Ordered islands

Tarek et al. [388] studied a system with some similarities to the work of Bocker et al. described earlier—a monolayer of n-tetradecyltrimethylammonium bromide. They also used explicit representations of the water molecules in a slab orientation, with the mono-layer on either side, in a molecular dynamics simulation. Their goal was to model more disordered, liquid states, so they chose two larger molecular areas, 0.45 and 0.67 nm molecule Density profiles normal to the interface were calculated and compared to neutron reflectivity data, with good agreement reported. The hydrocarbon chains were seen as highly disordered, and the diffusion was seen at both areas, with a factor of about 2.5 increase from the smaller molecular area to the larger area. They report no evidence of a tendency for the chains to aggregate into ordered islands, so perhaps this work can be seen as a realistic computer simulation depiction of a monolayer in an LE state. 

Chambliss, D. D., Wilson, R. J., and Chiang, S. (1991b). Nucleation of ordered island arrays on Au(lll) by surface-lattice dislocations. Phys. Rev. Lett. 66, 1721-1724. 

Fig. 13. STM images of organic molecules on the Si(100)-2 X 1 H surface (a) 35 nm2 image showing self-ordering of styrene molecules [79], (b) 35 nm2 image of ordered islands of C60 molecules [82], and (c) 25 nm2 3D rendered image of a carbon nanotube [80].

Another problem which obscures the analogy between different phase transitions is the fact that one does not always wish to work with the corresponding statistical ensembles. Consider, for example, a first-order transition where from a disordered lattice gas islands of ordered c(2x2) structure form. If we consider a physisorbed layer in full thermal equilibrium with the surrounding gas, then the chemical potential of the gas and the temperature would be the independent control variables. In equilibrium, of course, the chemical potential jx of subsystems is the same, and so the chemical potential of the lattice gas and that of the ordered islands would be the same, while the surface density (or coverage 9) in the islands will differ from that of the lattice gas. The three-dimensional gas acts as a reservoir which supplies adsorbate atoms to maintain the equilibrium value of the coverage in the ordered islands when one cools the adsorbed layer through the order-disorder transition. However, one often considers such a transition at... 

Of course, the two processes considered schematically in fig. 39 are only the basic building blocks of much more complex processes that are expected to occur in real systems, Consider e.g. the phase diagram of fig. 28c If we quench the system from the disordered phase to low temperatures for 9 < 1/2, the system separates into a disordered low-density lattice gas and ordered islands exhibiting the c(2x2) structure and 6 1/2 similarly, for the system of fig. 28d quenching experiments would produce simultaneously phase separation and ordering in (V3x /3) structures. Here we do not aim at a detailed description of such processes, but rather sketch the main ideas... 

To inject a comparable amount of charges in the ordered islands, a higher voltage is reqnired during the injection process The injected holes are not delocalized after the injection (Figure 4.3.15c). 

FIGURE 16.4 STM images of a 6 ML nanocrystal of Cso molecules subjected to an electron pulse irradiation (30 V and 60 nC) (a) 5 min and (b) 16 min after the irradiation. Mobile Cgo agglomerates form an ordered island in the irradiated region. (From Bolotov, L. and Kanayama, T., Low-energy electron irradiation of fullerene films formed on Si(lll)-(7x7) surfaces, Appl. Phys. Lett., 81, 1684-1686, Copyright 2002, with permission from American Institute of Physics.)... 

Figure 4.37 Sketch of the mechanism generating stripes of Au55(PPh3)i2Cl6 chains by the division of ordered islands into sections caused by the oscillating meniscus at the water-substrate boundary.

An example of chiral recognition and amplification by molecular adsorbates was reported by Chen and Richardson who showed that adenine dimers form homochiral chains on Cu(l 10 [99]. Chains of one chirality are capable of recognizing one enantiomer of phenylglycine, while the opposite enantiomer is recognized by chains of the opposite chirality [99]. The recognition process is able to nucleate subsequent growth of ordered islands of enantiomerically pure phenylglycine [99]. 

F. 71 Molecular structures of BPCPPCA onto calcite(10.4). (a) As-deposited, ordered island with a (2 X 4) superstructure (inset), (b) Overview image after annealing the substrate to about 300°C for 1 h, revealing rows (labeled I and IT) with two distinct angles with respect to the [01.0] directioiL (c) Proposed model for the two row types on calcite(10.4)... 

When depositing a submonolayer of BPCPPCA onto the calcite(10.4) surface at room temperature, ordered islands of a (2 x 4) superstructure are formed, as shown in Fig. 71a. 

To induce the second reaction step, we annealed the surface to 340°C. The resulting stmctures are shown in Fig. 72. Most strikingly, the molecular structures that are present on the surface after the second annealing steps are, again, distinctly different from both the as-deposited ordered islands and the row structures observed after the first, moderate annealing step. 

Truong, KT>., Rowntree, PA. Formation of self-assembled butanethiol monolayers of Au substrate spectroscopic evid ce for highly ordered island formation in sub-monolayer films. J. Phys. Chem. 100, 19917-19926 (1996)... 

In situ STM image of the partially ordered 2D surfece oxide layer formed on Ag(lll) in 0.1 M NaOH at -0.05 V. D and I mark the highly defective matrix and extended ordered islands, respectively. Circles indicate the atomic lattice. (From Maurice, V. et al., /. Phys. Chem. C, 111, 16351,2007.)... 

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