focused by the detailed structural features of t he surface and subsurface layers into non-planar directions, giving ri se to intricate symmetrical and asymmetrical spatial patterns in accor d with the crystal azimuths involved. These scattering patterns can be readily observed through the use of a time- and spatially resolving m icrochannel plate detector using the technique of scattering and recoi ling imaging spectrometry (SARIS). Such non-planar scattering features are not normally observed in conventional ion scattering experiments using small-area detectors. The features of the images can be interpre ted qualitatively by means of a simple blocking-cone analysis. Classic al ion trajectory simulations using the scattering and recoiling imagi ng code (SARIC) are used to simulate the scattering patterns, to delin eate the surface and subsurface layers involved in the scattering, and to illustrate the focusing of incoming and outgoing ion trajectories involved in producing various features of the images. (C) 1997 Elsevie r Science B.V.