Row structures

Surface reconstructions have been observed by STM in many systems, and the teclmique has, indeed, been used to confmn the missing row structure in the 1 x 2 reconstruction of Au(l 10) [28]. As the temperature was increased within 10 K of the transition to the disordered 1 1 phase (700 K), a drastic reduction in domain size to -20-40 A (i.e. less than the coherence width of LEED) was observed. In this way, the STM has been used to help explain and extend many observations previously made by diffraction methods. 

The first STM evidence for the facile transport of metal atoms during chemisorption was for oxygen chemisorption at a Cu(110) surface at room temperature 10 the conventional Langmuir model is that the surface substrate atoms are immobile. The reconstruction involved the removal of copper atoms from steps [eqn (1)], resulting in an added row structure and the development of a (2 x 1)0 overlayer [eqn (2)]. The steps present at the Cu(llO) surface are... 

A series of LEED intensity studies, together with ion-scattering spectroscopy, established that a missing row structure was the correct model for the (1 x 2) phase,14 with some small subsurface relaxation and reconstruction.10... 

Atom resolved studies were first reported by Ertl s group15 in the early 1990s for Cu(110)-K, indicating the development of (1 x 3) and (1 x 2) structures depending on the surface coverage. They were missing row structures with... 

Initial adsorption of potassium (0.15-0.25 ML) at room temperature does not change the (1 x 2) missing row structure of the Au(110) surface. The adsorbed... 

A sequence of STM images were obtained (Figure 7.2) of the Cu(l 10) surface before hydrogen exposure (A), at an ambient H2 pressure of 1 bar (B) and finally after evacuation under UHV conditions (C). It is clear that in the presence of H2 the surface reconstructs into the well-known (1x2) missing row structure and that an evacuation the surface reconstruction is lifted with the (2 x 1) structure observed. AES established that no impurities were present at the Cu(110) surface. 

Figure 4.9. Constant current images (10.5 x 6.9 nm ) at 41 K. (A) HtBDC double row structure (Vt = 1.070 V, k = 0.45 nA). The trenches in the underlying surface are sketched. (B) The trenches in the surface layers are disclosed after manipulating the molecules aside (Vt = 1 mV, k = 1-82 nA). Atomic resolution along the close-packed direction was obtained in the left part of the image (vertical fast scanning direction), whereas it was lost when the tip scanned the restructured area. (C) Ball model of the double row structure. The substrate atoms are shaded darker the deeper the layers lie, while the molecules are shown on top. Reprinted with permission from M. Schunack, L. Petersen, A. Kiihnle, E. Laegsgaard, I. Stensgaard, I. Johannsen and F. Besenbacher, Physical Review Letters 86, 456 (2001). Copyright (2001) by the American Physical Society.

Figure 1.4. Plan view of Cu(l 00)(x 2 /2)R45°-0 surface reconstruction. The outermost layer Cu atoms are shown more lightly shaded than those of the underlying substrate to show more clearly the missing-row structure of this outermost layer. The full lines show the surface unit mesh.

Fig. 25 a Homochiral pairs are observed in STM after adsorption of racemic cysteine. L-cysteine pairs are tilted CW away from the [110] substrate direction as clearly observed via STM (inset). Reprinted with permission of the authors, b Superposition of the most stable structure obtained from DFT calculations and a STM image acquired after annealing of a D-cysteine layer at 380 K. By removing the top-most atomic row underneath the cysteine double row structure the (1 x 1) Au(110) surface is restored. Reprinted with permission from [78]. Copyright (2004) American Physical Society... 

Scheme 1.9. Regioisomeric adducts resulting from [3 + 2] cycloaddition of diazomethane or azide dipoles to C70 (central row), and subsequent extrusion of N2 under formation of the respective 6-6 closed (top row) or 6-5 open (bottom row) structures.

Between the pyramids the surface is not in the final c(2x2) structural state, but shows a row structure parallel to the [100] and [010] directions, i.e. there are two domains of this structure (Fig. 9a). These row structures are also found on top of mostly the rectangular type pyramids (Fig. 10, right panel). The rows are made of three atomic rows, presumably Pt (see LDOS argument) with a local (100) symmetry, a square with one atom in the middle. The lateral distance of the atoms in direction of the rows is approximately 4 A. Occasionally one of the middle atoms is missing giving the rows a beaded appearance. This reconstruction seems to be an obvious way of the (001) surface to handle the Sn deficiency in the surface - quite different from the other two cases, (111) and... 

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