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Sample records for electrical transport properties

  1. Electrical Transport Properties of Liquid Al-Cu Alloys

    NASA Astrophysics Data System (ADS)

    Thakore, B. Y.; Khambholja, S. G.; Suthar, P. H.; Jani, A. R.

    2010-06-01

    Electrical transport properties viz. electrical resistivity, thermoelectric power and thermal conductivity of liquid Al-Cu alloys as a function of Cu concentration have been studied in the present paper. Ashcroft empty core model potential has been used to incorporate the ion-electron interaction. To incorporate the exchange and correlation effects, five different forms of local field correction functions viz. Hartree, Taylor, Ichimaru et al., Farid et al. and Sarkar et al. have been used. The transport properties of binary system have been studied using Faber-Ziman formulation combined with Ashcroft-Langreth (AL) partial structure factor. The computed values of electrical resistivity are compared with experimental data and for low Cu concentration, good agreement has been observed. Further, thermoelectric power and thermal conductivity have also been predicted.

  2. Electrical transport properties of manganite powders under pressure

    NASA Astrophysics Data System (ADS)

    Rodríguez, M. G.; Leyva, A. G.; Acha, C.

    2012-08-01

    We have measured the electrical resistance of micrometric to nanometric powders of the LaPryCaMnO3 (LPCMO with y=0.3) manganite for hydrostatic pressures up to 4 kbar. By applying different final thermal treatments to samples synthesized by a microwave assisted denitration process, we obtained two particular grain characteristic dimensions (40 nm and 1000 nm) which allowed us to analyze the grain size sensitivity of the electrical conduction properties of both the metal electrode interface with manganite (Pt/LPCMO) and the intrinsic intergranular interfaces formed by the LPCMO powder, conglomerate under the only effect of external pressure. We also analyzed the effects of pressure on the phase diagram of these powders. Our results indicate that different magnetic phases coexist at low temperatures and that the electrical transport properties are related to the intrinsic interfaces, as we observe evidences of a granular behavior and an electronic transport dominated by the Space Charge limited Current mechanism.

  3. Electrical Transport Properties of Liquid Sn-Sb Binary Alloys

    NASA Astrophysics Data System (ADS)

    Thakore, B. Y.; Suthar, P. H.; Khambholja, S. G.; Jani, A. R.

    2010-06-01

    The study of electrical transport properties viz. electrical resistivity, thermo electrical power and thermal conductivity of liquid Sn-Sb binary alloys have been made by our well recognized single parametric model potential. In the present work, screening functions due to Hartree, Taylor, Ichimaru et al.. Farid et al.. and Sarkar et al.. have been employed to incorporate the exchange and correlation effects. The liquid alloy is studied as a function of its composition at temperature 823 K according to the Faber-Ziman model. Further, thermoelectric power and thermal conductivity have been predicted. The values of electrical resistivity of binary alloys computed with Ichimaru et al. and Farid et al.. screening function are in good agreement with the experimental data.

  4. Single tube electric transport properties of synthesized Titania nanotubes

    NASA Astrophysics Data System (ADS)

    Abdelmoula, Mohamed; Menon, Latika

    2011-03-01

    Titania nanotube arrays fabricated by means of electrochemical anodization is currently the main interest of several research groups due to its promising applications. The high aspect ratio, durability, cheap and scalable fabrication technique make it highly attractive material for efficient solar cell. In this regard extensive research work is being carried out to investigate its properties. In our previous work we were able to find a mechanism for separating a single titania nanotube from the titania nanotube arrays and to measure its electric transport properties using e-beam lithography technique, In this work we investigated the effect of thermal annealing on the transport properties, we studied the effect of different annealing temperatures, heating and cooling rates, and in different gases. As a result, we were able to find the optimal annealing conditions to enhance the transport properties in blank titania nanotube. Under these optimal conditions, we were able to study the effect of coating TNTs with N719 dye and gold nanoparticles on the transport properties. As a result of our work we were able to optimize the treatments for more efficient solar cell fabrication.

  5. The electrical transport properties of liquid Rb using pseudopotential theory

    SciTech Connect

    Patel, A. B. Bhatt, N. K. Thakore, B. Y. Jani, A. R.; Vyas, P. R.

    2014-04-24

    Certain electric transport properties of liquid Rb are reported. The electrical resistivity is calculated by using the self-consistent approximation as suggested by Ferraz and March. The pseudopotential due to Hasegawa et al for full electron-ion interaction, which is valid for all electrons and contains the repulsive delta function due to achieve the necessary s-pseudisation was used for the calculation. Temperature dependence of structure factor is considered through temperature dependent potential parameter in the pair potential. Finally, thermo-electric power and thermal conductivity are obtained. The outcome of the present study is discussed in light of other such results, and confirms the applicability of pseudopotential at very high temperature via temperature dependent pair potential.

  6. The electrical transport properties of liquid Rb using pseudopotential theory

    NASA Astrophysics Data System (ADS)

    Patel, A. B.; Bhatt, N. K.; Thakore, B. Y.; Vyas, P. R.; Jani, A. R.

    2014-04-01

    Certain electric transport properties of liquid Rb are reported. The electrical resistivity is calculated by using the self-consistent approximation as suggested by Ferraz and March. The pseudopotential due to Hasegawa et al for full electron-ion interaction, which is valid for all electrons and contains the repulsive delta function due to achieve the necessary s-pseudisation was used for the calculation. Temperature dependence of structure factor is considered through temperature dependent potential parameter in the pair potential. Finally, thermo-electric power and thermal conductivity are obtained. The outcome of the present study is discussed in light of other such results, and confirms the applicability of pseudopotential at very high temperature via temperature dependent pair potential.

  7. Synthesis and electrical transport properties of SnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Chaki, S. H.; Deshpande, M. P.; Chaudhary, M. D.; Tailor, J. P.; Mahato, K. S.

    2013-02-01

    The SnS nanoparticles were synthesized at ambient temperature by simple wet chemical method. The stoichiometric and structural characterization was done by EDAX and XRD techniques respectively. The crystallite size was determined using Scherrer's formula and Hall-Williamson plot using XRD data. The electrical transport properties studies were carried out on pellets prepared by hydraulic pressing of SnS nanoparticles. The thermoelectric power and dc resistivity variation with temperature was studied on the pellets. Room temperature Hall effect measurement was made on the pellet. The obtained results are discussed in details.

  8. Synthesis and electrical transport properties of Gd doped nanocrystalline ceria

    NASA Astrophysics Data System (ADS)

    Anirban, Sk.; Sinha, A.; Dutta, A.

    2013-06-01

    In this paper we report synthesis and electrical properties of Ce1-xGdxO2-δ (x=0.05-0.2) materials. The materials were prepared using the citrate auto ignition method. The XRD patterns indicate the single phase of the prepared materials. The electrical properties were studied using impedance spectroscopy in a temperature range 250°C to 550°C. It has been observed that the total ionic conductivity increases with the increase in Gd concentration. The electrical data analysis was done using the conductivity formalism.

  9. Electrical transport properties of CaB6

    NASA Astrophysics Data System (ADS)

    Stankiewicz, Jolanta; Sesé, Javier; Balakrishnan, Geetha; Fisk, Zachary

    2014-10-01

    We report results from a systematic electron-transport study in a broad temperature range on 12 CaB6 single crystals. None of the crystals were intentionally doped. The different carrier densities observed presumably arise from slight variations in the Ca:B stoichiometry. In these crystals, the variation of the electrical resistivity and of the Hall effect with temperature can be consistently accounted for by the model we propose, in which B-antisite defects (B atom replacing Ca atom) are "amphoteric." The magnetotransport measurements reveal that most of the samples we have studied are close to a metal-insulator transition at low temperatures. The magnetoresistance changes smoothly from negative—for weakly metallic samples—to positive values—for samples in a localized regime.

  10. Computing and the electrical transport properties of coupled quantum networks

    NASA Astrophysics Data System (ADS)

    Cain, Casey Andrew

    In this dissertation a number of investigations were conducted on ballistic quantum networks in the mesoscopic range. In this regime, the wave nature of electron transport under the influence of transverse magnetic fields leads to interesting applications for digital logic and computing circuits. The work specifically looks at characterizing a few main areas that would be of interest to experimentalists who are working in nanostructure devices, and is organized as a series of papers. The first paper analyzes scaling relations and normal mode charge distributions for such circuits in both isolated and open (terminals attached) form. The second paper compares the flux-qubit nature of quantum networks to the well-established spintronics theory. The results found exactly contradict the conventional school of thought for what is required for quantum computation. The third paper investigates the requirements and limitations of extending the Thevenin theorem in classic electric circuits to ballistic quantum transport. The fourth paper outlines the optimal functionally complete set of quantum circuits that can completely satisfy all sixteen Boolean logic operations for two variables.

  11. Electrical transport properties of single-layer WS2.

    PubMed

    Ovchinnikov, Dmitry; Allain, Adrien; Huang, Ying-Sheng; Dumcenco, Dumitru; Kis, Andras

    2014-08-26

    We report on the fabrication of field-effect transistors based on single layers and bilayers of the semiconductor WS2 and the investigation of their electronic transport properties. We find that the doping level strongly depends on the device environment and that long in situ annealing drastically improves the contact transparency, allowing four-terminal measurements to be performed and the pristine properties of the material to be recovered. Our devices show n-type behavior with a high room-temperature on/off current ratio of ∼10(6). They show clear metallic behavior at high charge carrier densities and mobilities as high as ∼140 cm(2)/(V s) at low temperatures (above 300 cm(2)/(V s) in the case of bilayers). In the insulating regime, the devices exhibit variable-range hopping, with a localization length of about 2 nm that starts to increase as the Fermi level enters the conduction band. The promising electronic properties of WS2, comparable to those of single-layer MoS2 and WSe2, together with its strong spin-orbit coupling, make it interesting for future applications in electronic, optical, and valleytronic devices. PMID:25069042

  12. The effect of electron induced hydrogenation of graphene on its electrical transport properties

    SciTech Connect

    Woo, Sung Oh; Teizer, Winfried

    2013-07-22

    We report a deterioration of the electrical transport properties of a graphene field effect transistor due to energetic electron irradiation on a stack of Poly Methyl Methacrylate (PMMA) on graphene (PMMA/graphene bilayer). Prior to electron irradiation, we observed that the PMMA layer on graphene does not deteriorate the carrier transport of graphene but improves its electrical properties instead. As a result of the electron irradiation on the PMMA/graphene bilayer, the Raman “D” band appears after removal of PMMA. We argue that the degradation of the transport behavior originates from the binding of hydrogen generated during the PMMA backbone secession process.

  13. First-principles calculations of thermal, electrical, and thermoelectric transport properties of semiconductors

    NASA Astrophysics Data System (ADS)

    Zhou, Jiawei; Liao, Bolin; Chen, Gang

    2016-04-01

    The transport properties of semiconductors are key to the performance of many solid-state devices (transistors, data storage, thermoelectric cooling and power generation devices, etc). An understanding of the transport details can lead to material designs with better performances. In recent years simulation tools based on first-principles calculations have been greatly improved, being able to obtain the fundamental ground-state properties of materials (such as band structure and phonon dispersion) accurately. Accordingly, methods have been developed to calculate the transport properties based on an ab initio approach. In this review we focus on the thermal, electrical, and thermoelectric transport properties of semiconductors, which represent the basic transport characteristics of the two degrees of freedom in solids—electronic and lattice degrees of freedom. Starting from the coupled electron-phonon Boltzmann transport equations, we illustrate different scattering mechanisms that change the transport features and review the first-principles approaches that solve the transport equations. We then present the first-principles results on the thermal and electrical transport properties of semiconductors. The discussions are grouped based on different scattering mechanisms including phonon-phonon scattering, phonon scattering by equilibrium electrons, carrier scattering by equilibrium phonons, carrier scattering by polar optical phonons, scatterings due to impurities, alloying and doping, and the phonon drag effect. We show how the first-principles methods allow one to investigate transport properties with unprecedented detail and also offer new insights into the electron and phonon transport. The current status of the simulation is mentioned when appropriate and some of the future directions are also discussed.

  14. Electrical Transport Properties of Polymorphic MoS2.

    PubMed

    Kim, Jun Suk; Kim, Jaesu; Zhao, Jiong; Kim, Sungho; Lee, Jin Hee; Jin, Youngjo; Choi, Homin; Moon, Byoung Hee; Bae, Jung Jun; Lee, Young Hee; Lim, Seong Chu

    2016-08-23

    The engineering of polymorphs in two-dimensional layered materials has recently attracted significant interest. Although the semiconducting (2H) and metallic (1T) phases are known to be stable in thin-film MoTe2, semiconducting 2H-MoS2 is locally converted into metallic 1T-MoS2 through chemical lithiation. In this paper, we describe the observation of the 2H, 1T, and 1T' phases coexisting in Li-treated MoS2, which result in unusual transport phenomena. Although multiphase MoS2 shows no transistor-gating response, the channel resistance decreases in proportion to the temperature, similar to the behavior of a typical semiconductor. Transmission electron microscopy images clearly show that the 1T and 1T' phases are randomly distributed and intervened with 2H-MoS2, which is referred to as the 1T and 1T' puddling phenomenon. The resistance curve fits well with 2D-variable range-hopping transport behavior, where electrons hop over 1T domains that are bounded by semiconducting 2H phases. However, near 30 K, electrons hop over charge puddles. The large temperature coefficient of resistance (TCR) of multiphase MoS2, -2.0 × 10(-2) K(-1) at 300 K, allows for efficient IR detection at room temperature by means of the photothermal effect. PMID:27399325

  15. Electric field control of magnetic properties and magneto-transport in composite multiferroics.

    PubMed

    Udalov, O G; Chtchelkatchev, N M; Beloborodov, I S

    2015-05-13

    We study magnetic state and electron transport properties of composite multiferroic system consisting of a granular ferromagnetic thin film placed above the ferroelectric substrate. Ferroelectricity and magnetism in this case are coupled by the long-range Coulomb interaction. We show that magnetic state and magneto-transport strongly depend on temperature, external electric field and electric polarization of the substrate. Ferromagnetic order exists at finite temperature range around ferroelectric Curie point. Outside the region the film is in the superparamagnetic state. We demonstrate that magnetic phase transition can be driven by an electric field and magneto-resistance effect has two maxima associated with two magnetic phase transitions appearing in the vicinity of the ferroelectric phase transition. We show that positions of these maxima can be shifted by the external electric field and that the magnitude of the magneto-resistance effect depends on the mutual orientation of external electric field and polarization of the substrate. PMID:25894743

  16. Microstructure and thermo-electrical transport properties of Cd-Sn alloys

    SciTech Connect

    Ari, M. Saatci, B.; Guenduez, M.; Meydaneri, F.; Bozoklu, M.

    2008-05-15

    The thermophysical transport properties of Cd-Sn alloys have been investigated for six samples. The electrical resistivity measurements were obtained by using a standard dc four-point probe technique in the temperature range of 300 K-550 K. The resistivity of samples increases linearly with temperature and the electrical current mainly flows through the Sn phase channel. The electrical conductivity of samples is inversely proportional to temperature. Also, thermal conductivity of the Cd-Sn alloys was determined. The phonon component contribution of thermal conductivity dominates the thermal conduction processes at T < 500 K. The electronic component contribution of thermal conductivity affects the thermal transport process at T > 500 K. The thermal conductivity of the Cd-Sn alloys also depends on the grain size and grain boundary of the pure Cd and the pure Sn phases in the matrix. The temperature coefficient of resistivity was also determined, which is independent with the alloying elements.

  17. Electrical and thermal transport properties of layered Bi2YO4Cu2Se2

    NASA Astrophysics Data System (ADS)

    Xiao, Yu; Pei, Yanling; Chang, Cheng; Zhang, Xiao; Tan, Xing; Ye, Xinxin; Gong, Shengkai; Lin, Yuanhua; He, Jiaqing; Zhao, Li-Dong

    2016-07-01

    Bi2YO4Cu2Se2 possesses a low thermal conductivity and high electrical conductivity at room temperature, which was considered as a potential thermoelectric material. In this work, we have investigated the electrical and thermal transport properties of Bi2YO4Cu2Se2 system in the temperature range from 300 K to 873 K. We found that the total thermal conductivity decreases from ~1.8 W m-1 K-1 to ~0.9 W m-1 K-1, and the electrical conductivity decreases from ~850 S/cm to ~163 S/cm in the measured temperature range. To investigate how potential of Bi2YO4Cu2Se2 system, we prepared the heavily Iodine doped samples to counter-dope intrinsically high carrier concentration and improve the electrical transport properties. Interestingly, the Seebeck coefficient could be enhanced to ~+80 μV/K at 873 K, meanwhile, we found that a low thermal conductivity of ~0.7 W m-1 K-1 could be achieved. The intrinsically low thermal conductivity in this system is related to the low elastic properties, such as Young's modulus of 70-72 GPa, and Grüneisen parameters of 1.55-1.71. The low thermal conductivity makes Bi2YO4Cu2Se2 system to be a potential thermoelectric material, the ZT value ~0.06 at 873 K was obtained, a higher performance is expected by optimizing electrical transport properties through selecting suitable dopants, modifying band structures or by further reducing thermal conductivity through nanostructuring etc.

  18. Crystal Phase- and Orientation-Dependent Electrical Transport Properties of InAs Nanowires.

    PubMed

    Fu, Mengqi; Tang, Zhiqiang; Li, Xing; Ning, Zhiyuan; Pan, Dong; Zhao, Jianhua; Wei, Xianlong; Chen, Qing

    2016-04-13

    We report a systematic study on the correlation of the electrical transport properties with the crystal phase and orientation of single-crystal InAs nanowires (NWs) grown by molecular-beam epitaxy. A new method is developed to allow the same InAs NW to be used for both the electrical measurements and transmission electron microscopy characterization. We find both the crystal phase, wurtzite (WZ) or zinc-blende (ZB), and the orientation of the InAs NWs remarkably affect the electronic properties of the field-effect transistors based on these NWs, such as the threshold voltage (VT), ON-OFF ratio, subthreshold swing (SS) and effective barrier height at the off-state (ΦOFF). The SS increases while VT, ON-OFF ratio, and ΦOFF decrease one by one in the sequence of WZ ⟨0001⟩, ZB ⟨131⟩, ZB ⟨332⟩, ZB ⟨121⟩, and ZB ⟨011⟩. The WZ InAs NWs have obvious smaller field-effect mobility, conductivities, and electron concentration at VBG = 0 V than the ZB InAs NWs, while these parameters are not sensitive to the orientation of the ZB InAs NWs. We also find the diameter ranging from 12 to 33 nm shows much less effect than the crystal phase and orientation on the electrical transport properties of the InAs NWs. The good ohmic contact between InAs NWs and metal remains regardless of the variation of the crystal phase and orientation through temperature-dependent measurements. Our work deepens the understanding of the structure-dependent electrical transport properties of InAs NWs and provides a potential way to tailor the device properties by controlling the crystal phase and orientation of the NWs. PMID:27002386

  19. Temperature Dependent Electrical Transport Properties of Ni-Cr and Co-Cr Binary Alloys

    NASA Astrophysics Data System (ADS)

    Thakore, B. Y.; Suthar, P. H.; Khambholja, S. G.; Gajjar, P. N.; Bhatt, N. K.; Jani, A. R.

    2011-12-01

    The temperature dependent electrical transport properties viz. electrical resistivity and thermal conductivity of Ni10Cr90 and Co20Cr80 alloys are computed at various temperatures. The electrical resistivity has been calculated according to Faber-Ziman model combined with Ashcroft-Langreth partial structure factors. In the present work, to include the ion-electron interaction, we have used a well tested local model potential. For exchange-correlation effects, five different forms of local field correction functions due to Hartree (H), Taylor (T), Ichimaru and Utsumi (IU), Farid et al (F) and Sarkar et al (S) are used. The present results due to S function are in good agreement with the experimental data as compared to results obtained using other four functions. The S functions satisfy compressibility sum rule in long wave length limit more accurately as compared to T, IU and F functions, which may be responsible for better agreement of results, obtained using S function. Also, present result confirms the validity of present approach in determining the transport properties of alloys like Ni-Cr and Co-Cr.

  20. Temperature Dependent Electrical Transport Properties of Ni-Cr and Co-Cr Binary Alloys

    SciTech Connect

    Thakore, B. Y.; Khambholja, S. G.; Bhatt, N. K.; Jani, A. R.; Suthar, P. H.; Gajjar, P. N.

    2011-12-12

    The temperature dependent electrical transport properties viz. electrical resistivity and thermal conductivity of Ni{sub 10}Cr{sub 90} and Co{sub 20}Cr{sub 80} alloys are computed at various temperatures. The electrical resistivity has been calculated according to Faber-Ziman model combined with Ashcroft-Langreth partial structure factors. In the present work, to include the ion-electron interaction, we have used a well tested local model potential. For exchange-correlation effects, five different forms of local field correction functions due to Hartree (H), Taylor (T), Ichimaru and Utsumi (IU), Farid et al (F) and Sarkar et al (S) are used. The present results due to S function are in good agreement with the experimental data as compared to results obtained using other four functions. The S functions satisfy compressibility sum rule in long wave length limit more accurately as compared to T, IU and F functions, which may be responsible for better agreement of results, obtained using S function. Also, present result confirms the validity of present approach in determining the transport properties of alloys like Ni-Cr and Co-Cr.

  1. Investigation of electrical transport property in spinel NiCr2O4

    NASA Astrophysics Data System (ADS)

    Tripathy, S. N.; Pati, Abhipsa; Routray, K. L.; Behera, D.

    2016-05-01

    In the present work, we have discussed the electrical transport properties of the polycrystalline NiCr2O4 by employing Impedance spectroscopy and DC resistivity techniques. It was observed that charge carriers follow Arrhenius type conduction throughout the temperature range. Activation energy (Ea) has been calculated from the impedance data, 0.462 for Rgb and 0.42 from Rg, which is well buttressed by the activation energy from the DC resistivity fitted data which is 0.468 eV.

  2. Electrical transport properties of amorphous Ni32Pd53P15 alloy

    NASA Astrophysics Data System (ADS)

    Prakruti, Chaudhari; Joshi, R. H.; Bhatt, N. K.; Thakore, B. Y.

    2015-08-01

    A ternary alloy containing nickel, palladium and phosphorous in amorphous form has been studied. The electrical transport properties viz. electrical resistivity, thermoelectrical power (TEP), thermal conductivity are computed using our recently proposed potential. In the present work, five screening functions have been employed to incorporate the exchange and correlation effects. The theoretical structure factors due to hard core fluid theory have been used in the calculations. The liquid alloy is studied as a function of its composition at temperature 294 K. The partial structure factors of the compound-forming Ni32Pd53P15 ternary alloy has been calculated by considering Hoshino's m-component hard-sphere mixture, which is based on Percus-Yevic equation of Hiroike.

  3. Anomalous solute transport in saturated porous media: Relating transport model parameters to electrical and nuclear magnetic resonance properties

    NASA Astrophysics Data System (ADS)

    Swanson, Ryan D.; Binley, Andrew; Keating, Kristina; France, Samantha; Osterman, Gordon; Day-Lewis, Frederick D.; Singha, Kamini

    2015-02-01

    The advection-dispersion equation (ADE) fails to describe commonly observed non-Fickian solute transport in saturated porous media, necessitating the use of other models such as the dual-domain mass-transfer (DDMT) model. DDMT model parameters are commonly calibrated via curve fitting, providing little insight into the relation between effective parameters and physical properties of the medium. There is a clear need for material characterization techniques that can provide insight into the geometry and connectedness of pore spaces related to transport model parameters. Here, we consider proton nuclear magnetic resonance (NMR), direct-current (DC) resistivity, and complex conductivity (CC) measurements for this purpose, and assess these methods using glass beads as a control and two different samples of the zeolite clinoptilolite, a material that demonstrates non-Fickian transport due to intragranular porosity. We estimate DDMT parameters via calibration of a transport model to column-scale solute tracer tests, and compare NMR, DC resistivity, CC results, which reveal that grain size alone does not control transport properties and measured geophysical parameters; rather, volume and arrangement of the pore space play important roles. NMR cannot provide estimates of more-mobile and less-mobile pore volumes in the absence of tracer tests because these estimates depend critically on the selection of a material-dependent and flow-dependent cutoff time. Increased electrical connectedness from DC resistivity measurements are associated with greater mobile pore space determined from transport model calibration. CC was hypothesized to be related to length scales of mass transfer, but the CC response is unrelated to DDMT.

  4. Effect of morphology on the electrical transport properties of polyaniline films for electronic applications

    SciTech Connect

    Hardaker, S.S.; Eaiprasertsak, K.; Yon, J.; Gregory, R.V.; Tessema, G.X.

    1998-07-01

    Although it is well known that the oxidation state of polyaniline is an important characteristic, there are few reports of its influence on the development of morphology and electrical properties in fibers and films. In this work, differential scanning calorimetry is used in conjunction with measurements of temperature dependence of conductivity and thermoelectric power to elucidate the intimate relationship between structure and properties. By increasing the amount of chemical reduction of polyaniline solutions, films are repaired which exhibit a thermal transition between 300 and 385 C, indicative of melting. Increasing the chemical reduction also increases the conductivity of iodine doped films. The most reduced film exhibited a semiconductor transport mechanism, while the other films could be modeled with a quasi-one dimensional variable range hopping mechanism. The temperature dependence of conductivity also showed increasing order for increasing reduction, consistent with the DSC results.

  5. Self-Assembled Magnetic Metallic Nanopillars in Ceramic Matrix with Anisotropic Magnetic and Electrical Transport Properties.

    PubMed

    Su, Qing; Zhang, Wenrui; Lu, Ping; Fang, Shumin; Khatkhatay, Fauzia; Jian, Jie; Li, Leigang; Chen, Fanglin; Zhang, Xinghang; MacManus-Driscoll, Judith L; Chen, Aiping; Jia, Quanxi; Wang, Haiyan

    2016-08-10

    Ordered arrays of metallic nanopillars embedded in a ceramic matrix have recently attracted considerable interest for their multifunctionality in advanced devices. A number of hurdles need to be overcome for achieving practical devices, including selections of metal-ceramic combination, creation of tunable and ordered structure, and control of strain state. In this article, we demonstrate major advances to create such a fine nanoscale structure, i.e., epitaxial self-assembled vertically aligned metal-ceramic composite, in one-step growth using pulsed laser deposition. Tunable diameter and spacing of the nanopillars can be achieved by controlling the growth parameters such as deposition temperature. The magnetic metal-ceramic composite thin films demonstrate uniaxial anisotropic magnetic properties and enhanced coercivity compared to that of bulk metal. The system also presents unique anisotropic electrical transport properties under in-plane and out-of-plane directions. This work paves a new avenue to fabricate epitaxial metal-ceramic nanocomposites, which can simulate broader future explorations in nanocomposites with novel magnetic, optical, electrical, and catalytical properties. PMID:27438729

  6. Hole electrical transporting properties in organic-Si Schottky solar cell

    NASA Astrophysics Data System (ADS)

    Shen, Xiaojuan; Zhu, Yawen; Song, Tao; Lee, Shuit-Tong; Sun, Baoquan

    2013-07-01

    In this work we investigated the hole electrical transporting properties effect on the organic-Si hybrid Schottky solar cells. By changing the post-annealing atmosphere of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) film, the power conversion efficiencies of the Schottky Si/PEDOT:PSS cell boosted from 6.40% in air to 9.33% in nitrogen. Current-voltage, capacitance-voltage, external quantum efficiency, and transient photovoltage measurements illustrated that the enhanced power conversion efficiency of the cell was ascribed to the increase in both conductivity and work function (WP) of PEDOT:PSS film. The increased conductivity reduced the series resistance (RS) within the cell, and the higher WP generated the larger built-in potential (Vbi) which resulted in the improvement of the open-circuit voltage. In addition, the decreased RS and enlarged Vbi were beneficial for the efficient charge transport/collection, contributing to the enhancement of the fill factor. Our results indicated that the conductivity as well as the WP of the hole transporting layer played an important role in the organic-Si Schottky solar cell.

  7. Low-temperature synthesis and electrical transport properties of W 18O 49 nanowires

    NASA Astrophysics Data System (ADS)

    Shi, Songlin; Xue, Xinyu; Feng, Ping; Liu, Yonggang; Zhao, Heng; Wang, Taihong

    2008-01-01

    W 18O 49 nanowires are simply synthesized by the reaction between water vapor and tungsten powders in tube furnace at a low temperature of 600 °C. The nanowires have diameters of 20-50 nm, lengths several micrometers. XRD, TEM and SAED results show that the nanowires are of single crystalline monoclinic W 18O 49 structures with the growth direction [0 1 0]. The growth mechanism is analyzed. We investigate the temperature dependence electrical transport properties of individual W 18O 49 nanowires. The conductivity is 2.58 Ω -1 cm -1 at 290 K and 42.35 Ω -1 cm -1 at 500 K, respectively. And the electron activation energy is calculated to be about 0.26 eV.

  8. Electrical and thermal transport properties of RECu4 Au compounds, RE=Nd, Gd

    NASA Astrophysics Data System (ADS)

    Bashir, Aiman Kamal; Tchokonté, Moise Bertin Tchoula; Strydom, A. M.

    2016-09-01

    We report the electrical and thermal transport properties of NdCu4 Au and GdCu4 Au compounds, crystallizing in the cubic MgCu4 Sn - type crystal structure, with space group F 4 bar 3 m (no. 216).These properties are reported through measurements of electrical resistivity, ρ(T) , thermoelectric power, S(T) and thermal conductivity, λ(T) . ρ(T) and S(T) data indicate an antiferromagnetic (AFM)-like anomaly associated with a N e ´ el temperature TN=3.9 K and 10.9 K for NdCu4 Au and GdCu4 Au compounds, respectively. ρ(T) data for both compounds shows a sudden drop at TN. Above TN, ρ(T) results are characteristic of an electron-phonon interaction in the presence of s - d scattering. Application of magnetic field slightly suppresses TN value in GdCu4 Au compound from TN=10.9 K in a field of 0 T to 10.1 K in a field of 6 T. S(T) data at low temperatures for both compounds shows a minimum at TN. Critical analysis of S(T) in terms of the phenomenological resonance model yield the positions (Ef) and bandwidths (Wf) of the 4 f - band in both compounds: Ef=3.81(6)K, Wf=329(58) K for the Nd compound and Ef=18.2(4) K, Wf=306(5) K for the Gd compound. λ(T) for both compounds decreases linearly upon cooling from room temperature. The reduced Lorentz number L /L0 deviates from the Wiedmann-Franz at low temperature with a strong increase in L /L0 upon cooling the samples from room temperature.

  9. Anomalous electrical transport properties of polyvinyl alcohol-multiwall carbon nanotubes composites below room temperature

    NASA Astrophysics Data System (ADS)

    Chakraborty, G.; Gupta, K.; Meikap, A. K.; Babu, R.; Blau, W. J.

    2011-02-01

    The dc and ac electrical transport property of polyvinyl alcohol-multiwall carbon nanotubes composites has been investigated within a temperature range 77≤T≤300 K and in the frequency range 20 Hz-1 MHz in presence as well as in absence of a transverse magnetic field up to 1 T. The dc conductivity follows variable range hopping model. The magnetoconductivity of the samples changes a sign from positive to negative with an increase in temperature which can be interpreted by the dominancy of the quantum interference effect over the wave function shrinkage effect. The ac conductivity follows a power law whereas the temperature dependence of frequency exponent s can be explained by correlated barrier hopping model. The dielectric behavior of the samples has been governed by the grain and grain boundary resistance and capacitance. The ac conductivity reduces with the application of magnetic field. Although the theoretical model to explain it, is still lacking, we may conclude that this is due to the increase in grain and grain boundary resistance by the application of magnetic field.

  10. Electrical transport, magnetic properties of the half-metallic Fe 3O 4-based Schottky diode

    NASA Astrophysics Data System (ADS)

    Yan, Hong; Zhang, Ming; Yan, Hui

    2009-08-01

    Fe 3O 4 thin films were prepared successfully by using the rf-sputtering technique with Fe 2O 3 target. The inverse spinel structure of the film was determined by X-ray diffraction (XRD) and the single phase of the Fe 3O 4 was confirmed by the XPS measurements. The surface roughness increases with the increase of the partial pressure of hydrogen. A high saturated magnetic field, 5000 Oe, implies that there exist the antiphase boundaries (APBs) in the film. The higher coercive filed below T V is ascribed to the lower symmetry of the monoclinic structure. The temperature dependence of resistance shows a very clear Verwey transition and it is implied that the electrical transport behavior follows the variable-range hopping (VRH) mechanism from 40 to 300 K. The current vs. voltage curves of Fe 3O 4/Si Schottky heterojunction exhibits good rectifying property. The ideality factor and Schottky barrier height were obtained from the fitting curves calculated by the standard thermionic emission/diffusion model.

  11. Epitaxial growth and electrical transport properties of Cr{sub 2}GeC thin films

    SciTech Connect

    Eklund, Per; Bugnet, Matthieu; Mauchamp, Vincent; Dubois, Sylvain; Tromas, Christophe; Jaouen, Michel; Cabioc'h, Thierry; Jensen, Jens; Piraux, Luc; Gence, Loiek

    2011-08-15

    Cr{sub 2}GeC thin films were grown by magnetron sputtering from elemental targets. Phase-pure Cr{sub 2}GeC was grown directly onto Al{sub 2}O{sub 3}(0001) at temperatures of 700-800 deg. C. These films have an epitaxial component with the well-known epitaxial relationship Cr{sub 2}GeC(0001)//Al{sub 2}O{sub 3}(0001) and Cr{sub 2}GeC(1120)//Al{sub 2}O{sub 3}(1100) or Cr{sub 2}GeC(1120)//Al{sub 2}O{sub 3}(1210). There is also a large secondary grain population with (1013) orientation. Deposition onto Al{sub 2}O{sub 3}(0001) with a TiN(111) seed layer and onto MgO(111) yielded growth of globally epitaxial Cr{sub 2}GeC(0001) with a virtually negligible (1013) contribution. In contrast to the films deposited at 700-800 deg. C, the ones grown at 500-600 deg. C are polycrystalline Cr{sub 2}GeC with (1010)-dominated orientation; they also exhibit surface segregations of Ge as a consequence of fast Ge diffusion rates along the basal planes. The room-temperature resistivity of our samples is 53-66 {mu}{Omega}cm. Temperature-dependent resistivity measurements from 15-295 K show that electron-phonon coupling is important and likely anisotropic, which emphasizes that the electrical transport properties cannot be understood in terms of ground state electronic structure calculations only.

