A Theoretical and Experimental Investigation of Surface Structures and Gas-Surface Interactions

The object of this thesis is to study gas-surface interactions in general, and the geometrical structures of surface and overlayers in particular. Low-energy electron diffraction is employed to determine the structure of both clean metal surfaces and overlayers. In addition, an analysis of thermal desorption mass spectrometry is presented. In part II, a convolution-transform method of LEED analyses is described which has proved to be able to determine either contraction or expansion of the crystal surface. The results of analyses of clean Al(110), Ag(110), Ni(110), Rh(111) and Pt(111) surfaces obtained by this method are comparable with those obtained by more complicated dynamical calculations~ Our results indicate that both (111) surfaces have the same structure as the bulk with a slight expansion or contraction of the topmost layer of atoms by less than 5% of the bulk interlayer spacing. The analyses of the fcc(110) surfaces reveal that a contraction of 4%, 5% and 7% of the bulk interlayer spacing occurs on the Al(110), Ni(110) and Ag(110) surfaces. In part III, the atomic arrangement of general surfaces of Ir is discussed, namely, the (111), the reconstructed (110)-(1x2), and the unreconstructed (110) surface. Also, the surface structure of atomic overlayers of both oxygen and sulfur on these surfaces have been analyzed. Finally, the Debye temperature characteristics of both these surfaces of clean iridium are presented and compared.