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Sample records for electrical transport properties

  1. Controlling the Electrical Transport Properties of Nanocontacts to Nanowires.

    PubMed

    Lord, Alex M; Maffeis, Thierry G; Kryvchenkova, Olga; Cobley, Richard J; Kalna, Karol; Kepaptsoglou, Despoina M; Ramasse, Quentin M; Walton, Alex S; Ward, Michael B; Köble, Jürgen; Wilks, Steve P

    2015-07-08

    The ability to control the properties of electrical contacts to nanostructures is essential to realize operational nanodevices. Here, we show that the electrical behavior of the nanocontacts between free-standing ZnO nanowires and the catalytic Au particle used for their growth can switch from Schottky to Ohmic depending on the size of the Au particles in relation to the cross-sectional width of the ZnO nanowires. We observe a distinct Schottky to Ohmic transition in transport behavior at an Au to nanowire diameter ratio of 0.6. The current-voltage electrical measurements performed with a multiprobe instrument are explained using 3-D self-consistent electrostatic and transport simulations revealing that tunneling at the contact edge is the dominant carrier transport mechanism for these nanoscale contacts. The results are applicable to other nanowire materials such as Si, GaAs, and InAs when the effects of surface charge and contact size are considered.

  2. Electrical transport and thermoelectric properties of boron carbide nanowires.

    PubMed

    Kirihara, Kazuhiro; Mukaida, Masakazu; Shimizu, Yoshiki

    2017-04-07

    The electrical transport and thermoelectric property of boron carbide nanowires synthesized by a carbothermal method are reported. It is demonstrated that the nanowires achieve a higher Seebeck coefficient and power factor than those of the bulk samples. The conduction mechanism of the nanowires at low temperatures below 300 K is different from that of the sintered-polycrystalline and single-crystal bulk samples. In a temperature range of 200-450 K, there is a crossover between electrical conduction by variable-range hopping and phonon-assisted hopping. The inhomogeneous carbon concentration and planar defects, such as twins and stacking faults, in the nanowires are thought to modify the bonding nature and electronic structure of the boron carbide crystal substantially, causing differences in the electrical conductivity and Seebeck coefficient. The effect of boundary scattering of phonon at nanostructured surface on the thermal conductivity reduction is discussed.

  3. 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.

  4. Electrical transport and thermoelectric properties of boron carbide nanowires

    NASA Astrophysics Data System (ADS)

    Kirihara, Kazuhiro; Mukaida, Masakazu; Shimizu, Yoshiki

    2017-04-01

    The electrical transport and thermoelectric property of boron carbide nanowires synthesized by a carbothermal method are reported. It is demonstrated that the nanowires achieve a higher Seebeck coefficient and power factor than those of the bulk samples. The conduction mechanism of the nanowires at low temperatures below 300 K is different from that of the sintered-polycrystalline and single-crystal bulk samples. In a temperature range of 200–450 K, there is a crossover between electrical conduction by variable-range hopping and phonon-assisted hopping. The inhomogeneous carbon concentration and planar defects, such as twins and stacking faults, in the nanowires are thought to modify the bonding nature and electronic structure of the boron carbide crystal substantially, causing differences in the electrical conductivity and Seebeck coefficient. The effect of boundary scattering of phonon at nanostructured surface on the thermal conductivity reduction is discussed.

  5. Electrical Transport Properties of Carbon Nanotube Metal-Semiconductor Heterojunction

    NASA Astrophysics Data System (ADS)

    Talukdar, Keka; Shantappa, Anil

    2016-10-01

    Carbon nanotubes (CNTs) have been proved to have promising applicability in various fields of science and technology. Their fascinating mechanical, electrical, thermal, optical properties have caught the attention of today’s world. We have discussed here the great possibility of using CNTs in electronic devices. CNTs can be both metallic and semiconducting depending on their chirality. When two CNTs of different chirality are joined together via topological defects, they may acquire rectifying diode property. We have joined two tubes of different chiralities through circumferential Stone-Wales defects and calculated their density of states by nearest neighbor tight binding approximation. Transmission function is also calculated to analyze whether the junctions can be used as electronic devices. Different heterojunctions are modeled and analyzed in this study. Internal stresses in the heterojunctions are also calculated by molecular dynamics simulation.

  6. 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.

  7. Electrical transport properties in Co nanocluster-assembled granular film

    NASA Astrophysics Data System (ADS)

    Zhang, Qin-Fu; Wang, Lai-Sen; Wang, Xiong-Zhi; Zheng, Hong-Fei; Liu, Xiang; Xie, Jia; Qiu, Yu-Long; Chen, Yuanzhi; Peng, Dong-Liang

    2017-03-01

    A Co nanocluster-assembled granular film with three-dimensional cross-connection paralleled conductive paths was fabricated by using the plasma-gas-condensation method in a vacuum environment. The temperature-dependent longitudinal resistivity and anomalous Hall effect of this new type granular film were systematically studied. The longitudinal resistivity of the Co nanocluster-assembled granular film first decreased and then increased with increasing measuring temperature, revealing a minimum value at certain temperature, T min . In a low temperature region ( T < T min ), the barrier between adjacent nanoclusters governed the electrical transport process, and the temperature coefficient of resistance (TCR) showed an insulator-type behavior. The thermal fluctuation-induced tunneling conduction progressively increased with increasing temperature, which led to a decrease in the longitudinal resistivity. In a high temperature region, the TCR showed a metallic-type behavior, which was primarily attributed to the temperature-dependent scattering. Different from the longitudinal resistivity behavior, the saturated anomalous Hall resistivity increased monotonically with increasing measuring temperature. The value of the anomalous Hall coefficient ( R S ) reached 2.3 × 10-9 (Ω cm)/G at 300 K, which was about three orders of magnitude larger than previously reported in blocky single-crystal Co [E. N. Kondorskii, Sov. Phys. JETP 38, 977 (1974)]. Interestingly, the scaling relation ( ρx y A ∝ ρx x γ ) between saturated anomalous Hall resistivity ( ρx y A ) and longitudinal resistivity ( ρ x x ) was divided into two regions by T min . However, after excluding the contribution of tunneling, the scaling relation followed the same rule. The corresponding physical mechanism was also proposed to explain these phenomena.

  8. Electrical Transport Properties of Polyaniline Containing HCl, CuCl2 and Multiwall Carbon Nanotube

    NASA Astrophysics Data System (ADS)

    Meikap, A. K.

    2011-07-01

    Electrical transport properties of hydrochloric acid (HCl) doped polyaniline (PANI) and composite of PANI with Copper Chloride (CuCl2) and multiwall Carbon Nanotube (MWNT) was measured within a temperature range 77⩽T⩽300 K in presence and in absence of a magnetic field up to 1Tesla. The electrical transport properties can be explained by the variable range hopping (VRH) theory. All the samples have shown negative d.c magnetoconductivity at the room temperature but PANI-HCl sample has shown a transition from positive to negative magnetoconductivity as the temperature is increased.

  9. 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.

  10. Modifying the Interface Edge to Control the Electrical Transport Properties of Nanocontacts to Nanowires.

    PubMed

    Lord, Alex M; Ramasse, Quentin M; Kepaptsoglou, Despoina M; Evans, Jonathan E; Davies, Philip R; Ward, Michael B; Wilks, Steve P

    2017-02-08

    Selecting the electrical properties of nanomaterials is essential if their potential as manufacturable devices is to be reached. Here, we show that the addition or removal of native semiconductor material at the edge of a nanocontact can be used to determine the electrical transport properties of metal-nanowire interfaces. While the transport properties of as-grown Au nanocatalyst contacts to semiconductor nanowires are well-studied, there are few techniques that have been explored to modify the electrical behavior. In this work, we use an iterative analytical process that directly correlates multiprobe transport measurements with subsequent aberration-corrected scanning transmission electron microscopy to study the effects of chemical processes that create structural changes at the contact interface edge. A strong metal-support interaction that encapsulates the Au nanocontacts over time, adding ZnO material to the edge region, gives rise to ohmic transport behavior due to the enhanced quantum-mechanical tunneling path. Removal of the extraneous material at the Au-nanowire interface eliminates the edge-tunneling path, producing a range of transport behavior that is dependent on the final interface quality. These results demonstrate chemically driven processes that can be factored into nanowire-device design to select the final properties.

  11. Crystal structure and electrical transport properties of single layered perovskite LaSrCoO4

    NASA Astrophysics Data System (ADS)

    Ahad, Abdul; Shukla, D. K.; Rahman, F.; Majid, S.; Tarachand; Okram, G. S.; Phase, D. M.

    2016-10-01

    We present here investigations on the influence of structure on electrical transport properties of polycrystalline LaSrCoO4 that is single layered perovskite with K2NiF4 type structure synthesized using solid state reaction route. Using Reitveld refinement of X-ray diffraction (XRD) data, it is found that the sample is in single phase with tetragonal structure (space group I4/mmm). Electrical resistivity performed in the temperature range 140-300K shows semiconducting character of the sample. Considerable contrasts in the Co-O bond length is associated with the intermediate spin (IS) state of Co ion that correlates the structural and transport properties. Detailed analysis indicates that the temperature dependent electrical resistivity follows the three-dimensional variable range hopping (VRH) model in low temperature region below 225K. The high temperature (225-300K) resistivity data has been found to follow the thermally activated behaviour.

  12. 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.

  13. 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.

  14. Electrical transport properties of Co-based skutterudites filled with Ag and Au

    NASA Astrophysics Data System (ADS)

    Stoica, Maria; Lo, Cynthia S.

    2012-09-01

    This work presents theoretical calculations of the electrical transport properties of the Ag, Au, and La fractionally filled bulk skutterudites: CoSb3, CoAs3, and CoP3. Density functional theory, along with projector augmented wave potentials, was used to calculate bulk band structures and partial density of states. The Seebeck coefficient (S), electrical conductivity (σ), and power factor (S2σ) were calculated as a function of temperature and filling fraction using the momentum matrix method along the entire first Brillouin zone. Calculated trends in the electrical transport properties agree with previously published experimental measurements for p-type unfilled and La-filled CoSb3. The calculated S and σ values for the Ag- and Au-filled compounds indicate that the most promising electronic properties are exhibited by p-type Au0.125(CoSb3)4, Au0.25(CoSb3)4, and Au(CoSb3)4. Au is therefore recommended as a promising filler for improved thermoelectric properties in cobalt antimonides. Ag is also a good filler for cobalt phosphides; the creation of a negative indirect band gap is observed in Ag(CoP3)4, which indicates semimetallic behavior, so this compound may possibly exhibit lower thermal conductivity than metallic CoP3. Finally, we recommend future directions for improving the thermoelectric figure of merit of these materials.

  15. Tailoring the thermal and electrical transport properties of graphene films by grain size engineering

    NASA Astrophysics Data System (ADS)

    Ma, Teng; Liu, Zhibo; Wen, Jinxiu; Gao, Yang; Ren, Xibiao; Chen, Huanjun; Jin, Chuanhong; Ma, Xiu-Liang; Xu, Ningsheng; Cheng, Hui-Ming; Ren, Wencai

    2017-02-01

    Understanding the influence of grain boundaries (GBs) on the electrical and thermal transport properties of graphene films is essentially important for electronic, optoelectronic and thermoelectric applications. Here we report a segregation-adsorption chemical vapour deposition method to grow well-stitched high-quality monolayer graphene films with a tunable uniform grain size from ~200 nm to ~1 μm, by using a Pt substrate with medium carbon solubility, which enables the determination of the scaling laws of thermal and electrical conductivities as a function of grain size. We found that the thermal conductivity of graphene films dramatically decreases with decreasing grain size by a small thermal boundary conductance of ~3.8 × 109 W m-2 K-1, while the electrical conductivity slowly decreases with an extraordinarily small GB transport gap of ~0.01 eV and resistivity of ~0.3 kΩ μm. Moreover, the changes in both the thermal and electrical conductivities with grain size change are greater than those of typical semiconducting thermoelectric materials.

  16. Tailoring the thermal and electrical transport properties of graphene films by grain size engineering

    PubMed Central

    Ma, Teng; Liu, Zhibo; Wen, Jinxiu; Gao, Yang; Ren, Xibiao; Chen, Huanjun; Jin, Chuanhong; Ma, Xiu-Liang; Xu, Ningsheng; Cheng, Hui-Ming; Ren, Wencai

    2017-01-01

    Understanding the influence of grain boundaries (GBs) on the electrical and thermal transport properties of graphene films is essentially important for electronic, optoelectronic and thermoelectric applications. Here we report a segregation–adsorption chemical vapour deposition method to grow well-stitched high-quality monolayer graphene films with a tunable uniform grain size from ∼200 nm to ∼1 μm, by using a Pt substrate with medium carbon solubility, which enables the determination of the scaling laws of thermal and electrical conductivities as a function of grain size. We found that the thermal conductivity of graphene films dramatically decreases with decreasing grain size by a small thermal boundary conductance of ∼3.8 × 109 W m−2 K−1, while the electrical conductivity slowly decreases with an extraordinarily small GB transport gap of ∼0.01 eV and resistivity of ∼0.3 kΩ μm. Moreover, the changes in both the thermal and electrical conductivities with grain size change are greater than those of typical semiconducting thermoelectric materials. PMID:28205514

  17. Tailoring the thermal and electrical transport properties of graphene films by grain size engineering.

    PubMed

    Ma, Teng; Liu, Zhibo; Wen, Jinxiu; Gao, Yang; Ren, Xibiao; Chen, Huanjun; Jin, Chuanhong; Ma, Xiu-Liang; Xu, Ningsheng; Cheng, Hui-Ming; Ren, Wencai

    2017-02-16

    Understanding the influence of grain boundaries (GBs) on the electrical and thermal transport properties of graphene films is essentially important for electronic, optoelectronic and thermoelectric applications. Here we report a segregation-adsorption chemical vapour deposition method to grow well-stitched high-quality monolayer graphene films with a tunable uniform grain size from ∼200 nm to ∼1 μm, by using a Pt substrate with medium carbon solubility, which enables the determination of the scaling laws of thermal and electrical conductivities as a function of grain size. We found that the thermal conductivity of graphene films dramatically decreases with decreasing grain size by a small thermal boundary conductance of ∼3.8 × 10(9) W m(-2) K(-1), while the electrical conductivity slowly decreases with an extraordinarily small GB transport gap of ∼0.01 eV and resistivity of ∼0.3 kΩ μm. Moreover, the changes in both the thermal and electrical conductivities with grain size change are greater than those of typical semiconducting thermoelectric materials.

  18. Dielectric, electrical transport and magnetic properties of Er3+substituted nanocrystalline cobalt ferrite

    NASA Astrophysics Data System (ADS)

    Kakade, S. G.; Kambale, R. C.; Kolekar, Y. D.; Ramana, C. V.

    2016-11-01

    Erbium substituted cobalt ferrite (CoFe2-xErxO4; x=0.0-0.2, referred to CFEO) materials were synthesized by sol-gel auto-combustion method. The effect of erbium (Er3+) substitution on the crystal structure, dielectric, electrical transport and magnetic properties of cobalt ferrite is evaluated. CoFe2-xErxO4 ceramics exhibit the spinel cubic structure without any impurity phase for x≤0.10 whereas formation of the ErFeO3 orthoferrite secondary phase was observed for x≥0.15. All the CFEO samples demonstrate the typical hysteresis (M-H) behavior with a decrease in magnetization as a function of Er content due to weak superexchange interaction. The frequency (f) dependent dielectric constant (ε‧) revealed the usual dielectric dispersion. The ε‧-f dispersion (f=20 Hz to 1 MHz) fits to the modified Debye's function with more than one ion contributing to the relaxation. The relaxation time and spread factor derived are ∼10-4 s and ∼0.61(±0.04), respectively. Electrical and dielectric studies indicate that ε‧ increases and the dc electrical resistivity decreases as a function of Er content (x≤0.15). Complex impedance analyses confirm only the grain interior contribution to the conduction process. Temperature dependent electrical transport and room temperature ac conductivity (σac) analyses indicate the semiconducting nature and small polaron hopping.

  19. 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.

  20. Effects of Ordered Stacking Faults on Electrical Transport Properties in Silicon Nanowires

    NASA Astrophysics Data System (ADS)

    Collette, Marc; Moutanabbir, Oussama; Champagne, Alexandre

    Lattice defects in silicon nanowires (SiNWs) allow the exploration of the fundamental physics governing transport mechanisms. We study charge transport in SiNW transistors with stacking faults in the 3C sequence, producing local hexagonal ordering. This structure leads to polytype SiNWs with distinct properties for novel applications in thermoelectronics. Since charge carrier and phonon behavior depend on crystal structure, these planar defects affect the transport properties of the nanowire. We grow our SiNWs using a VLS method, with stacking faults induced during growth. Structural characterization of each SiNW is done with Raman spectroscopy to quantify hexagonality. Individual nanowires are located and contacted using different metals to understand the Schottky barrier of the contacts at the SiNWs. We suspend 2 μm-long SiNW devices using a wet oxide etch to uncouple the SiNW from the substrate. We study the electrical properties by I-V measurements across the FET device while modulating the applied back gate voltage. Our initial data show that the presence of stacking faults causes an increase in resistivity by two orders of magnitude, thus greatly hindering charge transport through the SiNW.

  1. Electrical Transport Properties of Mn doped Bi2Se3 Thin Films

    NASA Astrophysics Data System (ADS)

    Babakiray, Sercan; Johnson, Trent; Borisov, Pavel; Lederman, David

    2015-03-01

    Magnetic impurity doping in topological insulators manifest itself with a gap opening in the Dirac cone as a result of breaking the time reversal symmetry. Moreover, the magnetic impurities affect the structural and quantum transport properties of topological insulators by increasing the disorder and by changing the bulk charge carrier type, charge carrier density and Hall mobility. Here, we investigated the effect of Mn doping on the structural and electrical transport properties of Bi2-xMnxSe3 thin films which are 12 quintuple layers thick and grown on Al2O3 (0001) single crystal substrates via molecular beam epitaxy (MBE). Hikami-Larkin-Nagaoka (HLN) formalism was used to study the weak antilocalization (WAL). Increasing Mn doping concentration was found to increase the bulk charge carrier density and to decrease the Hall mobility. A decrease was also observed in the phase coherence length related to WAL as a function of Mn content x. Values of another WAL parameter, the pre-factor alpha, showed that the top and bottom surfaces were coupled through the bulk conducting channels. The temperature dependence of phase coherence length indicated the electrical transport was dominated by 2D electron-electron scattering for the undoped, and by bulk weak localization effects for the Mn doped samples, respectively.

  2. The influence of stoichiometry on electrical properties of silicon carbide grown by physical vapor transport process

    NASA Astrophysics Data System (ADS)

    Li, Qiang

    The purposes of this thesis were to investigate the influence of the vapor phase stoichiometry in the ambient on electrical properties of silicon carbide grown by physical vapor transport (PVT) process in order to provide a better understanding of the nature of the compensation mechanisms in semi-insulating SiC crystals. Standard PVT and hydrogen-assisted PVT processes have been used to grow SiC single crystals. Chemical elemental analysis, contactless resistivity mapping (COREMA), temperature dependent Hall measurements (TDH), deep level transient spectroscopy (DLTS), and minority diffusion length measurements were performed to characterize the properties of SiC wafers. The nitrogen contamination, the net carrier concentrations, and the concentrations of the major deep traps in the undoped and nitrogen-doped SiC crystals were found to substantially decrease during the standard PVT growth when moving from seed to tail of the crystal. Addition of hydrogen to the growth ambient changed all the properties in the same direction. As a consequence of the doping and deep traps variations, the electrical properties including resistivity, Fermi energy, and minority carrier lifetime continuously changed during the growth. The results of the hydrogen-assisted PVT growth and the virtual reactor growth modeling indicated that the electrical properties change as a function of stoichiometry in the vapor phase, and the carbon transport efficiency can be enhanced by the reactions of hydrogen with the SiC charge material and the graphite parts of the crucible. Thermodynamic calculation of the vapor phase stoichiometry and the studies of the properties of H2-assisted PVT-grown crystals have shown that hydrogen can be used as a key factor controlling the vapor phase stoichiometry in the PVT process; in this manner the purity, electrical uniformities and the yield of the semi-insulating wafers can be improved to a great extent. The electron mobility values were found unusually low in

  3. 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.

  4. 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.

  5. Electrical and thermal transport property studies of high-temperature thermoelectric materials

    NASA Astrophysics Data System (ADS)

    Bates, J. L.

    1984-12-01

    High-temperature materials that exhibit small polaron conduction appear to exhibit the highest figures of merit. A thermoelectric model based on small polaron transport has been developed. The model predicts that broad-band semiconductors with small polarons hopping along inequivalent sites of distorted sublattices can result in increases in both the electrical conductivity and the Seeback coefficient with increasing temperature without significant increases in thermal conductivity. High figures of merit (ZT), greater than 1 at 1000K, that increase with increasing temperatures are predicted. The model is being applied to the divalent metal containing (Y,LA)Cr0(3) systems with an ABO(3) perovskite structure. Transport properties have been determined for various doping elements and for different compositions. These data are being used for the evaluation of this model.

  6. Electrical transport and magnetic properties of epitaxial LSMO films grown on STO substrates

    NASA Astrophysics Data System (ADS)

    Yuan, Wei; Zhao, Yuelei; Su, Tang; Song, Qi; Han, Wei; Shi, Jing

    2015-03-01

    La0.7Sr0.3MnO3 (LSMO) is a very attractive material for spintronics due to its half-metallic ferromagnetic properties. The LSMO films are epitaxially grown on STO (100) substrates using pulsed laser deposition. The effects of substrate temperature, laser power, oxygen pressure, and annealing on the LSMO growth are systematically investigated by the reflection high energy electron diffraction and atomic force microscopy. Under the optimized growth condition, we have achieved atomically flat LSMO thin films with a wide terrace width of more than 5 micro-meters. The electrical transport properties of LSMO thin films of various thicknesses ranging from 8 to 20 monolayers are studied by measuring the resistivity as a function of temperature. We find that the growth condition plays an important role in the critical film thickness for the metal-insulator transition and the Curie temperature. The Ministry of Science and Technology of China.

  7. Electrical transport properties of potassium germanide tungstates (K10Ge18WO4): A theoretical study

    NASA Astrophysics Data System (ADS)

    Azam, Sikander; Reshak, A. H.

    2014-06-01

    The total and partial density of states, electronic charge density and optical properties of the monoclinic structure K10Ge18WO4 compound have been investigated using a full relativistic version of the full-potential augmented plane-wave method based on the density functional theory, within local density approximation (LDA), generalized gradient approximation (GGA) and Engel-Vosko GGA (EVGGA). Density of states discloses the semiconductor nature of the calculated compound. There exists a strong hybridization between K-p and K-s, W-d and O-p, W-f and K-p. The analysis of the chemical bonding shows that the bonding possesses strong covalent nature. The dielectric optical properties were also calculated and discussed in detail. The electrical transport coefficients of the under observation compound have been investigated using the density functional theory calculation within EVGGA.

  8. 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.

  9. Effect of ambient on electrical transport properties of ultra-thin Au nanowires

    NASA Astrophysics Data System (ADS)

    Amin, Kazi Rafsanjani; Kundu, Subhajit; Biswas, Sangram; Roy, Ahin; Singh, Abhishek Kumar; Ravishankar, N.; Bid, Aveek

    2016-12-01

    In this letter we present systematic studies of the dynamics of surface adsorption of various chemicals on ultra-thin single crystalline gold nanowires (AuNW) through sensitive resistance fluctuation spectroscopy measurements coupled with ab initio simulations. We show that, contrary to expectations, the adsorption of common chemicals like methanol and acetone has a profound impact on the electrical transport properties of the AuNW. Our measurements and subsequent calculations establish conclusively that in AuNW, semiconductor-like sensitivity to the ambient arises because of changes induced in its local density of states by the surface adsorbed molecules. The extreme sensitivity of the resistance fluctuations of the AuNW to ambient suggests their possible use as solid-state sensors.

  10. Structural, dynamic, and transport properties of concentrated aqueous sodium chloride solutions under an external static electric field.

    PubMed

    Ren, Gan; Shi, Rui; Wang, Yanting

    2014-04-24

    In the absence of an external electric field, it has already been known that ion clusters are formed instantaneously in moderately concentrated ionic solutions. In this work, we use molecular dynamics (MD) simulations to investigate the changes of structural, dynamic, and transport properties in a sodium chloride solution under an external electric field from the ion cluster perspective. Our MD simulation results indicate that, with a strong external electric field E (≥0.1 V/nm) applied, ion clusters become smaller and less net charged, and the structures and dynamics as well as transport properties of the ion solution become anisotropic. The influence of the cluster structure and shell structure to transport properties was analyzed and the Einstein relation was found invalid in this system.

  11. Electrical transport properties of single undoped and n-type doped InN nanowires.

    PubMed

    Richter, T; Lüth, H; Schäpers, Th; Meijers, R; Jeganathan, K; Estévez Hernández, S; Calarco, R; Marso, M

    2009-10-07

    Electrical transport properties of undoped and n-type doped InN nanowires grown by molecular beam epitaxy were studied by current-voltage and back-gate field-effect transistor measurements. The current-voltage characteristics show ohmic behavior in the temperature range between 4 and 300 K. Down to about 120 K a linear decrease in resistance with temperature is observed. The investigation of a large number of nanowires revealed for undoped as well as doped wires an approximately linear relation between the normalized conductance and diameter for wires with a diameter below 100 nm. This shows that the main conduction takes place in the tubular surface accumulation layer of the wires. In contrast, for doped wires with a diameter larger than 100 nm a quadratic dependence of conduction on the diameter was found, which is attributed to bulk conductance as the main contribution. The successful doping of the wires is confirmed by an enhanced conduction and by the results of the back-gate field-effect transistor measurements.

  12. The microstructure and electrical transport properties of immiscible copper-niobium alloy thin films

    SciTech Connect

    Banerjee, Rajarshi; Bose, Sangita; Ayyub, Pushan; Genc, Arda

    2008-02-01

    Mutually immiscible in the solid state, copper and niobium exhibit a relatively strong clustering (phase separating) tendency in the liquid state and can therefore only be alloyed in a highly metastable form: for example, by vapor quenching. We have deposited metastable Cu-Nb alloy thin films with nominal compositions ranging from 5 to 90 at. % Nb by magnetron cosputtering. The microstructure of these films depends strongly on the composition and ranges from coarse-grained solid solutions for Cu-rich and Nb-rich compositions to phase-separated amorphous mixtures when the two elements are in comparable amounts. The crystalline Cu- or Nb-rich compositions exhibit positive temperature coefficients of resistivity (TCR) with the Cu-90 at. % Nb film exhibiting a superconducting transition with (T{sub C}){sub onset}{approx}4.5 K. The amorphous films show high room temperature resistivity, a negative TCR, and composition dependent superconducting transitions. We investigate the relation between the microstructure, phase stability, and the electrical transport properties.

  13. 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.

  14. Electrical transport properties of single-crystal CaB6,SrB6 , and BaB6

    NASA Astrophysics Data System (ADS)

    Stankiewicz, Jolanta; Rosa, Priscila F. S.; Schlottmann, Pedro; Fisk, Zachary

    2016-09-01

    The electrical resistivity and Hall effect of alkaline-earth-metal hexaboride single crystals are measured as a function of temperature, hydrostatic pressure, and magnetic field. The transport properties vary weakly with the external parameters and are modeled in terms of intrinsic variable-valence defects. These defects can stay either in (1) delocalized shallow levels or in (2) localized levels resonant with the conduction band, which can be neutral or negatively charged. Satisfactory agreement is obtained for electronic transport properties in a broad temperature and pressure range, although fitting the magnetoresistance is less straightforward and a combination of various mechanisms is needed to explain the field and temperature dependences.

  15. Cellular Automata Simulations of Thermal and Electrical Transport Properties of Thin-Film Polymer/CNTs Nanocomposites

    NASA Astrophysics Data System (ADS)

    Casey, Alex; Iannacchione, Germano; Georgiev, Georgi; Cebe, Peggy

    2014-03-01

    A computational algorithm has been developed to simulate the transport properties of oriented and un-oriented thin film nanocomposites of isotactic Polypropylene (iPP) and carbon nanotubes (CNT) with increasing CNT concentration. Our goal is to be able to design materials with optimal properties using simulations. We use cellular automata approach in Matlab simulation environment. The percolation threshold is reproduced in the simulations, matching experimental data. Upon percolation, the thermal transport in the films increases sharply, more so for the electrical than for the thermal conductivity, due to the larger difference in the electric conductivities of the CNTs and the polymer. To verify the simulation, the thin-film samples were sheared in the melt at 200 C at 1 Hz in a Linkan microscope shearing hot stage. The thermal and electrical conductivity measurements were performed on the same cell arrangement with the transport perpendicular to the thin-film plane using a DC method. The thermal and electrical conductivity are higher for the un-sheared as compared to the sheared samples with stronger temperature dependence for the latter as compared to the former. Our cellular automata simulations provide information about the microstructure-macroscopic property relation in the thin film nanocomposites and can be extended to simulations of other important materials.

  16. AC electrical transport properties and current-voltage hysteresis behavior of PVA-CNT nanocomposite film

    NASA Astrophysics Data System (ADS)

    Das, Amit Kumar; Sinha, Subhojyoti; Meikap, Ajit Kumar

    2015-06-01

    Polyvinyl alcohol (PVA) - Carbon nanotube (CNT) composite has been prepared and its electric modulus, ac conductivity, impedance spectroscopy and current-voltage characteristics have been studied, at and above room temperature, to understand the prevailing charge transport mechanism. Non-Debye type relaxation behavior was observed with activation energy of 1.27 eV whereas correlated barrier hopping was found to be the dominant charge transport mechanism with maximum barrier height of 48.7 meV above room temperature. The sample, under ±80 V applied voltage, exhibits hysteresis behavior in its current - voltage characteristics.

  17. Electrical and Thermal Transport Properties of Bi2Sr2Co2O9-δ Single Crystals and Thin Films

    NASA Astrophysics Data System (ADS)

    Diao, Zhenyu; Lee, H. N.; Chisholm, M.; Jin, Rongying

    2012-02-01

    Layered Bi2Sr2Co2O9-δ possesses rich physical properties, promising for thermoelectric applications. We have successfully synthesized Bi2Sr2Co2O9-δ in both single crystal and epitaxial thin film forms by applying various oxygen pressures. We found that their electrical and thermal transport properties are sensitive to the oxygen content, suggesting that the oxidation state of Co plays an important role in thermoelectric properties. Comparison of power factor between single crystals and thin films will be presented.

  18. 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.

  19. Electrical transport properties of (La,Pr,Ca)MnO3 nanowires investigated using terahertz time domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Nguyen, T. V. A.; Hattori, A. N.; Nagai, M.; Nakamura, T.; Ashida, M.; Tanaka, H.

    2016-03-01

    The electrical transport properties of a 100-nm-width (La,Pr,Ca)MnO3 nanowire sample were investigated using terahertz (THz) time domain spectroscopy. When the electric field of incident THz pulses was parallel to the nanowires, we obtained their intrinsic THz conductivity. The temperature-dependent dc conductivity and metallic fraction were simultaneously estimated by analyzing the THz conductivity using a metal-insulator composite model. The evaluated dc conductivity closely reproduced that measured by electrical probe measurement. The metallic fraction showed the evolution of electric domains from the metallic state at temperatures below 100 K to the insulating state at temperatures above 150 K through a coexistence region, which was in consistence with the phase-separated scenario.

  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. 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.

  2. 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

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    CoSi-C binary alloys have been fabricated by focused electron beam-induced deposition by the simultaneous use of dicobaltoctacarbonyl, Co2(CO)8, and neopentasilane, Si5H12, 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 CoSi2 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.

  5. 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.

  6. 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.

  7. Investigation of structural and electrical transport properties in Ti doped Sr2IrO4

    NASA Astrophysics Data System (ADS)

    Bhatti, Imtiaz Noor; Pramanik, A. K.

    2016-05-01

    Effects of Ti substitution at Ir-site on structural and electrical properties are studies in Sr2IrO4. Structural investigation has been done using x-ray powder diffraction and allied Rietveld analysis for all the samples. While there is no structural phase transition but the lattice parameters evolve with Ti doping. Resistivity measurements show an insulating behavior for all the samples. Data show resistivity increases drastically with Ti doping. The increase in resistivity is understood to arise due to dilution of Ir-O-Ir network as well as tuning of electronic correlation effect.

  8. 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.

  9. Intrinsic Defect Engineering of Cuprous Oxide to Enhance Electrical Transport Properties for Photovoltaic Applications

    SciTech Connect

    Lloyd, Michael A.; Siah, Sin-Cheng; Brandt, Riley E.; Serdy, James; Johnston, Steve W.; Lee, Yun Seog; Buonassisi, Tonio

    2014-06-08

    Intrinsic point-defect species in cuprous oxide films are manipulated based on their thermodynamic properties via the implementation of a controlled annealing process. A wide range of electrical properties is demonstrated, with a window suitable for high-quality solar cell devices. A variation of carrier concentration over two orders of magnitude is demonstrated. Minority carrier lifetime is investigated by means of microwave photoconductance decay measurements, demonstrating a strong correlation with carrier concentration. Spectrally resolved photoluminescence yields are analyzed to provide insight into lifetime limiting mechanisms as a function of Cu2O processing parameters. Hall measurements of carrier mobility and concentration are taken at room temperature to provide insight into the effect of these processing conditions on net ionized defect concentration.

  10. 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.

  11. 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.

  12. 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.

  13. Structural, optical, and electrical-transport properties of Al-P-O inorganic layer coated on flexible stainless steel substrate

    NASA Astrophysics Data System (ADS)

    Kim, Moojin; Min, Jinhyuk; Kwak, Yongsu; Kim, Doori; Kim, Kyoung-Bo; Song, Jonghyun

    2017-03-01

    We coated inorganic layer containing oxygen, aluminium, phosphorus, and negligible sodium (APO) on stainless steel (STS) by using slot-die coating method and studied its application prospects as a substrate for flexible devices. The APO layer was compositionally uniform in overall area with an amorphous crystal structure. Surface morphology characterization of STS exhibited an improved flatness after the APO layer coating process. The optical property characterization of the APO film carried out by measuring optical reflectance spectrum and refractive index. We also investigated the electrical-transport mechanism in the APO layer. These experimental observations imply the possibility of potential application of APO-STS as a substrate for flexible devices.

  14. Centimeter-long Ta3N5 nanobelts: synthesis, electrical transport, and photoconductive properties

    NASA Astrophysics Data System (ADS)

    Wu, X. C.; Tao, Y. R.; Li, L.; Bando, Y.; Golberg, D.

    2013-05-01

    Centimeter-long Ta3N5 nanobelts were synthesized by a reaction of centimeter-long TaS3 nanobelt templates with flowing NH3 at 800 °C for 2 h. The nanobelts have cross-sections of about 50 × 100 nm2, and lengths up to 0.5 cm. A field effect transistor (FET) made of a single Ta3N5 nanobelt was fabricated on silica/silicon substrate. The electric transport of the individual nanobelt revealed that the nanobelt is a semiconductor with a room-temperature resistivity of 11.88 Ω m, and can be fitted well with an empirical formula ρ = 10831 exp(-T/43.8) - 22.6, where ρ is resistivity (Ω m) and T is absolute temperature (K). The FET showed decent photoconductive performance under light irradiation in the range 250-630 nm. The photocurrent increased by nearly 10 times the dark current under 450 nm light irradiation at an applied voltage of 5.0 V.

  15. Ce Core-Level Spectroscopy, and Magnetic and Electrical Transport Properties of Lightly Ce-Doped YCoO3

    NASA Astrophysics Data System (ADS)

    Kobayashi, Yoshihiko; Koike, Tsuyoshi; Okawa, Mario; Takayanagi, Ryohei; Takei, Shohei; Minohara, Makoto; Kobayashi, Masaki; Horiba, Koji; Kumigashira, Hiroshi; Yasui, Akira; Ikenaga, Eiji; Saitoh, Tomohiko; Asai, Kichizo

    2016-11-01

    We have investigated the Ce and Co core level spectroscopy, and the magnetic and electrical transport properties of lightly Ce-doped YCoO3. We have successfully synthesized single-phase Y1-xCexCoO3 for 0.0 ≤ x ≤ 0.1 by the sol-gel method. Hard X-ray photoelectron and X-ray absorption spectroscopy experiments reveal that the introduced Ce ions are tetravalent, which is considered to be the first case of electron doping into bulk trivalent Co oxides with perovskite RECoO3 (RE: rare-earth element or Y) caused by RE site substitution. The magnitude of the effective magnetic moment peff obtained from the temperature dependence of magnetic susceptibility χ(T) at higher temperatures is close to that for high-spin Co2+ introduced by the Ce doping, implying that the electrons doped into the Co site induce Co2+ with a high-spin state. For x = 0.1, ferromagnetic ordering is observed below about 7 K. Electrical transport properties such as resistivity and thermoelectric power show that negative electron-like carriers are introduced by Ce substitution.

  16. Temperature-dependent electrical transport properties of (Au/Ni)/n-GaN Schottky barrier diodes

    NASA Astrophysics Data System (ADS)

    Dogan, Hulya; Elagoz, Sezai

    2014-09-01

    The temperature-dependent electrical properties of (Au/Ni)/n-GaN Schottky barrier diodes (SBDs)have been investigated in the wide temperature range of 40-400 K. The analysis of the main electrical characteristics such as zero-bias barrier height (ΦB0), ideality factor (n) and series resistance (Rs) were found strongly temperature dependent. Such behavior is attributed to barrier inhomogeneities by assuming a Gaussian distribution (GD) of barrier heights (BHs) at the interface. It is evident that the diode parameters such as zero-bias barrier height increases and the ideality factor decreases with increasing temperature. The values of series resistance that are obtained from Cheung's method are decreasing with increasing temperature. The temperature dependence of Schottky barrier height (SBD) and ideality factor (n) are explained by invoking three sets of Gaussian distribution of (SBH) in the temperature ranges of 280-400 K, 120-260 K and 40-100 K, respectively. (Au/Ni)/n-GaN Schottky barrier diode have been shown a Gaussian distribution giving mean BHs (ΦbarB0) of 1.167, 0.652 and 0.356 eV and standard deviation σs of 0.178, 0.087 and 0.133 V for the three temperature regions. A modified ln(I0/T2)-q2σ2/2k2T2 vs. 1/kT plot have given ΦbarB0 and A* as 1.173 eV and 34.750 A/cm2 K2, 0.671 eV and 26.293 A/cm2 K2, 0.354 eV and 10.199 A/cm2 K2, respectively.

