Two-layer structure

Figure 11-18. Calculated current (solid line) and iccuinbiiuuion current (dashed line) density as a function of voltage bias for a single-layer structure, a two-layer structure with a hole-blocking layer and a two-layer structure in which the hole-blocking layer also serves as an electron transport layer.

E. Makovicky and B. G. Hyde, Incommensurate, Two-Layer Structures with Complex Crystal Chemistry Minerals and Related Synthetics, Mat. Sci. Forum, 100 101, 1-100 (1992). 

An alternative two-layer structure is adopted by a hexagonal form of NbS2 (NbS2 hex), with the sequence. .. Ay A ByB. ... 

Most of the metal-rich proteins form approximately cylindrical two-layer structures with either an up and down (rubredoxin, cytochrome c) or a Greek key (ferredoxin) topology, but in which the elements forming the cylinder are a mixture of helices, /3 strands, and more or less extended portions of the backbone. Cytochrome c3 is perhaps the ultimate example of an S-M protein, with four hemes in just over a hundred residues, and essentially no secondary structure at all except for one helix. 

Deposition of a merocyanine-dye layer on a transparent electro-conducting film of polyester coated with indium-tin oxide (ITO). Two layered structures were studied ... 

Figure 8. (a) Structure of the two-layer structure found in xerogel, and (b) comparison of the electrochemical behavior of the crystalline, xerogel,ct>-phase, and aerogeh forms of vanadium pentoxide. 

Blown film is made similarly to blow-molded articles the molten resin is extruded continuously as a parison, which is blown to form a continuous film cylinder. This cylinder can be rolled up as a two-layer structure or slit to form one large or two smaller single layers. 

Lister, J.S. and Bailey, S.W., 1967. Chlorite polytypism, 4. Regular two-layer structures. Am. Mineralogist, 52 1614-1631. 

The current understanding of the structure of ZDDP-based tribofilms derives mainly from XANES spectroscopy (Armstrong et al., 1997 Bancroft et al., 1997 Ferrari et al., 1999a Fuller et al., 1995, 1998 and 2002 Martin et al., 2001 Yin et al., 1993 and 1997a), infrared spectroscopy (Harrison and Brown, 1991 Lindsay et al., 1993 Willermet et al., 1992 and 1995b), and a comprehensive multi-technique (AES/XPS/XANES) approached on the basis of the hard and soft acids and bases (HSAB) principle (Martin, 1999, Martin et al., 2001 ). Most prominent models involve a two-layer structure. The layer in contact with the metal surface is thought to be composed of short-chain polyphosphates, and a top layer, consists of long-chain zinc polyphosphate. 

A Cameron-Plint friction machine generated tribofilms with two-layer structure a zinc polyphosphate thermal film overlying a mixed short-chain phosphate glass, containing iron sulfide precipitates. A tribochemical reaction between the zinc polyphosphate and the iron oxides species is proposed on the basis of the hard and soft acid and base HSAB principle (Martin, 1999 Martin et al., 2001). 

A recent XANES experiment showed that the ZDDP tribofilm generally has a two-layer structure a short-chain phosphate layer covered by a thin, long-chain polyphosphate layer. XANES spectra analysis of tribofilms did not show a substantial difference between neutral and basic ZDDPs (Fuller et al., 1997 Martin, 1999 Martin at al., 2001 Varlot et al., 2000 Willermet et al., 1991 and 1992 Yamaguchi et al., 1993 and 1996). 

Different from the situation of the passive layer on Ni, passive Cr does not show a two-layered structure. Variation of the tunnel current does not cause the change from an amorphous to a crystalline structure [127], Depending on the potential one observes the amorphous granular structure of the hydroxide, or the crystalline oxide. The lattice parameter measured by STM is 0.28 nm, which corresponds to the distance in the O plane of 0001-oriented a-Cr203. Apparently, STM samples the distance of the O ions. The distance of Cr3+ ions should be 0.485 nm due to a lower density of the cations. Crystalline bulk CrO(OH) and Cr(OH)3 have a similar structure. The parameters of the hydroxide or oxyhydroxide are somewhat larger, i.e. 

