The surface structure of Ag/W(100) has been studied using LEED and Low Energy Ion Scattering Spectroscopy (ISS). We find that Ag coverages are saturated at 0.5 ML after annealing at 800°C regardless of the initial coverages between 0.7~1.0 ML. We observe a c(2×2) image after annealing the Ag/W(100) sample at 800°C. Using the ISS technique the adsorption site of Ag on the c(2×2) surface is found to be the center of the nearest two atoms on the W(100) surface. The height of the Ag adsorption layer is 1.58 Å above the W(100) surface.

The atomic structure of reconstructed Si(001)c(4 x 4)-C surface has been studied by coaxial impact collision ion scattering spectroscopy. When the 100L of ethylene (C(2)H(4)) molecules have been exposed on Si(001)-(2 x 1) surface at 700 degrees C, it is found that C atoms cause the ordering of missing Si dimer defects and occupy the fourth layer of Si(001) directly below the bridge site. Our results provide the support for the previous model in which a missing dimer structure is accompanied by C incorporation into the subsurface.

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