  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. 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.

  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. Electrical transport properties of small diameter single-walled carbon nanotubes aligned on ST-cut quartz substrates

    PubMed Central

    2014-01-01

    A method is introduced to isolate and measure the electrical transport properties of individual single-walled carbon nanotubes (SWNTs) aligned on an ST-cut quartz, from room temperature down to 2 K. The diameter and chirality of the measured SWNTs are accurately defined from Raman spectroscopy and atomic force microscopy (AFM). A significant up-shift in the G-band of the resonance Raman spectra of the SWNTs is observed, which increases with increasing SWNTs diameter, and indicates a strong interaction with the quartz substrate. A semiconducting SWNT, with diameter 0.84 nm, shows Tomonaga-Luttinger liquid and Coulomb blockade behaviors at low temperatures. Another semiconducting SWNT, with a thinner diameter of 0.68 nm, exhibits a transition from the semiconducting state to an insulating state at low temperatures. These results elucidate some of the electrical properties of SWNTs in this unique configuration and help pave the way towards prospective device applications. PMID:25170326

  2. Effect of Y-doping on the electrical transport properties of nanocrystalline BiFeO3

    NASA Astrophysics Data System (ADS)

    Mukherjee, A.; Basu, S.; Chakraborty, G.; Pal, M.

    2012-07-01

    Effect of yttrium doping on the electrical transport properties of sol-gel prepare nanocrystalline BiFeO3 was investigated. A comprehensive state-of-the art sophisticated instruments like x-ray diffraction, differential thermal analyzer, field emission scanning electron microscope, and HRTEM were utilized to characterize the BiFeO3 nanoparticles. It was observed that the values of dc activation energy calculated from Arrhenius relation increase with increase of yttrium content. The variation of ac conductivity with frequency and temperature exhibits a correlated barrier hopping conduction mechanism. The dielectric permittivity of the sample reveals an increasing tendency with the concentration of yttrium and depends on both the grain and the interfacial grain boundary resistance. The activation energies for the dielectric relaxation estimated from the modulus spectra were found to be reasonably good agreement with those obtained from dc conductivity study.

  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. The Distribution Function and Transport Properties of Charged Particles in Strong, Crossed Electric and Magnetic fields

    DTIC Science & Technology

    2007-10-11

    kernels of the obtained system of the integro - differential equations . Our work on the project was proceeded during 11 Quarters, the Quarter 12 being...was created to solve a system of the integro - differential equations involv- ing the ion interaction with the electric field as well as the magnetic one...corresponds to the differential (left) side of the Boltzmann equation . When there is not any external force, this operator was studied in [16]. In the presence

  5. 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

  6. 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.

  7. 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.

  8. Extreme Chemical Disorder and the Electrical Transport Properties of Concentrated Solid Solution Alloys: From Binaries to High Entropy Alloys Replace this text with your abstract title

    NASA Astrophysics Data System (ADS)

    Stocks, G. Malcolm; Samolyuk, German; Khan, Suffian; Daene, Markus; Wimmer, Sebastian; Sales, Brian; Bei, Hongbin; Jin, Ke

    We present the results of experimental and theoretical studies of electrical transport properties of a family of 2, 3, 4 and 5-component concentrated solid solution alloys (CSA) comprising subsets of the 3d- and 4d-transition metal elements Cr, Mn, Fe, Co, Ni and Pd. Many of this family of CSA show unusual mechanical, magnetic and transport properties as well as indications of increased radiation resistance that are clearly related to the underlying chemical disorder. Here we show the results of calculations of the electrical transport properties that are based on the ab initio Korringa-Kohn-Rostoker coherent-potential-approximation (KKR-CPA) method for treating the effect of substitutional disorder, and necessary configurational averaging, on the underlying electronic structure. We compare calculated residual (T =0K) resistivities to corresponding experimental measurements and relate the variations in residual resistivity, which span almost two orders of magnitude, to the underlying electron structure.

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

    NASA Astrophysics Data System (ADS)

    Wang, Juan; Zhao, Kongshuang; Wu, Lixin

    2014-08-01

    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+ and Keggin polyoxometalate anion, [XW12O40]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 P12W403- and Si12W404- 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+ ion-pairs formed by POM and protonated DMF. The interaction between anion and cation in POM-DMFH+ ion-pairs are explained theoretically based on the Bruggeman's mixture theories and dipole rotation model. From this, the distance between POM and DMFH+ are estimated as about 1.1 nm.

  10. 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.

  11. 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.

  12. Fabrication and electrical transport properties of embedded graphite microwires in a diamond matrix

    NASA Astrophysics Data System (ADS)

    Barzola-Quiquia, J.; Lühmann, T.; Wunderlich, R.; Stiller, M.; Zoraghi, M.; Meijer, J.; Esquinazi, P.; Böttner, J.; Estrela-Lopis, I.

    2017-04-01

    Micrometer width and nanometer thick wires with different shapes were produced ≈ 3~μ m below the surface of a diamond crystal using a microbeam of He+ ions with 1.8 MeV energy. Initial samples are amorphous and after annealing at T≈ 1475 K, the wires crystallized into graphite-like structures, according to confocal Raman spectroscopy measurements. The electrical resistivity at room temperature is only one order of magnitude larger than the in-plane resistivity of highly oriented pyrolytic bulk graphite and shows a small resistivity ratio (ρ ≤ft(2~\\text{K}\\right)/ρ ≤ft(315~\\text{K}\\right)≈ 1.275 ). A small negative magnetoresistance below T  =  200 K was measured and can be well understood taking spin-dependent scattering processes into account. The used method provides the means to design and produce millimeter to micrometer sized conducting circuits with arbitrary shape embedded in a diamond matrix.

  13. 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.

  14. Application of light scattering in studies of transport, thermodynamics, light absorption, and electric properties of single droplets

    NASA Astrophysics Data System (ADS)

    Tu, Haohua

    2001-12-01

    A variety of subjects related to an isolated microdroplet, including precise optical measurement, fundamental light scattering theory, in situ droplet spectroscopy, transport mechanism, solution thermodynamics, and electrical stability, have been studied. A technique based on optical resonance alignment is developed to automate the measurement of the optical parameters for a single component droplet. The technique is able to determine the size and refractive index of the droplet with an accuracy of 1 part in 10000, and is also applicable to multicomponent droplets undergoing various physical changes with tolerable degradation of accuracy or automation. By examining the finest details of optical resonances, Mie's light scattering theory is proved to be valid except for a constant background broadening deviation. The effect of eccentricity on light scattering of a layered droplet is first observed. By preparing a concentrically layered droplet, rigorous experimental verification is presented for Aden-Kerker light scattering theory of a concentric sphere. Novel computational technique is developed to identify optical resonances and locate their positions for a concentric sphere of specific properties. A unique technique based on accurate measurement of the imaginary refractive index of a droplet is developed for in situ determination of the concentrations of absorptive chemical species inside the droplet. The effects of Stefan flow, non-isothermal effect, unsteady state behavior, unstationary mechanism, and internal transport on the function of droplet size versus time of a relatively nonvolatile droplet have been proved unimportant. Remarkable accuracy of the asymptotic model based on Maxwell's diffusion controlled theory is justified both theoretically and experimentally. Particular evaporation characteristics are observed for several layered droplets. Explicit as well as implicit methods based on resonance alignment have been developed to determine the activity

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

    SciTech Connect

    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; Belianinov, Alex; Cross, Nicholas

    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 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. 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.

  16. 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.

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

    DOE PAGES

    Stanford, Michael; Noh, Joo Hyon; Koehler, Michael R.; ...

    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. Transport Properties in Nuclear Pasta

    NASA Astrophysics Data System (ADS)

    Caplan, Matthew; Horowitz, Charles; Berry, Donald; da Silva Schneider, Andre

    2016-09-01

    At the base of the inner crust of neutron stars, where matter is near the nuclear saturation density, nuclear matter arranges itself into exotic shapes such as cylinders and slabs, called `nuclear pasta.' Lepton scattering from these structures may govern the transport properties of the inner crust; electron scattering from protons in the pasta determines the thermal and electrical conductivity, as well as the shear viscosity of the inner crust. These properties may vary in pasta structures which form at various densities, temperatures, and proton fractions. In this talk, we report on our calculations of lepton transport in nuclear pasta and the implication for neutron star observables.

  19. Dependence of electrical transport properties of CaO(CaMnO3)m (m = 1, 2, 3, ∞) thermoelectric oxides on lattice periodicity

    NASA Astrophysics Data System (ADS)

    Baranovskiy, Andrei; Amouyal, Yaron

    2017-02-01

    The electrical transport properties of CaO(CaMnO3)m (m = 1, 2, 3, ∞) compounds are studied applying the density functional theory (DFT) in terms of band structure at the vicinity of the Fermi level (EF). It is shown that the total density of states (DOS) values at EF increase with increase in the m-values, which implies an increase in the electrical conductivity, σ, with increasing m-values, in full accordance with experimental results. Additionally, the calculated values of the relative slopes of the DOS at EF correlate with the experimentally measured Seebeck coefficients. The electrical conductivity and Seebeck coefficients were calculated in the framework of the Boltzmann transport theory applying the constant relaxation time approximation. By the analysis of experimental and calculated σ(Τ) dependences, the electronic relaxation time and mean free path values were estimated. It is shown that the electrical transport is dominated by electron scattering on the boundaries between perovskite (CaMnO3) and Ca oxide (CaO) layers inside the crystal lattice.

  20. 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.

  1. 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.

  2. Electrical and thermal transport properties of layered Bi{sub 2}YO{sub 4}Cu{sub 2}Se{sub 2}

    SciTech Connect

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

    2016-07-15

    Bi{sub 2}YO{sub 4}Cu{sub 2}Se{sub 2} 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 Bi{sub 2}YO{sub 4}Cu{sub 2}Se{sub 2} system in the temperature range from 300 K to 873 K. We found that the total thermal conductivity decreases from ~1.8 W m{sup −1} K{sup −1} to ~0.9 W m{sup −1} K{sup −1}, and the electrical conductivity decreases from ~850 S/cm to ~163 S/cm in the measured temperature range. To investigate how potential of Bi{sub 2}YO{sub 4}Cu{sub 2}Se{sub 2} 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{sup −1} K{sup −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 Bi{sub 2}YO{sub 4}Cu{sub 2}Se{sub 2} 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. - Highlights: • The total thermal conductivity decreases from 1.8 to 0.9 Wm{sup –1}K{sup –1} at 300–873K. • The electrical conductivity decreased from 850 to 163 S/cm at 300–873K. • The Seebeck coefficients were enhanced through heavily Iodine doping. • The ZT ~0.06 at 873K suggests that Bi{sub 2}YO{sub 4}Cu{sub 2}Se{sub 2} systems are potential thermoelectrical materials.

  3. 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

  4. Effect of particle size on magnetic and electric transport properties of La(0.67)Sr(0.33)MnO3 coatings.

    PubMed

    Zhou, Yu; Zhu, Xinde; Li, Shengli

    2015-12-14

    A systematic study of polycrystalline La0.67Sr0.33MnO3 (LSMO) manganite coatings has been undertaken to analyse the effect of various particle sizes on the magnetic and electric transport properties. In order to acquire a series of samples with different particle sizes, the samples were prepared by a sol-gel method and were subjected to annealing at four different temperatures. With decreasing particle sizes, the magnetization decreases while the coercivity increases, which is attributed to the magnetically disordered surface layer. More attractively, the electrical transport properties can be systematically manipulated by particle sizes and so can the low field magnetoresistance (LFMR) values. Emphasis is placed on how the particle size affects the temperature dependence of resistivity, and three conduction models are explored to describe the transport behaviours in three temperature regions. A minimum resistivity is observed in the low temperature region in the presence and absence of a magnetic field, which can be mainly explained as due to the intergranular spin polarized tunneling (ISPT) through the grain boundaries (GBs) in polycrystalline materials.

  5. 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.

  6. Magnetic, specific heat and electrical transport properties of oxygen-deficient nanosized rutile TiO2‑δ

    NASA Astrophysics Data System (ADS)

    Tran, Vinh Hung; Thi Quynh Hoa, Nguyen

    2017-03-01

    An oxygen-deficient nanosized {{TiO}}2-δ , δ ∼ 0.7 sample was synthesized by a solvothermal method, and was characterized to have both ∼3 nm amorphous solid and ∼36–46 nm diameter rutile nanowires. Physical properties of the sample were investigated by measuring magnetic, specific heat, electrical resistance and magnetoresitance properties. DC magnetization M(H) data confirm ferromagnetic behavior previously reported for undoped TiO2. Furthermore, M(T) dependence follows the power-law relation M{(T)\\propto (1-T/{T}C)}β in the near-critical regime, yielding Curie temperature {T}C ∼ 415 K and critical exponent β = 0.2. Moreover, our results of AC magnetic susceptibility measurements suggest an additional phase transition at {T}* ∼ 310 K, presumably due to spin orientation. The metallic-like electrical resistance exhibits a distinct drop below {T}* with a strong thermal hysteresis in the temperature range 225–275 K. Specific heat in the temperature range 20–300 K is well described by the sum of contributions from acoustic phonons with Debye temperature 605 K and optical phonons with Einstein temperature 113 K. Below 10 K the specific heat divulges a large excess, which can be interpreted as an additional contribution originating from soft potentials.

  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. Electrical transport properties of (110)-oriented PrBa2(Cu0.8Ga0.2)3O7 thin films

    NASA Astrophysics Data System (ADS)

    Kandel, Hom; Chen, Tar-Pin; Bourdo, Shawn; Iliev, Milko N.; Watanabe, Fumiya; Seo, Hye-Won; Viswanathan, Tito

    2012-06-01

    The electrical transport properties of (110)-oriented PrBa2(Cu0.8Ga0.2)3O7 (PBCGO) thin films have been investigated. The electrical resistivity, ρ(T), of (110)-oriented PBCGO thin films is 8.91 × 105 Ω-cm at 77 K, about five orders of magnitude higher than that of the (110)-oriented PrBa2Cu3O7 thin films and follows Mott's T-1/4 law up to room temperature. Our experimental results suggest filling and localization of holes in Cu-O chains of (110)-oriented PBCGO thin films. We observed very less proximity effect on YBa2Cu3O7 (YBCO)/PBCGO multilayers indicating that the (110)-oriented PBCGO thin films may serve as effective insulators in YBCO SIS tunneling Josephson junction.

  9. 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

    2016-11-01

    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.

  10. 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.

  11. Electrical transport in a microdevice chain

    NASA Astrophysics Data System (ADS)

    Sinkkonen, J.; Eränen, S.

    A simple transport theory of a one-dimensional chain of small devices is presented. The chain is comprised of potential barriers connected by short conductors. Electrical transport through the barriers is described in terms of the quantum reflection and transmission coefficients. The conductors, which are longer than the de Broglie wavelength but eventually shorter than the mean tree path, are discussed within the Boltzmann transport theory. By fitting the solutions of the Boltzmann equation with the boundary conditions imposed by reflection and transmission at barriers a complete solution for the chain can be obtained. As an application, the two-barrier structure is studied in detail. As an function of the conductor length the current shows interference type resonances associated with scattering damped multiple reflections. The properties of the ballistic transistor are determined from the model.

  12. Influence of carbon nanoparticles/epoxy matrix interaction on mechanical, electrical and transport properties of structural advanced materials

    NASA Astrophysics Data System (ADS)

    Guadagno, Liberata; Naddeo, Carlo; Raimondo, Marialuigia; Barra, Giuseppina; Vertuccio, Luigi; Russo, Salvatore; Lafdi, Khalid; Tucci, Vincenzo; Spinelli, Giovanni; Lamberti, Patrizia

    2017-03-01

    The focus of this study is to design new nano-modified epoxy formulations using carbon nanofillers, such as carbon nanotubes, carbon nanofibers and graphene-based nanoparticles (CpEG), that reduce the moisture content and provide additional functional performance. The chemical structure of epoxy mixture, using a non-stoichiometric amount of hardener, exhibits unique properties in regard to the water sorption for which the equilibrium concentration of water (C eq) is reduced up to a maximum of 30%. This result, which is very relevant for several industrial applications (aeronautical, shipbuilding industries, wind turbine blades, etc), is due to a strong reduction of the polar groups and/or sites responsible to bond water molecules. All nanofillers are responsible of a second phase at lower glass transition temperature (Tg). Compared with other carbon nanofillers, functionalized graphene-based nanoparticles exhibit the best performance in the multifunctionality. The lowest moisture content, the high performance in the mechanical properties, the low electrical percolation threshold (EPT) have been all ascribed to particular arrangements of the functionalized graphene sheets embedded in the polymeric matrix. Exfoliation degree and edge carboxylated groups are responsible of self-assembled architectures which entrap part of the resin fraction hindering the interaction of water molecules with the polar sites of the resin, also favouring the EPT paths and the attractive/covalent interactions with the matrix.

  13. Influence of carbon nanoparticles/epoxy matrix interaction on mechanical, electrical and transport properties of structural advanced materials.

    PubMed

    Guadagno, Liberata; Naddeo, Carlo; Raimondo, Marialuigia; Barra, Giuseppina; Vertuccio, Luigi; Russo, Salvatore; Lafdi, Khalid; Tucci, Vincenzo; Spinelli, Giovanni; Lamberti, Patrizia

    2017-03-03

    The focus of this study is to design new nano-modified epoxy formulations using carbon nanofillers, such as carbon nanotubes, carbon nanofibers and graphene-based nanoparticles (CpEG), that reduce the moisture content and provide additional functional performance. The chemical structure of epoxy mixture, using a non-stoichiometric amount of hardener, exhibits unique properties in regard to the water sorption for which the equilibrium concentration of water (C eq) is reduced up to a maximum of 30%. This result, which is very relevant for several industrial applications (aeronautical, shipbuilding industries, wind turbine blades, etc), is due to a strong reduction of the polar groups and/or sites responsible to bond water molecules. All nanofillers are responsible of a second phase at lower glass transition temperature (Tg). Compared with other carbon nanofillers, functionalized graphene-based nanoparticles exhibit the best performance in the multifunctionality. The lowest moisture content, the high performance in the mechanical properties, the low electrical percolation threshold (EPT) have been all ascribed to particular arrangements of the functionalized graphene sheets embedded in the polymeric matrix. Exfoliation degree and edge carboxylated groups are responsible of self-assembled architectures which entrap part of the resin fraction hindering the interaction of water molecules with the polar sites of the resin, also favouring the EPT paths and the attractive/covalent interactions with the matrix.

  14. 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.

  15. Structure and electrical and transport properties of cation-deficient samples of perovskite ferrocuprates RBaCuFeO5 + δ ( R = Y, La)

    NASA Astrophysics Data System (ADS)

    Klyndyuk, A. I.; Chizhova, E. A.

    2008-04-01

    The structure, thermal expansion, and electrical properties of cation-deficient ferrocuprates RBaCuFeO5 + δ ( R = Y, La), which are p-type semiconductors, are investigated. The linear thermal expansion coefficient of the yttrium-barium ferrocuprate decreases upon formation of vacancies in the A sublattice (Y, Ba), while the unit cell parameters remain practically unchanged upon the formation of vacancies in different sublattices (Y, Ba, Cu/Fe) of the crystal structure. From analyzing the results of the thermopower measurements, it is assumed that the YBaCuFeO5 + δ ferrocuprate is actually a “nanocomposite” consisting of nanoregions of the Y2Cu2O5 and BaFeO3 - δ phases. The lanthanum deficiency brings about an increase in the LaBaCuFeO5 + δ unit cell while leaving very nearly unaffected its linear thermal expansion coefficient and electrical properties. The formation of cation vacancies in extended [Ba(Cu,Fe)2O5] blocks of the LaBaCuFeO5 + δ phase gives rise to tetragonal distortion of its cubic structure, a decrease in the linear thermal expansion coefficient, and an increase in the electrical resistivity of the samples, the latter resulting primarily from an increase in the carrier transport energy in (Cu,Fe)O2 layers of LaBaCuFeO5 + δ.

  16. The low temperature specific heat and electrical transport, magnetic properties of Pr0.65Ca0.35MnO3

    NASA Astrophysics Data System (ADS)

    Han, Zhiyong

    2017-02-01

    The magnetic properties, electrical transport properties, and low temperature specific heat of polycrystalline perovskite manganese oxide Pr0.65Ca0.35MnO3 have been investigated experimentally. It is found that there exists cluster glass state in the sample at low temperature besides the antiferromagnetic insulating state. With the increase of magnetic field, antiferromagnetic insulating state converts to ferromagnetic metal state and the Debye temperature decreases gradually. In addition, the low temperature electron specific heat in zero magnetic field is obviously larger than that of ordinary rare-earth manganites oxide and this phenomenon is related to the itinerant electrons in ferromagnetic cluster state and the disorder in Pr0.65Ca0.35MnO3.

  17. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES Electronic Transport Calculations Using Maximally-Localized Wannier Functions

    NASA Astrophysics Data System (ADS)

    Wang, Neng-Ping

    2011-01-01

    I present a method to calculate the ballistic transport properties of atomic-scale structures under bias. The electronic structure of the system is calculated using the Kohn-Sham scheme of density functional theory (DFT). The DFT eigenvectors are then transformed into a set of maximally localized Wannier functions (MLWFs) [N. Marzari and D. Vanderbilt, Phys. Rev. B 56 (1997) 12847]. The MLWFs are used as a minimal basis set to obtain the Hamitonian matrices of the scattering region and the adjacent leads, which are needed for transport calculation using the nonequilibrium Green's function formalism. The coupling of the scattering region to the semi-infinite leads is described by the self-energies of the leads. Using the nonequilibrium Green's function method, one calculates self-consistently the charge distribution of the system under bias and evaluates the transmission and current through the system. To solve the Poisson equation within the scheme of MLWFs I introduce a computationally efficient method. The method is applied to a molecular hydrogen contact in two transition metal monatomic wires (Cu and Pt). It is found that for Pt the I-V characteristics is approximately linear dependence, however, for Cu the I-V characteristics manifests a linear dependence at low bias voltages and exhibits apparent nonlinearity at higher bias voltages. I have also calculated the transmission in the zero bias voltage limit for a single CO molecule adsorbed on Cu and Pt monatomic wires. While a chemical scissor effect occurs for the Cu monatomic wire with an adsorbed CO molecule, it is absent for the Pt monatomic wire due to the contribution of d-orbitals at the Fermi energy.

  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. Nanoparticle transport effect on magnetohydrodynamic mixed convection of electrically conductive nanofluids in micro-annuli with temperature-dependent thermophysical properties

    NASA Astrophysics Data System (ADS)

    Malvandi, A.; Moshizi, S. A.; Ganji, D. D.

    2017-04-01

    This is a numerical investigation of nanoparticle transport effect on magnetohydrodynamic mixed convective heat transfer of electrically conductive nanofluids in micro-annuli with temperature-dependent thermophysical properties. The modified Buongiorno's non-homogeneous model is applied for the nanoparticle-fluid suspension to simulate the migration of nanoparticles into the base fluid, originating from the thermophoresis (nanoparticle migration because of temperature gradient) and Brownian motion (nanoparticle slip velocity because of concentration gradient). Due to surface roughness at the solid-fluid interface in micro-annuli, the wall surfaces are subjected to a linear slip condition to assess the non-equilibrium region near the interface. The fluid flow has been assumed to be fully developed, and the governing equations including continuity, momentum, energy, and nanoparticle transport equation are reduced to a system of ordinary differential equations, before they have been solved numerically. The results are presented with and without considering the dependency of thermophysical properties upon the temperature. It is indicated that ignoring the temperature dependency of thermophysical properties does not significantly affect the flow fields and heat transfer behavior of nanofluids, but it changes the relative magnitudes. Furthermore, in the presence of magnetic field, smaller nanoparticles are more appropriate than larger ones.

  20. 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.

  1. 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 ...

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

    NASA Astrophysics Data System (ADS)

    Kumar, Mohit; Basu, Tanmoy; Som, Tapobrata

    2015-08-01

    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 (˜1020 cm-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.

  4. 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.

  5. Electrical transport properties of single wall carbon nanotube/polyurethane composite based field effect transistors fabricated by UV-assisted direct-writing technology

    NASA Astrophysics Data System (ADS)

    Aïssa, B.; Therriault, D.; Farahani, R. D.; Lebel, L. L.; El Khakani, M. A.

    2012-03-01

    We report on the fabrication and transport properties of single-walled carbon nanotube (SWCNT)/polyurethane (PU) nanocomposite microfiber-based field effect transistors (FETs). UV-assisted direct-writing technology was used, and microfibers consisting of cylindrical micro-rods, having different diameters and various SWCNT loads, were fabricated directly onto SiO2/Si substrates in a FET scheme. The room temperature dc electrical conductivities of these microfibers were shown to increase with respect to the SWCNT concentrations in the nanocomposite, and were about ten orders of magnitude higher than that of the pure polyurethane, when the SWCNT load ranged from 0.1 to 2.5 wt% only. Our results show that for SWCNT loads ≤ 1.5 wt%, all the microfibers behave as a FET with p-type transport. The resulting FET exhibited excellent performance, with an Ion/Ioff ratio of 105 and a maximum on-state current (Ion) exceeding 70 µA. Correlations between the FET performance, SWCNTs concentration, and the microfiber diameters are also discussed.

  6. Electrical transport properties of single wall carbon nanotube/polyurethane composite based field effect transistors fabricated by UV-assisted direct-writing technology.

    PubMed

    Aïssa, B; Therriault, D; Farahani, R D; Lebel, L L; El Khakani, M A

    2012-03-23

    We report on the fabrication and transport properties of single-walled carbon nanotube (SWCNT)/polyurethane (PU) nanocomposite microfiber-based field effect transistors (FETs). UV-assisted direct-writing technology was used, and microfibers consisting of cylindrical micro-rods, having different diameters and various SWCNT loads, were fabricated directly onto SiO₂/Si substrates in a FET scheme. The room temperature dc electrical conductivities of these microfibers were shown to increase with respect to the SWCNT concentrations in the nanocomposite, and were about ten orders of magnitude higher than that of the pure polyurethane, when the SWCNT load ranged from 0.1 to 2.5 wt% only. Our results show that for SWCNT loads ≤ 1.5 wt%, all the microfibers behave as a FET with p-type transport. The resulting FET exhibited excellent performance, with an I(on)/I(off) ratio of 10⁵ and a maximum on-state current (I(on)) exceeding 70 µA. Correlations between the FET performance, SWCNTs concentration, and the microfiber diameters are also discussed.

  7. Electrical Transport in Semiconductor Nanoparticle Arrays: Conductivity, Sensing and Modeling

    NASA Astrophysics Data System (ADS)

    Hartner, Sonja; Schwesig, Dominik; Plümel, Ingo; Wolf, Dietrich E.; Lorke, Axel; Wiggers, Hartmut

    Electrical properties of nanoparticle ensembles are dominated by interparticle transport processes, mainly due to particle-particle and particle-contact interactions. This makes their electrical properties dependent on the network properties such as porosity and particle size and is a main prerequisite for solid- state gas sensors, as the surrounding gas atmosphere influences the depletion layer surrounding each particle. Different kinds of nanoparticle arrays such as pressed pellets, printed layer, and thin films prepared by molecular beam-assisted deposition are characterized with respect to their electrical transport properties. Experimental results are shown for the electrical and sensing properties of several metal oxide nanoparticle ensembles and the influence of porosity is investigated during compaction of nanoparticle powders exposed to an external force. A model describing these properties is developed and it is shown that for a given material only porosity, geometry, and particle size influence the overall electrical properties. The model developed for the description of current transport in particulate matter can also be utilized to describe current-assisted sintering.

  8. 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.

  9. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Transport Through a Precessing Spin Coupled to Noncollinearly Polarized Ferromagnetic Leads

    NASA Astrophysics Data System (ADS)

    Wang, Xian-Chao; Xin, Zi-Hua; Feng, Li-Ya

    2010-02-01

    The quantum electronic transport through a precessing magnetic spin coupled to noncollinearly polarized ferromagnetic leads (F-MS-F) has been studied in this paper. The nonequilibrium Green function approach is used to calculate local density of states (LDOS) and current in the presence of external bias. The characters of LDOS and the electronic current are obtained. The tunneling current is investigated for different precessing angle and different configurations of the magnetization of the leads. The investigation reveals that when the precessing angle takes θ < π/2 and negative bias is applied, the resonant tunneling current appears, otherwise, it appears when positive bias is applied. When the leads are totally polarized and the precessing angel takes 0, the tunneling current changes with the configuration of two leads; and it becomes zero when the two leads are antiparallel.

  10. Enhanced electrical property of Ni-doped CoOx hole transport layer for inverted perovskite solar cells.

    PubMed

    Huang, Aibin; Yu, Yu; Liu, Yan; Yang, Songwang; Lei, Lei; Bao, Shanhu; Cao, Xun; Jin, Ping

    2017-03-15

    Ultrathin Ni doped CoOx (Ni:CoOx) films were demonstrated by direct current (DC) co-sputtering at room temperature and employed as inorganic hole transport materials for inverted perovskite solar cells. P-type Ni2+ doping introduced in this work was designed to adjust the valence band position of CoOx to match the highest occupied molecular orbital of perovskite absorber material (CH3NH3PbI3), which would effectively inhibit recombination of photo-induced electrons and holes. Moreover, the hole extraction capacity would be further enhanced as a result of the appropriate Ni2+ doping, and hence the power conversion efficiency (PCE) of the devices increased from 3.68% to 9.60%. The optimized performance was also accompanied by decent stability as a result of its intrinsic stability and conductivity.

  11. Physical properties of electricity.

    PubMed

    Thomson, Angus J M

    2013-01-01

    Electricity is the flow of electrons through a conductor. The amount of current (amps) is related to the voltage (volts) pushing the electrons and the degree of resistance to flow (ohms). During their flow around a circuit, electrons can be used to create a number of useful byproducts such as heat and light. As electrons flow, they alter the charge of the matter they flow through, which may also generate electromagnetic effects.

  12. Role of self-assembled monolayer passivation in electrical transport properties and flicker noise of nanowire transistors.

    PubMed

    Kim, Seongmin; Carpenter, Patrick D; Jean, Rand K; Chen, Haitian; Zhou, Chongwu; Ju, Sanghyun; Janes, David B

    2012-08-28

    Semiconductor nanowires have achieved great attention for integration in next-generation electronics. However, for nanowires with diameters comparable to the Debye length, which would generally be required for one-dimensional operation, surface states degrade the device performance and increase the low-frequency noise. In this study, single In(2)O(3) nanowire transistors were fabricated and characterized before and after surface passivation with a self-assembled monolayer of 1-octadecanethiol (ODT). Electrical characterization of the transistors shows that device performance can be enhanced upon ODT passivation, exhibiting steep subthreshold slope (~64 mV/dec), near zero threshold voltage (~0.6 V), high mobility (~624 cm(2)/V·s), and high on-currents (~40 μA). X-ray photoelectron spectroscopy studies of the ODT-passivated nanowires indicate that the molecules are bound to In(2)O(3) nanowires through the thiol linkages. Device simulations using a rectangular geometry to represent the nanowire indicate that the improvement in subthreshold slope and positive shift in threshold voltage can be explained in terms of reduced interface trap density and changes in fixed charge density. Flicker (low-frequency, 1/f) noise measurements show that the noise amplitude is reduced following passivation. The interface trap density before and after ODT passivation is profiled throughout the band gap energy using the subthreshold current-voltage characteristics and is compared to the values extracted from the low-frequency noise measurements. The results indicate that self-assembled monolayer passivation is a promising optimization technology for the realization of low-power, low-noise, and fast-switching applications such as logic, memory, and display circuitry.

  13. 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}.

  14. Structural, magnetic and electrical transport properties in electron-doped La0.85Hf0.15MnO3 epitaxial film

    NASA Astrophysics Data System (ADS)

    Han, Li-an; Ma, Zi-wei; Zhu, Hua-ze; Chen, Chang-le; Zhang, Tao

    2017-03-01

    Using a pulsed laser deposition method, the electron-doped La0.85Hf0.15MnO3 (LHMO) film with the thickness of 90 nm was epitaxially grown on LaAlO3 (001) single crystal substrate. The structural, magnetic and electrical transport properties of the film have been studied comprehensively. The X-ray diffraction patterns confirm that LHMO film is of single phase, good quality and c axis orientation. The film undergoes a ferromagnetic-like ordering to paramagnetic states at T C =280 K. Moreover, a spin glass behavior observed in the film may be attributed to the strain effects. Using the percolation theory, we have analyzed the resistivity data ρ (T) of the film and given an excellent fit in the whole temperature range. Particularly, large temperature coefficient of resistance of 11.27% K- 1 has been discovered near sub-room-temperature, indicating that LHMO film could be useful for bolometric applications.

  15. Surface morphological, electrical and transport properties of rapidly annealed double layers Ru/Cr Schottky structure on n-type InP

    NASA Astrophysics Data System (ADS)

    Shanthi Latha, K.; Rajagopal Reddy, V.

    2017-02-01

    The electrical and transport properties of a fabricated bilayer Ru/Cr/n-InP Schottky diode (SD) have been investigated at different annealing temperatures. Atomic force microscopy results have showed that the overall surface morphology of the Ru/Cr/n-InP SD is fairly smooth at elevated temperatures. High barrier height is achieved for the diode annealed at 300 °C compared to the as-deposited, annealed at 200 and 400 °C diodes. The series resistance and shunt resistance of the Ru/Cr/n-InP SD are estimated by current-voltage method at different annealing temperatures. The barrier heights and series resistance are also determined by Cheung's and modified Norde functions. The interface state density of the Ru/Cr/n-InP SD is found to be decreased after annealing at 300 °C and then slightly increased upon annealing at 400 °C. The difference between barrier heights obtained from current-voltage and capacitance-voltage is also discussed. Experimental results have showed that the Poole-Frenkel emission is found to be dominant in the lower bias region whereas Schottky emission is dominant in the higher bias region for the Ru/Cr/n-InP SDs irrespective of annealing temperatures.

  16. 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.

  17. Electrical Transport Properties of Epitaxial and Granular Oriented Yttrium BARIUM(2) COPPER(3) OXYGEN(7-DELTA) Thin Films

    NASA Astrophysics Data System (ADS)

    Jones, Edwin Clay

    1992-01-01

    Strong correlations between the Hall coefficient R_{H}, the transition temperature T_{c}, and the critical current density J_{c} were established in a series of epitaxial YBa_2Cu_3O_ {7-delta} thin films as a function of oxygen deficiency delta. Steady increases in R_{H} with delta suggests that dexoygenation reduces the density of states which, according to BCS theory, should lead to corresponding decreases in T_ {c}. In contrast, two well known plateaus occurring at 90K and 60K were observed in T _{c} vs. delta . Others have ascribed these plateaus to either electronic phenomena or oxygen clustering. We find that in the 90K plateau, the critical current density J _{c}(delta ,H = 0) decreased with delta and extrapolates toward zero at the edge of the plateau, while the relative field dependence of J_ {c}(delta,H) is independent of delta. Furthermore, a fluctuation analysis of the resistive transitions indicates a constant upper critical field B_{ c2}(0) = 110T across this plateau. These observations suggest that the oxygen clustering/percolation scenario occurs on the 90K plateau. Moreover, computer simulations showed this oxygen clustering/percolation picture to be a plausible explanation for the occasional observation of a sign reversal of R _{H} near T _{c}. For large oxygen deficiencies (delta > 0.5) and for the granular oriented YBa_2Cu_3O _{7-delta} thin films, rapid decreases in J_{c} with applied field were observed which is reminiscent of the conventional granular alloys. In addition, the self -field critical current densities J_{c} behaved as SNS weak link systems in a Josephson mixed state. In sum, due to the short coherence length xi in these materials, many properties formerly believed to be "intrinsic" in nature are apparently "extrinsic" in nature.

  18. Electrical properties of complex tungsten bronze ceramics

    NASA Astrophysics Data System (ADS)

    Padhee, R.; Das, Piyush R.

    2014-09-01

    This paper highlights the electrical properties of two new complex tungsten bronze ceramics (K2Pb2Eu2W2Ti4Nb4O30 and K2Pb2Pr2W2Ti4Nb4O30) which were prepared by high temperature mixed oxide method. Variation of impedance parameters with temperature (27-500 °C) and frequency (1 kHz to 5 MHz) shows the grain and grain boundary effects in the samples. The variation of dielectric parameters with frequency is also studied. The ac conductivity variation with temperature clearly exhibits that the materials have thermally activated transport properties of Arrhenius type.

  19. Effect of sintering conditions on the electrical-transport properties of the SrZrO3-based protonic ceramic electrolyser membrane

    NASA Astrophysics Data System (ADS)

    Heras-Juaristi, Gemma; Pérez-Coll, Domingo; Mather, Glenn C.

    2016-11-01

    The effects of sintering temperature and addition of 4 mol.% ZnO as sintering additive on the crystal structure, microstructure and electrical properties of SrZr0.9Y0.1O3-δ are reported. The presence of ZnO as sintering aid brings about high densification at 1300 °C (relative density ∼97%); gas-tightness is not achieved for ZnO-free samples sintered below 1600 °C. Bulk conductivity (σB) is considerably higher in wet and dry O2 on doping with ZnO, but only slight variations of σB with sintering temperature are observed for the Zn-containing phases. Similarly, the apparent grain-boundary conductivities are much greater for the Zn-doped samples. The grain-boundary volume and accompanying resistances are much reduced on sintering at 1500 °C with ZnO addition in comparison to Zn-modified samples sintered below 1500 °C, with only minor changes in grain-boundary relaxation frequency observed. Conversely, in comparison to the undoped sample with sintering temperature of 1600 °C, there is an enormous improvement in the specific grain-boundary conductivity of two orders of magnitude for the ZnO-containing samples. Analysis on the basis of the core space-charge-layer model relates the enhancement of the grain-boundary transport to a higher concentration of charge carriers in the space-charge layer and associated lower potential barrier heights.