  12. Investigations of electrical transport properties of individual carbon nanotubes with nanoprober

    NASA Astrophysics Data System (ADS)

    Feng, Wei; Hayama, Kazumi; Akinaga, Hiroyuki

    2016-06-01

    We investigated and discussed quantitatively the transport properties of individual multiwalled (MW) carbon nanotubes (CNTs) by four-terminal measurement using a nanoprobing system. The homogeneity of the CNT was visibly examined using the electron beam absorbed current function of the nanoprober. The observed ohmic properties of the current–voltage characteristics and metallic transport properties of the CNTs proved that reliable contact of four probes was achieved on the outermost shell of MWCNTs. The experimental methodology was validated for the intrinsic properties of individual CNTs. Lower resistance per unit length was evaluated for thicker CNT. The measured resistance per unit length was lower than those reported by other researchers, but higher than ideally expected.

  13. Electric modulus formalism and electrical transport property of ball mill synthesized nanocrystalline Mn doped ZrO2 solid solution

    NASA Astrophysics Data System (ADS)

    Saha, S.; Nandy, A.; Meikap, A. K.; Pradhan, S. K.

    2015-12-01

    Here we report the formation of Mn doped nanocrystalline ZrO2 solid solution synthesized by high energy ball-milling method and the transport mechanism in the temperature range 298 Kelectrical study shows the dc conductivity enhances as the doping percentage increases. Complex electric modulus study shows low frequency region approaches to ideal Debye type behaviour while the high frequency side deviates. Alternating current conductivity is found to follow the power law σ'(f,T)∝fsTn. A transformation from small polaron hopping to correlated barrier hopping has been observed from the temperature dependence frequency exponent study. The contribution of grain boundary resistance is found to be dominating over the grain resistance in the ac conduction process.

  14. Electrical transport properties of individual WS2 nanotubes and their dependence on water and oxygen absorption

    NASA Astrophysics Data System (ADS)

    Zhang, Chaoying; Ning, Zhiyuan; Liu, Yang; Xu, Tingting; Guo, Yao; Zak, Alla; Zhang, Zhiyong; Wang, Sheng; Tenne, Reshef; Chen, Qing

    2012-09-01

    The electrical properties of WS2 nanotubes (NTs) were studied through measuring 59 devices. Important electrical parameters, such as the carrier concentration, mobility, and effective barrier height at the contacts, were obtained through fitting experimental non-linear I-V curves using a metal-semiconductor-metal model. The carrier mobility was found to be several orders of magnitude higher than that have been reported previously for WS2 NTs. Water absorption was found to decrease the conductivity and carrier mobility of the NTs, and could be removed when the sample was dried. Oxygen absorption also slightly decreased the conductivity of WS2 NTs.

  15. Thermodynamic and electrical transport properties of single-crystalline U2Cu4As5

    NASA Astrophysics Data System (ADS)

    Gnida, D.; Pikul, A. P.; Kaczorowski, D.

    2015-06-01

    High-quality single crystals of U2Cu4As5 were investigated by means of magnetic susceptibility, magnetization, specific heat, electrical resistivity, magnetoresistivity and Hall effect measurements, performed in wide ranges of temperature and magnetic field. The results revealed an antiferromagnetic ordering below TN = 190 K and very strong magnetocrystalline anisotropy. In the paramagnetic state, the charge transport is driven by Kondo spin-flip scattering. In the ordered region, it is governed by electron-magnon and electron-electron scattering processes with the latter ones being dominant at the lowest temperatures. The uniaxial character of the magnetic structure of U2Cu4As5 manifests itself in the temperature variations of the magnetic susceptibility and the electrical resistivity as well as in the characteristic response to the applied magnetic field.

  16. Electrical transport properties of an isolated CdS microrope composed of twisted nanowires

    NASA Astrophysics Data System (ADS)

    Yu, Gui-Feng; Yu, Miao; Pan, Wei; Han, Wen-Peng; Yan, Xu; Zhang, Jun-Cheng; Zhang, Hong-Di; Long, Yun-Ze

    2015-01-01

    CdS is one of the important II-VI group semiconductors. In this paper, the electrical transport behavior of an individual CdS microrope composed of twisted nanowires is studied. It is found that the current-voltage ( I- V) characteristics show two distinct power law regions from 360 down to 60 K. Space-charge-limited current (SCLC) theory is used to explain these temperature- and electric-field-dependent I-V curves. The I-V data can be well fitted by this theory above 100 K, and the corresponding carrier mobility, trap energy, and trap concentration are also obtained. However, the I-V data exhibit some features of the Coulomb blockade effect below 80 K.

  17. Electrical transport properties of an isolated CdS microrope composed of twisted nanowires.

    PubMed

    Yu, Gui-Feng; Yu, Miao; Pan, Wei; Han, Wen-Peng; Yan, Xu; Zhang, Jun-Cheng; Zhang, Hong-Di; Long, Yun-Ze

    2015-01-01

    CdS is one of the important II-VI group semiconductors. In this paper, the electrical transport behavior of an individual CdS microrope composed of twisted nanowires is studied. It is found that the current-voltage (I-V) characteristics show two distinct power law regions from 360 down to 60 K. Space-charge-limited current (SCLC) theory is used to explain these temperature- and electric-field-dependent I-V curves. The I-V data can be well fitted by this theory above 100 K, and the corresponding carrier mobility, trap energy, and trap concentration are also obtained. However, the I-V data exhibit some features of the Coulomb blockade effect below 80 K. PMID:25852319

  18. Solvation structure and transport properties of alkali cations in dimethyl sulfoxide under exogenous static electric fields

    SciTech Connect

    Kerisit, Sebastien; Vijayakumar, M. E-mail: karl.mueller@pnnl.gov; Han, Kee Sung; Mueller, Karl T. E-mail: karl.mueller@pnnl.gov

    2015-06-14

    A combination of molecular dynamics simulations and pulsed field gradient nuclear magnetic resonance spectroscopy is used to investigate the role of exogenous electric fields on the solvation structure and dynamics of alkali ions in dimethyl sulfoxide (DMSO) and as a function of temperature. Good agreement was obtained, for select alkali ions in the absence of an electric field, between calculated and experimentally determined diffusion coefficients normalized to that of pure DMSO. Our results indicate that temperatures of up to 400 K and external electric fields of up to 1 V nm{sup −1} have minimal effects on the solvation structure of the smaller alkali cations (Li{sup +} and Na{sup +}) due to their relatively strong ion-solvent interactions, whereas the solvation structures of the larger alkali cations (K{sup +}, Rb{sup +}, and Cs{sup +}) are significantly affected. In addition, although the DMSO exchange dynamics in the first solvation shell differ markedly for the two groups, the drift velocities and mobilities are not significantly affected by the nature of the alkali ion. Overall, although exogenous electric fields induce a drift displacement, their presence does not significantly affect the random diffusive displacement of the alkali ions in DMSO. System temperature is found to have generally a stronger influence on dynamical properties, such as the DMSO exchange dynamics and the ion mobilities, than the presence of electric fields.

  19. Optical properties and electrical transport of thin films of terbium(III) bis(phthalocyanine) on cobalt

    PubMed Central

    Robaschik, Peter; Siles, Pablo F; Bülz, Daniel; Richter, Peter; Monecke, Manuel; Fronk, Michael; Klyatskaya, Svetlana; Grimm, Daniel; Schmidt, Oliver G; Ruben, Mario; Zahn, Dietrich R T

    2014-01-01

    Summary The optical and electrical properties of terbium(III) bis(phthalocyanine) (TbPc2) films on cobalt substrates were studied using variable angle spectroscopic ellipsometry (VASE) and current sensing atomic force microscopy (cs-AFM). Thin films of TbPc2 with a thickness between 18 nm and 87 nm were prepared by organic molecular beam deposition onto a cobalt layer grown by electron beam evaporation. The molecular orientation of the molecules on the metallic film was estimated from the analysis of the spectroscopic ellipsometry data. A detailed analysis of the AFM topography shows that the TbPc2 films consist of islands which increase in size with the thickness of the organic film. Furthermore, the cs-AFM technique allows local variations of the organic film topography to be correlated with electrical transport properties. Local current mapping as well as local I–V spectroscopy shows that despite the granular structure of the films, the electrical transport is uniform through the organic films on the microscale. The AFM-based electrical measurements allow the local charge carrier mobility of the TbPc2 thin films to be quantified with nanoscale resolution. PMID:25551034

  20. Electrical Transport through Organic Molecules

    NASA Astrophysics Data System (ADS)

    Lau, C. N.; Chang, Shun-Chi; Williams, Stan

    2003-03-01

    We investigate electrical transport properties of single organic molecules using electromigration break junctions[1]. A self-assembled monolayer of various organic molecules such as 1,4-di(phenylethynyl-4'-methanethiol)benzene was grown on narrow metal wires, and single or a few molecules were incorporated into the junctions which were created by applying a large voltage and breaking the wires. The transport properties of these molecules were then measured at low temperatures. Latest experimental results will be discussed. [1] Park, J. et al, Nature, 417, 722 (2002); Liang W. et al, Nature, 417, 725 (2002).

  1. Structural and electrical transport properties of proficient Ba-Pb nanoferrites

    NASA Astrophysics Data System (ADS)

    Haq, A.; Anis-ur-Rehman, M.; Malik, Muhammad Ali

    2012-03-01

    The excellent combination of magnetic and dielectric properties of hexaferrites makes these materials suitable for use in high-frequency applications. Ba-Pb nanocrystalline ferrites having the general formula Ba1-xPbxFe12O19 (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were prepared by the co-precipitation method. X-ray powder diffraction (XRD) patterns of all prepared samples indicated the formation of the required phase. The crystallite size, lattice parameters and porosities of samples were measured from XRD data. Scanning electron microscopy was carried out to observe the morphology of the synthesized Ba-Pb ferrites. Temperature-dependent dc electrical resistivity, dielectric constant, dielectric loss tangent and the ac electrical conductivity of nanocrystalline Ba ferrites were investigated as a function of frequency and Pb concentration. The effect of Pb doping on dielectric and electric properties of Ba nanoferrites was explained on the basis of cation distribution in the crystal structure.

  2. Electrical, thermal, and species transport properties of liquid eutectic Ga-In and Ga-In-Sn from first principles

    SciTech Connect

    Yu, Seungho; Kaviany, Massoud

    2014-02-14

    Using ab initio molecular dynamics, the atomic structure and transport properties of eutectic Ga-In and Ga-In-Sn are investigated. The Kubo-Greenwood (K-G) and the Ziman-Faber (Z-F) formulations and the Wiedemann-Franz (W-F) law are used for the electrical and electronic thermal conductivity. The species diffusivity and the viscosity are also predicted using the mean square displacement and the Stokes-Einstein (S-E) relation. Alloying Ga causes more disordered structure, i.e., broadening the atomic distance near the In and Sn atoms, which reduces the transport properties and the melting temperature. The K-G treatment shows excellent agreement with the experimental results while Z-F treatment formula slightly overestimates the electrical conductivity. The predicted thermal conductivity also shows good agreement with the experiments. The species diffusivity and the viscosity are slightly reduced by the alloying of Ga with In and Sn atoms. Good agreements are found with available experimental results and new predicted transport-property results are provided.

  3. Fabrication and electrical transport properties of binary Co-Si nanostructures prepared by focused electron beam-induced deposition

    SciTech Connect

    Porrati, F.; Huth, M.; Kaempken, B.; Terfort, A.

    2013-02-07

    CoSi-C binary alloys have been fabricated by focused electron beam-induced deposition by the simultaneous use of dicobaltoctacarbonyl, Co{sub 2}(CO){sub 8}, and neopentasilane, Si{sub 5}H{sub 12}, as precursor gases. By varying the relative flux of the precursors, alloys with variable chemical composition are obtained, as shown by energy dispersive x-ray analysis. Room temperature electrical resistivity measurements strongly indicate the formation of cobalt silicide and cobalt disilicide nanoclusters embedded in a carbonaceous matrix. Temperature-dependent electrical conductivity measurements show that the transport properties are governed by electron tunneling between neighboring CoSi or CoSi{sub 2} nanoclusters. In particular, by varying the metal content of the alloy, the electrical conductivity can be finely tuned from the insulating regime into the quasi-metallic tunneling coupling regime.

  4. Electrical transport and thermochromic properties of polyaniline/chitosan/Co3O4 ternary nano composite

    NASA Astrophysics Data System (ADS)

    V, Mini; Kamath, Archana; S, Raghu; Chapi, Sharanappa; H, Devendrappa

    2015-06-01

    A new Polyaniline/ chitosan/ Co3O4 (CPAESCO) ternary nanocomposite is prepared by in situ oxidation polymerization of aniline in the presence of (NH4)2S2O8, chitosan and Co3O4. The Structural, Thermal, Optical and Electrical features of Polyaniline (PANI), Polyaniline/ chitosan (CPANI) and CPAESCO were analyzed using FT-IR, TGA, UV-vis analysis and Impedance spectroscopy by varying temperature. The results show that the introduction of the Co3O4 nanoparticles into CPANI matrix enhanced its properties. Mott's parameters show 3D -VRH Type conduction in it.

  5. Low temperature electrical transport properties in p-SnSe single crystals

    NASA Astrophysics Data System (ADS)

    Sumesh, C. K.; Patel, M.; Patel, K. D.; Solanki, G. K.; Pathak, V. M.; Srivastav, R.

    2011-01-01

    The electronic transport properties of p-type tin selenide (SnSe) grown by direct vapor transport (DVT) technique were investigated via Hall effect in the temperature range 40 < T < 300 K. The temperature dependence of conductivity revealed the existence of impurity energy level in the band gap of the crystal. The temperature dependence of the carrier concentration was analyzed using the single-donor - single-acceptor model. The Hall mobility increases by decreasing temperature up to 120 K and then decreases along with temperature. The observed temperature dependant mobility in the temperature range 120 < T < 300 K and 40 < T < 120 K was found to be limited by homopolar and ionized impurity mode scatterings respectively.

  6. Electrical Transport of Topological Insulator-bismuth selenide and Thermoelectric Properties of Graphene

    NASA Astrophysics Data System (ADS)

    Wei, Peng

    2011-12-01

    This thesis summarizes our work in the past four years in the field of transport studies of the topological insulator materials and thermoelectric properties of graphene. The first half of the thesis is focused on the transport properties of topological insulator material-Bi2Se3. In our research, we systematically tune the position of the chemical potential in p-type Ca-doped Bi2Se3 thin devices first by eliminating excess holes with controlled post-fabrication electron beam irradiation that results in an insulating bulk state. In spite of the fact that the energetic electron beam creates defects to localize the bulk carriers and inevitably to cause additional scattering, we find a tenfold increase in carrier mobility associated with the extended states in the band gap. In addition, the resistance undergoes a fivefold increase and passes the maximum as the chemical potential is further tuned by electrostatic gating. A cusp-like low-field magnetoresistance feature also emerges which is indicative of strong spin-orbit interaction. The observed gate-tunable high-mobility is a signature of massless Dirac fermions in the band gap of Bi2Se3. The second half of this thesis is focused on graphene. Our work first reported the thermoelectric study of graphene and demonstrated the anomalous thermoelectric transport of massless Dirac fermions. As a direct consequence of the linear dispersion of massless particles, we find that the Seebeck coefficient Sxx diverges with 1/n2D , where n2D is the carrier density. We observe a very large Nernst signal Sxy (˜ 50 muV/K at 8 T) at the Dirac point, and an oscillatory dependence of both Sxx and Sxy on n 2D at low temperatures. Our results underscore the anomalous thermoelectric transport in graphene, which may be used as a highly sensitive probe for impurity bands near the Dirac point.

  7. Transport Properties of Bulk Thermoelectrics An International Round-Robin Study, Part I: Seebeck Coefficient and Electrical Resistivity

    SciTech Connect

    Wang, Hsin; Porter, Wallace D; Bottner, Harold; Konig, Jan; Chen, Lidong; Bai, Shengqiang; Tritt, Terry M.; Mayolett, Alex; Senawiratne, Jayantha; Smith, Charlene; Harris, Fred; Gilbert, Partricia; Sharp, Jeff; Lo, Jason; Keinke, Holger; Kiss, Laszlo I.

    2013-01-01

    Recent research and development of high temperature thermoelectric materials has demonstrated great potential of converting automobile exhaust heat directly into electricity. Thermoelectrics based on classic bismuth telluride have also started to impact the automotive industry by enhancing air conditioning efficiency and integrated cabin climate control. In addition to engineering challenges of making reliable and efficient devices to withstand thermal and mechanical cycling, the remaining issues in thermoelectric power generation and refrigeration are mostly materials related. The figure-of-merit, ZT, still needs to improve from the current value of 1.0 - 1.5 to above 2 to be competitive to other alternative technologies. In the meantime, the thermoelectric community could greatly benefit from the development of international test standards, improved test methods and better characterization tools. Internationally, thermoelectrics have been recognized by many countries as an important area for improving energy efficiency. The International Energy Agency (IEA) group under the implementing agreement for Advanced Materials for Transportation (AMT) identified thermoelectric materials as an important area in 2009. This paper is Part I of the international round-robin testing of transport properties of bulk thermoelectrics. The main focuses in Part I are on two electronic transport properties: Seebeck coefficient and electrical resistivity.

  8. Transport Properties of Bulk Thermoelectrics—An International Round-Robin Study, Part I: Seebeck Coefficient and Electrical Resistivity

    NASA Astrophysics Data System (ADS)

    Wang, Hsin; Porter, Wallace D.; Böttner, Harald; König, Jan; Chen, Lidong; Bai, Shengqiang; Tritt, Terry M.; Mayolet, Alex; Senawiratne, Jayantha; Smith, Charlene; Harris, Fred; Gilbert, Patricia; Sharp, Jeff W.; Lo, Jason; Kleinke, Holger; Kiss, Laszlo

    2013-04-01

    Recent research and development of high-temperature thermoelectric materials has demonstrated great potential for converting automobile exhaust heat directly into electricity. Thermoelectrics based on classic bismuth telluride have also started to impact the automotive industry by enhancing air-conditioning efficiency and integrated cabin climate control. In addition to engineering challenges of making reliable and efficient devices to withstand thermal and mechanical cycling, the remaining issues in thermoelectric power generation and refrigeration are mostly materials related. The dimensionless figure of merit, ZT, still needs to be improved from the current value of 1.0 to 1.5 to above 2.0 to be competitive with other alternative technologies. In the meantime, the thermoelectric community could greatly benefit from the development of international test standards, improved test methods, and better characterization tools. Internationally, thermoelectrics have been recognized by many countries as a key component for improving energy efficiency. The International Energy Agency (IEA) group under the Implementing Agreement for Advanced Materials for Transportation (AMT) identified thermoelectric materials as an important area in 2009. This paper is part I of the international round-robin testing of transport properties of bulk thermoelectrics. The main foci in part I are the measurement of two electronic transport properties: Seebeck coefficient and electrical resistivity.

  9. Influence of Thickness on the Electrical Transport Properties of Exfoliated Bi2Te3 Ultrathin Films.

    PubMed

    Mo, D L; Wang, W B; Cai, Q

    2016-12-01

    In this work, the mechanical exfoliation method has been utilized to fabricate Bi2Te3 ultrathin films. The thickness of the ultrathin films is revealed to be several tens of nanometers. Weak antilocalization effects and Shubnikov de Haas oscillations have been observed in the magneto-transport measurements on individual films with different thickness, and the two-dimensional surface conduction plays a dominant role. The Fermi level is found to be 81 meV above the Dirac point, and the carrier mobility can reach ~6030 cm(2)/(Vs) for the 10-nm film. When the film thickness decreases from 30 to 10 nm, the Fermi level will move 8 meV far from the bulk valence band. The coefficient α in the Hikami-Larkin-Nagaoka equation is shown to be ~0.5, manifesting that only the bottom surface of the Bi2Te3 ultrathin films takes part in transport conductions. These will pave the way for understanding thoroughly the surface transport properties of topological insulators. PMID:27484860

  10. Influence of Thickness on the Electrical Transport Properties of Exfoliated Bi2Te3 Ultrathin Films

    NASA Astrophysics Data System (ADS)

    Mo, D. L.; Wang, W. B.; Cai, Q.

    2016-08-01

    In this work, the mechanical exfoliation method has been utilized to fabricate Bi2Te3 ultrathin films. The thickness of the ultrathin films is revealed to be several tens of nanometers. Weak antilocalization effects and Shubnikov de Haas oscillations have been observed in the magneto-transport measurements on individual films with different thickness, and the two-dimensional surface conduction plays a dominant role. The Fermi level is found to be 81 meV above the Dirac point, and the carrier mobility can reach ~6030 cm2/(Vs) for the 10-nm film. When the film thickness decreases from 30 to 10 nm, the Fermi level will move 8 meV far from the bulk valence band. The coefficient α in the Hikami-Larkin-Nagaoka equation is shown to be ~0.5, manifesting that only the bottom surface of the Bi2Te3 ultrathin films takes part in transport conductions. These will pave the way for understanding thoroughly the surface transport properties of topological insulators.

  11. Electrical transport properties of manganese containing pyrochlore type semiconducting oxides using impedance analyses

    SciTech Connect

    Sumi, S.; Prabhakar Rao, P.; Mahesh, S.K.; Koshy, Peter

    2012-12-15

    Graphical abstract: DC conductivity variation of CaCe{sub 1−x}Mn{sub x}SnNbO{sub 7−δ} (x = 0, 0.2, 0.4 and 0.6) with inverse of temperature. Variation of conductivity with Mn concentration at 600 °C is shown in the inset. Display Omitted Highlights: ► We have observed that the structural ordering as well as grain size increase with Mn substitution. ► Impedance analysis proved that a correlated barrier hopping type conduction mechanism is involved in the materials. ► Activation energy as well as electrical conductivity increases with increase in Mn substitution. ► Localization of electrons associated with Mn{sup 2+} and structural ordering are the key factors for the increased activation energy with Mn substitution. ► All the materials showed good NTC thermistor properties. -- Abstract: A new series of manganese containing pyrochlore type semiconducting oxides CaCe{sub 1−x}Mn{sub x}SnNbO{sub 7−δ} (x = 0, 0.2, 0.4 and 0.6) have been synthesized to study the effect of Mn substitution on the structure, microstructure and electrical properties of these samples. X-ray diffraction and scanning electron microscopy studies revealed an increase of structural ordering and grain size respectively with increase of Mn substitution. Rietveld analysis and Raman spectroscopy were also employed to corroborate the XRD results. The bulk resistance measurements with temperature exhibit negative temperature coefficient behavior. The impedance analysis of the samples revealed a non-Debye type relaxation existed in the materials. The ac conductivity variation with temperature and frequency indicates a correlated barrier hopping type conduction mechanism in these materials. The barrier height and the intersite separation for hopping influence the electrical conductivity of these samples and are found to be a function of localization of electrons associated with the Mn{sup 2+} ions and the unit cell volume respectively. The Mn substitution increases both electrical

  12. Structural, electrical and transport properties of yttrium-doped proton-conducting strontium cerates

    NASA Astrophysics Data System (ADS)

    Pasierb, P.; Wierzbicka, M.; Komornicki, S.; Rekas, M.

    Series of SrCe 1- xY xO 3- δ solid solutions with x varying between 0 and 0.2 were prepared by solid-state reaction method. XRD results revealed that samples with 0 ≤ x < 0.1 (SrCe 1- xY xO 3- δ) are homogenous perovskite phases, while the samples with higher concentration of yttrium contain admixture of other phase (identified as Sr 2CeO 4). According to SEM observations the samples were dense with uniform grain sizes within 3-5 μm. Impedance spectroscopic investigations revealed a strong influence of Y concentration on electrical properties of SrCe 1- xY xO 3- δ. The activation energies of the total electrical conductivity as well as grain boundary and bulk components have been determined. Mixed ionic-electronic conductivity in studied materials at experimental conditions has been observed. Potentiometric measurements of EMF versus temperature of solid cells containing studied materials as solid electrolytes were performed in order to determine ionic transference numbers versus temperature.

  13. Synthesis, electrical transport and optical properties of polyaniline-zirconium nanocomposite

    NASA Astrophysics Data System (ADS)

    Gupta, K.; Jana, P. C.; Meikap, A. K.

    2011-06-01

    Here, we report the synthesis of polyaniline-zirconium nanocomposite by chemical oxidative polymerization of aniline. Structural, thermal, and morphological properties of the samples are characterized by XRD, FTIR, TGA, SEM, and UV-Vis spectroscopy. Crystalline behavior of the nanocomposite has been obtained due to the presence of zirconium nanoparticles in polyaniline. FTIR analysis reveals the formation of polyaniline and changes to the structure of polyaniline due to the presence of zirconium nanoparticles. Granular morphology of the nanocomposite has been obtained from SEM micrographs and its conductivity has been increased due to the incorporation of zirconium nanoparticles. Temperature dependence of the resistivity has been fitted with ln [ρ(T)] ∝ T-1/4 which indicates three dimensional variable range hopping transport mechanism. ac conductivity follows the correlated barrier hopping transport mechanism. Some optical parameters like bandgap (Eg), peak transition energy (E0), and peak broadening parameter (C) are evaluated from real and imaginary dielectric functions. The value of the bandgap indicates the formation of a polaron lattice structure of the protonated emeraldine form of polyaniline.

  14. Electrical Transport Experiments at High Pressure

    SciTech Connect

    Weir, S

    2009-02-11

    High-pressure electrical measurements have a long history of use in the study of materials under ultra-high pressures. In recent years, electrical transport experiments have played a key role in the study of many interesting high pressure phenomena including pressure-induced superconductivity, insulator-to-metal transitions, and quantum critical behavior. High-pressure electrical transport experiments also play an important function in geophysics and the study of the Earth's interior. Besides electrical conductivity measurements, electrical transport experiments also encompass techniques for the study of the optoelectronic and thermoelectric properties of materials under high pressures. In addition, electrical transport techniques, i.e., the ability to extend electrically conductive wires from outside instrumentation into the high pressure sample chamber have been utilized to perform other types of experiments as well, such as high-pressure magnetic susceptibility and de Haas-van Alphen Fermi surface experiments. Finally, electrical transport techniques have also been utilized for delivering significant amounts of electrical power to high pressure samples, for the purpose of performing high-pressure and -temperature experiments. Thus, not only do high-pressure electrical transport experiments provide much interesting and valuable data on the physical properties of materials extreme compression, but the underlying high-pressure electrical transport techniques can be used in a number of ways to develop additional diagnostic techniques and to advance high pressure capabilities.

  15. Electric-field effect on transport and superconducting properties of YBa 2Cu 3O 7- x

    NASA Astrophysics Data System (ADS)

    Kawahara, T.; Suzuki, T.; Komai, E.; Nakazawa, K.; Terashima, T.; Bando, Y.

    1996-02-01

    Charging effects on the transport properties of thin YBa 2Cu 3O 7- x (YBCO) films are measured using FET-like junctions of YBCO in thickness ranging from 1 to 10 unit-cell thicknesses (UCT's). An electric ( E) field experiment without magnetic field reveals that the conductance is divergent at finite temperatures and changes of the Kosterlitz-Thouless transition temperature are observed as a function of applied E field. Under magnetic fields, the temperature dependence of the resistance under E fields is of Arrhenius type, and E field effects on the pinning energy of vortex are evaluated. These changes of the superconducting properties are linearly correlated to those of the normal resistance, namely, the induced areal carrier densities.

  16. Electrical and thermal transport properties of Nb- and Ru-substituted Mo3Al2C superconducting compounds

    NASA Astrophysics Data System (ADS)

    Ramachandran, B.; Jhiang, J. Y.; Kuo, Y. K.; Kuo, C. N.; Lue, C. S.

    2016-03-01

    Partial substitution effects of Nb and Ru on the superconducting and normal-state properties of Mo3Al2C-based compounds, namely Mo3-x Nb x Al2C (x = 0.00-0.25) and Mo3-x Ru x Al2C (x = 0.00-0.15), were investigated by means of electrical, magnetic, and thermoelectric studies. From the resistivity and magnetization data, we noted that the superconducting transition temperature of Mo3Al2C decreases gradually with increasing the dopant content of Nb and Ru, and the superconducting volume fraction also decreases significantly upon the substitution. The electrons dominate the thermoelectric transport in the studied compounds. Moreover, a change of curvature near 50 K in the transport properties of the parent Mo3Al2C compound was observed, prior to the superconducting transition. This is most likely due to the strong electron-phonon interaction which could have originated from the distortions near the Al sites. Finally, it was found that electronic carriers contribute considerably to heat conduction of the Mo3Al2C-based compounds near room temperature, whereas the phonons dominate the low-temperature thermal transport.

  17. The influence of hydrogen on the chemical, mechanical, optical/electronic, and electrical transport properties of amorphous hydrogenated boron carbide

    NASA Astrophysics Data System (ADS)

    Nordell, Bradley J.; Karki, Sudarshan; Nguyen, Thuong D.; Rulis, Paul; Caruso, A. N.; Purohit, Sudhaunshu S.; Li, Han; King, Sean W.; Dutta, Dhanadeep; Gidley, David; Lanford, William A.; Paquette, Michelle M.

    2015-07-01

    Because of its high electrical resistivity, low dielectric constant (κ), high thermal neutron capture cross section, and robust chemical, thermal, and mechanical properties, amorphous hydrogenated boron carbide (a-BxC:Hy) has garnered interest as a material for low-κ dielectric and solid-state neutron detection applications. Herein, we investigate the relationships between chemical structure (atomic concentration B, C, H, and O), physical/mechanical properties (density, porosity, hardness, and Young's modulus), electronic structure [band gap, Urbach energy (EU), and Tauc parameter (B1/2)], optical/dielectric properties (frequency-dependent dielectric constant), and electrical transport properties (resistivity and leakage current) through the analysis of a large series of a-BxC:Hy thin films grown by plasma-enhanced chemical vapor deposition from ortho-carborane. The resulting films exhibit a wide range of properties including H concentration from 10% to 45%, density from 0.9 to 2.3 g/cm3, Young's modulus from 10 to 340 GPa, band gap from 1.7 to 3.8 eV, Urbach energy from 0.1 to 0.7 eV, dielectric constant from 3.1 to 7.6, and electrical resistivity from 1010 to 1015 Ω cm. Hydrogen concentration is found to correlate directly with thin-film density, and both are used to map and explain the other material properties. Hardness and Young's modulus exhibit a direct power law relationship with density above ˜1.3 g/cm3 (or below ˜35% H), below which they plateau, providing evidence for a rigidity percolation threshold. An increase in band gap and decrease in dielectric constant with increasing H concentration are explained by a decrease in network connectivity as well as mass/electron density. An increase in disorder, as measured by the parameters EU and B1/2, with increasing H concentration is explained by the release of strain in the network and associated decrease in structural disorder. All of these correlations in a-BxC:Hy are found to be very similar to those

  18. Electrical transport properties of Mn-Ni-Zn ferrite using complex impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Azizar Rahman, M.; Hossain, A. K. M. Akther

    2014-02-01

    Polycrystalline Mn0.45Ni0.05Zn0.50Fe2O4 was prepared by a standard solid state reaction technique. We report the electrical properties of this ferrite using ac impedance spectroscopy as a function of frequency (20 Hz-10 MHz) at different temperatures (50-350 °C). X-ray diffraction patterns reveal the formation of cubic spinel structure. Complex impedance analysis has been used to separate the grain and grain boundary resistance of this ferrite. The variation of grain and grain boundary conductivities with temperature confirms semiconducting behavior. The dielectric permittivity shows dielectric dispersion at lower frequency and reveals that it has almost the same value on the high-frequency side. The non-coincidence of peaks corresponding to modulus and impedance indicates deviation from Debye-type relaxation. A similar value of activation energy is obtained from impedance and modulus spectra, indicating that charge carriers overcome the same energy barrier during relaxation. Electron hopping is responsible for ac conduction in this ferrite. The electron hopping shifts toward higher frequency with increasing temperature, below which the conductivity is frequency independent. The frequency-independent ac conductivity has been observed at and above 300 °C in the frequency range 20 Hz-1 MHz. This frequency-independent ac conductivity is due to the long-range movement of the mobile charge carriers.

  19. Photo-electrical and transport properties of hydrothermal ZnO

    NASA Astrophysics Data System (ADS)

    Onufrijevs, P.; Ščajev, P.; JarašiÅ«nas, K.; Medvid, A.; Korsaks, V.; Mironova-Ulmane, N.; Zubkins, M.; Mimura, H.

    2016-04-01

    We performed the studies of optical, photoelectric, and transport properties of a hydrothermal bulk n-type ZnO crystal by using the contactless optical techniques: photoluminescence, light-induced transient grating, and differential reflectivity. Optical studies revealed bound exciton and defect-related transitions between the donor states (at ˜60 meV and ˜240 meV below the conduction band) and the deep acceptor states (at 0.52 eV above the valence band). The acceptor state was ascribed to VZn, and its thermal activation energy of 0.43 eV was determined. A low value of carrier diffusion coefficient (˜0.1 cm2/s) at low excitations and temperatures up to 800 K was attributed to impact the recharged deep acceptors. Electron and hole mobilities of 140 and ˜80 cm2/Vs, correspondently, were determined at room temperature. The decrease of carrier lifetime with excitation was ascribed to increasing rate of radiative recombination at low temperatures and nonradiative recombination above the room temperature.

  20. Impact of defects on the electrical transport, optical properties and failure mechanisms of GaN nanowires.

    SciTech Connect

    Armstrong, Andrew M.; Aubry, Sylvie; Shaner, Eric Arthur; Siegal, Michael P.; Li, Qiming; Jones, Reese E.; Westover, Tyler; Wang, George T.; Zhou, Xiao Wang; Talin, Albert Alec; Bogart, Katherine Huderle Andersen; Harris, C. Thomas; Huang, Jian Yu

    2010-09-01

    We present the results of a three year LDRD project that focused on understanding the impact of defects on the electrical, optical and thermal properties of GaN-based nanowires (NWs). We describe the development and application of a host of experimental techniques to quantify and understand the physics of defects and thermal transport in GaN NWs. We also present the development of analytical models and computational studies of thermal conductivity in GaN NWs. Finally, we present an atomistic model for GaN NW electrical breakdown supported with experimental evidence. GaN-based nanowires are attractive for applications requiring compact, high-current density devices such as ultraviolet laser arrays. Understanding GaN nanowire failure at high-current density is crucial to developing nanowire (NW) devices. Nanowire device failure is likely more complex than thin film due to the prominence of surface effects and enhanced interaction among point defects. Understanding the impact of surfaces and point defects on nanowire thermal and electrical transport is the first step toward rational control and mitigation of device failure mechanisms. However, investigating defects in GaN NWs is extremely challenging because conventional defect spectroscopy techniques are unsuitable for wide-bandgap nanostructures. To understand NW breakdown, the influence of pre-existing and emergent defects during high current stress on NW properties will be investigated. Acute sensitivity of NW thermal conductivity to point-defect density is expected due to the lack of threading dislocation (TD) gettering sites, and enhanced phonon-surface scattering further inhibits thermal transport. Excess defect creation during Joule heating could further degrade thermal conductivity, producing a viscous cycle culminating in catastrophic breakdown. To investigate these issues, a unique combination of electron microscopy, scanning luminescence and photoconductivity implemented at the nanoscale will be used in

  1. Synthesis, magnetic, optical, and electrical transport properties of the nanocomposites of polyaniline with some rare earth chlorides

    NASA Astrophysics Data System (ADS)

    Gupta, K.; Chakraborty, G.; Ghatak, S.; Jana, P. C.; Meikap, A. K.; Babu, R.

