Stripe domain structure

Ali et al. (1976) and Grundy et al. (1977) have studied the effect of radiation damage (ion and electron) on the stripe domain structure. Argon ion doses below lO -lO ions cm do not affect the structure films with a thickness of more than 800 A have a perpendicular anisotropy and show bubbles after application of a normal bias. Doses of 10 ions cm destroy the perpendicular anisotropy. 

The analysis in the last paragraph has shown that the incommensurate Xe layer on Pt(lll) at misfits of about 6% is a striped phase with fully relaxed domain walls, i.e. a uniaxially compressed layer. For only partially relaxed domain walls and depending on the extent of the wall relaxation and on the nature of the walls (light, heavy or superheavy) additional statellites in the (n, n) diffraction patterns should appear. Indeed, closer to the beginning of the C-I transition, i.e. in the case of a weakly incommensurate layer (misfits below 4%) we observe an additional on-axis peak at Qcimm + e/2 in the (2,2) diffraction pattern. In order to determine the nature of the domain walls we have calculated the structure factor for the different domain wall types as a function of the domain wall relaxation following the analysis of Stephens et al. The observed additional on-axis satellite is consistent with the occurrence of superheavy striped domain wails the observed peak intensities indicate a domain wall width of A=i3-5Xe inter-row distances. With... 

Using a scanning Hall microscope, a stripe-shaped domain structure has been observed in a (Ga.Mn)As sample with tensile strain and perpendicular easy axis (Shono et al. 2000 Fukumura et al. 2001). The Baukhausen noise due to the scattering from the domain wall movement has also been observed in magnetotransport measurements (Hayashi et al. 2000). 

Fig. 9.50 The various domain structures observable in epitaxial iron garnet films (a) maze, (b) bubbles , and (c) stripe.

Fig. 6 Two-dimensional arrays assembled from DNA components, (a) A two-component array made from a DAE and a DAE + J motif both 4 x 16 nm in this projection, where the extra domain is indicated by a filled black circle. Sticky ends are represented geometrically, (b) A four-component array, where the stripes occur every 64 nm. (c) An array made of two TX molecules (A and B), a rotated TX molecule (C). and a double helix (D). (d) A four-arm junction can also be used to produce an array, (d.l) and (d.2) show that the four-arm junction assumes a two-domain structure, where the two domains are at an angle 60° to each other. Although flexible in its own right, four of them can produce a well-structured parallelogram (d.3) that can self-assemble into a 2D array (d.4). View this art in color at www.dekker.com.)...

Asymmetric block copolymers which form hexagonal or cubic-packed spherical morphologies in the bulk, form stripe or circular domain patterns in two dimensions, as illustrated in Figure 5. The stripe pattern results from cylinders lying parallel to the substrate, and a circular domain surface pattern occurs when cylinders are oriented perpendicular to the substrate, or for spheres at the surface. Bicontinuous structures cannot exist in two dimensions therefore the gy-roid phase is suppressed in thin films. More complex multiple stripe and multiple circular domain structures can be formed at the surface of ABC triblocks (83). Nanostructures in block copolymer films can be oriented using electric fields (if the difference in dielectric permittivity is sufficient), which will be important in applications where parallel stripe (84) or perpendicular cylinder configurations (85) are desired. 

One of the remarkable phenomena in nematic liquid crystals is the appearance of modulated structures under the action of an electric field [1-3]. These structures are characterized by the periodic distortion of the nematic director field in a certain preferred direction, and could be optically visualized as regular patterns of black and white stripes (domains) arranged perpendicular to the distortion plane. If the direction of distortion is degenerate in the layer plane, domains form a rectangular, hexagonal, or some other type of lattice, which could periodically transform to each other, i.e., oscillating domain patterns appear. 

The formation of transient domain patterns aligned perpendicular to the initial director during the relaxation process of the Frederiks transition has been known since the earliest observations by Carr [20] and Guyon et al. [21]. After these observations some other transient domain structures were found in thermotropic and lyotropic liquid crystal with perpendicular [22], parallel [23], oblique [24], and two-dimensional [25] striped patterns relative to the initial orientation of the director in both the electric and magnetic fields. 

Quasi-bookshelf layer structure with stripe domains)... 

Fig. 6.1.4 Changes in texture induced by AC-field treatment, (a) Texture I. Initial virgin texture with chevron layer structure and zigzag defects, (b) Textures II. A rooftop texture is observed after the application of an AC field of medium strength, (c) Texture HI. A quasi-bookshelf layer structure with stripe domains is observed after the apphcation of a strong AC field.

Figure 5.14 6CB on water far below the NI transition. All the domains here have the same color, that is, the same thickness. Between crossed polarizers, the edge of the striped domains shows a planar structure (crossed extinctions). The domains smaller than the wavelength have a planar radial structure with a defect in the center. 

Domain Mode. A remarkable domain structure has recently been observed in FLCs possessing high spontaneous polarization (>100 nC cm ) [193-195]. A very stable spatially periodic optical pattern arises in layers of FLCs with their molecules oriented parallel to the substrates after a dc field treatment of the cell. The stripes are oriented perpendicular to the director orientation and their period is inversely proportional to the polarization magnitude squared, and independent of cell thickness. 

Summarizing these facts it follows that the different parameters need to be optimized to obtain a required slope of the elec-trodistortional curve for a certain application and avoid the occurrence of striped domains or the formation of a twisted structure with a twist of -180° for the temperature regime of operation. 

Reprinted with permission from M. Seul. L.R. Monar, L. O Gorman and R. Vttelfe, Morphology and local structure in labyrinthine stripe domain phase. Science254 6 6- Q 8, Fig. 3 (1991). Copyright 1991 American Association for the... 

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