Figure 1

Molecular structure of Y104 (left) and Y105 (right) dyes. As Y104 compound was supplied as a mixture of two isomers, the alternative attachment of the sulfonate group is shown in brackets.Reuse & Permissions

Figure 2

(a) Polarized optical microscopy (POM) and soft x-ray images $(E=285.7\mathrm{eV})$ of samples prepared by different techniques (from left to right): spreading over a Si wafer with applicator rod and drying; from “industrial grade” film, followed by Ba fixation and lift off process; rubbing of LCLC droplet between two ${\mathrm{Si}}_3{\mathrm{N}}_4$ chips and drying out in ${\mathrm{N}}_2$ flow. All images are cropped to a similar field of view. (b) Magnified POM images of Y104 (top) and Y105 (bottom) thin dried films, prepared by the chip-to-chip rubbing procedure. Rubbing (shear) direction is approximately along the horizontal axis. The cross polarizers were positioned at 45° to vertical/horizontal directions to highlight the presence of herringbone-type orientational texture.Reuse & Permissions

Figure 3

Schematic layout of experimental settings. Monochromatized x-ray light is coming from the left and focused by Fresnel zone plate to a $50\mathrm{nm}$ spot on the sample. Transmitted x rays are detected by conversion to visible light by a phosphor and single event detection by a fast photomultiplier. The detection geometry is such that the full radiation cone is measured. The dried liquid crystal thin film is oriented along the shear direction (shown at $\beta$ to horizontal plane). The characteristic herringbone texture is shown as shaded lines. The three top cartoons depict the molecular arrangements and their relative geometry. Individual molecules (shown as plates) with face-to-face alignment form columns (shown as cylinders). Supramolecular alignment creates bundles. Angular misalignment of one patch relative to another (with characteristic mosaic angle $\delta$) leads to the herringbone texture appearance, seen in POM microscope as black-and-white stripes. The liquid crystal director, a vector along which molecules are aligned on average, is pointed along the long axis of the column. In-plane (azimuthal) rotation of the sample leads to variation of the angle between the $E$ vector of the linear polarized x-rays and the normal to the molecular planes normal angle.Reuse & Permissions

Figure 4

(Color online) NEXAFS spectra of Y104/ Y105 dyes. (a) Low-energy part of C $K$ edge NEXAFS, measured at the same sample location but with three different polarizations of the x-ray light. The solid line corresponds to linear polarized light with the $E$ vector horizontal, the dotted line corresponds to linear polarized light with the $E$ vector vertical, and the dashed line corresponds to right circularly polarized light. Extended range C (b), N (c), O (d), and S (e) $K$ edge NEXAFS spectra (upper panel) and linear dichroic signal (bottom) part are plotted. Short vertical lines mark peaks, whose energy and assignment is given in Table . Relevant chemical structural elements are shown as inserts. Note the dichroic measurements correspond to in-plane variation of the $E$ vector to a shear direction.Reuse & Permissions

Figure 5

Spectral angular variation within the domain. The top panel refers to Y104 while the bottom panel refers to Y105. (a) OD images (at $285.7\mathrm{eV}$) of Y104/ Y105 sample taken at approximately 45° sample rotation. Rubbing direction is shown as the bidirectional arrow. Light spots indicate the location where NEXAFS spectra (shown at the right) are extracted. Note that the actual size of the x-ray beam is only $50\mathrm{nm}$, but the data have been averaged over the larger area indicated to account for possible sample misalignment. (b) Low energy C edge NEXAFS spectra variation for different sample rotations. The sample OD at high energy is normalized to unity. The insert plots the variation of the peak intensity as a function of the sample rotation angle. Open markers correspond to Y105 film, dashed to Y104 sample, individual energy intensity are $284.3\mathrm{eV}$ as crosses, $285.6\mathrm{eV}$ as circles, $286.5\mathrm{eV}$ as tip up triangles, $287.7\mathrm{eV}$ as tip down triangles, solid lines are the fit to ${\cos }^2$ function with parameters as described in the text.Reuse & Permissions

Figure 6

(Color) False color image of crystalline film orientational texture, as green (with minimum value as indicated on the color bar) to violet (maximum) color palette: (a) Y104, (b) Y105 thick, and (c) Y105 thin films. For each row, the left panel shows maps of the in-plane mosaic angle (the angle between shear direction and local in-plane LCLC director) map, the middle panel shows maps of the magnitude of in-plane director defined here as a fraction of the molecules with their aromatic core plane oriented normal to the local in-plane director, and the right panel shows maps of the sample thickness, as deduced from x-ray absorption intensity in the $\mathrm{C}1s$ continuum. All images in a given row are rescaled to the same region of interest. White bars show the spatial scale while the shear direction is marked by double sided black arrows below the images.Reuse & Permissions

Figure 7

(Color) (a) Mosaic angle distribution function derived from histograms of the images shown in Figs. 6a, 6b, 6c first column. (b) Magnitude of Fourier transformation (logarithmic scale) of mosaic angle images [Figs. 6a, 6b, 6c] averaged along direction perpendicular to shear and plotted as inverse length function (linear scale from 0.1 to $2{\mathrm{\mu }}^{-1}$ to highlight characteristic length of in-plane undulations). (c) Normalized histogram of the in-plane molecular order distribution for Y104, Y105 thick, and Y105 thin films derived from Figs. 6a, 6b, 6c middle column. (d) Film thickness variation as deduced from Figs. 6a, 6b, 6c right column. For all figures, green curves correspond to Y104 film, dark blue lines to Y105 thick region, and light blue lines to thin section of Y105 film.Reuse & Permissions

Figure 8

(Color) LCLC film characteristic defects. The color coded images (called “molecular orientation maps”) of in-plane angular orientation of LC director (labeled “angle”) and the magnitude of order parameter (labeled “in-plane order”) are taken from Fig. 6a, but truncated to the region of interest, zoomed, rotated by $\sim 120°$ and aligned on top of each other. Those two images have been combined and plotted as a vector field image, where the length of the bars (plotted in blue) are proportional to the magnitude of the order parameter and the bar orientation is given by the LC director angle (chosen here such that bars oriented perpendicular to the in-plane director indicate the aromatic core molecular plane). This image provides a convenient visualization of molecular alignment, as it displays the molecular arrangement if viewed from above the film. Red bars are a hand sketch of molecular alignment expected in the vicinity of a $\frac{1}{2}$ disclination and are only for eye guidance. Thin black dashed lines are the pointers to link the same regions on all maps and cartoons. We also chose to display the angular map as color coded contours superimposed on the “molecular orientation map.” Cartoons (labeled as “model”) placed at the top and sides of the figure show the molecular arrangement associated with each type of defect. Contrary to the bar representation of the molecular alignment, these are drawn as continuous lines resembling molecular columns which permits a 3D representation of the molecular ordering. Model (a) shows in-plane undulation characteristic of LCLC $M$ phase texture with in-plane conical narrowing of undulation period. Molecules (shown as elongated ellipses) ordering along the individual column are drawn on the left; the expected hexagonal packing is omitted. (b) and (c) are models showing column alignment in the vicinity of a $\frac{1}{2}$ disclination, where the columns are rotated in the direction toward the film surface in the form of a dome with an extended wedge on one side.Reuse & Permissions