Oxides bonding

Aluminum, the most common material used for contacts, is easy to use, has low resistivity, and reduces surface Si02 to form interfacial metal-oxide bonds that promote adhesion to the substrate. However, as designs reach submicrometer dimensions, aluminum, Al, has been found to be a poor choice for metallization of contacts and via holes. Al has relatively poor step coverage, which is nonuniform layer thickness when deposited over right-angled geometric features. This leads to keyhole void formation when spaces between features are smaller than 0.7 p.m. New collimated sputtering techniques can extend the lower limit of Al use to 0.5-p.m appHcations. 

EtO)2P(S)] with short oxide bonds and phosphate oxygen weakly bridging to the second tin. This relates to the carboxylate structure of (26b) where the additional bridges are weaker. 

Disulfide bonds arise when the SH groups of two cysteine residues are covalently linked as a dithiol by oxidation. Bonds of this type are only found (with a few exceptions) in extracellular proteins, because in the interior of the cell glutathione (see p.284) and other reducing compounds are present in such high concentrations that disulfides would be reduc-... 

Figure 1 Crystal structure of 2,5-dihydro-2,4- Figure 2 Crystal structure of 2,4-diphenyi-2/7-diphenyl-l,2,3,5-thiatriazole 1-oxide (bond lengths in 1,2,3,5-thiatriazol-l-ium bromide (bond lengths in A A and bond angles in °). and bond angles in °).

In oxides a large departure from the stoichiometric composition is usually met. The importance of this phenomenon, also for the understanding of the oxide bond, is highlighted at the end of the chapter. 

Here, the main features of the valence band results for Th02 and UO2 will be illustrated. Since a large number of publications exists in this field (especially for uranium oxides), reference will be made only to a few selected investigations, chosen for the purpose of highlighting those aspects of the oxide bond discussed previously. A very comprehensive review of these results can be found (and references therein electronic and spectroscopic properties in Refs. 109-111). Figure 21 shows the photoemission spectrum of Th02 and UO2 up to Et = 45 eV The valence band region extends to about 10 eV. The marked difference is the appearance in UO2 of a sharp and intense peak at Et =... 

Which Metal Oxide Bonds Are Critical for Oxidation Reactions V=0, V-O-V or V-O-Support ... 

Toluene p-sulfonyl hydrazones (tosyl hydrazones) undergo C=N oxidative bond cleavage with H202 in the presence of TS-1, to give high yields of the corresponding carbonyl compounds very likely, the reaction proceeds through... 

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