  20. Transport properties of alumina nanofluids.

    PubMed

    Wong, Kau-Fui Vincent; Kurma, Tarun

    2008-08-27

    Recent studies have showed that nanofluids have significantly greater thermal conductivity compared to their base fluids. Large surface area to volume ratio and certain effects of Brownian motion of nanoparticles are believed to be the main factors for the significant increase in the thermal conductivity of nanofluids. In this paper all three transport properties, namely thermal conductivity, electrical conductivity and viscosity, were studied for alumina nanofluid (aluminum oxide nanoparticles in water). Experiments were performed both as a function of volumetric concentration (3-8%) and temperature (2-50 °C). Alumina nanoparticles with a mean diameter of 36 nm were dispersed in water. The effect of particle size was not studied. The transient hot wire method as described by Nagaska and Nagashima for electrically conducting fluids was used to test the thermal conductivity. In this work, an insulated platinum wire of 0.003 inch diameter was used. Initial calibration was performed using de-ionized water and the resulting data was within 2.5% of standard thermal conductivity values for water. The thermal conductivity of alumina nanofluid increased with both increase in temperature and concentration. A maximum thermal conductivity of 0.7351 W m(-1) K(-1) was recorded for an 8.47% volume concentration of alumina nanoparticles at 46.6 °C. The effective thermal conductivity at this concentration and temperature was observed to be 1.1501, which translates to an increase in thermal conductivity by 22% when compared to water at room temperature. Alumina being a good conductor of electricity, alumina nanofluid displays an increasing trend in electrical conductivity as volumetric concentration increases. A microprocessor-based conductivity/TDS meter was used to perform the electrical conductivity experiments. After carefully calibrating the conductivity meter's glass probe with platinum tip, using a standard potassium chloride solution, readings were taken at

  1. 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

  2. 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.

  3. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Spin-Polarized Transport through a Quantum Dot Coupled to Ferromagnetic Leads and a Mesoscopic Ring

    NASA Astrophysics Data System (ADS)

    Huang, Rui; Wu, Shao-Quan

    2010-02-01

    Using an equation of motion technique, we investigate the spin-polarized transport through a quantum dot coupled to ferromagnetic leads and a mesoscopic ring by the Anderson Hamiltonian. We analyze the transmission probability of this system in both the equilibrium and nonequilibrium cases, and our results reveal that the transport properties show some noticeable characteristics depending upon the spin-polarized strength p, the magnetic flux Φ and the number of lattice sites NR in the mesoscopic ring. These effects might have some potential applications in spintronics.

  4. Future drive: Electric vehicles and sustainable transportation

    SciTech Connect

    Sperling, D.

    1996-07-01

    This book discusses the future of electric vehicles by starting with two premises: (1) improvements in the environmental and economic performance of our transportation systems are being overwhelmed by rapid increases in the number of people, cars, and miles traveled, and (2) when we shape our transportation future, we must respect peoples` preferred mode of travel, the private car. An assessment of developing technologies is presented along with the key issues of how new automotive technologies should be integrated into our lives and what types of regulatory reform would facilitate needed changes.

  5. 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.

  6. 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.

  7. Low-frequency electrical properties.

    USGS Publications Warehouse

    Olhoeft, G.R.

    1985-01-01

    In the interpretation of induced polarization data, it is commonly assumed that metallic mineral polarization dominantly or solely causes the observed response. However, at low frequencies, there is a variety of active chemical processes which involve the movement or transfer of electrical charge. Measurements of electrical properties at low frequencies (such as induced polarization) observe such movement of charge and thus monitor many geochemical processes at a distance. Examples in which this has been done include oxidation-reduction of metallic minerals such as sulfides, cation exchange on clays, and a variety of clay-organic reactions relevant to problems in toxic waste disposal and petroleum exploration. By using both the frequency dependence and nonlinear character of the complex resistivity spectrum, these reactions may be distinguished from each other and from barren or reactionless materials.-Author

  8. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Wave-Vector and Temperature-Dependent Electron Transport in a Magnetic Nanostructure Modulated by Bias

    NASA Astrophysics Data System (ADS)

    Lu, Jian-Duo; Li, Yun-Bao; Wang, Yu-Hua; Hou, Yang-Lai

    2010-08-01

    We theoretically investigate the wave-vector and temperature-dependent electron transport in a magnetic nanostructure modulated by an applied bias. The large spin-polarization can be achieved in such a device, and the degree of spin-polarization strongly depends on the transverse wave-vector and the temperature. These interesting properties may be helpful to spin-polarize electrons into semiconductors, and this device may be used as a spin filter.

  9. 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.

  10. Electrical transport in thin films of copper silicide

    NASA Astrophysics Data System (ADS)

    Aboelfotoh, M. O.; Krusin-Elbaum, L.

    1991-09-01

    Electrical properties of thin films of η'-Cu3Si phase with a tetragonal crystal structure are reported on. Electrical transport in these films is found to be very sensitive to oxygen exposure. Cu3Si reacts with oxygen at room temperature to form both Si and Cu oxides, resulting in high-room-temperature (˜60 μΩ cm) and even nonmetallic resistivity. This behavior is contrasted with that of low-resistivity (˜5 μΩ cm at room temperature) Cu3Ge, which is inert in an oxygen environment.

  11. Hybrid Electric Propulsion Technologies for Commercial Transports

    NASA Technical Reports Server (NTRS)

    Bowman, Cheryl; Jansen, Ralph; Jankovsky, Amy

    2016-01-01

    NASA Aeronautics Research Mission Directorate has set strategic research thrusts to address the major drivers of aviation such as growth in demand for high-speed mobility, addressing global climate and capitalizing in the convergence of technological advances. Transitioning aviation to low carbon propulsion is one of the key strategic research thrust and drives the search for alternative and greener propulsion system for advanced aircraft configurations. This work requires multidisciplinary skills coming from multiple entities. The Hybrid Gas-Electric Subproject in the Advanced Air Transportation Project is energizing the transport class landscape by accepting the technical challenge of identifying and validating a transport class aircraft with net benefit from hybrid propulsion. This highly integrated aircraft of the future will only happen if airframe expertise from NASA Langley, modeling and simulation expertise from NASA Ames, propulsion expertise from NASA Glenn, and the flight research capabilities from NASA Armstrong are brought together to leverage the rich capabilities of U.S. Industry and Academia.

  12. 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

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

    DOE PAGES

    Zhu, Jinlong; Yang, Liuxiang; Wang, Hsiu -Wen; ...

    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

  14. Electrical Properties of Phospholipid Vesicles

    PubMed Central

    Schwan, H. P.; Takashima, S.; Miyamoto, V. K.; Stoeckenius, W.

    1970-01-01

    The capacitance of the membrane of phospholipid vesicles and the electrical properties of the vesicle interior have been determined. To this end the electrical properties of phospholipid vesicles have been investigated over a frequency range extending from 1 kHz to 100 MHz. The dielectric behavior is characterized by two dispersions, one placed between 1 kHz and 1 MHz and the other between 1 and 100 MHz. The relaxational behavior at low frequencies is explained by counterion movement tangential to the vesicle surface and a reasonable value for the fixed charge of the vesicles is calculated from the dispersion magnitude. The relaxation at high frequencies is of the Maxwell-Wagner type and appears caused by the phospholipid bilayer bounding the interior phase of the vesicles. It is consistent with the existence of a closed bilayer with a capacitance of about 2 μF/cm2 and an internal phase similar to the vesicle suspending medium. There is no indication of other than normally structured water inside the small vesicles. PMID:5471701

  15. Neoclassical transport properties and their limits in NSTX

    NASA Astrophysics Data System (ADS)

    Houlberg, W. A.; Strand, P. I.; Shaing, K. C.

    2001-10-01

    The low aspect ratio and low toroidal field of NSTX enhance its neoclassical transport properties, but also push the limits of standard neoclassical models. Particle and energy transport, plasma rotation, the radial electric field, and bootstrap current are examined for typical NSTX discharges. Regimes of inward and outward impurity transport driven by a combination of the inductive electric field (Ware pinch), inward transport on the deuterium density gradient, and outward transport on the ion temperature gradient are identified. Orbit losses and atomic physics effects near the plasma boundary lead to modifications in the bootstrap current and impurity transport properties in the H-mode pedestal. Potato orbit effects near the axis, included as a viscosity modification, can enhance the ion energy transport, but are reduced by orbit squeezing. The low aspect ratio and high beta of NSTX plasmas provide a critical test of the limits of neoclassical theory.

  16. 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

  17. 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.

  18. Electric transport in three-dimensional skyrmion/monopole crystal

    NASA Astrophysics Data System (ADS)

    Zhang, Xiao-Xiao; Mishchenko, Andrey S.; De Filippis, Giulio; Nagaosa, Naoto

    2016-11-01

    We study theoretically the transport properties of a three-dimensional spin texture made from three orthogonal helices, which is essentially a lattice of monopole-antimonopole pairs connected by skyrmion strings. This spin structure is proposed for MnGe based on neutron scattering experiments as well as Lorentz transmission electron microscopy observations. Equipped with a sophisticated spectral analysis method, we adopt the finite temperature Green's function technique to calculate the longitudinal dc electric transport in such a system. We consider conduction electrons interacting with spin waves of the topologically nontrivial spin texture, wherein fluctuations of monopolar emergent magnetic fields enter. We study in detail the behavior of electric resistivity under the influence of temperature, external magnetic field, and a characteristic monopole motion, especially a novel magnetoresistivity effect describing the latest experimental observations in MnGe, wherein a topological phase transition signifying strong correlations is identified.

  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. 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.

  1. 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.

  2. 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.

  3. Magnetism, half-metallicity and electrical transport properties of V- and Cr-doped semiconductor SnTe: A theoretical study

    SciTech Connect

    Liu, Y.; Bose, S. K.; Kudrnovský, J.

    2013-12-07

    This work presents results for the electronic structure, magnetic properties, and electrical resistivity of the semiconductor SnTe doped with 3d transition metals V and Cr. From the standpoint of potential application in spintronics, we look for half-metallic states and analyze their properties in both rock salt and zinc blende structures using ab initio electronic structure methods. In both cases, it is the Sn-sublattice that is doped with the transition metals, as has been the case with experiments performed so far. We find four half-metallic compounds at their optimized cell volumes. Results of exchange interactions and the Curie temperature are presented and analyzed for all the relevant cases. Resistivity calculation based on Kubo-Greenwood formalism shows that the resistivities of these alloys due to transition metal doping of the Sn-sublattice may vary, in most cases, from typical liquid metal or metallic glass value to 2–3 times higher. 25% V-doping of the Sn-sublattice in the rock salt structure gives a very high resistivity, which can be traced to high values of the lattice parameter resulting in drastically reduced hopping or diffusivity of the states at the Fermi level.

  4. Transport properties in the atmosphere of Jupiter

    NASA Technical Reports Server (NTRS)

    Biolsi, L., Jr.

    1979-01-01

    Activities reported include: (1) testing of the computer program used to obtain transport properties for the Hulburt-Hirschfelder potential; (2) calculation of transport properties for the C2-C interaction; (3) preliminary calculations for the C2-C2 interaction; (4) calculation of transport properties for the C2H-He interaction; (5) consideration of the effect of inelastic collisions on the transport properties; and (6) the use of the Hulburt-Hirschfelder potential to model ion-atom interactions.

  5. 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.

  6. Electrical transport engineering of semiconductor superlattice structures

    NASA Astrophysics Data System (ADS)

    Shokri, Aliasghar

    2014-04-01

    We investigate the influence of doping concentration on band structures of electrons and electrical transmission in a typical aperiodic semiconductor superlattice consisting of quantum well and barrier layers, theoretically. For this purpose, we assume that each unit cell of the superlattice contains alternately two types of material GaAs (as a well) and GaAlAs (as a barrier) with six sublayers of two materials. Our calculations are based on the generalized Kronig-Penny (KP) model and the transfer matrix method within the framework of the parabolic conductance band effective mass approximation in the coherent regime. This model reduces the numerical calculation time and enables us to use the transfer matrix method to investigate transport in the superlattices. We show that by varying the doping concentration and geometrical parameters, one can easily block the transmission of the electrons. The numerical results may be useful in designing of nanoenergy filter devices.

  7. 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.

  8. 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.

  9. Electrical transport properties and modelling of electrostrictive resonance phenomena in Ba2/3Sr1/3TiO3 thin films

    NASA Astrophysics Data System (ADS)

    Ghalem, A.; Huitema, L.; Crunteanu, A.; Rammal, M.; Trupina, L.; Nedelcu, L.; Banciu, M. G.; Dutheil, P.; Constantinescu, C.; Marchet, P.; Dumas-Bouchiat, F.; Champeaux, C.

    2016-11-01

    We present the conduction mechanisms of Ba2/3Sr1/3TiO3 thin films integrated in metal-insulator-metal (MIM) capacitors and the modelling of the frequency-dependent electrostrictive resonances (in the 100 MHz-10 GHz domain) induced in the devices upon applying different voltage biases. Au/BST/Ir MIM structures on MgO substrates have been fabricated and, depending on their specific polarization, we highlighted different conduction mechanisms in the devices. Depending on the dc bias polarity, the conduction current across the material shows a space-charge-limited-current behavior under negative polarization, whereas under positive bias, the conduction obeys an electrode-limited Schottky-type law at the Au/BST interface. The application of an electric field on the device induces the onset of acoustic resonances related to electrostrictive phenomena in the ferroelectric material. We modeled these acoustic resonances over a wide frequency range, by using a modified Lakin model, which takes into account the dispersions of acoustic properties near the lower electrode/thin film interface.

  10. 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.

  11. 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.

  12. Electrical Transport in Thin Films of Doped Silicon Nanocrystals

    NASA Astrophysics Data System (ADS)

    Chen, Ting

    Colloidal semiconductor nanocrystals (NCs) have shown great potential for thin-film optoelectronics, such as solar cells and light emitting diodes (LEDs), due to their size-tunable electronic properties and solution processability. Significant progress has been made in developing synthetic methods to prepare high quality NCs, achieving controllable doping, and integrating NCs into high performance electronic devices. Most electronic applications rely on the electrical conduction through NC films, therefore, fundamental understanding of the carrier transport in NC films is required to further improve device performance and provide guide for future device design. My research is inspired by the successful achievement of a highly efficient LED with hydrosilylated Si NCs as the emissive layer. To better understand the electrical conduction in the Si NC system, a systematic study of the temperature and electric-field dependence of the film conductivity is performed. It shows that the conductivity of the Si NC film is limited by the ionization of rare NCs containing donor impurities and the carrier transport follows nearest neighbor hopping. The Si NCs are inherently doped with a very small concentration of impurities, about 1 donor per 1000 NCs. This is also the first study of carrier transport in a lightly doped NC system, and results obtained in this work can apply to other NC materials as well. The organic ligands used to passivate NC surface are necessary to achieve strong photoluminescence, however, they inhibit the carrier transport due to the resulting large tunneling barrier between neighboring NCs. The localization length estimated from the temperature data in the high electric field regime is about 1 nm. In addition, the activation energy required for conduction also depends on the surrounding medium of NCs, the electrical conduction can be improved by reducing the activation energy through engineering of the matrix of NC arrays. Doping is critical to enable

  13. 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.

  14. 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.

  15. Electrical Properties of Thin Films of Alumina.

    DTIC Science & Technology

    The report consists of a literature survey on the electrical properties of alumina and aluminum oxide thin films . A bibliographic listing of reports is included along with abstracts from most of them.

  16. Influence of Oxidation on Electrical Properties of Compacted Cu Nanopowders

    NASA Astrophysics Data System (ADS)

    Nadutov, Volodymyr; Perekos, Anatoliy; Kokorin, Volodymyr; Konoplyuk, Sergiy; Kabantsev, Taras

    2016-10-01

    The phase composition and electrical transport properties of Cu powder obtained by electric spark dispersion and the pellets manufactured from this powder were studied by X-ray phase analysis and electric resistance measurements. The compacted powders were annealed in pure Ar atmosphere. It was shown that electrical resistance of the compacted Cu specimens essentially depends on the annealing temperature. In particular, the electrical resistance of the pellet after annealing at 873 K decreases on heating at low temperatures (semiconducting mechanism). As the temperature is increased, semiconducting behavior of resistivity is altered for metallic one. This change of conductivity type is ascribed to formation of metallic oxide and modification of its content during annealing.

  17. Influence of Oxidation on Electrical Properties of Compacted Cu Nanopowders.

    PubMed

    Nadutov, Volodymyr; Perekos, Anatoliy; Kokorin, Volodymyr; Konoplyuk, Sergiy; Kabantsev, Taras

    2016-12-01

    The phase composition and electrical transport properties of Cu powder obtained by electric spark dispersion and the pellets manufactured from this powder were studied by X-ray phase analysis and electric resistance measurements. The compacted powders were annealed in pure Ar atmosphere. It was shown that electrical resistance of the compacted Cu specimens essentially depends on the annealing temperature. In particular, the electrical resistance of the pellet after annealing at 873 K decreases on heating at low temperatures (semiconducting mechanism). As the temperature is increased, semiconducting behavior of resistivity is altered for metallic one. This change of conductivity type is ascribed to formation of metallic oxide and modification of its content during annealing.

  18. Electronic transition and electrical transport properties of delafossite CuCr1-xMgxO2 (0 ≤ x ≤ 12%) films prepared by the sol-gel method: A composition dependence study

    NASA Astrophysics Data System (ADS)

    Han, M. J.; Duan, Z. H.; Zhang, J. Z.; Zhang, S.; Li, Y. W.; Hu, Z. G.; Chu, J. H.

    2013-10-01

    Highly transparent CuCr1-xMgxO2 (0 ≤ x ≤ 12%) films were prepared on (001) sapphire substrates by sol-gel method. The microstructure, phonon modes, optical band gap, and electrical transport properties have been systematically discussed. It was found that Mg-doping improved the crystal quality and enhanced the (00l) preferred orientation. The spectral transmittance of films approaches about 70%-75% in the visible-near-infrared wavelength region. With increasing Mg-composition, the optical band gap first declines and climbs up due to the band gap renormalization and Burstein-Moss effect. The direct and indirect band gaps of CuCr0.94Mg0.06O2 film are 3.00 and 2.56 eV, respectively. In addition, it shows a crossover from the thermal activation behavior to that of three-dimensional variable range hopping from temperature-dependent electrical conductivity. The crossover temperature decreases with increasing Mg-doping composition, which can be ascribed to the change of spin-charge coupling between the hole and the local spin at Cr site. It should be noted that the electrical conductivity of CuCr1-xMgxO2 films becomes larger with increasing x value. The highest electrical conductivity of 3.85 S cm-1 at room temperature for x = 12% is four-order magnitude larger than that (8.81 × 10-4 S cm-1) for pure CuCrO2 film. The high spectral transmittance and larger conductivity indicate that Mg-doped CuCrO2 films are promising for optoelectronic device applications.

  19. 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)

  20. Optical and electrical properties of nanostructured metallic electrical contacts

    NASA Astrophysics Data System (ADS)

    Toranzos, Victor J.; Ortiz, Guillermo P.; Mochán, W. Luis; Zerbino, Jorge O.

    2017-01-01

    We study the optical and electrical properties of silver films with a graded thickness obtained through metallic evaporation in vacuum on a tilted substrate to evaluate their use as semitransparent electrical contacts. We measure their ellipsometric coefficients, optical transmissions and electrical conductivity for different widths, and we employ an efficient recursive method to calculate their macroscopic dielectric function, their optical properties and their microscopic electric fields. The topology of very thin films corresponds to disconnected islands, while very wide films are simply connected. For intermediate widths the film becomes semicontinuous, multiply connected, and its microscopic electric field develops hotspots at optical resonances which appear near the percolation threshold of the conducting phase, yielding large ohmic losses that increase the absorptance above that of a corresponding homogeneous film. Optimizing the thickness of the film to maximize its transmittance above the percolation threshold of the conductive phase we obtained a film with transmittance T  =  0.41 and a sheet resistance Rs\\text{max}≈ 2.7 Ω . We also analyze the observed emission frequency shift of porous silicon electroluminescent devices when Ag films are used as solid electrical contacts in replacement of electrolytic ones.

  1. Electrical properties with relaxation through human blood

    PubMed Central

    Abdalla, S.; Al-ameer, S. S.; Al-Magaishi, S. H.

    2010-01-01

    The present work aims to study the effects of the blood-microstructure on the electrical conduction from two different but correlated properties: Electrical and mechanical (viscosity), and to derive useful parameters for the evaluation of electrical conduction as a function of the blood viscosity. ac-conductivity and dielectric constant of normal and diabetic blood are measured in the frequency range 10 kHz–1 MHz at the room temperature. An empirical relation relating the resistivity and viscosity of the blood has been presented. The results show that a microfluidic device is a viable and simple solution for determination of electrical and rheological behaviors of blood samples. PMID:20686650

  2. Compositional control of electrical transport properties in the new series of defect thiospinels, Ga{sub 1-x}Ge{sub x}V{sub 4}S{sub 8-{delta}} (0<=x<=1)

    SciTech Connect

    Szkoda, Iwona; Vaqueiro, Paz; McDowall, Andrew; Powell, Anthony V.; Ritter, Clemens

    2009-10-15

    A new series of non-stoichiometric sulfides Ga{sub 1-x}Ge{sub x}V{sub 4}S{sub 8-{delta}} (0<=x<=1; delta<=0.23) has been synthesized at high temperatures by heating stoichiometric mixtures of the elements in sealed quartz tubes. The samples have been characterized by powder X-ray diffraction, SQUID magnetometry and electrical transport-property measurements. Structural analysis reveals that a solid solution is formed throughout this composition range, whilst thermogravimetric data reveal sulfur deficiency of up to 2.9% in the quaternary phases. Magnetic measurements suggest that the ferromagnetic behavior of the end-member phase GaV{sub 4}S{sub 8} is retained at x<=0.7; samples in this composition range showing a marked increase in magnetization at low temperatures. By contrast Ga{sub 0.25}Ge{sub 0.75}V{sub 4}S{sub 8-{delta}} appears to undergo antiferromagnetic ordering at ca. 15 K. All materials with xnot =1 are n-type semiconductors whose resistivity falls by almost six orders of magnitude with decreasing Ga content, whilst the end-member phase GeV{sub 4}S{sub 8-{delta}} is a p-type semiconductor. The results demonstrate that the physical properties are determined principally by the degree of electron filling of narrow-band states arising from intracluster V-V interactions. - Graphical abstract: Chemical substitution and sulfur non-stoichiometry produce dramatic changes in the transport properties of defect thiospinels Ga{sub 1-x}Ge{sub x}V{sub 4}S{sub 8-{delta}}.

  3. Study on the electrical transport properties of La2/3Ba1/3MnO3:Ag0.04/LaAlO3 (001) films

    NASA Astrophysics Data System (ADS)

    Liu, Xiang; Zhao, Shuang; Zhang, Shao-Chun

    2017-01-01

    La2/3Ba1/3MnO3: wt%Agx (LBMO:Agx, x=0.04) films were prepared on single crystalline (001)-orientated LaAlO3 substrates by pulsed laser deposition technique. All the samples show along the (00l) orientation in rhombohedral structure with R3c space group. The surface roughness (Ra), insulator-metal transition temperature (Tp) and resistivity at Tp (ρTp) of the LBMO:Ag0.04 films reached optimal values of 3.29 nm, 288 K and 0.033 Ω cm at 740 °C, respectively. The improvement of electrical transport properties in the films are attributed to the optimal growth temperature and Ag-doping improve the microstructure of the surfaces, grain boundaries (GBs) in connectivity and better crystallization. In addition, the electrical conduction behaviors can be well fitted with the grain/domain boundary, electron-electron and magnon scattering mechanisms in the ferromagnetic metallic region (TTp).

  4. Anisotropic electrical and lattice transport properties of ordered quaternary phases Cr2TiAlC2 and Mo2TiAlC2: A first principles study

    NASA Astrophysics Data System (ADS)

    Li, Y. F.; Ding, Y. C.; Xiao, B.; Cheng, Y. H.

    2016-11-01

    Electrical conductivities of Cr2TiAlC2 and Mo2TiAlC2 in a and c directions are calculated from semi-classic Boltzmann transport theory. The values are found to be σa = 5.68 ×105 S /m (6.56 ×105 S /m) and σc = 2.15 ×105 S /m (2.69 ×105 S /m) for Cr2TiAlC2 (Mo2TiAlC2) at 300 K. Using the phonon-mode Debye temperature and Slack-model, the lattice thermal conductivities in the two directions are also evaluated, and the values are κa = 18.71 W /m K (16.11 W/m K) and κc = 0.48 W /m K (0.25 W /m K) for Cr2TiAlC2 (Mo2TiAlC2) at room temperature. The anisotropy in lattice thermal conductivity is found to be stronger than that of electrical conductivity. The predicted Seebeck coefficients and thermoelectric figure of merit (ZT) indicate that they are poor thermoelectric materials. Due to the relatively high conductivities, they might be used to fabricate high temperature conductive components in aerospace industry. In addition, our results in a direction have the direct implications for the relevant properties of MXenes (Cr2TiC2 and Mo2TiC2), produced from their bulk phases.

  5. 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.

  6. Neoclassical Radial Electric Field and Transport with Finite Orbits

    SciTech Connect

    Wang, W. X.; Hinton, F. L.; Wong, S. K.

    2001-07-30

    Neoclassical transport in a toroidal plasma with finite ion orbits is studied, including for the first time the self-consistent radial electric field. Using a low-noise {delta}f particle simulation, we demonstrate that a deep electric-field well develops in a region with a steep density gradient, because of the self-collision--driven ion flux. We find that the electric field agrees with the standard neoclassical expression, when the toroidal rotation is zero, even for a steep density gradient. Ion thermal transport is modified by the electric-field well in a way which is consistent with the orbit squeezing effect, but smoothed by the finite orbits.

  7. Preparation of ferroelectric field effect transistor based on sustainable strongly correlated (Fe,Zn)3O4 oxide semiconductor and their electrical transport properties

    NASA Astrophysics Data System (ADS)

    Takaobushi, Junichi; Kanki, Teruo; Kawai, Tomoji; Tanaka, Hidekazu

    2011-03-01

    We have constructed a field effect transistor structure composed of the sustainable oxide semiconductor (Fe,Zn)3O4 with high Curie temperature and ferroelectric Pb(Zr,Ti)O3. Electric field control of (Fe2.5Zn0.5)O4 channel resistance was achieved in the heterostructures though modulation of their carrier concentration. The results will lead to the significant development of sustainable oxide semiconductor spintronics devices working at room temperature.

  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/lubrican...

  9. 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.

  10. Electrical properties of single CdTe nanowires.

    PubMed

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

    2015-01-01

    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.

  11. 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

  12. Electrical transport properties of In-doped Ce(1-x)In(x)O(2-delta) (x = 0.1; 0.2).

    PubMed

    Bhella, Surinderjit Singh; Kuti, Lisa M; Li, Qin; Thangadurai, Venkataraman

    2009-11-21

    We report the synthesis and electrical conductivity of fluorite-type Ce(1-x)In(x)O(2-delta) (x = 0.1; 0.2) in air, dry Ar, N(2) and H(2) in the temperature range of 300-800 degrees C. We have employed a new CO(2) capture technique to prepare the "metastable" fluorite-related structure Ce(1-x)In(x)O(2-delta) from the corresponding In-doped Ba-containing perovskite of the nominal chemical formula BaCe(1-x)In(x)O(3-delta) at 800 degrees C. The amount of CO(2) gained per ceramic gram was found to be consistent with the formation of BaCO(3), confirming the complete leaching of Ba in BaCe(1-x)In(x)O(3-delta). The CO(2) capture efficiency was found to be in the range of 90-99% at 800 degrees C, which is significantly higher than those of well-known low-temperature CO(2) absorbing materials, including Li(2)O, Li(6)Zr(2)O(7), Li(1.8)Na(0.2)ZrO(3) and LiNaZrO(3). Powder X-ray diffraction (PXRD) and energy dispersive X-ray analysis (EDAX) confirmed the perovskite into fluorite structural transformation reaction. The AC impedance study showed a clear intercept to the real axis at the low-frequency over the investigated temperatures in all the atmospheres, indicating a non-blocking nature of electrode (Pt) and electrolyte interface. The constant phase element (CPE) value was found to be in the order of 10(-10) F in air, N(2) and Ar for high-frequency part of the semicircle due to bulk contribution, and about two orders of magnitude lower values were observed for the low-frequency semicircle which may correspond to grain-boundary effect. The 20 mol% In-doped CeO(2) exhibits a total electrical conductivity of about 4 x 10(-6) S/cm at 600 degrees C in Ar, while in H(2) an about four orders of magnitude higher electrical conductivity of 3 x 10(-2) S/cm was observed. The activation energy for electrical conductivity was found to be 1.36 eV in Ar, 1.43 eV in N(2), 1.34 eV in H(2), and 1.1 eV in air for Ce(0.8)In(0.2)O(1.9).

  13. 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.

  14. 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

    2013-12-07

    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.

  15. 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.

  16. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Spin-dependent electron transport of a waveguide with Rashba spin-orbit coupling in an electromagnetic field

    NASA Astrophysics Data System (ADS)

    Xiao, Xian-Bo; Li, Xiao-Mao; Chen, Yu-Guang

    2009-12-01

    We investigate theoretically the spin-dependent electron transport in a straight waveguide with Rashba spin-orbit coupling (SOC) under the irradiation of a transversely polarized electromagnetic (EM) field. Spin-dependent electron conductance and spin polarization are calculated as functions of the emitting energy of electrons or the strength of the EM field by adopting the mode matching approach. It is shown that the spin polarization can be manipulated by external parameters when the strength of Rashba SOC is strong. Furthermore, a sharp step structure is found to exist in the total electron conductance. These results can be understood by the nontrivial Rashba subbands intermixing and the electron intersubband transition when a finite-range transversely polarized EM field irradiates a straight waveguide.

  17. Investigation on the electrical transport properties of highly (00l)-textured Sb2Te3 films deposited by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Zhang, Xiangpeng; Zeng, Zhigang; Shen, Chao; Zhang, Ziqiang; Wang, Zhichong; Lin, Cong; Hu, Zhiyu

    2014-01-01

    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 cm2/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 ṡcm/K.

  18. In-plane Thermal and Electrical Transport Through Single-walled Carbon Nanotube Thin Films

    NASA Astrophysics Data System (ADS)

    Ferguson, A. J.; Avery, A. D.; Mistry, K. S.; Zink, B. L.; Olsen, M. L.; Parilla, P. A.; Blackburn, J. L.

    2014-03-01

    Recent advances in both chemical processing and fabrication techniques have enabled the development of a variety of new nanostructured materials for energy conversion technologies. Single-walled carbon nanotube (SWNT) networks may enable a number of cost-effective energy technologies, including transparent conductors for photovoltaics and thermoelectric composites. For such applications, a fundamental understanding of the physics governing their thermal and electrical properties is needed. Transport in SWNT networks is highly anisotropic; therefore the ability to measure the in-plane transport, both thermal and electrical, for these systems is extremely important. In this talk, we discuss the dispersion of highly enriched semiconducting SWNTs in organic solvents and deposition techniques optimized to enable measurements of in-plane transport of uniform thin films. We present results from in-plane thermal and electrical measurements as well as optical properties of SWNT:polymer thin films. Finally, we discuss the application of these results to developing nanocomposite films optimized for thermoelectric applications.

  19. 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.

  20. 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.

  1. Electrical Transport in Thin Film Systems for Energy Harvesting

    NASA Astrophysics Data System (ADS)

    Huang, Bingyuan

    Many energy conversion technologies rely on the function and properties of thin films. In many cases, the fundamental physics underlying the structure-property-performance interrelationship is not completely understood. So it is not possible to fully exploit the true capabilities of these systems. Therefore, investigating and understanding such interrelationships in different systems is of both scientific and technological importance. In this dissertation, both conjugated polymer systems for photovoltaic application and strained silicon system for thermoelectric application are investigated in order to develop a clearer understanding of the effect of film thickness and microstructural features on electrical transport. Morphological features such as domain size, phase purity are investigated in the polymers in order to understand the effects on charge mobility, recombination and further on device performance. With regard to silicon, the effects of lattice strain on electrical conductivity and thermopower are studied. The out-of-plane hole mobility was investigated in regioregular P3HT thin films. It was shown that the hole mobilities monotonically increased an order of magnitude when film thickness increased from 80 nm to 700 nm. Based on X-ray diffraction, spectroscopic ellipsometry and simulations, this thickness-dependent mobility is associated with substrate induced anisotropies of the P3HT film structure. The role of microstructural features on the performance characteristics of the archetypal P3HT:PCBM (1:1) bulk heterojunction solar cell was investigated. It is demonstrated that small domain sizes and correspondingly large interfacial areas accommodated a high initial carrier density. However in these materials, non-geminate recombination of carriers could be significant, leading to low open circuit voltages and low fill factors. The purity of the domains also influenced the charge carrier mobilities and non-germinate recombination. One important finding from

  2. Effect of Doping with Substituent Bi Atoms on the Electrical Transport Properties of a Bi0.4Sb1.6Te3 Film Fabricated by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Wang, Zhichong; Zhang, Xiangpeng; Wu, Yigui; Hu, Zhiyu

    2015-10-01

    A highly crystalline Bi0.4Sb1.6Te3 film was fabricated on a Si substrate by molecular beam epitaxy (MBE) at a substrate temperature of 280°C. On the basis of study of x-ray diffraction patterns and high-resolution transmission electron microscopy lattice fringes it was inferred that Bi atoms were successfully incorporated into Sb lattice sites, forming substituent Bi impurities. Reduction of the carrier concentration was ascribed to the increased resistance to formation of antisite defects when Sb was substituted by Bi. The reduced mobility was a result of enhanced grain boundary scattering and attraction by substituent Bi atoms. Analysis of temperature-dependent electrical transport properties revealed that introduction of Bi atoms resulted in deeper energy level impurities in the Bi0.4Sb1.6Te3 film and higher activation energy (43.2 meV) than the normal value at room temperature, leading to semiconductor characteristics of the film in the temperature range -50°C to 150°C.

  3. Electrical transport and thermoelectric properties of Ni-doped perovskite-type YCo1-x NixO3 (0 <= x <= 0.07) prepared by sol-gel process

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Li, Hai-Jin; Zhang, Qing; Li, Yong; Liu, Hou-Tong

    2013-05-01

    Electrical transport and thermoelectric properties of Ni-doped YCo1-xNixO3(0 <= x <= 0.07), prepared by using the sol-gel process, are investigated in a temperature range from 100 to 780 K. The results show that with the increase of Ni doping content, the values of DC resistivity of YCo1-xNixO3 decrease, but carrier concentration increases. The temperature dependences of the resistivity for YCo1-xNixO3 are found to follow a relation of ln ρ ∝ 1/T in a low-temperature range (LTR) (T < ~ 304 K for x = 0; ~ 230 K < T < ~ 500 K for x = 0.02, 0.05, and 0.07) and high-temperature range (HTR) (T > ~ 655 K for all compounds), respectively. The estimated apparent activation energies for conduction Ea1 in LRT and Ea2 in HTR are both found to decrease monotonically with doping content increasing. At very low temperatures (T < ~230 K), Mott's law is observed for YCo1—xNixO3 (x >= 0.02), indicating that considerable localized states form in the heavy doping compounds. Although the Seebeck coefficient of the compound decreases after Ni doping, the power factor of YCo1-xNixO3 is enhanced remarkably in a temperature range from 300 to 740 K, i.e., a 6-fold increase is achieved at 500 K for YCo0.98Ni0.02O3, indicating that the high-temperature thermoelectric property of YCoO3 can be improved by partial substitution of Ni for Co.

  4. 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.

  5. Intercomponent momentum transport and electrical conductivity of collisionless plasma

    NASA Technical Reports Server (NTRS)

    Wilhelm, H. E.

    1973-01-01

    Based on the Lenard-Balescu equation, the interaction integral for the intercomponent momentum transfer in a two-component, collisionless plasma is evaluated in closed form. The distribution functions of the electrons and ions are represented in the form of nonisothermal, displaced Maxwellians corresponding to the 5-moment approximation. As an application, the transport of electrical current in an electric field is discussed for infrasonic up to sonic electron-ion drift velocities.

  6. 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.

  7. 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

  8. On the tuning of electrical and thermal transport in thermoelectrics: an integrated theory-experiment perspective

    NASA Astrophysics Data System (ADS)

    Yang, Jiong; Xi, Lili; Qiu, Wujie; Wu, Lihua; Shi, Xun; Chen, Lidong; Yang, Jihui; Zhang, Wenqing; Uher, Ctirad; Singh, David J.

    2016-02-01

    During the last two decades, we have witnessed great progress in research on thermoelectrics. There are two primary focuses. One is the fundamental understanding of electrical and thermal transport, enabled by the interplay of theory and experiment; the other is the substantial enhancement of the performance of various thermoelectric materials, through synergistic optimisation of those intercorrelated transport parameters. Here we review some of the successful strategies for tuning electrical and thermal transport. For electrical transport, we start from the classical but still very active strategy of tuning band degeneracy (or band convergence), then discuss the engineering of carrier scattering, and finally address the concept of conduction channels and conductive networks that emerge in complex thermoelectric materials. For thermal transport, we summarise the approaches for studying thermal transport based on phonon-phonon interactions valid for conventional solids, as well as some quantitative efforts for nanostructures. We also discuss the thermal transport in complex materials with chemical-bond hierarchy, in which a portion of the atoms (or subunits) are weakly bonded to the rest of the structure, leading to an intrinsic manifestation of part-crystalline part-liquid state at elevated temperatures. In this review, we provide a summary of achievements made in recent studies of thermoelectric transport properties, and demonstrate how they have led to improvements in thermoelectric performance by the integration of modern theory and experiment, and point out some challenges and possible directions.

  9. 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.

