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Differential Resistance (differential + resistance)

Distribution by Scientific Domains
Polymers and Materials Science44%
Physics and Astronomy44%

Kinds of Differential Resistance

  • negative differential resistance
    		•

    Selected Abstracts

    Comment on "Memory Effect and Negative Differential Resistance by Electrode-Induced Two-Dimensional Single-Electron Tunneling in Molecular and Organic Electronic Devices"

    ADVANCED MATERIALS, Issue 21 2006
    S. Majumdar
    No abstract is available for this article. [source]

    Synthesis, Morphology, and Properties of Poly(3-hexylthiophene)- block -Poly(vinylphenyl oxadiazole) Donor,Acceptor Rod,Coil Block Copolymers and Their Memory Device Applications

    ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010
    Yi-Kai Fang
    Abstract Novel donor,acceptor rod,coil diblock copolymers of regioregular poly(3-hexylthiophene) (P3HT)- block -poly(2-phenyl-5-(4-vinylphenyl)-1,3,4-oxadiaz-ole) (POXD) are successfully synthesized by the combination of a modified Grignard metathesis reaction (GRIM) and atom transfer radical polymerization (ATRP). The effects of the block ratios of the P3HT donor and POXD pendant acceptor blocks on the morphology, field effect transistor mobility, and memory device characteristics are explored. The TEM, SAXS, WAXS, and AFM results suggest that the coil block fraction significantly affects the chain packing of the P3HT block and depresses its crystallinity. The optical absorption spectra indicate that the intramolecular charge transfer between the main chain P3HT donor and the side chain POXD acceptor is relatively weak and the level of order of P3HT chains is reduced by the incorporation of the POXD acceptor. The field effect transistor (FET) hole mobility of the system exhibits a similar trend on the optical properties, which are also decreased with the reduced ordered P3HT crystallinity. The low-lying highest occupied molecular orbital (HOMO) energy level (,6.08 eV) of POXD is employed as charge trap for the electrical switching memory devices. P3HT- b -POXD exhibits a non-volatile bistable memory or insulator behavior depending on the P3HT/POXD block ratio and the resulting morphology. The ITO/P3HT44 - b - POXD18/Al memory device shows a non-volatile switching characteristic with negative differential resistance (NDR) effect due to the charge trapped POXD block. These experimental results provide the new strategies for the design of donor-acceptor rod-coil block copolymers for controlling morphology and physical properties as well as advanced memory device applications. [source]

    Vapor Sorption and Electrical Response of Au-Nanoparticle, Dendrimer Composites,

    ADVANCED FUNCTIONAL MATERIALS, Issue 6 2007
    N. Krasteva
    Abstract Films comprising Au nanoparticles and polyphenylene dendrimers (first and second generation) are deposited onto transducer substrates via layer-by-layer self-assembly and characterized by atomic force microscopy and X-ray photoelectron spectroscopy. Their sorption behavior is studied by measuring the uptake of solvents from the vapor phase with quartz crystal microbalances (QCMs). The resistance of the films is simultaneously monitored. Both sensor types, QCMs and chemiresistors, give qualitatively very similar response isotherms that are consistent with a combination of Henry- and Langmuir-type sorption processes. The sorption-induced increase in relative differential resistance scales linearly with the amount of analyte accumulated in the films. This result is in general agreement with an activated tunneling process for charge transport, if little swelling and only small changes in the permittivity of the film occur during analyte sorption (a first-order approximation). The relative sensitivity of the films to different solvents decreases in the order toluene,,,tetrachloroethylene,>,1-propanol,,,water. Films containing the larger second-generation dendrimers show higher sensitivity than films containing first-generation dendrimers. [source]

    Resonant Tunneling Processes along Conjugated Molecular Wires: A Quantum-Chemical Description

    ADVANCED FUNCTIONAL MATERIALS, Issue 11-12 2002
    Y. Karzazi
    Abstract Molecular electronics research is a very active area in the field of nanotechnology. It is now well established that individual or self-assembled molecules can behave as nanoscopic switches in transistor and diode configurations. Molecular wires inserted into nanopores and contacted by two metallic electrodes can also be used as active elements for the fabrication of resonant tunneling diodes (RTDs). The RTD current/voltage (I/V) characteristics can display a negative differential resistance (NDR) behavior (i.e., a negative slope in the I/V curve) for reasons that are not yet fully understood. Here we describe a possible mechanism at the quantum-chemical level that is based on conformational effects and accounts for the experimental observation of strong NDR signatures in substituted phenylene ethynylene oligomers. The occurrence of a peak current in the I/V curves is rationalized by analyzing the evolution of the one-electron structure of the molecular wires upon application of a static electric field aligned along the molecular axis (the field simulates the driving voltage applied between the two electrodes in the RTD devices). The results of our calculations provide a general basis to develop strategies for the design of molecular wires displaying an NDR behavior. [source]

