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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Both ac and dc conduction processes through thin Langmuir–Blodgett (LB) films of the dodecyloxyphenylurethane of 2-bromo-5 (2'-hydroxyethoxy) tetracyanoquinodimethan (DDOP-C-TCNQ, a redox-active molecule) sandwiched between dissimilar metal (Pt and Mg) electrodes have been studied. The dc conduction changed from a linear I/V characteristic for the lowest applied voltages (±20 mV) to a symmetric nonlinear characteristic obeying a ln I∝V1/4 dependence for voltages up to ±1.5 V, in as-prepared samples. For larger positive voltages, a large increase in current was observed with the dependence changing to a ln I∝V3 law, a dependence not reported previously for metal/LB film/metal systems. For increased negative voltages, the ln I∝V1/4 was again observed. For low applied ac fields, the conductance was found to follow a ωn law with a value of n close to 0.8. The effect of heat annealing the samples was also studied with significant differences in the observed changes in conductance between bilayer and monolayer structures. Emphasis was placed on understanding the conduction process through the single DDOP-C-BHTCNQ layer film. For the monolayer device, hysteresis is observed in the positive bias, and both as-prepared and annealed samples exhibit ln I∝V3 behavior. Such behavior was not observed for the corresponding negative voltages, indicating rectification across a distance approximated by the length of an individual molecule. Possible models of the three-dimensional arrays for both monolayer and multilayer metal/LB film/Mg structures are presented. The weight of existing experimental results does not support the Aviram–Ratner "molecular rectifier'' concept for presently known Pt/LB monolayer/Mg devices.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 1603-1612 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new bifunctional material, [2-nitro-5-(N-methyl-N-octadecylamino)benzoic acid] (NMOB), has been synthesized and its film forming properties investigated by the Langmuir–Blodgett technique. Pressure-area isotherms indicate that NMOB forms stable monolayers below 40 mN/m which can be transferred to solid substrates. Multilayered samples were prepared on both transmission and reflection substrates and investigated by Fourier transform infrared (FTIR) spectroscopy. Polarization measurements indicate that the orientation of the NMOB molecules is definitely anisotropic with the alkyl tail tilted considerably relative to the surface while the dye chromophore has its plane oriented primarily parallel to the surface. Changes in this orientation upon interleaving these NMOB layers with deuterated cadmium arachidate spacer layers were also investigated both at room and elevated temperatures.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1916-1918 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Metal/Langmuir–Blodgett monolayer/metal devices, where the monolayer consists of the dodecyloxyphenylcarbamate of 2-bromo, 5(2'-hydroxyethoxy) tetracyanoquinodimethan, a donor-σ-acceptor molecular system, have been constructed, and dc current-voltage (I-V) characteristics of these devices were recorded at room temperature. For biases of ±20 mV, the I-V characteristics are linear, changing to a nonlinear form for higher voltages. This nonlinear characteristic exhibited a ln(I)∝V1/4 dependence for both positive and negative voltages up to ±1 V. For positive voltages 〉+2.0 V for as-prepared devices and 〉+1.5 V for annealed devices, a ln(I)∝V3 dependence was observed, revealing a very large increase in current for small voltage changes. Such behavior was not observed for corresponding negative voltages, indicating rectification across a distance approximated by the length of an individual molecule.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 5 (1995), S. 305-320 
    ISSN: 1057-9257
    Keywords: rectification ; Langmuir-Blodgett films ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: In the field of molecular scale electronics the drive is towards the fabrication of self-assembled, organic, nanoscale architectures which will have an active role to play in novel electronic devices. As a formative step towards this goal the creation of an organic analogue to the p-n junction was proposed by Aviram and Ratner in the 1970s. In their proposal a monomolecular layer of a charge transfer species controls current flow between a pair of metal electrodes, allowing easy flow for only one polarity of the applied voltage. Such metal/molecular layer/metal structures have now been fabricated, utilising the self-ordering properties of Langmuir-Blodgett films to form the organic layer, with one dimension of the device being reduced to the molecular scale. The fabrication techniques involved in the generation of these M/LB/M junctions are now described along with the present understanding of conduction mechanisms through such nanoscale thickness junctions. These structures clearly show that the organic molecular layers can control current passage in electronic devices emulating some of the characteristics of an inorganic semiconducting p-n junction.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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