  10. Enhanced electrical properties of vertically aligned carbon nanotube-epoxy nanocomposites with high packing density

    PubMed Central

    2012-01-01

    During their synthesis, multi-walled carbon nanotubes can be aligned and impregnated in a polymer matrix to form an electrically conductive and flexible nanocomposite with high backing density. The material exhibits the highest reported electrical conductivity of CNT-epoxy composites (350 S/m). Here, we show how conductive atomic force microscopy can be used to study the electrical transport mechanism in order to explain the enhanced electrical properties of the composite. The high spatial resolution and versatility of the technique allows us to further decouple the two main contributions to the electrical transport: (1) the intrinsic resistance of the tube and (2) the tunneling resistance due to nanoscale gaps occurring between the epoxy-coated tubes along the composite. The results show that the material behaves as a conductive polymer, and the electrical transport is governed by electron tunneling at interconnecting CNT-polymer junctions. We also point out the theoretical formulation of the nanoscale electrical transport between the AFM tip and the sample in order to derive both the composite conductivity and the CNT intrinsic properties. The enhanced electrical properties of the composite are attributed to high degree of alignment, the CNT purity, and the large tube diameter which lead to low junction resistance. By controlling the tube diameter and using other polymers, the nanocomposite electrical conductivity can be improved. PMID:23158381

  11. 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.

  12. 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

  13. [Measuring the electricity frequency properties of blood].

    PubMed

    Huang, Hua; Hu, Maoqing; Chen, Huaiqing; Yuan, Zirun; Tong, Shan; Luo, An

    2005-04-01

    In order to understand the electricity frequency specialties of blood, we have developed a wide frequency electricity characteristic testing system and used it to test the amplitude frequency property and phase frequency property of the blood in different states and constituents at 1 Hz to 20 MHz. Further analysis on the results of tests helped us know some important properties of blood at even more microcosmic levels from a new angle. Meanwhile, some problems and considerations on the improvement of the electricity model of biotic tissue and blood were pointed out. (1) From 1 Hz to 5 KHz, the impedance of blood descended 99%. (2) Simple equivalent circuit of resistance and capacitance must be used in series equivalent but not in usual parallel connection equivalent. (3) Experiment indicated, equivalent circuits of blood need more analysis, because simple equivalent circuit of resistance and capacitance is liable to gross error. (4) When the three element model is used for measuring the resistance of inside liquid, capacitance of cell membrane and the resistance of outside liquid of blood, the three testing frequencies must be very similar.

  14. Quantum-walk transport properties on graphene structures

    NASA Astrophysics Data System (ADS)

    Bougroura, Hamza; Aissaoui, Habib; Chancellor, Nicholas; Kendon, Viv

    2016-12-01

    We present numerical studies of quantum walks on C60 and related graphene structures to investigate their transport properties. Also known as a honeycomb lattice, the lattice formed by carbon atoms in the graphene phase can be rolled up to form nanotubes of various dimensions. Graphene nanotubes have many important applications, some of which rely on their unusual electrical conductivity and related properties. Quantum walks on graphs provide an abstract setting in which to study such transport properties independent of the other chemical and physical properties of a physical substance. They can thus be used to further the understanding of mechanisms behind such properties. We find that nanotube structures are significantly more efficient in transporting a quantum walk than cycles of equivalent size, provided the symmetry of the structure is respected in how they are used. We find faster transport on zigzag nanotubes compared to armchair nanotubes, which is unexpected given that for the actual materials the armchair nanotube is metallic, while the zigzag is semiconducting.

  15. 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.

  16. Growth and electrical properties of zinc oxide nanowires.

    PubMed

    Zhang, Zengxing; Zhao, Yuanchun; Sun, Lianfeng; Liu, Dongfang; Shen, Jun; Zhou, Weiya; Luo, Qiang; Jin, Aizi; Yang, Haifang; Gu, Changzhi; Xie, Sishen

    2009-02-01

    Zinc oxide nanowires were grown on molybdenum grids with a simple chemical vapor transport and deposition method through thermal evaporation of zinc powder at a temperature of 600 degrees C. These nanowires are 20-50 nm in diameter and over ten microns in length. High resolution transmission electron microscopy studies show that the as-grown nanowires are single crystal of wurtzite structure and grow along the (0001) direction. The growth process was explained with a vapor-solid mechanism under zinc-rich conditions. We further patterned electrodes on individual ZnO nanowires by e-beam lithography and studied thier electrical properties.

  17. Transport properties of multicomponent thermal plasmas: Grad method versus Chapman-Enskog method

    SciTech Connect

    Porytsky, P.; Krivtsun, I.; Demchenko, V.; Reisgen, U.; Mokrov, O.; Zabirov, A.; Gorchakov, S.; Timofeev, A.; Uhrlandt, D.

    2013-02-15

    Transport properties (thermal conductivity, viscosity, and electrical conductivity) for multicomponent Ar-Fe thermal plasmas at atmospheric pressure have been determined by means of two different methods. The transport coefficients set based on Grad's method is compared with the data obtained when using the Chapman-Enskog's method. Results from both applied methods are in good agreement. It is shown that the Grad method is suitable for the determination of transport properties of the thermal plasmas.

  18. Temperature effects on electrical transport in semiconducting nanoporous carbon nanowires

    NASA Astrophysics Data System (ADS)

    Samuel, B. A.; Rajagopalan, R.; Foley, H. C.; Haque, M. A.

    2008-07-01

    In this paper we report on the effect of temperature on the electrical conductivity of amorphous and nanoporous (pores size around 0.5 nm) carbon nanowires. Poly(furfuryl alcohol) nanowires with diameter varying from 150 to 250 nm were synthesized by a template-based technique and upon pyrolysis yielded amorphous carbon nanowires with nanosized pores in them. We observed significant (as high as 700%) decrease in electrical resistance when the nanowire surface temperature was increased from room temperature to 160 °C. On the basis of the experimental and microscopy evidence, we infer a thermally activated carrier transport mechanism to be the primary electrical transport mechanism, at elevated temperatures, in these semiconducting, amorphous, and nanoporous carbon nanowires.

  19. 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.

  20. 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.

  1. 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.

  2. Electrical and thermal transport measurements on nano-structured materials

    NASA Astrophysics Data System (ADS)

    Chang, Chih-Wei

    This thesis discusses electrical and thermal transport measurements on C60, carbon nanotubes, and boron-nitride nanotubes. Chapter 1 describes the anomalous resistivity behavior of Ag films on C60 crystals. The correlation of the resistivity anomaly and the structural phase transition is established. Chapter 2 gives an introduction to the physical properties and the synthesis methods of carbon and boron nitride nanotubes. Chapter 3 shows two different approaches on chemical functionalization of boron-nitride nanotubes. Chapter 4 gives the theoretical background of thermal conductivity, especially for nano-structured materials. A summary of theoretical and experimental works on the thermal conductivity of nanotubes is given. Chapter 5 discusses the experimental results of thermal conductivity of nanotube mats. An absolute value of the thermal conductivity of boron nitride nanotubes is bracketed and can be compared to the results of the following chapters on individual nanotubes. Chapter 6 describes the experimental methods of measuring thermal conductivity of individual nanotubes. Chapter 7 shows the 2 temperature dependent thermal conductivity and thermopower of individual nanotubes. Chapter 8 discusses the isotope effect and the diameter dependence of the thermal conductivity of nanotubes. In chapter 9, it is shown that the thermal conductivity of nanotubes is robust against electron irradiation and structural deformation. Importantly, the observation challenges current understandings on the thermal transport of nano-structured materials. In chapter 10, it is shown that it is possible to reversibly tune the thermal conductivity of a multiwalled nanotube by controllably sliding the outer-shells against inner cores. Chapter 11 describes a thermal rectifier by engineering the mass distribution along a nanotube. The observed non-zero thermal rectification effect provides strong evidence for solitons in nanotubes. The soliton model also coherently explains many

  3. Electrical, optical and dielectric properties of HCl doped polyaniline nanorods

    NASA Astrophysics Data System (ADS)

    Chutia, P.; Kumar, A.

    2014-03-01

    In this report we have investigated the optical, electrical and dielectric properties of HCl doped polyaniline nanorods synthesized by the interfacial polymerization technique. High resolution transmission electron microscope (HRTEM) micrographs confirm the formation of nanorods. X-ray diffraction pattern shows the semicrystalline nature of polyaniline nanorods with a diameter distribution in the range of 10-22 nm. The chemical and electronic structures of the polyaniline nanorods are investigated by micro-Raman and UV-vis spectroscopy. Dielectric relaxation spectroscopy has been applied to study the dielectric permittivity, modulus formalism and ac conductivity as a function of frequency and temperature. The ac conductivity follows a power law with frequency. The variation of frequency exponent with temperature suggests that the correlated barrier hopping is the dominant charge transport mechanism. The existence of both polaron and bipolaron in the transport mechanism has been confirmed from the binding energy calculations.

  4. 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.

  5. 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

  6. 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).

  7. Operation regimes and electrical transport of steep slope Schottky Si-FinFETs

    NASA Astrophysics Data System (ADS)

    Jeon, Dae-Young; Zhang, Jian; Trommer, Jens; Park, So Jeong; Gaillardon, Pierre-Emmanuel; De Micheli, Giovanni; Mikolajick, Thomas; Weber, Walter M.

    2017-02-01

    In the quest for energy efficient circuits, considerable focus has been given to steep slope and polarity-controllable devices, targeting low supply voltages and reduction of transistor count. The recently proposed concept of the three-independent gated Si-FinFETs with Schottky-barriers (SBs) has proven to bring both functionalities even in a single device. However, the complex combination of transport properties including Schottky emission and weak impact ionization as well as the body effect makes the design of such devices challenging. In this work, we perform a deep electrical characterization analysis to visualize and decouple the different operation regimes and electrical properties of the SB Si-FinFETs using a graphical transport map. From these, we give important guidelines for the design of future devices.

  8. 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.

  9. Quantifying solute transport processes: are chemically "conservative" tracers electrically conservative?

    USGS Publications Warehouse

    Singha, Kamini; Li, Li; Day-Lewis, Frederick D.; Regberg, Aaron B.

    2012-01-01

    The concept of a nonreactive or conservative tracer, commonly invoked in investigations of solute transport, requires additional study in the context of electrical geophysical monitoring. Tracers that are commonly considered conservative may undergo reactive processes, such as ion exchange, thus changing the aqueous composition of the system. As a result, the measured electrical conductivity may reflect not only solute transport but also reactive processes. We have evaluated the impacts of ion exchange reactions, rate-limited mass transfer, and surface conduction on quantifying tracer mass, mean arrival time, and temporal variance in laboratory-scale column experiments. Numerical examples showed that (1) ion exchange can lead to resistivity-estimated tracer mass, velocity, and dispersivity that may be inaccurate; (2) mass transfer leads to an overestimate in the mobile tracer mass and an underestimate in velocity when using electrical methods; and (3) surface conductance does not notably affect estimated moments when high-concentration tracers are used, although this phenomenon may be important at low concentrations or in sediments with high and/or spatially variable cation-exchange capacity. In all cases, colocated groundwater concentration measurements are of high importance for interpreting geophysical data with respect to the controlling transport processes of interest.

  10. Physical and Optical Polarizability and Transport Properties of Bismuthate Glasses

    NASA Astrophysics Data System (ADS)

    Bale, Shashidhar; Rahman, Syed

    Bismuth-based glasses containing ZnO, B2O3 and Li2O are investigated through different physical, polarizability and transport properties. Raman spectroscopy reveals that these glasses are built from [BiO3] and [BiO6] units. Zinc in tetrahedral form is also observed. Density and glass transition temperature increase with the bismuth content. The refractive index, oxide ion polarizability and optical basicity also increase with the Bi2O3 content, whereas the interaction parameter decreases. The DC electrical conductivity increases and the activation energy decreases with the increase in the Li2O content.

  11. Electrical properties and magnetic response of cobalt germanosilicide nanowires.

    PubMed

    Tsai, Chun-I; Wang, Chiu-Yen; Tang, Jianshi; Hung, Min-Hsiu; Wang, Kang L; Chen, Lih-Juann

    2011-12-27

    The effects of partial substitution of Ge for Si in cobalt germanosilicide (CoSi(1-x)Ge(x) and Co(2)Si(1-x)Ge(x)) nanowires (NWs) on the electrical transport, magnetic properties, and magnetoresistance (MR) have been investigated. Cobalt germanosilicide NWs were synthesized by a spontaneous chemical vapor transport growth method. The Ge concentration can be selectively controlled from 0 to 15% and 0-50% for CoSi(1-x)Ge(x) and Co(2)Si(1-x)Ge(x) NWs, respectively, by varying the reaction temperature. Electrical measurements showed that the resistivities of CoSi(1-x)Ge(x) NWs are 90, 60, 30, and 23 μΩ-cm for x = 0, 0.01, 0.05, and 0.15, respectively. Therefore, the electrical resistivity of CoSi(1-x)Ge(x) NWs was found to decrease significantly with an increasing Ge concentration, which is believed to be a result of the band gap narrowing. On the other hand, the Co(2)Si(1-x)Ge(x) (x ≤ 0.5) NWs exhibited ferromagnetism at 300 K, which is attributed to the uncoordinated Co atoms on the NW surface and spin-glass behavior at low temperature. The highest MR response of Co(2)Si(1-x)Ge(x) NWs occurred at x = 0.5, where a MR ratio of 11.7% can be obtained at 10-25 K with a magnetic field of 8 T. The enhanced physical properties of cobalt germanosilicide NWs with Ge substitution shall lead to promising application in the fabrication of nanodevices, including spintronics and serving as the gate and interconnect material.

  12. Electrical transport along bacterial nanowires from Shewanella oneidensis MR-1

    PubMed Central

    El-Naggar, Mohamed Y.; Wanger, Greg; Leung, Kar Man; Yuzvinsky, Thomas D.; Southam, Gordon; Yang, Jun; Lau, Woon Ming; Nealson, Kenneth H.; Gorby, Yuri A.

    2010-01-01

    Bacterial nanowires are extracellular appendages that have been suggested as pathways for electron transport in phylogenetically diverse microorganisms, including dissimilatory metal-reducing bacteria and photosynthetic cyanobacteria. However, there has been no evidence presented to demonstrate electron transport along the length of bacterial nanowires. Here we report electron transport measurements along individually addressed bacterial nanowires derived from electron-acceptor–limited cultures of the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1. Transport along the bacterial nanowires was independently evaluated by two techniques: (i) nanofabricated electrodes patterned on top of individual nanowires, and (ii) conducting probe atomic force microscopy at various points along a single nanowire bridging a metallic electrode and the conductive atomic force microscopy tip. The S. oneidensis MR-1 nanowires were found to be electrically conductive along micrometer-length scales with electron transport rates up to 109/s at 100 mV of applied bias and a measured resistivity on the order of 1 Ω·cm. Mutants deficient in genes for c-type decaheme cytochromes MtrC and OmcA produce appendages that are morphologically consistent with bacterial nanowires, but were found to be nonconductive. The measurements reported here allow for bacterial nanowires to serve as a viable microbial strategy for extracellular electron transport. PMID:20937892

  13. Dynamical properties of transportation on complex networks

    NASA Astrophysics Data System (ADS)

    Shen, Bo; Gao, Zi-You

    2008-02-01

    We study the dynamical properties of transportation considering the topology structure of networks and congestion effects, based on a proposed simple model. We analyze the behavior of the model for finding out the relationship between the properties of transportation and the structure of network. Analysis and numerical results demonstrate that the transition from free flow to congested regime can be observed for both single link load and network load, but it is discontinuous for single link and continuous for network. We also find that networks with large average degree have small average link betweenness and are more tolerant to congestion, and networks with homogeneous structure can hold more vehicles in stationary state at the subcritical region. Furthermore, by allotting capacity with different mode to links, a manner of enhancing the performance of networks is introduced, which should be helpful in the design of traffic networks.

  14. Diffusive Transport Properties Across Coupling Regimes

    NASA Astrophysics Data System (ADS)

    Dharuman, G.; Murillo, M. S.; Verboncoeur, J.; Christlieb, A.

    2014-10-01

    Transport properties are poorly known across coupling regimes, therefore understanding them is of importance for theoretical and practical reasons. A useful tool is an ultracold plasma system because of the experimental capability to tune the system to attain Coulomb coupling Γ ranging from 0.1 to 1 to 10 with the screening parameter κ ranging from 0 to 4 to 8, spanning the regions of the phase diagram from weak to moderate to strongly coupled and screened systems. Strong coupling is possible if Disorder Induced Heating is mitigated which requires a correlated initial ion state. Of particular interest is Rydberg blockaded gas of ultracold atoms where the local blockade effect results in correlations. Predictions of higher coupling in ultracold plasma created from a Rydberg blockaded gas have been reported. In this work we examine the diffusive transport properties of ultracold plasma system using molecular dynamics simulations for experimentally realizable values of Γ and κ as discussed above.

  15. 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.

  16. Effect of graphene-oxide on the microstructure and charge carrier transport of polyaniline nanocomposites under low applied electric fields

    NASA Astrophysics Data System (ADS)

    Mombrú, Dominique; Romero, Mariano; Faccio, Ricardo; Mombrú, Álvaro W.

    2017-01-01

    We report a study on the preparation and characterization of polyaniline-graphene oxide (PANI-GO-X) nanocomposites focusing in the study of its structure, microstructure, and correlations with electrical transport properties under low applied electric fields. X-ray diffraction analysis showed evidence of graphene oxide (GO) blending between polyaniline fibers, and according to small angle X-ray scattering, the fractal dimensionality was quasi-one dimensional for all nanocomposites. Confocal Raman spectroscopy revealed that the addition of GO leads to a notorious decrease of the polaron population of polyaniline. A significant increase in resistivity was observed for PANI-GO-X nanocomposites with respect to pure polyaniline, in agreement with the decrease in the polaron population. The electrical transport mechanism could be explained by an Arrhenius behavior at high temperatures (T > 255 K) and a broad transition with a logarithmic dependence of the activation energy with temperature for the low temperature regime (T < 255 K). Additionally, an increase in the hopping transport dimensionality from quasi-1D to quasi-3D was observed for X = 7% GO nanocomposites. The transport properties, studied after the polarization using low applied electric fields, revealed the modification of the electrical transport at low temperatures. In addition, the electrical transport of PANI-GO-X nanocomposites followed a typical ln(σ) vs E1/2 Poole-Frenkel type dependence in the presence of low applied electric fields. At low temperatures, X = 7% GO nanocomposites showed a notorious increase in the Poole-Frenkel slope at low applied electric fields with respect to pure polyaniline. The enhancement on the electric response using low applied electric fields (E ˜ 2 V/cm) could be of great interest for the development of new organic electronic devices.

  17. Stability properties of elementary dynamic models of membrane transport.

    PubMed

    Hernández, Julio A

    2003-01-01

    Living cells are characterized by their capacity to maintain a stable steady state. For instance, cells are able to conserve their volume, internal ionic composition and electrical potential difference across the plasma membrane within values compatible with the overall cell functions. The dynamics of these cellular variables is described by complex integrated models of membrane transport. Some clues for the understanding of the processes involved in global cellular homeostasis may be obtained by the study of the local stability properties of some partial cellular processes. As an example of this approach, I perform, in this study, the neighborhood stability analysis of some elementary integrated models of membrane transport. In essence, the models describe the rate of change of the intracellular concentration of a ligand subject to active and passive transport across the plasma membrane of an ideal cell. The ligand can be ionic or nonionic, and it can affect the cell volume or the plasma membrane potential. The fundamental finding of this study is that, within the physiological range, the steady states are asymptotically stable. This basic property is a necessary consequence of the general forms of the expressions employed to describe the active and passive fluxes of the transported ligand.

  18. Spatially resolved imaging of opto-electrical property variations

    DOEpatents

    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.

  19. 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.

  20. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Grain Size Effect on Electrical Conductivity and Giant Magnetoresistance of Bulk Magnetic Polycrystals

    NASA Astrophysics Data System (ADS)

    Luo, Wei; Zhu, Lin-Li; Zheng, Xiao-Jing

    2009-11-01

    By solving the Boltzmann transport equation and considering the spin-dependent grain boundary scattering, the distribution of electrons in grains and the electrical transport properties in the applied magnetic field are studied. With regard to the dominant influence of grain boundary scattering which is taken as a boundary condition for the electrical transport, the grain size-dependent electrical conductivity is investigated. In addition, the reorientation of the relative magnetization between grains brings the change of the electron spin when the magnetonanocrystalline material is subjected to the magnetic field, resulting in the remarkable giant magnetoresistance effect.

  1. Transport properties of polymer solutions. A comparative approach.

    PubMed Central

    Foster, K R; Cheever, E; Leonard, J B; Blum, F D

    1984-01-01

    A variety of transport properties have been measured for solutions of the water soluble polymer poly(ethylene oxide)(PEO) with molecular weights ranging from 200 to 14,000, and volume fractions ranging from 0-80%. The transport properties are thermal conductivity, electrical conductivity at audio frequencies (in solutions containing dilute electrolyte), and water self-diffusion. These data, together with dielectric relaxation data previously reported, are amenable to analysis by the same mixture theory. The ionic conductivity and water self-diffusion coefficient, but not the thermal conductivity, are substantially smaller than predicted by the Maxwell and Hanai mixture relations, calculated using the known transport properties of pure liquid water. A 25% (by volume) solution of PEO exhibits an average dielectric relaxation frequency of the suspending water of one half that of pure water, with clear evidence of a distribution of relaxation times present. The limits of the cumulative distribution of dielectric relaxation times that are consistent with the data are obtained using a linear programming technique. The application of simple mixture theory, under appropriate limiting conditions, yields hydration values for the more dilute polymer solutions that are somewhat larger than values obtained from thermodynamic measurements. PMID:6733244

  2. Connection between elastic and electrical properties of cortical bone.

    PubMed

    Gao, X; Sevostianov, I

    2016-03-21

    The paper focuses on the connection between elastic and electrical properties of cortical bone. Both these properties are governed by microstructure that consists of several pore systems filled with mechanically soft and electrically conductive tissue. Microstructural changes induced by aging, various diseases, microgravity conditions etc. lead to variation in both properties. The paper address the problem of evaluation of the changes in mechanical performance (decrease in Young׳s moduli) via monitoring electrical conductivity. The theoretical results are verified experimentally.

  3. 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.

  4. Predicting the transport properties of sedimentary rocks from microstructure

    SciTech Connect

    Schlueter, Erika 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.

  5. Transport properties in semiconductor-gas discharge electronic devices

    NASA Astrophysics Data System (ADS)

    Sadiq, Y.; (Yücel) Kurt, H.; Albarzanji, A. O.; Alekperov, S. D.; Salamov, B. G.

    2009-09-01

    Nonlinear electrical transport of semi-insulating (SI) GaAs detector in semiconductor-gas discharge IR image converter (SGDIC) are studied experimentally for a wide range of the gas pressures ( p = 28-55 Torr), interelectrode distances ( d = 445-525 μm) and inner electrode diameters ( D = 12-22 mm) of photocathode. The destabilization of homogeneous state observed in a planar dc-driven structure is due to nonlinear transport properties of GaAs photocathode. Experimental investigation of electrical instability in SGDIC structure was analyzed using hysteresis, N-shaped negative differential conductivity (NDC) current voltage characteristics (CVC) and dynamic behavior of current in a wide range of feeding voltage ( U = 590-1000 V) under different IR light intensities incident on cathode material. It is established that hysteresis are related to electron capture and emission from EL2 deep center on the detector substrate. We have experimentally investigated domain velocity and electron mobility based on well-understood transferred electron effect (TEE) for abovementioned nonlinear electrical characteristics of SI GaAs. The experimental findings are in good agreement with estimated results reported by other independent authors.

  6. Transport Properties of Negative Ions in HBR Plasmas

    NASA Astrophysics Data System (ADS)

    Stojanovic, Vladimir; Ivanovic, Nenad; Radmilovic-Radjenovic, Marija; Raspopovic, Zoran; Bojarov, Aleksandar; Petrovic, Zoran

    2014-10-01

    Low temperature plasma in halogenated gases is standard environment for dry etching of semiconductors. Amount of negative ions in HBr plasmas determines electronegativity so modeling etching devices requires data for anion transport properties. In this work we present cross section set for Br- ions in HBr assembled by using Denpoh-Nanbu theory. The threshold energy values were calculated by known heats of formation. The calculated total cross section accounts for ion-induced-dipole and ion-permanent-dipole interaction by using the local-dipole model. The total cross section was corrected to fit the reduced mobility obtained by SACM (Statistical Adiabatic Channel Model) approximation. Existing cross section measurements were used to scale calculated cross sections. Finally, we used Monte Carlo method to determine transport parameters for Br- as a function of reduced electric fields that can be used in fluid and hybrid plasma models.

  7. 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.

  8. The phase diagram and transport properties for hydrogen-helium fluid planets

    NASA Technical Reports Server (NTRS)

    Stevenson, D. J.; Salpeter, E. E.

    1977-01-01

    The properties of pure hydrogen and helium are examined, taking into account metallic hydrogen, molecular hydrogen, and the molecular-metallic transition. Metallic hydrogen-helium mixtures are considered along with molecular hydrogen-helium mixtures, the total phase diagram, and minor constituents, including deuterium. The transport properties of the metallic and the molecular phase are also discussed, giving attention to electrical conductivity, thermal conductivity, viscosity, self-diffusion, interdiffusion, radiative opacity, and second-order transport coefficients.

  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. Measurement of Transport Properties of Aerosolized Nanomaterials

    PubMed Central

    Ku, Bon Ki; Kulkarni, Pramod

    2015-01-01

    Airborne engineered nanomaterials such as single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), functionalized MWCNT, graphene, fullerene, silver and gold nanorods were characterized using a tandem system of a differential mobility analyzer and an aerosol particle mass analyzer to obtain their airborne transport properties and understand their relationship to morphological characteristics. These nanomaterials were aerosolized using different generation methods such as electrospray, pneumatic atomization, and dry aerosolization techniques, and their airborne transport properties such as mobility and aerodynamic diameters, mass scaling exponent, dynamic shape factor, and effective density were obtained. Laboratory experiments were conducted to directly measure mobility diameter and mass of the airborne nanomaterials using tandem mobility-mass measurements. Mass scaling exponents, aerodynamic diameters, dynamic shape factors and effective densities of mobility-classified particles were obtained from particle mass and the mobility diameter. Microscopy analysis using Transmission Electron Microscopy (TEM) was performed to obtain morphological descriptors such as envelop diameter, open area, aspect ratio, and projected area diameter. The morphological information from the TEM was compared with measured aerodynamic and mobility diameters of the particles. The results showed that aerodynamic diameter is smaller than mobility diameter below 500 nm by a factor of 2 to 4 for all nanomaterials except silver and gold nanorods. Morphologies of MWCNTs generated by liquid-based method, such as pneumatic atomization, are more compact than those of dry dispersed MWCNTs, indicating that the morphology depends on particle generation method. TEM analysis showed that projected area diameter of MWCNTs appears to be in reasonable agreement with mobility diameter in the size range from 100 – 400 nm. Principal component analysis of the obtained airborne particle

  11. Silicon multi-branch nanostructures for decent field emission and excellent electrical transport

    NASA Astrophysics Data System (ADS)

    Sun, Min; Gao, Yihua; Zhi, Chunyi; Bando, Yoshio; Golberg, Dmitri

    2011-04-01

    We report on the synthesis, field electron emission and electric transport properties of a novel nanomaterial: ordered arrays of crystallized silicon multi-branch nanostructures. A decent field electron emission with relatively low turn-on field of 3.16 V µm - 1 and high field-enhancement factor of 1252 was received for the silicon nanobranches. The relevancies between field-emission current-voltage characteristic, turn-on field, threshold field and sample-anode distance have been thoroughly analyzed. In addition, electrical transport measurements revealed a small electrical resistance of 0.51 MΩ for as-prepared silicon nanobranches. In contrast, by improving the silicon nanobranch-electrode contact, vacuum annealing dramatically reduced the electrical resistance, by a factor approaching two, while thermal oxidation resulted in a much higher resistance due to the amorphous oxide coating of the silicon nanobranches, both of the current versus voltage curves became more linear and symmetrical, and the transport stability was obviously improved.

  12. 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.

  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. First-principles study of the electrical and lattice thermal transport in monolayer and bilayer graphene

    NASA Astrophysics Data System (ADS)

    D'Souza, Ransell; Mukherjee, Sugata

    2017-02-01

    We report the transport properties of monolayer and bilayer graphene from first-principles calculations and Boltzmann transport theory (BTE). Our resistivity studies on monolayer graphene show Bloch-Grüneisen behavior in a certain range of chemical potentials. By substituting boron nitride in place of a carbon dimer of graphene, we predict a twofold increase in the Seebeck coefficient. A similar increase in the Seebeck coefficient for bilayer graphene under the influence of a small electric field ˜0.3 eV has been observed in our calculations. Graphene with impurities shows a systematic decrease of electrical conductivity and mobility. We have also calculated the lattice thermal conductivities of monolayer graphene and bilayer graphene using phonon BTE which show excellent agreement with experimental data available in the temperature range 300-700 K.

  15. High pressure electrical transport behavior in organic semiconductor pentacene

    NASA Astrophysics Data System (ADS)

    Wang, Qinglin; Zhang, Haiwa; Zhang, Yan; Liu, Cailong; Han, Yonghao; Ma, Yanzhang; Gao, Chunxiao

    2014-10-01

    The high pressure electrical transport behavior of pentacene has been investigated by alternating current impedance techniques and direct current resistivity measurement in a diamond anvil cell (DAC). The resistance decreases with increasing pressure below 17.4 GPa, while it increases above 17.4 GPa, which is caused by the transition of pentacene from an ordered state to the disordered state under higher pressure. From the Raman spectra under various pressures, pentacene becomes amorphous above 17.3 GPa, which is consistent with the impedance results. The charge transport operates in the hopping regime with charges jumping between interacting molecules, and the hopping mechanisms are related to the vibration modes. Above 17.4 GPa, the pressure dependence of the relaxation activation energy is 21.7 meV/GPa and pentacene keeps semiconductor characteristics up to 28.3 GPa.

  16. Transport and magnetic properties of CMR manganites with antidot arrays

    NASA Astrophysics Data System (ADS)

    Zhang, Kai; Du, Kai; Niu, Jiebin; Wei, Wengang; Chen, Jinjie; Yin, Lifeng; Shen, Jian

    2014-03-01

    We fabricated and characterized a series of manganites thin film samples with different densities of antidots. With increasing antidot density, the samples show higher MIT temperature and lower resistivity under zero and low magnetic fields. These differences become smaller and finally vanished when the magnetic field is large enough to melt the charge ordered phase in the system, which is expected in our theoretical explanations. We believe that emerging edge states at the ring of antidotes play a significant role for observed metal-insulator transition and electrical transport properties, which are of great importance of real storage and sensor device design. Magnetic property measurements and theoretical simulation also support the conclusion. These results open up new ways to control and tune the strongly correlated oxides without introduce any new material or field.

  17. 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.

  18. Transport properties of multigrained nanocomposites with imperfect interfaces

    NASA Astrophysics Data System (ADS)

    Palla, Pier Luca; Giordano, Stefano

    2016-11-01

    Multigrained or polycrystalline composite materials have attracted a considerable attention due to their potential applications as advanced materials with outstanding thermal, mechanical, and electromagnetic properties. When the grains' morphology is displayed at the nanoscopic scale, the presence of imperfect interfaces plays a central role in determining the effective transport properties. Therefore, we develop here a self-consistent effective medium theory able to evaluate the influence of real contacts between the different phases of multigrained composite materials. This approach takes into account the classical interface schemes that have been introduced in literature, namely, the low and the high conducting interface models. The theoretical results have been compared with numerical and experimental data concerning the thermal conductivity of ( 1 - x ) Si : x Ge mixtures and the electrical conductivity of ( 1 - x ) Li 2 O : x B 2 O 3 composites.

  19. Annealing effects on the structural and electrical transport properties of n-type Bi 2Te 2.7Se 0.3 thin films deposited by flash evaporation

    NASA Astrophysics Data System (ADS)

    Duan, Xingkai; Jiang, Yuezhen

    2010-10-01

    N-type Bi 2Te 2.7Se 0.3 thermoelectric thin films with thickness 800 nm have been deposited on glass substrates by flash evaporation method at 473 K. Annealing effects on the thermoelectric properties of Bi 2Te 2.7Se 0.3 thin films were examined in the temperature range 373-573 K. The structures, morphology and chemical composition of the thin films were characterized by X-ray diffraction, field emission scanning electron microscope and energy dispersive X-ray spectroscopy, respectively. Thermoelectric properties of the thin films have been evaluated by measurements of the electrical resistivity and Seebeck coefficient at 300 K. The Hall coefficients were measured at room temperature by the Van der Pauw method. The carrier concentration and mobility were calculated from the Hall coefficient. The films thickness of the annealed samples was measured by ellipsometer. When annealed at 473 K, the electrical resistivity and Seebeck coefficient are 2.7 mΩ cm and -180 μV/K, respectively. The maximum of thermoelectric power factor is enhanced to 12 μW/cm K 2.

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

    NASA Technical Reports Server (NTRS)

    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.

  1. 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.

  2. Redox-gated electron transport in electrically wired ferrocene molecules

    NASA Astrophysics Data System (ADS)

    Xiao, Xiaoyin; Brune, Daniel; He, Jin; Lindsay, Stuart; Gorman, Christopher B.; Tao, Nongjian

    2006-07-01

    We have synthesized cysteamine-terminated ferrocene molecules and determined the dependence of the electron transport properties of the molecules on their redox states by measuring the current through the molecules as a function of the electrode potential. The current fluctuates over a large range, but its average value increases with the potential. We attribute the current fluctuation and its increase with the potential to the switching of the molecules from low-conductance reduced state to high-conductance oxidized state.

  3. Electrical-stress-induced transport and surface potential characterizations of metal/ TiO 2/metal planar junctions

    NASA Astrophysics Data System (ADS)

    Kim, Haeri; Kim, Dong-Wook

    2011-03-01

    Electric-field-induced resistive switching (RS) phenomena in metal oxides have attracted considerable research interest due to their potential use in nonvolatile memory device applications. Intensive investigations have revealed that coupled electron ion dynamics play a key role the RS mechanism. Metal/single crystal junction can be an ideal model system to study how the ionic drift and diffusion can affect the resistance. We investigated transport and local electrical properties of Pt/ Ti O2 single crystal/Ti planar junctions with micron- sized gaps between the electrodes. Scanning Kelvin probe microscopy (SKPM) showed that negative (positive) electrical stress to the Pt electrodes significantly reduced (hardly affected) the Pt/ Ti O2 contact resistance. The SKPM results also revealed that the electrical stress caused alteration of the local work function of Ti O2 . The comparative investigations of the transport and SKPM results suggested that the electrical stress induced redistribution of ions, resulting in the change of the junction resistance.

  4. Advanced Hall Electric Propulsion for Future In-space Transportation

    NASA Technical Reports Server (NTRS)

    Oleson, Steven R.; Sankovic, John M.

    2001-01-01

    The Hall thruster is an electric propulsion device used for multiple in-space applications including orbit raising, on-orbit maneuvers, and de-orbit functions. These in-space propulsion functions are currently performed by toxic hydrazine monopropellant or hydrazine derivative/nitrogen tetroxide bi-propellant thrusters. The Hall thruster operates nominally in the 1500 sec specific impulse regime. It provides greater thrust to power than conventional gridded ion engines, thus reducing trip times and operational life when compared to that technology in Earth orbit applications. The technology in the far term, by adding a second acceleration stage, has shown promise of providing over 4000s Isp, the regime of the gridded ion engine and necessary for deep space applications. The Hall thruster system consists of three parts, the thruster, the power processor, and the propellant system. The technology is operational and commercially available at the 1.5 kW power level and 5 kW application is underway. NASA is looking toward 10 kW and eventually 50 kW-class engines for ambitious space transportation applications. The former allows launch vehicle step-down for GEO missions and demanding planetary missions such as Europa Lander, while the latter allows quick all-electric propulsion LEO to GEO transfers and non-nuclear transportation human Mars missions.

  5. 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

  6. Experimental analysis of electrical properties of composite materials

    NASA Astrophysics Data System (ADS)

    Fiala, L.; Rovnaník, P.; Černý, R.

    2017-02-01

    Dry cement-based composites are electrically non-conductive materials that behave in electric field like dielectrics. However, a relatively low amount of electrically conductive admixture significantly increases the electrical conductivity which extends applicability of such materials in practice. Therefore, they can be used as self-monitoring sensors controlling development of cracks; as sensors monitoring moisture content or when treated by an external electrical voltage as heat sources used for deicing of material's surface layer. Alkali-activated aluminosilicates (AAA), as competing materials to cement-based materials, are intensively investigated in the present due to their superior durability and environmental impact. Whereas the electrical properties of AAA are similar to those cement-based, they can be enhanced in the same way. In both cases, it is crucial to find a reasonable amount of electrically conductive phase to design composites with a sufficient electrical conductivity at an affordable price. In this paper, electrical properties of composites based on AAA binder and electrically conductive admixture represented by carbon nanotubes (CNT) are investigated. Measurements of electrical properties are carried out by means of 2-probes DC technique on nine types of samples; reference sample without the conductive phase and samples with CNT admixture in amount of 0.1 % - 2.5 % by vol. A significant increase of the electrical conductivity starts from the amount of 0.5 % CNT admixture and in case of 2.5 % CNT is about three orders of magnitude higher compared to the reference sample.