The particularity of the natural conditions of the Black Sea lies in the fact that it the largest basin in the world with a permanent halocline and a two-layered structure of the waters. The intensive pycno- and halocline prevents the waters from vertical mixing and oxygen penetration to deeper layers even in the period of the development of the wintertime vertical convection. Therefore, the entire water column below a depth of 100-200 m represents an inanimate hydrogen sulphide zone, in which only anoxic processes take place. About 90% of the water volume does not participate in the processes of self-purification of the sea. 

The two-layered structure of the Uzunlarian deposits is also registered on the Caucasian coast. Here, they form a coarse-grained terrigenous (conglomerates and calcareous sands) accumulative cover of the fifth (55 m high) terrace. 

One can visualize this situation by considering six pseudocells as constituents of two- and three-layer tobermorite sheets. The number of Si02 molecules in the six pseudocells is 12, and the two-layer structure has, let us say, 17 CaO molecules in the six cells. The CaO/Si02 ratio is 1.42. The six cells in the two-layer sheet contribute six unit areas, in the three-layer sheet four unit areas. Thus, in the conversion from the two- to the three-layer sheet, two pseudocell areas disappear. The cementing action requires four CaO molecules consequently, the six cells in the three-layer sheet have 21 CaO and 12 Si02 molecules, and the CaO/Si02 ratio becomes 1.75. 

The Taylor-Howison hypothesis gives an almost identical structure for the three-layer tobermorite with the one shown in Figure 8 the pseudocell surface contains one molecule of Si02 and 0.75 molecule of CaO, and the CaO content of the layers between the pseudocells is 1.50 molecules. The two-layer structure, however, shows greater differences. The surface is not very different it contains... 

The change in dB provides additional information about the refractive index of the thin films that have three- or two-layer structures [8]. 

Layer thicknesses are similar to those of the AFm phases, and it would be difficult to distinguish the two groups of phases by XRD if only the basal reflections could be observed. Polytypism is common for example, sjogrenite, with a two-layer structure, has a three-layer polytype, called pyroaurite. Three-layer structures are the ones normally formed at room temperature. Meixnerite, which is a three-layer form, has a = 0.30463 nm, c = 2.293 (3 X 0.764)nm, space group R3m, Z = 3, D = 1950kgm (K30). Thermal dehydration (B86) and IR spectroscopic (FI35) studies on Mg-Al phases of this group have been reported. 

Two-layer structure forms on front-illuminated n-Si and on high-resistivity p-Si the top layer has microscopic pores (nanometer scale) while the bottom layer has macroscopic pores (micrometer scale). 

Hakkinen et al. examined two isomers of Au8 bound on an F-center of MgO(lOO),167 a quasi-planar structure and a two-layered structure that is similar to the structure of neutral gas phase Aug. After 02 adsorption, the quasi-planar structure is the more stable of the two by 0.10 eV. Based on the concept that clusters of both types must exist in real materials, the bonding of 02 was primarily examined with respect to the slightly less stable two-layered structure. 02 adsorbed on this cluster is accompanied by an extension of the O O bond length by 0.18 A compared to gaseous 02 and the adsorbed molecule has zero net spin, unlike the gas phase triplet state. The adsorption of 02 on this... 

Surface induced spinodal decomposition leads, for properly controlled surface fields, to a two layer structure characteristic for coexisting phases. Hence it may be used to determine the coexisting conditions in a more convenient way that with the interfacial relaxation method as the initial bilayer geometry may be avoided. In practical terms the overall composition of the whole thin film may be much better controlled in experiments involving spinodal decomposition. Therefore in experiments studying the equilibrium composition vs depth pro-... 

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