Vacancy island

Figure 10.11 A well-ordered 2D AuS phase develops during annealing to 450 K. (A) The structure exhibits a very complex LEED pattern, which can be explained by an incommensurate structure with a nearly quadratic unit cell. (B) STM reveals the formation of large vacancy islands by Oswald ripening which cover about 50% of the surface, thus indicating the incorporation of 0.5 ML of Au atoms into the 2D AuS phase. The 2D AuS phase exhibits a quasi-rectangular structure (inset) and uniformly covers both vacancy islands and terrace areas. (Reproduced from Ref. 37).

Thiophene monolayers can be removed by UV photolysis in air followed by rinsing with ethanol. When unannealed SAMs are photooxi-dized, the vacancy islands in the thiophene monolayers disappear. The oxidation product in this case is presumably 1,1-thiophene dioxide. 

Figure 9 shows an STM image recorded after adsorbing 0.1 ML of sulphur on 0.8 ML of silver supported on Ru(OOOl) [44]. Initially, a mismatch between the lattice parameters of silver and ruthenium produced misfit dislocations in the structure of the metal overlayer (not shown) [24,44]. The sulphur adatoms attack preferentially these positions. Ag atoms are displaced from the Ru interface and their positions are occupied by sulphur atoms. Within the structure of the metal overlayer a highly ordered triangular lattice of silver vacancy islands forms (Figures... 

Fig 10 Atomically resolved STM image (115x115 A) of a large silver vacancy island, about 50 A in diameter. The island step edges of this and the smaller islands move much faster than the acquisition rate of the STM images, and thus appear blurred . The cluster of nearly 50 sulphur adatoms inside the large island exhibits p(2x2) order. Reprinted from ref. [44]. 

All vacancy island formation during Sb electrodeposition. Although, attempts to deposit atomic layers of Co onto naked Au surfaces at underpotential were not successful, stable Co upd layers can be formed on the Sb/Au surface. The chemical nature of the CoSb phase formed is under investigation, and will be reported on in the near future. 

Standing electron wave patterns of surface states also can be observed in defects. This was realized with adatom islands on Ag( 111) at low temperature [205]. Vacancy islands did not show electron confinement probably because of absorption losses via bulk transitions. 

FIGURE 3.1 Different initial configuratioiis for processes on an fccflOO) surface, (a) A typical stepped surface used in the simulations with A =64 and Ny = Sl. (b) A typical island used in the simulations with JVi=J = 105. (c) A typical iimer island in a vacancy island on a fccflOO) surface used in the simulations with A =J = 105. Reproduced with permission from Potting et aL [10] and Luque et al. [14]. 2009, 2010, Elsevier. 

As pointed in Section 3.3.1, the weU-defined geometry of an island, which initiaUy contained 218 atoms, situated in the center of a vacancy island of75 x 75 atoms (Fig. 3.1c) was the initial configuration for the study of Ostwald ripening. In the absence of adsorbed Cl, the island was practically stable over the time of 1000 s (soUd line, in Fig. 3.7). In the presence of chlorine, the island decayed completely with a decay rate of about 0.25 atoms s (dashed line in Fig. 3.7). 

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