    2010-10-01

    Nanocomposites of polyaniline with some rare earth chlorides like neodymium chloride, europium chloride, and dysprosium chloride were synthesized by chemical oxidative polymerization of aniline. Morphological, structural, thermal, optical, magnetic, and electrical properties of the samples were characterized by scanning electron microscope, x-ray diffractometer, Fourier transform infrared spectrometer, thermogravimetric analyzer, differentiating scanning calorimeter, optical absorption spectroscopy, room temperature magnetic susceptibility measurement, and low temperature electrical transport measurement. Nanocomposites were thermally more stable than pure polyaniline and they were more crystalline than pure polyaniline. Magnetic susceptibilities of the samples were field dependent. Three-dimensional variable range hopping charge transport mechanism was followed by the samples. The dc magnetoconductivity of the composites can be explained in terms of forward interference effect and wave function shrinkage effect. dc conductivity of Europium chloride-polyaniline composite shows a transition from forward interference model to wave function shrinkage model. Ac conductivity of the investigated samples can be explained in terms of correlated barrier hopping model. Permittivity of the sample is dominated by the grain boundary behavior in low frequency and by the grain phase in the high frequency and frequency dependence of real part of impedance is explained by Maxwell-Wagner capacitor model.

  2. Electrical properties of soils

    NASA Astrophysics Data System (ADS)

    Pozdnyakova, Larisa A.

    In this study, thorough analysis is conducted for soil electrical properties, i.e. electrical resistivity, conductivity, and potential. Soil electrical properties are the parameters of natural and artificially created electrical fields in soils and influenced by distribution of mobile electrical charges, mostly inorganic ions, In soils. Distributions of electrical charges and properties in various soil profiles were shown to be results of the soil-forming processes. Soil properties influencing the density of mobile electrical charges were found to be exponentially related with electrical resistivity and potential based on Boltzmann's law of statistical thermodynamics. Relationships were developed between electrical properties and other soil physical and chemical properties, such as texture, stone content, bulk density, water content, cation exchange capacity, salinity, humus content, and base saturation measured in-situ and in soil samples. Geophysical methods of vertical electrical sounding, four-electrode probe, non-contact electromagnetic profiling, and self-potential were modified for measuring soil electrical properties and tested in different soil studies. The proposed methods are extremely efficient, reliable, and non-disturbing. Compared with conventional methods of soil analysis, the electrical geophysical methods allowed evaluating groundwater table, salt content, depth and thickness of soil horizons, Polluted or disturbed layers in soil profiles, and stone content with an estimation error <10%. The methods provide extensive data on spatial and temporal variations in soil electrical properties, which relate to the distributions of other essential soil properties. The electrical properties were incorporated with the data from conventional soil analyses to enhance the estimation of a number of soil physical and chemical properties and to assist soil survey. The study shows various applications of the modified geophysical methods in soil physics, soil

  3. Preparation and electrical transport properties of quasi free standing bilayer graphene on SiC (0001) substrate by H intercalation

    SciTech Connect

    Yu, Cui; Liu, Qingbin; Li, Jia; Lu, Weili; He, Zezhao; Cai, Shujun; Feng, Zhihong

    2014-11-03

    We investigate the temperature dependent electrical transport properties of quasi-free standing bilayer graphene on 4H-SiC (0001) substrate. Three groups of monolayer epitaxial graphene and corresponding quasi-free standing bilayer graphene with different crystal quality and layer number homogeneity are prepared. Raman spectroscopy and atomic-force microscopy are used to obtain their morphologies and layer number, and verify the complete translation of buffer layer into graphene. The highest room temperature mobility reaches 3700 cm{sup 2}/V·s for the quasi-free standing graphene. The scattering mechanism analysis shows that poor crystal quality and layer number inhomogeneity introduce stronger interacting of SiC substrate to the graphene layer and more impurities, which limit the carrier mobility of the quasi-free standing bilayer graphene samples.

  4. Electricity as Transportation ``Fuel''

    NASA Astrophysics Data System (ADS)

    Tamor, Michael

    2013-04-01

    The personal automobile is a surprisingly efficient device, but its place in a sustainable transportation future hinges on its ability use a sustainable fuel. While electricity is widely expected to be such a ``fuel,'' the viability of electric vehicles rests on the validity of three assumptions. First, that the emissions from generation will be significantly lower than those from competing chemical fuels whether `renewable' or fossil. Second, that advances in battery technology will deliver adequate range and durability at an affordable cost. Third, that most customers will accept any functional limitations intrinsic to electrochemical energy storage. While the first two are subjects of active research and vigorous policy debate, the third is treated virtually as a given. Popular statements to the effect that ``because 70% of all daily travel is accomplished in less than 100 miles, mass deployment of 100 mile EVs will electrify 70% of all travel'' are based on collections of one-day travel reports such as the National Household Travel Survey, and so effectively ignore the complexities of individual needs. We have analyzed the day-to-day variations of individual vehicle usage in multiple regions and draw very different conclusions. Most significant is that limited EV range results in a level of inconvenience that is likely to be unacceptable to the vast majority of vehicle owners, and for those who would accept that inconvenience, battery costs must be absurdly low to achieve any economic payback. In contrast, the plug-in hybrid (PHEV) does not suffer range limitations and delivers economic payback for most users at realistic battery costs. More importantly, these findings appear to be universal in developed nations, with labor market population density being a powerful predictor of personal vehicle usage. This ``scalable city'' hypothesis may prove to a powerful predictor of the evolution of transportation in the large cities of the developing world.

  5. Electrical Transport Properties of C60 Single Crystals Doped with Alkali Metals

    NASA Astrophysics Data System (ADS)

    Ogata, Hironori; Maruyama, Yusei; Inabe, Tamotsu; Achiba, Yohji; Suzuki, Sinzo; Kikuchi, Koichi; Ikemoto, Isao

    Electronic structures of various kinds of alkali metal (Na, K, Rb or Cs)-doped C60 solids are studied by electrical resistivity and thermoelectric power measurements by using C60 single crystals prepared from a CS2 solution as a starting material. For K-or Rb-doped C60, metallic conducting behaviors in the normal conducting state and relatively sharp superconducting transitions are observed by the electrical resistivity measurements. Nearly linear-temperature dependences with the negative sign are observed in the thermoelectric power measurements at the normal conducting states for K-or Rb-doped C60. From electron diffusion term of the thermoelectric power, the values of Fermi energy and the density of states at the Fermi energy are estimated by assuming the three-dimensional free electron model, which are in substantial agreement with the results of other experiments and calculations. "Metal-semiconductor transition" is observed in both the electrical resistivity and the thermoelectric power measurements for Na-doped C60. Existence of metallic phase is confirmed by the thermoelectric power measurement in Cs-doped C60.

  6. Swift heavy ion irradiation-induced modifications in structural, magnetic and electrical transport properties of epitaxial magnetite thin films

    SciTech Connect

    Kumar, Ravi; Khan, M. Wasi; Srivastava, J. P.; Arora, S. K.; Sofin, R. G. S.; Choudhary, R. J.; Shvets, I. V.

    2006-08-01

    The effect of swift heavy ion (SHI) irradiation (190 MeV Ag) on structural, electrical transport and magnetic properties of epitaxial magnetite (Fe{sub 3}O{sub 4}) thin films (thickness {approx}70 nm) grown on MgO<100> oriented substrate have been investigated. The x-ray diffraction shows that at low fluence values up to 5x10{sup 11} ions/cm{sup 2}, the strain in the films is relaxed, whereas, at higher fluence range 1x10{sup 12}-1x10{sup 13} ions/cm{sup 2}, the epitaxial relationship with the substrate is lost along with a phase transformation from magnetite to more oxidized magnetite phase (i.e., maghemite). The Verwey transition temperature measured by electrical transport is found to increase from 109 to 117 K with the low fluence SHI irradiation, which is related to the irradiation induced strain relaxation and structural modifications. At higher fluences the system did not show Verwey transition and the resistance is also increased. The similar results were obtained by magnetization studies. The observed magnetization at 1 T field is increased at low fluence suggesting the reduction of areas with frustrated exchange interactions associated with the cationic arrangement at the anti phase boundaries. At higher fluences it decreases monotonically, indicating the emergence of other phases. The observed modifications are explained on the basis of structural strain and disorder induced by swift heavy ions, which lead to modification of the interionic Coulomb potential at octahedral sublattices and bandwidth in this system.

  7. Electrical transport properties and current density - voltage characteristic of PVA-Ag nanocomposite film

    NASA Astrophysics Data System (ADS)

    Das, A. K.; Dutta, B.; Sinha, S.; Mukherjee, A.; Basu, S.; Meikap, A. K.

    2016-05-01

    Silver (Ag) nanoparticle and Polyvinyl alcohol (PVA) - Silver (Ag) composite have been prepared and its dielectric constant, ac conductivity, and current density-voltage characteristics have been studied, at and above room temperature. Here correlated barrier hopping found to be the dominant charge transport mechanism with maximum barrier height of 0.11 eV. The sample, under ±5 V applied voltage, show back to back Schottky diode behaviour.

  8. The influence of hydrogen on the chemical, mechanical, optical/electronic, and electrical transport properties of amorphous hydrogenated boron carbide

    SciTech Connect

    Nordell, Bradley J.; Karki, Sudarshan; Nguyen, Thuong D.; Rulis, Paul; Caruso, A. N.; Paquette, Michelle M.; Purohit, Sudhaunshu S.; Li, Han; King, Sean W.; Dutta, Dhanadeep; Gidley, David; Lanford, William A.

    2015-07-21

    Because of its high electrical resistivity, low dielectric constant (κ), high thermal neutron capture cross section, and robust chemical, thermal, and mechanical properties, amorphous hydrogenated boron carbide (a-B{sub x}C:H{sub y}) has garnered interest as a material for low-κ dielectric and solid-state neutron detection applications. Herein, we investigate the relationships between chemical structure (atomic concentration B, C, H, and O), physical/mechanical properties (density, porosity, hardness, and Young's modulus), electronic structure [band gap, Urbach energy (E{sub U}), and Tauc parameter (B{sup 1/2})], optical/dielectric properties (frequency-dependent dielectric constant), and electrical transport properties (resistivity and leakage current) through the analysis of a large series of a-B{sub x}C:H{sub y} thin films grown by plasma-enhanced chemical vapor deposition from ortho-carborane. The resulting films exhibit a wide range of properties including H concentration from 10% to 45%, density from 0.9 to 2.3 g/cm{sup 3}, Young's modulus from 10 to 340 GPa, band gap from 1.7 to 3.8 eV, Urbach energy from 0.1 to 0.7 eV, dielectric constant from 3.1 to 7.6, and electrical resistivity from 10{sup 10} to 10{sup 15} Ω cm. Hydrogen concentration is found to correlate directly with thin-film density, and both are used to map and explain the other material properties. Hardness and Young's modulus exhibit a direct power law relationship with density above ∼1.3 g/cm{sup 3} (or below ∼35% H), below which they plateau, providing evidence for a rigidity percolation threshold. An increase in band gap and decrease in dielectric constant with increasing H concentration are explained by a decrease in network connectivity as well as mass/electron density. An increase in disorder, as measured by the parameters E{sub U} and B{sup 1/2}, with increasing H concentration is explained by the release of strain in the network and associated decrease in structural

  9. Surface electrical properties experiment

    USGS Publications Warehouse

    Simmons, Gene; Strangway, David; Annan, Peter; Baker, Richard G.; Bannister, Lawrence; Brown, Raymon; Cooper, William; Cubley, Dean; deBettencourt, Joseph; England, Anthony W.; Groener, John; Kong, Jin-Au; LaTorraca, Gerald; Meyer, James; Nanda, Ved; Redman, David; Rossiter, James; Tsang, Leung; Urner, Joseph; Watts, Raymond

    1973-01-01

    The surface electrical properties (SEP) experiment was used to explore the subsurface material of the Apollo 17 landing site by means of electromagnetic radiation. The experiment was designed to detect electrical layering, discrete scattering bodies, and the possible presence of water. From the analysis of the data, it was expected that values of the electrical properties (dielectric constant and loss tangent) of lunar material in situ would be obtained.

  10. Anomalous Solute Transport in Saturated Porous Media: Linking Transport Model Parameters to Electrical and Nuclear Magnetic Resonance Properties

    NASA Astrophysics Data System (ADS)

    Swanson, R. D.; Binley, A. M.; Keating, K.; France, S.; Osterman, G. K.; Day-Lewis, F. D.; Singha, K.

    2013-12-01

    The advection-dispersion equation fails to describe non-Fickian solute transport in saturated porous media, necessitating the use of other models. The dual-domain mass transfer (DDMT) model partitions the total porosity into mobile and less-mobile domains with solute exchange between the domains; consequently, the DDMT model can produce a better fit to breakthrough curves (BTCs) in systems defined by more- and less-mobile components. However, direct experimental estimation of DDMT model parameters such as rate of exchange and the mobile and less-mobile porosities remains elusive. Consequently, model parameters are often calculated purely as a model fitting exercise. There is a clear need for material characterization techniques that can offer some insight into the pore space geometrical arrangement, particularly if such techniques can be extended to the field scale. Here, we interpret static direct-current (DC) resistivity, complex resistivity (CR) and nuclear magnetic resonance (NMR) geophysical measurements in the characterization of mass transfer parameters. We use two different samples of the zeolite clinoptilolite, a material shown to demonstrate solute mass transfer due to a significant intragranular porosity, along with glass beads as a control. We explore the relation between geophysical and DDMT parameters in conjunction with supporting material characterization methods. Our results reveal how these geophysical measurements can offer some insight into the pore structures controlling the observed anomalous transport behavior.

  11. The temperature-dependent electrical transport properties of liquid Sn using pseudopotential theory

    NASA Astrophysics Data System (ADS)

    Patel, A. B.; Bhatt, N. K.; Thakore, B. Y.; Vyas, P. R.; Jani, A. R.

    2014-08-01

    We present the calculations of electrical resistivity, thermo-electric power and thermal conductivity based on the self-consistent approximation. The pseudopotential due to Hasegawa et al. [J. Non-Cryst. Solids 117/118, 300 (1990)] for full electron-ion interaction, which is valid for all electrons and contains the repulsive delta function to achieve the necessary s-pseudisation, was used in the calculation. Temperature dependence of structure factor is achieved through temperature-dependent potential parameter in the pair-potential. The outcome of the present study is discussed in the light of other such results and with predictions of Wiedemann and Franz law up to moderately high temperature. Specially, high-temperature resistivity data necessitates the careful investigation of electron energy dispersion close to the Fermi level and possible metal to non-metal transition while going from dense-fluid to low density-fluid state. In the absence of experimental data at high temperature, these findings may serve as future guideline.

  12. Electrical transport properties and interaction of heteropolyacid in N,N-dimethylformamide by dielectric spectroscopy

    SciTech Connect

    Wang, Juan; Zhao, Kongshuang; Wu, Lixin

    2014-08-07

    We present a dielectric spectroscopy study on binary electrolyte solutions composed of N,N-Dimethylformamide (DMF) and heteropolyacid (HPA). The HPA is composed of H{sup +} and Keggin polyoxometalate anion, [XW{sub 12}O{sub 40}]{sup n−}(X = P, Si, with n = 3, 4). Conductivity was used to calculate the transport parameters such as diffusion coefficient and hydrodynamic radius of polyoxometalate (POM) anions. The hydrodynamic radius of P{sub 12}W{sub 40}{sup 3−} and Si{sub 12}W{sub 40}{sup 4−} are 5.552 Å and 5.526 Å, respectively, indicating that these POM anions remain unsolvated in DMF. The temperature dependences of conductivity obeyed the Arrhenius equation, suggesting that the activation energy of proton conduction process is independent with temperature. The calculated activation energy shows that the conduction process follows Grotthuss mechanism, i.e., proton is transported by hydrogen bond between DMF molecules. One dielectric relaxation observed around 10 MHz is considered to be associated with the POM-DMFH{sup +} ion-pairs formed by POM and protonated DMF. The interaction between anion and cation in POM-DMFH{sup +} ion-pairs are explained theoretically based on the Bruggeman's mixture theories and dipole rotation model. From this, the distance between POM and DMFH{sup +} are estimated as about 1.1 nm.

  13. Conjugated polymers/semiconductor nanocrystals hybrid materials--preparation, electrical transport properties and applications.

    PubMed

    Reiss, Peter; Couderc, Elsa; De Girolamo, Julia; Pron, Adam

    2011-02-01

    This critical review discusses specific preparation and characterization methods applied to hybrid materials consisting of π-conjugated polymers (or oligomers) and semiconductor nanocrystals. These materials are of great importance in the quickly growing field of hybrid organic/inorganic electronics since they can serve as active components of photovoltaic cells, light emitting diodes, photodetectors and other devices. The electronic energy levels of the organic and inorganic components of the hybrid can be tuned individually and thin hybrid films can be processed using low cost solution based techniques. However, the interface between the hybrid components and the morphology of the hybrid directly influences the generation, separation and transport of charge carriers and those parameters are not easy to control. Therefore a large variety of different approaches for assembling the building blocks--conjugated polymers and semiconductor nanocrystals--has been developed. They range from their simple blending through various grafting procedures to methods exploiting specific non-covalent interactions between both components, induced by their tailor-made functionalization. In the first part of this review, we discuss the preparation of the building blocks (nanocrystals and polymers) and the strategies for their assembly into hybrid materials' thin films. In the second part, we focus on the charge carriers' generation and their transport within the hybrids. Finally, we summarize the performances of solar cells using conjugated polymer/semiconductor nanocrystals hybrids and give perspectives for future developments. PMID:21152569

  14. Calculations of electrical transport properties of liquid metals at high pressures

    NASA Technical Reports Server (NTRS)

    Evans, R.; Jain, A.

    1972-01-01

    It is shown how the usual nearly-free-electron model for the electrical resistivity of simple liquid metals can be extended to the case of liquid transition metals such as iron. A simple prescription is given for calculating the resistivity at different densities and temperatures. As an application and example of the method, calculations on liquid iron at different densities were carried out and the resistivity of molten iron in the earth's outer core is estimated. The effects of alloying iron with other elements are also considered. The calculated conductivity of the outer core is well within the limit required for the dynamo model of the geomagnetic field and agrees well with some recent shock wave data.

  15. Device fabrication and dc electrical transport properties of barium manganite nanofibers (BMO-NFs)

    NASA Astrophysics Data System (ADS)

    Hayat, Khizar; Javid Iqbal, M.; Rasool, Kamran; Iqbal, Yaseen

    2014-11-01

    Barium manganite nanofibers were synthesized using electrospinning technique. X-ray diffraction revealed the formation of single phase BaMnO3 nanofibers. Scanning electron microscopy revealed the formation of uniform composite and porous BaMnO3 nanofibers with an average diameter of ∼130 nm and <100 nm at 100 °C and 600 °C, respectively. Temperature dependent dc transport study of BMO-NFs device showed three distinct regions. The dominant conduction mechanism was space charge limited current with an exponential distribution of traps. The trap density was calculated to be 5.78 × 109 cm-3 using the cross-over voltage. These results provide new paradigm for developing nanofibers devices that may ultimately contribute to nanotechnology.

  16. Electrical transport properties of (BN)-rich hexagonal (BN)C semiconductor alloys

    SciTech Connect

    Uddin, M. R.; Doan, T. C.; Li, J.; Lin, J. Y.; Jiang, H. X.; Ziemer, K. S.

    2014-08-15

    The layer structured hexagonal boron nitride carbon semiconductor alloys, h-(BN)C, offer the unique abilities of bandgap engineering (from 0 for graphite to ∼6.4 eV for h-BN) and electrical conductivity control (from semi-metal for graphite to insulator for undoped h-BN) through alloying and have the potential to complement III-nitride wide bandgap semiconductors and carbon based nanostructured materials. Epilayers of (BN)-rich h-(BN){sub 1-x}(C{sub 2}){sub x} alloys were synthesized by metal-organic chemical vapor deposition (MOCVD) on (0001) sapphire substrates. Hall-effect measurements revealed that homogeneous (BN)-rich h-(BN){sub 1-x}(C{sub 2}){sub x} alloys are naturally n-type. For alloys with x = 0.032, an electron mobility of about 20 cm{sup 2}/Vs at 650 °K was measured. X-ray photoelectron spectroscopy (XPS) was used to determine the chemical composition and analyze chemical bonding states. Both composition and chemical bonding analysis confirm the formation of alloys. XPS results indicate that the carbon concentration in the alloys increases almost linearly with the flow rate of the carbon precursor (propane (C{sub 3}H{sub 8})) employed during the epilayer growth. XPS chemical bonding analysis showed that these MOCVD grown alloys possess more C-N bonds than C-B bonds, which possibly renders the undoped h-(BN){sub 1-x}(C{sub 2}){sub x} alloys n-type and corroborates the Hall-effect measurement results.

  17. Focused helium-ion beam irradiation effects on electrical transport properties of few-layer WSe2: Enabling nanoscale direct write homo-junctions

    DOE PAGESBeta

    Stanford, Michael; Noh, Joo Hyon; Koehler, Michael R.; Mandrus, David G.; Duscher, Gerd; Rondinone, Adam Justin; Ivanov, Ilia N.; Ward, Thomas Zac; Rack, Philip D.; Pudasaini, Pushpa Raj; et al

    2016-06-06

    Atomically thin transition metal dichalcogenides (TMDs) are currently receiving significant attention due to their promising opto-electronic properties. Tuning optical and electrical properties of mono and few-layer TMDs, such as tungsten diselenide (WSe2), by controlling the defects, is an intriguing opportunity to synthesize next generation two dimensional material opto-electronic devices. Here, we report the effects of focused helium ion beam irradiation on the structural, optical and electrical properties of few-layer WSe2, via high resolution scanning transmission electron microscopy, Raman spectroscopy, and electrical transport measurements. By controlling the ion irradiation dose, we selectively introduce precise defects in few-layer WSe2 thereby locally tuningmore » the resistivity and transport properties of the material. Hole transport in the few layer WSe2 is degraded more severely relative to electron transport after helium ion irradiation. Moreover, by selectively exposing material with the ion beam, we demonstrate a simple yet highly tunable method to create lateral homo-junctions in few layer WSe2 flakes, which constitutes an important advance towards two dimensional opto-electronic devices.« less

  18. Focused helium-ion beam irradiation effects on electrical transport properties of few-layer WSe2: enabling nanoscale direct write homo-junctions

    PubMed Central

    Stanford, Michael G.; Pudasaini, Pushpa Raj; Belianinov, Alex; Cross, Nicholas; Noh, Joo Hyon; Koehler, Michael R.; Mandrus, David G.; Duscher, Gerd; Rondinone, Adam J.; Ivanov, Ilia N.; Ward, T. Zac; Rack, Philip D.

    2016-01-01

    Atomically thin transition metal dichalcogenides (TMDs) are currently receiving significant attention due to their promising opto-electronic properties. Tuning optical and electrical properties of mono and few-layer TMDs, such as tungsten diselenide (WSe2), by controlling the defects, is an intriguing opportunity to synthesize next generation two dimensional material opto-electronic devices. Here, we report the effects of focused helium ion beam irradiation on the structural, optical and electrical properties of few-layer WSe2, via high resolution scanning transmission electron microscopy, Raman spectroscopy, and electrical transport measurements. By controlling the ion irradiation dose, we selectively introduce precise defects in few-layer WSe2 thereby locally tuning the resistivity and transport properties of the material. Hole transport in the few layer WSe2 is degraded more severely relative to electron transport after helium ion irradiation. Furthermore, by selectively exposing material with the ion beam, we demonstrate a simple yet highly tunable method to create lateral homo-junctions in few layer WSe2 flakes, which constitutes an important advance towards two dimensional opto-electronic devices. PMID:27263472

  19. Focused helium-ion beam irradiation effects on electrical transport properties of few-layer WSe2: enabling nanoscale direct write homo-junctions

    NASA Astrophysics Data System (ADS)

    Stanford, Michael G.; Pudasaini, Pushpa Raj; Belianinov, Alex; Cross, Nicholas; Noh, Joo Hyon; Koehler, Michael R.; Mandrus, David G.; Duscher, Gerd; Rondinone, Adam J.; Ivanov, Ilia N.; Ward, T. Zac; Rack, Philip D.

    2016-06-01

    Atomically thin transition metal dichalcogenides (TMDs) are currently receiving significant attention due to their promising opto-electronic properties. Tuning optical and electrical properties of mono and few-layer TMDs, such as tungsten diselenide (WSe2), by controlling the defects, is an intriguing opportunity to synthesize next generation two dimensional material opto-electronic devices. Here, we report the effects of focused helium ion beam irradiation on the structural, optical and electrical properties of few-layer WSe2, via high resolution scanning transmission electron microscopy, Raman spectroscopy, and electrical transport measurements. By controlling the ion irradiation dose, we selectively introduce precise defects in few-layer WSe2 thereby locally tuning the resistivity and transport properties of the material. Hole transport in the few layer WSe2 is degraded more severely relative to electron transport after helium ion irradiation. Furthermore, by selectively exposing material with the ion beam, we demonstrate a simple yet highly tunable method to create lateral homo-junctions in few layer WSe2 flakes, which constitutes an important advance towards two dimensional opto-electronic devices.

  20. Focused helium-ion beam irradiation effects on electrical transport properties of few-layer WSe2: enabling nanoscale direct write homo-junctions.

    PubMed

    Stanford, Michael G; Pudasaini, Pushpa Raj; Belianinov, Alex; Cross, Nicholas; Noh, Joo Hyon; Koehler, Michael R; Mandrus, David G; Duscher, Gerd; Rondinone, Adam J; Ivanov, Ilia N; Ward, T Zac; Rack, Philip D

    2016-01-01

    Atomically thin transition metal dichalcogenides (TMDs) are currently receiving significant attention due to their promising opto-electronic properties. Tuning optical and electrical properties of mono and few-layer TMDs, such as tungsten diselenide (WSe2), by controlling the defects, is an intriguing opportunity to synthesize next generation two dimensional material opto-electronic devices. Here, we report the effects of focused helium ion beam irradiation on the structural, optical and electrical properties of few-layer WSe2, via high resolution scanning transmission electron microscopy, Raman spectroscopy, and electrical transport measurements. By controlling the ion irradiation dose, we selectively introduce precise defects in few-layer WSe2 thereby locally tuning the resistivity and transport properties of the material. Hole transport in the few layer WSe2 is degraded more severely relative to electron transport after helium ion irradiation. Furthermore, by selectively exposing material with the ion beam, we demonstrate a simple yet highly tunable method to create lateral homo-junctions in few layer WSe2 flakes, which constitutes an important advance towards two dimensional opto-electronic devices. PMID:27263472

  1. Anisotropy of electrical and magnetic transport properties of epitaxial SrRuO{sub 3} thin films

    SciTech Connect

    Ning, X. K.; Wang, Z. J. Zhang, Z. D.

    2015-03-07

    SrRuO{sub 3} (SRO) thin films with different thickness (2–70 nm) have been grown on (001), (110), and (111) SrTiO{sub 3} substrates. The (001)-SRO films (2–8 nm) exhibited smooth flat surfaces whereas the (110)- and (111)-SRO films featured a faceted island structure. Room temperature resistivity and residual resistivity are the lowest for the (111)-SRO films (30–70 nm). Over all thicknesses, we observed enhanced magnetization in the (111)-SRO films (∼4 μ{sub B}/Ru) compared with that for the (001)- and (110)-SRO films (∼2 μ{sub B}/Ru and ∼3 μ{sub B}/Ru, respectively), suggesting a low-spin state t{sub 2g}(3↑,1↓), high-spin state t{sub 2g}(3↑)e{sub g}(1↑), and mixed low- and high-spin states for the (001)-, (111)-, and (110)-SRO films, respectively. The dependence of resistivity on temperatures near T{sub C} follows a power law with exponent β = 0.312 and β = 0.363 for the (110)- and (111)-SRO films, respectively. These critical exponents are consistent with magnetic data with scaling law M = C (T{sub C} − T){sup β}. At low temperatures, dM/dT and dρ/dT show a linear relationship in the temperature range for the Fermi liquid. These results suggest that the intrinsic electrical and magnetic transport properties are coupled.

  2. The Transport Properties of Activated Carbon Fibers

    DOE R&D Accomplishments Database

    di Vittorio, S. L.; Dresselhaus, M. S.; Endo, M.; Issi, J-P.; Piraux, L.

    1990-07-01

    The transport properties of activated isotropic pitch-based carbon fibers with surface area 1000 m{sup 2}/g have been investigated. We report preliminary results on the electrical conductivity, the magnetoresistance, the thermal conductivity and the thermopower of these fibers as a function of temperature. Comparisons are made to transport properties of other disordered carbons.

  3. The transport properties of activated carbon fibers

    SciTech Connect

    di Vittorio, S.L. . Dept. of Materials Science and Engineering); Dresselhaus, M.S. . Dept. of Electrical Engineering and Computer Science Massachusetts Inst. of Tech., Cambridge, MA . Dept. of Physics); Endo, M. . Dept. of Electrical Engineering); Issi, J-P.; Piraux, L.

    1990-07-01

    The transport properties of activated isotropic pitch-based carbon fibers with surface area 1000 m{sup 2}/g have been investigated. We report preliminary results on the electrical conductivity, the magnetoresistance, the thermal conductivity and the thermopower of these fibers as a function of temperature. Comparisons are made to transport properties of other disordered carbons. 19 refs., 4 figs.

  4. PV/solar electric transport

    SciTech Connect

    Muntwyler, U.W.; Kleindienst Muntwyler, S.

    1994-12-31

    Urs W. Muntwyler and Sigrid Kleindienst Muntwyler provide an overview of the past and future development of solar electric vehicles, and highlight the necessary changes in policy which need to take place for SEV`s to take their rightful place as one of the foremost non-polluting modes of public and private transport.

  5. Determination of the built-in electric field near contacts to polycrystalline CuInSe{sub 2}: probing local charge transport properties by photomixing

    SciTech Connect

    Tang, Yi; Sun, G.S.; Braunstein, R. von Roedern, B.

    1999-03-01

    The built-in electric field in polycrystalline CuInSe{sub 2} (CIS) near gold co-planar contacts was quantitatively revealed for the first time by the photomixing technique. A He-Ne laser beam was focused locally on the CIS sample near one of its contact. While both dc dark and photo-currents showed ohmic behavior, the high frequency ac current was non-zero for zero applied dc bias, which reveals a built-in electric field of {approximately}1000V/cm. The capability of the photomixing technique to probe local charge transport properties is expected to be very useful for, e.g., the quantitative evaluation of the quality of ohmic contacts and the investigation of electric field induced p-n junction formation in CIS and related materials. {copyright} {ital 1999 American Institute of Physics.}

  6. Determination of the built-in electric field near contacts to polycrystalline CuInSe[sub 2]: probing local charge transport properties by photomixing

    SciTech Connect

    Tang, Yi ); Sun, G.S.; Braunstein, R. ) von Roedern, B. )

    1999-03-01

    The built-in electric field in polycrystalline CuInSe[sub 2] (CIS) near gold co-planar contacts was quantitatively revealed for the first time by the photomixing technique. A He-Ne laser beam was focused locally on the CIS sample near one of its contact. While both dc dark and photo-currents showed ohmic behavior, the high frequency ac current was non-zero for zero applied dc bias, which reveals a built-in electric field of [approximately]1000V/cm. The capability of the photomixing technique to probe local charge transport properties is expected to be very useful for, e.g., the quantitative evaluation of the quality of ohmic contacts and the investigation of electric field induced p-n junction formation in CIS and related materials. [copyright] [ital 1999 American Institute of Physics.

  7. A comparable study of structural and electrical transport properties of Al and Cu nanowires using first-principle calculations

    SciTech Connect

    Gao, N.; Li, J. C. E-mail: jiangq@jlu.edu.cn; Jiang, Q. E-mail: jiangq@jlu.edu.cn

    2013-12-23

    The structural and quantum transport properties of Al and Cu nanowires with diameters up to 3.6 nm are studied using density functional theory combined with Landauer formalism. Contrary to the classical electronic behavior, the conductance of Al wires is larger than that of Cu. This is mainly attributed to the larger contribution of conductance channels from Al-3p, which is determined by the chemical nature. Meanwhile, the stronger axial contraction of Al wires plays a minor role to conductance. This makes Al wires possible candidate interconnects in integrated circuits.

  8. Theoretical investigation on local structure and transport properties of NaFsbnd AlF3 molten salts under electric field environment

    NASA Astrophysics Data System (ADS)

    Lv, Xiaojun; Xu, Zhenming; Li, Jie; Chen, Jiangan; Liu, Qingsheng

    2016-08-01

    The effect of electric field and molecular ratio CR (NaF/AlF3) on basic structure and transport properties of NaFsbnd AlF3 molten salts were investigated by molecular dynamics simulations with the Buckingham potential model. The [AlF6]3- groups are the dominant specie in NaFsbnd AlF3 molten salts at CR ≥ 2.6, and followed by the [AlF5]2- groups, while CR ≤ 2.4, [AlF5]2- groups are the protagonists up to 40%. In NaFsbnd AlF3 system, with the increase of CR, the proportion of Fb decreases slightly and the percentage of Ff increases dramatically. The Alsbnd F bonds have ionic characters as well as partial covalently characters due to the hybridization of F-2p and Al-3s, 3p orbitals. The order of ion diffusion ability follows as Na+ > F- > Al3+. Adding more NaF can break some F bridges of structure networks and decrease the polymerization degree of NaFsbnd AlF3 molten salts, the viscosity reduces and ionic conductivity increases as a consequence. The calculated results of ionic conductivity are in agreement with the experimental results. Electric field has no significant impact on the local structure characters, while transport properties are not. The change of CR (NaF/AlF3) can significantly affect these characters of both the structure and transport.

