Surface antiphase domains

Barth C, Henry CR (2003). Atomic resolution imaging of the (001) surface of UHV cleaved MgO by dynamic scanning force microscopy. Phys Rev Lett, 91, 196102 Kulawik M, Nihus N, Rust H-P, Freund H-J (2003). Atomic structure of antiphase domain boundaries of a thin Al Oj film on NiAl(l 10). Phys Rev Lett, 91, 256101 20. Kresse G, Schmid M, Napetschnig E, Shishkin M, Kohler L, Varga P (2005). Structure of the ultrathin aluminum oxide film on NiAl(l 10). Science, 308, 1440... 

We shall see that this description of B explains most of its special properties (except for the existence of antiphase domains and extra spots in the electron diffraction pattern that can be deduced also by comparison to the A structure, but taking into account some more sophisticated details). We shall first study the common properties of the A and B phases the orientation of thin crystals and the existence of steps at the surface of these crystals. Then we shall study the special properties of B and finally the A, B phase transformation that we have shown to be cooperative. 

It should be noted that the LEED patterns observed for halogen adsorption on the bcc surfaces can also be explained by regularly spaced antiphase domain boundaries [82B]. Such models, however, yield unrealistically small distances between the adsotbed halogen atoms and require complicated concerted motion of the adatoms to obtain continuously varying LEED patterns [82J], Further, electronic band stmcture studies performed on chemisorbed halogen layers on Fe(llO) support the formation of the incommensurate compression phases described above [91M],... 

Rychetsky, I. Deformation of crystal surfaces in ferroelastic materials caused by antiphase domain boundaries. J. Rhys. Condens. Matter 9,4583-4592 (1997)... 

FEED pattern shows directly the size and orientation of the surface unit cell. Flowever, the symmetry of the unit cell is not necessarily identical to the experimentally observed symmetry in LEED including spot intensities. The properties of symmetries such as rotation axes or mirror planes affect the intensities of the spots. The distinction between the structural symmetries of the surface and symmetries observed among spot intensities in LEED can be performed by changing the direction of the incident electron beam. At oblique incidence only mirror planes can be observed when the incident beam is parallel to the symmetry plane, otherwise the diffraction pattern exhibits no symmetry. In cases where the surface is not well ordered one may obtain additional symmetry information from the diffused LEED spots. The characteristic distribution of diffuse intensity in reciprocal space indicates the existence of short-range ordered antiphase domains or twin domains. 

APD antiphase domain CCGSE concentric-circle grating surface-... 

By analogy with Si (001) epitaxy we can expect formation of antiphase domains. A diamond structure reconstructed to a 2 x 1 dimer structure allows two positions for new dimer nucleation (34). If, after nucleation, two islands grow and interact, there is a 50% probability that they will have opposite phases. At the intersection, two kinds of antiphase boundaries exist (34). Such boundaries have been revealed on hydrogen-etched CVD diamond surfaces by STM. In Fig. 10 we see an orthogonal network of dimer rows. The distance between rows is 5 A. In addition to antiphase boundaries, there are narrower rows that correspond to 3 X 1 reconsfiuction. In such reconstruction we have one dihydride row (35). 

P2(N,M,r) make evaluation difficult if many different states are present, but we restrict the discussion to a two-state model, because that already shows the most important features. We consider two cases roughness on a surface with two levels and a reconstruction with two antiphase domains. For more complex roughness models, we refer to the literature [41]. 

Another illustrative application of the two-state model is for a (2x1) reconstructed surface. On such a surface, two domains are possible that are shifted by one bulk lattice spacing (antiphase domains) (see Figure 3.4.2.37). The treatment of this system is fully analogous to that of the surface with two levels of roughness. The... 

It was Sato and Toth who showed that when low-energy imperfections such as antiphase domain boundaries were introduced into an ordered structure without changing the near-neighbor coordination, the positions of (some of) the Brillouin zone boundaries were altered so that they followed an expanding Fermi surface and maintained structural stability despite the increase in electron concentration due to alloying. Consider, for example, the ordered AuCu I structure. The reduced Brillouin zone is made up of 100 planes and the second extended zone is made up of (002) and (110 -type planes. Mapped back in the reduced zone, the second zone has a square cross section normal to the axis. With two electrons per primitive cell, the Fermi surface overlaps the 001 planes of the first zone and touches the 110 planes of the second zone. 

Planar defects surfaces, grain boundaries, small-angle grain boundaries, cell walls, planar stacking faults, antiphase domain walls, shear structures, segregation of impurity atoms to interfaces... 

Au is an excellent electrode material. It is inert in most electrochemical environments, and its surface chemistry is moderately well understood. It is not, however, the substrate of choice for the epitaxial formation of most compounds. One major problem with Au is that it is not well lattice matched with the compounds being deposited. There are cases where fortuitous lattice matches are found, such as with CdSe on Au(lll), where the Vs times the lattice constant of CdSe match up with three times the Au (Fig. 63B) [115,125]. However, there is still a 0.6% mismatch. A second problem has to do with formation of a compound on an elemental substrate (Fig. 65) [384-387]. Two types of problems are depicted in Fig. 65. In Fig. 65A the first element incompletely covers the surface, so that when an atomic layer of the second element is deposited, antiphase boundaries result on the surface between the domains. These boundaries may then propagate as the deposit grows. In Fig. 65b the presence of an atomically high step in the substrate is seen to also promote the formation of antiphase boundaries. The first atomic layer is seen to be complete in this case, but when an atomic layer of the second element is deposited on top, a boundary forms at the step edge. Both of the scenarios in Fig. 65 are avoided by use of a compound substrate. 

Fig. 30.31. Photomicrograph on an etched (001) surface of Gd2(Mo04)j taken in reflected light. Trench-like etch pits develop along APB s in the negatively charged surfaces but not in the positively charged surface in the reverse domain. This is a typical distribution of antiphase boundaries in crystals cooled through Tc when very little domain wall movement occurs (Barkley and Jeitschko, 1973).

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