  7. Universality of the electrical transport in granular metals

    PubMed Central

    Bakkali, Hicham; Dominguez, Manuel; Batlle, Xavier; Labarta, Amílcar

    2016-01-01

    The universality of the ac electrical transport in granular metals has been scarcely studied and the actual mechanisms involved in the scaling laws are not well understood. Previous works have reported on the scaling of capacitance and dielectric loss at different temperatures in Co-ZrO2 granular metals. However, the characteristic frequency used to scale the conductivity spectra has not been discussed, yet. This report provides unambiguous evidence of the universal relaxation behavior of Pd-ZrO2 granular thin films over wide frequency (11 Hz–2 MHz) and temperature ranges (40–180 K) by means of Impedance Spectroscopy. The frequency dependence of the imaginary parts of both the impedance Z″ and electrical modulus M″ exhibit respective peaks at frequencies ωmax that follow a thermal activation law, ωmax ∝ exp(T1/2). Moreover, the real part of electrical conductivity σ′ follows the Jonscher’s universal power law, while the onset of the conductivity dispersion also corresponds to ωmax. Interestingly enough, ωmax can be used as the scaling parameter for Z″, M″ and σ′, such that the corresponding spectra collapse onto single master curves. All in all, these facts show that the Time-Temperature Superposition Principle holds for the ac conductance of granular metals, in which both electron tunneling and capacitive paths among particles compete, exhibiting a well-characterized universal behavior. PMID:27411671

  8. Universality of the electrical transport in granular metals.

    PubMed

    Bakkali, Hicham; Dominguez, Manuel; Batlle, Xavier; Labarta, Amílcar

    2016-07-14

    The universality of the ac electrical transport in granular metals has been scarcely studied and the actual mechanisms involved in the scaling laws are not well understood. Previous works have reported on the scaling of capacitance and dielectric loss at different temperatures in Co-ZrO2 granular metals. However, the characteristic frequency used to scale the conductivity spectra has not been discussed, yet. This report provides unambiguous evidence of the universal relaxation behavior of Pd-ZrO2 granular thin films over wide frequency (11 Hz-2 MHz) and temperature ranges (40-180 K) by means of Impedance Spectroscopy. The frequency dependence of the imaginary parts of both the impedance Z″ and electrical modulus M″ exhibit respective peaks at frequencies ωmax that follow a thermal activation law, ωmax ∝ exp(T(1/2)). Moreover, the real part of electrical conductivity σ' follows the Jonscher's universal power law, while the onset of the conductivity dispersion also corresponds to ωmax. Interestingly enough, ωmax can be used as the scaling parameter for Z″, M″ and σ', such that the corresponding spectra collapse onto single master curves. All in all, these facts show that the Time-Temperature Superposition Principle holds for the ac conductance of granular metals, in which both electron tunneling and capacitive paths among particles compete, exhibiting a well-characterized universal behavior.

  9. Universality of the electrical transport in granular metals

    NASA Astrophysics Data System (ADS)

    Bakkali, Hicham; Dominguez, Manuel; Batlle, Xavier; Labarta, Amílcar

    2016-07-01

    The universality of the ac electrical transport in granular metals has been scarcely studied and the actual mechanisms involved in the scaling laws are not well understood. Previous works have reported on the scaling of capacitance and dielectric loss at different temperatures in Co-ZrO2 granular metals. However, the characteristic frequency used to scale the conductivity spectra has not been discussed, yet. This report provides unambiguous evidence of the universal relaxation behavior of Pd-ZrO2 granular thin films over wide frequency (11 Hz-2 MHz) and temperature ranges (40-180 K) by means of Impedance Spectroscopy. The frequency dependence of the imaginary parts of both the impedance Z″ and electrical modulus M″ exhibit respective peaks at frequencies ωmax that follow a thermal activation law, ωmax ∝ exp(T1/2). Moreover, the real part of electrical conductivity σ‧ follows the Jonscher’s universal power law, while the onset of the conductivity dispersion also corresponds to ωmax. Interestingly enough, ωmax can be used as the scaling parameter for Z″, M″ and σ‧, such that the corresponding spectra collapse onto single master curves. All in all, these facts show that the Time-Temperature Superposition Principle holds for the ac conductance of granular metals, in which both electron tunneling and capacitive paths among particles compete, exhibiting a well-characterized universal behavior.

  10. Conceptual design of hybrid-electric transport aircraft

    NASA Astrophysics Data System (ADS)

    Pornet, C.; Isikveren, A. T.

    2015-11-01

    The European Flightpath 2050 and corresponding Strategic Research and Innovation Agenda (SRIA) as well as the NASA Environmentally Responsible Aviation N+ series have elaborated aggressive emissions and external noise reduction targets according to chronological waypoints. In order to deliver ultra-low or even zero in-flight emissions levels, there exists an increasing amount of international research and development emphasis on electrification of the propulsion and power systems of aircraft. Since the late 1990s, a series of experimental and a host of burgeouning commercial activities for fixed-wing aviation have focused on glider, ultra-light and light-sport airplane, and this is proving to serve as a cornerstone for more ambitious transport aircraft design and integration technical approaches. The introduction of hybrid-electric technology has dramatically expanded the design space and the full-potential of these technologies will be drawn through synergetic, tightly-coupled morphological and systems integration emphasizing propulsion - as exemplified by the potential afforded by distributed propulsion solutions. With the aim of expanding upon the current repository of knowledge associated with hybrid-electric propulsion systems a quad-fan arranged narrow-body transport aircraft equipped with two advanced Geared-Turbofans (GTF) and two Electrical Fans (EF) in an under-wing podded installation is presented in this technical article. The assessment and implications of an increasing Degree-of-Hybridization for Useful Power (HP,USE) on the overall sizing, performance as well as flight technique optimization of fuel-battery hybrid-electric aircraft is addressed herein. The integrated performance of the concept was analyzed in terms of potential block fuel burn reduction and change in vehicular efficiency in comparison to a suitably projected conventional aircraft employing GTF-only propulsion targeting year 2035. Results showed that by increasing HP,USE, significant

  11. Electrical properties of epoxy resin based nano-composites

    SciTech Connect

    Tuncer, Enis; Sauers, Isidor; James, David Randy; Ellis, Alvin R; Paranthaman, Mariappan Parans; Aytug, Tolga; Sathyamurthy, Srivatsan; More, Karren Leslie; Li, Jing; Goyal, Amit

    2007-01-01

    We investigate the electrical properties of composite materials prepared as nano and sub-micro scale metal-oxide particles embedded in a commercial resin. The filler particles are barium titanate and calcium copper titanate. The physical and structural characteristics of constituents and the fabricated composites are reported. The electrical characterization of the composite samples are performed with the time- and frequency-domain dielectric spectroscopy techniques. The electrical breakdown strength of samples with nano and sub-micron size particles have better electrical insulation properties than the unfilled resin.

  12. Electrical transport anisotropy of uniaxial polycrystalline samples and the effective medium approximation: An application to HTS

    NASA Astrophysics Data System (ADS)

    Cruz-García, A.; Muné, P.

    2016-08-01

    In this paper we have applied the effective medium approximation (EMA) to a polycrystalline sample made up of uniaxial crystallites with similar behavior to the high critical temperature superconductors (HTS) at the normal state (σab ≫ σc). As a result the dependence of the anisotropy parameter at the level of the sample, μ =σx /σz , on orientation probability of the grains' a-axes along a certain preferential direction, γxa is obtained. The intrinsic and shape anisotropy parameters of the crystallites constitute input data. In addition, the dependence of the orientation factor, f, which has been introduced in current models on the transport properties of HTS, is calculated as a function of γxa. These results offer a tool to interpret electrical transport measurements at normal state in granular uniaxial superconducting materials with certain texture degree, by means of the correlation between microstructure and electrical transport properties. Moreover, the comparison between the model and some experimental data suggests the presence of intragranular planar defects in the polycrystalline superconductors. They may affect the measurement of paracoherent resistivity and consequently the determination of f mainly in Bi based samples.

  13. 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.

  14. Elastic and transport properties in polycrystals of crackedgrains: Cross-property relations and microstructure

    SciTech Connect

    Berryman, J.G.

    2007-10-02

    Some arguments of Bristow (1960) concerning the effects of cracks on elastic and transport (i.e., electrical or thermal conduction) properties of cold-worked metals are reexamined. The discussion is posed in terms of a modern understanding of bounds and estimates for physical properties of polycrystals--in contrast to Bristow's approach using simple mixture theory. One type of specialized result emphasized here is the cross-property estimates and bounds that can be obtained using the methods presented. Our results ultimately agree with those of Bristow, i.e., confirming that microcracking is not likely to be the main cause of the observed elastic behavior of cold-worked metals. However, it also becomes clear that the mixture theory approach to the analysis is too simple and that crack-crack interactions are necessary for proper quantitative study of Bristow's problem.

  15. Electrical properties and transport mechanisms of Au/Ba0.6Sr0.4TiO3/GaN metal-insulator-semiconductor (MIS) diode at high temperature range

    NASA Astrophysics Data System (ADS)

    Rajagopal Reddy, V.

    2016-05-01

    The electrical and transport mechanisms of a fabricated Au/Ba0.6Sr0.4TiO3 (BST)/GaN metal-insulator-semiconductor (MIS) diode have been studied in the temperature range of 280-430 K by current-voltage ( I- V) and capacitance-voltage ( C- V) measurements. The barrier heights (BHs) of the Au/BST/GaN MIS diode are found to be 0.85 eV ( I- V)/1.35 ( C- V) at 280 K and 1.14 eV ( I- V)/1.17 ( C- V) at 430 K. The series resistance ( R S) values determined by Cheung's functions are in good agreement with each other. The difference between BHs estimated by I- V and C- V methods are also discussed. Results show that the estimated interface state density ( N SS) of MIS diode decreases with an increase in temperature. Observations have indicated that the BH increases whereas ideality factor R S and N SS decreases with increasing temperature. Results have demonstrated that the reverse leakage current is dominated by Poole-Frenkel emission at temperatures of 280-340 K and by Schottky emission at temperatures of 370-430 K. It is also noted that there is a transition of the conduction mechanism in Au/BST/GaN MIS diode from Poole-Frenkel to Schottky emission at temperatures of 340-370 K.

  16. Temperature dependence of the electrical properties of hydrogen titanate nanotubes

    SciTech Connect

    Alves, Diego C. B.; Brandão, Frederico D.; Krambrock, Klaus; Ferlauto, Andre S.; Fonseca, Fabio C.

    2014-11-14

    The temperature dependence of the electrical properties of hydrogen-rich titanate nanotubes (H-TNTs) in the 90–270 °C range was investigated by impedance spectroscopy. Three types of dominant conduction were found which depend on the previous thermal treatment of the samples. For untreated samples, at low temperatures (T < 100 °C), electrical conductivity is relatively high (>10{sup −4} S/cm at T ≈ 90 °C) and is dominated by protonic transport within structural water molecules. For thermal annealing in inert atmosphere up to 150 °C, water molecules are released from the nanotube structure resulting in a dehydrated H{sub 2}Ti{sub 3}O{sub 7} phase. Such phase has a low, thermally-dependent, electrical conductivity (10{sup −8} S/cm at T ≈ 90 °C) with activation energy of 0.68 eV. For samples annealed up to 260 °C, loss of OH groups, and consequent generation of oxygen vacancies, occurs that result in the non-stoichiometric H{sub 2(1−z)}Ti{sub 3}O{sub 7−z} phase. This phase has much higher conductivity (10{sup −5} S/cm at T ≈ 90 °C) and lower associated activation energy (0.40 eV). The generation of oxygen vacancies is confirmed by electron paramagnetic resonance measurements at room temperature, which revealed the presence of single-electron-trapped oxygen vacancies. The activation energy value found is consistent with the thermal ionization energy of the oxygen vacancies. Such defect formation represents the initial stage of the phase transformation from titanate to TiO{sub 2} (B). X-ray diffraction and Raman spectroscopy measurements also support such interpretation.

  17. Electrical transport in three-dimensional cubic Skyrmion crystal

    NASA Astrophysics Data System (ADS)

    Zhang, Xiao-Xiao; Nagaosa, Naoto

    2015-03-01

    Two-dimensional magnetic Skyrmions have been well confirmed via various experimental techniques in the bulk or on epitaxial thin films. Besides, a topologically nontrivial three-dimensional cubic Skyrmion crystal in the bulk, which is essentially a hedgehog-antihedgehog pair texture predicted theoretically, has also been tentatively observed. Equipped with a sophisticated spectral analysis program, we adopt Matsubara Green's function technique to study electrical transport, especially diagonal conductivity, in such system. We consider conduction electrons interacting with spinwaves via the strong Hund's rule coupling, wherein fluctuation of monopolar emergent electromagnetic field exits within adiabatic approximation. We describe in detail the influence of temperature and Skyrmion number on both dc and ac conductivities. Possible deviation from Fermi liquid behavior will also be discussed.

  18. Electrical transport and thermometry of electroformed titanium dioxide memristive switches

    NASA Astrophysics Data System (ADS)

    Borghetti, Julien; Strukov, Dmitri B.; Pickett, Matthew D.; Yang, J. Joshua; Stewart, Duncan R.; Williams, R. Stanley

    2009-12-01

    We investigated the electrical transport of electroformed titanium dioxide memristive switches from liquid helium to room temperatures in order to better understand their internal states. After electroforming, we observed a continuous transition between two distinct limiting behaviors: a nearly Ohmic "ON"-state and an "OFF"-state characterized by conduction through a barrier. We interpret our data in terms of a model in which the electroforming step creates a conducting channel that does not completely bridge the metal contacts on the titanium dioxide film. The switching then occurs as a result of voltage-induced changes in the oxygen vacancy concentration in the gap between the tip of the channel and the adjacent metal contact. We used the metallic resistivity of the conduction channel as an in situ thermometer to measure the local device temperature, thus revealing an important implicit state variable.

  19. Resilient design of recharging station networks for electric transportation vehicles

    SciTech Connect

    Kris Villez; Akshya Gupta; Venkat Venkatasubramanian

    2011-08-01

    As societies shift to 'greener' means of transportation using electricity-driven vehicles one critical challenge we face is the creation of a robust and resilient infrastructure of recharging stations. A particular issue here is the optimal location of service stations. In this work, we consider the placement of battery replacing service station in a city network for which the normal traffic flow is known. For such known traffic flow, the service stations are placed such that the expected performance is maximized without changing the traffic flow. This is done for different scenarios in which roads, road junctions and service stations can fail with a given probability. To account for such failure probabilities, the previously developed facility interception model is extended. Results show that service station failures have a minimal impact on the performance following robust placement while road and road junction failures have larger impacts which are not mitigated easily by robust placement.

  20. Fuel cells for electric utility and transportation applications

    NASA Astrophysics Data System (ADS)

    Srinivasan, S.

    1980-04-01

    The status of fuel cell development is reviewed. For terrestrial electric utility applications, the most promising are phosphoric acid, molten carbonate and solid electrolyte fuel cells. The first will be coupled with a reformer (to convert natural gas, petroleum derived and biomass fuels to hydrogen) while the second and third with a coal gasifier. As ground transportation power sources, the promising systems are phosphoric (or alternate acid) and alkaline electrolyte fuel cells. In the first case, methanol is most attractive while in the second, it will be hydrogen stored as a compressed gas or as a hydride. A technoeconomic assessment of a 'Regenerative Hydrogen-Halogen Energy Storage System' demonstrates the prospects of its use for load leveling when coupled with nuclear, solar or wind power plants.

  1. Transmission electron microscopy and electrical transport investigations performed on the same single-walled carbon nanotube

    SciTech Connect

    Philipp, G.; Burghard, M.; Roth, S.

    1998-08-11

    Electrical transport measurements and high resolution transmission electron microscopy performed on the same (rope of) single-walled carbon nanotube(s) (SWCNTs) allow to establish links between structural and electronic properties of the tubes. The tubes are deposited on electron transparent ultrathin Si{sub 3}N{sub 4}-membranes bearing Cr/AuPd-electrodes defined by electron beam lithography. TEM-micrographs of the setup reveal mostly ropes consisting of 2-3 tubes which also appear on a scanning force microscope image of the same area. A current-voltage trace of the ropes at 4.2 K is also presented.

  2. Optical absorption and electrical transport in hybrid TiO2 and polymer nanocomposite films

    NASA Astrophysics Data System (ADS)

    Zhou, Xi-Song; Li, Zheng; Wang, Ning; Lin, Yuan-Hua; Nan, Ce-Wen

    2006-06-01

    Hybrid nanofilms of poly(2-methoxy-5-ethylhexyloxy-1,4-phenylene)vinylene (MEH-PPV) and anatase-TiO2 nanoparticles were prepared. The results showed that the optical absorption spectra and electrical transport properties of the TiO2/MEH-PPV nanocomposite films were strongly dependent on the particle size and concentration of TiO2 nanoparticles in the hybrid films. In comparison with pure TiO2 nanofilms, the hybrid TiO2/MEH-PPV films presented a shift of the absorption edge to the lower-energy region, and an obvious nonlinear current-voltage characteristic.

  3. 76 FR 4724 - Emerson Transportation Division, a Division of Emerson Electric, Including Workers Located...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-26

    ..., Including Workers Located Throughout the United States; Bridgeton, MO; Amended Certification Regarding... Emerson Transportation Division, a division of Emerson Electric, including workers located throughout...

  4. Incoherence-coherence crossover and low-temperature Fermi-liquid-like behavior in AFe2As2 (A  =  K, Rb, Cs): evidence from electrical transport properties

    NASA Astrophysics Data System (ADS)

    Xiang, Z. J.; Wang, N. Z.; Wang, A. F.; Zhao, D.; Sun, Z. L.; Luo, X. G.; Wu, T.; Chen, X. H.

    2016-10-01

    We study the normal-state transport properties of AFe2As2 (A  =  K, Rb and Cs) single crystals using Hall coefficient, resistivity and magnetoresistance (MR) measurements. In all three materials, the Hall coefficient R H shows a strong temperature dependence, which is typical for multi-band systems. In particular, R H develops an upturn below a characteristic temperature {{T}\\ast} , which is in agreement with the incoherence-coherence crossover reported in recent nuclear magnetic resonance studies. A Fermi-liquid-like state, characterized by T 2 behavior of the resistivity and a positive orbital MR obeying Kohler’s rule, emerges below T FL  ˜0.4 ~{{T}\\ast} . The superconducting transition temperature T c experiences a simultaneous suppression with {{T}\\ast} and T FL as the alkali ion’s radius increases from A  =  K to A  =  Cs, suggesting that the unconventional superconductivity in the AFe2As2 series is related to the strength of the electronic coherence. A phase diagram, similar to that in the heavy fermion Kondo lattice system, is obtained. Based on all the experimental evidence, we argue that the physical properties of this family of heavily hole-doped Fe-based superconductors are controlled by the hybridization between itinerant carriers and localized orbitals, and the Kondo scenario could be effective in such a case.

  5. 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.

  6. Electronic Properties of Bilayer Graphene Strongly Coupled to Interlayer Stacking and an External Electric Field

    NASA Astrophysics Data System (ADS)

    Park, Changwon; Ryou, Junga; Hong, Suklyun; Sumpter, Bobby G.; Kim, Gunn; Yoon, Mina

    2015-07-01

    Bilayer graphene (BLG) with a tunable band gap appears interesting as an alternative to graphene for practical applications; thus, its transport properties are being actively pursued. Using density functional theory and perturbation analysis, we investigated, under an external electric field, the electronic properties of BLG in various stackings relevant to recently observed complex structures. We established the first phase diagram summarizing the stacking-dependent gap openings of BLG for a given field. We further identified high-density midgap states, localized on grain boundaries, even under a strong field, which can considerably reduce the overall transport gap.

  7. Surface electrical properties experiment, part 1. [flown on Apollo 17

    NASA Technical Reports Server (NTRS)

    Strangway, D. W.; Annan, A. P.; Redman, J. D.; Rossiter, J. R.; Rylaarsdam, J. A.; Watts, R. D.

    1974-01-01

    The work is reported which was performed on the Surface Electrical Properties Experiment Data Acquisition System. Areas discussed include: data handling and processing, installation and external signal application, operation of the equipment, and digital output. Detailed circuit descriptions are included.

  8. Transport properties of ribbon-shaped carbon fibers: Property-structure relationship

    NASA Astrophysics Data System (ADS)

    Gallego, Nidia Constanza

    Mesophase pitch-based carbon fibers are an ideal material for applications in which high rates of heat dissipation and low mass are required. Unfortunately, the high cost of current commercial high thermal conductivity mesophase pitch-based carbon fibers has limited their use in high volume applications. Understanding how the structure develops during the fiber formation process and how this structure relates to the final fiber properties is the way to optimizing the fiber properties while reducing the processing costs. Ribbon-shaped fibers have been developed at Clemson University and are being evaluated as a low-cost high thermal conductivity alternative fiber to traditional round-shaped fibers. However, the characterization of the thermal transport properties of carbon fibers is a difficult and time-consuming process. The objectives of this study were to evaluate the transport (both thermal and electronic) properties of ribbon-shaped fibers produced from an AR mesophase at different processing conditions, to characterize the structure of these fibers, to study their structure-property relationships, and to develop a model capable of estimating the thermal conductivity of carbon fibers based upon their structural parameters. For this purpose, several sets of ribbon fibers were produced from an AR mesophase at different spinning temperatures and shear rates and heat treated at a final temperature of 2400°C. The electrical resistivities, magnetoresistances and thermal conductivities of these fibers were measured and the structural parameters were determined with x-ray techniques. Two approaches (a short-fiber composite, and a periodic composite) were utilized to model the relationship between the structure of the fiber and its thermal conductivity. The results of this study confirmed that ribbon-shaped fibers develop excellent transport properties at lower graphitization temperatures than those used commercially for round-shaped fibers. Additionally, for the first

  9. Electrical properties of granite with implications for the lower crust.

    USGS Publications Warehouse

    Olhoeft, G.R.

    1981-01-01

    The electrical properties of granite appear to be dominantly controlled by the amount of free water in the granite and by temperature. Minor contributions to the electrical properties are provided by hydrostatic and lithostatic pressure, structurally bound water, oxygen fugacity, and other parameters. The effect of sulphur fugacity may be important but is experimentally unconfirmed. In addition to changing the magnitude of electrical properties, the amount and chemistry of water in granite significantly changes the temperature dependence of the electrical properties. With increasing temperature, changes in water content retain large, but lessened, effects on electrical properties. Near room temperature, a monolayer of water will decrease the electrical resistivity by an order of magnitude. Several weight-percent water may decrease the electrical resistivity by as much as nine orders of magnitude and decrease the thermal activation energy by a factor of five. At elevated temperatures just below granitic melting, a few weight-percent water may still decrease the resistivity by as much as 3 orders of magnitude and the activation energy by a factor of two.-Author

  10. An on-chip electrical transport spectroscopy approach for in situ monitoring electrochemical interfaces

    NASA Astrophysics Data System (ADS)

    Ding, Mengning; He, Qiyuan; Wang, Gongming; Cheng, Hung-Chieh; Huang, Yu; Duan, Xiangfeng

    2015-08-01

    In situ monitoring electrochemical interfaces is crucial for fundamental understanding and continued optimization of electrocatalysts. Conventional spectroscopic techniques are generally difficult to implement for in situ electrochemical studies. Here we report an on-chip electrical transport spectroscopy approach for directly probing the electrochemical surfaces of metallic nanocatalysts in action. With a four-electrode device configuration, we demonstrate that the electrical properties of ultrafine platinum nanowires are highly sensitive and selective to the electrochemical surface states, enabling a nanoelectronic signalling pathway that reveals electrochemical interface information during in-device cyclic voltammetry. Our results not only show a high degree of consistency with generally accepted conclusions in platinum electrochemistry but also offer important insights on various practically important electrochemical reactions. This study defines a nanoelectronic strategy for in situ electrochemical surface studies with high surface sensitivity and surface specificity.

  11. An on-chip electrical transport spectroscopy approach for in situ monitoring electrochemical interfaces

    PubMed Central

    Ding, Mengning; He, Qiyuan; Wang, Gongming; Cheng, Hung-Chieh; Huang, Yu; Duan, Xiangfeng

    2015-01-01

    In situ monitoring electrochemical interfaces is crucial for fundamental understanding and continued optimization of electrocatalysts. Conventional spectroscopic techniques are generally difficult to implement for in situ electrochemical studies. Here we report an on-chip electrical transport spectroscopy approach for directly probing the electrochemical surfaces of metallic nanocatalysts in action. With a four-electrode device configuration, we demonstrate that the electrical properties of ultrafine platinum nanowires are highly sensitive and selective to the electrochemical surface states, enabling a nanoelectronic signalling pathway that reveals electrochemical interface information during in-device cyclic voltammetry. Our results not only show a high degree of consistency with generally accepted conclusions in platinum electrochemistry but also offer important insights on various practically important electrochemical reactions. This study defines a nanoelectronic strategy for in situ electrochemical surface studies with high surface sensitivity and surface specificity. PMID:26245937

  12. Versatile variable temperature insert at the DEIMOS beamline for in situ electrical transport measurements.

    PubMed

    Joly, L; Muller, B; Sternitzky, E; Faullumel, J G; Boulard, A; Otero, E; Choueikani, F; Kappler, J P; Studniarek, M; Bowen, M; Ohresser, P

    2016-05-01

    The design and the first experiments are described of a versatile cryogenic insert used for its electrical transport capabilities. The insert is designed for the cryomagnet installed on the DEIMOS beamline at the SOLEIL synchrotron dedicated to magnetic characterizations through X-ray absorption spectroscopy (XAS) measurements. This development was spurred by the multifunctional properties of novel materials such as multiferroics, in which, for example, the magnetic and electrical orders are intertwined and may be probed using XAS. The insert thus enables XAS to in situ probe this interplay. The implementation of redundant wiring and careful shielding also enables studies on operating electronic devices. Measurements on magnetic tunnel junctions illustrate the potential of the equipment toward XAS studies of in operando electronic devices.

  13. 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.

  14. Transport properties and nanosensors of oxide nanowires and nanobelts

    NASA Astrophysics Data System (ADS)

    Lao, Changshi

    ZnO is one of the most important materials for electronics, optoelectronics, piezoelectricity and optics. With a wide band gap of 3.37eV and an exiton binding energy of 60meV, ZnO ID nanostructures exhibit promising properties in a lot of optical device applications. It is also an important piezoelectric material and has applications in a new category of nanodevices, nano-piezotronics. Demonstrated prototype of devices includes nanogenerators, piezoelectric-FET, and a series of evolutive devices based on the concept of nanogenerator. This is based on working principle of a semiconductor and piezoelectric coupled property. This thesis is about the growth, characterization and device fabrication of ZnO nanowires and nanobelts for sensors and UV detectors. First, the fundamental synthesis of ZnO nanostructurs is investigated, particularly polar surface dominated nanostructues, to illustrate the unique growth configurations of ZnO nanobelts, nanorings and nanosprings. Detail study in this part includes nanobelts, nanorings, nanocombs, nanonetworks, and nanodiskettes synthesis. Important factors in driving the nanostructure synthesis mechanism are analyzed, such as the chemical activities of different surface of ZnO, the abundant of available Zn ions in the vapor, and the polar surface dominated effects. These factors contribute to the large abundant available ZnO nanostructures. Then, the devices fabricated methods using individual nanowires/nanobelts and their electrical transport properties were carefully characterized. In this part, dominant factors which are critical for nanobelt device performance are investigated, such as the contact properties, interface effects, and durability testing. Also, a metal doping method is studied to explore the controlling and modification of nanowire electric and optical properties. Research results obtained here provide a basic and thoroughly understanding the control process and fabrication criteria in building a functional

  15. Effect of interfacial properties on polymer-nanocrystal thermoelectric transport.

    PubMed

    Coates, Nelson E; Yee, Shannon K; McCulloch, Bryan; See, Kevin C; Majumdar, Arun; Segalman, Rachel A; Urban, Jeffrey J

    2013-03-20

    The electrical behavior of a conducting-polymer/inorganic-nanowire composite is explained with a model in which carrier transport occurs predominantly through a highly conductive volume of polymer that exists at the polymer-nanowire interface. This result highlights the importance of controlling nanoscale interfaces for thermoelectric materials, and provides a general route for improving carrier transport in organic/inorganic composites.

  16. Magneto-transport properties of PbSe single crystals

    NASA Astrophysics Data System (ADS)

    Anand, Naween; Martin, Catalin; Gu, Genda; Tanner, David

    PbSe is a low-gap semiconductor with excellent infrared photodetection properties. Here we report our high magnetic field and low temperature electrical properties measurement performed on a moderately doped PbSe single crystals with p-type bulk carrier density of around 1×1018 cm-3. Longitudinal resistance (Rxx) and Hall resistance (Rxy) were simultaneously measured between 0 T and 18 T, and at temperatures between 0.8 K and 25 K, show quantum oscillations above 6 T. The quantum oscillation frequency is ~15 T, giving an estimate for the carrier density of each L pocket in the BZ participating in these oscillations. The effective mass of the free carriers is estimated from the temperature dependence of oscillation amplitudes. Measurements as the magnetic fields is rotated reveal the magneto-transport properties of a 3D-like fermi surface. Dingle temperature and free carrier scattering rate has been estimated and compared to optical measurements. Optical measurements also show a low frequency phonon mode around 45 cm-1 and bandgap of around 0.2 eV along with other interband electronic transitions.

  17. Thermal to electricity conversion using thermal magnetic properties

    DOEpatents

    West, Phillip B [Idaho Falls, ID; Svoboda, John [Idaho Falls, ID

    2010-04-27

    A system for the generation of Electricity from Thermal Energy using the thermal magnetic properties of a Ferromagnetic, Electrically Conductive Material (FECM) in one or more Magnetic Fields. A FECM is exposed to one or more Magnetic Fields. Thermal Energy is applied to a portion of the FECM heating the FECM above its Curie Point. The FECM, now partially paramagnetic, moves under the force of the one or more Magnetic Fields. The movement of the FECM induces an electrical current through the FECM, generating Electricity.

  18. Chemical and electrical properties of cavities in silicon and germanium

    SciTech Connect

    Myers, S.M.; Follstaedt, D.M.; Petersen, G.A.; Seager, C.H.; Stein, H.J.; Wampler, W.R.

    1994-12-31

    Cavities were formed in Si and Ge by He ion implantation and annealing, and resultant chemical and electrical properties were investigated. The dissociation energies for Si-H and Ge-H surface monohydride bonds were determined, showing that H chemisorption on Si is energetically stable with respect H{sub 2} gas whereas H chemisorption on Ge is not. Cavity walls in Si were found to trap transition metals strongly, suggesting application to impurity gettering in devices. Measurement and modeling of cavity electrical properties elucidated surface electronic states and indicated a potential for controlled electrical isolation in devices. 35 refs.

  19. Magnetic, specific heat and electrical transport properties of Frank-Kasper cage compounds RTM2Al20 [R  =  Eu, Gd and La; TM  =  V, Ti

    NASA Astrophysics Data System (ADS)

    Kumar, K. Ramesh; Nair, Harikrishnan S.; Christian, Reinke; Thamizhavel, A.; Strydom, André M.

    2016-11-01

    Single crystals of Frank-Kasper compounds RTM2Al20 (R  =  Eu, Gd and La; TM  =  V and Ti) were grown by self-flux method and their physical properties were investigated through magnetization (M), magnetic susceptibility (χ), specific heat (C P) and electrical resistivity (ρ) measurements. Powder x-ray diffraction studies and structural analysis showed that these compounds crystallize in the cubic crystal structure with the space group Fd\\bar{3}m . The magnetic susceptibility for the compounds EuTi2Al20 and GdTi2Al20 showed a sudden jump below the Néel temperature T N indicative of plausible double magnetic transition. Specific heat (C P) and electrical resistivity (ρ) measurements also confirm the first-order magnetic transition (FOMT) and possible double magnetic transitions. Temperature variation of heat capacity showed a sharp phase transition and huge C P value for the (Eu/Gd)Ti2Al20 compounds’ full width at half-maximum (FWHM) (<0.2 K) which is reminiscent of a first-order phase transition and a unique attribute among RTM2Al20 compounds. In contrast, linear variation of C P is observed in the ordered state for (Eu/Gd)V2Al20 compounds suggesting a λ-type transition. We observed clear anomaly between heating and cooling cycle in temperature-time relaxation curve for the compounds GdTi2Al20 (2.38 K) and EuTi2Al20 (3.2 K) which is indicating a thermal arrest due to the latent heat. The temperature variation of S mag for GdTi2Al20 saturates to a value 0.95R\\ln 8 while the other magnetic systems exhibited still lower entropy saturation values in the high temperature limit. ≤ft({{C}\\text{P}}-γ T\\right)/{{T}3} versus T plot showed a maximum near 27 K for all the compounds indicating the presence of low frequency Einstein modes of vibrations. Resistivity measurements showed that all the samples behave as normal Fermi liquid type compounds and ρ (T) due to electron-phonon scattering follows Bloch-Grüneisen-Mott relation in the

  20. Electrical properties of epoxy resin based nano-composites

    NASA Astrophysics Data System (ADS)

    Tuncer, Enis; Sauers, Isidor; James, D. Randy; Ellis, Alvin R.; Parans Paranthaman, M.; Aytug, Tolga; Sathyamurthy, Srivatsan; More, Karren L.; Li, Jing; Goyal, Amit

    2007-01-01

    We investigate the electrical properties of composite materials prepared as nano- and sub-micron-scale metal-oxide particles embedded in a commercial resin. The filler particles are barium titanate and calcium copper titanate. The physical and structural characteristics of the constituents and the fabricated composites are reported. Electrical characterization of the composite samples is performed using time- and frequency-domain dielectric spectroscopy techniques. The electrical breakdown strength of samples with nano- and sub-micron-sized particles have better electrical insulation properties than the unfilled resin. The start-up funding for the research was provided by the US Department of Energy, Office of Electricity Delivery and Energy Reliability, and follow-on funding was continued by the Laboratory Directed Research and Development (LDRD) Program of Oak Ridge National Laboratory (ORNL), managed by UT-Battelle, LLC for the US Department of Energy under Contract No. DE-AC05-00OR22725 (D06-100).

  1. Networks of semiconducting SWNTs: contribution of midgap electronic states to the electrical transport.

    PubMed

    Itkis, Mikhail E; Pekker, Aron; Tian, Xiaojuan; Bekyarova, Elena; Haddon, Robert C

    2015-08-18

    Single-walled carbon nanotube (SWNT) thin films provide a unique platform for the development of electronic and photonic devices because they combine the advantages of the outstanding physical properties of individual SWNTs with the capabilities of large area thin film manufacturing and patterning technologies. Flexible SWNT thin film based field-effect transistors, sensors, detectors, photovoltaic cells, and light emitting diodes have been already demonstrated, and SWNT thin film transparent, conductive coatings for large area displays and smart windows are under development. While chirally pure SWNTs are not yet commercially available, the marketing of semiconducting (SC) and metallic (MT) SWNTs has facilitated progress toward applications by making available materials of consistent electronic structure. Nevertheless the electrical transport properties of networks of separated SWNTs are inferior to those of individual SWNTs. In particular, for semiconducting SWNTs, which are the subject of this Account, the electrical transport drastically differs from the behavior of traditional semiconductors: for example, the bandgap of germanium (E = 0.66 eV) roughly matches that of individual SC-SWNTs of diameter 1.5 nm, but in the range 300-100 K, the intrinsic carrier concentration in Ge decreases by more than 10 orders of magnitude while the conductivity of a typical SC-SWNT network decreases by less than a factor of 4. Clearly this weak modulation of the conductivity hinders the application of SC-SWNT films as field effect transistors and photodetectors, and it is the purpose of this Account to analyze the mechanism of the electrical transport leading to the unusually weak temperature dependence of the electrical conductivity of such networks. Extrinsic factors such as the contribution of residual amounts of MT-SWNTs arising from incomplete separation and doping of SWNTs are evaluated. However, the observed temperature dependence of the conductivity indicates the

  2. Transport properties of alkali metal doped fullerides

    SciTech Connect

    Yadav, Daluram Yadav, Nishchhal

    2015-07-31

    We have studied the intercage interactions between the adjacent C{sub 60} cages and expansion of lattice due to the intercalation of alkali atoms based on the spring model to estimate phonon frequencies from the dynamical matrix for the intermolecular alkali-C{sub 60} phonons. We considered a two-peak model for the phonon density of states to investigate the nature of electron pairing mechanism for superconducting state in fullerides. Coulomb repulsive parameter and the electron phonon coupling strength are obtained within the random phase approximation. Transition temperature, T{sub c}, is obtained in a situation when the free electrons in lowest molecular orbital are coupled with alkali-C{sub 60} phonons as 5 K, which is much lower as compared to reported T{sub c} (20 K). The superconducting pairing is mainly driven by the high frequency intramolecular phonons and their effects enhance it to 22 K. The importance of the present study, the pressure effect and normal state transport properties are calculated within the same model leading superconductivity.

  3. Magnetic and transport properties of PrRhSi3.

    PubMed

    Anand, V K; Adroja, D T; Hillier, A D

    2013-05-15

    We have investigated the magnetic and transport properties of a noncentrosymmetric compound PrRhSi3 by dc magnetic susceptibility χ(T), isothermal magnetization M(H), thermoremanent magnetization M(t), specific heat Cp(T), electrical resistivity ρ(T,H) and muon spin relaxation (μSR) measurements. At low fields χ(T) shows two anomalies near 15 and 7 K with an irreversibility between ZFC and FC data below 15 K. In contrast, no anomaly is observed in Cp(T) or ρ(T) data. M(H) data at 2 K exhibit very sharp increase below 0.5 T and a weak hysteresis. M(t) exhibits very slow relaxation, typical for a spin-glass system. Even though the absence of any anomaly in Cp(T) is consistent with the spin-glass type behavior, there is no obvious origin of spin-glass behavior in this structurally well ordered compound. The crystal electric field (CEF) analysis of Cp(T) data indicates a CEF-split singlet ground state lying below a doublet at 81(1) K and a quasi-triplet at 152(2) K. The ρ(T) data indicate a metallic behavior, and ρ(H) exhibits a very high positive magnetoresistance, as high as ~300% in 9 T at 2 K. No long range magnetic order or spin-glass behavior was detected in a μSR experiment down to 1.2 K.

  4. Modeling the transport properties of epitaxially grown thermoelectric oxide thin films using spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Sarath Kumar, S. R.; Abutaha, Anas I.; Hedhili, M. N.; Alshareef, H. N.

    2012-01-01

    The influence of oxygen vacancies on the transport properties of epitaxial thermoelectric (Sr,La)TiO3 thin films is determined using electrical and spectroscopic ellipsometry (SE) measurements. Oxygen vacancy concentration was varied by ex-situ annealing in Ar and Ar/H2. All films exhibited degenerate semiconducting behavior, and electrical conductivity decreased (258-133 S cm-1) with increasing oxygen content. Similar decrease in the Seebeck coefficient is observed and attributed to a decrease in effective mass (7.8-3.2 me), as determined by SE. Excellent agreement between transport properties deduced from SE and direct electrical measurements suggests that SE is an effective tool for studying oxide thin film thermoelectrics.

