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Transport Properties (transport + property)
Kinds of Transport Properties Selected AbstractsYttrium ,-Diketonate Glyme MOCVD Precursors: Effects of the Polyether Length on Stabilities, Mass Transport Properties and Coordination SpheresEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2004Graziella Malandrino Abstract The glyme adducts of trishexafluoroacetylacetonato yttrium, [Y(hfa)3·monoglyme], [Y(hfa)3·diglyme], [Y(hfa)3·(H2O)2·triglyme] and [Y(hfa)2·tetraglyme]+[Y(hfa)4], {CH3(OCH2CH2)nOCH3, n = 1 monoglyme, 2 diglyme, 3 triglyme and 4 tetraglyme}, were synthesized and characterized by elemental analysis, mass spectrometry, and IR, 1H and 13C NMR spectroscopy. Additionally, [Y(hfa)3·monoglyme] and [Y(hfa)3·diglyme] were characterized by single-crystal X-ray diffraction studies. The mass-transport properties of these adducts were investigated by thermogravimetric analysis, differential scanning calorimetry, evaporation-rate measurements and chemical vapour-deposition experiments. There is evidence of high volatility and very good thermal stabilities with a residue lower than 2,4 %. Vaporization-rate experiments proved that all adducts are well-suited for metal-organic chemical vapour-deposition experiments. The [Y(hfa)3·monoglyme] complex was successfully applied in the low-pressure MOCVD process of YBaCuO HTc superconductor using a multimetal molten single source. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Microstructure and Transport Properties of Cellular Materials: Representative Volume ElementADVANCED ENGINEERING MATERIALS, Issue 10 2009Emmanuel Brun The representative volume element (RVE) plays a central role in efforts to predict the effective thermo-physical and transport properties of heterogeneous materials. A quantitative definition of its size is proposed in this work. It is shown that RVE depends on the morphological or physical property being investigated. The methodology is applied to real samples of open-celled materials (such as metallic foam) whose structure is obtained from X-Ray microtomography. [source] Structural and Room-Temperature Transport Properties of Zinc Blende and Wurtzite InAs NanowiresADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Shadi A. Dayeh Abstract Here, direct correlation between the microstructure of InAs nanowires (NWs) and their electronic transport behavior at room temperature is reported. Pure zinc blende (ZB) InAs NWs grown on SiO2/Si substrates are characterized by a rotational twin along their growth-direction axis while wurtzite (WZ) InAs NWs grown on InAs (111)B substrates have numerous stacking faults perpendicular to their growth-direction axis with small ZB segments. In transport measurements on back-gate field-effect transistors (FETs) fabricated from both types of NWs, significantly distinct subthreshold characteristics are observed (Ion/Ioff,,,2 for ZB NWs and ,104 for WZ NWs) despite only a slight difference in their transport coefficients. This difference is attributed to spontaneous polarization charges at the WZ/ZB interfaces, which suppress carrier accumulation at the NW surface, thus enabling full depletion of the WZ NW FET channel. 2D Silvaco-Atlas simulations are used for ZB and WZ channels to analyze subthreshold current flow, and it is found that a polarization charge density of ,1013,cm,2 leads to good agreement with experimentally observed subthreshold characteristics for a WZ InAs NW given surface-state densities in the 5,×,1011,5,×,1012,cm,2 range. [source] Thickness-Dependent Structural Evolutions and Growth Models in Relation to Carrier Transport Properties in Polycrystalline Pentacene Thin Films,ADVANCED FUNCTIONAL MATERIALS, Issue 17 2007H.-L. Cheng Abstract Thickness-dependent crystal structure, surface morphology, surface energy, and molecular structure and microstructure of a series of polycrystalline pentacene films with different film thickness ranging from several monolayers to the several hundred nanometers have been investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), contact angle meter, and Raman spectroscopy. XRD studies indicate that thin film polymorphs transformation behaviours are from the orthorhombic phase to the thin-film phase and then to the triclinic bulk phase as measured by the increased tilt angle (,tilt) of the pentacene molecule from the c- axis toward the a- axis. We propose a growth model that rationalizes the ,tilt increased along with increasing film thickness in terms of grain size and surface energy varying with film growth using AFM combined with contact angle measurements. The vibrational characterizations of pentacene molecules in different thickness films were investigated by Raman spectroscopy