Tilted-film experiments

The infra-red measurements were of two types, normal-film measurements with the sample sandwiched between KBr plates, and tilted-film experiments with the sample sandwiched between 45° prisms of KBr, in each case with layers of Nujol to provide optical matching. Whereas the 1616 cm 1 Raman line occurs in a region well clear of other lines so that it was satisfactory to measure peak intensities, the infra-red spectrum of PET shows many overlapping bands. Accurate assessment of absorption intensities therefore requires the computer separation of the spectrum into a set of overlapping peaks (shown to be Lorentzian in profile) and a linear background. The procedures adopted and the band assignments are discussed in detail by Hutchinson et al. 6). 

One of the key experimental results leading to the elucidation of this overall structural puzzle involved depolarized reflected light microscopy (DRLM) studies on NOBOW freely suspended films in the high-temperature SmCP phase.48 In the freely suspended films it appears that only one phase is observed, which is assumed to be the phase forming the majority domains in the EO cells. The DRLM experiment provides two key results. First, thin films of any layer number have a uniformly tilted optic axis, suggesting all of the layer interfaces are synclinic. Second, films of even-layer number are nonpolar, while films of odd-layer number are polar, with the polar axis oriented normal to the plane of the director tilt (lateral polarization). 

The treatment can be modified to include effects of the temperature development and tilting of the susceptor by using the temperature dependence of the diffiision coefficient and adjusting d and (191). In this manner, the experimental data can be correlated, but the model has limited capability for predicting behavior beyond the particular set of experiments used to fit the model. In fact, because of the low values of the Reynolds number (<50) in typical horizontal CVD reactors, film theory and simple... 

Over the past several years, Gruen and coworkers have examined the SH response from iron electrodes in alkaline solutions [45, 53, 172]. In their work on polycrystalline iron, they concluded that the potential dependent SH response which was observed during surface oxidation could be attributed to two intermediate phases on the electrode surface between the passive film at oxidative potentials and the reduced metal at hydrogen evolution potentials [53]. They have recently extended this work to Fe(110). In this study [172], they examined the SH rotational anisotropy from this crystal under ambient conditions. They found that the experiments reveal the presence of both twofold and threefold symmetric species at the metal/oxide interface. When their data is fit to the theory of Tom et al. [68], they conclude that the measured three-fold symmetric oxide is found to be tilted by 5° from the Fe(110) plane. The two-fold symmetric structure is aligned with the Fe(110) surface. 

In order to evaluate quantitatively the orientation of vibrational modes from the dichroic ratio in molecular films, we assume a uniaxial distribution of transition dipole moments in respect to the surface normal, (z-axis in Figure 1). This assumption is reasonable for a crystalline-like, regularly ordered monolayer assembly. An alternative, although more complex model is to assume uniaxial symmetry of transition dipole moments about the molecular axis, which itself is tilted (and uniaxially symmetric) with respect to the z-axis. As monolayers become more liquid-like, this may become a progressively more valid model (8,9). We define < > as the angle between the transition dipole moment M and the surface normal (note that 0° electric field of the evenescent wave (2,10), in the ATR experiment are given by equations 3-5 (8). 

Figure 9 Absorption spectrum (a) and electrochromism (b) of [Ru(bpy)3] dissolved in a thin polymer film at 77 K. Absorption and electrochromism spectra are taken through semitransparent conducting electrodes. Electrochromism is usually measured with the externally applied electric field parallel to the propagation direction koflight( = 0°). Experiments can also be made with the film tilted away from the normal to the propagation direction (Drawn from data in Oh and Boxer )...

Vortices in superconductors can be observed quantitatively by interference microscopy [2.18, 2.19] and Lorentz microscopy [2.20] with our 350 kV holography electron microscope [2.21]. In the experiments we conducted, a superconductive thin film was tilted with respect to both the electron beam and the magnetic field. 

Figure 13.15. (a) Schematic set-up of the surface plasinon resonance experiment (b) experimental results (symbols) with calculated curves (solid lines). Spectra of 0, 2,4, 6, and 8 monolayers of a LB-filin of 3-thienylpcntadecanoic acid on an Ag film (450 nm) ate shown in curves a-e, respectively. Evaluation of the results indicate a thickness of 2.33 nm per monolayer which is smaller than the geometric film thickness calculated from the length of the molecule at a tilt of 10° (c) schematic representation of a bi-layer on a hydrophilic substrate. In the layers the molecules are oriented upright and the thiophene parts (T) partially interpenetrate, resulting in a diminished layer thickness. Reproduced fi om ref 97 by kind permission of Elsevier. 

The earlier setup of using ion-selective electrodes as an FI detector employed an electrode tilted at about 45°, with the sample/carrier flowing continuously over its sensing surface. The electrode was adjusted so that the surface film thus formed kept contact with the effluent solution, the latter being maintained at constant level in the out-flow reservoir, in which the reference electrode was submeiged. This cascade design, seemingly simple, requires some skill, experience, and patience from the operator, and appears to lack the robustness of a routinely applicable detector. 

Thin films of isotactic PMEPL prepared by direct melt crystallization on a microscope grid show the single crystal-like electron diffraction pattern illustrated in Fig. 4. If it is assumed that this diffraction pattern, obtained witli irradiation normal to the sample surface, is the hkO reciprocal lattice, the unit cell parameters a and b can be explicitly evaluated as 9.10 A and 7.44 A, respectively, with y = 90 . Unfortunately no higher order reflections were recorded from tilted samples, presumably because of the weak intensity of the hkl reflections accessible through such experiments. The periodicity along the c-direction was therefore evaluated from epitaxially crystallized samples. The c-axis dimension was found to be 4.75 A. 

In nanostructured parylene columnar films, the columns tilted at an angle of 57-63° relative to the surface, during sliding contact in some cases a mechanical anisotropy emerges [115]. Microscale sliding friction experiments were performed on nanostructured poly(chloro-/7-xylylene) films. 

Figure 16.2 shows P t,T) of one of the experiments. The tracking curve appears smooth and demonstrates the reliability of the tilt-angle determination. Tilt-angle variation is an issue because the oriented PP film is heated until it becomes a viscous melt. Therefore, the material shrinks and bends in the synchrotron X-ray beam. 

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