A comparative atomic force microscopic study of liquid crystal films: transferred freely-suspended vs. Langmuir-Blodgett. Morphology, lattice, and manipulation

Overney, René M.; Meyer, Ernst; Frommer, Jane; Güntherodt, H.‐J.; Decher, Gero; Reibel, J.; Sohling, Ulrich

doi:10.1021/la00025a063

Cited by 45 publications

(16 citation statements)

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“…For FPP the value of ␥ϭ13ϫ10 Ϫ3 agrees well with an independent direct measurement . It is about a factor of 2 smaller than the values reported for nonfluorinated liquid crystals, which is due to a reduction of the surface energy due to fluorination of the alkyl chain (Pang and Clark, 1994). The value obtained for K is quite normal but the value of B is much larger than the others in Table III.…”

Section: Interpretation Of Diffuse Reflectivitymentioning

confidence: 51%

Structure and fluctuations of smectic membranes

2003

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Smectic membranes are perfect model systems for studying low-dimensional phase transitions and the associated fluctuations. During the last two decades we have seen important progress in the understanding of the structure and fluctuation behavior of these systems, driven by both new experimental techniques and theoretical developments. Phase transitions are reviewed involving liquid, hexatic, and crystalline layers, which provide several types of model system for low-dimensional melting. The authors discuss the influence of the surfaces on the physical properties of the membranes as well as the crossover from three-to two-dimensional behavior. The layer-displacement fluctuations in smectic membranes have been investigated by specular and diffuse x-ray reflectivity. Theoretical and experimental aspects of the displacement-displacement correlation function are discussed. Of special interest is the quenching or enhancement of fluctuations at surfaces, which is directly related to the phenomenon of surface ordering. The authors consider the conditions under which fluctuations are conformal throughout a membrane, and then the dynamic aspects of the layer-displacement correlation function, which include the effects of finite size, surface tension, and viscous dissipation. This leads in smectic membranes to a discrete spectrum of elastic and viscous relaxation modes, which have been studied experimentally with coherent x rays at third-generation synchrotron sources. The fluctuating character of crystalline-B membranes is also considered. Finally, the article looks briefly at thinning transitions, smectic membranes of chiral molecules, smectic films on substrates, and applications to biologically relevant systems. Open questions and future trends in the field are discussed. CONTENTS I. Motivation and Scope 182 II. Smectic Membranes 183 A. Smectic liquid-crystal phases 183 B. Main features of x-ray patterns 185

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Section: Interpretation Of Diffuse Reflectivitymentioning

confidence: 51%

Structure and fluctuations of smectic membranes

2003

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“…The indentation and controlled modification of LB films using the atomic force microscope ͑AFM͒ has been reported recently on several systems ͑cadmium arachidate, 9,10,12 -tricosenoic acid, 11,14 alkyl ethoxy-carboxylate, 13 behenic acid, 15 polyglutamate, 16 and octadecylaminoethyl-dehydrocorbathien͒. 17 Patterning is achieved either by increasing the load on the tip at constant speed ͑usually in the range 10-100 nN, scan speed below 10 m/s͒, [9][10][11][13][14][15][16] by increasing the scan speed ͑up to 10 m/s͒ at constant load, 13,18 or by increasing both the load and scan speed ͑100 nN, 5 m/s͒.…”

Section: Introductionmentioning

confidence: 99%

High speed layer by layer patterning of phthalocyanine Langmuir–Blodgett films by the atomic force microscope

Bourgoin

Sudiwala

Palacin

1996

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Imaging of organic molecular films using a scanning near-field optical microscope combined with an atomic force microscope J.Anisotropic Langmuir-Blodgett films of phthalocyanine derivatives have been patterned using an atomic force microscope to scan the surface of the film at high scan rate ͑Ͼ100 m/s͒. The depth of the periodic grooved lines, of width down to 50 nm, formed perpendicular to the fast scan direction can be controlled to the monolayer level through the effect of the load ͑a few nanonewtons͒ applied to the tip. It is shown that the patterning results from an oscillation in the feedback loop resulting in a periodic force modulation of a few nanonewtons along each scan line. Using the same principle, we show that the microscope can be modified to write patterns of arbitrary form by the superposition of a given voltage waveform onto the Z piezo voltage.

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“…There are reports that indicate that smectic ordering can be induced at the surface of the nematic phase 4. There are also numerous reports on aggregation and pattern formation by LC molecules on surfaces 5–7. Studies into the factors governing the patterns on the surface are important.…”

Section: Introductionmentioning

confidence: 99%

Liquid Crystals at Interfaces

Gupta

Manjuladevi

2012

Israel Journal of Chemistry

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The ordering in liquid crystals (LCs) can be influenced by an interface. Some of these molecules adsorbed at the air‐water interface yield a stable Langmuir monolayer. They exhibit numerous surface phases, which are classified on the basis of intermolecular separation and ordering. These surface phases are governed by the molecular interactions and the ambient experimental conditions such as temperature, humidity, pH, and ion content of the subphase. In this article, the role of molecular interactions on the surface behavior of several rodlike LCs are discussed. The Langmuir monolayer of a cholesteric LC exhibits an interesting low density liquid (L1′) phase with tilted molecules. Brewster angle microscopy reveals stripe patterns, which arise due to the precession of the tilted molecules. It is demonstrated that this molecular precession can be controlled by the relative humidity, presence of cations in the subphase, and incorporation of appropriate molecular species. The Langmuir monolayer and Langmuir‐Blodgett films of a novel rod‐disc hybrid LC are discussed.

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A comparative atomic force microscopic study of liquid crystal films: transferred freely-suspended vs. Langmuir-Blodgett. Morphology, lattice, and manipulation

Cited by 45 publications

References 0 publications

Structure and fluctuations of smectic membranes

Structure and fluctuations of smectic membranes

High speed layer by layer patterning of phthalocyanine Langmuir–Blodgett films by the atomic force microscope

Liquid Crystals at Interfaces

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