  9. Electrical transport properties study of Mo{sub 0.6}W{sub 0.4}Se{sub 2} single crystals

    SciTech Connect

    Chaki, Sunil; Deshpande, M. P.; Tailor, J. P.; Chaudhary, M. D.; Sakaria, Pallavi N.

    2012-06-05

    The mixed transition metal dichalcogenide single crystals Mo{sub 0.6}W{sub 0.4}Se{sub 2} were characterized employing EDAX (Energy Dispersive Analysis of X-ray), (XRD) X-ray diffraction, SEM (Scanning Electron Microscope) and UV-Vis-NIR spectroscopy techniques. The electrical transport properties of as-grown Mo{sub 0.6}W{sub 0.4}Se{sub 2} single crystals were studied by two probe d. c. resistivity, Hall Effect and thermoelectric power measurement set-up. The obtained results are discussed in details.

  10. Modeling Electrical Transport through Nucleic Acids

    NASA Astrophysics Data System (ADS)

    Qi, Jianqing

    Nucleic acids play a vital role in many biological systems and activities. In recent years, engineers and scientists have been interested in studying their electrical properties. The motivation for these studies stems from the following facts: (1) the bases, which form the building blocks of nucleic acids, have unique ionization potentials. Further, nucleic acids are one of the few nanomaterials that can be reproducibly manufactured with a high degree of accuracy (though admittedly their placement at desired locations remains a challenge). As a result, designed strands with specific sequences may offer unique device properties; (2) electrical methods offer potential for sequencing nucleic acids based on a single molecule; (3) electrical methods for disease detection based on the current flowing through nucleic acids are beginning to be demonstrated. While experiments in the above mentioned areas is promising, a deeper understanding of the electrical current flow through the nucleic acids needs to be developed. The modeling of current flowing in these molecules is complex because: (1) they are based on atomic scale contacts between nucleic acids and metal, which cannot be reproducibly built; (2) the conductivity of nucleic acids is easily influenced by the environment, which is constantly changing; and (3) the nucleic acids by themselves are floppy. This thesis focuses on the modeling of electrical transport through nucleic acids that are connected to two metal electrodes at nanoscale. We first develop a decoherent transport model for the double-stranded helix based on the Landauer-Buttiker framework. This model is rationalized by comparison with an experiment that measured the conductance of four different DNA strands. The developed model is then used to study the: (1) potential to make barriers and wells for quantum transport using specifically engineered sequences; (2) change in the electrical properties of a specific DNA strand with and without methylation; (3

  11. Reversible modulation of electric transport properties by oxygen absorption and releasing on Nb:SrTiO{sub 3} surface

    SciTech Connect

    Lu, H. X.; Liu, Y. B.; Chen, Y. S. Wang, J.; Shen, B. G.; Sun, J. R.

    2014-11-07

    Pt Schottky contacts on (001)-orientated Nb-doped SrTiO{sub 3} (NSTO) in both ambient air and vacuum were investigated by the conductive atomic force microscope. The co-existed TiO{sub 2} and SrO termination layers were identified on the terrace-structured NSTO surface, where the former possessed a higher forward current than the latter. In ambient air, the barrier height of Pt/NSTO Schottky junction exhibited periodical variation with cyclic terrace plane and step sites, whereas it became homogeneous in ambient vacuum. We suggested that the oxygen absorption and releasing of surface dangling bonds were the origin for reversible changes in transport properties, which indicates a feasible approach for the surface modulation and band structure tailoring of NSTO based heterojunctions.

  12. Reversible modulation of electric transport properties by oxygen absorption and releasing on Nb:SrTiO3 surface

    NASA Astrophysics Data System (ADS)

    Lu, H. X.; Liu, Y. B.; Chen, Y. S.; Wang, J.; Shen, B. G.; Sun, J. R.

    2014-11-01

    Pt Schottky contacts on (001)-orientated Nb-doped SrTiO3 (NSTO) in both ambient air and vacuum were investigated by the conductive atomic force microscope. The co-existed TiO2 and SrO termination layers were identified on the terrace-structured NSTO surface, where the former possessed a higher forward current than the latter. In ambient air, the barrier height of Pt/NSTO Schottky junction exhibited periodical variation with cyclic terrace plane and step sites, whereas it became homogeneous in ambient vacuum. We suggested that the oxygen absorption and releasing of surface dangling bonds were the origin for reversible changes in transport properties, which indicates a feasible approach for the surface modulation and band structure tailoring of NSTO based heterojunctions.

  13. Electrical transport properties of a CNT/C60/CNT hybrid junction with closed end CNT leads using Green's function method

    NASA Astrophysics Data System (ADS)

    Shokri, Aliasghar; Nikzad, Shaghayegh

    2013-01-01

    We investigate transport properties of an all-carbon molecular device consisting of a CNT/C60/CNT hybrid system with closed end (5,5) CNT leads. Two different ways of coupling are considered for C60 molecule through one and five atoms to the cap-edges of CNTs. Our calculations are based on the Green's function method in the nearest neighbor tight-binding approximation in the coherent regime. In this paper, the sensitivity of electron transport on the geometry of the CNT electrodes-C60 interface is shown. Within the framework of the Landauer-Buttiker formalism, the electrical transmission and current-voltage characteristic are calculated at room temperature. We have investigated the effect of a gate voltage on the current in the considered geometry. In the considered structure, the appearance of the conductance resonances is a manifestation of resonant states of CNT caps, which lie within the HOMO-LUMO gap.

  14. Distinct Impact of Alkali-Ion Doping on Electrical Transport Properties of Thermoelectric p-Type Polycrystalline SnSe.

    PubMed

    Wei, Tian-Ran; Tan, Gangjian; Zhang, Xiaomi; Wu, Chao-Feng; Li, Jing-Feng; Dravid, Vinayak P; Snyder, G Jeffrey; Kanatzidis, Mercouri G

    2016-07-20

    Recent findings about ultrahigh thermoelectric performance in SnSe single crystals have stimulated related research on this simple binary compound, which is focused mostly on its polycrystalline counterparts, and particularly on electrical property enhancement by effective doping. This work systematically investigated the thermoelectric properties of polycrystalline SnSe doped with three alkali metals (Li, Na, and K). It is found that Na has the best doping efficiency, leading to an increase in hole concentration from 3.2 × 10(17) to 4.4 × 10(19) cm(-3) at room temperature, accompanied by a drop in Seebeck coefficient from 480 to 142 μV/K. An equivalent single parabolic band model was found adequate to capture the variation tendency of Seebeck coefficient with doping levels within a wide range. A mixed scattering of carriers by acoustic phonons and grain boundaries is suitable for numerically understanding the temperature-dependence of carrier mobility. A maximum ZT of ∼0.8 was achieved in 1% Na- or K-doped SnSe at 800 K. Possible strategies to improve the mobility and ZT of polycrystals were also proposed. PMID:27348333

  15. Temperature-Dependent Electrical Properties and Carrier Transport Mechanisms of TMAH-Treated Ni/Au/Al2O3/GaN MIS Diode

    NASA Astrophysics Data System (ADS)

    Reddy, M. Siva Pratap; Puneetha, Peddathimula; Reddy, V. Rajagopal; Lee, Jung-Hee; Jeong, Seong-Hoon; Park, Chinho

    2016-08-01

    The temperature-dependent electrical properties and carrier transport mechanisms of tetramethylammonium hydroxide (TMAH)-treated Ni/Au/Al2O3/GaN metal-insulator-semiconductor (MIS) diodes have been investigated by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The experimental results reveal that the barrier height (I-V) increases whereas the ideality factor decreases with increasing temperature. The TMAH-treated Ni/Au/Al2O3/GaN MIS diode showed nonideal behaviors which indicate the presence of a nonuniform distribution of interface states (N SS) and effect of series resistance (R S). The obtained R S and N SS were found to decrease with increasing temperature. Furthermore, it was found that different transport mechanisms dominated in the TMAH-treated Ni/Au/Al2O3/GaN MIS diode. At 150 K to 250 K, Poole-Frenkel emission (PFE) was found to be responsible for the reverse leakage, while Schottky emission (SE) was the dominant mechanism at high electric fields in the temperature range from 300 K to 400 K. Feasible energy band diagrams and possible carrier transport mechanisms for the TMAH-treated Ni/Au/Al2O3/GaN MIS diode are discussed based on PFE and SE.

  16. A new multicomponent salt of imidazole and tetrabromoterepthalic acid: structural, optical, thermal, electrical transport properties and antibacterial activity along with Hirshfeld surface analysis.

    PubMed

    Dey, Sanjoy Kumar; Saha, Rajat; Singha, Soumen; Biswas, Susobhan; Layek, Animesh; Middya, Somnath; Ray, Partha Pratim; Bandhyopadhyay, Debasis; Kumar, Sanjay

    2015-06-01

    Herein, we report the structural, optical, thermal and electrical transport properties of a new multicomponent salt (TBTA(2-))·2(IM(+))·(water) [TBTA-IM] of tetrabromoterepthalic acid (TBTA) with imidazole (IM). The crystal structure of TBTA-IM is determined by both the single crystal and powder X-ray diffraction techniques. The structural analysis has revealed that the supramolecular charge assisted O(-)⋯HN(+) hydrogen bonding and Br⋯π interactions play the most vital role in formation of this multicomponent supramolecular assembly. The Hirshfeld surface analysis has been carried out to investigate supramolecular interactions and associated 2D fingerprint plots reveal the relative contribution of these interactions in the crystal structure quantitatively. According to theoretical analysis the HOMO-LUMO energy gap of the salt is 2.92 eV. The salt has been characterized by IR, UV-vis and photoluminescence spectroscopic studies. It shows direct optical transition with band gaps of 4.1 eV, which indicates that the salt is insulating in nature. The photoluminescence spectrum of the salt is significantly different from that of TBTA. Further, a comparative study on the antibacterial activity of the salt with respect to imidazole, Gatifloxacin and Ciprofloxacin has been performed. Moreover, the current-voltage (I-V) characteristic of ITO/TBTA-IM/Al sandwich structure exhibits good rectifying property and the electron tunneling process governs the electrical transport mechanism of the device. PMID:25748591

  17. A new multicomponent salt of imidazole and tetrabromoterepthalic acid: Structural, optical, thermal, electrical transport properties and antibacterial activity along with Hirshfeld surface analysis

    NASA Astrophysics Data System (ADS)

    Dey, Sanjoy Kumar; Saha, Rajat; Singha, Soumen; Biswas, Susobhan; Layek, Animesh; Middya, Somnath; Ray, Partha Pratim; Bandhyopadhyay, Debasis; Kumar, Sanjay

    2015-06-01

    Herein, we report the structural, optical, thermal and electrical transport properties of a new multicomponent salt (TBTA2-)·2(IM+)·(water) [TBTA-IM] of tetrabromoterepthalic acid (TBTA) with imidazole (IM). The crystal structure of TBTA-IM is determined by both the single crystal and powder X-ray diffraction techniques. The structural analysis has revealed that the supramolecular charge assisted O-⋯Hsbnd N+ hydrogen bonding and Br⋯π interactions play the most vital role in formation of this multicomponent supramolecular assembly. The Hirshfeld surface analysis has been carried out to investigate supramolecular interactions and associated 2D fingerprint plots reveal the relative contribution of these interactions in the crystal structure quantitatively. According to theoretical analysis the HOMO-LUMO energy gap of the salt is 2.92 eV. The salt has been characterized by IR, UV-vis and photoluminescence spectroscopic studies. It shows direct optical transition with band gaps of 4.1 eV, which indicates that the salt is insulating in nature. The photoluminescence spectrum of the salt is significantly different from that of TBTA. Further, a comparative study on the antibacterial activity of the salt with respect to imidazole, Gatifloxacin and Ciprofloxacin has been performed. Moreover, the current-voltage (I-V) characteristic of ITO/TBTA-IM/Al sandwich structure exhibits good rectifying property and the electron tunneling process governs the electrical transport mechanism of the device.

  18. Prediction of hydraulic and electrical transport properties of sandstone with multiscale lattice Boltzmann/finite element simulation on microtomographic images

    NASA Astrophysics Data System (ADS)

    Wong, T.; Sun, W.

    2012-12-01

    Microcomputed tomography can be used to characterize the geometry of the pore space of a sedimentary rock, with resolution that is sufficiently refined for the realistic simulation of physical properties based on the 3D image. Significant advances have been made on the characterization of pore size distribution and connectivity, development of techniques such as lattice Boltzmann method to simulate permeability, and its upscaling. Sun, Andrade and Rudnicki (2011) recently introduced a multiscale method that dynamically links these three aspects, which were often treated separately in previous computational schemes. In this study, we improve the efficiency of this multiscale method by introducing a flood-fill algorithm to determine connectivity of the pores, followed by a multiscale lattice Boltzmann/finite element calculation to obtain homogenized effective anisotropic permeability. The improved multiscale method also includes new capacity to consistently determine electrical conductivity and formation factor from CT images. Furthermore, we also introduce a level set based method that transforms pore geometry to finite element mesh and thus enables direct simulation of pore-scale flow with finite element method. When applied to the microCT data acquired by Lindquist et al. (2000) for four Fontainebleau sandstone samples with porosities ranging from 7.5% to 22%, this multiscale method has proved to be computationally efficient and our simulations has provided new insights into the relation among permeability, pore geometry and connectivity.

  19. Microscopic structure and electrical transport property of sputter-deposited amorphous indium-gallium-zinc oxide semiconductor films

    NASA Astrophysics Data System (ADS)

    Yabuta, H.; Kaji, N.; Shimada, M.; Aiba, T.; Takada, K.; Omura, H.; Mukaide, T.; Hirosawa, I.; Koganezawa, T.; Kumomi, H.

    2014-06-01

    We report on microscopic structures and electrical and optical properties of sputter-deposited amorphous indium-gallium-zinc oxide (a-IGZO) films. From electron microscopy observations and an x-ray small angle scattering analysis, it has been confirmed that the sputtered a-IGZO films consist of a columnar structure. However, krypton gas adsorption measurement revealed that boundaries of the columnar grains are not open-pores. The conductivity of the sputter-deposited a-IGZO films shows a change as large as seven orders of magnitude depending on post-annealing atmosphere; it is increased by N2-annealing and decreased by O2-annealing reversibly, at a temperature as low as 300°C. This large variation in conductivity is attributed to thermionic emission of carrier electrons through potential barriers at the grain boundaries, because temperature dependences of the carrier density and the Hall mobility exhibit thermal activation behaviours. The optical band-gap energy of the a-IGZO films changes between before and after annealing, but is independent of the annealing atmosphere, in contrast to the noticeable dependence of conductivity described above. For exploring other possibilities of a-IGZO, we formed multilayer films with an artificial periodic lattice structure consisting of amorphous InO, GaO, and ZnO layers, as an imitation of the layer-structured InGaZnO4 homologous phase. The hall mobility of the multilayer films was almost constant for thicknesses of the constituent layer between 1 and 6 Å, suggesting rather small contribution of lateral two-dimensional conduction It increased with increasing the thickness in the range from 6 to 15 Å, perhaps owing to an enhancement of two-dimensional conduction in InO layers.

  20. ELECTRICAL PROPERTIES OF FOODS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Foods, especially liquid foods, conduct electricity. Unlike in metals, the charge carriers in foods are ions, instead of electrons. Under normal applications, ions carry the charges as the mass of ions moves along the electrical field. The concentration and mobility of ions determine the electrical ...

  1. Ultra-violet absorption induced modifications in bulk and nanoscale electrical transport properties of Al-doped ZnO thin films

    SciTech Connect

    Kumar, Mohit; Basu, Tanmoy; Som, Tapobrata

    2015-08-07

    Using conductive atomic force microscopy and Kelvin probe force microscopy, we study local electrical transport properties in aluminum-doped zinc oxide (ZnO:Al or AZO) thin films. Current mapping shows a spatial variation in conductivity which corroborates well with the local mapping of donor concentration (∼10{sup 20 }cm{sup −3}). In addition, a strong enhancement in the local current at grains is observed after exposing the film to ultra-violet (UV) light which is attributed to persistent photocurrent. Further, it is shown that UV absorption gives a smooth conduction in AZO film which in turn gives rise to an improvement in the bulk photoresponsivity of an n-AZO/p-Si heterojunction diode. This finding is in contrast to the belief that UV absorption in an AZO layer leads to an optical loss for the underneath absorbing layer of a heterojunction solar cell.

  2. Electric field manipulation of magnetic and transport properties in SrRuO3/Pb(Mg1/3Nb2/3)O3-PbTiO3 heterostructure

    PubMed Central

    Zhou, W. P.; Li, Q.; Xiong, Y. Q.; Zhang, Q. M.; Wang, D. H.; Cao, Q. Q.; Lv, L. Y.; Du, Y. W.

    2014-01-01

    The electric field manipulation of magnetic properties is currently of great interest for the opportunities provided in low-energy-consuming spintronics devices. Here, we report the effect of electric field on magnetic and transport properties of the ferromagnetic SrRuO3 film which is epitaxially grown on Pb(Mg1/3Nb2/3)O3-PbTiO3 ferroelectric substrate. With the application of electric field on the substrate, the magnetization, Curie temperature and resistivity of SrRuO3 are effectively modified. The mechanism of the electric field manipulation of these properties is ascribed to the rotations of RuO6 oxygen octahedra caused by the electric-field-induced strain, which changes the overlap and hybridization between the Ru 4d orbitals and O 2p orbitals, resulting in the modification of the magnetic and electronic properties. PMID:25384967

  3. Effective Transport Properties

    NASA Astrophysics Data System (ADS)

    Mauri, Roberto

    In this chapter we study a particular case of multiphase systems, namely two-phase materials in which one of the phases is randomly dispersed in the other, so that the composite can be viewed on a macroscale as an effective continuum, with well defined properties. In general, the theoretical determination of the parameter for an effective medium requires, as a rule, the solution of a corresponding transport problem at the microscale, which takes into account the morphology of the system and its evolution. As the mathematical problem is well-posed on a microscale, this can be accomplished using, for example, the multiple scale approach shown in Chap. 11 ; however, the task requires massive computations and is therefore difficult to implement from the practical standpoint. Here, instead, we focus on a deterministic approach to the problem, where the geometry and spatial configuration of the particles comprising the included phase are given and the solution to the microscale problem is therefore sought analytically. As examples, we study the effective thermal conductivity of solid reinforced materials (Sect. 10.1), the effective viscosity of non-colloidal suspensions (Sect. 10.2), the effective permeability of porous materials (10.3) and the effective self- and gradient diffusivities of colloidal suspensions (Sect. 10.4). Then, in Sect. 10.5, an alternative dynamic definition of the transport coefficients is considered, which can also serve as a basis to determine the effective properties of complex systems.

  4. Structure, Electrical Transport and Magneto-Resistance Properties of La5/8Ca3/8MnO3 Manganite Synthesized with Different Manganese Precursors

    NASA Astrophysics Data System (ADS)

    Navasery, M.; Halim, S. A.; Lim, K. P.; Chen, S. K.; Roslan, A. S.; Abd-Shukor, R.

    We synthesized the polycrystalline manganite of La5/8Ca3/8MnO3 with three different manganese routes prepared through a solid state reaction method. The effects of the manganese route selection on the structure, electrical transport and magneto-transport properties were examined in this study. The samples were characterized using X-ray diffraction (XRD) and SEM to identify their structure and morphology. XRD analysis confirmed that all samples were in single phase with orthorhombic structure and belonged to the Pnma space group. The average grain sized samples with manganese route of Mn2O3 and MnCO3 had a grain size of 1.2-8.7 μm and 2-7.5 μm, respectively. For the MnO2 route, the sample had a small melt-like shape with higher porosity. The metal-insulator transition temperature, TMI, for LCMO (Mn2O3), LCMO (MnO2) and LCMO (MnCO3) samples were 270 K, 266 K and 258 K, respectively. All the samples showed negative magneto-resistance with significant increase in value near the TMI temperature. The highest CMR (colossal magneto-resistance) ratio was found in LCMO (Mn2O3), -22.06% at 270 K, followed by -16.69% for LCMO (MnO2) at 80 K, and 15.2% for LCMO (MnCO3) at 100 K in a 1 T magnetic field.

  5. Electric field control of magnetic properties and electron transport in BaTiO₃-based multiferroic heterostructures.

    PubMed

    Asa, M; Baldrati, L; Rinaldi, C; Bertoli, S; Radaelli, G; Cantoni, M; Bertacco, R

    2015-12-23

    In this paper, we report on a purely electric mechanism for achieving the electric control of the interfacial spin polarization and magnetoresistance in multiferroic tunneling junctions. We investigate micrometric devices based on the Co/Fe/BaTiO3/La0.7Sr0.3MnO3 heterostructure, where Co/Fe and La0.7Sr0.3MnO3 are the magnetic electrodes and BaTiO3 acts both as a ferroelectric element and tunneling barrier. We show that, at 20 K, devices with a 2 nm thick BaTiO3 barrier present both tunneling electroresistance (TER = 12   ±   0.1%) and tunneling magnetoresistance (TMR). The latter depends on the direction of the BaTiO3 polarization, displaying a sizable change of the TMR from  -0.32   ±   0.05% for the polarization pointing towards Fe, to  -0.12   ±   0.05% for the opposite direction. This is consistent with the on-off switching of the Fe magnetization at the Fe/BaTiO3 interface, driven by the BaTiO3 polarization, we have previously demonstrated in x-ray magnetic circular dichroism experiments. PMID:26613190

  6. Tuning the band structure, magnetic and transport properties of the zigzag graphene nanoribbons/hexagonal boron nitride heterostructures by transverse electric field.

    PubMed

    Ilyasov, V V; Meshi, B C; Nguyen, V C; Ershov, I V; Nguyen, D C

    2014-07-01

    The paper presents the results of ab initio study of the opportunities for tuning the band structure, magnetic and transport properties of zigzag graphene nanoribbon (8-ZGNR) on hexagonal boron nitride (h-BN(0001)) semiconductor heterostructure by transverse electric field (E(ext)). This study was performed within the framework of the density functional theory (DFT) using Grimme's (DFT-D2) scheme. We established the critical values of E(ext) for the 8-ZGNR/h-BN(0001) heterostructure, thereby providing for semiconductor-halfmetal transition in one of electron spin configurations. This study also showed that the degeneration in energy of the localized edge states is removed when E(ext) is applied. In ZGNR/h-BN (0001) heterostructure, value of the splitting energy was higher than one in ZGNRs without substrate. We determined the effect of low E(ext) applied to the 8-ZGNR/h-BN (0001) semiconductor heterostructure on the preserved local magnetic moment (LMM) (0.3μ(B)) of edge carbon atoms. The transport properties of the 8-ZGNR/h-BN(0001) semiconductor heterostructure can be controlled using E(ext). In particular, at a critical value of the positive potential, the electron mobility can increase to 7× 10(5) cm(2)/V s or remain at zero in the spin-up and spin-down electron subsystems, respectively. We established that magnetic moments (MMs), band gaps, and carrier mobility can be altered using E(ext). These abilities enable the use of 8-ZGNR/h-BN(0001) semiconductor heterostructure in spintronics. PMID:25005304

  7. Tuning the band structure, magnetic and transport properties of the zigzag graphene nanoribbons/hexagonal boron nitride heterostructures by transverse electric field

    SciTech Connect

    Ilyasov, V. V. E-mail: chuongnguyen11@gmail.com; Meshi, B. C.; Nguyen, V. C. E-mail: chuongnguyen11@gmail.com; Ershov, I. V.; Nguyen, D. C.

    2014-07-07

    The paper presents the results of ab initio study of the opportunities for tuning the band structure, magnetic and transport properties of zigzag graphene nanoribbon (8-ZGNR) on hexagonal boron nitride (h-BN(0001)) semiconductor heterostructure by transverse electric field (E{sub ext}). This study was performed within the framework of the density functional theory (DFT) using Grimme's (DFT-D2) scheme. We established the critical values of E{sub ext} for the 8-ZGNR/h-BN(0001) heterostructure, thereby providing for semiconductor-halfmetal transition in one of electron spin configurations. This study also showed that the degeneration in energy of the localized edge states is removed when E{sub ext} is applied. In ZGNR/h-BN (0001) heterostructure, value of the splitting energy was higher than one in ZGNRs without substrate. We determined the effect of low E{sub ext} applied to the 8-ZGNR/h-BN (0001) semiconductor heterostructure on the preserved local magnetic moment (LMM) (0.3μ{sub B}) of edge carbon atoms. The transport properties of the 8-ZGNR/h-BN(0001) semiconductor heterostructure can be controlled using E{sub ext}. In particular, at a critical value of the positive potential, the electron mobility can increase to 7× 10{sup 5} cm{sup 2}/V s or remain at zero in the spin-up and spin-down electron subsystems, respectively. We established that magnetic moments (MMs), band gaps, and carrier mobility can be altered using E{sub ext}. These abilities enable the use of 8-ZGNR/h-BN(0001) semiconductor heterostructure in spintronics.

  8. Electrical transport properties of dense bulk YBa 2Cu 4O 8 produced by hot isostatic pressing

    NASA Astrophysics Data System (ADS)

    Andersson, B. M.; Sundqvist, B.; Niska, J.; Loberg, B.; Easterling, K.

    1990-10-01

    Highly dense sintered YBa 2Cu 4O 8 has been produced by hot isostatic pressing (HIP). The electrical resistivity ϱ of this material has been measured as a function of temperature T and pressure ϱ in the range 40-650 K and 0-0.7 GPa. Both the temperature dependence and the pressure dependence of ϱ are found to be well described by a model based on the standard Bloch-Grüneisen theory. It is pointed out that ϱ is liner in T only under isobaric conditions, while ϱ is strongly nonlinear in all high- Tc superconductors under isochoric (constant volume) conditions. The critical current density of the material is 900 A/cm 2 at 4 K, while the resistivity is 630 μΩ cm at 294 K.

  9. Electrical transport properties of ReS2 with polymer electrolyte gating in the high-doping limit

    NASA Astrophysics Data System (ADS)

    Ovchinnikov, Dmitry; Allain, Adrien; Pasquier, Diego; Dumcenco, Dumitru; Ho, Ching-Hwa; Huang, Ying-Sheng; Yazyev, Oleg; Kis, Andras

    Two-dimensional (2D) materials have emerged as promising candidates for future electronic applications. Among them, transition metal dichalcogenides (TMDs) demonstrate not only potential as ultrathin transistor channel material, but also intriguing spin and valley physics, which in principle could allow new types of devices and circuits. Here we report on the first study of two-dimensional anisotropic ReS2 at high doping levels, enabled by polymer electrolyte gating. Significantly increasing the doping level using electrolyte instead of standard solid gate, we measured an unusual modulation of the conductivity at high carrier densities in monolayer ReS2. In the case of thicker flakes, the effect is milder and an insulator-metal-insulator sequence with increasing doping is observed. Transport measurements provide the evidence of major influence of ionic disorder. Furthermore, we discuss possible band structure effects.

  10. Electrical transport and mechanical properties of alkylsilane self-assembled monolayers on silicon surfaces probed by atomic force microscopy

    SciTech Connect

    Park, Jeong Young; Qi, Yabing; Ashby, Paul D.; Hendriksen, Bas L.M.; Salmeron, Miquel

    2009-02-06

    The correlation between molecular conductivity and mechanical properties (molecular deformation and frictional responses) of hexadecylsilane self-assembled monolayers was studied with conductive probe atomic force microscopy/friction force microscopy in ultrahigh vacuum. Current and friction were measured as a function of applied pressure, simultaneously, while imaging the topography of self-assembled monolayer molecule islands and silicon surfaces covered with a thin oxide layer. Friction images reveal lower friction over the molecules forming islands than over the bare silicon surface, indicating the lubricating functionality of alkylsilane molecules. By measuring the tunneling current change due to changing of the height of the molecular islands by tilting the molecules under pressure from the tip, we obtained an effective conductance decay constant ({beta}) of 0.52/{angstrom}.

  11. Large-scale synthesis and electrical transport properties of single-crystalline SmB6 nanowires

    NASA Astrophysics Data System (ADS)

    Zhou, Yong; Peng, Yuehua; Yin, Yanling; Zhou, Weichang; Zhou, Fang; Liu, Chang; Liu, Guangtong; Sun, Lianfeng; Tang, Dongsheng

    2016-07-01

    Topological Kondo insulator samarium hexaboride (SmB6) nanowires, with diameters of 60–150 nm and lengths up to 1–5 μm, were successfully synthesized in large scale by chemical vapor deposition using BCl3 and SmCl3 as precursors at 1070 °C. Transmission electron microscopy observation and selected area electron diffraction analysis indicate that SmB6 nanowires are single-crystalline and grow in a preferred direction of [1 0 0]. It also indicates that the growth of SmB6 nanowires might be governed by a vapor–solid mechanism. Conventional four-terminal resistance measurements show that the resistance of an SmB6 nanowire increases with decreasing temperature, but saturates at temperatures less than 10 K, which might be attributed to a true topological insulator with a metallic surface and fully insulating bulk states. Resistance measurements also indicate that the contribution of surface states to conductance in the SmB6 nanowire is enhanced remarkably; therefore the high-quality single-crystalline SmB6 nanowires with large surface-to-bulk ratio might be the best candidate for investigating the topological properties of this material.

  12. Cation stoichiometry and electrical transport properties of the NdGaO3/(0 0 1)SrTiO3 interface

    NASA Astrophysics Data System (ADS)

    Kalabukhov, A.; Boikov, Yu A.; Serenkov, I. T.; Sakharov, V. I.; Claeson, T.; Winkler, D.

    2015-06-01

    The interface formed between two wide band-gap insulators, NdGaO3 and SrTiO3 renders metallic behavior, similar to the LaAlO3/SrTiO3 interface. The interface conductivity depends strongly upon oxygen pressure during growth of the NdGaO3 film and subsequent annealing in oxygen. The conductivity of a (10 uc) NdGaO3/SrTiO3 film, pulsed laser deposited at low (pO2 = 10-4 mbar) oxygen pressure, vanishes after annealing at 600 °C in oxygen atmosphere. For a similar interface formed at high oxygen pressure (pO2 = 0.3 mbar), the metallic conductivity remains also after post annealing. Medium energy ion spectroscopy (MEIS) in random (non-channeling) direction showed that a substantial part of Ga is missing in films deposited at low pressure, while optimal stoichiometry is approached in films deposited at high pressure. Aligned (channeling) MEIS likewise show that the Ga/Nd ratio approaches the stoichiometric value as the pressure is increased from 10-4 to 0.3 mbar. This is interpreted as due to gallium desorption from a growing film at high temperature and low oxygen pressure while the re-evaporation of gallium is considerably suppressed at higher pressure. We discuss the possible role of stoichiometry on electrical transport properties.

  13. STM study of electrical transport properties of one dimensional contacts between MnSi(~1.7) nanowires and Si(111) and (110) substrates.

    PubMed

    Liu, Xiao-Yong; Zou, Zhi-Qiang

    2015-05-15

    We demonstrate the formation of contact barriers at the interfaces between MnSi1.7 nanowires (NWs) and Si substrates by the current-voltage (I-V) curves measured by scanning tunneling microscope with the tip contacting the NWs. The NWs on Si(110) exhibit linear reverse bias I-V curves, which suggests a parallel Ohmic surface state conductance of the Si(110) surface. The NWs on Si(111) exhibit nonlinear reverse bias I-V behavior, which indicates a considerable amount of minority carrier recombination-generation current. The NW length-dependence study of the forward bias current clearly shows that the quantitative change in NW length leads to a qualitative change in electrical transport properties. We derive a characteristic length LC ≈ 200 nm and the corresponding aspect ratio of ∼12-18 for MnSi1.7 NWs according to the variation of current density with the NW length. PMID:25900852

  14. Computing Thermodynamic And Transport Properties

    NASA Technical Reports Server (NTRS)

    Mcbride, B.; Gordon, Sanford

    1993-01-01

    CET89 calculates compositions in chemical equilibrium and properties of mixtures of any chemical system for which thermodynamic data available. Provides following options: obtains chemical-equilibrium compositions and corresponding thermodynamic mixture properties for assigned thermodynamic states; calculates dilute-gas transport properties of complex chemical mixtures; obtains Chapman-Jouguet detonation properties for gaseous mixtures; calculates properties of incident and reflected shocks in terms of assigned velocities; and calculates theoretical performance of rocket for both equilibrium and frozen compositions during expansion. Rocket performance based on optional models of finite or infinite area combustor.

  15. Electrical properties of diamond nanostructures

    NASA Astrophysics Data System (ADS)

    Bevilacqua, M.

    Nanocrystalline diamond films (NCD) can potentially be used in a large variety of applications such as electrochemical electrodes, tribology, cold cathodes, and corrosion resistance. A thorough knowledge of the electrical properties of NCD films is therefore critical to understand and predict their performance in various applications. In the present work the electrical properties of NCD films were analysed using Impedance Spectroscopy and Hall Effect measurements. Impedance Spectroscopy permits to identify and single out the conduction paths within the films tested. Such conduction paths can be through grain interiors and/or grain boundaries. Hall measurements, carried out on Boron doped NCD, permits determination of the mobility of the films. Specific treatments were devised to enhance the properties of the NCD films studied. Detonation nanodiamond (DND) is becoming an increasingly interesting material. It is already used as abrasive material or component for coatings [1], but its potential applications can extend far beyond these. It is therefore essential to understand the structure and electrical properties of DND in order to exploit the full potential of this material. In the present work, electrical properties of DND were studied using Impedance Spectroscopy. The results obtained suggest that DND could be used to manufacture devices able to work as Ammonia detectors. Another major area of study in this work was ultra-violet diamond photodetectors. Using high quality CVD single-crystal diamond, UV photodetection devices were built using standard lithographic techniques. Following the application of heat treatments, the photoconductive properties of these devices were highly enhanced. The devices represent the state-of-the-art UV diamond photodetectors.

  16. Electrical Properties of Hydrous Magmas

    NASA Astrophysics Data System (ADS)

    Laumonier, M.; Sifre, D.; Gaillard, F.

