Surface atomically smooth

Large Specific Surface Area Porous materials can have a large proportion of surface atoms - their surface area within a typical sampling volume of 10 pm can reach 10 pm, which is approximately 10 larger than for a smooth surface crossing the same volume. These effects lead to clearly increased Raman intensities of surface species and also to improved intensity ratios of surface and bulk Raman bands. 

Hollow carbon nanostructures are exciting new systems for research and for the design of potential nano-electronic devices. Their atomic structures are closely related to their outer shapes and are described by hex-agonal/pentagonal network configttrations. The surfaces of such structures are atomically smooth and perfect. The most prominent of these objects are ftil-lerenes and nanotubesjl]. Other such novel structures are carbon onions[2] and nanocones[3]. 

The statics and dynamics of microstructures are governed by the forces that create or maintain them. Rarely can the forces be measured directly. But forces between special surfaces immersed in fluid can now be accurately gauged at separations down to 0.1 nm with the direct force measurement apparatus, an ingenious combination of a differential spring, a piezoelectric crystal, an interferometer, and crossed cyhndrical surfaces covered by atomically smooth layers of cleaved mica (Figure 9.4). This recent development is finding more and more applications in research on liquid and semiliquid microstructures, thin films, and adsorbed layers. 

Sample surfaces are atomically smooth surfaces of cleaved mica sheets for SFA, and various colloidal spheres and plates for a colloidal probe AFM. These surfaces can be modified using various chemical modification techniques, such as Langmuir-Blodged (LB) deposition [12,19] and silanization reactions [20,21]. For more detailed information, see the original papers and references texts. 

At smooth metal electrodes that have been subjected to annealing, the number of different crystallographic defects (dislocations, kinks, etc.) emerging at the surface is between 10 and lO cm. This number is small relative to the total number of surface atoms (which is on the order of 10 cm ). In the literature, attempts have been described to determine the catalytic activity of electrodes having an artihcially boosted number of surface defects. These experiments gave no unambiguous results in some cases some increase, in other cases some decrease in activity was observed. 

The forces acting between atomically smooth mica surfaces immersed in both organic and aqueous liquid media have been determined in the range of surface separations 0 - 300 nm, both in the absence and the presence of adsorbed polymer layers. In this way the interactions between the adsorbed macromolecular layers themselves were determined. We present results for the following cases i) Poor solvent, ii) 0 - solvent, iii) good... 

Figure 21 Friction coefficient for differently oriented Ni(100)/Ni(100) interfaces. Rough surfaces have a 0.8 A rms variation in roughness added to the atomically smooth surfaces. Reproduced with permission from Ref. 85.

The concentration of the surface states is in the range from 1 x 10 to 1 x 10 cm-, which is 1/10 to 1 /lOOOOO of the concentration of surface atoms ( 1 x 10 cm- ). UsuaUy, the surface state concentration is greater on the rough siuface than on the smooth surface. 

Ideal Surfaces, A model of an ideal atomically smooth (100) surface of a face-centered cubic (fee) lattice is shown in Figure 3.13. If the surface differs only slightly in orientation from one that is atomically smooth, it will consist of flat portions called terraces and atomic steps or ledges. Such a surface is called vicinal. The steps on a vicinal surface can be completely straight (Fig. 3.13a) or they may have kinks (Fig. 3.13b). 

The structure of real surfaces differs from the structure of ideal surfaces by the surface roughness. Whereas an ideal surface is atomically smooth, a real surface has defects, steps, kinks, vacancies, and clusters of adatoms (Fig. 3.16). 

As an attempt to quantify the effect of solvent on individual faces of sucrose crystal we have ertqrloyed a solvent accessibility of Van der Waals sized surface atoms for a spheric probe representing the solvent molecule flSI. The smooth surface generated by rolling such a probe along the crystal surface consists of... 

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