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  • 1
    Electronic Resource
    Electronic Resource
    Dynamic studies of polymerization in liquid crystal-polymer mixtures (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 6652-6656 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This work studied the dynamic behavior of polymerization in films of liquid crystal (LC)-polymer mixtures by using the pump-probe technique. Chopped Ar+ laser pulses were used as pump beams, and probed by a cw He—Ne laser. The experimental results indicated that the transmission of the probe beam was modulated in response to the chopping frequency of the pump beam. The modulation was such that transmission during the on-time of the pump beam was initially smaller than, then equal to, and finally larger than that in the off-time. Analyzing the transparency difference between the films with and without the Ar+ laser pulse allows us to recognize the three stages of polymerization process, initiation, propagation, and termination. Moreover, both the LC content in the sample and the chopping on/off ratio of the pump beam significantly affected the turning point occurred and the modulation amplitude of the probe beam. A model is proposed to explain these observed results. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371739
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  • 2
    Electronic Resource
    Electronic Resource
    Dynamical studies of gratings formed in polymer-dispersed liquid crystal films (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 679-683 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The use of polymer-dispersed liquid crystal films to fabricate gratings was demonstrated. The written gratings are permanent, but are electrically switchable. In this article, we report the results obtained from the dynamical studies of gratings formed in polymer-dispersed liquid crystal films having various liquid crystal-polymer mixing ratios. The results showed that during the initial phases of formation, a thermal grating effect dominated. Later, it was offset or quenched by the photopolymerization effect which eventually dominated and determined the characteristics of the final grating. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366738
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of oxygen to argon ratio on properties of (Ba,Sr)TiO3 thin films prepared by radio-frequency magnetron sputtering (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 3482-3487 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films of (Ba,Sr)TiO3 on Pt/SiO2/Si substrates were deposited using rf magnetron sputtering at various substrate temperatures and O2/(Ar+O2) mixing ratios (OMR). The crystallinity of the films improved significantly as the OMR increased. The dielectric constant increased with increasing OMR and reached a maximum value at 50% OMR. The leakage current density decreased with increasing oxygen flow, but had a minimum value at 40% OMR. The results for the dielectric constant and the leakage current were interpreted in terms of polarization effect and loss theory. The film deposited at 450 °C and 50% OMR exhibited good surface morphology and had a dielectric constant of 375, a tangent loss of 0.074 at 100 kHz, a leakage current density of 7.35×10−9 A/cm2 at an electric field of 100 kV/cm with a delay time of 30 s, and a charge storage density of 49 fC/μm2 at an applied field of 150 kV/cm. The 10 yr lifetime of time-dependent dielectric breakdown studies indicate that a 50% OMR sample has a longer lifetime than the 0% OMR sample. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365665
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  • 4
    Electronic Resource
    Electronic Resource
    Very strong negative differential resistance real-space transfer transistor using a multiple δ-doping GaAs/InGaAs pseudomorphic heterostructure (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 739-741 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present the observation of an effective real-space transfer process of hot electrons resulting in a very strong negative differential resistance in GaAs/In0.25Ga0.75As/GaAs pseudomorphic heterostructure by growing symmetrically double δ-doping layers on both sides of the InGaAs channel. By Hall measurements, the proposed structure shows carrier mobility as high as 4500 (14 100) cm2/V s at 300 (77) K which is suitable for high-frequency operations. Meanwhile, this structure with a 5×100 μm2 emitter channel reveals extremely sharp charge injection, broad current valley range ((approximately-greater-than)3 V), high transconductance (over 23.5 S/mm), high current driving capability, and high peak-to-valley current ratio (up to 156 000). We also carried out secondary-ion mass spectrometry profiles to confirm the quality of the proposed structure. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114117
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  • 5
    Electronic Resource
    Electronic Resource
    Optically switchable gratings based on polymer-dispersed liquid crystal films doped with a guest–host dye (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 2572-2574 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this work, we add a small amount of a guest–host dye G-206 in the polymer-dispersed liquid crystal mixtures to fabricate holographic gratings. Following formation, the grating is irradiated by a single Ar+ laser beam while probed by a He–Ne laser. Experimental results indicate that the first-order diffracted intensity of the probe beam increases significantly. Such an optically switchable diffraction effect is attributed to thermal expansion. The G-206 dye absorbs the Ar+ laser, subsequently resulting in thermal expansion. The liquid crystal (LC) droplets are then squeezed so that the LC molecules within the droplets are reoriented collectively. Thus, the refractive index difference between the LC-rich and polymer-rich stripes Δn increases. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123901
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  • 6
    Electronic Resource
    Electronic Resource
    A comment on time-reversal symmetry of chiral systems
    Amsterdam : Elsevier
    Chemical Physics Letters 173 (1990), S. 485-488 
    Details
    ISSN: 0009-2614
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0009-2614(90)87240-R
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  • 7
    Electronic Resource
    Electronic Resource
    Polymer-dispersed liquid crystal films for storing optical holographic images (1996)
    Springer
    Optical and quantum electronics 28 (1996), S. 1535-1541 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We have developed an economic liquid crystal-polymer dispersion material that can be used for storing optical holographic images. In this paper, we demonstrate the use of thin samples of this material for such an application. The obtained results show that the written gratings-holograms are permanent, but are electrically switchable. Furthermore, the diffraction efficiency is high and does not change significantly after many tests over a period of months. Thus, we believe this material is promising for practical uses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326223
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