Rough surfaces restructuring

Defect sites (steps or kinks) and rough, low-packing-density surfaces have higher charge densities near the Fermi level. This is shown by lower work functions and the higher densities of filled electronic states detected by photoemission studies. These rough surfaces restructure more readily when clean, as described in Chapter 2. They are likely to participate in more massive adsorbate-induced restructuring... 

The use of neutron reflectivity at liquid interfaces, which is a method sensitive to both surface roughness and surfactant layer thickness, was reviewed with the examples of polydimethylsiloxane-surfactant layers.633 Sum-frequency generation (SFG) vibrational spectroscopy was applied to study surface restructuring behavior of PDMS in water in an attempt to understand antifouling properties of silicones.6 ... 

Rough surfaces that are also chemically active (as will be discussed later) appear to be flexible. The uncovered surface atoms move toward the bulk and to new equilibrium positions. The more open the surface, the larger the movement and the more flexible the surface atoms are. Upon chemisorption these surfaces restructure more readily. It is perhaps instruetive to divide surfaces according to their flexibility as shown in Figure 6.12. Close-paeked surfaces, like the face-centered cubic (fee) (111)... 

The adsorbate bond is surface-structure-sensitive, and adsorbate-induced surface restructuring frequently occurs. Rough surfaces (with lower atomic coordination) restructure more readily. 

Silver catalysts have been used for the partial oxidation of methanol to formaldehyde this is a very important process in the chemical industry. The role of the silver catalyst and, in particular, the influence of its atomic structure on the catalytic process have been extensively studied with various surface science tools [44—50]. In these investigations, Raman spectroscopy was employed to identify and confirm the role of the oxygen species for the catalytic process. These studies were performed under reaction conditions close to those in industrial processes using Ag(lll) and Ag(llO) samples. Upon extended exposure to oxygen at high temperatures, both samples restructure to (111) planes with a well-defined microstructure and with mesoscopic roughness (on a scale of 1 pm). Therefore, in the course of the oxygen pretreatment, the local nature of the surface of the two samples becomes nearly identical and, hence, their Raman spectra are quite similar [44]. 

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