Electrical properties conductors

Kikuchi K, Murata K, Honda Y, NamUd T, Saito K, Ishiguro T, Kobayashi K, Ikemoto I (1987) On ambient-pressure superconductivity in organic conductors electrical properties of (DMET)2l3, (DMET)2l2Br and (DMET)2lBr2. J Phys Soc Jpn 56 3436-3439... 

Chemical properties of deposited monolayers have been studied in various ways. The degree of ionization of a substituted coumarin film deposited on quartz was determined as a function of the pH of a solution in contact with the film, from which comparison with Gouy-Chapman theory (see Section V-2) could be made [151]. Several studies have been made of the UV-induced polymerization of monolayers (as well as of multilayers) of diacetylene amphiphiles (see Refs. 168, 169). Excitation energy transfer has been observed in a mixed monolayer of donor and acceptor molecules in stearic acid [170]. Electrical properties have been of interest, particularly the possibility that a suitably asymmetric film might be a unidirectional conductor, that is, a rectifier (see Refs. 171, 172). Optical properties of interest include the ability to make planar optical waveguides of thick LB films [173, 174]. 

Semiconductors (qv) are materials with resistivities between those of conductors and those of insulators (between 10 and 10 H-cm). The electrical properties of a semiconductor determine the hmctional performance of the device. Important electrical properties of semiconductors are resistivity and dielectric constant. The resistivity of a semiconductor can be varied by introducing small amounts of material impurities or dopants. Through proper material doping, electron movement can be precisely controlled, producing hmctions such as rectification, switching, detection, and modulation. 

Electrical properties Relating to the resistance, electrical capacity, and insulating characteristics of a conductor or electrical device. 

Many ingredients, especially those that are conductive, may affect electrical properties. Most plastics, which are poor conductors of current, build up a charge of static electricity. Antistatic agents can be added to attract-moisture, reducing the likelihood of a spark or discharge. 

Basic physical properties of sulfur, selenium, and tellurium are indicated in Table 1.3. Downward the sulfur sub-group, the metallic character increases from sulfur to polonium, so that whereas there exist various non-metallic allotropic states of elementary sulfur, only one allotropic form of selenium is (semi)metallic, and the (semi)metallic form of tellurium is the most common for this element. Polonium is a typical metal. Physically, this trend is reflected in the electrical properties of the elements oxygen and sulfur are insulators, selenium and tellurium behave as semiconductors, and polonium is a typical metallic conductor. The temperature coefficient of resistivity for S, Se, and Te is negative, which is usually considered... 

Landauer proposed in 1957 the first mesoscopic theoretical approach to charge transport [176]. Transport is treated as a scattering problem, ignoring initially all inelastic interactions. Phase coherence is assumed to be preserved within the entire conductor. Transport properties, such as the electrical conductance, are intimately related to the transmission probability for an electron to cross the system. Landauer considered the current as a consequence of the injection of electrons at one end of a sample, and the probability of the electrons reaching the other end. The total conductance is determined by the sum of all current-carrying eigenmodes and their transmission probability, which leads to the Landauer formula of a ID system ... 

The electrical properties of materials are important for many of the higher technology applications. Measurements can be made using AC and/or DC. The electrical properties are dependent on voltage and frequency. Important electrical properties include dielectric loss, loss factor, dielectric constant, conductivity, relaxation time, induced dipole moment, electrical resistance, power loss, dissipation factor, and electrical breakdown. Electrical properties are related to polymer structure. Most organic polymers are nonconductors, but some are conductors. 

Figure 6.8 One dimensional schematic representation of the energy momentum curve for seven electrons in a conductor with (a) no applied electric field and (b) an applied electric field. Reprinted, by permission, from L. Solymar, and D. Walsh, Lectures on the Electrical Properties of Materials, 5th ed., p. 427. Copyright 1993 by Oxford University Press.

Composite-based PTC thermistors are potentially more economical. These devices are based on a combination of a conductor in a semicrystalline polymer—for example, carbon black in polyethylene. Other fillers include copper, iron, and silver. Important filler parameters in addition to conductivity include particle size, distribution, morphology, surface energy, oxidation state, and thermal expansion coefficient. Important polymer matrix characteristics in addition to conductivity include the glass transition temperature, Tg, and thermal expansion coefficient. Interfacial effects are extremely important in these materials and can influence the ultimate electrical properties of the composite. 

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