compared to density functional theory calculations of an isolated molecule. In combination with XRD and AFM the method enables us to distinguish the molecular microstructures in different thin film polymorphs. We proposed a methodology to probe the microscopic parameters determining the carrier transport properties based on Davydov splitting and the characteristics of aromatic C,C stretching modes in Raman spectra. When compared to the triclinic bulk phase at a high thickness, we suggest that the first few monolayer structures located at the dielectric surface could have inferior carrier transport properties due to weak intermolecular interactions, large molecular relaxation energy, and more grain boundaries. [source] Semiconductive Polymer Blends: Correlating Structure with Transport Properties at the Nanoscale (Adv. Mater.ADVANCED MATERIALS, Issue 7 2004385.) To view the original paper click http://dx.doi.org/10.1002/adma.200305747 [source] Variability in Transport Properties for Blackbutt Timber in New South Wales: Within and Between-Tree VariabilityASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2006S. J. Cabardo Variability is a key issue in the processing of biological materials, in this case the hying of hardwood timber. This paper reports the measurements of variability of transport properties. which are relevant to the drying of blackbutt, Eucalyptus pilularis Sm, from northern New South Wales. Specifically, within-tree and between-tree variations are reported for two blackbutt regrowth logs. An analysis of variance showed that some timber properties were affected by the board positions within-trees and between-trees. Circumferential and radial efects were significant for the within- tree variability of most transport properties. Similarly, radial and circumferential effects were signlficant for most of the transport parameters between trees, but can be tentatively stated because only two regrowth logs were assessed. Timber boards with high initial moisture contents had higher rates of diffirsion and low basic densities using principal components analysis. A possible reason is that if there is less wood material per unit volume, these vacant spaces may be occupied by water, and there is also less resistance for diffusive transport of moisture. [source] Influence of Growth Temperature and Carrier Flux on the Structure and Transport Properties of Highly Oriented CrO2 on Al2O3 (0001),CHEMICAL VAPOR DEPOSITION, Issue 10 2007M. Sousa Abstract In this work we report on the structure and magnetic and electrical transport properties of CrO2 films deposited onto (0001) sapphire by atmospheric pressure (AP)CVD from a CrO3 precursor. Films are grown within a broad range of deposition temperatures, from 320 to 410,°C, and oxygen carrier gas flow rates of 50,500,sccm, showing that it is viable to grow highly oriented a -axis CrO2 films at temperatures as low as 330,°C i.e., 60,70,°C lower than is reported in published data for the same chemical system. Depending on the experimental conditions, growth kinetic regimes dominated either by surface reaction or by mass-transport mechanisms are identified. The growth of a Cr2O3 interfacial layer as an intrinsic feature of the deposition process is studied and discussed. Films synthesized at 330,°C keep the same high quality magnetic and transport properties as those deposited at higher temperatures. [source] ChemInform Abstract: Transport Properties of Undoped and Br-Doped PbTe Sintered at High-Temperature and Pressure , 4.0 GPa.CHEMINFORM, Issue 2 2010Yongkwan Dong Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Compositional Control of Electrical Transport Properties in the New Series of Defect Thiospinels, Ga1-xGexV4S8-, (0 , x ,1).CHEMINFORM, Issue 2 2010Iwona Szkoda Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Crystal, Electric Transport Properties and Electronic Structures of the Ti5M1-xSb2+x Series of Compounds (M: Cr, Mn, Fe, Co, Ni, Cu).CHEMINFORM, Issue 21 2009A. Tkachuk Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Transport Properties and Lithium Insertion Study in the p-Type Semi-Conductors AgCuO2 and AgCu0.5Mn0.5O2.CHEMINFORM, Issue 18 2009F. Sauvage Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Structure and Electrical Transport Properties of the Ordered Skutterudites MGe1.5S1.5 (M: Co, Rh, Ir).CHEMINFORM, Issue 32 2008Paz Vaqueiro Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Magnetic and Transport Properties of Zn0.4Fe2.6O4 Thin Films with Highly Preferential OrientationCHEMINFORM, Issue 13 2007Z. L. Lu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Solvothermal Synthesis and Electrical Transport Properties of Skutterudite CoSb3.CHEMINFORM, Issue 36 