Dimer reconstruction

Fig. 7. Si(001). Bulk terminated atom positions, top and side views. (2 x 1) dimer reconstruction, top and side views. In all cases, the first-layer atoms are hatched, the second-layer atoms are shaded and deeper-layer atoms are smaller. (Drawn by Tracy Schoolcraft.)...

Figure 5.3. Models of the Si(100) and Ge(100) surface (Left) (2 x 1) dimer reconstruction involving symmetric dimers (Middle) c(4 x 2) dimer reconstruction with buckled dimers These two structures are observed for silicon at room temperature and lower temperature, respectively. For germanium, the structure at (Right), the p(2 x 2) dimer reconstruction with buckled dimers, is also observed at lower temperatures. In the top view model, the open circles represent the top layer atoms, with the larger and smaller circles designating the up and down atoms of the dimer, respectively. The filled circles represent the next layer of atoms.

Although Si(100) and Ge(100) undergo similar dimer reconstructions, the Ge(l 11) surface reconstructions differ from those of Si(lll). As described above, Si(lll) reconstructs into a (7 x 7) structure that contains 49 surface atoms in the new unit cell. Ge(lll) is found in various reconstructed forms depending on surface preparation, but the most common reconstruction under vacuum is Ge(lll)-c(2 x 8) [51-53]. This structure involves charge transfer from adatoms to restatoms [5]. On the other hand, most of the passivation and functionalization studies reviewed here lead to the Ge(lll)-1 x 1 surface structure. This structure, in which the surface Ge atoms retain their bulk positions, can be achieved by hydrogen, chlorine, or alkyl termination of the surface (discussed below). The structure is analogous to that for H-terminated Si(lll). 

Dimensionless coupling constant, 397fr, 405f pr Dimerization reconstruction, Schlier and Farnsworth, 240... 

Approximate first-order kinetics has been observed on the Ge(100)-2 x 1 surface, which also has a surface dimer reconstruction [44, 55]. D Evelyn et al. [44] showed that the prepairing model reproduces deviations from first-order behavior on Ge, again with an of about 5 kcal/mol. This preliminary evidence hints at wider generality for the prepairing model. Several groups have found indications of first-order kinetics on the diamond (100)-2 X 1 surface [56-58] as well, though the kinetic parameters are not well determined. 

Fig. 8.28. Plots of surface energy density versus biaxial mismatch strain for (105) vicinal surfaces with steps aligned with the [010] direction on (001) Si. The stepped edges are serrated in both cases by removing every other step-edge atom, which leaves two possibilities for dimer reconstruction on the terraces. In the configuration proposed by Khor and Das Sarma (1997), the dimer nearest the step edge rebonds directly into the step face, whereas the configuration proposed by Mo et al. (1990) presumes the alternate dimer reconstruction. The plot is based on compntations by Shenoy et al. (2002) using the Tersoff potential.

Table 4.6 Structural parameters as defined in Figure 4.32F determined for the (2 x 1) reconstructions ofSi(lOO) and Ce(lOO). For Si(lOO), an early analysis with a symmetric dimer model [75] and the latest analysis with a buckled dimer model [83] are listed. For Ge(lOO), the model listed also has a buckled dimer reconstruction [87].

Figure 9.39 A vicinal Si(OOl) surface with alternating Sa and Sb steps that separate terraces with alternating (2x1) and (1 x2) dimer reconstructions. Sa steps are straight Sb steps are rough and exhibit a large number of thermally excited kinks.

It turns out that dimer reconstructions also explain the c(4x2) and p(2x2) phases of Si(OOl). These reconstructions with larger... 

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