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  • 1985-1989  (7)
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Material
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Characterization of layer-tilted state in ferroelectric liquid-crystal cells by electro-optical switchings (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 6654-6661 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using an electro-optical method, we have determined the director tilt angle, the layer-tilt angle, and the quiescent-state azimuthal angles of a surface-stabilized ferroelectric liquid-crystal (SSFLC) cell as a function of temperature in the smectic C phase. The method is based on a collective switching of the director's conical motion due to the interaction of the external field with the spontaneous polarization and the dielectric anisotropy of the liquid-crystal medium, together with a one-elastic constant free-energy model. Using the equation of total free energy, we have proved that only splayed states could be stabilized in layer-tilted geometry, but bistable cells could still be obtained. When the surface interactions at both substrate surfaces are nonidentical, the SSFLC cell will exhibit two distinct quiescent states: one stable and the other quasistable. The twist angles of the director from top to bottom substrates at quiescent states and the ratio of the surface polar to nonpolar interaction are deduced. The experimental observation and calculation on an overshoot in the rising part of the optical response upon bipolar switching are also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342019
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Depolarization field and ionic effects on the bistability of surface-stabilized ferroelectric liquid-crystal devices (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 125-127 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Based on a collective switching model coupled to a simplified continuity equation for impurity ions, the internal electric field and light transmission of a surface-stabilized (SS), layer-tilted ferroelectric liquid-crystal (FLC) cell with insulating alignment layers have been calculated as a function of time, under bipolar voltage pulses. The polarization and ionic charges, accumulated on the interfaces between the FLC medium and alignment layers, tend to partially screen the external on-field and generate a depolarization field to reverse the spontaneous polarization when the external field is off. When the thickness of the alignment layer is greater than 1000 A(ring), it is difficult to achieve bistability using FLC mixtures with a spontaneous polarization larger than approximately 20 nC/cm2. For bistability to occur in a SSFLC cell with high spontaneous polarization, thin insulating or conducting alignment layers are preferred. We also found that the existence of impurity ions in a SSFLC cell is always detrimental to bistability in spite of their low mobilities ((approximately-equal-to)10−7 cm2/V s).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102121
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Measurements of empty cell gap for liquid-crystal displays using interferometric methods (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 4780-4781 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to determine the empty cell gap of a liquid-crystal (LC) cell to better than 1% accuracy, the empty LC cell has been modeled as an optical medium consisting of seven layers with an air gap representing the true cell gap in the middle layer. The given index of refraction and thickness for each layer, optical reflections as a function of wavelength ranging from 500 to 650 nm have been calculated. To simulate the experimental measurement, the apparent cell gaps were deduced from reflection peaks and compared with the true cell gaps in the region of 5–10 μm. It was found that the difference between the apparent and true cell gaps was larger than 0.66 μm using a 0.1-μm polyimide as an aligning layer coated on top of the transparent indium-tin-oxide electrode of 0.04 μm in thickness. This modeling is applicable to three interferometric methods commonly used for the measurement of an empty cell gap.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341199
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Observation of a doping-dependent orientation effect of the depletion of silicon self-interstitials during oxidation (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 1812-1815 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We conducted an experiment to study the growth kintetics of the oxidation-induced stacking faults (OSF) of n- and p-type (100) and (111) Si wafers with resistivities of 0.8–15 Ω cm. The OSF size data are as expected for the p-type (100) and (111) wafers as well as for the n-type (100) wafers. For the n-type (111) 0.8–2 Ω cm wafers, however, no OSF were generated at a temperature higher than ∼1100 °C and those grown at 1050 °C are considerably smaller than expected. This indicates that in the n-type (111) wafers there exists a mechanism that depletes Si self-interstitials, in addition to the normal mechanism of interstitial injection. Obviously, the effect is dependent on orientation as well as on doping. The same kind of effect was found before via diffusion studies, which, however, did not appear as doping dependent. We propose that this discrepancy is apparently due to the fact that, in one diffusion experiment, p+ (111) materials (Ga implanted to a concentration exceeding 1020 cm−3) were oxidized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.334408
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  • 5
    Electronic Resource
    Electronic Resource
    Electro-optical effects of uniform layer-tilted state in ferroelectric liquid crystals (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 2400-2403 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental results on the electro-optical behavior of uniform layer-tilted ferroelectric liquid crystals (FLCs) are reported for the first time. The special arrangement of the uniform layer-tilted state, with the spontaneous polarization parallel to the cell substrates, responds equally to either polarity of the electric field without a storage effect. Due to the presence of a small pretilt angle of the director of the FLC caused by rubbing alignment, the saturated light transmission through such a FLC cell between crossed polarizers shows a characteristic asymmetry with respect to different polarities of the field. The saturated light transmission and the angular position to null the asymmetry have been used to determine the cone angle and the pretilt angle of the FLC director, respectively. The switch-on time at 15 V is less than 23 μs for both polarities of the field. Field induced switch-off time is 34 μs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337958
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    A simple method to determine the pretilt angle of nematic guest-host liquid crystals (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 2820-2822 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The phase retardation-extremum method offers a fast and simple way to measure the pretilt angle of nematic liquid crystal (NLC) cells. Due to optical absorption of the dissolved dyes, such a method is not suitable to measure the pretilt angle of a guest-host (GH) NLC cell. We have obtained a simple and fast method to determine the pretilt angle of a GH NLC cell from the incident angle corresponding to the minimum transmission intensity of a polarized light passing through the GH cell. Using this simple method, we have measured the pretilt angles of GH NLC cells with different dye concentrations, and compared them with the pretilt angles of the corresponding host NLCs measured by the retardation-extremum method. Excellent agreement between the two methods was observed with a dye concentration of not more than 1%. Within our experimental errors, dye concentration of up to 5.8% (by weight) seems not to change the pretilt angle of the GH NLC from that of the corresponding host NLC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337064
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  • 7
    Electronic Resource
    Electronic Resource
    Dynamic fracture toughness (1986)
    Springer
    International journal of fracture 30 (1986), S. 275-285 
    Details
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Résumé On passe en revue les relations entre la ténacité à la rupture dynamique et la vitesse de propagation d'une fissure, dans le cas de l'Homalite-100, du polycarbonate, de l'acier 4340 durci, et de nitrure de silicium assemblé par liaisons chimiques. On relève les divergences par rapport aux données publiées, et leurs causes probables. On attribue la dispersion des données en partie aux fluctuations observées dans les vitesses de la fissure. Les résultats confirment les conclusions précédemment exprimées, selon lesquelles d'une part la relation qui lie la ténacité à la rupture dynamique à la vitesse de la fissure dépend de l'éprouvette, et d'autre part le facteur dynamique d'intensité de contraintes correspondant à l'arrêt d'une rupture n'est pas une propriété univoque du matériau.
    Notes: Abstract Dynamic fracture toughness versus crack velocity relations of Homalite-100, polycarbonate, hardened 4340 steel and reaction bonded silicon nitride are reviewed and discrepancies with published data and their probable causes are discussed. Data scatter in published data are attributed in part to the observed fluctuations in crack velocities. The results reaffirmed our previous conclusion that the dynamic fracture toughness versus crack velocity relation is specimen dependent and that the dynamic crack arrest stress intensity factor is not a unique material property.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00019707
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