2006J. L. Mi Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Structural, Magnetic and Transport Properties of Sr2Fe1-xMgxMoO6 (0 , x , 1) Double Perovskites.CHEMINFORM, Issue 44 2005Falak Sher Abstract For Abstract see ChemInform Abstract in Full Text. [source] Electrical Transport Properties of USbSe and USbTe.CHEMINFORM, Issue 38 2005D. Kaczorowski Abstract For Abstract see ChemInform Abstract in Full Text. [source] Anisotropy in Magnetic and Transport Properties of GdCrSb3.CHEMINFORM, Issue 46 2004D. D. Jackson Abstract For Abstract see ChemInform Abstract in Full Text. [source] Preparation and Transport Properties of New Oxide Ion Conductors KNb1-xMgxO3-, by High Temperature and Pressure.CHEMINFORM, Issue 20 2003Liping Li Abstract For Abstract see ChemInform Abstract in Full Text. [source] Low Temperature Preparation and Transport Properties of Ternary Pb,Bi ,Te Alloy.CHEMINFORM, Issue 18 2003Yuan Deng Abstract For Abstract see ChemInform Abstract in Full Text. [source] Tetrachloro-substituted Perylene Bisimide Dyes as Promising n-Type Organic Semiconductors: Studies on Structural, Electrochemical and Charge Transport PropertiesCHEMPHYSCHEM, Issue 1 2004Zhijian Chen Twisted ,-systems: The highly twisted 1,6,7,12-tetrachloro-substituted perylene bisimides possess an improved electron affinity. The nonplanar nature of these molecules facilitates a slipped brickstone-type rather than a columnar stacking of the ,-systems, with a potentially useful two dimensional contact feature. These compounds show isotropic charge carrier mobilities as high as up to 0.14 cm2,V,1 s,1 (see graphic). [source] A new approach for numerical simulation of quantum transport in double-gate SOIINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 6 2007Tarek M. Abdolkader Abstract Numerical simulation of nanoscale double-gate SOI (Silicon-on-Insulator) greatly depends on the accurate representation of quantum mechanical effects. These effects include, mainly, the quantum confinement of carriers by gate-oxides in the direction normal to the interfaces, and the quantum transport of carriers along the channel. In a previous work, the use of transfer matrix method (TMM) was proposed for the simulation of the first effect. In this work, TMM is proposed to be used for the solution of Schrodinger equation with open boundary conditions to simulate the second quantum-mechanical effect. Transport properties such as transmission probability, carrier concentration, and I,V characteristics resulting from quantum transport simulation using TMM are compared with that using the traditional tight-binding model (TBM). Comparison showed that, when the same mesh size is used in both methods, TMM gives more accurate results than TBM. Copyright © 2007 John Wiley & Sons, Ltd. [source] Transport properties of hydrogen-doped (Zr803d20)1,xHx (3d = Co, Ni) metallic glassesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2004I. Kokanovi Abstract The electrical resistivities of hydrogen-doped (Zr803d20)1,xHx (3d = Ni, Co; x , 0.11) metallic glasses have been measured at temperatures between 2 K and 110 K and in magnetic fields up to 1 T for various dopant concentrations. These systems have a high room-temperature resistivity (, > 160 ,, cm) and become superconducting below 4 K. The increase of the room-temperature resistivity and its temperature coefficient with hydrogen dopant concentration is explained as due to an increase of disorder with hydrogen-doping. The temperature and magnetic field dependence of the resistivity has been analysed using theoretical models of weak-localisation and electron,electron interaction in disordered conductors. The hydrogen dopant is found to reduce the effective electron diffusion constant, D, the spin-orbit scattering rate, ,,1so, the superconducting transition temperature, Tc, and broadens the superconducting transition region. The contribution of the Maki-Thompson interaction to the magnetoresistivity is also reduced. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Transport properties in n-type AlGaN/AlN/GaN-superlatticesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008J. Hertkorn Abstract In order to improve the lateral conductivity in optoelectronic devices, we have investigated Si-doped AlGaN/AlN/GaN-superlattices. As a first step we performed calculations of the band structure of Al-GaN/AlN/GaN modulation doped multi heterostructures. Based on these results we worked on optimizing the growth of low Al content (xAl, 20%) superlattices by MOVPE. Several tens of abrupt and graded AlGaN/AlN/GaN-layer pairs could be grown crack-free on 2 ,m thick n-GaN layers deposited on sapphire substrates with AlN nucleation. By Van-der-Pauw Hall measurements, we determined that the lateral conductivity of a 1.5 ,m thick superlattice structure is a factor of four higher than in highly n-doped bulk material with comparable thickness without compromising too much the vertical conductivity as confirmed by two step TLM-measurements. At 4K we could demonstrate an extremely high effective mobility of 18760 cm2/Vs at n=2×1014 cm,2 (R=1.6,/®), a clear verification of our excellent crystal quality. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Transport of cytokinins mediated by purine transporters of the PUP family expressed in phloem, hydathodes, and pollen of ArabidopsisTHE PLANT JOURNAL, Issue 1 2003Lukas Bürkle Summary Nucleobases and derivatives like cytokinins and caffeine are translocated in the plant vascular system. Transport studies in cultured Arabidopsis cells indicate that adenine and cytokinin are transported by a common H+ -coupled high-affinity purine transport system. Transport properties are similar to that of Arabidopsis purine transporters AtPUP1 and 2. When expressed in yeast, AtPUP1 and 2 mediate energy-dependent high-affinity adenine uptake, whereas AtPUP3 activity was not detectable. Similar to the results from cell cultures, purine permeases (PUP) mediated uptake of adenine can be inhibited by cytokinins, indicating that cytokinins are transport substrates. Direct measurements demonstrate that AtPUP1 is capable of mediating uptake of radiolabeled trans -zeatin. Cytokinin uptake is strongly inhibited by adenine and isopentenyladenine but is poorly inhibited by 6-chloropurine. A number of physiological cytokinins including trans- and cis- zeatin are also efficient competitors for AtPUP2-mediated adenine uptake, suggesting that AtPUP2 is also able to mediate cytokinin transport. Furthermore, AtPUP1 mediates transport of caffeine and ribosylated purine derivatives in yeast. Promoter,reporter gene studies point towards AtPUP1 expression in the epithem of hydathodes and the stigma surface of siliques, suggesting a role in retrieval of cytokinins from xylem sap to prevent loss during guttation. The AtPUP2 promoter drives GUS reporter gene activity in the phloem of Arabidopsis leaves, indicating a role in long-distance transport of adenine and cytokinins. Promoter activity of AtPUP3 was only found in pollen. In summary, three closely related PUPs are differentially expressed in Arabidopsis and at least two PUPs have properties similar to the adenine and cytokinin transport system identified in Arabidopsis cell cultures. [source] The Andersen thermostat in molecular dynamicsCOMMUNICATIONS ON PURE & APPLIED MATHEMATICS, Issue 1 2008Weinan E We carry out a mathematical study of the Andersen thermostat [1], which is a frequently used tool in molecular dynamics. After reformulating the continuous- and discrete-time Andersen dynamics, we prove that in both cases the Andersen dynamics is uniformly ergodic. A detailed numerical analysis is presented, establishing the rate of convergence of most commonly used numerical algorithms for the Andersen thermostat. Transport properties such as the diffusion constant are also investigated. It is proved for the Lorentz gas model where there is intrinsic diffusion that the diffusion coefficient calculated using the Andersen thermostat converges to the true diffusion coefficient in the limit of vanishing collision frequency in the Andersen thermostat. © 2007 Wiley Periodicals, Inc. [source] Microstructure and Transport Properties of Cellular Materials: Representative Volume ElementADVANCED ENGINEERING MATERIALS, Issue 10 2009Emmanuel Brun The representative volume element (RVE) plays a central role in efforts to predict the effective thermo-physical and transport properties of heterogeneous materials. A quantitative definition of its size is proposed in this work. It is shown that RVE depends on the morphological or physical property being investigated. The methodology is applied to real samples of open-celled materials (such as metallic foam) whose structure is obtained from X-Ray microtomography. [source] Temperature-Resolved Local and Macroscopic Charge Carrier Transport in Thin P3HT Layers,ADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Patrick Pingel Abstract Previous investigations of the field-effect mobility in poly(3-hexylthiophene) (P3HT) layers revealed a strong dependence on molecular weight (MW), which was shown to be closely related to layer morphology. Here, charge carrier mobilities of two P3HT MW fractions (medium-MW: Mn,=,7,200 g mol,1; high-MW: Mn,=,27,000 g mol,1) are probed as a function of temperature at a local and a macroscopic length scale, using pulse-radiolysis time-resolved microwave conductivity (PR-TRMC) and organic field-effect transistor measurements, respectively. In contrast to the macroscopic transport properties, the local