  5. Transport in polymer-gel composites: theoretical methodology and response to an electric field

    NASA Astrophysics Data System (ADS)

    Hill, Reghan J.

    2006-03-01

    A theoretical model of electromigrative, diffusive and convective transport in polymer-gel composites is presented. Bulk properties are derived from the standard electrokinetic model with an impenetrable charged sphere embedded in an electrolyte-saturated Brinkman medium. Because the microstructure can be carefully controlled, these materials are promising candidates for enhanced gel-electrophoresis, chemical sensing, drug delivery, and microfluidic pumping technologies. The methodology provides solutions for situations where perturbations from equilibrium are induced by gradients of electrostatic potential, concentration and pressure. While the volume fraction of the inclusions should be small, Maxwell's well-known theory of conduction suggests that the model may also be accurate at moderate volume fractions. In this work, the theory is used to compute ion fluxes, electrical current density, and convective flow driven by an electric field applied to an homogeneous composite. The electric-field-induced (electro-osmotic) flow is a sensitive indicator of the inclusion zeta-potential and size, electrolyte concentration, and Darcy permeability of the gel, while the electrical conductivity is usually independent of the polymer gel and is relatively insensitive to characteristics of the inclusions and electrolyte.

  6. Modifying Surface Energy of Graphene via Plasma-Based Chemical Functionalization to Tune Thermal and Electrical Transport at Metal Interfaces.

    PubMed

    Foley, Brian M; Hernández, Sandra C; Duda, John C; Robinson, Jeremy T; Walton, Scott G; Hopkins, Patrick E

    2015-08-12

    The high mobility exhibited by both supported and suspended graphene, as well as its large in-plane thermal conductivity, has generated much excitement across a variety of applications. As exciting as these properties are, one of the principal issues inhibiting the development of graphene technologies pertains to difficulties in engineering high-quality metal contacts on graphene. As device dimensions decrease, the thermal and electrical resistance at the metal/graphene interface plays a dominant role in degrading overall performance. Here we demonstrate the use of a low energy, electron-beam plasma to functionalize graphene with oxygen, fluorine, and nitrogen groups, as a method to tune the thermal and electrical transport properties across gold-single layer graphene (Au/SLG) interfaces. We find that while oxygen and nitrogen groups improve the thermal boundary conductance (hK) at the interface, their presence impairs electrical transport leading to increased contact resistance (ρC). Conversely, functionalization with fluorine has no impact on hK, yet ρC decreases with increasing coverage densities. These findings indicate exciting possibilities using plasma-based chemical functionalization to tailor the thermal and electrical transport properties of metal/2D material contacts.

  7. Magnetoelectric and transport properties of (GaMn)Sb thin films: A ferrimagnetic phase in dilute alloys

    NASA Astrophysics Data System (ADS)

    Calderón, Jorge A.; Mesa, F.; Dussan, A.

    2017-02-01

    We studied the electrical, magnetic, and transport properties of (GaMn)Sb thin films fabricated by the direct current magnetron co-sputtering method. Using X-ray powder diffraction measurements, we identified the presence of ferrimagnetic (Mn2Sb) and ferromagnetic (Mn2Sb2) phases within the films. We also measured the magnetization of the films versus an applied magnetic field as well as their hysteresis curves at room temperature. We determined the electrical and transport properties of the films through temperature-dependent resistivity measurements using the Van Der Pauw method. The main contribution to the transport process was variable range hopping. Hopping parameters were calculated using percolation theory and refined using the diffusional model. In addition, we determined that all samples had p type semiconductor behavior, that there was an increase in the density of localized states near the Fermi level, and that the binary magnetic phases influenced the electrical properties and transport mechanisms.

  8. The Elusive Memristor: Properties of Basic Electrical Circuits

    ERIC Educational Resources Information Center

    Joglekar, Yogesh N.; Wolf, Stephen J.

    2009-01-01

    We present an introduction to and a tutorial on the properties of the recently discovered ideal circuit element, a memristor. By definition, a memristor M relates the charge "q" and the magnetic flux [phi] in a circuit and complements a resistor R, a capacitor C and an inductor L as an ingredient of ideal electrical circuits. The properties of…

  9. Percolating silicon nanowire networks with highly reproducible electrical properties.

    PubMed

    Serre, Pauline; Mongillo, Massimo; Periwal, Priyanka; Baron, Thierry; Ternon, Céline

    2015-01-09

    Here, we report the morphological and electrical properties of self-assembled silicon nanowires networks, also called Si nanonets. At the macroscopic scale, the nanonets involve several millions of nanowires. So, the observed properties should result from large scale statistical averaging, minimizing thus the discrepancies that occur from one nanowire to another. Using a standard filtration procedure, the so-obtained Si nanonets are highly reproducible in terms of their morphology, with a Si nanowire density precisely controlled during the nanonet elaboration. In contrast to individual Si nanowires, the electrical properties of Si nanonets are highly consistent, as demonstrated here by the similar electrical properties obtained in hundreds of Si nanonet-based devices. The evolution of the Si nanonet conductance with Si nanowire density demonstrates that Si nanonets behave like standard percolating media despite the presence of numerous nanowire-nanowire intersecting junctions into the nanonets and the native oxide shell surrounding the Si nanowires. Moreover, when silicon oxidation is prevented or controlled, the electrical properties of Si nanonets are stable over many months. As a consequence, Si nanowire-based nanonets constitute a promising flexible material with stable and reproducible electrical properties at the macroscopic scale while being composed of nanoscale components, which confirms the Si nanonet potential for a wide range of applications including flexible electronic, sensing and photovoltaic applications.

  10. Electrical and galvanomagnetic properties of cadmium telluride films synthesized under highly nonequilibrium conditions

    SciTech Connect

    Belyaev, A. P. Rubets, V. P.; Antipov, V. V.; Grishin, V. V.

    2008-11-15

    The results of experimental studies of electrical and galvanomagnetic properties of CdTe films synthesized under highly nonequilibrium conditions via vapor condensation on a substrate cooled with liquid nitrogen are reported. The temperature dependences of dark conductivity, current-voltage characteristics with and without illumination, temperature dependences of the Hall coefficient R{sub H} and effective Hall mobility {mu}{sub H} in the planar geometry, and dark current-voltage characteristics in the sandwich geometry are reported. Anisotropy of conductivity is revealed. It is shown that the electrical and galvanomagnetic properties of the films are consistently described by a percolation model of charge transport, according to which, at high temperatures, the charge transport takes place over the percolation level of the valence band, and at low temperatures, over the percolation level of the impurity band.

  11. Electrical Transport and Channel Length Modulation in Semiconducting Carbon Nanotube Field-Effect Transistors

    DTIC Science & Technology

    2013-11-25

    AEROSPACE REPORT NO. ATR-2013-01138 Electrical Transport and Channel Length Modulation in Semiconducting Carbon Nanotube Field-Effect Transistors ...Transport and Channel Length Modulation in Semiconducting Carbon Nanotube Field-Effect Transistors November 25, 2013 Adam W. Bushmaker Electronics and...Electrical Transport and Channel Length Modulation in Semiconducting Carbon Nanotube Field-Effect Transistors Approved by: U^ g jj t^yt Steven C

  12. Viscosity and electric properties of water aerosols

    NASA Astrophysics Data System (ADS)

    Shavlov, A. V.; Sokolov, I. V.; Dzhumandzhi, V. A.

    2016-09-01

    The flow of water mist in a narrow duct has been studied experimentally. The profile of the velocity of drops has been measured, and the viscosity of the mist has been calculated using the Navier-Stokes equation. It has been found that at low gradients of the rate of shear the viscosity of the mist can exceed that of clean air by tens and even hundreds of times. The electric charge of the drops has been measured. It has been found that the viscosity of the mist differs from that of clean air at gradients of the rate of shear that are less than the frequency of the establishment of electric equilibrium between the drops. A comparative analysis of the viscosities of the mist and a drop cluster has been carried out, and the dependence of the viscosity of the water aerosol on the radius and the charge of the drops has been predicted. The possible role of aerosols that contain submicron drops in the known "clear air turbulence" problem has been shown.

  13. Electrical Properties of PVDF Based Nanocomposites

    NASA Astrophysics Data System (ADS)

    Contreras, Jerry; Foltz, Heinrich D.; Duan, Yuping; Hhuq, Hasina F.; Tidrow, Steven C.; Chipara, Mircea

    2015-03-01

    Nanocomposites based on polyvinylidene fluoride (PVDF) have been obtained by melt mixing, loading the polymeric matrix with various weight fraction (between 0 % to 40 %) of different fillers (multiwalled carbon nanotubes, carbon nanofibers, and barium titanate). Pellets of nanocomposites have been obtained by hot pressing at about 175 oC. Copper contacts have been deposited on the as obtained pellets and the electrical features have been measured by using the two point technique. PVDF is a semicrystalline ferroelectric and piezoelectric polymer with a glass transition temperature of -35 oC and a melting temperature of about 175 oC. Electrical measurements have been performed in a wide range of frequencies starting from dc to ac (up to about 250 MHz). The dependence of the resistivity and dielectric constant on frequency and temperature (between -50 oC to 150 oC) was investigated in detail. Supplementary DSC, WAXS, and Raman data provided detailed information regarding the effect of fillers on phase transitions (glass, crystallization, and melting) and crystalline composition/structure of these nanocomposites.

  14. Optical and electrical properties of bi-layers organic devices

    NASA Astrophysics Data System (ADS)

    Trad, Hager; Rouis, Ahlem; Davenas, Jöel; Majdoub, Mustapha

    2014-10-01

    The influence of interfacial charges on the device characteristics of bi-layers structure LEDs with poly[5-methoxy-2-octyloxy-1,4-phenylenevinylene] (MO-PPV) as active polymer layer is investigated. The concept to improve device performance is presented using: a diacetate cellulose (DAC) and a new synthetized 5-{2-(2-chloroethoxy)ethoxy}-2-{(E)-(2-pyridyl)azo}phenol (PDEG) components. The DAC and mixed (DAC+PDEG) layers were inserted between indium tin oxide (ITO) and MO-PPV polymer. The optical properties (UV-Vis) of MO-PPV, PDEG and mixed (DAC+PDEG) in solutions were studied and compared to those on thin films. Detailed current-voltage measurements of the bi-layers devices showed improvements of the threshold voltage (Vth) of the ITO/(DAC+PDEG)/MO-PPV/Al device attributed to the enhancement of carriers injection and transport resulted from the modified electrode structures. Conduction mechanisms of structure LEDs were matched with space-charge-limited current (SCLC) one. The impedance spectra for all devices can be discussed in terms of an equivalent circuit model designed as a parallel resistor Rp and capacitor Cp network in series with resistor Rs. The ITO/(DAC+PDEG)/MO-PPV/Al device showed the lowest impedance attributed to the removal of contaminants and to changes in the work function of ITO. The frequency-dependent electrical properties of the ITO/(DAC+PDEG)/MO-PPV/Al structure is analyzed by impedance spectroscopy as function of bias. We have extracted numerical values of the equivalent circuit model parameters by fitting experimental data. Their evolution with bias voltages has shown that the SCLC mechanism is characterized by an exponential trap distribution.

  15. Case Study: Transportation Initiative Incorporates Alternative Fuels and Electric Vehicles

    EPA Pesticide Factsheets

    James A. Lovell Federal Health Care Center in North Chicago, Illinois, reduced greenhouse gases by incorporating electric vehicles and alternative fuels into fleet operations. Lovell FHCC increased its electric fleet by 200 in one year.

  16. Synthesis and electrical properties of PANI-CNT-CdS nanocomposites

    NASA Astrophysics Data System (ADS)

    Goswami, M.; Mukherjee, A.; Ghosh, R.; Meikap, A. K.

    2016-05-01

    Polyaniline-CNT-CdS nanocomposite has been synthesized by the chemical oxidative polymerization reaction. The particle size of nanocomposites lies in between 2.7 to 4.8 nm. I-V characteristics of the nanocomposite shows a non linear behaviour. The dc electrical transport property of Polyaniline-CNT-CdS nanocomposites has been investigated within a temperature range 77≤T≤300K. The dc conductivity follows 3D variable range hopping (VRH) model.

  17. Morphological and electrical properties of SnS:Bi thin films

    NASA Astrophysics Data System (ADS)

    Calderón, C.; Banguero, E.; Gordillo, G.

    2014-04-01

    This work presents results regarding the influence of the Bi content on the morphology and electrical transport properties of SnS:Bi thin films grown by sulfurization of the metallic precursors on a soda-lime glass substrate. The SnS:Bi films were characterized through atomic force microscopy and electrical conductivity measurements. The results showed that the Bi content affects the grain size and roughness of the SnS:Bi films. The grain size affects the carrier mobility and therefore the electrical conductivity at room temperature. Measurements of conductivity as a function of temperature, carried out in the range between 90K and 630K, revealed the electrical transport in SnS:Bi thin films is affected by two different mechanisms: at temperatures greater than 350K, the conductivity is predominantly affected by free carrier transport in extended states of the conduction/valence band, whereas at temperatures below 350K the conductivity is mainly determined by the variable range hopping transport mechanism.

  18. Effects of an external electric field on electronic states and transport of a Bi2Se3 thin film

    NASA Astrophysics Data System (ADS)

    Liu, Genhua; Zhou, Benliang; Zhou, Guanghui

    2016-10-01

    We study the electronic band structure, density distribution, and electronic transport of surface states in a Bi2Se3 thin film. By using the four-band model, it is demonstrated that an appropriate external electric field can eliminate the coupling between the top and bottom surface states of the film, and contribute to the realization of the quantum spin Hall effects. However, a sufficient high electric field may destroy the property of the surface states. Using the scattering matrix approach, we further study theoretically the spin-dependent electron transport of a Bi2Se3 thin-film junction. Interestingly, a transverse electric field can switch on/off the spin-up or -down electronic channel of the surface states in the junction.

  19. Controlling thermal and electrical properties of graphene by strain-engineering its flexural phonons

    NASA Astrophysics Data System (ADS)

    Conley, Hiram; Nicholl, Ryan; Bolotin, Kirill

    2014-03-01

    We explore the effects of flexural phonons on the thermal and electrical properties of graphene. To control the amplitude of flexural phonons, we developed a technique to engineer uniform mechanical strain between 0 and 1% in suspended graphene. We determine the level of strain, thermal conductivity and carrier mobility of graphene through a combination of mechanical resonance and electrical transport measurements. Depending on strain, we find significant changes in the thermal expansion coefficient, thermal conductivity, and carrier mobility of suspended graphene. These changes are consistent with the expected contribution of flexural phonons.

  20. Local electric conductive property of Si nanowire models

    NASA Astrophysics Data System (ADS)

    Ikeda, Yuji; Senami, Masato; Tachibana, Akitomo

    2012-12-01

    Local electric conductive properties of Si nanowire models are investigated by using two local electric conductivity tensors, {{σ }limits^{leftrArr }}_{ext}(r) and {{σ }limits^{leftrArr }}_{int}(r), defined in Rigged QED. It is emphasized that {{σ }limits^{leftrArr }}_{int}(r) is defined as the response of electric current to the actual electric field at a specific point and does not have corresponding macroscopic physical quantity. For the Si nanowire models, there are regions which show complicated response of electric current density to electric field, in particular, opposite and rotational ones. Local conductivities are considered to be available for the study of a negative differential resistance (NDR), which may be related to this opposite response. It is found that {{σ }limits^{leftrArr }}_{int}(r) shows quite different pattern from {{σ }limits^{leftrArr }}_{ext}(r), local electric conductivity defined for the external electric field. The effects of impurities are also studied by using the model including a Ge atom, in terms of the local response to electric field. It is found that the difference from the pristine model is found mainly around the Ge atom.

  1. Study of the effect of the charge transport layer in the electrical characteristics of the organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Rahimi, Ronak; Roberts, Alex; Narang, V.; Kumbham, Vamsi Krishna; Korakakis, D.

    2013-09-01

    Significant progress in fabrication and optimization of organic photovoltaics (OPVs) has been made during the last decade. The main reason for popularity of OPVs is due to their low production cost, large area devices and compatibility with flexible substrates 1-3. Various approaches including optimizing morphology of the active layers 1, 2, introducing new materials as the donor and acceptor 3,4, new device structures such as tandem structure 5, 6 have been adapted to improve the efficiency of the organic photovoltaics. However, electrical characteristics of the OPVs do not only depend on the active layer materials or device structure. They can also be defined by the interface properties between active layers and the charge transport layers or the metal contacts. Within this paper, the effect of the thickness variation of the charge transport layer in the electrical properties of the bilayer heterojunction OPVs has been studied. Several devices with CuPc/PTCDI-C8 as the donor/acceptor layers have been fabricated with different thicknesses of electron transport layer. MoO3 and Alq3 have been used respectively as the hole transport layer (HTL) and the electron transport layer (ETL). It has been shown that the S-shape effect in the current-voltage curve is attributed to the accumulation of the charge carriers at the interface between the active layer and the charge transport layer 5, 7.

  2. Study of the effect of the charge transport layer in the electrical characteristics of the organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Rahimi, Ronak; Roberts, Alex; Narang, V.; Kumbham, Vamsi Krishna; Korakakis, D.

    2013-03-01

    Significant progress in fabrication and optimization of organic photovoltaics (OPVs) has been made during the last decade. The main reason for popularity of OPVs is due to their low production cost, large area devices and compatibility with flexible substrates [1-3]. Various approaches including optimizing morphology of the active layers [1,2], introducing new materials as the donor and acceptor [3,4], new device structures such as tandem structure [5,6] have been adapted to improve the efficiency of the organic photovoltaics. However, electrical characteristics of the OPVs do not only depend on the active layer materials or device structure. They can also be defined by the interface properties between active layers and the charge transport layers or the metal contacts. Within this paper, the effect of the thickness variation of the charge transport layer in the electrical properties of the bilayer heterojunction OPVs has been studied. Several devices with CuPc/PTCDI-C8 as the donor/acceptor layers have been fabricated with different thicknesses of electron transport layer. MoO3 and Alq3 have been used respectively as the hole transport layer (HTL) and the electron transport layer (ETL). It has been shown that the S-shape effect in the current-voltage curve is attributed to the accumulation of the charge carriers at the interface between the active layer and the charge transport layer [5,7].

  3. Integrative Modeling of Electrical Properties of Pacemaker Cardiac Cells

    NASA Astrophysics Data System (ADS)

    Grigoriev, M.; Babich, L.

    2016-06-01

    This work represents modeling of electrical properties of pacemaker (sinus) cardiac cells. Special attention is paid to electrical potential arising from transmembrane current of Na+, K+ and Ca2+ ions. This potential is calculated using the NaCaX model. In this respect, molar concentration of ions in the intercellular space which is calculated on the basis of the GENTEX model is essential. Combined use of two different models allows referring this approach to integrative modeling.

  4. Electrical transport studies of molecular beam epitaxy grown gallium manganese arsenide epilayers and heterostructures

    NASA Astrophysics Data System (ADS)

    Zhu, Meng

    2008-10-01

    Diluted magnetic semiconductors (DMS) grown by molecular beam epitaxy have been drawing attention in the context of emerging spintronics, which utilizes electron spins to develop devices with new functionalities. The canonical DMS---(Ga,Mn)As---has been on center stage for almost a decade, and extensive efforts have been dedicated to understanding its hole-mediated ferromagnetism, optimizing growth and annealing conditions to achieve higher-Tc, studying the magneto-transport, exploiting its abundant magnetic anisotropy, and so on. This dissertation focuses on three aspects of the study of (Ga,Mn)As: (1) Magneto-transport under hard magnetization reversal; (2) Electrical noise properties; and (3) Exchange-biasing and spin-dependent transport in (Ga,Mn)As/MnAs hybrid structures. The first chapter provides the motivation for this dissertation and introduces several aspects of the current understanding of (Ga,Mn)As. Both the theoretical models and experimentally established observations are reviewed, focusing on the magnetic and transport properties of (Ga,Mn)As epilayers. Next, the hybrid ferromagnetic metal/semiconductor heterostructures are introduced. As an excellent candidate for making these heterostructures, the semi-metal MnAs is reviewed in terms of its structural and magnetic properties, which are essential for making the exchange-biased devices described in Chapter 5 and Chapter 6. The second chapter describes the experimental techniques encompassed in the scope of this dissertation. Several important techniques, such as MBE growth, device patterning, magnetometry and transport measurements are discussed. The third chapter reports the first experiment in this dissertation, which describes the longitudinal magnetoresistance (MR) anomalies of a (Ga,Mn)As epilayer experiencing hard axis magnetization reversal in an perpendicular magnetic field. By probing the MRs for currents running along different crystallographic directions, the origins of these anomalies

  5. Focused helium-ion beam irradiation effects on electrical properties of multi-layer WSe2

    NASA Astrophysics Data System (ADS)

    Pudasaini, Pushpa Raj; Stanford, Michael; Cross, Nick; Duscher, Gerd; Mandrus, David; Rack, Philip

    Atomically thin transition metal dichalcogenides (TMDs) are currently receiving great attention due to their excellent opto-electronic properties. Tuning optical and electrical properties of mono and few layers TMDs, such as Tungsten diselenide (WSe2), by controlling the defects, is an intriguing opportunity to fabricate the next generation opto-electronic devices. Here, we report the effects of focused helium ion beam irradiation on structural, optical and electrical properties of few layer WSe2, via high resolution scanning transmission electron microscopy, Raman spectroscopy and electrical measurements. By controlling the ion irradiation dose, we selectively introduced precise defects in few layer WSe2 thereby locally tuning the electrically resistivity of the material. Hole transport in the few layer WSe2 is severely affected compared to electron transport for the same dose of helium ion beam irradiation studied. Furthermore, by selectively exposing the ion beams, we demonstrate the lateral p-n junction in few layer WSe2 flakes, which constitute an important advance towards two dimensional opto-electronic devices. Materials Science and Technology Division, ORNL, Oak Ridge, TN 37831, USA.

  6. TOPAZ-2 single-cell TFE electric insulation properties study

    SciTech Connect

    Vasilchenko, A.V.; Izhvanov, O.L.

    1996-03-01

    TOPAZ-II single cell thermoinic fuel element (TFE) electric insulation parameters under testing with electric heating were measured. TFE electric design schematic, experimental procedure and measurements results are described. Collector resistance was measured in helium at 420{endash}890 K. Metal ceramic ceals insulation properties were measured in vacuum P=10{sup {minus}4} Pa and in cesium vapor P=10{sup {minus}1}{minus}260 Pa, at 420{endash}730 K. Results of separate TFE are compared with the data; that were measured during nuclear power system (NPS) Ya-21U test. Based upon this data NPS power losses were estimated. {copyright} {ital 1996 American Institute of Physics.}

  7. Thermal and electrical transport in ferromagnetic metal thin films

    NASA Astrophysics Data System (ADS)

    Avery, Azure D.

    The recent emergence of spin caloritronics has focused considerable attention on the interplay between spin, charge, and temperature gradients in magnetic materials. A reliable and energy efficient method for generating pure spin currents would signify an important step toward future spin-based nano-electronics that may offer lower power consumption and greater processing capabilities. To develop new technology using thermoelectric effects in magnetic thin films, it is essential to understand thermal and electrical transport through these films. One possible source of pure spin currents is the so-called spin Seebeck effect (SSE) in which a thermal gradient (▿T) applied to a ferromagnet is thought to produce a pure spin current detectable by measuring a transverse voltage (VT) generated by the inverse spin Hall effect. However, recent work on spin-dependent transport in thin film nanostructures supported by bulk substrates has underscored the difficulty in understanding ▿T in these systems due to uncertainty in the direction of the applied ▿T through a substrate with a thermal conductance several orders of magnitude larger than the sample conductance. These results suggest that early SSE experiments may have been strongly affected by other effects such as the anomalous Nernst effect. They may also have been affected by thermoelectric effects generated from planar thermal gradients such as the planar Nernst effect which develops a VT in a film with a planar ▿T and magnetization. In this dissertation, I introduce the concepts of thermal conductivity, the Wiedemann-Franz law, and thermoelectric effects including the Seebeck effect, the Peltier effect, and the planar Nernst effect (PNE). Next, I describe our experimental method for measuring thermal and electrical transport in non magnetic and ferromagnetic metallic thin films using suspended Si-N membrane structures. Our membrane method reduces the background thermal conductance contribution by 5 orders of

  8. Nanoscale electrical properties of epitaxial Cu3Ge film

    PubMed Central

    Wu, Fan; Cai, Wei; Gao, Jia; Loo, Yueh-Lin; Yao, Nan

    2016-01-01

    Cu3Ge has been pursued as next-generation interconnection/contact material due to its high thermal stability, low bulk resistivity and diffusion barrier property. Improvements in electrical performance and structure of Cu3Ge have attracted great attention in the past decades. Despite the remarkable progress in Cu3Ge fabrication on various substrates by different deposition methods, polycrystalline films with excess Ge were frequently obtained. Moreover, the characterization of nanoscale electrical properties remains challenging. Here we show the fabrication of epitaxial Cu3Ge thin film and its nanoscale electrical properties, which are directly correlated with localized film microstructures and supported by HRTEM observations. The average resistivity and work function of epitaxial Cu3Ge thin film are measured to be 6 ± 1 μΩ cm and ~4.47 ± 0.02 eV respectively, qualifying it as a good alternative to Cu. PMID:27363582

  9. Transport and magnetic properties in topological materials

    NASA Astrophysics Data System (ADS)

    Liang, Tian

    The notion of topology has been the central topic of the condensed matter physics in recent years, ranging from 2D quantum hall (QH) and quantum spin hall (QSH) states, 3D topological insulators (TIs), topological crystalline insulators (TCIs), 3D Dirac/Weyl semimetals, and topological superconductors (TSCs) etc. The key notion of the topological materials is the bulk edge correspondence, i.e., in order to preserve the symmetry of the whole system (bulk+edge), edge states must exist to counter-compensate the broken symmetry of the bulk. Combined with the fact that the bulk is topologically protected, the edge states are robust due to the bulk edge correspondence. This leads to interesting phenomena of chiral edge states in 2D QH, helical edge states in 2D QSH, "parity anomaly'' (time reversal anomaly) in 3D TI, helical edge states in the mirror plane of TCI, chiral anomaly in Dirac/Weyl semimetals, Majorana fermions in the TSCs. Transport and magnetic properties of topological materials are investigated to yield intriguing phenomena. For 3D TI Bi1.1Sb0.9Te 2S, anomalous Hall effect (AHE) is observed, and for TCI Pb1-x SnxSe, Seebeck/Nernst measurements reveal the anomalous sign change of Nernst signals as well as the massive Dirac fermions. Ferroelectricity and pressure measurements show that TCI Pb1-xSnxTe undergoes quantum phase transition (QPT) from trivial insulator through Weyl semimetal to anomalous insulator. Dirac semimetals Cd3As2, Na 3Bi show interesting results such as the ultrahigh mobility 10 7cm2V-1s-1 protected from backscattering at zero magnetic field, as well as anomalous Nernst effect (ANE) for Cd3As2, and the negative longitudinal magnetoresistance (MR) due to chiral anomaly for Na3Bi. In-plane and out-of-plane AHE are observed for semimetal ZrTe5 by in-situ double-axes rotation measurements. For interacting system Eu2Ir2O7, full angle torque magnetometry measurements reveal the existence of orthogonal magnetization breaking the symmetry of

  10. Electrical properties and applications of carbon nanotube structures.

    PubMed

    Bandaru, Prabhakar R

    2007-01-01

    The experimentally verified electrical properties of carbon nanotube structures and manifestations in related phenomena such as thermoelectricity, superconductivity, electroluminescence, and photoconductivity are reviewed. The possibility of using naturally formed complex nanotube morphologies, such as Y-junctions, for new device architectures are then considered. Technological applications of the electrical properties of nanotube derived structures in transistor applications, high frequency nanoelectronics, field emission, and biological sensing are then outlined. The review concludes with an outlook on the technological potential of nanotubes and the need for new device architectures for nanotube systems integration.

  11. Correlation of magnetic properties with deformation in electrical steels

    NASA Astrophysics Data System (ADS)

    Papadopoulou, S.

    2016-03-01

    This paper investigates the utilization of magnetic Barkhausen Noise (MBN) and hysteresis loops methods for the non-destructive characterization of deformed electrical steel samples. For this reason electrical steel samples were subjected to uniaxial tensile tests on elastic and plastic region of deformations. Both the MBN and hysteresis loops were measured. The results shown a strong degradation of the magnetic properties on plastically strains. This was attributed to the irreversible movement of the magnetic domain walls, due to the presence of high dislocation density. The resulting magnetic properties were further evaluated by examining the microstructure of the deformed samples by using scanning electron microscopy.

  12. Electric Transport Phenomena of Nanocomposite Organic Polymer Thin Films

    NASA Astrophysics Data System (ADS)

    Jira, Nicholas C.; Sabirianov, Ildar; Ilie, Carolina C.

    We discuss herein the nanocomposite organic thin film diodes for the use of plasmonic solar cells. This experimental work follows the theoretical calculations done for plasmonic solar cells using the MNPBEM toolbox for MatLab. These calculations include dispersion curves and amount of light scattering cross sections for different metallic nanoparticles. This study gives us clear ideas on what to expect from different metals, allowing us to make the best choice on what to use to obtain the best results. One specific technique for light trapping in thin films solar cells utilizes metal nanoparticles on the surface of the semiconductor. The characteristics of the metal, semiconductor interface allows for light to be guided in between them causing it to be scattered, allowing for more chances of absorption. The samples were fabricated using organic thin films made from polymers and metallic nanoparticles, more specifically Poly(1-vinylpyrrolidone-co-2-dimethylaminoethyl methacrylate) copolymer and silver or gold nanoparticles. The two fabrication methods applied include spin coating and Langmuir-Blodgett technique. The transport properties are obtained by analyzing the I-V curves. We will also discuss the resistance, resistivity, conductance, density of charge carriers. SUNY Oswego SCAC Grant.

  13. Graphene transport properties upon exposure to PMMA processing and heat treatments

    NASA Astrophysics Data System (ADS)

    Gammelgaard, Lene; Caridad, José M.; Cagliani, Alberto; Mackenzie, David M. A.; Petersen, Dirch H.; Booth, Timothy J.; Bøggild, Peter

    2014-12-01

    The evolution of graphene's electrical transport properties due to processing with the polymer polymethyl methacrylate (PMMA) and heat are examined in this study. The use of stencil (shadow mask) lithography enables fabrication of graphene devices without the usage of polymers, chemicals or heat, allowing us to measure the evolution of the electrical transport properties during individual processing steps from the initial as-exfoliated to the PMMA-processed graphene. Heating generally promotes the conformation of graphene to SiO2 and is found to play a major role for the electrical properties of graphene while PMMA residues are found to be surprisingly benign. In accordance with this picture, graphene devices with initially high carrier mobility tend to suffer a decrease in carrier mobility, while in contrast an improvement is observed for low carrier mobility devices. We explain this by noting that flakes conforming poorly to the substrate will have a higher carrier mobility which will however be reduced as heat treatment enhance the conformation. We finally show the electrical properties of graphene to be reversible upon heat treatments in air up to 200 °C.

  14. Imaging spectral electrical properties of variably saturated porous media

    NASA Astrophysics Data System (ADS)

    Kelter, Matthias; Huisman, Johann A.; Kemna, Andreas; Zimmermann, Egon; Vereecken, Harry

    2013-04-01

    The spatial distribution of unsaturated hydraulic conductivity in the subsurface is of importance for hydrological modeling. Conventional methods to determine unsaturated hydraulic properties in the field are invasive and typically have a poor spatial resolution. In order to overcome these drawbacks, geophysical methods have received much attention in the last decades. Recent results of electrical impedance spectroscopy (EIS) on a range of saturated and unsaturated porous media revealed promising relationships between spectral electrical and hydraulic properties. Therefore, spectral electrical impedance tomography (EIT) is a promising method to image hydraulic properties in the subsurface. While this approach is emerging for aquifer characterization, unsaturated hydraulic properties have not yet been determined by EIT. In order to do so, a laboratory setup has been developed to perform controlled infiltration, drainage and stationary flow experiments on soil columns. A lysimeter with a height of 50 cm and a diameter of 22 cm is equipped with 40 electrodes and 4 tensiometers. An irrigation device at the top controlled by a peristaltic pump is used for a constant and homogeneous infiltration. Outflow is controlled by a suction plate at the bottom where an adjustable vacuum of up to 500 hPa can be applied. In a first measurement series, spectral EIT measurements were performed on a homogeneous sand column during stepwise drainage of the saturated porous medium using predefined pressure at the bottom. First results show that with decreasing water content the low frequency phase shift of complex electrical conductivity increases. This is consistent with previously reported EIS results. Calibrated relationships between electrical and hydraulic properties were used to convert the resulting electrical into hydraulic conductivity images.

  15. Effect of Alignment on Transport Properties of Carbon Nanotube/Metallic Junctions

    NASA Technical Reports Server (NTRS)

    Wincheski, Buzz; Namkung, Min; Smits, Jan; Williams, Phillip; Harvey, Robert

    2003-01-01

    Ballistic and spin coherent transport in single walled carbon nanotubes (SWCNT) are predicted to enable high sensitivity single-nanotube devices for strain and magnetic field sensing. Based upon these phenomena, electron beam lithography procedures have been developed to study the transport properties of purified HiPCO single walled carbon nanotubes for development into sensory materials for nondestructive evaluation. Purified nanotubes are dispersed in solvent suspension and then deposited on the device substrate before metallic contacts are defined and deposited through electron beam lithography. This procedure produces randomly dispersed ropes, typically 2 - 20 nm in diameter, of single walled carbon nanotubes. Transport and scanning probe microscopy studies have shown a good correlation between the junction resistance and tube density, alignment, and contact quality. In order to improve transport properties of the junctions a technique has been developed to align and concentrate nanotubes at specific locations on the substrate surface. Lithographic techniques are used to define local areas where high frequency electric fields are to be concentrated. Application of the fields while the substrate is exposed to nanotube-containing solution results in nanotube arrays aligned with the electric field lines. A second electron beam lithography layer is then used to deposit metallic contacts across the aligned tubes. Experimental measurements are presented showing the increased tube alignment and improvement in the transport properties of the junctions.

  16. Stacking-dependent transport properties in few-layers graphene

    NASA Astrophysics Data System (ADS)

    Lima, Matheus Paes; Padilha, José Eduardo; Pontes, Renato Borges; Fazzio, Adalberto; Silva, Antônio José Roque da

    2017-01-01

    By performing ab initio electronic structure and transport calculations, we investigated the effects of the stacking order (Bernal (AB) and rhombohedral (ABC)) as well as the number of layers, in the electronic structure and charge transport of few-layers graphene (FLG). We observed that for the ABC stack the transport properties are derived from surface states close to the Fermi level connected to dispersive states with an exponential penetration towards the inner layers, whereas for the AB stacking the transport is distributed over all layers. We present a simple model for the resistances as a function of the number of layers which contemplates the different contribution of the surface and inner layers for the transport. However, even if the stackings AB and ABC present completely different electronic and transport properties, both present the same cohesive energies, showing the absence of a thermodynamical preference for a given kind of stacking.

  17. Theoretical studies of effects of 2D plasmonic grating on electrical properties of organic solar cells

    NASA Astrophysics Data System (ADS)

    Sha, Wei E. I.; Choy, Wallace C. H.; Chew, Weng Cho

    2012-09-01

    Although various optical designs and physical mechanisms have been studied both experimentally and theoretically to improve the optical absorption of organic solar cells (OSCs) by incorporating metallic nanostructures, the effects of plasmonic nanostructures on the electrical properties of OSCs is still not fully understood. Hence, it is highly desirable to study the changes of electrical properties induced by plasmonic structures and the corresponding physics for OSCs. In this work, we develop a multiphysics model for plasmonic OSCs by solving the Maxwell's equations and semiconductor equations (Poisson, continuity, and drift-diffusion equations) with unified finite-difference method. Both the optical and electrical properties of OSCs incorporating a 2D metallic grating anode are investigated. For typical active polymer materials, low hole mobility, which is about one magnitude smaller than electron mobility, dominates the electrical property of OSCs. Since surface plasmon resonances excited by the metallic grating will produce concentrated near-field penetrated into the active polymer layer and decayed exponentially away from the metal-polymer interface, a significantly nonuniform and extremely high exciton generation rate is obtained near the grating. Interestingly, the reduced recombination loss and the increased open-circuit voltage can be achieved in plasmonic OSCs. The physical origin of the phenomena lies at direct hole collections to the metallic grating anode with a short transport path. In comparison with the plasmonic OSC, the hole transport in a multilayer planar OSC experiences a long transport path and time because the standard planar OSC has a high exciton generation rate at the transparent front cathode. The unveiled multiphysics is particularly helpful for designing high-performance plasmonic OSCs.

  18. Intrinsic non-ohmic electronic transport properties of the transparent In-Zn-O compound nanobelts under ohmic contact and out of the space charge limited transport region

    NASA Astrophysics Data System (ADS)

    Wen, Jing; Zhang, Xitian; Gao, Hong

    2016-02-01

    It is generally accepted that the nonlinear I-V characteristics for semiconductor nanostructures are mainly induced by the Schottky contacts or by the space charge limited transport mechanism. We perform I-V measurements on undoped and doped In-Zn-O compound nanobelts and confirm that their intrinsic non-ohmic transport behaviors are not caused by these mechanisms. A model based on the hopping assisted trap state electrons transport process is introduced to explain the nonlinear I-V characteristics and to extract their electrical parameters. An understanding of this trap-state influenced carrier transport can advance the progress of nanomaterials applications and enable us to distinguish their intrinsic transport behaviors from contact effects. The results also indicate that the material has good electrical properties and can be used as a potential substitute for In2O3.

