Formation of Triangular Arrays

Under the right concentrations, polymer colloids can self-assemble to form close-packed hexagonal films. Simple drop-casting methods enable the formation of large arrays of hexagonally packed particles, which provide a very simple but effective template through which to deposit materials to form patterns. The interstices between colloidal particles are small, approximately triangular holes. 

However, it must be borne in mind that in previous work, H2 did not react with a triangular array of O ions to form OH" ions (354). If such a reaction with H2 occurred, then the O" ions would no longer be available for Oj formation. Moreover, the reaction of pairs of O ions with oxygen should lead to pairs of O J ions which would have an abnormal EPR spectrum if they can be seen at all. In fact, the g tensor is as expected for isolated OJ ions. The CoO-MgO system behaves as CaO for the formation of Oj, i.e., via invisible O ions. The ozonide ions characterized by a three-g-value EPR signal (2.0025, 2.012, 2.017) do not exhibit any superhyperfine interaction with cobalt nuclei, suggesting that they are adsorbed on Mg2+ ions (110). Depending on the system (MgO, CaO, CoO-MgO) and the experimental conditions, the ozonide ion Oj disappears irreversibly between 25° and 130°C. In the case of MgO (333,334), OJ ions are formed when O J ions are destroyed, whereas for CaO (158) and CoO-MgO (110) the evidence is not clear. 

The Pd(Il) ions are four-coordinate and planar. An examination of this molecule reveals a triangular array of exposed mercaptido sulfur donors. It is conceivable that this molecule may serve as a donor for other metal ions with the formation of polynuclear complexes. 

Figure 19. Formation of localized dots numerical solutions of eq.(32) for [111] surface orientation showing different stages of coarsening of initial regular hexagonal array of triangular pyramids. The parameters are the same as in for the case shown in Fig.18, except 6 = 0.44Jm-2,...

In the case of electron-poor systems the electron deficit must be compensated by the formation of multiple bonds. Thus, the compound H20s3(CO)io that actually has only 46 electrons should have an Os-Os double bond leading to an isosceles triangular array of osmium atoms. Such a prediction agrees with structural data (Table 2.2) which show indeed one Os-Os distance of 2.60 A, shorter than the other two (2.8 A). 

Fig. 4 Pore density versus silicon electrode doping density for porous silicon layers of different geometries. Notice that macropores are essentially obtained on low to moderately doped substrates. The dashed line shows the pore density of a triangular pore pattern with a pore pitch equal to two times the SCR width for a 3 V applied bias. Note that only macropores on n-type substrates may show a pore spacing significantly exceeding this limit. The regime of stable macropore array formation on n-Si is indicated by a dot pattern. Doping type and etching current density (in mA/cm ) are indicated in the legend (After Lehmann 1993)...

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