Defects on the surface

The rate of the droplet motion was limited by the rate of the viscous flow of the liquid because electrochemical reaction took place much faster (in less than 1 s) than the deformation of the droplet ( 10 s). Pinning of the droplet sometimes occurred at a defect on the surface. In most cases, the pinned droplet could be moved again by... 

As already mentioned, the poison formation reaction is potential-dependent, and the poisoning rate for the basal planes is Pt(llO) > Pt(lOO) > Pt(lll) [Sun et al., 1994 Iwasita et al., 1996]. The case of Pt(lll) is special, since the poisoning has been associated with the presence of defects on the surface. Selective covering of the defects on the Pt(l 11) electrode by some adatoms prevents the formation of CO on the electrode surface [Macia et al., 1999, 2001 Smith et al., 2000]. 

The degree of graphitization also plays a significant role on the corrosion rate of MWCNTs the number of defects on the surface of nanotubes decreases as graphi-... 

In the case of a quasi-isolated surface, the bulk of the semiconductor (e.g., impurities inside the crystal) no longer influences its chemisorptive and catalytic properties, the latter depending only on the structure of the surface. This dependence is implicit in Equation (25), according to which the position of the Fermi level on the surface e.+ (and hence the chemisorptive and catalytic properties of the surface) depends on the concentration and nature of the chemisorbed particles and also on the concentration and nature of the structural defects on the surface. 

The herringbone structures are particularly sensitive to local defects on the surface. Near a single atomic step, the herringbone structure is often terminated by U-shaped connections. 

This visual inspection should be done before the tank is hydraulically tested since rusting formed immediately after the hydraulic test will camouflage the defects on the surface. 

In JP-A-2213174 cross-talk between adjacent photodiodes is reduced by providing a lattice of crystal defects on the surface of a CdTe substrate before an HgCdTe detector layer is grown thereon. 

Generally any deviation from a perfect surface is considered a defect and can originate from several sources, those that occur naturally on the clean surface or from contaminants. It is useful to understand the most common types of defect on the surface in order to interpret STM images of deposited adsorbates. It is also important to minimize these surface defects, especially from the perspective of nanoscale device construction on Si [17,18] where defects could alter device performance. A surface, prepared using standard annealing techniques in UHV, will typically contain a defect density of a few percent. 

For the surface defect mechanism, using a HF derived kinetic Monte Carlo model, Radeke and Carter98 showed that H2 desorption from Si(100)-2 x 1 via isolated dihydrides (Figure 11c) follows first-order kinetics. They further showed that the concentration of defects on the surface has a profound effect on the desorption rate constant. Recent studies proposed the importance of step sites rather than terraces99. 

In addition to the adsorption reaction it is admitted that the defects A can undergo reactions involving other defects on the surface. These reactions among the defects may be either monomolecular, bimolecular, or more complex. Examples of the first two cases have been discussed in detail by Vol kenshtein. In the monomolecular case it is assumed that in addition to the defects A and B a third type of defect C exists which undergoes the following reaction... 

In principle, the optical absorptions in this region could also be associated with point defects on the surface either with or without trapped electrons and holes. However, the properties of the charged defects have been studied extensively, and the trapped charges can be thermally annealed at temperatures far lower than the normal preparation temperatures of these samples. In addition, they are characterized by optical and EPR spectra which are not observed in these samples. Contributions from point defects with no trapped charges cannot easily be eliminated. In fact, such a surface vacancy or divacancy would represent a localized state on a low-index surface associated with 4-coordinated ions. 

The transport of protons from HTD surface on Ca(OH)2 surface is accompanied by redistribution of electron densities on neighboring calcium and titanium atoms [50]. According to XPS (Fig. 6.12), the binding energy of the Ti 2p3/2 level in the initial HTD is weakly sensitive to the presence of OH" groups and H2O it is quite the same for HTD and anhydrous anatase [51]. In the activated HTD, the position of the maximum ofTi 2p3/2 line is not changed but broadening of the line occurs that is connected with the formation of defects on the surface. However, in the spectrum of activated... 

It has been demonstrated in earlier sections that the catalytic activity of nickel oxide in the room-temperature oxidation of carbon monoxide is related to the number and the nature of the lattice defects on the surface of the catalyst and that any modification of the surface structure influences the activity of the solid. Changes of catalytic activity resulting from the incorporation of altervalent ions in the lattice of nickel oxide may, therefore, be associated not only with the electronic structure of the semiconductor (principle of controlled valency ) (78) but perhaps also with the presence of impurities in the oxide surface or a modification of the surface structure because of this incorporation. In order to determine the influence of dopants on the lattice defects in the surface of the solid and on its catalytic activity, doped nickel oxides were prepared under vacuum at a low temperature (250°). Bulk doping is not achieved and, thence, one of the basic assumptions of the electronic theory of catalysis (79) is not fulfilled. 

The strained two-member silicon rings, which are the most peculiar topological defects on the surface of amorphous silica, proved the most reactive [55]. Thus, hydratation occurs preferentially with these rings - they are cleaved through the processes shown schematically in Fig. 5.18. This is in agreement with the most abundant spectroscopic evidence collected in real hydratation and dehydratation experiments and reported in literature. 

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