    2013-12-01

    Volatiles strongly affect physical and chemical properties of magmas which are major vectors of mass and heat transfer in the Earth's. In subduction zones, hydrated melts prevail during the entire course of differentiation from basalts, andesites, dacites to rhyolites. Several electrical surveys obtained by magneto telluric investigations are currently deployed at subduction zones. The electrical conductivity of hydrous melts is however poorly constrained: so far only three studies have experimentally addressed this topic. Here, we show in situ electrical impedance of natural dacites, andesites (from Uturuncu Volcano, Bolivia) and basaltic magmas obtained with a 4-wire set up in a piston cylinder and internally heated pressure vessel. The range of temperature (500 to 1300°C), pressure (0.3 to 2 Gpa), and the various water contents and crystal fractions covers the respective ranges occurring at natural conditions. First results show that the conductivity increases with the temperature, the melt fraction, and a slightly decreases with the pressure and the crystal fraction. The compilation of these results with previous studies (rhyolitic, phonolitic and basaltic compositions) will lead to a general model of the electrical properties of magmas. Such a model will help in (i) interpreting the electrical signature of natural magmas and (ii) constraining their conditions (chemical composition, temperature, pressure, water content, melt fraction) from the source to the storage location.

  17. Transport properties of uranium dioxide

    SciTech Connect

    Fink, J.K.; Chasanov, M.G.; Leibowitz, L.

    1981-04-01

    In order to provide reliable and consistent data on the thermophysical properties of reactor materials for reactor safety studies, this revision is prepared for the transport properties of the uranium dioxide portion of the fuel property section of the report Properties for LMFBR Safety Analysis. Since the original report was issued in 1976, measurements of thermal diffusivity and emissivity have been made. In addition to incorporating this new data, new equations have been derived to fit the thermal diffusivity and thermal conductivity data. This analysis is consistent with the analysis of enthalpy and heat capacity. A new form of equation for the emissivity is also given. The present report comprises the transport part of the UO/sub 2/ portion of section A of the planned complete revision of Properties for LMFBR Safety Analysis.

  18. Nanostructured Carbons and Their Electrical Transport Characteristics

    NASA Astrophysics Data System (ADS)

    Shi, Wu

    This thesis is about the fabrication, characterization, device preparation and electrical transport properties measurements of three types of nanostructured carbons. In particular, the foci are on the 4 Angstrom carbon nanotubes embedded in zeolite crystals, bundles of double-wall carbon nanotubes, and disordered graphene. The 4 Angstrom single-wall carbon nanotubes (SWCNTs) embedded in zeolite crystals are fabricated by a new heating process which introduces ethylene gas as the carbon source. Raman characterization indicates the sample quality to be improved compared to that fabricated by the original heating process that involved converting the precursor tripropylamine. Transport measurements carried out on these newly fabricated 4 Angstrom SWCNT samples show two types of superconducting resistive transitions. The first type is one-dimensional (1D) crossover to three-dimensional (3D) superconducting transition, which was observed to initiate at 15 K, followed by a sharp, order of magnitude resistance drop at 7.5 K. The sharp transition exhibits anisotropic magnetic field dependence. And differential resistance versus current curves indicate that the establishment of coherence proceeded in stages as the temperature is lowered below 15K. In particular, the sharp resistance drop and its attendant nonlinear IV characteristics are consistent with the manifestations of a Berezinskii-Kosterlitz-Thouless (BKT) transition that establishes a quasi-long range order in the plane transverse to the c-axis of the nanotubes. The second type is quasi 1D superconducting transition, which was also observed to initiate at 15 K. But the resistance drop exhibits a smooth feature and magnetic field independence up to 11 Tesla as temperature decreases. And differential resistance increases smoothly with bias current. Specific heat and new Meissner effect measurements carried out by Prof. Rolf Lortz's group provide strong support of the superconductivity in 4 Angstrom CNTs, with detailed

  19. Transport properties in the atmosphere of Jupiter

    NASA Technical Reports Server (NTRS)

    Biolsi, L., Jr.

    1979-01-01

    The computer program used to obtain transport properties for the Hulburt-Hirschfelder potential was tested. Transport properties for the C-C interaction were calculated. Rough estimates for transport properties for the important ablation species were obtained as well as estimates of transport properties for some of the species associated with photochemical smog. The results are discussed.

  20. Thermal and Electrical Transport in Oxide Heterostructures

    NASA Astrophysics Data System (ADS)

    Ravichandran, Jayakanth

    This dissertation presents a study of thermal and electrical transport phenomena in heterostructures of transition metal oxides, with specific interest in understanding and tailoring thermoelectricity in these systems. Thermoelectric energy conversion is a promising method for waste heat recovery and the efficiency of such an engine is directly related to a material dependent figure of merit, Z, given as S2sigma/kappa, where S is thermopower and sigma and kappa are electrical and thermal conductivity respectively. Achieving large figure of merit has been hampered by the coupling between these three thermoelectric coefficients, and the primary aim of this study is to understand the nature of thermoelectricity in complex oxides and identify mechanisms which can allow tuning of one or more thermoelectric coefficients in a favorable manner. Unlike the heavily studied conventional thermoelectric semiconductors, transition metals based complex oxides show conduction band characteristics dominated by d-bands, with much larger effective masses and varying degrees of electron correlations. These systems provide for exotic thermoelectric effects which are typically not explained by conventional theories and hence provide an ideal platform for exploring the limits of thermoelectricity. Meanwhile, oxides are composed of earth abundant elements and have excellent high temperature stability, thus providing compelling technological possibilities for thermoelectrics based power generation. In this dissertation, we address specific aspects of thermoelectricity in model complex oxide systems such as perovskite titanates and layered cobaltates to understand thermal and thermoelectric behavior and explore the tunability of thermoelectricity in these systems. The demonstration of band engineering as a viable method to tune physical properties of materials is explored. The model system used for this case is strontium titanate, where two dopants such as La on the Sr-site and oxygen

  1. Transport Properties for Combustion Modeling

    SciTech Connect

    Brown, N.J.; Bastein, L.; Price, P.N.

    2010-02-19

    This review examines current approximations and approaches that underlie the evaluation of transport properties for combustion modeling applications. Discussed in the review are: the intermolecular potential and its descriptive molecular parameters; various approaches to evaluating collision integrals; supporting data required for the evaluation of transport properties; commonly used computer programs for predicting transport properties; the quality of experimental measurements and their importance for validating or rejecting approximations to property estimation; the interpretation of corresponding states; combination rules that yield pair molecular potential parameters for unlike species from like species parameters; and mixture approximations. The insensitivity of transport properties to intermolecular forces is noted, especially the non-uniqueness of the supporting potential parameters. Viscosity experiments of pure substances and binary mixtures measured post 1970 are used to evaluate a number of approximations; the intermediate temperature range 1 < T* < 10, where T* is kT/{var_epsilon}, is emphasized since this is where rich data sets are available. When suitable potential parameters are used, errors in transport property predictions for pure substances and binary mixtures are less than 5 %, when they are calculated using the approaches of Kee et al.; Mason, Kestin, and Uribe; Paul and Warnatz; or Ern and Giovangigli. Recommendations stemming from the review include (1) revisiting the supporting data required by the various computational approaches, and updating the data sets with accurate potential parameters, dipole moments, and polarizabilities; (2) characterizing the range of parameter space over which the fit to experimental data is good, rather than the current practice of reporting only the parameter set that best fits the data; (3) looking for improved combining rules, since existing rules were found to under-predict the viscosity in most cases; (4

  2. Improving the electrical properties of graphene layers by chemical doping

    NASA Astrophysics Data System (ADS)

    Farooq Khan, Muhammad; Zahir Iqbal, Muhammad; Waqas Iqbal, Muhammad; Eom, Jonghwa

    2014-10-01

    Although the electronic properties of graphene layers can be modulated by various doping techniques, most of doping methods cost degradation of structural uniqueness or electrical mobility. It is matter of huge concern to develop a technique to improve the electrical properties of graphene while sustaining its superior properties. Here, we report the modification of electrical properties of single- bi- and trilayer graphene by chemical reaction with potassium nitrate (KNO3) solution. Raman spectroscopy and electrical transport measurements showed the n-doping effect of graphene by KNO3. The effect was most dominant in single layer graphene, and the mobility of single layer graphene was improved by the factor of more than 3. The chemical doping by using KNO3 provides a facile approach to improve the electrical properties of graphene layers sustaining their unique characteristics.

  3. Electrical and Mechanical Properties of Graphene

    NASA Astrophysics Data System (ADS)

    Bao, Wenzhong

    Graphene is an exciting new atomically-thin two-dimensional (2D) system of carbon atoms organized in a hexagonal lattice structure. This "wonder material" has been extensively studied in the last few years since it's first isolation in 2004. Its rapid rise to popularity in scientific and technological communities can be attributed to a number of its exceptional properties. In this thesis I will present several topics including fabrication of graphene devices, electrical and mechanical properties of graphene. I will start with a brief introduction of electronic transport in nanosclae system including quantum Hall effect, followed by a discussion of fundamental electrical and mechanical properties of graphene. Next I will describe how graphene devices are produced: from the famous "mechnical exfoliation" to our innovative "scratching exfoliation" method, together with the traditional lithography fabrication for graphene devices. We also developed a lithography-free technique for making electrical contacts to suspended graphene devices. Most of the suspended devices presented in this thesis are fabricated by this technique. Graphene has remarkable electrical properties thanks to its crystal and band structures. In Chapter 3, I will first focus on proximity-induced superconductivity in graphene Josephson transistors. In this section we investigate electronic transport in single layer graphene coupled to superconducting electrodes. We observe significant suppression in the critical current I c and large variation in the product IcR n in comparison to theoretic prediction; both phenomena can be satisfactorily accounted for by premature switching in underdamped Josephson junctions. Another focus of our studies is quantum Hall effect and many body physics in graphene in suspended bilayer and trilayer graphene. We demonstrate that symmetry breaking of the first 3 Landau levels and fractional quantum Hall states are observed in both bilayer and trilayer suspended graphene

  4. Local structural distortion and electrical transport properties of Bi(Ni1/2Ti1/2)O3 perovskite under high pressure.

    PubMed

    Zhu, Jinlong; Yang, Liuxiang; Wang, Hsiu-Wen; Zhang, Jianzhong; Yang, Wenge; Hong, Xinguo; Jin, Changqing; Zhao, Yusheng

    2015-01-01

    Perovskite-structure materials generally exhibit local structural distortions that are distinct from long-range, average crystal structure. The characterization of such distortion is critical to understanding the structural and physical properties of materials. In this work, we combined Pair Distribution Function (PDF) technique with Raman spectroscopy and electrical resistivity measurement to study Bi(Ni1/2Ti1/2)O3 perovskite under high pressure. PDF analysis reveals strong local structural distortion at ambient conditions. As pressure increases, the local structure distortions are substantially suppressed and eventually vanish around 4 GPa, leading to concurrent changes in the electronic band structure and anomalies in the electrical resistivity. Consistent with PDF analysis, Raman spectroscopy data suggest that the local structure changes to a higher ordered state at pressures above 4 GPa. PMID:26671171

  5. Local structural distortion and electrical transport properties of Bi(Ni1/2Ti1/2)O3 perovskite under high pressure

    NASA Astrophysics Data System (ADS)

    Zhu, Jinlong; Yang, Liuxiang; Wang, Hsiu-Wen; Zhang, Jianzhong; Yang, Wenge; Hong, Xinguo; Jin, Changqing; Zhao, Yusheng

    2015-12-01

    Perovskite-structure materials generally exhibit local structural distortions that are distinct from long-range, average crystal structure. The characterization of such distortion is critical to understanding the structural and physical properties of materials. In this work, we combined Pair Distribution Function (PDF) technique with Raman spectroscopy and electrical resistivity measurement to study Bi(Ni1/2Ti1/2)O3 perovskite under high pressure. PDF analysis reveals strong local structural distortion at ambient conditions. As pressure increases, the local structure distortions are substantially suppressed and eventually vanish around 4 GPa, leading to concurrent changes in the electronic band structure and anomalies in the electrical resistivity. Consistent with PDF analysis, Raman spectroscopy data suggest that the local structure changes to a higher ordered state at pressures above 4 GPa.

  6. Local structural distortion and electrical transport properties of Bi(Ni1/2Ti1/2)O3 perovskite under high pressure

    PubMed Central

    Zhu, Jinlong; Yang, Liuxiang; Wang, Hsiu-Wen; Zhang, Jianzhong; Yang, Wenge; Hong, Xinguo; Jin, Changqing; Zhao, Yusheng

    2015-01-01

    Perovskite-structure materials generally exhibit local structural distortions that are distinct from long-range, average crystal structure. The characterization of such distortion is critical to understanding the structural and physical properties of materials. In this work, we combined Pair Distribution Function (PDF) technique with Raman spectroscopy and electrical resistivity measurement to study Bi(Ni1/2Ti1/2)O3 perovskite under high pressure. PDF analysis reveals strong local structural distortion at ambient conditions. As pressure increases, the local structure distortions are substantially suppressed and eventually vanish around 4 GPa, leading to concurrent changes in the electronic band structure and anomalies in the electrical resistivity. Consistent with PDF analysis, Raman spectroscopy data suggest that the local structure changes to a higher ordered state at pressures above 4 GPa. PMID:26671171

  7. Local structural distortion and electrical transport properties of Bi(Ni1/2Ti1/2)O3 perovskite under high pressure

    DOE PAGESBeta

    Zhu, Jinlong; Yang, Liuxiang; Wang, Hsiu -Wen; Zhang, Jianzhong; Yang, Wenge; Hong, Xinguo; Jin, Changqing; Zhao, Yusheng

    2015-12-16

    Perovskite-structure materials generally exhibit local structural distortions that are distinct from long-range, average crystal structure. The characterization of such distortion is critical to understanding the structural and physical properties of materials. In this work, we combined Pair Distribution Function (PDF) technique with Raman spectroscopy and electrical resistivity measurement to study Bi(Ni1/2Ti1/2)O3 perovskite under high pressure. PDF analysis reveals strong local structural distortion at ambient conditions. As pressure increases, the local structure distortions are substantially suppressed and eventually vanish around 4 GPa, leading to concurrent changes in the electronic band structure and anomalies in the electrical resistivity. We find, consistent withmore » PDF analysis, Raman spectroscopy data suggest that the local structure changes to a higher ordered state at pressures above 4 GPa.« less

  8. Transport properties of ceramic composites

    SciTech Connect

    Starr, T.L.; Hablutzel, N.

    1996-08-01

    Instrumentation and procedures have been completed for measurement of gas permeability and mass diffusivity of fiber preforms and porous materials. Results are reported for composites reinforced with Nicalon fiber in cloth lay-up and 3-D weave and with Nextel fiber in multi-layer braid. Measured permeability values range from near 100 to less than 0.1 darcies. Mass diffusivity is reported as a structure factor relating the diffusion through the porous material to that in free space. This measure is independent of the diffusing species and depends only on the pore structure of the material. Measurements are compared to predictions of a node-bond model for gas transport. Model parameters adjusted to match measured transport properties relate to physical microstructure features of the different architectures. Combination of this transport model with the CVI process model offers a predictive method to evaluate the densification behavior of various fiber preforms.

  9. Solar electric propulsion for Mars transport vehicles

    SciTech Connect

    Hickman, J.M.; Curtis, H.B.; Alexander, S.W.; Gilland, J.H.; Hack, K.J.; Lawrence, C.; Swartz, C.K.

    1990-09-01

    Solar electric propulsion (SEP) is an alternative to chemical and nuclear powered propulsion systems for both piloted and unpiloted Mars transport vehicles. Photovoltaic solar cell and array technologies were evaluated as components of SEP power systems. Of the systems considered, the SEP power system composed of multijunction solar cells in an ENTECH domed fresnel concentrator array had the least array mass and area. Trip times to Mars optimized for minimum propellant mass were calculated. Additionally, a preliminary vehicle concept was designed.

  10. Solar electric propulsion for Mars transport vehicles

    NASA Technical Reports Server (NTRS)

    Hickman, J. M.; Curtis, H. B.; Alexander, S. W.; Gilland, J. H.; Hack, K. J.; Lawrence, C.; Swartz, C. K.

    1990-01-01

    Solar electric propulsion (SEP) is an alternative to chemical and nuclear powered propulsion systems for both piloted and unpiloted Mars transport vehicles. Photovoltaic solar cell and array technologies were evaluated as components of SEP power systems. Of the systems considered, the SEP power system composed of multijunction solar cells in an ENTECH domed fresnel concentrator array had the least array mass and area. Trip times to Mars optimized for minimum propellant mass were calculated. Additionally, a preliminary vehicle concept was designed.

  11. Simulation of Electrical Transport in Rocks under Mechanical Action

    NASA Astrophysics Data System (ADS)

    Salgueiro da Silva, M. A.; Seixas, T. M.

    2015-12-01

    Rock's electrical properties can be changed by mechanical action, especially when deformation is accompanied by micro-fracturing processes. Knowing how electrical charge is generated in inelastically deformed rocks, the nature and properties of the generated charge carriers, and their spatial distribution and propagation is crucial to gain insight into the origin of seismo-electromagnetic signals. In this work, we describe briefly a model for the numerical simulation of electrical transport in rocks under mechanical action, assuming that high and low mobility charge carriers of opposite signs can be simultaneously generated by micro-fracturing processes and recombine, diffuse and drift across the sample rock. The electrical behavior can then be described using an adaptation of the formalism applied to semiconductors. We provide simulation results on a one-dimensional lattice using finite-difference discretization. Our results show that a large mobility contrast among charge carriers allows charge separation inside the deformation region, which leads to the formation of charged layers of alternate signs. Inside these layers, rapid electric field variations are observed which can lead to the emission of electromagnetic radiation. With proper positioning of current electrodes inside the deformation region, it is possible to collect electrical current even without any applied voltage. We discuss our results in the light of available experimental results on the generation of electrical and electromagnetic signals in deformed rocks.

  12. Effect of gamma ray irradiation on the structural and electrical transport properties of PrFe{sub 1−x}Mn{sub x}O{sub 3}

    SciTech Connect

    Sultan, Khalid Ikram, M.; Asokan, K.

    2014-04-24

    The effect of gamma ray irradiation on the structural and transport properties of polycrystalline bulk samples of PrFe{sub 1−x}Mn{sub x}O{sub 3} (x = 0.0, 0.1, 0.5) were investigated. The samples were synthesized by solid state reaction method and exposed to {sup 60}Co gamma radiation to accumulated dose of 625 KGy. From the Raman study, the modes exhibit a blue shift with broadening of spectral features in the irradiated samples. The dielectric constant (ε′) was also studied as a function of frequency. The dielectric constant and ac conductivity increases with Mn doping but decrease on irradiation. Exposure to gamma radiation results in substantial modification in the physical properties of these compounds.

  13. Electrical transport properties of CoMn0.2-xGaxFe1.8O4 ferrites using complex impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Tsay, Chien-Yie; Lin, Yi-Hsiang; Wang, Yao-Ming; Chang, Horng-Yi; Lei, Chien-Ming; Jen, Shien-Uang

    2016-05-01

    In this study, we report the influence of Ga content on the microstructural, magnetic, and AC impedance properties of Co-based ferrites with compositions of CoMn0.2-xGaxFe1.8O4 (x=0, 0.1, and 0.2) prepared by the solid-state reaction method. Experimental results showed that the as-prepared Co-based ferrites had a single-phase spinel structure; the Curie temperature of Co-based ferrites decreased with increasing Ga content. All ferrite samples exhibited a typical hysteresis behavior with good values of saturation magnetization at room temperature. The electrical properties of Co-based ferrites were investigated using complex impedance spectroscopy analysis in the frequency range of 100 kHz-50 MHz at temperatures of 150 to 250 oC. The impedance analysis revealed that the magnitudes of the real part (Z') and the imaginary part (Z") of complex impedance decreased with increasing temperature. Only one semicircle was observed in each complex impedance plane plot, which revealed that the contribution to conductivity was from the grain boundaries. It was found that the relaxation time for the grain boundary (τgb) also decreased with increasing temperature. The values of resistance for the grain boundary (Rgb) significantly increased with increasing Ga content, which indicated that the incorporation of Ga into Co-based ferrites enhanced the electrical resistivity.

  14. Lateral electrical transport, optical properties and photocurrent measurements in two-dimensional arrays of silicon nanocrystals embedded in SiO2.

    PubMed

    Gardelis, Spiros; Manousiadis, Pavlos; Nassiopoulou, Androula G

    2011-01-01

    In this study we investigate the electronic transport, the optical properties, and photocurrent in two-dimensional arrays of silicon nanocrystals (Si NCs) embedded in silicon dioxide, grown on quartz and having sizes in the range between less than 2 and 20 nm. Electronic transport is determined by the collective effect of Coulomb blockade gaps in the Si NCs. Absorption spectra show the well-known upshift of the energy bandgap with decreasing NC size. Photocurrent follows the absorption spectra confirming that it is composed of photo-generated carriers within the Si NCs. In films containing Si NCs with sizes less than 2 nm, strong quantum confinement and exciton localization are observed, resulting in light emission and absence of photocurrent. Our results show that Si NCs are useful building blocks of photovoltaic devices for use as better absorbers than bulk Si in the visible and ultraviolet spectral range. However, when strong quantum confinement effects come into play, carrier transport is significantly reduced due to strong exciton localization and Coulomb blockade effects, thus leading to limited photocurrent. PMID:21711736

  15. Transport properties of quark and gluon plasmas

    SciTech Connect

    Heiselberg, H.

    1993-12-01

    The kinetic properties of relativistic quark-gluon and electron-photon plasmas are described in the weak coupling limit. The troublesome Rutherford divergence at small scattering angles is screened by Debye screening for the longitudinal or electric part of the interactions. The transverse or magnetic part of the interactions is effectively screened by Landau damping of the virtual photons and gluons transferred in the QED and QCD interactions respectively. Including screening a number of transport coefficients for QCD and QED plasmas can be calculated to leading order in the interaction strength, including rates of momentum and thermal relaxation, electrical conductivity, viscosities, flavor and spin diffusion of both high temperature and degenerate plasmas. Damping of quarks and gluons as well as color diffusion in quark-gluon plasmas is, however, shown not to be sufficiently screened and the rates depends on an infrared cut-off of order the ``magnetic mass,`` m{sub mag} {approximately} g{sup 2}T.

  16. Transport properties in the atmosphere of Jupiter

    NASA Technical Reports Server (NTRS)

    Biolsi, L., Jr.

    1978-01-01

    The calculation of transport properties near the surface of a probe entering the atmosphere of Jupiter is discussed for (1) transport properties in the pure Jovian atmosphere, (2) transport properties for collisions between monatomic carbon atoms, including the effect of excited electronic states, (3) transport properties at the boundaries for mixing of the pure Jovian atmosphere and the atmosphere due to the injection of gaseous ablation products, and (4) transport properties for interactions involving some of the molecular ablation products. The transport properties were calculated using the kinetic theory of gases. Transport collision integrals were calculated for only a limited set of empirical and semiempirical interaction potentials. Since the accuracy of the fit of these empirical potentials to the true potential usually determines the accuracy of the calculation of the transport properties, the various interaction potentials used in these calculations are discussed.

  17. Structure, magnetic and electrical transport properties of the perovskites La0.67-xEuxSr0.33MnO3

    NASA Astrophysics Data System (ADS)

    Dhahri, Neila; Dhahri, Abdessalem; Dhahri, Jemai; Hlil, El-kebir; Dhahri, Essebti

    2013-01-01

    In this paper we report the structural, magnetic and electrical properties of a series of nanocrystalline La0.67-xEuxSr0.33MnO3 (0≤x≤0.3) materials which were prepared by the solid-state reaction method in air. The X-ray powder diffraction has shown that all our synthesized samples are a single phase and have crystallized in the hexagonal symmetry with R3barC space group. The scanning electron microscopy has shown smooth and densified structures, clean and pure images. Electric and magnetic measurements show that all our samples had exhibited a ferromagnetic to paramagnetic transition and a metallic to semiconductor one when temperature increases. The substitution of La3+ by Eu3+ leads to a continuously simultaneous decrease of the Curie temperature TC (from 350 K for x=0.0-258 K for x=0.3) and the metal-semi-conductor transition temperature Tp (from 310 K for x=0.0-224 K for x=0.3). The electrical resistivity data were analyzed using different theoretical models and it has been concluded that at low temperatures (ferromagnetic metallic region) the resistivity may originate from grain/domain boundary, electron-electron scattering and two-magnon scattering effects. While in the paramagnetic insulating regime, the variation of resistivity with temperature may be explained by adiabatic small polaron Hopping mechanism and variable-range hopping mechanisms. The values of activation energies were found decreasing, while the density of states at the Fermi-level, N (EF) was increasing with decreasing . A suitable explanation for the observed behavior is given.

  18. Electrical Properties and Cation Valences in the

    NASA Astrophysics Data System (ADS)

    Sehlin, Scott Richard

    The electrical properties of the (La,Ca)(Cr,Co)O _3 system were studied as a function of temperature and composition to determine the mechanisms of charge transport and charge carrier formation. The results of electrical conductivity measurements were found to be consistent with the small polaron conduction mechanism. A room temperature electrical conductivity minimum as a function of Cr content was observed for small Cr content in rm La_{1-x}Ca_{x}(Cr,Co)O _3 for x = 0.1 and for x = 0.2. This minimum was attributed to the trapping of p-type small polarons at energetically lower Cr sites. The results of Seebeck coefficient measurements for the (La,Ca)(Cr,Co)O _3 system were interpreted using the mechanism of thermally activated charge disproportionation among Co ions. To further investigate the plausibility of the assumptions of thermally activated charge disproportionation and of a small polaron conduction mechanism, a model incorporating those assumptions was developed for the electrical conductivity and Seebeck coefficient of (La,Ca)CoO_3 compositions. The temperature dependence of the electrical conductivity and Seebeck coefficient of the compositions studied was successfully modelled only when the free energy of disproportionation was modified to include coulomb screening-like interactions between charge carriers. These screening-like interactions account for the deviations from the dilute limit that arise due to the high carrier concentrations produced through thermally activated charge disproportionation. The mechanism of screening utilized in the model is also consistent with the experimentally observed trend that the free energy of disproportionation decreases with increasing acceptor (Ca) content for (La,Ca)CoO _3.

  19. Temperature dependent electrical transport of disordered reduced graphene oxide

    NASA Astrophysics Data System (ADS)

    Muchharla, Baleeswaraiah; Narayanan, T. N.; Balakrishnan, Kaushik; Ajayan, Pulickel M.; Talapatra, Saikat

    2014-06-01

    We report on the simple route for the synthesis of chemically reduced graphene oxide (rGO) using ascorbic acid (a green chemical) as a reducing agent. Temperature-dependent electrical transport properties of rGO thin films have been studied in a wide range (50 K T 400 K) of temperature. Electrical conduction in rGO thin films was displayed in two different temperature regimes. At higher temperatures, Arrhenius-like temperature dependence of resistance was observed indicating a band gap dominating transport behavior. At lower temperatures, the rGO sample showed a conduction mechanism consistent with Mott's two-dimensional variable range hopping (2D-VRH). An unsaturated negative magnetoresistance (MR) was observed up to 3 T field. A decrease in negative MR at high temperatures is attributed to the phonon scattering of charge carriers.

  20. Charge Transport Properties in Polymer Brushes

    NASA Astrophysics Data System (ADS)

    Moog, Mark; Tsui, Frank; Vonwald, Ian; You, Wei

    Electrical transport properties in poly(3-methyl)thiophene (P3MT) brushes have been studied. The P3MT brushes correspond to a new type of surface-tethered, vertically oriented conjugated molecular wires, sandwiched between two metallic electrodes to form the electrode-molecule-electrode (EME) devices. P3MT is a highly conjugated polymer, a ''workhorse'' material for organic electronics and photonics. The P3MT brushes were grown on ITO surfaces with controlled length (between 2 and 100 nm). The top electrodes were transfer-printed Au films with lateral dimensions between 200 nm and 50 μm. I-V and differential conductance measurements were performed using conductive AFM and 4-terminal techniques. Tunneling and field-emission measurements in EME devices with molecular lengths < 5 nm show HOMO mediated direct hole tunneling with energy barriers of 0.3 and 0.5 eV at the respective interfaces with ITO and Au. The transport properties in longer brushes are indicative of the two quasi-Ohmic interfaces with a characteristic offset in the conductance minimum of 0.12 V biased toward the ITO. Temperature dependent parameters have been examined at various molecular lengths. The drift mobility and the interplay between intra- and intermolecular transport have been investigated.

  1. Electrical properties of dry rocks

    NASA Technical Reports Server (NTRS)

    Morrison, H.

    1973-01-01

    The mechanism by which atmospheric moisture affects the conductivity and dielectric constant of rock specimens was studied in time and frequency domains. It is suggested that adsorbed water molecules alter the surface conductivity in a manner similar to that observed in semiconductors and insulators. Powdered basalts show a low-frequency dispersion produced by the atmospheric moisture remaining in the pore system of the sample in a high vacuum; this effect is attributed to isolated adsorption centers. Simulated lunar permafrost at 100 K and a vacuum of 10 to the -8th power torr together with data on lunar samples contaminated with atmospheric moisture and the dielectric properties of ice at various temperatures indicate that, if permafrost exists in the moon it should present a relaxation peak at approximately 300 Hz; for temperatures up to 263 K it may go up to 20 KHz. It is concluded that in order to have electrical steady state conditions in rock samples it is necessary to have volume charge accumulations at interfaces within the sample and at the electrode sample interface. A method for measuring heterogeneous dielectrics with non-negligible ohmic and dielectric conductivities is proposed and experimentally verified.

  2. Transport properties of ceramic composites

    SciTech Connect

    Starr, T.L.

    1995-08-01

    This project involves experimental and modeling investigation of the transport properties of chemical vapor infiltration (CVI) preforms and densified composites, with particular emphasis on gas permeability and mass diffusivity. The results of this work will be useful both for on-going CVI process development and for evaluation and optimization of composite materials for fossil energy applications. With preforms made with 500 filaments/tow Nicalon at 40 vol% fiber loading, permeability values are similar for square-weave cloth layup and 3-D weave at low density. At greater densification the 3-D weave permeability is lower and approaches zero with significantly more closed porosity than the cloth layup. For filament wound preforms we were unable to make reliable measurements with the available materials. A model for gas transport in these materials utilizes percolation theory concepts. The ultimate achievable density is related to the closing of a continuous gas path through the preform. As the density approaches this limit the gas permeability and diffusivity vanish exponentially. The value of this limit is controlled primarily by the preform fiber architecture. The observed difference between the cloth layup and 3-D weave materials is due to the larger pores at tow crossing points found in the 3-D weave.

  3. Synthesis, crystal structure, electrical properties, and sodium transport pathways of the new arsenate Na4Co7(AsO4)6

    NASA Astrophysics Data System (ADS)

    Ben Smida, Youssef; Marzouki, Riadh; Georges, Samuel; Kutteh, Ramzi; Avdeev, Maxim; Guesmi, Abderrahmen; Zid, Mohamed Faouzi

    2016-07-01

    A new sodium cobalt (II) arsenate Na4Co7(AsO4)6 has been synthesized by a solid-state reaction and its crystal structure determined from single crystal X-ray diffraction data. It crystallizes in the monoclinic system, space group C2/m, with a=10.7098(9) Å, b=14.7837(9) Å, c=6.6845(7) Å, and β=105.545(9)°. The structure is described as a three-dimensional framework built up of corner-edge sharing CoO6, CoO4 and AsO4 polyhedra, with interconnecting channels along [100] in which the Na+ cations are located. The densest ceramics with relative density of 94% was obtained by ball milling and optimization of sintering temperature, and its microstructure characterized by scanning electron microscopy. The electrical properties of the ceramics were studied over a temperature interval from 280 °C to 560 °C using the complex impedance spectroscopy over the range of 13 MHz-5 Hz. The ionic bulk conductivity value of the sample at 360 °C is 2.51 10-5 S cm-1 and the measured activation energy is Ea=1 eV. The sodium migration pathways in the crystal structure were investigated computationally using the bond valence site energy (BVSE) model and classical molecular dynamics (MD) simulations.

  4. Electrical properties of carbon nanotube FETs

    NASA Astrophysics Data System (ADS)

    Mizutani, T.; Ohno, Y.; Kishimoto, S.

    2008-08-01

    The electrical properties of carbon nanotube FETs (CNTFETs) have been studied in detail. The conduction type of the CNTFETs was dependent on the work function of the contact metal, which suggests that Fermi level pinning at the metal/nanotube interface is not strong. Based on the two-probe and four-probe resistance measurements, it has been shown that the carrier transport at the contact is explained by the edge contact model even in the diffusive regime. The chemical doping using F4TCNQ was effective in reducing not only the channel resistance but also the contact resistance. In the CNTFETs fabricated using plasma-enhanced (PE) CVD-grown nanotubes, the drain current of the most of the devices could be modulated by the gate voltage with small OFF current suggesting the preferential growth of the nanotubes with semiconducting behavior. Multichannel top-gate CNTFETs with horizontally-aligned nanotubes as channels have been successfully fabricated using CNT growth on the ST-cut quartz substrate, arc-discharge plasma deposition of the catalyst metal, and ALD gate insulator deposition. The devices show normally-on and n-type conduction property with a relatively-high ON current of 13 mA/mm. CNTFETs with nanotube network have also been fabricated by direct growth on the SiO2/Si substrate using grid-inserted PECVD and using catalyst formed on the channel area of the FETs. The uniformity of the electrical properties of the network channel CNTFETs were very good. Finally, it has been shown that the surface potential profile measurement based on the electrostatic force detection in the scanning probe microscopy was effective in studying the behavior of the CNTFETs such as the transient behavior and the effect of the defects.

  5. Optical and electrical properties of niobium carbide

    SciTech Connect

    Allison, C.Y.; Modine, F.A.; French, R.H.

    1987-02-15

    The optical and electrical properties were measured for single crystals of NbC/sub x/ for x = 0.98, 0.87, and 0.76, and for one hot-isostatically-pressed sample of NbC/sub 0.88/. Specular reflectance was measured between 0.025 and 11 eV, and ellipsometry measurements were made at 1.96 eV. By using the phase obtained from ellipsometry data to correct the Kramers-Kronig analyses of the reflectances, we were able to improve the accuracy of the resulting optical functions. For energies below 6.5 eV, there are differences in the reflectance and optical functions of the samples which are due to differences in x. We interpret the low-energy optical data in terms of intraband transitions, which allows us to calculate the dc conductivity as well as other electronic transport parameters. These parameters agree well with the electrical conductivities and the Hall coefficients obtained by the van der Pauw technique. The higher-energy optical data are interpreted in light of recent electronic-structure calculations, which suggest that most interband transitions occur near the square face of the Brillouin zone.

  6. Transport properties of strontium titanate niobates

    SciTech Connect

    Podkorytov, A.L.; Pantyukhina, M.I.; Zhukovskii, V.M.