intra-grain mobility depends only weakly on MW (being in the order of 10,2 cm2 V,1 s,1) and being thermally activated below the melting temperature for both fractions. The striking differences of charge transport at both length scales are related to the heterogeneity of the layer morphology. The quantitative analysis of temperature-dependent UV/Vis absorption spectra according to a model of F. C. Spano reveals that a substantial amount of disordered material is present in these P3HT layers. Moreover, the analysis predicts that aggregates in medium-MW P3HT undergo a "pre-melting" significantly below the actual melting temperature. The results suggest that macroscopic charge transport in samples of short-chain P3HT is strongly inhibited by the presence of disordered domains, while in high-MW P3HT the low-mobility disordered zones are bridged via inter-crystalline molecular connections. [source] Engineering Disorder in Superdiffusive Lévy GlassesADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Jacopo Bertolotti Abstract Disorder is known to have a substantial impact on light transport in optical materials. In particular, when properly tuned, disorder can unveil optical properties that common, periodically patterned materials do not possess. In this paper, a method to realize disordered dielectric materials dubbed Lévy glasses, in which light transport is superdiffusive, is presented. The degree of superdiffusion is set by engineering the spatial inhomogeneity of the scatterer density in the material. A model that relates the microscopic parameters to the macroscopic transport properties of Lévy glasses is given and the signature of superdiffusion on the transmission profile in a slab configuration is shown experimentally. [source] Variations in Hole Injection due to Fast and Slow Interfacial Traps in Polymer Light-Emitting Diodes with InterlayersADVANCED FUNCTIONAL MATERIALS, Issue 1 2010M. James Harding Abstract Detailed studies on the effect of placing a thin (10,nm) solution-processable interlayer between a light-emitting polymer (LEP) layer and a poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic)-acid-coated indium tin oxide anode is reported; particular attention is directed at the effects on the hole injection into three different LEPs. All three different interlayer polymers have low ionization potentials, which are similar to those of the LEPs, so the observed changes in hole injection are not due to variations in injection barrier height. It is instead shown that changes are due to variations in hole trapping at the injecting interface, which is responsible for varying the hole current by up to two orders of magnitude. Transient measurements show the presence of very fast interfacial traps, which fill the moment charge is injected from the anode. These can be considered as injection pathway dead-ends, effectively reducing the active contact surface area. This is followed by slower interfacial traps, which fill on timescales longer than the carrier transit time across the device, further reducing the total current. The interlayers may increase or decrease the trap densities depending on the particular LEP involved, indicating the dominant role of interfacial chain morphology in injection. Penetration of the interlayer into the LEP layer can also occur, resulting in additional changes in the bulk LEP transport properties. [source] Microstructural Engineering of Hydroxyapatite Membranes to Enhance Proton ConductivityADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Dongxia Liu Abstract A new approach to enhancing proton conductivity of ceramics is demonstrated by aligning proton conductive pathways and eliminating resistive grain boundaries. Hydroxyapatite (HAP) membranes are synthesized by multistage crystallization onto palladium. The synthesis involves three steps: electrochemical deposition of HAP seeds, secondary hydrothermal crystallization onto the seed layer to promote c -axis growth normal to the substrate, and tertiary hydrothermal crystallization to promote a- axis growth to fill the gaps between the aligned crystals. The c -axis alignment with crystal domains spanning the membrane thickness significantly enhances proton conduction since protons are primarily transported along the c -axes of HAP crystals. The novel HAP membranes display proton conductivity almost four orders of magnitude higher than traditional sintered HAP ceramics. The HAP membranes on palladium hydrogen membrane substrates hold promise for use in intermediate-temperature fuel cells, chemical sensors, and other devices. The synthesis approach presented may also be applied to other ion-conducting membrane materials to enhance transport properties. [source] | |||||||||||||||||||||||||