Electron-stimulated desorption of F + and F − from SF 6 on Ru( [formula omitted]): structure and bonding

Abstract

The adsorption properties and bonding geometry of octahedrally coordinated SF 6 molecules are studied on Ru(0 0 0 1) for coverages less than 1 ML. Temperature programmed desorption reveals predominantly molecular adsorption of SF 6 at 25 K; desorption occurs below 100 K. Electron stimulated desorption ion angular distributions of both F + and F − ions demonstrate halo-like patterns. Heating the substrate to ∼90 K results in transformation of the halo-like patterns into hexagonal angular distributions for both ions. Electron-stimulated desorption of the ions occurs via different mechanisms, but from the same chemical states. SF 6 appears to be adsorbed via three F atoms, with the other three pointed away from the surface. At low temperatures, the S–F bonds have a random azimuthal orientation, while upon annealing, lateral ordering occurs in two complementary domains. Low energy electron diffraction reveals no evidence of long range order in the adsorbed layer.