    1995-08-01

    In this work the authors studied transport properties of Sr{sub 3}NiNb{sub 2}O{sub 10} and Sr{sub 6-x}Ti{sub x}Nb{sub 2}O{sub 11+x} in order to develop views concerning their high-temperature behavior and mechanisms of disordering in their structures. The authors measured the electrical conductivity (f+1 kHz, RLC meter, 500-1300{degrees}C) and the effective self-diffusion coefficients of radionuclides {sup 90}Sr, {sup 44}Ti, and {sup 95}Nb using radiometric depth profiling (RKB-4IeM {beta}-radiometer) of ceramic samples (porosity no greater than 10%), as described. The samples with radionuclides applied to their faces were annealed in the range 1270-1470 K for 24-100 h. The error in the diffusion coefficients thus measured did not exceed 20%.

  7. Structure and electrical transport properties of pure and Li{sub 2}O-doped CuO/MgO solid solution

    SciTech Connect

    El-Shobaky, G.A. . E-mail: elshobaky@yahoo.com; Mokhtar, M.; Salem, A.M.

    2005-06-15

    The different electrical properties, {sigma}, {epsilon}', tan {delta} and E {sub {sigma}} of pure and Li{sub 2}O-doped CuO/MgO solid solution were investigated. The mole fraction of CuO (MF) was varied between 0.048 and 0.2. Pure and doped samples were subjected to heat treatments at 673 and 1073 K. The results revealed that the amount of CuO dissolved in MgO lattice increases progressively by increasing the MF as evidenced from the progressive decrease in the intensity of all diffraction lines of undissolved CuO phase. The dissolution process of copper ions in MgO lattice was accompanied by progressive increase in its lattice parameter. This process being conducted at 1073 K was accompanied by a significant progressive increase in the values of {sigma}, {epsilon}' and tan {delta} with subsequent decrease in the value of E {sub {sigma}}. The increase in the MF value of CuO from 0.048 to 0.2 led to a significant increase in the value of {sigma} {sub DC}, measured at room temperature, from 6.33 x 10{sup -12} to 9.9 x 10{sup -10} {omega}{sup -1} cm{sup -1} and E {sub {sigma}} decreases from 0.76 to 0.58 eV. Li{sub 2}O doping of the investigated system followed by calcination at 1073 K resulted in a measurable increase in values of {sigma}, {epsilon}' and tan {delta} with subsequent decrease in E {sub {sigma}}. These results were discussed in the light of the possible effective increase in the charge carriers concentration (Cu{sup 2+}ions dissolved in MgO lattice) and also to an effective increase in mobility of these charge carriers by Li{sub 2}O doping.

  8. TRANSPORT PROPERTY MEASUREMENTS OF HFC-236EA

    EPA Science Inventory

    The report gives results of an evaluation of transport properties of 1, 1, 1, 2, 3, 3-hexafluoropropane (HFC-236ea), with liquid viscosity and thermal conductivity being the two main transport properties of interest. In addition, the specific heat and density of refrigerant/lubri...

  9. TRANSPORT PROPERTY MEASUREMENTS OF HFC-236EA

    EPA Science Inventory

    The report gives results of an evaluation of transport properties of 1,1,1,2,3,3,-hexafluoropropane (HFC-236ea), with liquid viscosity and thermal conductivity being the two main transport properties of interest. In addition, the specific heat and density of refrigerant/lubrican...

  10. The Electrical Property of Matter.

    ERIC Educational Resources Information Center

    DeMeo, Stephen; Lythcott, Jean

    2001-01-01

    Describes a demonstration of static charge using balloons and crystals to illustrate the electrical nature of matter. Building on the classic physics demonstration that uses pieces of paper and a plastic rod, this approach adds a new dimension of chemistry. Offers suggestions for how to discuss the observed phenomenon. (DLH)

  11. Transport properties of fission product vapors

    SciTech Connect

    Im, K.H.; Ahluwalia, R.K.

    1983-07-01

    Kinetic theory of gases is used to calculate the transport properties of fission product vapors in a steam and hydrogen environment. Provided in tabular form is diffusivity of steam and hydrogen, viscosity and thermal conductivity of the gaseous mixture, and diffusivity of cesium iodide, cesium hydroxide, diatomic tellurium and tellurium dioxide. These transport properties are required in determining the thermal-hydraulics of and fission product transport in light water reactors.

  12. Research and development of electric vehicles for clean transportation.

    PubMed

    Wada, Masayoshi

    2009-01-01

    This article presents the research and development of an electric vehicle (EV) in Department of Human-Robotics Saitama Institute of Technology, Japan. Electric mobile systems developed in our laboratory include a converted electric automobile, electric wheelchair and personal mobile robot. These mobile systems contribute to realize clean transportation since energy sources and devices from all vehicles, i.e., batteries and electric motors, does not deteriorate the environment. To drive motors for vehicle traveling, robotic technologies were applied. PMID:19803077

  13. Electrical transport measurements of individual bismuth nanowires and carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Jang, Wan Young

    Nanostructures are defined by reducing dimensions. When the reduced size of materials is comparable to the Fermi wavelength, quantum size effect occurs. Dimensionality plays a critical role in determining the electronic properties of materials, because the density of states of materials is quite different. Nanowires have attracted much attention recently due to their fundamental interest and potential applications. A number of materials have been tried. Among them, bismuth has unique properties. Bismuth has the smallest effective mass as small as 0.001me. This small effective mass of Bi nanowires allows one to observe the quantum confinement effect easily. Also Bi nanowires are good candidates for a low-dimensional transport study due to long mean free path. Because of these remarkable properties of Bi nanowires, many efforts have been made to study Bi nanowires. However, because bismuth is extremely sensitive to the oxide, it is very difficult to make a reliable device. So far, array measurements of Bi nanowires have been reported. The study is focused on the synthesis and electric transport measurements of individual Bi nanowires. Bi nanowires are synthesized by electrodeposition using either anodic aluminum oxide (AAO) templates or commercially available track etched polycarbonate membranes (PCTE). The desired nanowire has a heterostructure of Au - Bi - Au. Au wires on both sides serve as contact electrodes with Bi. To extract nanowires from PCTE or AAO, several attempts have been made. Devices consisting of single Bi nanowires grown by hydrothermal method are fabricated and electrical measurements have been carried out after in-situ deposition of Pt electrodes. The temperature dependence of resistance of majority of nanowires increases with decreasing temperature, showing polycrystalline nature of nanowires. However, some nanowires show resistance peaks at low temperature, suggesting quantum size effect (QSE). Magnetoresistance (MR) has also been measured. We

  14. Magnetic and electrical properties of Martian particles

    NASA Technical Reports Server (NTRS)

    Olhoeft, G. R.

    1991-01-01

    The only determinations of the magnetic properties of Martian materials come from experiments on the two Viking Landers. The results suggest Martian soil containing 1 to 10 percent of a highly magnetic phase. Though the magnetic phase mineral was not conclusively identified, the predominate interpretation is that the magnetic phase is probably maghemite. The electrical properties of the surface of Mars were only measured remotely by observations with Earth based radar, microwave radiometry, and inference from radio-occultation of Mars orbiting spacecraft. No direct measurements of electrical properties on Martian materials have been performed.

  15. Review on measurement techniques of transport properties of nanowires.

    PubMed

    Rojo, Miguel Muñoz; Calero, Olga Caballero; Lopeandia, A F; Rodriguez-Viejo, J; Martín-Gonzalez, Marisol

    2013-12-01

    Physical properties at the nanoscale are novel and different from those in bulk materials. Over the last few decades, there has been an ever growing interest in the fabrication of nanowire structures for a wide variety of applications including energy generation purposes. Nevertheless, the study of their transport properties, such as thermal conductivity, electrical conductivity or Seebeck coefficient, remains an experimental challenge. For instance, in the particular case of nanostructured thermoelectrics, theoretical calculations have shown that nanowires offer a promising way of enhancing the hitherto low efficiency of these materials in the conversion of temperature differences into electricity. Therefore, within the thermoelectrical community there has been a great experimental effort in the measurement of these quantities in actual nanowires. The measurements of these properties at the nanoscale are also of interest in fields other than energy, such as electrical components for microchips, field effect transistors, sensors, and other low scale devices. For all these applications, knowing the transport properties is mandatory. This review deals with the latest techniques developed to perform the measurement of these transport properties in nanowires. A thorough overview of the most important and modern techniques used for the characterization of different kinds of nanowires will be shown. PMID:24113712

  16. The Electrical Properties of Biphenylenes

    SciTech Connect

    Schneebeli, S.; Hybertsen, M.; Kamenetska, M.; Foss, F.; Vazquez, H.; Skouta, R.; Venkataraman, L.; Breslow, R.

    2010-09-17

    The effect of the partial antiaromaticity of biphenylene on its substitution chemistry, its oxidation potential, and its single-molecule conductance is explored. Biphenylene and fluorene molecules with linkers of two amino groups or two cyclic thioether groups were synthesized and their conduction properties were investigated using scanning tunneling microscopy (STM) break-junction techniques and DFT calculations. Despite the partial antiaromaticity of biphenylene, which causes the biphenylenes to be much more easily oxidizable, no significant increase in molecular conductance was found.

  17. Ferroelectric gated electrical transport in CdS nanotetrapods.

    PubMed

    Fu, Wangyang; Qin, Shengyong; Liu, Lei; Kim, Tae-Hwan; Hellstrom, Sondra; Wang, Wenlong; Liang, Wenjie; Bai, Xuedong; Li, An-Ping; Wang, Enge

    2011-05-11

    Complex nanostructures such as branched semiconductor nanotetrapods are promising building blocks for next-generation nanoelectronics. Here we report on the electrical transport properties of individual CdS tetrapods in a field effect transistor (FET) configuration with a ferroelectric Ba(0.7)Sr(0.3)TiO(3) film as high-k, switchable gate dielectric. A cryogenic four-probe scanning tunneling microscopy (STM) is used to probe the electrical transport through individual nanotetrapods at different temperatures. A p-type field effect is observed at room temperature, owing to the enhanced gate capacitance coupling. And the reversible remnant polarization of the ferroelectric gate dielectric leads to a well-defined nonvolatile memory effect. The field effect is shown to originate from the channel tuning in the arm/core/arm junctions of nanotetrapods. At low temperature (8.5 K), the nanotetrapod devices exhibit a ferroelectric-modulated single-electron transistor (SET) behavior. The results illustrate how the characteristics of a ferroelectric such as switchable polarization and high dielectric constant can be exploited to control the functionality of individual three-dimensional nanoarchitectures. PMID:21513340

  18. Electrical properties of single CdTe nanowires

    PubMed Central

    Matei, Elena; Florica, Camelia; Costas, Andreea; Toimil-Molares, María Eugenia

    2015-01-01

    Summary Ion track, nanoporous membranes were employed as templates for the preparation of CdTe nanowires. For this purpose, electrochemical deposition from a bath containing Cd and Te ions was employed. This process leads to high aspect ratio CdTe nanowires, which were harvested and placed on a substrate with lithographically patterned, interdigitated electrodes. Focused ion beam-induced metallization was used to produce individual nanowires with electrical contacts and electrical measurements were performed on these individual nanowires. The influence of a bottom gate was investigated and it was found that surface passivation leads to improved transport properties. PMID:25821685

  19. Nonlinear electrical properties of Si three-terminal junction devices

    NASA Astrophysics Data System (ADS)

    Meng, Fantao; Sun, Jie; Graczyk, Mariusz; Zhang, Kailiang; Prunnila, Mika; Ahopelto, Jouni; Shi, Peixiong; Chu, Jinkui; Maximov, Ivan; Xu, H. Q.

    2010-12-01

    This letter reports on the realization and characterization of silicon three-terminal junction devices made in a silicon-on-insulator wafer. Room temperature electrical measurements show that the fabricated devices exhibit pronounced nonlinear electrical properties inherent to ballistic electron transport in a three-terminal ballistic junction (TBJ) device. The results show that room temperature functional TBJ devices can be realized in a semiconductor material other than high-mobility III-V semiconductor heterostructures and provide a simple design principle for compact silicon devices in nanoelectronics.

  20. Electrical properties of semiconductor quantum dots

    SciTech Connect

    Kharlamov, V. F. Korostelev, D. A.; Bogoraz, I. G.; Milovidova, O. A.; Sergeyev, V. O.

    2013-04-15

    A method, which makes it possible to obtain semiconductor particles V Almost-Equal-To 10{sup -20} cm{sup 3} in volume (quantum dots) with a concentration of up to 10{sup 11} cm{sup -2} and electrical contacts to each of them, is suggested. High variability in the electrical properties of such particles from a metal oxide (CuO or NiO) after the chemisorption of gas molecules is found.

  1. Thermal stability and electrical transport properties of β-Zn4Sb3 single crystal prepared by Sn-flux method

    NASA Astrophysics Data System (ADS)

    Shai, Xuxia; Deng, Shukang; Meng, Daiyi; Shen, Lanxian; Li, Decong

    2014-11-01

    In this work, β-Zn4Sb3 single crystals with space group R3barc were prepared by Sn-flux method according to the stoichiometric ratios of Zn4+x(0-0.8)Sb3Sn3. thermogravimetric-differential thermal analysis (TG-DTA) shows that there has no weight loss untill temperature reaches to melting point of 821 K. All crystals behave characteristic of p-type conduction and the carrier densities are independent on the initial composition. Comparing with β-Zn4Sb3 polycrystalline sample, the carrier mobility of the present single crystals are increased. The crystals with X>0 possess higher electrical conductivity, and the highest power factor of 1.18×10-3 Wm-1 K-2 is obtained at 585 K for the sample with X=0.8.

  2. Electrical properties of dislocations in III-Nitrides

    SciTech Connect

    Cavalcoli, D.; Minj, A.; Pandey, S.; Cavallini, A.

    2014-02-21

    Research on GaN, AlN, InN (III-N) and their alloys is achieving new heights due their high potential applications in photonics and electronics. III-N semiconductors are mostly grown epitaxially on sapphire, and due to the large lattice mismatch and the differences in the thermal expansion coefficients, the structures usually contain many threading dislocations (TDs). While their structural properties have been widely investigated, their electrical characteristics and their role in the transport properties of the devices are still debated. In the present contribution we will show conductive AFM studies of TDs in GaN and Al/In GaN ternary alloys to evidence the role of strain, different surface polarity and composition on their electrical properties. Local I-V curves measured at TDs allowed us to clarify their role in the macroscopic electrical properties (leakage current, mobilities) of III-N based devices. Samples obtained by different growers (AIXTRON, III-V Lab) were studied. The comparison between the results obtained in the different alloys allowed us to understand the role of In and Al on the TDs electrical properties.

  3. Electrical properties of dislocations in III-Nitrides

    NASA Astrophysics Data System (ADS)

    Cavalcoli, D.; Minj, A.; Pandey, S.; Cavallini, A.

    2014-02-01

    Research on GaN, AlN, InN (III-N) and their alloys is achieving new heights due their high potential applications in photonics and electronics. III-N semiconductors are mostly grown epitaxially on sapphire, and due to the large lattice mismatch and the differences in the thermal expansion coefficients, the structures usually contain many threading dislocations (TDs). While their structural properties have been widely investigated, their electrical characteristics and their role in the transport properties of the devices are still debated. In the present contribution we will show conductive AFM studies of TDs in GaN and Al/In GaN ternary alloys to evidence the role of strain, different surface polarity and composition on their electrical properties. Local I-V curves measured at TDs allowed us to clarify their role in the macroscopic electrical properties (leakage current, mobilities) of III-N based devices. Samples obtained by different growers (AIXTRON, III-V Lab) were studied. The comparison between the results obtained in the different alloys allowed us to understand the role of In and Al on the TDs electrical properties.

  4. Baseline tests of the Volkswagen transporter electric delivery van

    NASA Technical Reports Server (NTRS)

    Soltis, R. F.; Mcbrien, E. F.; Bozek, J. M.; Gourash, F.

    1978-01-01

    The Volkswagen Transporter, an electric delivery van, was tested as part of an Energy Research and Development Administration (ERDA) project to characterize the state of the art of electric vehicles. The Volkswagen Transporter is a standard Volkswagen van that has been converted to an electric vehicle. It is powered by a 144-volt traction battery. A direct current (dc) chopper controller, actuated by a conventional accelerator pedal, regulates the voltage or power applied to the 16-kilowatt (21-hp) motor. The braking system uses conventional hydraulic braking in combination with an electric regenerative braking system. The Volkswagen vehicle performance test results are presented.

  5. Investigation on the electrical transport properties of highly (00l)-textured Sb{sub 2}Te{sub 3} films deposited by molecular beam epitaxy

    SciTech Connect

    Zhang, Xiangpeng; Zeng, Zhigang E-mail: zhiyuhu@shu.edu.cn; Shen, Chao; Wang, Zhichong; Lin, Cong; Zhang, Ziqiang; Hu, Zhiyu E-mail: zhiyuhu@shu.edu.cn

    2014-01-14

    Highly (00l)-textured antimony telluride films were fabricated using molecular beam epitaxy (MBE) on Si (111) substrate at 280 °C. X-ray diffraction analysis implying the samples have good crystalline quality, simultaneously, the grain sizes coarsening with increasing thickness. The results of Hall coefficient measurement demonstrated that the carrier concentration and mobility are strongly affected by grain boundaries and microcrystalline internal defects. It was found that the grain boundaries play a primary factor influencing the carrier concentration in thinner film. At room temperature, the results in a maximum mobility value of 305 cm{sup 2}/Vs for 121-nm-thick film, and the electrical conductivity increased from 425.7 S/cm to 1036 S/cm as the thickness varied from 28 nm to 121 nm. In the range of room temperature to 150 °C, the resistivity almost linearly increased with increasing temperature. This may be explained by low concentration of impurities or defects and shallow impurity band. For difference thickness films, temperature coefficients of resistivity are substantially equal, and the values are about 3 ∼ 4 μΩ⋅cm/K.

  6. Calculating Theromodynamic And Transport Properties Of Fluids

    NASA Technical Reports Server (NTRS)

    Proctor, Margaret P.; Klem, Mark D.

    1987-01-01

    Computer program incorporates van der Waals equation and correction tables. FLUID program developed to calculate thermodynamic and transport properties of pure fluids in both liquid and gas phases. Properties calculated by use of simple gas model, empirical corrections, and efficient numerical interpolation scheme. Produces results that agree very well with measured values. Much faster than older, more complex programs developed for same purpose.

  7. Ionic transport and electrical relaxation in glass

    NASA Astrophysics Data System (ADS)

    Moynihan, C. T.; Barkatt, A.

    1987-09-01

    The basic purpose of the work described was to achieve extensive and quantitative understanding of ionic transport processes in melts and glasses by means of a combination of experimental measurements and theoretical modeling. Two major subjects of the study were the mechanism of dielectric relaxation in ionically conducting glasses and the large retardation of ionic transport in mixed alkali systems.

  8. Charge carrier transport properties in layer structured hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Doan, T. C.; Li, J.; Lin, J. Y.; Jiang, H. X.

    2014-10-01

    Due to its large in-plane thermal conductivity, high temperature and chemical stability, large energy band gap (˜ 6.4 eV), hexagonal boron nitride (hBN) has emerged as an important material for applications in deep ultraviolet photonic devices. Among the members of the III-nitride material system, hBN is the least studied and understood. The study of the electrical transport properties of hBN is of utmost importance with a view to realizing practical device applications. Wafer-scale hBN epilayers have been successfully synthesized by metal organic chemical deposition and their electrical transport properties have been probed by variable temperature Hall effect measurements. The results demonstrate that undoped hBN is a semiconductor exhibiting weak p-type at high temperatures (> 700 °K). The measured acceptor energy level is about 0.68 eV above the valence band. In contrast to the electrical transport properties of traditional III-nitride wide bandgap semiconductors, the temperature dependence of the hole mobility in hBN can be described by the form of μ ∝ (T/T0)-α with α = 3.02, satisfying the two-dimensional (2D) carrier transport limit dominated by the polar optical phonon scattering. This behavior is a direct consequence of the fact that hBN is a layer structured material. The optical phonon energy deduced from the temperature dependence of the hole mobility is ħω = 192 meV (or 1546 cm-1), which is consistent with values previously obtained using other techniques. The present results extend our understanding of the charge carrier transport properties beyond the traditional III-nitride semiconductors.

  9. A Experimental Investigation Into the Electrical Transport Properties of LANTHANUM(2)COPPER OXIDE(4+DELTA) and NEODYMIUM(2)COPPER OXIDE(4+DELTA)

    NASA Astrophysics Data System (ADS)

    Ryder, J.

    1990-01-01

    suppressed. Our magnetic transport measurements imply that superconductivity arises here from a condensation of highly local carrier-pairs. These measurements, together with the thermoelectric power, indicate possible precursor behaviour in La_2CuO _{4 + delta} up to ~60K. Vacancy-doped Nd_2 CuO_{4 + delta} shows no tendency to either phase segregation or superconductivity, with important implications for the mechanism of both processes in La_2CuO_{4 + delta}.

  10. Electron transport in argon in crossed electric and magnetic fields

    PubMed

    Ness; Makabe

    2000-09-01

    An investigation of electron transport in argon in the presence of crossed electric and magnetic fields is carried out over a wide range of values of electric and magnetic field strengths. Values of mean energy, ionization rate, drift velocity, and diffusion tensor are reported here. Two unexpected phenomena arise; for certain values of electric and magnetic field we find regions where the swarm mean energy decreases with increasing electric fields for a fixed magnetic field and regions where swarm mean energy increases with increasing magnetic field for a fixed electric field. PMID:11088933

  11. Transport Properties and Transport Phenomena in Casting Nickel Superalloys

    NASA Astrophysics Data System (ADS)

    Felicelli, S. D.; Sung, P. K.; Poirier, D. R.; Heinrich, J. C.

    1998-11-01

    Nickel superalloys that are used in the high-temperature regions of gas-turbine engines are cast by directional solidification (DS). In the DS processes, the castings are cooled from below, and three zones exist during solidification: (1) an all-solid zone at the bottom, (2) a "mushy zone" that is comprised of solid and liquid material, and (3) an overlying all-liquid zone. Computer simulations can be useful in predicting the complex transport phenomena that occur during solidification, but realistic simulations require accurate values of the transport properties. In addition to transport properties, the thermodynamic equilibria between the solid and liquid during solidification must also be known with reasonable accuracy. The importance of using reasonably accurate estimations of the transport properties is illustrated by two-dimensional simulations of the convection during solidification and the coincidental macrosegregation in the DS castings of multicomponent Ni-base alloys. In these simulations, we examine the sensitivity of the calculated results to measured partition ratios, thermal expansion coefficients, and viscosities that are estimated by regression analyses and correlations of existing property data.

  12. Electrically tunable transport in the antiferromagnetic Mott insulator Sr2IrO4

    NASA Astrophysics Data System (ADS)

    Wang, C.; Seinige, H.; Cao, G.; Zhou, J.-S.; Goodenough, J. B.; Tsoi, M.

    2015-09-01

    Electronic transport properties of the antiferromagnetic Mott insulator S r2Ir O4 have been investigated under extremely high electric biases. Using nanoscale contacts, we apply electric fields up to a few MV/m to a single crystal of S r2Ir O4 and observe a continuous reduction in the material's resistivity with increasing bias, characterized by a reduction in the transport activation energy by as much as 16 % . Temperature-dependent resistivity measurements provide a means to unambiguously retrieve the bias dependence of the activation energy from the Arrhenius plots at different biases. We further demonstrate the feasibility of reversible resistive switching induced by the electric bias, which is of interest for the emerging field of antiferromagnetic spintronics. Our findings demonstrate the potential of electrical means for tuning electronic properties in 5 d transition-metal oxides and suggest a promising path towards development of next-generation functional devices.

  13. Central role of the observable electric potential in transport equations.

    PubMed

    Garrido, J; Compañ, V; López, M L

    2001-07-01

    Nonequilibrium systems are usually studied in the framework of transport equations that involve the true electric potential (TEP), a nonobservable variable. Nevertheless another electric potential, the observable electric potential (OEP), may be defined to construct a useful set of transport equations. In this paper several basic characteristics of the OEP are deduced and emphasized: (i) the OEP distribution depends on thermodynamic state of the solution, (ii) the observable equations have a reference value for all other transport equations, (iii) the bridge that connects the OEP with a certain TEP is usually defined by the ion activity coefficient, (iv) the electric charge density is a nonobservable variable, and (v) the OEP formulation constitutes a natural model for studying the fluxes in membrane systems. PMID:11461346

  14. Transport properties of graphene and its application

    NASA Astrophysics Data System (ADS)

    Lu, Jianming

    This thesis focuses on the transport properties of graphene, a new emerging atomically thin, two-dimensional material, with and without the application of a magnetic field. Because of its high mobility, graphene is a promising candidate for Extraordinary Magnetoresistance (EMR) devices. The magnetoresistance of an EMR device arises mainly from its geometry rather than the intrinsic response of the material itself to an applied magnetic field. As a result, the geometric parameters play an important role in its performance. Experiments employing various combinations of geometric parameters and graphene of different quality levels were conducted to determine the optimal results. We found that the optimized parameters vary for different applied magnetic fields. In a magnetic field of 9 Tesla, magnetoresistance up to 55,000% was observed. In addition, Finite Element Analysis (FEA) simulations are used to complement the experiments and explain the measured magnetoresistance. The excellent agreement between the simulations and experimental results indicates that theoretical simulation can be used as a convenient method to explore EMR devices with alternative geometries or materials. The anomalous quantum Hall effect is one of the most exciting properties of graphene. The observation of the v=0 state above a critical magnetic field is closely related to the quality of the graphene, where a higher quality reduces the critical field needed. With our high quality graphene sample, the critical field is reduced to 6.75 Tesla. Moreover, from 6.75 T to 9T, the resistance at the cross point of the metal-insulator transition (MIT) is very close to h/2e2, which resembles the case of a disordered two-dimensional electron gas (2DEG) and may indicate a similar physical mechanism. In addition to the magnetotransport measurements, the current saturation of graphene in a high electric field is studied both theoretically and experimentally. This thesis focuses primarily on bilayer graphene

  15. Interplay between electrical and rheological properties of viscoelastic inks

    NASA Astrophysics Data System (ADS)

    Yu, Milim; Ahn, Kyung Hyun; Lee, Seung Jong

    2016-04-01

    We investigated the effect of the interaction between the electrical and rheological properties of the ink in electrodydrodynamic (EHD) printing process by designing model systems that control both the electrical conductivity and the viscoelasticity of the ink to observe how they affect the Taylor cone jet formation. The results demonstrate that the initial voltage at which the Taylor cone jet first appears and the final voltage at which the jet becomes unstable increase at higher electrical conductivity as the conical shape with large surface area is formed and grants stability at higher conductivity. Increased viscosity and elasticity also lead to the similar result: increase in the initial and final voltages, which can be attributed to the slower charge transport that minimizes the stabilizing effect of the inks' electrical conductivity. In addition, we use two dimensionless variables (dimensionless flow rate and dimensionless voltage) to make an operating window map of the EHD process. Through this map, the processing condition for the Taylor cone jet zone can be predicted with respect to the effect of the interplay between the electrical and rheological properties of the ink.

  16. Solar electric propulsion and interorbital transportation

    NASA Technical Reports Server (NTRS)

    Austin, R. E.

    1978-01-01

    In-house MSFC and contracted systems studies have evaluated the requirements associated with candidate SEP missions and the results point to a standard system approach for both program flexibility and economy. The prospects for economical space transportation in the 1980s have already provided a stimulus for Space Industrialization (SI) planning. Two SI initiatives that are used as examples for interorbital transportation requirements are discussed - Public Service Platforms and Satellite Power System. The interorbital requirements for SI range from support of manned geosynchronous missions to transfers of bulk cargo and large-delicate space structures from low earth orbit to geosynchronous orbit.

  17. Research on lunar materials. [optical, chemical, and electrical properties

    NASA Technical Reports Server (NTRS)

    Gold, T.

    1978-01-01

    Abstracts of 14 research reports relating to investigations of lunar samples are presented. The principal topics covered include: (1) optical properties of surface and core samples; (2) chemical composition of the surface layers of lunar grains: Auger electron spectroscopy of lunar soil and ground rock samples; (3) high frequency electrical properties of lunar soil and rock samples and their relevance for the interpretation of lunar radar observations; (4) the electrostatic dust transport process; (5) secondary electron emission characteristics of lunar soil samples and their relevance to the dust transportation process; (6) grain size distribution in surface soil and core samples; and (7) the optical and chemical effects of simulated solar wind (2keV proton and a particle radiation) on lunar material.

  18. Magnetoelectric and thermoelectric transport in graphene and helical metal: Effect of applied electric field

    NASA Astrophysics Data System (ADS)

    Chao, Sung-Po; Wei, Huazhou; Aji, Vivek

    2012-02-01

    We report on the electrical and thermoelectric transport properties of the surface state of the 3D topological insulator (TI) and graphene in a quantizing magnetic field. An unique feature of these systems is the evolution of the Landau level spectrum as a function of applied in plane electric field. We bench mark out results at small fields by computing conductivity and thermopower within linear response. We find that the universal values of thermopower in the clean limit depend on the gyromagnetic ratio in TIs, providing a clear distinction from graphene. In large electric fields we find an oscillation of conductivity as a function of applied electric field for fixed chemical potential, but not for fixed particle density. Signatures of the Landau level dependence on electric fields are also found in thermopower. These results are suggested as possible probes, in transport measurements of topological surface states.

  19. Electrical properties of seafloor massive sulfides

    NASA Astrophysics Data System (ADS)

    Spagnoli, Giovanni; Hannington, Mark; Bairlein, Katharina; Hördt, Andreas; Jegen, Marion; Petersen, Sven; Laurila, Tea

    2016-06-01

    Seafloor massive sulfide (SMS) deposits are increasingly seen as important marine metal resources for the future. A growing number of industrialized nations are involved in the surveying and sampling of such deposits by drilling. Drill ships are expensive and their availability can be limited; seabed drill rigs are a cost-effective alternative and more suitable for obtaining cores for resource evaluation. In order to achieve the objectives of resource evaluations, details are required of the geological, mineralogical, and physical properties of the polymetallic deposits and their host rocks. Electrical properties of the deposits and their ore minerals are distinct from their unmineralized host rocks. Therefore, the use of electrical methods to detect SMS while drilling and recovering drill cores could decrease the costs and accelerate offshore operations by limiting the amount of drilling in unmineralized material. This paper presents new data regarding the electrical properties of SMS cores that can be used in that assessment. Frequency-dependent complex electrical resistivity in the frequency range between 0.002 and 100 Hz was examined in order to potentially discriminate between different types of fresh rocks, alteration and mineralization. Forty mini-cores of SMS and unmineralized host rocks were tested in the laboratory, originating from different tectonic settings such as the intermediate-spreading ridges of the Galapagos and Axial Seamount, and the Pacmanus back-arc basin. The results indicate that there is a clear potential to distinguish between mineralized and non-mineralized samples, with some evidence that even different types of mineralization can be discriminated. This could be achieved using resistivity magnitude alone with appropriate rig-mounted electrical sensors. Exploiting the frequency-dependent behavior of resistivity might amplify the differences and further improve the rock characterization.

  20. Electrical properties of seafloor massive sulfides

    NASA Astrophysics Data System (ADS)

    Spagnoli, Giovanni; Hannington, Mark; Bairlein, Katharina; Hördt, Andreas; Jegen, Marion; Petersen, Sven; Laurila, Tea

    2016-02-01

    Seafloor massive sulfide (SMS) deposits are increasingly seen as important marine metal resources for the future. A growing number of industrialized nations are involved in the surveying and sampling of such deposits by drilling. Drill ships are expensive and their availability can be limited; seabed drill rigs are a cost-effective alternative and more suitable for obtaining cores for resource evaluation. In order to achieve the objectives of resource evaluations, details are required of the geological, mineralogical, and physical properties of the polymetallic deposits and their host rocks. Electrical properties of the deposits and their ore minerals are distinct from their unmineralized host rocks. Therefore, the use of electrical methods to detect SMS while drilling and recovering drill cores could decrease the costs and accelerate offshore operations by limiting the amount of drilling in unmineralized material. This paper presents new data regarding the electrical properties of SMS cores that can be used in that assessment. Frequency-dependent complex electrical resistivity in the frequency range between 0.002 and 100 Hz was examined in order to potentially discriminate between different types of fresh rocks, alteration and mineralization. Forty mini-cores of SMS and unmineralized host rocks were tested in the laboratory, originating from different tectonic settings such as the intermediate-spreading ridges of the Galapagos and Axial Seamount, and the Pacmanus back-arc basin. The results indicate that there is a clear potential to distinguish between mineralized and non-mineralized samples, with some evidence that even different types of mineralization can be discriminated. This could be achieved using resistivity magnitude alone with appropriate rig-mounted electrical sensors. Exploiting the frequency-dependent behavior of resistivity might amplify the differences and further improve the rock characterization.

  1. Antifungal Properties of Electrically Generated Metallic Ions

    PubMed Central

    Berger, T. J.; Spadaro, J. A.; Bierman, Richard; Chapin, S. E.; Becker, R. O.

    1976-01-01

    A qualitative and quantitative investigation was undertaken to study the susceptibility of unicellular eucaryotic organisms (yeasts) to metallic cations generated by low levels of direct current. Results were characteristic of effects obtained previously using clinical and standard bacteria test organisms. The present study demonstrated that anodic silver (Ag+) at low direct currents had inhibitory and fungicidal properties. Broth dilution susceptibility tests were made on several species of Candida and one species of Torulopsis. Growth in all isolates was inhibited by concentrations of electrically generated silver ions between 0.5 and 4.7 μg/ml, and silver exhibited fungicidal properties at concentrations as low as 1.9 μg/ml. The inhibitory and fungicidal concentrations of electrically generated silver ions are lower than those reported for other silver compounds. Images PMID:1034467

  2. Electrical properties of epoxies and film resistors

    NASA Technical Reports Server (NTRS)

    Sergent, J. E.

    1976-01-01

    The reliability of hybrid microcircuits has been enhanced in recent years by the use of organic adhesives as a replacement for solder and eutectics. The epoxies have been the most effective and widely used material for this application. Methods for measuring the electrical and mechanical properties of epoxies are developed. Data are given for selected conductive adhesives at high and low frequencies. The temperature coefficients of resistance of thick film resistors are presented.

