Langmuir, Vol.12, No.14, 3472-3480, 1996
An Electron-Stimulated Desorption Ion Angular-Distribution and Low-Energy-Electron Diffraction Investigation of CF3I on Ru(001)
We have investigated the structures of CF3I, and its dissociation products, adsorbed an Ru(001) using low-energy electron diffraction and electron-stimulated desorption ion angular distribution (ESDIAD). Atomic iodine forms (root 3x root 3)R30 degrees islands even at very low coverages. At 70% of saturation and above, a (2x2) superstructure forms which we attribute to a p(2x2) unit cell with one CF3 group and one iodine atom. ESDIAD images show F+ desorbing at normal emission and in three hexagonal patterns. The normal emission is attributed to a tilted configuration of CF3(ad) in which one C-F bond is oriented perpendicular to the surface. A small hexagon is attributed to F(ad) on step edges. A large hexagon at low coverages may arise from isolated CF3(ad) species possessing C-3v symmetry. And finally, an intermediate hexagon is attributed to perturbation of the CF3(ad) orientation by molecular fragments which result from electron irradiation of physisorbed CF3I.