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In order to understand the physics of radiation-induced proton density decay in thin SiO/sub 2/ films, we performed ab initio Hartree-Fock calculations of the potential energy curves for the interaction between model oxide clusters and H in two charge states. The calculated results led to two separate proposed mechanisms for proton density decay in thin SiO/sub 2/ films: (1) electronic excitation involving hot phonon levels of the ground electronic state at low photon-energy radiation and (2) electron capture by protons at high photon-energy radiation. The proposed mechanisms qualitatively explain recent experimental observations.

Preface. Structure and Topology. Defect-free vitreous networks: The idealised structure of SiO2 and related glasses A.C. Wright. Topology and topological disorder in silica L.W. Hobbs, X. Yuan. Bulk Defects. Optical properties of defects in silica L. Skuja. The natures of point defects in amorphous silicon dioxide D.L. Griscom. Ab initio theory of point defects in SiO2 G. Pacchioni. A demi-century of magnetic defects in alpha-quartz J.A. Weil. Interaction of SiO2 glasses with high energy ion beams and vacuum UV excimer laser pulses H. Hosono, K. Kawamura. Excitons, localized states in silicon dioxide and related crystals and glasses A.N. Trukhin. Gamma rays induced conversion of native defects in natural silica F.M. Gelardi, S. Agnello. Ge and Sn doping in silica: structural changes, optically active defects, paramagnetic sites A. Paleari. Computational studies of self-trapped excitons in silica L.R. Corrales, et al. Surface Defects. Defects on activated silica surface V.A. Radzig. Ab-initio molecular dynamics simulation of amorphous silica surface M. Bernasconi. Bragg Grating. periodic UV-induced index modulations in doped-silica optical fibers: formation and properties of the fiber Bragg grating C.G. Askins. Bulk silicas prepared by low presssure plasma CVD: formation of structure and point defects K.M. Golant. Change of spectroscopic and structural properties of germanosilicate glass uner mechanical compression and UV irradiation V.M. Machinsky. UV photoinduced phenomena in oxygen-deficient silica glasses A. Rybaltovskii. One- and two-quantum UV photo-reactions in pure and doped silica glasses. 2. Germanium oxygen deficient centers (GODC). V.N. Bagratashvili, et al. Photoinduced refractive index change and second harmonic generation in MCVD germanosilicate core fibers fabricated in reduced (nitrogen and helium) atmospheres E.M. Dianov, et al. Si/SiO2 Interface and Gate Dielectrics. Molecular hydrogen interaction kinetics of interfacial Si dangling bonds in thermal (111)Si/SiO2. An electron spin resonance saga A.L. Stesmans. Ultrathin oxide films for advanced gate dielectrics applications Current progress and future challenges E.P. Gusev. SiC/SiO2 interface defects V.V. Afanas'ev. Point defects in Si-SiO2 systems: current understanding S.P. Karna, et al. Index.

Ab initio cluster model calculations on the interaction of CO and CO2 with NiO and MgO surface and defect sites are reviewed. NiO behaves very similarly as the non-transition metal oxide MgO towards CO chemisorption because the bonding of CO to these surfaces is dominated by electrostatic terms and involves a very modest σ donation or, in the NiO case, π back donation. The role of the surface defects in determining the reactivity of oxides toward CO and CO2 chemisorption is shown.

The surface chemistry of metal oxides is of considerable importance in catalysis. A large fraction of industrial catalytic processes involves reactions occuring at the surface of transition metal oxides.1,2 For this reason, there is a need for the development of analytical surface techniques for the determination of the physico-chemical properties of the oxide surfaces. An important problem is the determination of the formal oxidation state of the surface cations. This can be indirectly deduced from measures of the Lewis’s acidity of the cationic surface sites. A variety of physico-chemical methods have been used to characterize the surface of an oxide: thermal desorption, microcalorimetry, Potentiometric titrations, spectroscopy. Usually, these techniques make use of a probe molecule adsorbed on the surface. The response of this adsorbed molecule to the experimental technique applied provides a measure of the chemical nature of the adsorption sites.