  3. Computing Thermodynamic And Transport Properties Of Air

    NASA Technical Reports Server (NTRS)

    Thompson, Richard A.; Gupta, Roop N.; Lee, Kam-Pui

    1994-01-01

    EQAIRS computer program is set of FORTRAN 77 routines for computing thermodynamic and transport properties of equilibrium air for temperatures from 100 to 30,000 K. Computes properties from 11-species, curve-fit mathematical model. Successfully implemented on DEC VAX-series computer running VMS, Sun4-series computer running SunOS, and IBM PC-compatible computer running MS-DOS.

  4. Thermoelectric transport properties of molybdenum from abinitio simulations

    NASA Astrophysics Data System (ADS)

    French, Martin; Mattsson, Thomas R.

    2014-10-01

    We employ abinitio simulations based on density functional theory (DFT) to calculate the electronic transport coefficients (electrical conductivity, thermal conductivity, and thermopower) of molybdenum over a broad range of thermodynamic states. By comparing to available experimental data, we show that DFT is able to describe the desired transport properties of this refractory metal with high accuracy. Most noteworthy, both the positive sign and the quantitative values of the thermopower of solid molybdenum are reproduced very well. We calculate the electrical and thermal conductivity in the solid and the fluid phase between 1000 and 20 000 K and a wide span in density and develop empirical fit formulas for direct use in practical applications, such as magneto-hydrodynamics simulations. The influence of thermal expansion in conductivity measurements at constant pressure is also discussed in some detail.

  5. Thermodynamic and transport properties of fluids

    NASA Technical Reports Server (NTRS)

    Fessler, T. E.

    1980-01-01

    Computer program subroutine FLUID calculates thermodynamic and transport properties of pure fluids in liquid, gas, or two-phase (liquid/gas) conditions. Program determines thermodynamic state from assigned values for temperature and density, pressure and density, temperature and pressure, pressure and entropy, or pressure and enthalpy.

  6. Electronic transport properties in graphene oxide frameworks

    NASA Astrophysics Data System (ADS)

    Zhu, P.; Cruz-Silva, E.; Meunier, V.

    2014-02-01

    The electronic transport properties in multiterminal graphene oxide framework (GOF) materials are investigated using a combination of theoretical and computational methods. GOFs make up four-terminal [origin=c]90H-shaped GNR-L-GNR junctions where sandwiched boronic acid molecules (L) are covalently linked to two graphene nanoribbons (GNRs) of different edge chiralities. The transport properties are governed by both tunneling and quasiresonant regimes. We determine how the presence of linker molecules affects the transport properties and establish that the through-molecule transport properties can be tuned by varying the chemical composition of the pillar molecules but are not significantly modified when changing the type of electrodes from zigzag GNRs to armchair GNRs. In addition, we find that in multilinker systems containing two parallel molecules in the device area, the coupling between the molecules can lead to both constructive and destructive quantum interferences. We also examine the inability of the classical Kirchhoff's superposition law to account for electron flow in multilinker GOF nanonetworks.

  7. Electrical properties of epoxies used in hybrid microelectronics

    NASA Technical Reports Server (NTRS)

    Stout, C. W.

    1976-01-01

    The electrical properties and basic characteristics of the structure of conductive epoxies were studied. The results of the experimental work performed to measure the electrical properties of epoxies are presented.

  8. Electrical properties of polycrystalline methane hydrate

    USGS Publications Warehouse

    Du Frane, W. L.; Stern, L.A.; Weitemeyer, K.A.; Constable, S.; Pinkston, J.C.; Roberts, J.J.

    2011-01-01

    Electromagnetic (EM) remote-sensing techniques are demonstrated to be sensitive to gas hydrate concentration and distribution and complement other resource assessment techniques, particularly seismic methods. To fully utilize EM results requires knowledge of the electrical properties of individual phases and mixing relations, yet little is known about the electrical properties of gas hydrates. We developed a pressure cell to synthesize gas hydrate while simultaneously measuring in situ frequency-dependent electrical conductivity (σ). Synthesis of methane (CH4) hydrate was verified by thermal monitoring and by post run cryogenic scanning electron microscope imaging. Impedance spectra (20 Hz to 2 MHz) were collected before and after synthesis of polycrystalline CH4 hydrate from polycrystalline ice and used to calculate σ. We determined the σ of CH4 hydrate to be 5 × 10−5 S/m at 0°C with activation energy (Ea) of 30.6 kJ/mol (−15 to 15°C). After dissociation back into ice, σ measurements of samples increased by a factor of ~4 and Ea increased by ~50%, similar to the starting ice samples.

  9. Electrical properties of methane hydrate + sediment mixtures

    USGS Publications Warehouse

    Du Frane, Wyatt L.; Stern, Laura A.; Weitemeyer, Karen A.; Constable, Steven; Roberts, Jeffery J.

    2011-01-01

    As part of our DOE-funded proposal to characterize gas hydrate in the Gulf of Mexico using marine electromagnetic methods, a collaboration between SIO, LLNL, and USGS with the goal of measuring the electrical properties of lab-created methane (CH4) hydrate and sediment mixtures was formed. We examined samples with known characteristics to better relate electrical properties measured in the field to specific gas hydrate concentration and distribution patterns. Here we discuss first-ever electrical conductivity (σ) measurements on unmixed CH4 hydrate (Du Frane et al., 2011): 6 x 10-5 S/m at 5 °C, which is ~5 orders of magnitude lower than seawater. This difference allows electromagnetic (EM) techniques to distinguish highly resistive gas hydrate deposits from conductive water saturated sediments in EM field surveys. More recently, we performed measurements on CH4 hydrate mixed with sediment and we also discuss those initial findings here. Our results on samples free of liquid water are important for predicting conductivity of sediments with pores highly saturated with gas hydrate, and are an essential starting point for comprehensive mixing models.

  10. Electrical transport in carbon black-epoxy resin composites at different temperatures

    NASA Astrophysics Data System (ADS)

    Macutkevic, J.; Kuzhir, P.; Paddubskaya, A.; Maksimenko, S.; Banys, J.; Celzard, A.; Fierro, V.; Bistarelli, S.; Cataldo, A.; Micciulla, F.; Bellucci, S.

    2013-07-01

    Results of broadband electric/dielectric properties of different surface area—carbon black/epoxy resin composites above the percolation threshold are reported in a wide temperature range (25-500 K). At higher temperatures (above 400 K), the electrical conductivity of composites is governed by electrical transport in polymer matrix and current carriers tunneling from carbon black clusters to polymer matrix. The activation energy of such processes decreases when the carrier concentration increases, i.e., with the increase of carbon black concentration. At lower temperatures, the electrical conductivity is governed by electron tunneling and hopping. The electrical conductivity and dielectric permittivity of composites strongly decrease after annealing composites at high temperatures (500 K); at the same time potential barrier for carriers tunneling strongly increases. All the observed peculiarities can be used for producing effective low-cost materials on the basis of epoxy resin working at different temperatures for electrical applications.

  11. Transport properties and microstructural characteristics of a thermally cracked mylonite

    NASA Astrophysics Data System (ADS)

    Le Ravalec, M.; Darot, M.; Reuschlé, T.; Guéguen, Y.

    1996-03-01

    An experimental study was carried out on a granitic mylonite (La Bresse, France) to analyze the influence of pore microstructure on transport properties. Different crack networks were obtained by a controlled thermal treatment. Microstructures were analyzed by means of gas adsorption and mercury porosimetry. Transport properties have been investigated by measuring gas permeability and electrical conductivity. The dependence of permeability on confining pressure shows an exponential decrease, characteristic of a porosity made of cracks. Correlations between measured parameters have been analyzed by comparing them with relations deduced from theoretical models. Linking the formation factor to the porosity leads to a rather low tortuosity value (about 2.4), characterizing a medium with a well connected porosity. Correlation between permeability k and formation factor F leads to a power-law relation k ∝ F -n where n≈2.9, which is consistent with a crack model describing the behavior of the thermally treated rock.

  12. Properties of interfaces and transport across them.

    PubMed

    Cabezas, H

    2000-01-01

    Much of the biological activity in cell cytoplasm occurs in compartments some of which may be formed, as suggested in this book, by phase separation, and many of the functions of such compartments depend on the transport or exchange of molecules across interfaces. Thus a fundamentally based discussion of the properties of phases, interfaces, and diffusive transport across interfaces has been given to further elucidate these phenomena. An operational criterion for the width of interfaces is given in terms of molecular and physical arguments, and the properties of molecules inside phases and interfaces are discussed in terms of molecular arguments. In general, the properties of the interface become important when the molecules diffusing across are smaller than the width of the interface. Equilibrium partitioning, Donnan phenomena, and electrochemical potentials at interfaces are also discussed in detail. The mathematical expressions for modeling transport across interfaces are discussed in detail. These describe a practical and detailed model for transport across interfaces. For molecules smaller than the width of the interface, this includes a detailed model for diffusion inside the interface. Last, the question of the time scale for phase formation and equilibration in biological systems is discussed. PMID:10610364

  13. Optical and electrical properties of silicon nanopillars

    SciTech Connect

    Golobokova, L. S. Nastaushev, Yu. V.; Dultsev, F. N.; Kryzhanovskaya, N. V.; Moiseev, E. I.; Kozhukhov, A. S.; Latyshev, A. V.

    2015-07-15

    The electrical and optical properties of silicon nanopillars (Si NPs) are studied. Electron-beam lithography and reactive ion etching are used for the formation of ordered Si-NP arrays. The Si NPs with a diameter from 60 to 340 nm and a height from 218 to 685 nm are formed. The Si NPs are coated with a TiON{sup x} layer with a thickness of 8 nm for chemical and electrical passivation of the surface. Scanning electron microscopy and atomic-force microscopy are used to characterize the obtained structures. The Si-NP arrays acquire various colors when exposed to “bright-field” illumination. The spectra of reflection from the Si-NP arrays in the wavelength range 500–1150 nm are obtained.

  14. Transport properties in the Jovian atmosphere

    NASA Technical Reports Server (NTRS)

    Biolsi, L.

    1978-01-01

    Transport properties in a Jupiter-like atmosphere (89 mol % hydrogen and 11 mol % helium) are obtained by using the method of the kinetic theory of gases. The transport collision integrals are calculated by fitting various two-body semiempirical interaction potentials for which the collision integrals are tabulated to ab initio quantum mechanical calculations of the two-body interactions. The collision integrals are used to calculate the binary diffusion coefficients, viscosity, and 'total' thermal conductivity of the pure gases and the gas mixtures at 1-atm pressure from 1000 K to 25,000 K.

  15. Electrical properties of methane hydrate + sediment mixtures

    NASA Astrophysics Data System (ADS)

    Du Frane, Wyatt L.; Stern, Laura A.; Constable, Steven; Weitemeyer, Karen A.; Smith, Megan M.; Roberts, Jeffery J.

    2015-07-01

    Knowledge of the electrical properties of multicomponent systems with gas hydrate, sediments, and pore water is needed to help relate electromagnetic (EM) measurements to specific gas hydrate concentration and distribution patterns in nature. Toward this goal, we built a pressure cell capable of measuring in situ electrical properties of multicomponent systems such that the effects of individual components and mixing relations can be assessed. We first established the temperature-dependent electrical conductivity (σ) of pure, single-phase methane hydrate to be ~5 orders of magnitude lower than seawater, a substantial contrast that can help differentiate hydrate deposits from significantly more conductive water-saturated sediments in EM field surveys. Here we report σ measurements of two-component systems in which methane hydrate is mixed with variable amounts of quartz sand or glass beads. Sand by itself has low σ but is found to increase the overall σ of mixtures with well-connected methane hydrate. Alternatively, the overall σ decreases when sand concentrations are high enough to cause gas hydrate to be poorly connected, indicating that hydrate grains provide the primary conduction path. Our measurements suggest that impurities from sand induce chemical interactions and/or doping effects that result in higher electrical conductivity with lower temperature dependence. These results can be used in the modeling of massive or two-phase gas-hydrate-bearing systems devoid of conductive pore water. Further experiments that include a free water phase are the necessary next steps toward developing complex models relevant to most natural systems.

  16. Electronic structure and electrical transport in ternary Al-Mg-B films prepared by magnetron sputtering

    SciTech Connect

    Yan, C.; Qian, J. C.; He, B.; Ng, T. W.; Zhang, W. J.; Bello, I.; Jha, S. K.; Zhou, Z. F.; Li, K. Y.; Klemberg-Sapieha, J. E.; Martinu, L.

    2013-03-25

    Nanostructured ternary Al-Mg-B films possess high hardness and corrosion resistance. In the present work, we study their electronic structure and electrical transport. The films exhibit semiconducting characteristics with an indirect optical-bandgap of 0.50 eV, as deduced from the Tauc plots, and a semiconductor behavior with a Fermi level of {approx}0.24 eV below the conduction band. Four-probe and Hall measurements indicated a high electrical conductivity and p-type carrier mobility, suggesting that the electrical transport is mainly due to hole conduction. Their electrical properties are explained in terms of the film nanocomposite microstructure consisting of an amorphous B-rich matrix containing AlMgB{sub 14} nanoparticles.

  17. Photoinduced Charge Transport in a BHJ Solar Cell Controlled by an External Electric Field

    PubMed Central

    Li, Yongqing; Feng, Yanting; Sun, Mengtao

    2015-01-01

    This study investigated theoretical photoinduced charge transport in a bulk heterojunction (BHJ) solar cell controlled by an external electric field. Our method for visualizing charge difference density identified the excited state properties of photoinduced charge transfer, and the charge transfer excited states were distinguished from local excited states during electronic transitions. Furthermore, the calculated rates for the charge transfer revealed that the charge transfer was strongly influenced by the external electric field. The external electric field accelerated the rate of charge transfer by up to one order when charge recombination was significantly restrained. Our research demonstrated that photoinduced charge transport controlled by an external electric field in a BHJ solar cell is efficient, and the exciton dissociation is not the limiting factor in organic solar cells.Our research should aid in the rational design of a novel conjugated system of organic solar cells. PMID:26353997

  18. Temperature Dependent Electrical Properties of PZT Wafer

    NASA Astrophysics Data System (ADS)

    Basu, T.; Sen, S.; Seal, A.; Sen, A.

    2016-04-01

    The electrical and electromechanical properties of lead zirconate titanate (PZT) wafers were investigated and compared with PZT bulk. PZT wafers were prepared by tape casting technique. The transition temperature of both the PZT forms remained the same. The transition from an asymmetric to a symmetric shape was observed for PZT wafers at higher temperature. The piezoelectric coefficient (d 33) values obtained were 560 pc/N and 234 pc/N, and the electromechanical coupling coefficient (k p) values were 0.68 and 0.49 for bulk and wafer, respectively. The reduction in polarization after fatigue was only ~3% in case of PZT bulk and ~7% for PZT wafer.

  19. Electric current induced forward and anomalous backward mass transport

    NASA Astrophysics Data System (ADS)

    Somaiah, Nalla; Sharma, Deepak; Kumar, Praveen

    2016-05-01

    Multilayered test samples were fabricated in form of standard Blech structure, where W was used as the interlayer between SiO2 substrate and Cu film. Electromigration test was performed at 250 °C by passing an electric current with a nominal density of 3.9  ×  1010 A m‑2. In addition to the regular electromigration induced mass transport ensuing from the cathode towards the anode, we also observed anomalous mass transport from the anode to the cathode, depleting Cu from the anode as well. We propose an electromigration-thermomigration coupling based reasoning to explain the observed mass transport.

  20. A transition in mechanisms of size dependent electrical transport at nanoscale metal-oxide interfaces

    SciTech Connect

    Hou, Jiechang; Nonnenmann, Stephen S.; Qin, Wei; Bonnell, Dawn A.

    2013-12-16

    As device miniaturization approaches nanoscale dimensions, interfaces begin to dominate electrical properties. Here the system archetype Au/SrTiO{sub 3} is used to examine the origin of size dependent transport properties along metal-oxide interfaces. We demonstrate that a transition between two classes of size dependent electronic transport mechanisms exists, defined by a critical size ε. At sizes larger than ε an edge-related tunneling effect proportional to 1/D (the height of the supported Au nanoparticle) is observed; interfaces with sizes smaller than ε exhibit random fluctuations in current. The ability to distinguish between these mechanisms is important to future developments in nanoscale device design.

  1. Investigations of Persistent Photoconductivity of Cadmium Sulfide at T = 1-20K: Structure of the Photo - Defect, Transport Properties, and Electric Current Instabilities Associated with Thermal Transport to a Liquid Helium-Ii Film.

    NASA Astrophysics Data System (ADS)

    Dong, Mouqun

    The nature of stored charge and the electric conduction mechanism, two important aspects of persistent photoconductivity (PPC), have been investigated in CdS at low temperatures. A persistent photo-induced electron spin resonance (ESR) center was found for the first time. Correlations between buildups of PPC, edge luminescence and ESR absorption suggest the same charge transfer process responsible for all of the phenomena. Analysis of the ESR spectra indicates that the ESR center is a hole on a sulphur site with a neighboring cadmium-vacancy. From its correlation with luminescence and PPC, this ESR defect is deduced to constitute the acceptor in edge luminescence, which had never previously been conclusively identified. The most probable mechanism for the persistence of both the PPC and the ESR signals is concluded to be the random potential barrier model. Existent theories of hopping conduction are consistent with most aspects of the PPC, for which detailed measurements on the temperature dependence and magnetoresistance were taken. However, for complete quantitative agreement, correction factors of non-understood origin are utilized. An instability in I-V characteristic of PPC, which was first observed in this lab, has been solved by a model of heat transfer between the interface of CdS and He-II film. The observed S-shaped I-V curve can be accounted for by this model quantitatively. Two related effects, anomalous power dependence of the Kapitza resistance and peak heat flux associated with a helium film evaporation mechanism have also been addressed.

  2. Transport properties in periodically modulated zigzag silicene nanoribbon

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Shuang; Shen, Man; An, Xing-Tao; Liu, Jian-Jun

    2016-04-01

    We study theoretically the electronic transport properties of zigzag silicene nanoribbon superlattices subject to a periodic electric field perpendicular to the surface of silicene. Our results show that the conductivity of the system depends on the superlattice structural parameters and show effects analogous to those found with two-dimensional semiconductor superlattices. For a superlattice with Nb barriers, a series of resonant peaks, each of which is split into (Nb - 1) subpeaks, and transmission blockade regions appear in the conductance spectrum, which indicates the formation of minibands and minigaps. These silicene-based quantum structures can provide concepts for the design nanodevices.

  3. Electrical Power Systems for NASA's Space Transportation Program

    NASA Technical Reports Server (NTRS)

    Lollar, Louis F.; Maus, Louis C.

    1998-01-01

    Marshall Space Flight Center (MSFC) is the National Aeronautics and Space Administration's (NASA) lead center for space transportation systems development. These systems include earth to orbit launch vehicles, as well as vehicles for orbital transfer and deep space missions. The tasks for these systems include research, technology maturation, design, development, and integration of space transportation and propulsion systems. One of the key elements in any transportation system is the electrical power system (EPS). Every transportation system has to have some form of electrical power and the EPS for each of these systems tends to be as varied and unique as the missions they are supporting. The Preliminary Design Office (PD) at MSFC is tasked to perform feasibility analyses and preliminary design studies for new projects, particularly in the space transportation systems area. All major subsystems, including electrical power, are included in each of these studies. Three example systems being evaluated in PD at this time are the Liquid Fly Back Booster (LFBB) system, the Human Mission to Mars (HMM) study, and a tether based flight experiment called the Propulsive Small Expendable Deployer System (ProSEDS). These three systems are in various stages of definition in the study phase.

  4. Electrical properties of epoxy/silver nanocomposites

    NASA Astrophysics Data System (ADS)

    Gonon, P.; Boudefel, A.

    2006-01-01

    We investigated the electrical properties of nanocomposites made of epoxy resin filled with 70-nm-sized silver particles. These composites were studied for the fabrication of integrated capacitors in electronics packaging. The dc conductivity was studied as a function of the filler concentration and as a function of temperature. We also studied the ac conductivity and the permittivity in the 10-1-105 Hz range as a function of the filler concentration. Experimental properties were analyzed using standard percolation theories. The dc conductivity varies as (φ-φc)t, where φ is the filler concentration, φc is the percolation threshold, and t is the dc critical exponent. A very low percolation threshold is obtained (φc=1%) which is believed to be related to a segregated distribution of the fillers in the epoxy matrix. We also measured a very high dc critical exponent (t=5) probably related to the interparticle electrical contact. A universal scaling law is observed for σ(ω) and ɛ(ω). Above a cutoff frequency (ωc, which scales with the dc conductivity as ωc~σdcq) the conductivity and the permittivity follow the universal power laws (σ~ωu and V~ω-v) with critical exponents taking nonstandard values (q=0.83-0.98, u=0.79, and v=0.03).

  5. Controlling Defects in Graphene for Optimizing the Electrical Properties of Graphene Nanodevices

    PubMed Central

    2015-01-01

    Structural defects strongly impact the electrical transport properties of graphene nanostructures. In this Perspective, we give a brief overview of different types of defects in graphene and their effect on transport properties. We discuss recent experimental progress on graphene self-repair of defects, with a focus on in situ transmission electron microscopy studies. Finally, we present the outlook for graphene self-repair and in situ experiments. PMID:25864552

  6. Effect of External Electric Field on Substrate Transport of a Secondary Active Transporter.

    PubMed

    Zhang, Ji-Long; Zheng, Qing-Chuan; Yu, Li-Ying; Li, Zheng-Qiang; Zhang, Hong-Xing

    2016-08-22

    Substrate transport across a membrane accomplished by a secondary active transporter (SAT) is essential to the normal physiological function of living cells. In the present research, a series of all-atom molecular dynamics (MD) simulations under different electric field (EF) strengths was performed to investigate the effect of an external EF on the substrate transport of an SAT. The results show that EF both affects the interaction between substrate and related protein's residues by changing their conformations and tunes the timeline of the transport event, which collectively reduces the height of energy barrier for substrate transport and results in the appearance of two intermediate conformations under the existence of an external EF. Our work spotlights the crucial influence of external EFs on the substrate transport of SATs and could provide a more penetrating understanding of the substrate transport mechanism of SATs. PMID:27472561

  7. Thermoelectric transport properties of In2Se3 single crystal

    NASA Astrophysics Data System (ADS)

    Nguyen, Thi Huong; Duong, Van Thiet; Nguyen, Van Quang; Duong, Anh Tuan; Cho, Sunglae; Song, Jae Yong; Park, Hyun-Min

    In recent years the discovery and development of green energy source are one of the top concerns in science. The enormous efforts have been devoted to search for thermoelectric materials. Enhancement of thermoelectric figure of merit (ZT = (S2 σ / κ) T) is currently research goal of scientists. In2Se3 is one of semiconductors with layered structure, which is good for thermoelectric applications. In this study, we report on the transport and thermoelectric properties of In2Se3 single crystal. The layered crystal structure of In2Se3 was determined by XRD and FE-SEM measurements. Ellipsometry measurement illustrated the indirect band gap of In2Se3, about 1.61 eV. Transport properties have been studied in the temperature range from 20 to 400 K along axis which is parallel to the layers direction. Interestingly, Seebeck coefficient was n-type and increased with temperature and the electrical conductivity increased with temperature. Therefore, power factor increased up to 2.69 µWcm-1K-2at 400 K. In this talk, we will discuss more on transport properties.

  8. Optical and transport properties of dense liquid silica

    SciTech Connect

    Qi, Tingting; Millot, Marius; Kraus, Richard G.; Hamel, Sebastien; Root, Seth

    2015-06-15

    Using density-functional-theory based molecular dynamics and the Kubo-Greenwood linear response theory, we evaluated the high-pressure equation of state and the optical and transport properties of quartz and fused silica shock-compressed to 2000 GPa. The computed Hugoniots and corresponding optical reflectivity values are in very good agreement with published data for quartz, and new data that we obtained on fused silica using magnetically launched flyer plate experiments. The rise of optical reflectivity upon shock compression appears to be primarily a temperature-driven mechanism, which is relatively insensitive to small density variation. We observed that the electrical conductivity does not display Drude-like frequency dependence, especially at lower temperatures. In addition, the Wiedemann-Franz relation between electrical and thermal conductivities was found to be invalid. It suggests that even at three-fold compression, warm dense liquid silica on the Hugoniot curve is still far away from the degenerate limit.

  9. Transport Properties of n-POLYANILINE/p-POROUS Silicon Heterojunctions

    NASA Astrophysics Data System (ADS)

    Farag, A. A. M.; Ashery, A.; Yahia Abed, M.; Shenashen, M. A.; Hindia, T. A.

    The donor/acceptor heterojunction devices having configuration n-PANI/p-PSi were fabricated by in-situ chemical oxidative polymerization method of aniline on p-type porous silicon. The structure of n-PANI/p-PSi junctions was examined by scanning electron microscopy and X-ray diffraction spectroscopy. The dark current-voltage measurements were performed in the temperature range of 303-393 K to determine the electrical transport mechanisms of these devices. Rectifying properties were obtained and capacitance-voltage at 1 MHz behavior indicates an abrupt interface. At low forward bias, the current was found to be limited by thermionic emission of holes from p-PSi over the PANI/PSi barrier in the PANI thin film. For relatively higher voltage, the conduction was dominated by a space charge limited current mechanism, with an exponential distribution of traps. Also, various electrical parameters were determined from the I-V and C-V analysis.

  10. Optical and transport properties of dense liquid silica

    NASA Astrophysics Data System (ADS)

    Qi, Tingting; Millot, Marius; Kraus, Richard G.; Root, Seth; Hamel, Sebastien

    2015-06-01

    Using density-functional-theory based molecular dynamics and the Kubo-Greenwood linear response theory, we evaluated the high-pressure equation of state and the optical and transport properties of quartz and fused silica shock-compressed to 2000 GPa. The computed Hugoniots and corresponding optical reflectivity values are in very good agreement with published data for quartz, and new data that we obtained on fused silica using magnetically launched flyer plate experiments. The rise of optical reflectivity upon shock compression appears to be primarily a temperature-driven mechanism, which is relatively insensitive to small density variation. We observed that the electrical conductivity does not display Drude-like frequency dependence, especially at lower temperatures. In addition, the Wiedemann-Franz relation between electrical and thermal conductivities was found to be invalid. It suggests that even at three-fold compression, warm dense liquid silica on the Hugoniot curve is still far away from the degenerate limit.

  11. Electrical and optical properties of carbon films

    NASA Astrophysics Data System (ADS)

    Kulkarni, Pranita

    the morphology and graphitic cluster sizes that were obtained from Raman scattering. To enable the development of future devices based on nanostructured carbon films, four metals (Zr, Ti, Cu, and Pt) with substantially different work functions and catalytic activity were deposited on pyrolyzed PAN-b-PBA films. All metals formed ohmic contacts to the films in the 'as-deposited' state with contact resistances of the order of 105 O. The ohmicity of all metals and the modulation of the pseudo-gap with graphitic cluster sizes were explained using the simple single-orbital tight-binding calculations for nanometer-sized graphitic clusters. Unlike most inorganic single-crystal semiconductors but commonly observed in organic or nanocrystalline materials, our modeling of resistivity-temperature measurements showed that variable-range-hopping (VRH) was the dominant current transport mechanism in the films up to room-temperature with a crossover from Mott-VRH to Efros-Skhlovskii-VRH at temperatures below 100 K. Specific contact resistivity values for all metal-copolymer (PAN-b-PBA)-derived films pyrolyzed at 600°C increased with increasing work function of the metal, suggesting that the films are n-type; this conclusion agrees with the n-type result obtained from the Hall-effect measurements. Nanocrystalline diamond (NCD) films have a variety of potential applications, including optical windows, Schottky diodes, and electron emitting surfaces for field emission displays. In this study Zr, Ti, Cu and Pt on intrinsic and lightly sulfur-doped (n-type) NCD films were characterized electrically and photoelectrically. All metals showed linear (ohmic) current-voltage characteristics in the as-deposited state. The Schottky barrier heights (phiB) at the metal-film interface were investigated using x-ray and ultra-violet photoelectron spectroscopy. The undoped NCD films exhibited a negative electron affinity and a band gap of 5.0 +/- 0.4 eV. The phiB were calculated based on this band gap

  12. Transport properties of individual C{sub 60}-molecules

    SciTech Connect

    Géranton, G.; Seiler, C.; Evers, F.; Bagrets, A.; Venkataraman, L.

    2013-12-21

    Electrical and thermal transport properties of C{sub 60} molecules are investigated with density-functional-theory based calculations. These calculations suggest that the optimum contact geometry for an electrode terminated with a single-Au atom is through binding to one or two C-atoms of C{sub 60} with a tendency to promote the  sp{sup 2}-hybridization into an  sp{sup 3}-type one. Transport in these junctions is primarily through an unoccupied molecular orbital that is partly hybridized with the Au, which results in splitting the degeneracy of the lowest unoccupied molecular orbital triplet. The transmission through these junctions, however, cannot be modeled by a single Lorentzian resonance, as our results show evidence of quantum interference between an occupied and an unoccupied orbital. The interference results in a suppression of conductance around the Fermi energy. Our numerical findings are readily analyzed analytically within a simple two-level model.

  13. Transport properties of the hot and dense sQGP

    NASA Astrophysics Data System (ADS)

    Berrehrah, H.; Bratkovskaya, E.; Cassing, W.; Marty, R.

    2015-05-01

    The transport properties of the quark gluon plasma (QGP) are studied in a QCD medium at finite temperature and chemical potential. We calculate the shear viscosity η(T,μq) and the electric conductivity σe(T, μq) for a system of interacting massive and broad quasi-particles as described by the dynamical quasi-particle model “DQPM” at finite temperature T and quark chemical potential μq within the relaxation time approximation. Our results are in a good agreement with lattice QCD at finite temperature and show clearly the increase of the transport coefficients with increasing T and μq. Our results provide the basic ingredients for the study of the hot and dense matter in the Beam Energy Scan (BES) at RHIC and CBM at FAIR.

  14. Thermodynamic and transport properties of gaseous tetrafluoromethane in chemical equilibrium

    NASA Technical Reports Server (NTRS)

    Hunt, J. L.; Boney, L. R.

    1973-01-01

    Equations and in computer code are presented for the thermodynamic and transport properties of gaseous, undissociated tetrafluoromethane (CF4) in chemical equilibrium. The computer code calculates the thermodynamic and transport properties of CF4 when given any two of five thermodynamic variables (entropy, temperature, volume, pressure, and enthalpy). Equilibrium thermodynamic and transport property data are tabulated and pressure-enthalpy diagrams are presented.

  15. Geophysical and transport properties of reservoir rocks. Summary annual report

    SciTech Connect

    Cook, N.G.W.

    1990-04-29

    Definition of petrophysical properties, such as porosity, permeability and fluid saturation, on the scale of meters, is the key to planning and control of successful Enhanced Oil Recovery techniques for domestic reservoirs. Macroscopic transport properties in reservoir rocks depend critically upon processes at the pore level involving interactions between the pore topology and the physical and chemical properties of the rock minerals and interstitial fluids. Similar interactions at the pore level determine also the macroscopic electrical and seismic properties of reservoir rocks. The objective of this research is to understand, using analysis and experiment, how fluids in pores affect the geophysical and sport properties of reservoir rocks. The goal is to develop equations-relating seismic and electrical properties of rock to the porosity, permeability and fluid saturations so as to invert geophysical images for improved reservoir management. Results from seismic measurements performed so far in this study suggest that even subtle changes in fluid contacts and the in-situ state of effective stress can be detected using geophysical imaging techniques. The experiments using Wood`s metal and wax are revealing the topology and sport properties of the pore space in clastic sedimentary rocks. A deeper understanding of these properties is considered-to be the key to the recovery of much of the mobile oil left in domestic reservoirs and to the effective management of enhanced oil recovery techniques. The results of Wood`s metal percolation tests indicate that most of the permeability of Berea sandstone resides in the critical percolating paths and these paths occupy only a small fraction of the total porosity. This result may have important implications for flooding in terms of override and efficiency as a function of saturation.

  16. Predicting the transport properties of sedimentary rocks from microstructure

    SciTech Connect

    Schlueter, E.M.

    1995-01-01

    Understanding transport properties of sedimentary rocks, including permeability, relative permeability, and electrical conductivity, is of great importance for petroleum engineering, waste isolation, environmental restoration, and other applications. These transport properties axe controlled to a great extent by the pore structure. How pore geometry, topology, and the physics and chemistry of mineral-fluid and fluid-fluid interactions affect the flow of fluids through consolidated/partially consolidated porous media are investigated analytically and experimentally. Hydraulic and electrical conductivity of sedimentary rocks are predicted from the microscopic geometry of the pore space. Cross-sectional areas and perimeters of individual pores are estimated from two-dimensional scanning electron microscope (SEM) photomicrographs of rock sections. Results, using Berea, Boise, Massilon, and Saint-Gilles sandstones show close agreement between the predicted and measured permeabilities. Good to fair agreement is found in the case of electrical conductivity. In particular, good agreement is found for a poorly cemented rock such as Saint-Gilles sandstone, whereas the agreement is not very good for well-cemented rocks. The possible reasons for this are investigated. The surface conductance contribution of clay minerals to the overall electrical conductivity is assessed. The effect of partial hydrocarbon saturation on overall rock conductivity, and on the Archie saturation exponent, is discussed. The region of validity of the well-known Kozeny-Carman permeability formulae for consolidated porous media and their relationship to the microscopic spatial variations of channel dimensions are established. It is found that the permeabilities predicted by the Kozeny-Carman equations are valid within a factor of three of the observed values methods.

  17. Engineering electrical properties of graphene: chemical approaches

    NASA Astrophysics Data System (ADS)

    Kim, Yong-Jin; Kim, Yuna; Novoselov, Konstantin; Hong, Byung Hee

    2015-12-01

    To ensure the high performance of graphene-based devices, it is necessary to engineer the electrical properties of graphene with enhanced conductivity, controlled work function, opened or closed bandgaps, etc. This can be performed by various non-covalent chemical approaches, including molecular adsorption, substrate-induced doping, polymerization on graphene, deposition of metallic thin films or nanoparticles, etc. In addition, covalent approaches such as the substitution of carbon atoms with boron or nitrogen and the functionalization with hydrogen or fluorine are useful to tune the bandgaps more efficiently, with better uniformity and stability. In this review, representative examples of chemically engineered graphene and its device applications will be reviewed, and remaining challenges will be discussed.

  18. Spin Dependent Transport Properties of Metallic and Semiconducting Nanostructures

    NASA Astrophysics Data System (ADS)

    Sapkota, Keshab R.