  19. Surface electrical properties experiment study phase, volume 2

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The choice of an antenna for a subsurface radio sounding experiment is discussed. The radiation properties of the antennas as placed on the surface of the medium is examined. The objective of the lunar surface electrical properties experiment is described. A numerical analysis of the dielectric permittivity and magnetic permeability of a subsurface domain is developed. The application of electromagnetic field measurements between one or more transmitting antennas and a roving receiving station is explained.

  20. Passive electrical properties of rod outer segments

    PubMed Central

    Falk, Gertrude; Fatt, P.

    1968-01-01

    1. Measurements on a packed suspension of randomly oriented, dark-adapted frog rods at frequencies of 15 c/s-0·5 Mc/s indicate a behaviour similar to that of other biological materials. 2. Results are analysed on the assumption that the low-frequency limiting resistance is determined by current flowing in the suspending medium and that, of the rods, two thirds are oriented perpendicular to the applied field and one third parallel to it. Those parallel to the field are treated as non-conductors. 3. From the high-frequency limiting resistance the conductivity of the rod interior is calculated to vary linearly with the conductivity of the medium. The slope of the relation of internal to external conductivity is 0·50 with a limiting internal conductivity (at zero external) of 280 μmho/cm. 4. On the assumption that the suspension can be represented as a single-capacitance network, the characteristic frequency of impedance is used to calculate a capacitance for the rod surface of 1·54 μF/cm2. On the assumption of a distribution in properties of the suspension according to the theory of Bruggeman, the capacitance is calculated to have a value of about one half this. 5. At frequencies below 5 kc/s the impedance locus deviates from the curve describing the behaviour at higher frequencies. It is suggested that this may involve conduction in a thin layer extending along the surface of the rod. PMID:5685292

  1. Correlation of normal and superconducting transport properties on textured Bi-2212 ceramic thin rods

    NASA Astrophysics Data System (ADS)

    Natividad, E.; Castro, M.; Burriel, R.; Angurel, L. A.; Díez, J. C.; Navarro, R.

    2002-07-01

    The electric and thermal properties well above and below Tc of Bi-2212 textured ceramics have been correlated through a careful analysis of the microstructure and the transport measurements. Thin rods with the same Bi-2122 stoichiometry and textured by a laser floating zone technique have been studied with that aim. By changing the growth parameters, it has been possible to produce strong changes in microstructure and critical current density, Jc, with small variations in the thermal conductivity. The existence of phase and composition gradients across the thin rods, which explains the variations of Tc, makes the relation difficult between the normal state resistivity and Jc (77 K). A simple qualitative analysis that takes into account the observed microstructure has been developed to correlate the electric transport properties in the normal and in the superconducting states.

  2. Crystallization and Transport Properties of Amorphous Cr-Si Thin Film Thermoelectrics

    NASA Astrophysics Data System (ADS)

    Novikov, S. V.; Burkov, A. T.; Schumann, J.

    2014-06-01

    We studied the thermoelectric properties, crystallization, and stability of amorphous and nanocrystalline states in Cr-Si composite films. Amorphous films, prepared by magnetron sputtering, were transformed into the nanocrystalline state by annealing with in situ thermopower and electrical resistivity measurements. We have found that the amorphous state is stable in these film composites to about 550 K. Prior to crystallization, the amorphous films undergo a structural relaxation, detected by peculiarities in the temperature dependences of the transport properties, but not visible in x-ray or electron diffraction. The magnitude and temperature dependences of electrical conductivity and thermopower indicate that electron transport in the amorphous films is through extended states. The amorphous films are crystallized at annealing temperatures above 550 K into a nanocrystalline composite with an average grain size of 10-20 nm.

  3. Temperature effects on the electrical properties of multiphase polymer composites

    NASA Astrophysics Data System (ADS)

    De Vivo, Biagio; Guadagno, Liberata; Lamberti, Patrizia; Raimondo, Marialuigia; Spinelli, Giovanni; Tucci, Vincenzo; Vertuccio, Luigi; Vittoria, Vittoria

    2014-05-01

    A study concerning the temperature dependence of some electrical properties of multiphase nanocomposite systems based on epoxy matrix, loaded with a 1% of multi-walled carbon nanotube (MWCNT) and different amounts of Hydrotalcite clay (HT), is presented. An extensive electrical characterization in DC was carried out highlighting that, consistently with the fluctuation-induced tunneling model, the electrical resistivity of the composites are characterized by a negative temperature coefficient (NTC) since it decreases monotonically with increasing temperature in the range 30-110°C. Furthermore, current-voltage (I-V) and temperature-voltage (T-V) characteristics with a perfect linear behavior are detected. The influence of different clay content on the electrical performance of the composites is also investigated. The interesting results open a new routes for such composites due their possible applications in the field of temperature sensor.

  4. Mechanical and Electrical Properties of Cryo-worked Cu

    NASA Astrophysics Data System (ADS)

    Bettinali, Livio; Tosti, Silvano; Pizzuto, Aldo

    2014-01-01

    For manufacturing the magnets of fusion machines pure copper of both high mechanical resistance and electrical conductivity is required. Though high purity copper guarantees high electrical conductivity, its mechanical properties may be not suitable for the applications in tokamaks. In this view, a new procedure developed for obtaining high purity copper with excellent mechanical strength is described in this work. Samples of oxygen free copper (OFC) have been worked by pressing in liquid nitrogen (77 K). It has been verified that the mechanical properties of the worked metal are strongly dependent on the strain rate. Very low strain rates permitted to attain values of tensile yield strength (550 MPa) significantly higher than those obtained by traditional cold-working at room temperature (450 MPa). The electrical conductivity of the cryo-worked Cu decreases with the tensile yield strength even though the hardest samples of tensile yield strength of 550 MPa exhibit still acceptable values of conductivity (about 94 % IACS at room temperature).

  5. Preparation and electrical properties of oil-based magnetic fluids

    NASA Astrophysics Data System (ADS)

    Sartoratto, P. P. C.; Neto, A. V. S.; Lima, E. C. D.; Rodrigues de Sá, A. L. C.; Morais, P. C.

    2005-05-01

    This paper describes an improvement in the preparation of magnetic fluids for electrical transformers. The samples are based on surface-coated maghemite nanoparticles dispersed in transformer insulating oil. Colloidal stability at 90°C was higher for oleate-grafted maghemite-based magnetic fluid, whereas decanoate and dodecanoate-grafted samples were very unstable. Electrical properties were evaluated for samples containing 0.80%-0.0040% maghemite volume fractions. Relative permittivity varied from 8.8 to 2.1 and the minimum value of the loss factor was 12% for the most diluted sample. The resistivity falls in the range of 0.7-2.5×1010Ωm, whereas the ac dielectric strength varied from 70to79kV. These physical characteristics reveal remarkable step forward in the properties of the magnetic fluid samples and may result in better operation of electrical transformers.

  6. Composite Materials with Magnetically Aligned Carbon Nanoparticles Having Enhanced Electrical Properties and Methods of Preparation

    NASA Technical Reports Server (NTRS)

    Hong, Haiping (Inventor); Peterson, G.P. (Bud) (Inventor); Salem, David R. (Inventor)

    2016-01-01

    Magnetically aligned carbon nanoparticle composites have enhanced electrical properties. The composites comprise carbon nanoparticles, a host material, magnetically sensitive nanoparticles and a surfactant. In addition to enhanced electrical properties, the composites can have enhanced mechanical and thermal properties.

  7. Defects and transport properties of molybdenum doped indium oxide

    NASA Astrophysics Data System (ADS)

    Yoshida, Yuki; Gessert, Timothy; Wood, David; Coutts, Timothy

    2004-03-01

    Mo-doped indium oxide (IMO) films were deposited using an r.f. magnetron sputtering system under various oxygen concentrations. Using the `method of four coefficients', the conductivity, Hall, Nernst, and Seebeck coefficients were measured for IMO. These coefficients can be used with solutions to the Boltzmann transport equation to extract the carrier density-of-states effective mass, the Fermi level relative to the conduction-band minimum, and an energy-dependent scattering parameter related to the scattering mechanism. We find the conduction band is parabolic with a band effective mass of ˜ 0.32 me over a carrier concentration range from 4×10^19 to 5× 10^20 cm-3, indicating that relaxation time controls mobility in IMO. Temperature-dependent Hall measurements show that phonon and ionized-impurity scattering dominate at high mobility and high carrier concentration, respectively. We will also discuss possible defects in the film using XPS and electrical property data.

  8. Recent Progress and Future Challenges in MR Electric Properties Tomography

    PubMed Central

    Katscher, Ulrich; Kim, Dong-Hyun

    2013-01-01

    MR Electric Properties Tomography (EPT) is a lately developed medical imaging modality capable of visualizing both conductivity and permittivity of the patient at the Larmor frequency using B1 maps. The paper discusses the development of EPT reconstructions, EPT sequences, EPT experiments, and challenging issues of EPT. PMID:23573170

  9. PROPERTIES OF INTERFACES AND TRANSPORT ACROSS THEM

    EPA Science Inventory

    Much of the biological activity in cell cytoplasm occurs in compartments which are thought to form by phase separation, and many of the functions of these compartments occur by the transport or exchange of molecules across interfaces. Thus, a fundamentally based discussion of th...

  10. A computational study of the quantum transport properties of a Cu-CNT composite.

    PubMed

    Ghorbani-Asl, Mahdi; Bristowe, Paul D; Koziol, Krzysztof

    2015-07-28

    The quantum transport properties of a Cu-CNT composite are studied using a non-equilibrium Green's function approach combined with the self-consistent-charge density-functional tight-binding method. The results show that the electrical conductance of the composite depends strongly on CNT density and alignment but more weakly on chirality. Alignment with the applied bias is preferred and the conductance of the composite increases as its mass density increases.

  11. Bottom-up processing and low temperature transport properties of polycrystalline SnSe

    SciTech Connect

    Ge, Zhen-Hua; Wei, Kaya; Lewis, Hutton; Martin, Joshua; Nolas, George S.

    2015-05-15

    A hydrothermal approach was employed to efficiently synthesize SnSe nanorods. The nanorods were consolidated into polycrystalline SnSe by spark plasma sintering for low temperature electrical and thermal properties characterization. The low temperature transport properties indicate semiconducting behavior with a typical dielectric temperature dependence of the thermal conductivity. The transport properties are discussed in light of the recent interest in this material for thermoelectric applications. The nanorod growth mechanism is also discussed in detail. - Graphical abstract: SnSe nanorods were synthesized by a simple hydrothermal method through a bottom-up approach. Micron sized flower-like crystals changed to nanorods with increasing hydrothermal temperature. Low temperature transport properties of polycrystalline SnSe, after SPS densification, were reported for the first time. This bottom-up synthetic approach can be used to produce phase-pure dense polycrystalline materials for thermoelectrics applications. - Highlights: • SnSe nanorods were synthesized by a simple and efficient hydrothermal approach. • The role of temperature, time and NaOH content was investigated. • SPS densification allowed for low temperature transport properties measurements. • Transport measurements indicate semiconducting behavior.

  12. Irradiation imposed degradation of the mechanical and electrical properties of electrical insulation for future accelerator magnets

    SciTech Connect

    Polinski, J.; Chorowski, M.; Bogdan, P.; Strychalski, M.; Rijk, G. de

    2014-01-27

    Future accelerators will make extensive use of superconductors made of Nb{sub 3}Sn, which allows higher magnetic fields than NbTi. However, the wind-and-react technology of Nb{sub 3}Sn superconducting magnet production makes polyimide Kapton® non applicable for the coils' electrical insulation. A Nb{sub 3}Sn technology compatible insulation material should be characterized by high radiation resistivity, good thermal conductivity, and excellent mechanical properties. Candidate materials for the electrical insulation of future accelerator's magnet coils have to be radiation certified with respect to potential degradation of their electrical, thermal, and mechanical properties. This contribution presents procedures and results of tests of the electrical and mechanical properties of DGEBA epoxy + D400 hardener, which is one of the candidates for the electrical insulation of future magnets. Two test sample types have been used to determine the material degradation due to irradiation: a untreated one (unirradiated) and irradiated at 77 K with 11 kGy/min intense, 4MeV energy electrons beam to a total dose of 50 MGy.

  13. Transport properties in a monolayer graphene modulated by the realistic magnetic field and the Schottky metal stripe

    NASA Astrophysics Data System (ADS)

    Lu, Jian-Duo; Li, Yun-Bao; Liu, Hong-Yu; Peng, Shun-Jin; Zhao, Fei-Xiang

    2016-09-01

    Based on the transfer-matrix method, a systematic investigation of electron transport properties is done in a monolayer graphene modulated by the realistic magnetic field and the Schottky metal stripe. The strong dependence of the electron transmission and the conductance on the incident angle of carriers is clearly seen. The height, position as well as width of the barrier also play an important role on the electron transport properties. These interesting results are very useful for understanding the tunneling mechanism in the monolayer graphene and helpful for designing the graphene-based electrical device modulated by the realistic magnetic field and the electrical barrier.

  14. Electrokinetic transport of aerobic microorganisms under low-strength electric fields.

    PubMed

    Maillacheruvu, Krishnanand Y; Chinchoud, Preethi R

    2011-01-01

    To investigate the feasibility of utilizing low strength electric fields to transport commonly available mixed cultures such as those from an activated sludge process, bench scale batch reactor studies were conducted in sand and sandy loam soils. A readily biodegradable substrate, dextrose, was used to test the activity of the transported microorganisms. Electric field strengths of 7V, 10.5V, and 14V were used. Results from this investigation showed that an electric field strength of 0.46 Volts per cm was sufficient to transport activated sludge microorganisms across a sandy loam soil across a distance of about 8 cm in 72 h. More importantly, the electrokinetically transported microbial culture remained active and viable after the transport process and was biodegrade 44% of the dextrose in the soil medium. Electrokinetic treatment without microorganisms resulted in removal of 37% and the absence of any treatment yielded a removal of about 15%.

  15. Electric Field-Controlled Ion Transport In TiO2 Nanochannel.

    PubMed

    Li, Dan; Jing, Wenheng; Li, Shuaiqiang; Shen, Hao; Xing, Weihong

    2015-06-03

    On the basis of biological ion channels, we constructed TiO2 membranes with rigid channels of 2.3 nm to mimic biomembranes with flexible channels; an external electric field was employed to regulate ion transport in the confined channels at a high ionic strength in the absence of electrical double layer overlap. Results show that transport rates for both Na+ and Mg2+ were decreased irrespective of the direction of the electric field. Furthermore, a voltage-gated selective ion channel was formed, the Mg2+ channel closed at -2 V, and a reversed relative electric field gradient was at the same order of the concentration gradient, whereas the Na+ with smaller Stokes radius and lower valence was less sensitive to the electric field and thus preferentially occupied and passed the channel. Thus, when an external electric field is applied, membranes with larger nanochannels have promising applications in selective separation of mixture salts at a high concentration.

  16. Topological Nanocolloids with Facile Electric Switching of Plasmonic Properties

    SciTech Connect

    Yuan, Ye; Smalyukh, Ivan I.

    2015-12-01

    Combining topology and plasmonics paradigms in nanocolloidal systems may enable new means of pre-engineering desired composite material properties. Here we design and realize orientationally ordered assemblies of noble metal nanoparticles with genus-one topology and unusual long-range ordering mediated by their interactions with the surrounding nematic fluid host. Facile electric switching of these composites is reminiscent of that of pristine liquid crystals (LCs), but provides a means of reconfiguring the nanoparticle assembly and thus also the ensuing composite medium's optical properties. Our findings may lead to formation of new molecular-colloidal soft matter phases with unusual optical properties, as well as optical metamaterials.

  17. Review on optical and electrical properties of oxide semiconductors

    NASA Astrophysics Data System (ADS)

    Kim, Dong Lim; Kim, Hyun Jae

    2010-03-01

    Oxide semiconductors became one of the potential elements for large area electronics such as a channel for thin film transistors. Optical and electrical properties were modified by alloying or doping of several oxide materials; In2O3, ZnO, Ga2O3, and SnO2. The excellent properties achieved at the ternary or quaternary alloys could be explained by the role of each materials as a carrier controller, a conduction path, and etc. The metal oxide semiconductors were generally deposited by vacuum process but recently, alternative ways, like a sol-gel or an ink-jet printing, are suggested. In this review, diverse approaches on oxide semiconductors are shown, and an in-depth discussion of the optical and electrical properties alternation in metal oxide alloy fabricated by various methods is given.

  18. Magnetically Controlled Electronic Transport Properties of a Ferromagnetic Junction on the Surface of a Topological Insulator

    NASA Astrophysics Data System (ADS)

    Liu, Zheng-Qin; Wang, Rui-Qiang; Deng, Ming-Xun; Hu, Liang-Bin

    2015-06-01

    We have investigated the transport properties of the Dirac fermions through a ferromagnetic barrier junction on the surface of a strong topological insulator. The current-voltage characteristic curve and the tunneling conductance are calculated theoretically. Two interesting transport features are predicted: observable negative differential conductances and linear conductances tunable from unit to nearly zero. These features can be magnetically manipulated simply by changing the spacial orientation of the magnetization. Our results may contribute to the development of high-speed switching and functional applications or electrically controlled magnetization switching. Supported by National Natural Science Foundation of China under Grant Nos. 11174088, 11175067, 11274124

  19. Nanostructured semiconductors for thermoelectric energy conversion: Synthesis and transport properties

    NASA Astrophysics Data System (ADS)

    Sahoo, Pranati

    Increasing energy demands and decreasing natural energy resources have sparked search for alternative clean and renewable energy sources. For instance, currently there is a tremendous interest in thermoelectric and photovoltaic solar energy production technologies. Half-Heusler (HH) alloys are among the most popular material systems presently under widespread investigations for high temperature thermoelectric energy conversion. Approaches to increase the thermoelectric figure of merit (ZT) of HH range from (1) chemical substitution of atoms with different masses within the same atomic position in the crystal structure to optimize carrier concentration and enhance phonon scattering via mass fluctuation and (2) embedding secondary phonon scattering centers in the matrix (nanostructuring) to further reduce thermal conductivity. This work focuses on three material systems. The first part describes the synthesis and properties (thermal conductivity, electrical conductivity, magnetic) of various oxide nanostructures (NiO, Co3O4) which were subsequently used as inclusion phases in a HH matrix to reduce the thermal conductivity. Detailed reviews of the past efforts along with the current effort to optimize synthetic routes are presented. The effects of the synthesis conditions on the thermoelectric properties of compacted pellets of NiO and Co3O4 are also discussed. The second part of the work discusses the development of synthetic strategies for the fabrication of p-type and n-type bulk nanostructured thermoelectric materials made of a half-Heusler matrix based on (Ti,Hf)CoSb, containing nanostructures with full-Heusler (FH) compositions and structures coherently embedded inside the half-Heusler matrix. The role of the nanostructures in the regulation of phonon and charge carrier transports within the half-heusler matrix is extensively discussed by combining transport data and electron microscopy images. It was found that the FH nanoinclusions form staggered

  20. Magnetic resonance electric property imaging of brain tissues.

    PubMed

    Zhang, Xiaotong; Zhu, Shanan; He, Bin

    2009-01-01

    The electric properties (EPs) of brain tissues, i.e., the electric conductivity and permittivity, can provide important information for diagnosis of various brain disorders. A high-field MRI system is accompanied by significant wave propagation effects, and the radio frequency (RF) radiation is dependent on EPs of the biological tissue. Based on the measurement of the active transverse magnetic component of the applied RF field (known as B1-mapping technique), we have developed a dual-excitation algorithm, which uses two sets of measured B1 data, to noninvasively reconstruct the biological tissue's electric properties. A series of computer simulations were conducted to evaluate the feasibility and performance of the proposed method on a 3-D head model within a birdcage coil and a transverse electromagnetic coil. Compared with other B1-mapping based reconstruction algorithms, our approach provides superior performance without the need for iterative computations. The present simulation results indicate good reconstruction of electric properties of brain tissues from noninvasive MRI B1 mapping.

  1. Electrical Properties of Sand-Clay Mixtures Containing Trichloroethylene and Ethanol

    SciTech Connect

    Roberts, J J; Wildenschild, D

    2001-12-04

    A series of laboratory experiments, including the measurement of electrical properties and permeability, were performed on carefully characterized sand-clay mixtures. Different mixtures and configurations of quartz sand and 0 to 10% Na-montmorillonite clay were investigated using solutions of NaCl, CaCl{sub 2}, and deionized water. Samples containing 10% distributed clay were also studied using fluids containing 20 and 500 ppm trichloroethylene (TCE). Electrical properties were measured at frequencies between 10{sup 6} and 10{sup -2} Hz using the four-electrode method and Ag-AgCl inner electrodes on saturated samples at room temperature and 412 kPa confining pressure, corresponding to a soil depth of 15 to 20 m. Our results show that the addition of TCE has a small effect on electrical resistivity, with resistivity increasing with the addition of TCE. The influence of TCE on the electrical properties was most prominent in plots of loss tangent as a function of frequency. A loss tangent peak occurred at {approx}200 Hz. The height of the peak and the peak frequency both decrease with the addition of TCE. Further experiments were performed on samples containing a distinct clay layer parallel to current flow. Electrical properties were measured on water saturated samples and as a mixture of ethanol and water (80:20) was flowed through the sample. Resistivity increased by about a factor of four as the ethanol mixture replaced the water solution. Non-destructive x-ray imaging of the sample at various stages of dewatering indicates a decrease in the thickness of the clay layer with increasing number of pore volumes of ethanol-water flowed. Our results showed that electrical measurements are a useful tool for characterizing porous rocks and soils and that it is feasible to remotely detect the presence and follow the transport of contaminants such as TCE in the subsurface.

  2. Inward transport of a toroidally confined plasma subject to strong radial electric fields

    NASA Technical Reports Server (NTRS)

    Roth, J. R.; Krawczonek, W. M.; Powers, E. J.; Hong, J.; Kim, Y. H.

    1977-01-01

    Digitally implemented spectral analysis techniques were used to investigate the frequency-dependent fluctuation-induced particle transport across a toroidal magnetic field. When the electric field pointed radially inward, the transport was inward and a significant enhancement of the plasma density and confinement time resulted.

  3. Development of micro-four-point probe in a scanning tunneling microscope for in situ electrical transport measurement

    SciTech Connect

    Ge, Jian-Feng; Liu, Zhi-Long; Gao, Chun-Lei; Qian, Dong; Liu, Canhua E-mail: jfjia@sjtu.edu.cn; Jia, Jin-Feng E-mail: jfjia@sjtu.edu.cn

    2015-05-15

    Electrons at surface may behave differently from those in bulk of a material. Multi-functional tools are essential in comprehensive studies on a crystal surface. Here, we developed an in situ microscopic four-point probe (4PP) transport measurement system on the basis of a scanning tunneling microscope (STM). In particular, convenient replacement between STM tips and micro-4PPs enables systematic investigations of surface morphology, electronic structure, and electrical transport property of a same sample surface. Performances of the instrument are demonstrated with high-quality STM images, tunneling spectra, and low-noise electrical I-V characteristic curves of a single-layer FeSe film grown on a conductive SrTiO{sub 3} surface.

  4. Physical transport properties of marine microplastic pollution

    NASA Astrophysics Data System (ADS)

    Ballent, A.; Purser, A.; Mendes, P. de Jesus; Pando, S.; Thomsen, L.

    2012-12-01

    Given the complexity of quantitative collection, knowledge of the distribution of microplastic pollution in many regions of the world ocean is patchy, both spatially and temporally, especially for the subsurface environment. However, with knowledge of typical hydrodynamic behavior of waste plastic material, models predicting the dispersal of pelagic and benthic plastics from land sources into the ocean are possible. Here we investigate three aspects of plastic distribution and transport in European waters. Firstly, we assess patterns in the distribution of plastics found in fluvial strandlines of the North Sea and how distribution may be related to flow velocities and distance from source. Second, we model transport of non-buoyant preproduction pellets in the Nazaré Canyon of Portugal using the MOHID system after assessing the density, settling velocity, critical and depositional shear stress characteristics of such waste plastics. Thirdly, we investigate the effect of surface turbulences and high pressures on a range of marine plastic debris categories (various densities, degradation states and shapes tested) in an experimental water column simulator tank and pressure laboratory. Plastics deposited on North Sea strandlines varied greatly spatially, as a function of material composition and distance from source. Model outputs indicated that such dense production pellets are likely transported up and down canyon as a function of tidal forces, with only very minor net down canyon movement. Behaviour of plastic fragments under turbulence varied greatly, with the dimensions of the material, as well as density, playing major determining roles. Pressure was shown to affect hydrodynamic behaviours of only low density foam plastics at pressures ≥ 60 bar.

  5. Enhancement of wall jet transport properties

    DOEpatents

    Claunch, S.D.; Farrington, R.B.

    1997-02-04

    By enhancing the natural instabilities in the boundary layer and in the free shear layer of a wall jet, the boundary is minimized thereby increasing the transport of heat and mass. Enhancing the natural instabilities is accomplished by pulsing the flow of air that creates the wall jet. Such pulsing of the flow of air can be accomplished by sequentially occluding and opening a duct that confines and directs the flow of air, such as by rotating a disk on an axis transverse to the flow of air in the duct. 17 figs.

  6. Enhancement of wall jet transport properties

    DOEpatents

    Claunch, Scott D.; Farrington, Robert B.

    1997-01-01

    By enhancing the natural instabilities in the boundary layer and in the free shear layer of a wall jet, the boundary is minimized thereby increasing the transport of heat and mass. Enhancing the natural instabilities is accomplished by pulsing the flow of air that creates the wall jet. Such pulsing of the flow of air can be accomplished by sequentially occluding and opening a duct that confines and directs the flow of air, such as by rotating a disk on an axis transverse to the flow of air in the duct.

  7. Noise-assisted energy transport in electrical oscillator networks with off-diagonal dynamical disorder

    PubMed Central

    León-Montiel, Roberto de J.; Quiroz-Juárez, Mario A.; Quintero-Torres, Rafael; Domínguez-Juárez, Jorge L.; Moya-Cessa, Héctor M.; Torres, Juan P.; Aragón, José L.

    2015-01-01

    Noise is generally thought as detrimental for energy transport in coupled oscillator networks. However, it has been shown that for certain coherently evolving systems, the presence of noise can enhance, somehow unexpectedly, their transport efficiency; a phenomenon called environment-assisted quantum transport (ENAQT) or dephasing-assisted transport. Here, we report on the experimental observation of such effect in a network of coupled electrical oscillators. We demonstrate that by introducing stochastic fluctuations in one of the couplings of the network, a relative enhancement in the energy transport efficiency of 22.5 ± 3.6% can be observed. PMID:26610864

  8. Noise-assisted energy transport in electrical oscillator networks with off-diagonal dynamical disorder.

    PubMed

    León-Montiel, Roberto de J; Quiroz-Juárez, Mario A; Quintero-Torres, Rafael; Domínguez-Juárez, Jorge L; Moya-Cessa, Héctor M; Torres, Juan P; Aragón, José L

    2015-11-27

    Noise is generally thought as detrimental for energy transport in coupled oscillator networks. However, it has been shown that for certain coherently evolving systems, the presence of noise can enhance, somehow unexpectedly, their transport efficiency; a phenomenon called environment-assisted quantum transport (ENAQT) or dephasing-assisted transport. Here, we report on the experimental observation of such effect in a network of coupled electrical oscillators. We demonstrate that by introducing stochastic fluctuations in one of the couplings of the network, a relative enhancement in the energy transport efficiency of 22.5 ± 3.6% can be observed.

  9. Electrical and dielectric properties of bovine trabecular bone--relationships with mechanical properties and mineral density.

    PubMed

    Sierpowska, J; Töyräs, J; Hakulinen, M A; Saarakkala, S; Jurvelin, J S; Lappalainen, R

    2003-03-21

    Interrelationships of trabecular bone electrical and dielectric properties with mechanical characteristics and density are poorly known. While electrical stimulation is used for healing fractures, better understanding of these relations has clinical importance. Furthermore, earlier studies have suggested that bone electrical and dielectric properties depend on the bone density and could, therefore, be used to predict bone strength. To clarify these issues, volumetric bone mineral density (BMDvol), electrical and dielectric as well as mechanical properties were determined from 40 cylindrical plugs of bovine trabecular bone. Phase angle, relative permittivity, loss factor and conductivity of wet bovine trabecular bone were correlated with Young's modulus, yield stress, ultimate strength, resilience and BMDvol. The reproducibility of in vitro electrical and dielectric measurements was excellent (standardized coefficient of variation less than 1%, for all parameters), especially at frequencies higher than 1 kHz. Correlations of electrical and dielectric parameters with the bone mechanical properties or density were frequency-dependent. The relative permittivity showed the strongest linear correlations with mechanical parameters (r > 0.547, p < 0.01, n = 40, at 50 kHz) and with BMDvol (r = 0.866, p < 0.01, n = 40, at 50 kHz). In general, linear correlations between relative permittivity and mechanical properties or BMDvol were highest at frequencies over 6 kHz. In addition, a significant site-dependent variation of electrical and dielectric characteristics, mechanical properties and BMDvol was revealed in bovine femur (p < 0.05, Kruskall-Wallis H-test). Based on the present results, we conclude that the measurement of electrical and dielectric properties provides quantitative information that is related to bone quantity and quality.

  10. Analysis and design of nonlocal spin devices with electric-field-induced spin-transport acceleration

    NASA Astrophysics Data System (ADS)

    Takamura, Yota; Akushichi, Taiju; Shuto, Yusuke; Sugahara, Satoshi

    2015-05-01

    We apply electric-field-induced acceleration for spin transport to a four-terminal nonlocal device and theoretically analyze its Hanle-effect signals. The effect of the ferromagnetic contact widths of the spin injector and detector on the signals is carefully discussed. Although Hanle-effect signals are randomized owing to the effect of the contact widths, this can be excluded by selecting an appropriate electric field for acceleration of spin transport. Spin lifetime can be correctly extracted by nonlocal devices with electric-field acceleration even using the spin injector and detector with finite contact widths.

  11. Analysis and design of nonlocal spin devices with electric-field-induced spin-transport acceleration

    SciTech Connect

    Takamura, Yota; Akushichi, Taiju; Shuto, Yusuke; Sugahara, Satoshi

    2015-05-07

    We apply electric-field-induced acceleration for spin transport to a four-terminal nonlocal device and theoretically analyze its Hanle-effect signals. The effect of the ferromagnetic contact widths of the spin injector and detector on the signals is carefully discussed. Although Hanle-effect signals are randomized owing to the effect of the contact widths, this can be excluded by selecting an appropriate electric field for acceleration of spin transport. Spin lifetime can be correctly extracted by nonlocal devices with electric-field acceleration even using the spin injector and detector with finite contact widths.

  12. Structural and electrical transport properties of La{sub 0.8}Sm{sub 0.05}K{sub 0.15}MnO{sub 3} manganites

    SciTech Connect

    Shaikh, M. W.; Mansuri, I.; Varshney, Dinesh

    2014-04-24

    Polycrystalline sample of single-phase La{sub 0.8}Sm{sub 0.05}K{sub 0.15}MnO{sub 3} perovskite compound have been synthesized by solid-state reaction route. X-ray diffraction patterns accompanied by Rietveld–refined crystal structure parameters reveal the rhombohedral structure with space group R 3C. Electrical resistivity infers transition from metallic to insulator phase at 537 K. The application of magnetic field of 8 T, suppresses the resistivity. The metallic resistivity is retraced by considering electron–phonon, electron–electron and electron-spin-fluctuation interactions while insulating behaviour is analysed with small polaron conduction model.

  13. Human Mars Transportation Applications Using Solar Electric Propulsion

    NASA Technical Reports Server (NTRS)

    Donahue, Benjamin B.; Martin, Jim; Potter, Seth; Henley, Mark; Carrington, Connie (Technical Monitor)

    2000-01-01

    Advanced solar electric power systems and electric propulsion technology constitute viable elements for conducting human Mars transfer missions that are roughly comparable in performance to similar missions utilizing alternative high thrust systems, with the one exception being their inability to achieve short Earth-Mars trip times. A modest solar electric propulsion human Mars scenario is presented that features the use of conjunction class trajectories in concert with pre-emplacement of surface assets that can be used in a series of visits to Mars. Major elements of the Mars solar electric transfer vehicle can be direct derivatives of present state-of-the-art Solar array and electric thruster systems. During the study, several elements affecting system performance were evaluated, including varying Earth orbit altitude for departure, recapturing the transfer stage at Earth for reuse, varying power system mass-to-power ratio, and assessing solar array degradation on performance induced by Van Allen belt passage. Comparisons are made to chemical propulsion and nuclear thermal propulsion Mars vehicles carrying similar payloads.

  14. High temperature transport properties of air

    NASA Technical Reports Server (NTRS)

    Levin, E.; Partridge, Harry; Stallcop, J. R.

    1987-01-01

    A general computer code was developed to allow calculation of atom-atom and ion-atom transport collision integrals from accurate potential energy curves described by a set of discrete data points for a broad range of scattering conditions. This code is based upon semiclassical approximations that properly account for quantum mechanical behavior such as tunneling effects near a barrier maximum, resonance charge exchange, and nuclear symmetry effects. Transport collision integrals were determined for N-N, O-O, N(+)-N, and O(+)-O interactions from complete sets of accurate potential functions derived from combined experimental and ab initio structure calculations. For the O-O case, this includes results for excited states. The calculated values of the N(+)-N and O(+)-O resonance charge exchange cross section Q(ex) agree well with measurements from beam experiment that are available at high energies where the diffusion cross section Q(d) satisfies Q(d) approximately equal to 2Q(ex).

  15. Electrical Properties of Structural Components of the Crystalline Lens

    PubMed Central

    Mathias, R. T.; Rae, J. L.; Eisenberg, R. S.

    1979-01-01

    The electrical properties of the crystalline lens of the frog eye are measured with stochastic currents applied with a microelectrode near the center of the preparation and potential recorded just under the surface. The stochastic signals are decomposed by Fourier analysis into sinusoidal components, and the impedance is determined from the ratio of mean cross power to input power. The data are fit by an electrical model that includes two paths for current flow: one through the cytoplasm, gap junctions, and outer membrane; the other through inner membranes and the extracellular space between lens fibers. The electrical properties of the structures of the lens which appear as circuit components in the model are determined by the fit to the data. The resistivity of the extracellular space within the lens is comparable to the resistivity of Ringer. The outer membrane has a normal resistance of 5 kohm · cm2 but large capacitance of 10 μF/cm2, probably because it represents the properties of several layers of fibers. The inner membranes have properties reminiscent of artificial lipid bilayers: they have high membrane resistance, 2.2 megohm · cm2, and low specific capacitance, 0.8 μF/cm2. There is so much membrane within the lens, however, that the sum of the current flow across all the inner membranes is comparable to that across the outer surface. PMID:262384

  16. Structural and electrical properties of silicon hyperdoped with gold

    NASA Astrophysics Data System (ADS)

    Mathews, Jay; Liu, Yining; Malladi, Girish; Efstathiadis, Harry; Warrender, Jeffrey

    Recent advances in the field of laser hyperdoping have produced a new class of materials that could lead the way to silicon-based, CMOS-compatible infrared detectors. Using the method of ion implantation followed by pulsed laser melting (II-PLM), silicon films with impurities at concentrations well above the solid solubility limit can be fabricated. Recent work has centered around Si:Au, from which prototype IR detectors have been successfully fabricated, but there are still many questions about the structural, electrical, and optical properties of this material. In order to enhance the infrared absorption and achieve high-efficiency devices, a thorough understanding of these properties is necessary, and the processes for device fabrication must be optimized. In this work, we explore the structural and electrical properties of Si:Au hyperdoped films. Si:Au films were annealed at various temperatures, and RBS channeling was used to measure the fraction of Au atoms sitting at substitutional sites. Additionally, transmission line method (TLM) and van der Pauw (VDP) test structures were fabricated in order to investigate formation of Ohmic contacts on the hyperdoped films and to study the electrical properties of Si:Au.

  17. Magnetic and electrical properties of In doped cobalt ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Nongjai, Razia; Khan, Shakeel; Asokan, K.; Ahmed, Hilal; Khan, Imran

    2012-10-01

    Nanoparticles of CoFe2O4 and CoIn0.15Fe1.85O4 ferrites were prepared by citrate gel route and characterized to understand their structural, electrical, and magnetic properties. X-ray diffraction and Raman spectroscopy were used to confirm the formation of single phase cubic spinel structure. The average grain sizes from the Scherrer formula were below 50 nm. Microstructural features were obtained by scanning electron microscope and compositional analysis by energy dispersive spectroscopy. The hysteresis curve shows enhancement in coercivity while reduction in saturation magnetization with the substitution of In3+ ions. Enhancement of coercivity is attributed to the transition from multidomain to single domain nature. Electrical properties, such as dc resistivity as a function of temperature and ac conductivity as a function of frequency and temperature were studied for both the samples. The activation energy derived from the Arrhenius equation was found to increase in the doped sample. The dielectric constant (ɛ') and dielectric loss (tan δ) are also studied as a function of frequency and temperature. The variation of dielectric properties ɛ', tan δ, and ac conductivity (σac) with frequency reveals that the dispersion is due to Maxwell-Wagner type of interfacial polarization in general and the hopping of charge between Fe2+ and Fe3+ as well as between Co2+ and Co3+ ions at B-sites. Magnetization and electrical property study showed its dominant dependence on the grain size.

  18. Transport properties of porous media from the microstructure

    SciTech Connect

    Torquato, S.

    1995-12-31

    The determination of the effective transport properties of a random porous medium remains a challenging area of research because the properties depend on the microstructure in a highly complex fashion. This paper reviews recent theoretical and experimental progress that we have made on various aspects of this problem. A unified approach is taken to characterize the microstructure and the seemingly disparate properties of the medium.

  19. CET89 - CHEMICAL EQUILIBRIUM WITH TRANSPORT PROPERTIES, 1989

    NASA Technical Reports Server (NTRS)

    Mcbride, B.

