Average island diameter

Islands occur particularly with adsorbates that aggregate into two-dimensional assemblies on a substrate, leaving bare substrate patches exposed between these islands. Diffraction spots, especially fractional-order spots if the adsorbate fonns a superlattice within these islands, acquire a width that depends inversely on tire average island diameter. If the islands are systematically anisotropic in size, with a long dimension primarily in one surface direction, the diffraction spots are also anisotropic, with a small width in that direction. Knowing the island size and shape gives valuable infonnation regarding the mechanisms of phase transitions, which in turn pemiit one to leam about the adsorbate-adsorbate interactions. 

Stearic Acid-czs-Decalin Series. The adsorption process of stearic acid from Decalin (Figure 3) is similar to that of the first two acids, with the trend being to still smaller average island diameters for the several stages of monolayer completion. 

Fig. 72. The average island diameter (i) and die rms roughness (ii) of two typical Y films grown at T ubs — (D)...

In order to develop the criterion more quantitatively, consider the sequence of phase-space portraits shown in Figs. 5.4(a) - (d). This sequence suggests that, as the control parameter K increases, the diameter of the resonance islands at Z = 0 mod 27t grows in action. In order to predict the touching point of the resonances, we need the widths of the resonances as a function of K. The width of the resonances is derived on the basis of the Hamiltonian (5.2.1). Since the dynamics induced by H is equivalent to the chaotic mapping (5.1.6), the Hamiltonian H itself cannot be treated analytically and has to be simplified. One way is to consider only the average effect of the periodic 6 kicks in (5.2.1). The average perturbation... 

To prepare model catalysts, metal nanoparticles were grown on the thin film oxide by evaporation (step 3 in Fig. 15.7a). Figure 15.7c and d show STM results for Pd nanoparticles grown on Al3O3/NiAl(110) at 300 and 90 K, respectively [11, 39,43,47,48]. Figure 15.8 displays the dependence of the island density (nanoparticles per cm ), the mean particle diameter, and the average number of atoms per particle on the nominal film thickness [39]. Similar nucleation studies were performed for Pt, Rh, and Ir nanoparticles [39, 46]. 

Fig. 15.8 Deposition of Pd on Al203/NiAl(l 10) at 300 and 90 K substrate temperature dependence of the island density, mean particle diameter, and average number of atoms per particle on the nominal film thickness. Adapted from [39] with permission. Copyright 1999 Elsevier...

As more Si or Ge is deposited, the average crystallite size increases. But the crystallites remain (truncated) spherical until their size reaches a threshold value. Here, facets become observable when the crystallites grow to a diameter of 40 5 nm. This size threshold of faceting is comparable to that of Ge on HOPG. In Figure 6.12b, after 50-nm Ge deposited, relatively large islands show facets on... 

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