    Conductance through a redox system in the Coulomb blockade regime: Many-particle effects and influence of electronic correlations

    PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 1-2 2010
    Sabine Tornow
    Abstract We investigate the transport characteristics of a redox system weakly coupled to leads in the Coulomb blockade regime. The redox system comprises a donor and acceptor separated by an insulating bridge in a solution. It is modeled by a two-site extended Hubbard model which includes on-site and inter-site Coulomb interactions and the coupling to a bosonic bath. The current,voltage characteristics is calculated at high temperatures using a rate equation approach. For high voltages exceeding the Coulomb repulsion at the donor site the calculated transport characteristics exhibit pronounced deviations from the behavior expected from single-electron transport. Depending on the relative sizes of the effective on-site and inter-site Coulomb interactions on one side and the reorganization energy on the other side we find either negative differential resistance or current enhancement. Schematic view of the redox system with donor (D) and acceptor (A) coupled to the leads L and R. The electronic degrees of freedom of the DA system are coupled to the environment comprising internal vibrations and the solvent dynamics. The current is calculated as a function of the bias voltage Vb and gate voltage Vg. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Anomalous current,voltage characteristics of thin polymer films

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 2 2003
    V. A. Kolesnikov
    Abstract In this paper we have investigated organic light emitting diodes with such electroluminescent materials as aromatic polyimide, poly,N-vinylcarbazole (PVK) and dye doped PVK. N-type current,voltage characteristics with negative differential resistance for the thin polymeric and organic films are analyzed. No reasonable explanation has been provided for this phenomenon until now. Here we suggest that a polymer(organic)/metal interface containing various inhomogeneities and metal spikes is responsible for this effect. We detect also the black-body radiation, whose temperature exceeds both the melting point and the sublimation temperature of the metal of the electrode. We suppose that the current density through the spike in any cases is large enough to cause the explosion of the tip of the spike and the detected radiation has the hot plasma origin. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Current filamentation and negative differential resistance in C60 diodes

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2008
    Philipp Stadler
    Abstract Current-Voltage (IV) measurements of C60 thin film diodes in the temperature range of 300,4.2 K are presented. The fullerene diodes exhibit space charge limited currents as well as reversible voltage instabilities (S-shape IV characteristics) at temperatures below 200 K and at high current densities. The instabilities are similar to certain charge transport effects in amorphous inorganic semiconductors, which are explained by injection of holes and electrons at the same time and charge trapping near the electrodes. Beyond certain current densities conductive filaments in the fullerene bulk phase are formed. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Differential seedling resistance to the eyespot pathogens, Oculimacula yallundae and Oculimacula acuformis, conferred by Pch2 in wheat and among accessions of Triticum monococcum

    PLANT PATHOLOGY, Issue 5 2010
    C. Burt
    Eyespot is an economically important stem-base disease of wheat caused by two fungal species: Oculimacula yallundae and Oculimacula acuformis. This study investigated the efficacy of two sources of resistance, viz. the genes Pch1, introgressed into hexaploid wheat from Aegilops ventricosa, and Pch2, identified in wheat cv. Cappelle Desprez, against O. yallundae and O. acuformis separately. In a series of seedling bioassays Pch1 was found to be highly effective against both species. Although Pch2 was found to confer resistance against both pathogen species, it was significantly less effective against penetration from O. yallundae than O. acuformis. Furthermore, a quantitative trait locus (QTL) analysis was not able to locate any resistance to O. yallundae on chromosome 7A of Cappelle Desprez. This has important implications for the use of Pch2 in commercial cultivars as it is necessary to have genes that confer resistance to both pathogens for effective eyespot control. In addition, a set of 22 T. monococcum accessions was screened for resistance to both O. yallundae and O. acuformis to identify potentially novel resistances and to assess the accessions for evidence of differential resistance to the eyespot species. Significant differences in resistance to the two pathogens were identified in four of these lines, providing evidence for differential resistance in T. monococcum. This study demonstrates that future screening for novel sources of eyespot resistance should investigate both pathogen species. [source]

    Tunneling in quantum confined GaAs ultrashallow sidewall tunnel junctions

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2006
    Takeo Ohno
    Abstract Temperature dependence of current-voltage (I - V ) characteristics of quantum-confined GaAs ultra-shallow sidewall p+n+ tunnel junctions has been investigated. The sidewall tunnel junctions with junction depths ranging from 5 nm to 50 nm were achieved by the combination of intermittent injection of TEG/AsH3 in an ultra high vacuum and a wet etching process of the GaAs growth layer. From the I - V results, abrupt negative differential resistances (NDR) were observed, which relate to direct/indirect tunneling and sub-band formation. The change in the number instances of NDR and their voltage positions also depended on the junction depth. Mechanisms of tunneling in the present sidewall tunnel junction will be discussed from the point of the sub-band formation in conduction bands. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]