    Present computing and communication devices rely on two different classes of technologies; information processing devices are based on electrical charge transport in semiconducting materials while information storage devices are based on orientation of electron spins in magnetic materials. A realization of a hybrid-type device that is based on charge as well as spin properties of electrons would perform both of these actions thereby enhancing computation power to many folds and reducing power consumptions. This dissertation focuses on the fabrication of such spin-devices based on metallic and semiconducting nanostructures which can utilize spin as well as charge properties of electrons. A simplified design of the spin-device consists of a spin injector, a semiconducting or metallic channel, and a spin detector. The channel is the carrier of the spin signal from the injector to the detector and therefore plays a crucial role in the manipulation of spin properties in the device. In this work, nanostructures like nanowires and nanostripes are used to function the channel in the spin-device. Methods like electrospinning, hydrothermal, and wet chemical were used to synthesize nanowires while physical vapor deposition followed by heat treatment in controlled environment was used to synthesis nanostripes. Spin-devices fabrication of the synthesized nanostructures were carried out by electron beam lithography process. The details of synthesis of nanostructures, device fabrication procedures and measurement techniques will be discussed in the thesis. We have successfully fabricated the spin-devices of tellurium nanowire, indium nanostripe, and indium oxide nanostripe and studied their spin transport properties for the first time. These spin-devices show large spin relaxation length compared to normal metals like copper and offer potentials for the future technologies. Further, Heusler alloys nanowires like nanowires of Co 2FeAl were synthesized and studied for electrical

  19. The influence of edge defects on the electrical and thermal transport of graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Izadi Vishkayi, Sahar; Rahimpour Soleimani, Hamid

    2015-11-01

    The electrical conductance, thermopower, thermal conductance and figure of merit of graphene nanoribbons (GNRs) are investigated using Green function formalism in the linear response regime. The Hamiltonian of GNR is described by the tight-binding approach and the effect of elastic interactions due to the electron-electron interaction or the thermal environmental fluctuations is considered by dephasing approach within the self-consistent Born approximation. The results show that the dephasing process leads to the reduction of the electrical transport of GNRs. Since the edge configuration of GNRs has the significant role in their electronic properties, it is shown that the electrical and thermal transports of the GNRs are decreased by the edge defects while the reduction of thermal conductance is more efficient, therefore, the thermal efficiency of GNRs is increased.

  20. Electronic transport properties of silicon clusters

    NASA Astrophysics Data System (ADS)

    Matsuura, Yukihito

    2016-02-01

    The electronic transport properties of silicon clusters were examined via theoretical calculations using the first-principles method. Additionally, p-type doping and n-type doping were analyzed by calculating conductance and current of boron- and phosphorus-doped silicon clusters. The p-type doping and n-type doping provided a new transmission peak at an energy level around the Fermi level to increase conductance. Furthermore, simultaneous boron and phosphorus doping resulted in noticeable rectifying characteristics, with the current drive in forward bias being three times higher than that in the reverse bias. A p-n junction was achieved even on a molecular scale.

  1. Spectrophotometric and electrical properties of imperatorin: an organic molecule

    NASA Astrophysics Data System (ADS)

    Mir, Feroz A.

    2015-09-01

    Imperatorin (molecular formula = C16H14O4, molecular mass = 270) an organic molecule was isolated from ethyl acetate extract of the root parts of the plant Prangos pabularia. The optical study was carried out by ultraviolet-visible spectroscopy, and this compound showed an indirect allowed transition. The optical band gap ( E g ) was found around 3.75 eV. Photoluminescence shows various good emission bands. The frequency-dependent real part of the complex ac conductivity was found to follow the universal dielectric response: σ ac ( ω) α ω s [where σ ac ( ω) is the frequency-dependent total conductivity, ω is the frequency, and s is the frequency exponent]. From ac conductivity data analysis, correlated barrier hopping charge-transport mechanism is the dominant electrical transport process shown by this compound. The good emission, less absorption, wide band gap and good electrical properties shown by this compound project them as a bright choice for organic electronic devices.

  2. Spatially resolved imaging of opto-electrical property variations

    SciTech Connect

    Nikiforov, Maxim; Darling, Seth B; Suzer, Ozgun; Guest, Jeffrey; Roelofs, Andreas

    2014-09-16

    Systems and methods for opto electric properties are provided. A light source illuminates a sample. A reference detector senses light from the light source. A sample detector receives light from the sample. A positioning fixture allows for relative positioning of the sample or the light source with respect to each other. An electrical signal device measures the electrical properties of the sample. The reference detector, sample detector and electrical signal device provide information that may be processed to determine opto-electric properties of the same.

  3. Predicting the transport properties of sedimentary rocks from microgeometry

    SciTech Connect

    Schlueter, E.M.

    1993-01-01

    We investigate through analysis and experiment how pore geometry, topology, and the physics and chemistry of mineral-fluid and fluid-fluid interactions affect the flow of fluids through consolidated/partially consolidated porous media. Our approach is to measure fluid permeability and electrical conductivity of rock samples using single and multiple fluid phases that can be frozen in place (wetting and nonwetting) over a range of pore pressures. These experiments are analyzed in terms of the microphysics and microchemistry of the processes involved to provide a theoretical basis for the macroscopic constitutive relationships between fluid-flow and geophysical properties that we develop. The purpose of these experiments and their analyses is to advance the understanding of the mechanisms and factors that control fluid transport in porous media. This understanding is important in characterizing porous media properties and heterogeneities before simulating and monitoring the progress of complex flow processes at the field scale in permeable media.

  4. Predicting the transport properties of sedimentary rocks from microgeometry

    SciTech Connect

    Schlueter, E.M.

    1995-02-01

    The author investigates through analysis and experiment how pore geometry, topology, and the physics and chemistry of mineral-fluid and fluid-fluid interactions affect the flow of fluids through consolidated/partially consolidated porous media. The approach is to measure fluid permeability and electrical conductivity of rock samples using single and multiple fluid phases that can be frozen in place (wetting and nonwetting) over a range of pore pressures. These experiments are analyzed in terms of the microphysics and microchemistry of the processes involved to provide a theoretical basis for the macroscopic constitutive relationships between fluid-flow and geophysical properties that the authors develop. The purpose of these experiments and their analyses is to advance the understanding of the mechanisms and factors that control fluid transport in porous media. This understanding is important in characterizing porous media properties and heterogeneities before simulating and monitoring the progress of complex flow processes at the field scale in permeable media.

  5. Control of photon transport properties in nanocomposite nanowires

    NASA Astrophysics Data System (ADS)

    Moffa, M.; Fasano, V.; Camposeo, A.; Persano, L.; Pisignano, D.

    2016-02-01

    Active nanowires and nanofibers can be realized by the electric-field induced stretching of polymer solutions with sufficient molecular entanglements. The resulting nanomaterials are attracting an increasing attention in view of their application in a wide variety of fields, including optoelectronics, photonics, energy harvesting, nanoelectronics, and microelectromechanical systems. Realizing nanocomposite nanofibers is especially interesting in this respect. In particular, methods suitable for embedding inorganic nanocrystals in electrified jets and then in active fiber systems allow for controlling light-scattering and refractive index properties in the realized fibrous materials. We here report on the design, realization, and morphological and spectroscopic characterization of new species of active, composite nanowires and nanofibers for nanophotonics. We focus on the properties of light-confinement and photon transport along the nanowire longitudinal axis, and on how these depend on nanoparticle incorporation. Optical losses mechanisms and their influence on device design and performances are also presented and discussed.

  6. Graphene on graphene antidot lattices: Electronic and transport properties

    NASA Astrophysics Data System (ADS)

    Gregersen, Søren Schou; Pedersen, Jesper Goor; Power, Stephen R.; Jauho, Antti-Pekka

    2015-03-01

    Graphene bilayer systems are known to exhibit a band gap when the layer symmetry is broken by applying a perpendicular electric field. The resulting band structure resembles that of a conventional semiconductor with a parabolic dispersion. Here, we introduce a bilayer graphene heterostructure, where single-layer graphene is placed on top of another layer of graphene with a regular lattice of antidots. We dub this class of graphene systems GOAL: graphene on graphene antidot lattice. By varying the structure geometry, band-structure engineering can be performed to obtain linearly dispersing bands (with a high concomitant mobility), which nevertheless can be made gapped with a perpendicular field. We analyze the electronic structure and transport properties of various types of GOALs, and draw general conclusions about their properties to aid their design in experiments.

  7. Local structural distortion and electrical transport properties of Bi(Ni1/2Ti1/2)O3 perovskite under high pressure

    SciTech Connect

    Zhu, Jinlong; Yang, Liuxiang; Wang, Hsiu -Wen; Zhang, Jianzhong; Yang, Wenge; Hong, Xinguo; Jin, Changqing; Zhao, Yusheng

    2015-12-16

    Perovskite-structure materials generally exhibit local structural distortions that are distinct from long-range, average crystal structure. The characterization of such distortion is critical to understanding the structural and physical properties of materials. In this work, we combined Pair Distribution Function (PDF) technique with Raman spectroscopy and electrical resistivity measurement to study Bi(Ni1/2Ti1/2)O3 perovskite under high pressure. PDF analysis reveals strong local structural distortion at ambient conditions. As pressure increases, the local structure distortions are substantially suppressed and eventually vanish around 4 GPa, leading to concurrent changes in the electronic band structure and anomalies in the electrical resistivity. We find, consistent with PDF analysis, Raman spectroscopy data suggest that the local structure changes to a higher ordered state at pressures above 4 GPa.

  8. Electric Transport Traction Power Supply System With Distributed Energy Sources

    NASA Astrophysics Data System (ADS)

    Abramov, E. Y.; Schurov, N. I.; Rozhkova, M. V.

    2016-04-01

    The paper states the problem of traction substation (TSS) leveling of daily-load curve for urban electric transport. The circuit of traction power supply system (TPSS) with distributed autonomous energy source (AES) based on photovoltaic (PV) and energy storage (ES) units is submitted here. The distribution algorithm of power flow for the daily traction load curve leveling is also introduced in this paper. In addition, it illustrates the implemented experiment model of power supply system.

  9. Surface electrical properties experiment, part 1. [for measuring lunar surface electrical properties

    NASA Technical Reports Server (NTRS)

    Kupfer, W. S. (Compiler)

    1973-01-01

    The design evolution, hardware development, and production history of the surface electrical properties (SEP) experiment are discussed. The SEP transmitter and receiver were designed to be used on the lunar surface during the Apollo 17 mission. The equipment was used to measure lunar surface electrical properties over traverses totalling more than 8 kilometers, for a duration of more than 100 minutes. A comprehensive outline of the techniques, is given along with a simplified detailed breakdown of equipment description and function to outline the principles of operation. A history of the design evolution with trade-off criteria and emphasis on changes caused by decisions reached in solving problems inherent in a fast-paced development program are presented from the viewpoint of overall design concept and in detail for each item of deliverable hardware. There is a brief account of lunar operations.

  10. Electrical and optical properties of p-type InN

    SciTech Connect

    Mayer, Marie A.; Choi, Soojeong; Bierwagen, Oliver; Smith, Holland M.; Haller, Eugene E.; Speck, James S.; Walukiewicz, Wladek

    2011-01-01

    We have performed comprehensive studies of optical, thermoelectric and electrical properties of Mg doped InN with varying Mg doping levels and sample thicknesses. Room temperature photoluminescence spectra show a Mg acceptor related emission and the thermopower provides clear evidence for the presence of mobile holes. Although the effects of the hole transport are clearly observed in the temperature dependent electrical properties, the sign of the apparent Hall coefficient remains negative in all samples. We show that the standard model of two electrically well connected layers (n-type surface electron accumulation and p-type bulk) does not properly describe Hall effect in p-type InN.

  11. Optical, Electrical and Catalytic Properties Of Titania Nanotubes

    NASA Astrophysics Data System (ADS)

    AbdElmoula, Mohamed

    In past decades revolutionary developments took place in many aspects of science. One of the leading developments is in the field of material science where there is great interest in developing new materials for various applications. Massive number of applications will change the entire life of mankind on earth and in space. Nanomaterials science is considered the pioneer in this new era. Titania nanotube is considered a very important material due to its promising applications in many fields ranging from energy harvesting to sensors and photocatalytic applications. Electrochemical anodization method is used to fabricate titania nanotube arrays, this method is preferred than other methods for many reasons, for example it has good degree of controlling tube length, tube diameter and tube wall thickness. In addition to controlling tube parameter this method provides a scalable, easy and cheap technique for future industrial applications. My work in this thesis is focused on this kind of nanotubes arrays. In this dissertation we will provide an introduction to fabrication of titania nanotube arrays. We will provide an overview about the reported methods of fabrication and the advantage of each method. Also we will describe some anticipated application and the challenges to make these nanotubes functional and efficient. Secondly, we will carry out a comprehensive study of the electrical transport of a single titania nanotube, where we have been able to study for the first time the electrical transport properties of a single titania nanotube using E-beam Lithography technique. Also we will explore parameters that affect these transport properties such as annealing conditions and the morphology of the nanotube. We will describe a study of the optical properties of free standing titania nanotube arrays, where we will investigate the transmission, reflection and absorption of electromagnetic spectrum from 300nm to 1000nm (which cover the infrared, visible light and ultra

  12. Structural and electrical properties of polymorphic pentacene thin films

    NASA Astrophysics Data System (ADS)

    Stadlober, Barbara; Satzinger, Valentin; Maresch, Hannes; Somitsch, Dieter; Haase, Anja; Pichler, Heinz; Rom, Werner; Jakopic, Georg

    2003-11-01

    Due to its outstanding carrier transport capabilities the aromatic hydrocarbon pentacene is still one of the most promising out of all organic semiconducting materials investigated so far. Pentacene appears in several polymorphic structures that significantly differ with respect to the d(001) spacing. It is shown, that precise control of the epitaxial growth process of thin films enables not only to adjust the formation of the polymorphic phases, but also to influence grain size and shape. The relative volume fraction of the pentacene polymorphs is determined by several parameters which are substrate material, deposition rate, film thickness and substrate temperature. A comparison of X-ray diffraction and Raman measurements reveals that the phase with the smaller layer-by-layer spacing grows on top of the other]. Moreover, there is a strict correlation between evaporation rate and maximum grain size. In addition to structural we also investigated the electrical properties of pentacene thin films focussing on polymorphism and its influence on the transport properties. Apart from the fact that the charge carrier mobility is strongly influenced by the grain size it turned out that the bulk phase is related to a lower intrinisic mobility than the thin film phase.

  13. Charged Hadron Properties in Background Electric Fields

    SciTech Connect

    William Detmold, Brian C. Tiburzi, Andre Walker-Loud

    2010-02-01

    We report on a lattice calculation demonstrating a novel new method to extract the electric polarizability of charged pseudo-scalar mesons by analyzing two point correlation functions computed in classical background electric fields.

  14. Magnetic and electrical transport properties of La0.65Ca0.30Pb0.05Mn0.90Cu0.10O3 compounds: Thermal hysteresis

    NASA Astrophysics Data System (ADS)

    Irmak, A. E.; Taşarkuyu, E.; Coşkun, A.; Acet, M.; Samancıoğlu, Y.; Aktürk, S.

    2015-08-01

    Structural, electrical, and magnetic properties of La0.65(Ca0.30Pb0.05)Mn0.90Cu0.10O3 compound were investigated. The compound, prepared by the sol-gel route, was pressed into pellets and one of them was sintered at 900 °C and the other at 1000 °C for 24 h. The aim of the study was to explore structural, electrical and magnetic properties of the compound. Temperature dependent X-ray powder diffraction studies on the sample sintered at 900 °C reveal an orthorhombic-Pbnm perovskite structure through the temperature range between 320 K and 86 K. Scanning electron microcopy and energy dispersive spectroscopy analyses showed grainy, homogeneous and stoichiometric structure. Magnetization and resistivity measurements reveal that the Curie temperatures, TC, and insulator-metal transition temperatures, TIM, coincide, but the samples sintered at 900 °C also exhibit thermal hysteresis both in magnetization and resistivity upon cooling and warming.

  15. Processing, electrical and microwave properties of sputtered Tl-Ca-Ba-Cu-O superconducting thin films

    NASA Technical Reports Server (NTRS)

    Subramanyam, G.; Kapoor, V. J.; Chorey, C. M.; Bhasin, K. B.

    1993-01-01

    A reproducible fabrication process has been established for TlCaBaCuO thin films on LaAlO3 substrates by RF magnetron sputtering and post-deposition processing methods. Electrical transport properties of the thin films were measured on patterned four-probe test devices. Microwave properties of the films were obtained from unloaded Q measurements of all-superconducting ring resonators. This paper describes the processing, electrical and microwave properties of Tl2Ca1Ba2Cu2O(x) 2122-plane phase thin films.

  16. Applying electrical utility least-cost approach to transportation planning

    SciTech Connect

    McCoy, G.A.; Growdon, K.; Lagerberg, B.

    1994-09-01

    Members of the energy and environmental communities believe that parallels exist between electrical utility least-cost planning and transportation planning. In particular, the Washington State Energy Strategy Committee believes that an integrated and comprehensive transportation planning process should be developed to fairly evaluate the costs of both demand-side and supply-side transportation options, establish competition between different travel modes, and select the mix of options designed to meet system goals at the lowest cost to society. Comparisons between travel modes are also required under the Intermodal Surface Transportation Efficiency Act (ISTEA). ISTEA calls for the development of procedures to compare demand management against infrastructure investment solutions and requires the consideration of efficiency, socioeconomic and environmental factors in the evaluation process. Several of the techniques and approaches used in energy least-cost planning and utility peak demand management can be incorporated into a least-cost transportation planning methodology. The concepts of avoided plants, expressing avoidable costs in levelized nominal dollars to compare projects with different on-line dates and service lives, the supply curve, and the resource stack can be directly adapted from the energy sector.

  17. Oxygen nonstoichiometry and transport properties of strontium substituted lanthanum ferrite

    SciTech Connect

    Sogaard, Martin Vang Hendriksen, Peter; Mogensen, Mogens

    2007-04-15

    This study presents an investigation of the properties of (La{sub 0.6}Sr{sub 0.4}){sub 0.99}FeO{sub 3-{delta}} (LSF40) covering thermomechanical properties, oxygen nonstoichiometry and electronic and ionic conductivity. Finally, oxygen permeation experiments have been carried out and the oxygen flux has been determined as a function of temperature and driving force. The electrical conductivity was measured using a 4 probe method. It is shown that the electrical conductivity is a function of the charge carrier concentration only. The electron hole mobility is found to decrease with increasing charge carrier concentration in agreement with recent literature. Values of the chemical diffusion coefficient, D{sub Chem}, and the surface exchange coefficient, k{sub Ex}, have been determined using electrical conductivity relaxation. At 800 deg. CD{sub Chem} is determined to be 6.2x10{sup -6}cm{sup 2}s{sup -1} with an activation energy of 137kJmol{sup -1}. The surface exchange coefficient is found to decrease with decreasing oxygen partial pressure. Oxygen permeation experiments were carried out. The flux through a membrane placed between air and wet hydrogen/nitrogen was J{sub O{sub 2}}{approx}1.8x10{sup -6}molcm{sup -2}s{sup -1} (corresponding to an equivalent electrical current density of 670mAcm{sup -2}). The oxygen permeation measurements are successfully interpreted based on the oxygen nonstoichiometry data and the determined transport parameters.

  18. Electronic transport properties of (fluorinated) metal phthalocyanine

    NASA Astrophysics Data System (ADS)

    Fadlallah, M. M.; Eckern, U.; Romero, A. H.; Schwingenschlögl, U.

    2016-01-01

    The magnetic and transport properties of the metal phthalocyanine (MPc) and F16MPc (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn and Ag) families of molecules in contact with S-Au wires are investigated by density functional theory within the local density approximation, including local electronic correlations on the central metal atom. The magnetic moments are found to be considerably modified under fluorination. In addition, they do not depend exclusively on the configuration of the outer electronic shell of the central metal atom (as in isolated MPc and F16MPc) but also on the interaction with the leads. Good agreement between the calculated conductance and experimental results is obtained. For M = Ag, a high spin filter efficiency and conductance is observed, giving rise to a potentially high sensitivity for chemical sensor applications.

  19. Transport properties of epitaxial lift off films

    NASA Technical Reports Server (NTRS)

    Mena, R. A.; Schacham, S. E.; Young, P. G.; Haugland, E. J.; Alterovitz, S. A.

    1993-01-01

    Transport properties of epitaxially lifted-off (ELO) films were characterized using conductivity, Hall, and Shubnikov-de Haas measurements. A 10-15 percent increase in the 2D electron gas concentration was observed in these films as compared with adjacent conventional samples. We believe this result to be caused by a backgating effect produced by a charge build up at the interface of the ELO film and the quartz substrate. This increase results in a substantial decrease in the quantum lifetime in the ELO samples, by 17-30 percent, but without a degradation in carrier mobility. Under persistent photoconductivity, only one subband was populated in the conventional structure, while in the ELO films the population of the second subband was clearly visible. However, the increase of the second subband concentration with increasing excitation is substantially smaller than anticipated due to screening of the backgating effect.

  20. Electrically induced displacement transport of immiscible oil in saline sediments.

    PubMed

    Pamukcu, Sibel; Shrestha, Reena A; Ribeiro, Alexandra B; Mateus, Eduardo P

    2016-08-01

    Electrically assisted mitigation of coastal sediment oil pollution was simulated in floor-scale laboratory experiments using light crude oil and saline water at approximately 1/10 oil/water (O/W) mass ratio in pore fluid. The mass transport of the immiscible liquid phases was induced under constant direct current density of 2A/m(2), without water flooding. The transient pore water pressures (PWP) and the voltage differences (V) at and in between consecutive ports lined along the test specimen cell were measured over 90days. The oil phase transport occurred towards the anode half of the test specimen where the O/W volume ratio increased by 50% over its initial value within that half-length of the specimen. In contrast, the O/W ratio decreased within the cathode side half of the specimen. During this time, the PWP decreased systematically at the anode side with oil bank accumulation. PWP increased at the cathode side of the specimen, signaling increased concentration of water there as it replaced oil in the pore space. Electrically induced transport of the non-polar, non-conductive oil was accomplished in the opposing direction of flow by displacement in absence of viscous coupling of oil-water phases. PMID:27064863

  1. Role of topology in electrical properties of bacterio-rhodopsin and rat olfactory receptor I7

    NASA Astrophysics Data System (ADS)

    Alfinito, E.; Reggiani, L.

    2010-03-01

    We report on electrical properties of the two sensing proteins: bacteriorhodopsin and rat olfactory receptor OR-I7. As relevant transport parameters we consider the small-signal impedance spectrum and the static current-voltage characteristics. Calculations are compared with available experimental results and the model predictability is tested for future perspectives.

  2. Calorimetric and transport properties of Zircalloy 2, Zircalloy 4, and Inconel 625

    NASA Astrophysics Data System (ADS)

    Maglić, K. D.; Perović, N. Lj.; Stanimirović, A. M.

    1994-07-01

    This paper presents the measurements and the results on thermal and electrical transport properties of three nuclear reactor cladding materials: Zircalloy 2, Zircalloy 4, and Inconel 625. Study of these materials constituted a part of the IAEA coordinated research program aimed at the generation and establishment of a reliable and complete database of the thermal properties of reactor materials. Measured properties include thermal diffusivity, specific heat, and electrical resistivity. Thermal diffusivity was measured by the laser pulse technique. Specific heat and electrical resistivity were measured using a millisecond-resolution direct electrical pulse heating technique. Thermal conductivity was computed from the experimentally determined thermal difusivity and specific heat functions and the room temperature density values. Measurements were performed in the 20 to 1500°C temperature range, depending on the material and property concerned.

  3. Calorimetric and transport properties of Zircalloy 2, Zircalloy 4, and Inconel 625

    SciTech Connect

    Maglic, K.D.; Perovic, N.Lj.; Stanimirovic, A.M.

    1994-07-01

    This paper presents the measurements and the results on thermal and electrical transport properties of three nuclear reactor cladding materials: Zircalloy 2, Zircalloy 4, and Inconel 625. Study of these materials constituted a part of the IAEA coordinated research program aimed at the generation and establishment of a reliable and complete database of the thermal properties of reactor materials. Measured properties include thermal diffusivity, specific heat, and electrical resistivity. Thermal diffusivity was measured by the laser pulse technique. Specific heat and electrical resistivity were measured using a millisecond-resolution direct electrical pulse heating technique. Thermal conductivity was computed from the experimentally determined thermal diffusivity and specific heat functions and the room temperature density values. Measurements were performed in the 20 to 1500{degrees}C temperature range, depending on the material and property concerned.

  4. Imprint electric field controlled electronic transport in TlGaSe2 crystals

    NASA Astrophysics Data System (ADS)

    Seyidov, MirHasan Yu; Suleymanov, Rauf A.; Balaban, Ertan; Şale, Yasin

    2013-09-01

    The effect of built-in electric field onto the dc electrical conductivity, photoconductivity, and electrical switching phenomenon were investigated in TlGaSe2 layered semiconductor within the temperature range of 77-300 K. We have used different types of electrodes for different TlGaSe2 samples in both parallel and perpendicular directions to the plane of layers. The effect of electric field was investigated by cooling the samples from the room temperature under the electric field and then removing it at ˜80 K. After the procedure, it was found that a built-in internal electric field which strongly affects transport properties appears in TlGaSe2 crystals. Substantial increasing of both dark currents and photo-conductivities were observed predominantly at low temperatures, where hopping was the main conductivity mechanism. The anomalous decrease of the activation energy in the low temperature region and the switching effect are also the main experimental findings of the present work. Such behavior can be understood by assuming that the built-in electric field greatly increases the contribution of the hopping conductivity at low temperatures. Obtained results are discussed on the basis of the models widely used for disordered semiconductors. It was shown that TlGaSe2 crystal demonstrates the peculiar behavior that is typical to such type of semiconductors.

  5. Role of inter-tube coupling and quantum interference on electrical transport in carbon nanotube junctions

    NASA Astrophysics Data System (ADS)

    Tripathy, Srijeet; Bhattacharyya, Tarun Kanti

    2016-09-01

    Due to excellent transport properties, Carbon nanotubes (CNTs) show a lot of promise in sensor and interconnect technology. However, recent studies indicate that the conductance in CNT/CNT junctions are strongly affected by the morphology and orientation between the tubes. For proper utilization of such junctions in the development of CNT based technology, it is essential to study the electronic properties of such junctions. This work presents a theoretical study of the electrical transport properties of metallic Carbon nanotube homo-junctions. The study focuses on discerning the role of inter-tube interactions, quantum interference and scattering on the transport properties on junctions between identical tubes. The electronic structure and transport calculations are conducted with an Extended Hückel Theory-Non Equilibrium Green's Function based model. The calculations indicate conductance to be varying with a changing crossing angle, with maximum conductance corresponding to lattice registry, i.e. parallel configuration between the two tubes. Further calculations for such parallel configurations indicate onset of short and long range oscillations in conductance with respect to changing overlap length. These oscillations are attributed to inter-tube coupling effects owing to changing π orbital overlap, carrier scattering and quantum interference of the incident, transmitted and reflected waves at the inter-tube junction.

  6. Electrical Transport in Nanoscale Complex Oxide Thin Films: Strontium titanate and RNiO3

    NASA Astrophysics Data System (ADS)

    Son, Junwoo

    Complex oxide thin films have attracted significant attention due to a wealth of physical phenomena, such as ferroelectricity and Mott transitions arising from strong interactions in d-bands. Moreover, the physical phenomena observed in these materials exhibit sensitivities, which are not found in conventional semiconductors and give rise to abrupt changes in their physical properties. The richness of electronic phases and unique functionalities of complex oxides are attractive for applications in next-generation electronic devices. To realize new electronic devices with complex oxides, it is essential to understand the mechanisms of the electrical transport and to control the transport properties of complex oxide thin films. In this dissertation, electrical transport phenomena and their electrical control are experimentally studied in two different complex oxide thin film systems, exhibiting resistive switching and Mott metal-insulator transitions. The first part will briefly discuss resistive switching in ultrathin SrTiO3 tunnel junctions in metal-insulator-metal (MIM) geometry. The current-voltage characteristics provide hints of the origin of the resistive switching phenomena in SrTiO3 tunnel barriers, which are also relevant for resistive switching in thicker films. The second part focuses on the control of metal-insulator transitions in RNiO3, where R = trivalent rare earth ion, using different strategies: band-width control and band-filling control. The electrical transport in low-dimensional, strongly correlated LaNiO3 is explored in terms of band-width control by strain and dimensionality. A new concept of band-filling control in nanoscale NdNiO3 thin films by modulation doping is discussed, and the experimental charge injection from high-quality La-doped SrTiO3 into NdNiO3 thin films is experimentally studied. The potential and limitations of a Modulation-doped Mott Field Effect Transistor (MM-FET) for future "Mott" electronic devices is discussed.

  7. Transport properties of supercooled confined water

    NASA Astrophysics Data System (ADS)

    Mallamace, F.; Branca, C.; Broccio, M.; Corsaro, C.; Gonzalez-Segredo, N.; Spooren, J.; Stanley, H. E.; Chen, S.-H.

    2008-07-01

    This article presents an overview of recent experiments performed on transport properties of water in the deeply supercooled region, a temperature region of fundamental importance in the science of water. We report data of nuclear magnetic resonance, quasi-elastic neutron scattering, Fourier-transform infrared spectroscopy, and Raman spectroscopy, studying water confined in nanometer-scale environments. When contained within small pores, water does not crystallise, and can be supercooled well below its homogeneous nucleation temperature Th. On this basis it is possible to carry out a careful analysis of the well known thermodynamical anomalies of water. Studying the temperature and pressure dependencies of water dynamics, we show that the liquid-liquid phase transition (LLPT) hypothesis represents a reliable model for describing liquid water. In this model, water in the liquid state is a mixture of two different local structures, characterised by different densities, namely the low density liquid (LDL) and the high-density liquid (HDL). The LLPT line should terminate at a special transition point: a low-T liquid-liquid critical point. We discuss the following experimental findings on liquid water: (i) a crossover from non-Arrhenius behaviour at high T to Arrhenius behaviour at low T in transport parameters; (ii) a breakdown of the Stokes-Einstein relation; (iii) the existence of a Widom line, which is the locus of points corresponding to maximum correlation length in the p-T phase diagram and which ends in the liquid-liquid critical point; (iv) the direct observation of the LDL phase; (v) a minimum in the density at approximately 70 K below the temperature of the density maximum. In our opinion these results represent the experimental proofs of the validity of the LLPT hypothesis.

  8. Visible light response, electrical transport, and amorphization in compressed organolead iodine perovskites

    NASA Astrophysics Data System (ADS)

    Ou, Tianji; Yan, Jiejuan; Xiao, Chuanhai; Shen, Wenshu; Liu, Cailong; Liu, Xizhe; Han, Yonghao; Ma, Yanzhang; Gao, Chunxiao

    2016-06-01

    Recent scientific advances on organic-inorganic hybrid perovskites are mainly focused on the improvement of power conversion efficiency. So far, how compression tunes their electronic and structural properties remains less understood. By combining in situ photocurrent, impedance spectroscopy, and X-ray diffraction (XRD) measurements, we have studied the electrical transport and structural properties of compressed CH3NH3PbI3 (MAPbI3) nanorods. The visible light response of MAPbI3 remains robust below 3 GPa while it is suppressed when it becomes amorphous. Pressure-induced electrical transport properties of MAPbI3 including resistance, relaxation frequency, and relative permittivity have been investigated under pressure up to 8.5 GPa by in situ impedance spectroscopy measurements. These results indicate that the discontinuous changes of these physical parameters occur around the structural phase transition pressure. The XRD studies of MAPbI3 under high pressure up to 20.9 GPa show that a phase transformation below 0.7 GPa, could be attributed to the tilting and distortion of PbI6 octahedra. And pressure-induced amorphization is reversible at a low density amorphous state but irreversible at a relatively higher density state. Furthermore, the MAPbI3 nanorods crush into nanopieces around 0.9 GPa which helps us to explain why the mixed phase of tetragonal and orthorhombic was observed at 0.5 GPa. The pressure modulated changes of electrical transport and visible light response properties open up a new approach for exploring CH3NH3PbI3-based photo-electronic applications.Recent scientific advances on organic-inorganic hybrid perovskites are mainly focused on the improvement of power conversion efficiency. So far, how compression tunes their electronic and structural properties remains less understood. By combining in situ photocurrent, impedance spectroscopy, and X-ray diffraction (XRD) measurements, we have studied the electrical transport and structural properties of

  9. Basic knowledge on radiative and transport properties to begin in thermal plasmas modelling

    SciTech Connect

    Cressault, Y.

    2015-05-15

    This paper has for objectives to present the radiative and the transport properties for people beginning in thermal plasmas. The first section will briefly recall the equations defined in numerical models applied to thermal plasmas; the second section will particularly deal with the estimation of radiative losses; the third part will quickly present the thermodynamics properties; and the last part will concern the transport coefficients (thermal conductivity, viscosity and electrical conductivity of the gas or mixtures of gases). We shall conclude the paper with a discussion about the validity of these results the lack of data for some specific applications, and some perspectives concerning these properties for non-equilibrium thermal plasmas.

  10. Evaluation of all-electric secondary power for transport aircraft

    NASA Astrophysics Data System (ADS)

    Murray, W. E.; Feiner, L. J.; Flores, R. R.

    1992-01-01

    This report covers a study by Douglas Aircraft Company (DAC) of electrical power systems for advanced transport aircraft based upon an all-electric design concept. The concept would eliminate distributed hydraulic and pneumatic secondary power systems, and feature an expanded secondary electrical power system redesigned to supply power to the loads customarily supplied by hydraulic or pneumatic power. The initial study was based on an advanced 20-kHz electrical power transmission and distribution system, using a system architecture supplied by NASA-Lewis Research Center for twin-engine aircraft with many advanced power conversion concepts. NASA-LeRC later requested DAC to refocus the study on 400-Hz secondary power distribution. Subsequent work was based on a three-engine MD-11 aircraft, selected by DAC as a baseline system design that would provide data for the comparative cost/benefit analysis. The study concluded that the 20-kHz concept produced many expected benefits, and that the all-electric trijet weight savings on hardware redesign would be 2,304 pounds plus a 2.1-percent fuel reduction and resized for a total weight reduction of 11,000 pounds. Cost reductions for a fleet of 800 aircraft in a 15-year production program were estimated at $76.71 million for RDT&E $2.74 million per aircrat for production; $9.84 million for nonrecurring expenses; $120,000 per aircraft for product support; and $300,000 per aircraft per year for operating and maintenance costs, giving a present value of $1.914 billion saved or a future value of $10.496 billion saved.