Modulated vicinal surfaces

Figure 1. Sets of constant height contours on 1- and 2-D sinusoidal surfaces. The contours correspond to the idealized shapes of the surface steps on modulated crystal surfaces, a) and c) correspond to modulations on singular planes b) and d) correspond to vicinal surfaces.

D Gratings on Si(OOl) There are some fundamental differences in the evolution of 1- and 2-D modulations on singular or vicinal surfaces. As illustrated in figure 1 and discussed by Rettori and Villain[4] the 2-D modulations will generally involve closed step contours so that decay is promoted by differences in curvature of neighbouring steps and also interactions among steps in... 

Membrane alanyl aminopeptidase (microsomal aminopeptidase, amino-peptidase M, EC 3.4.11.2) and peptidyl-dipeptidase A (angiotensin I converting enzyme, EC 3.4.15.1) located in the vascular endothelium and smooth muscle cell surface modulate the levels of vasoactive peptides [23], One of the roles of membrane-bound enzymes is to switch off the action of peptides in the vicinity of the target or to prevent them from gaining access to a region containing receptors that are activated only by locally released peptides. 

Schottky barrier height modulation and stabilization as a "by product" of the original studies. Moreover, since these results are thought to follow from replacement reactions in the vicinity of the interface, they reflect the importance of surface structure as well as composition at semiconductor interfaces. 

The most inclnsive definition of hydration shell describes it as consisting of all thermodynamically altered water molecnles in the vicinity of a solnte. From a thermodynamic standpoint, hydration can be viewed as binding of water molecnles to the hydration sites of a solnte. The energetics of this association is modulated by the type of solute-solvent interactions (electrostatic, hydrogen bonding, van der Waals) and by solnte-indnced solvent reorganization. The latter occnrs even in the absence of appreciable solute-solvent interactions becanse the eqnUib-rium distribution of hydrogen-bonded water networks of the bulk becomes disrupted at the solute surface. 

When the modulation of the gas solid potential is strong enough, the positions of adsorbed particles are confined to a close vicinity of the surface potential minima (adsorption sites) even at quite high temperatures. Under such conditions the ordered cidsorbed phases are commensurate with the substrate surface lattice. These ordered phases may undergo various phase transitions when the density of the film or the temperature changes. 

We now turn our attention very briefly to the nematic liquid crystal surface. A variety of experimental studies have established conclusively that orientationally ordered states, and in certain materials even density modulations, develop in the vicinity of the free surface. We describe below the salient features of these observations. 

---