    1994-01-01

    Scientists and engineers need chemical equilibrium composition data to calculate the theoretical thermodynamic properties of a chemical system. This information is essential in the design and analysis of equipment such as compressors, turbines, nozzles, engines, shock tubes, heat exchangers, and chemical processing equipment. The substantial amount of numerical computation required to obtain equilibrium compositions and transport properties for complex chemical systems led scientists at NASA's Lewis Research Center to develop CET89, a program designed to calculate the thermodynamic and transport properties of these systems. CET89 is a general program which will calculate chemical equilibrium compositions and mixture properties for any chemical system with available thermodynamic data. Generally, mixtures may include condensed and gaseous products. CET89 performs the following operations: it 1) obtains chemical equilibrium compositions for assigned thermodynamic states, 2) calculates dilute-gas transport properties of complex chemical mixtures, 3) obtains Chapman-Jouguet detonation properties for gaseous species, 4) calculates incident and reflected shock properties in terms of assigned velocities, and 5) calculates theoretical rocket performance for both equilibrium and frozen compositions during expansion. The rocket performance function allows the option of assuming either a finite area or an infinite area combustor. CET89 accommodates problems involving up to 24 reactants, 20 elements, and 600 products (400 of which may be condensed). The program includes a library of thermodynamic and transport properties in the form of least squares coefficients for possible reaction products. It includes thermodynamic data for over 1300 gaseous and condensed species and transport data for 151 gases. The subroutines UTHERM and UTRAN convert thermodynamic and transport data to unformatted form for faster processing. The program conforms to the FORTRAN 77 standard, except for

  20. Electric field structures in thin films: formation and properties.

    PubMed

    Cassidy, Andrew; Plekan, Oksana; Balog, Richard; Dunger, Jack; Field, David; Jones, Nykola C

    2014-08-21

    A newly discovered class of molecular materials, so-called "spontelectrics", display spontaneous electric fields. Here we show that the novel properties of spontelectrics can be used to create composite spontelectrics, illustrating how electric fields in solid films may be structured on the nanoscale by combining layers of different spontelectric materials. This is demonstrated using the spontelectric materials nitrous oxide, toluene, isoprene, isopentane, and CF2Cl2. These yield a variety of tailored electric field structures, with individual layers harboring fields between 10(7) and 10(8) V/m. Fields may be of the same sign or of opposite sign, the latter enabling the creation of nanoscale potential wells. The formation of fields is followed using an established electron beam technique, employing the ASTRID synchrotron storage ring. The influence of temperature on heterolayer structures, displaying new Curie effects, and the nature of the interfacial region between different spontelectrics are also discussed.

  1. Electrical Resistivity and Thermodynamic Properties of Iron Under High Pressure

    NASA Astrophysics Data System (ADS)

    Hieu, Ho Khac; Hai, Tran Thi; Hong, Nguyen Thi; Sang, Ngo Dinh; Tuyen, Nguyen Viet

    2017-03-01

    In this work, the electrical resistivity and thermodynamic properties of iron under high pressure have been investigated by using the semi-empirical approach. The recently well-established Grüneisen parameter expressions have been applied to derive the Debye frequency and temperature under compression. Using these results combined with the Bloch-Grüneisen law, the resistivity of iron has also been determined up to Earth's core pressures. We show that the electrical resistivity diminished gradually with pressure and saturates at high pressure. Our model gives low electrical resistivity values which are in agreement with the recent experimental measurements. The low resistivity may be attributed to the well-known resistivity saturation effect at high temperature, which was not considered in earlier models of core conductivity.

  2. Chatanika radar measurements of the electrical properties of auroral arcs

    NASA Astrophysics Data System (ADS)

    Vondrak, R. R.

    Ionospheric parameters measured in the presence of auroral arcs by the incoherent scatter Chatanika radar are used to define properties of the arcs. The radar broadcasts at 3-5 MW with a range resolution of 4.5 km along the radar line-of-sight, and has yielded auroral measurements on the variation of electron density, Hall and Pederson conductivity, horizontal electric fields, electrojet currents, precipitating electron energy flux, and the Joule heating rate. Elevation-scan techniques have been utilized to study the latitude and altitude variation of the ionospheric plasma parameters, and fixed-position scans allow determination of ionization conditions, including the electric fields and the acceleration of precipitating auroral electrons. Arcs in the diffuse aurora have been found to be local conductivity enhancements, while discrete arcs correspond to the boundary plasma sheet and have an asymmetric electric field pattern reduced on the northward side.

  3. Electric field induced by vortex transport in percolation superconductors

    NASA Astrophysics Data System (ADS)

    Kuz'min, Yu. I.

    2016-10-01

    The influence of fractal normal phase clusters on the electric field induced by the flow and creep of the magnetic flux in percolation superconductors has been considered. The current-voltage characteristics of such superconductors with allowance for the influence of the fractal dimension of cluster boundaries and the pinning barrier height have been obtained. The vortex dynamics in percolation superconductors with a fractal cluster structure in a viscous flow of the magnetic flux, the Anderson-Kim creep, and the collective flux creep has been analyzed. It has been discovered that the fractality of normal phase clusters reduces the electric field arising in the initial stage of the resistive transition.

  4. Unsaturated Zone and Saturated Zone Transport Properties (U0100)

    SciTech Connect

    J. Conca

    2000-12-20

    This Analysis/Model Report (AMR) summarizes transport properties for the lower unsaturated zone hydrogeologic units and the saturated zone at Yucca Mountain and provides a summary of data from the Busted Butte Unsaturated Zone Transport Test (UZTT). The purpose of this report is to summarize the sorption and transport knowledge relevant to flow and transport in the units below Yucca Mountain and to provide backup documentation for the sorption parameters decided upon for each rock type. Because of the complexity of processes such as sorption, and because of the lack of direct data for many conditions that may be relevant for Yucca Mountain, data from systems outside of Yucca Mountain are also included. The data reported in this AMR will be used in Total System Performance Assessment (TSPA) calculations and as general scientific support for various Process Model Reports (PMRs) requiring knowledge of the transport properties of different materials. This report provides, but is not limited to, sorption coefficients and other relevant thermodynamic and transport properties for the radioisotopes of concern, especially neptunium (Np), plutonium (Pu), Uranium (U), technetium (Tc), iodine (I), and selenium (Se). The unsaturated-zone (UZ) transport properties in the vitric Calico Hills (CHv) are discussed, as are colloidal transport data based on the Busted Butte UZTT, the saturated tuff, and alluvium. These values were determined through expert elicitation, direct measurements, and data analysis. The transport parameters include information on interactions of the fractures and matrix. In addition, core matrix permeability data from the Busted Butte UZTT are summarized by both percent alteration and dispersion.

  5. Magnetothermoelectric transport properties of multiterminal graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Wei, Miao-Miao; Zhang, Ying-Tao; Guo, Ai-Min; Liu, Jian-Jun; Xing, Yanxia; Sun, Qing-Feng

    2016-06-01

    The Peltier effect and the Ettingshausen effect are investigated in graphene nanoribbons, where charge current produces heat current along the longitudinal direction in the former case, and longitudinal charge current generates transverse heat current in the latter case. With the aid of the nonequilibrium Green's function and the Landauer-Büttiker formalism, the Peltier coefficient Πc and the Ettingshausen coefficient Ec are obtained. We found that the Kelvin relation is always valid for the longitudinal thermoelectric transport, i.e., Πc=T Sc , with T the temperature and Sc the Seebeck coefficient. In contrast, for transverse magnetothermoelectric transport, the Kelvin relation breaks down and Ec≠T Nc usually, with Nc the Nernst coefficient. In the region of weak magnetic field, the Ettingshausen effect depends strongly on device parameters. When the Fermi energy EF is close to the Dirac point, the Ettingshausen effect of the semiconducting armchair graphene nanoribbon is much stronger than that of the metallic one. When EF is far away from the Dirac point, the Ettingshausen coefficient Ec oscillates around zero. When under a strong magnetic field, Ec is independent of the device parameters and swells only near the Dirac point. Further, the dependence of Ec on EF can be scaled by EF/kBT , with a peak value of (2 ln2 ) kBT /e for the three-terminal system and (4/3 ln2 ) kBT /e for the four-terminal system. We also study the impact of disorder on the Ettingshausen effect. Regardless of the magnetic field strength, Ec is robust against moderate disorder scattering. In addition, in the strong magnetic field, Ec with additional regular oscillating structure can be caused by disorder.

  6. Bi-based 2223 superconducting polycrystalline materials prepared by either a solid state route or a glassy ‘matrix’ precursor method: Chemical analysis as well as electrical and thermal transport properties

    NASA Astrophysics Data System (ADS)

    Cloots, R.; Bougrine, H.; Houssa, M.; Stassen, S.; D'Urzo, L.; Rulmont, A.; Ausloos, M.

    1994-10-01

    Two routes have been followed in order to prepare Bi 1.7Pb 0.3Sr 2Ca 2Cu 3O y superconducting materials. Bi 1.7Pb 0.3CuO 4 is always used as one of the starting basic materials. The first route involves a new experimental procedure based on the solid state synthesis of separate intermediate phases, mixed together in a two (Bi 1.7Pb 0.3CuO 4+2SrCaCuO 3), three (Bi 1.7Pb 0.3CuO 4+2SrCuO 2+2CaCO 3) or four (Bi 1.7Pb 0.3CuO 4+ ( {1}/{12}) Sr 8Ca 6Cu 24O 41+( {3}/{2}X) CaCO 3+( {4}/{3})SrCO 3) powder process. Electric resistivity versus temperature measurements are presented. Even though the Tc(0) of each sample is above 100 K, X-ray diffraction shows that the main phase is the 2212 phase in each case. Relatively pure 2223 materials have, however, successfully been produced by the second method, which starts from a glassy intermediate phase and involves a so-called ‘matrix’ method. The glass precursor phase is composed of one (Bi 1.7Pb 0.3CuO 4), two (Bi 1.7Pb 0.3CuO 4+2CaCo 3), and three (Bi 1.7Pb 0.3CuO 4+( {3}/{2})CaCO 3+( {4}/{3})SrCO 3) components as for the solid state routes. The role of both the added alkaline earth crystalline compounds and the glass matrix precursors in this second method turns out to be very important. We propose a schematic structural model in order to explain the selectivity of the starting materials. SrCaCuO 3 is found to be a good precursor of the 2212 phase, while SrCuO 2 gives rise to the 2223 phase. It seems that the presence of CaCO 3 in the glassy intermediate phase, thus acting as a cation reservoir, is very useful for the production of the 2223 phase. Electric resistivity, thermal conductivity and thermopower versus temperature measurements are also presented and discussed in terms of intergrowths and variations of cationic compositions in the Bi-based layers.

  7. Electrical Transport of Long DNA Molecules on Liuid-Solid Interfaces

    NASA Astrophysics Data System (ADS)

    Samuilov, Vladimir; Seo, Young-Soo; Sokolov, Jonathan; Rafailovich, Miriam; Chu, Benjamin

    2002-03-01

    The electrical transport properties of long DNA molecules were studied based upon a newly developed method of electrophoresis on flat surfaces [1]. The electrophoretic mobilities of DNA in the presence of Si surface were found to be approximately one order less than in free solution. The electropherogram peaks of 1 kb- and Hind III DNA ladders have been clearly identified. The experimental dependencies of the mobilities on molecular weight were found to be scaled with power law with the exponents of an opposite sign at 2 different buffer concentrations: negative for surface transport at 10 -2 M concentration of TBE buffer and positive at 10 -3 M. A novel mechanism responsible for DNA molecules separation in the presence of the surface at low buffer concentrations has been developed. The multi-ion system is governed by the Nernst-Planck equations (ion movement due to convection, migration and diffusion), in combination with the Poisson-Boltzmann equation. The discrepancy from charge neutrality that occurs in the diffuse double layer very close to the substrate is the driving force for the Navier-Stokes equation, which finally results in a liquid movement very close to the surface that is denoted as electro-osmosis. The adsorbed DNA move due to the electrical field parallel to the surface, and also due the electro-osmotic convection that drags the DNA chains if they are only partly adsorbed. The electric double layer is responsible for a velocity profile of the electroosmotic flow. The net electrophoretic mobility of longer DNA, being trapped closer to the surface, is higher than of the shorter ones in the electric field, oriented along the surface. The main features of the electro-hydrodynamic instability related to λ and T2 DNA molecules aggregation, observed in our system, are consistent with our model. This work was supported by NSF-MRSEC Program. [1]. N. Pernodet, V. Samuilov, K. Shin, J. Sokolov, M.H. Rafailovich, D. Gersappe, B. Chu, DNA Electrophoresis on a

  8. Single-Crystal Silicon: Electrical and Optical Properties

    NASA Astrophysics Data System (ADS)

    Hava, Shlomo; Auslender, Mark

    Electrical and optical properties of crystalline semiconductors are important parts of pure physics and material science research. In addition, knowledge of parameters related to these properties, primarily for silicon and III-V semiconductors, has received a high priority in microelectronics and optoelectronics since the establishment of these industries. For control protocols, emphasis has recently been placed on novel optical measurement techniques, which have proved very promising as nondestructive and even non-contact methods. Earlier they required knowledge of the free-carrier-derived optical constants, related to the electrical conductivity at infrared frequencies, but interest in the optical constants of silicon in the visible, ultraviolet (UV) and soft-X-ray ranges has been revived since the critical dimensions in devices have become smaller.

  9. Electrical Properties of Polymer/Carbon Nanotube Blends

    NASA Astrophysics Data System (ADS)

    Salgado-Delgado, R.; Olarte-Paredes, A.; Vargas-Galarza, Z.; García-Hernández, E.; Salgado-Delgado, A. M.; Rubio-Rosas, E.; Campos-Álvarez, J.; Castaño, V. M.

    2016-10-01

    Electrical and morphological properties of a novel composite, consisting of polypyrrole (PPy)/carbon black (CB)/carbon nanotubes (CNT), within a polyethylene (PE) matrix, are reported. The electrical properties were studied according to the type of filler (i.e. PPy, CB or CNT). The resistivity, analyzed by the Van der Pauw method, shows values in the range of (1E+15 for PE to 1.07E-01 for M15) Ω cm. The filler is distributed as one phase within the blended matrix and/or at the interface between the polymers, thus producing a highly homogeneous material. The morphology and degree of dispersion of the PPy/CB/CNTs in the PE matrix at different concentrations were investigated by scanning electron microscopy.

  10. Electrical transport and magnetic properties of epitaxial Nd0.7 Sr0.3 MnO3 thin films on (001)-oriented LaAlO3 substrate

    NASA Astrophysics Data System (ADS)

    Gopalarao, T. R.; Ravi, S.; Pamu, D.

    2016-07-01

    Nd0.7 Sr0.3 MnO3 thin films were deposited using RF-magnetron sputtering on (001) oriented LaAlO3 substrate by varying thickness in the range of 12-200 nm. X-ray diffraction patterns of both air annealed and oxygen annealed films show epitaxial growth along (00l) orientation with decrease in lattice strain with increase in film thickness. Raman spectra show the presence of strong peaks corresponding to rotational and stretching modes of MnO6 octahedra and their intensity is found to decrease with increase in film thickness. Both air and oxygen annealed films except for 12 nm thickness exhibit ferromagnetic transition with a maximum TC of 200 K. The magnetic anisotropic constant was estimated from the analysis of M-H curve and its value is found to decrease with increase in film thickness. Metal-insulator transitions have been observed in all films including the 12 nm thick film. The electrical resistivity data in the metallic region, i.e. close to TMI, were analysed by considering electron-magnon scattering mechanism and in the low temperature region far below TMI; the analysis was carried out by considering the combination of electron-electron scattering and charge localisation effect. The resistivity data in the insulating region (T >TMI) were analysed by considering Mott-variable range hopping model.

  11. TRANSPORT

    EPA Science Inventory

    Presentation outline: transport principles, effective solubility; gasoline composition; and field examples (plume diving).
    Presentation conclusions: MTBE transport follows from - phyiscal and chemical properties and hydrology. Field examples show: MTBE plumes > benzene plu...

  12. Pressure dependence of thermal transport properties

    PubMed Central

    Hofmeister, Anne M.

    2007-01-01

    Pressure (P) derivatives of thermal conductivity (k) and thermal diffusivity (D) are important to geophysics but are difficult to measure accurately because minerals, being hard and partially transparent, likely incur systematic errors through thermal losses at interfaces and spurious radiative transfer. To evaluate accuracy, repeat experiments for olivine [(Mg0.9Fe0.1)2SiO4], quartz (SiO2), and NaCl are examined in detail: these and other data on electrical insulators are compared with theory. At ambient conditions, D is underestimated in proportion to the number of contacts. As temperature (T) increases, spurious radiative transfer more than offsets contact loss. Compression of pore space and contact losses affect pressure derivatives, but these seem independent of T. Accurate (±2%) values of D(T) at 1 atm are obtained with the contact-free, laser-flash method. Other optical techniques do not pinpoint D but provide useful pressure derivatives. Published data on ∂(lnk)/∂P at ambient conditions agree roughly with all available models, the simplest of which predicts ∂(lnk)/∂P ∼ ∂(lnKT)/∂P, where KT is the bulk modulus. However, derivatives verified by multiple measurements are reproduced accurately only by the damped harmonic oscillator model. An improved database is needed to refine this model and to confidently extrapolate these difficult measurements to geophysically relevant conditions. PMID:17299046

  13. Structure and Electrical Properties of an Assembly of Au Nanoclusters

    DTIC Science & Technology

    2001-01-01

    Nanoclusters DISTRIBUTION: Approved for public release, distribution unlimited This paper is part of the following report: TITLE: Materials Research...Materials Research Society Structure and Electrical Properties of an Assembly of Au Nanoclusters G. Muralidharan, L. Maya and T. Thundat Oak Ridge National...interest both for understanding the fundamental physics involved and for potential applications. In this study, we describe a technique for preparing

  14. Effect of gamma irradiation on electrical properties of Cu nanowires

    SciTech Connect

    Rana, Pallavi Gehlawat, Devender Chauhan, R. P.

    2014-04-24

    Metallic nanowires are of great interest due to their unique electrical, optical, chemical and magnetic properties. Characterization and explanations of electronic properties of nanowires are extremely important due to their potential applications in the field of nanoelectronics and optoelectronics. In the present study, we synthesized the copper nanowires of different diameters (80nm, 100nm and 200nm) and exposed them with gamma rays of 100 KGy and 150 KGy doses. The I-V characteristics of different diameter of Cu nanowires before and after the irradiation were recorded.

  15. Selected electrical properties of high ohmic thick-film resistors

    NASA Astrophysics Data System (ADS)

    DÄ browski, Arkadiusz; Tatar, Adam; Dziedzic, Andrzej

    2016-12-01

    Results of fabrication as well as electrical and stability characterization of thick-film high ohmic resistors are described in this paper. Five commercially available resistive compositions with sheet resistance of 1, 10, and 100 MΩ/sq were applied. The best properties were obtained for the lowest sheet resistance pastes, for which voltage coefficient of resistance (VCR) was lower than 3 ppm/V and hot temperature coefficient of resistance (HTCR) below 50 ppm/°C. Effect of resistor length on sheet resistance and impact of termination material were analyzed. High voltage pulse stress at 2 kV had negligible influence on resistors' properties.

  16. Computational rock physics: Transport properties in porous media and applications

    NASA Astrophysics Data System (ADS)

    Keehm, Youngseuk

    Earth sciences is undergoing a gradual but massive shift from descriptions of the earth and earth systems, toward process modeling, simulation, and process visualization. This shift is very challenging because the underlying physical and chemical processes are often nonlinear and coupled, and take place in strongly heterogeneous systems. An example is two-phase fluid flow in rocks: a nonlinear, coupled, and time-dependent problem in complex microgeometry. To understand these complex processes, the knowledge of the underlying pore-scale processes is essential. This work focuses on building transport process simulators in realistic pore microstructures. These pore-scale simulators will be modules of a computational rock physics framework with future acoustic, elastic, electrical and NMR property simulators. This computational environment can significantly complement the physical laboratory, with several distinct advantages: rigorous prediction of physical properties, interrelations among the physical properties, and simulation of dynamic problems with multiple physical responses. This dissertation is initiative for the computational rock physics framework---a quantitative model for coupled, nonlinear, transient and complex behavior of earth systems. A rigorous pore-scale simulation requires three important traits: reliability, efficiency, and the ability to handle complex microgeometry. We implemented single-phase and two-phase flow simulators using the Lattice-Boltzmann algorithm, since it handles very complex pore geometries without idealization of the pore space. The single-phase flow simulator successfully replicates fluid flow in a digital representation of real sandstone, and predicts permeability very accurately. Furthermore, two applications using the single-phase flow simulator are proposed: a permeability estimation technique from thin sections, and diagenesis modeling with fluid flow. These two applications show the potential applicability of this robust

  17. Transport properties of pyroclastic rocks from Montagne Pelée volcano (Martinique, Lesser Antilles)

    NASA Astrophysics Data System (ADS)

    Bernard, Marie-Lise; Zamora, Maria; GéRaud, Yves; Boudon, Georges

    2007-05-01

    The hydraulic and electrical properties of pyroclastic rocks have been investigated in laboratory on a representative sampling of Montagne Pelée (Martinique, France) deposits with renewed interest in geophysical applications. This sampling covers all the lithologic units of this volcano: lava dome and lava flows, pumices from ash-and-pumice fall and flow deposits, lava blocks from block-and-ash flow and Peléean "nuées ardentes" deposits, scoriae from scoria flow deposits. The connected porosity varies over a wide range from 3 to 62%. The unconnected porosity is important only on pumices where it can reach 15%. The permeability covers more than 5 orders of magnitude, ranging from 10-16 to 35 × 10-12 m2. The higher values are obtained on lava blocks and the scoriae, even if these rocks are less porous than the pumices. The formation factor ranges from 7 to 1139. The transport properties of these rocks are slightly correlated with porosity. This indicates that these properties are not only controlled by the connected porosity. To connect the transport properties to the textural characteristics of the pore network of pyroclastic rocks, different models, based on geometrical considerations or percolation theory, were tested. The pore access radius distribution and the tortuosity control the transport properties of pyroclastic rocks. Consequently, the models (electric and hydraulic) based on the concept of percolation (e.g., the models of Katz and Thompson), apply better than the equivalent channel model of Kozeny-Carman. In addition, the difference in transport properties observed on lava blocks and pumices confirms that the mechanisms of degassing and vesiculation are different for these two types of rock.

  18. Magnetic Resonance Based Electrical Properties Tomography: A Review

    PubMed Central

    Zhang, Xiaotong; Liu, Jiaen

    2014-01-01

    Frequency-dependent electrical properties (EPs; conductivity and permittivity) of biological tissues provide important diagnostic information (e.g. tumor characterization), and also play an important role in quantifying radiofrequency (RF) coil induced Specific Absorption Rate (SAR) which is a major safety concern in high- and ultrahigh-field Magnetic Resonance Imaging (MRI) applications. Cross-sectional imaging of EPs has been pursued for decades. Recently introduced Electrical Properties Tomography (EPT) approaches utilize the measurable RF magnetic field induced by the RF coil in an MRI system to quantitatively reconstruct the EP distribution in vivo and non-invasively with a spatial resolution of a few millimeters or less. This paper reviews the Electrical Properties Tomography approach from its basic theory in electromagnetism to the state of the art research outcomes. Emphasizing on the imaging reconstruction methods rather than experimentation techniques, we review the developed imaging algorithms, validation results in physical phantoms and biological tissues, as well as their applications in in vivo tumor detection and subject-specific SAR prediction. Challenges for future research are also discussed. PMID:24803104

  19. Transport properties of high-temperature Jupiter atmosphere components

    SciTech Connect

    Bruno, D.; Colonna, G.; De Pascale, O.; Laricchiuta, A.; Catalfamo, C.; Diomede, P.; Capitelli, M.; Gorse, C.; Longo, S.; Giordano, D.; Pirani, F.

    2010-11-15

    Transport properties of high-temperature helium and hydrogen plasmas as well as Jupiter atmosphere have been calculated for equilibrium and nonequilibrium conditions using higher approximations of the Chapman-Enskog method. A complete database of transport cross sections for relevant interactions has been derived, including minority species, by using both ab initio and phenomenological potentials. Inelastic collision integrals terms, due to resonant charge-exchange channels, have been also considered.

  20. Metal nanoparticle fluids with magnetically induced electrical switching properties

    NASA Astrophysics Data System (ADS)

    Kim, Younghoon; Cho, Jinhan

    2013-05-01

    We report the successful preparation of solvent-free metal nanoparticle (NP) fluids with multiple-functionalities, such as rheological properties, magnetism, ionic conductivity, and electrical properties, allowing for facile synthesis and mass production. The gold nanoparticles (AuNPs) used in this study were synthesized using tetraoctylammonium bromide (TOABr) in toluene and then directly phase-transferred to solvent-free low-molecular-weight (Mw) imidazolium-type ionic liquid media containing thiol groups (i.e., IL-SH). Magnetic metal fluids (i.e., MIL-SH-AuNPs) were prepared by the addition of FeCl3 powder to metal fluids (i.e., IL-SH-AuNPs). These fluids showed relatively high ionic and electrical conductivities compared with those of conventional metal NP fluids based on organic ILs with high Mw. Furthermore, it was demonstrated that these fluids could be used as electric switches operated using an external magnetic field in organic media.We report the successful preparation of solvent-free metal nanoparticle (NP) fluids with multiple-functionalities, such as rheological properties, magnetism, ionic conductivity, and electrical properties, allowing for facile synthesis and mass production. The gold nanoparticles (AuNPs) used in this study were synthesized using tetraoctylammonium bromide (TOABr) in toluene and then directly phase-transferred to solvent-free low-molecular-weight (Mw) imidazolium-type ionic liquid media containing thiol groups (i.e., IL-SH). Magnetic metal fluids (i.e., MIL-SH-AuNPs) were prepared by the addition of FeCl3 powder to metal fluids (i.e., IL-SH-AuNPs). These fluids showed relatively high ionic and electrical conductivities compared with those of conventional metal NP fluids based on organic ILs with high Mw. Furthermore, it was demonstrated that these fluids could be used as electric switches operated using an external magnetic field in organic media. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00653k

  1. Transport properties of interacting magnetic islands in tokamak plasmas

    SciTech Connect

    Gianakon, T.A.; Callen, J.D.; Hegna, C.C.

    1993-10-01

    This paper explores the equilibrium and transient transport properties of a mixed magnetic topology model for tokamak equilibria. The magnetic topology is composed of a discrete set of mostly non-overlapping magnetic islands centered on the low-order rational surfaces. Transport across the island regions is fast due to parallel transport along the stochastic magnetic field lines about the separatrix of each island. Transport between island regions is assumed to be slow due to a low residual cross-field transport. In equilibrium, such a model leads to: a nonlinear dependence of the heat flux on the pressure gradient; a power balance diffusion coefficient which increases from core to edge; and profile resiliency. Transiently, such a model also exhibits a heat pulse diffusion coefficient larger than the power balance diffusion coefficient.

  2. Transport properties in nontwist area-preserving maps

    DOE PAGES

    Szezech Jr., J. D.; Caldas, I. L.; Lopes, S. R.; ...

    2009-10-23

    Nontwist systems, common in the dynamical descriptions of fluids and plasmas, possess a shearless curve with a concomitant transport barrier that eliminates or reduces chaotic transport, even after its breakdown. In order to investigate the transport properties of nontwist systems, we analyze the barrier escape time and barrier transmissivity for the standard nontwist map, a paradigm of such systems. We interpret the sensitive dependence of these quantities upon map parameters by investigating chaotic orbit stickiness and the associated role played by the dominant crossing of stable and unstable manifolds.

  3. Recovery Act - Sustainable Transportation: Advanced Electric Drive Vehicle Education Program

    SciTech Connect

    Caille, Gary

    2013-12-13

    The collective goals of this effort include: 1) reach all facets of this society with education regarding electric vehicles (EV) and plug–in hybrid electric vehicles (PHEV), 2) prepare a workforce to service these advanced vehicles, 3) create web–based learning at an unparalleled level, 4) educate secondary school students to prepare for their future and 5) train the next generation of professional engineers regarding electric vehicles. The Team provided an integrated approach combining secondary schools, community colleges, four–year colleges and community outreach to provide a consistent message (Figure 1). Colorado State University Ventures (CSUV), as the prime contractor, plays a key program management and co–ordination role. CSUV is an affiliate of Colorado State University (CSU) and is a separate 501(c)(3) company. The Team consists of CSUV acting as the prime contractor subcontracted to Arapahoe Community College (ACC), CSU, Motion Reality Inc. (MRI), Georgia Institute of Technology (Georgia Tech) and Ricardo. Collaborators are Douglas County Educational Foundation/School District and Gooru (www.goorulearning.org), a nonprofit web–based learning resource and Google spin–off.

  4. Electrical Treeing Induced Vascular Networks for Fluid Transport

    NASA Astrophysics Data System (ADS)

    Behler, Kristopher; Wetzel, Eric

    2010-03-01

    Electrical treeing (ET) is a stepwise dielectric breakdown process in which partial discharges in a dielectric material generate a branched hollow network of tubules between the electrode and the ground. Overtime, exposure of dielectric materials to global electric fields which are lower than the dielectric strength results in electrical trees (ETs). This dielectric breakdown is exploited to induce a controlled growth of ETs in epoxies to demonstrate a fabrication technique of synthetic vascular systems in engineering materials. Both AC, ±20 kV at 100 Hz sine wave, and DC, up to -60 kV, voltages were used to grow ET in planar and volumetric systems. AC treeing induces a more bush-like highly branched structure, whereas DC treeing results in a more tree-like structure possessing mostly low ordered branches. In addition to voltage, the geometric arrangement of the electrode and ground, and the use of electrode surface treatments with multi-walled carbon nanotubes (MWCNTs) were investigated. Applications for vascular networks were demonstrated by filling the ETs with dyed liquids.

  5. Emissions of greenhouse gases from the use of transportation fuels and electricity. Volume 1, Main text

    SciTech Connect

    DeLuchi, M.A.

    1991-11-01

    This report presents estimates of full fuel-cycle emissions of greenhouse gases from using transportation fuels and electricity. The data cover emissions of carbon dioxide (CO{sub 2}), methane, carbon monoxide, nitrous oxide, nitrogen oxides, and nonmethane organic compounds resulting from the end use of fuels, compression or liquefaction of gaseous transportation fuels, fuel distribution, fuel production, feedstock transport, feedstock recovery, manufacture of motor vehicles, maintenance of transportation systems, manufacture of materials used in major energy facilities, and changes in land use that result from using biomass-derived fuels. The results for electricity use are in grams of CO{sub 2}-equivalent emissions per kilowatt-hour of electricity delivered to end users and cover generating plants powered by coal, oil, natural gas, methanol, biomass, and nuclear energy. The transportation analysis compares CO{sub 2}-equivalent emissions, in grams per mile, from base-case gasoline and diesel fuel cycles with emissions from these alternative- fuel cycles: methanol from coal, natural gas, or wood; compressed or liquefied natural gas; synthetic natural gas from wood; ethanol from corn or wood; liquefied petroleum gas from oil or natural gas; hydrogen from nuclear or solar power; electricity from coal, uranium, oil, natural gas, biomass, or solar energy, used in battery-powered electric vehicles; and hydrogen and methanol used in fuel-cell vehicles.

  6. Emissions of greenhouse gases from the use of transportation fuels and electricity

    SciTech Connect

    DeLuchi, M.A. )

    1991-11-01

    This report presents estimates of full fuel-cycle emissions of greenhouse gases from using transportation fuels and electricity. The data cover emissions of carbon dioxide (CO{sub 2}), methane, carbon monoxide, nitrous oxide, nitrogen oxides, and nonmethane organic compounds resulting from the end use of fuels, compression or liquefaction of gaseous transportation fuels, fuel distribution, fuel production, feedstock transport, feedstock recovery, manufacture of motor vehicles, maintenance of transportation systems, manufacture of materials used in major energy facilities, and changes in land use that result from using biomass-derived fuels. The results for electricity use are in grams of CO{sub 2}-equivalent emissions per kilowatt-hour of electricity delivered to end users and cover generating plants powered by coal, oil, natural gas, methanol, biomass, and nuclear energy. The transportation analysis compares CO{sub 2}-equivalent emissions, in grams per mile, from base-case gasoline and diesel fuel cycles with emissions from these alternative- fuel cycles: methanol from coal, natural gas, or wood; compressed or liquefied natural gas; synthetic natural gas from wood; ethanol from corn or wood; liquefied petroleum gas from oil or natural gas; hydrogen from nuclear or solar power; electricity from coal, uranium, oil, natural gas, biomass, or solar energy, used in battery-powered electric vehicles; and hydrogen and methanol used in fuel-cell vehicles.

  7. Theoretical studies of the transport properties in compound semiconductors

    NASA Technical Reports Server (NTRS)

    Segall, Benjamin

    1994-01-01

    This final report is an overview of the work done on Cooperative Agreement NCC 3-55 with the Solid State Technology Branch of the NASA-Lewis Research Center (LeRC). Over the period of time that the agreement was in effect, the principal investigator and, in the last three years, the co-principal investigator worked on a significant number of projects and interacted with members of the Solid State Technology (SST) branch in a number of different ways. For the purpose of this report, these efforts will be divided into five categories: 1) work directly with experimental electrical transport studies conducted by members of the SST branch; 2) theoretical work on electrical transport in compound semiconductors; 3) electronic structure calculations which are relevant to the electrical transport in polytypes of SiC and SiC-AlN alloys; 4) the electronic structure calculations of polar interfaces; and 5) consultative and supportive activities related to experiments and other studies carried out by SST branch members. Work in these categories is briefly discussed.

  8. Measurement of the radiative transport properties of reticulated alumina foams

    SciTech Connect

    Hale, M.J.; Bohn, M.S.

    1992-12-01

    This paper presents a method for determining radiative transport properties of reticulated materials. The method has both experimental and analytical components. A polar nephelometer is used to measure the scattering profile of a sample of the reticulated material. The results of a Monte Carlo simulation of the experiment are then combined with the experimental results to give the scatter albedo and extinction coefficient. This paper presents the results of using this method to determine the radiative transport properties of four different porosities (10, 20, 30, 65 pores per inch) of cylindrical reticulated alumina samples ranging in thickness form 0.5 inches to 2. 5 inches.

  9. Effect of A-site ionic size variation on TCR and electrical transport properties of (Nd0.7-xLax)0.7Sr0.3MnO3 with x = 0, 0.1 and 0.2

    NASA Astrophysics Data System (ADS)

    Vadnala, Sudarshan; Asthana, Saket; Pal, Prem; Srinath, S.

    2015-02-01

    In this work, the structural and transport properties of (Nd0.7-xLax)0.7Sr0.3MnO3 manganites with x = 0, 0.1 and 0.2 prepared by solid state reaction route are studied. These compounds are found to be crystallized in orthorhombic structural form. Experimental results showing a shift in the metal to semiconductor/insulator transition temperature (TMI) towards room temperature (289 K) with the substitution of Nd by La, as the value of x is varied in the sequence (0,0.1,0.2), have been provided. The shift in the TMI, from 239 K (for x=0) to near the room temperature 289 K (for x=0.2), is attributed to the fact that the average radius of site-A increases with the percentage of La. The maximum temperature coefficients of resistance (TCR) of (Nd0.7-xLax)0.7Sr0.3MnO3 (x= 0.1 and 0.2) are found to be higher compared to its parent compound Nd0.7Sr0.3MnO3. The electrical transport mechanisms for (Nd0.7-xLax)0.7Sr0.3MnO3 (x= 0 to 0.2) are explored by using different theoretical models, for temperatures below and above TMI. An appropriate enlightenment for the observed behavior is discussed in detail.

  10. Electrical and Thermal Transport in Coplanar Polycrystalline Graphene-hBN Heterostructures.

    PubMed

    Barrios-Vargas, José Eduardo; Mortazavi, Bohayra; Cummings, Aron W; Martinez-Gordillo, Rafael; Pruneda, Miguel; Colombo, Luciano; Rabczuk, Timon; Roche, Stephan

    2017-03-08

    We present a theoretical study of electronic and thermal transport in polycrystalline heterostructures combining graphene (G) and hexagonal boron nitride (hBN) grains of varying size and distribution. By increasing the hBN grain density from a few percent to 100%, the system evolves from a good conductor to an insulator, with the mobility dropping by orders of magnitude and the sheet resistance reaching the MΩ regime. The Seebeck coefficient is suppressed above 40% mixing, while the thermal conductivity of polycrystalline hBN is found to be on the order of 30-120 Wm(-1) K(-1). These results, agreeing with available experimental data, provide guidelines for tuning G-hBN properties in the context of two-dimensional materials engineering. In particular, while we proved that both electrical and thermal properties are largely affected by morphological features (e.g., by the grain size and composition), we find in all cases that nanometer-sized polycrystalline G-hBN heterostructures are not good thermoelectric materials.

  11. Effects of crystal phase mixing on the electrical properties of InAs nanowires.

    PubMed

    Thelander, Claes; Caroff, Philippe; Plissard, Sébastien; Dey, Anil W; Dick, Kimberly A

    2011-06-08

    We report a systematic study of the relationship between crystal quality and electrical properties of InAs nanowires grown by MOVPE and MBE, with crystal structure varying from wurtzite to zinc blende. We find that mixtures of these phases can exhibit up to 2 orders of magnitude higher resistivity than single-phase nanowires, with a temperature-activated transport mechanism. However, it is also found that defects in the form of stacking faults and twin planes do not significantly affect the resistivity. These findings are important for nanowire-based devices, where uncontrolled formation of particular polytype mixtures may lead to unacceptable device variability.

  12. Thermophysical Properties of Liquid Te: Density, Electrical Conductivity, and Viscosity

    NASA Technical Reports Server (NTRS)

    Li, C.; Su, C.; Lehoczky, S. L.; Scripa, R. N.; Ban, H.; Lin, B.

    2004-01-01

    The thermophysical properties of liquid Te, namely, density, electrical conductivity, and viscosity, were determined using the pycnometric and transient torque methods from the melting point of Te (723 K) to approximately 1150 K. A maximum was observed in the density of liquid Te as the temperature was increased. The electrical conductivity of liquid Te increased to a constant value of 2.89 x 10(exp 5 OMEGA-1m-1) as the temperature was raised above 1000 K. The viscosity decreased rapidly upon heating the liquid to elevated temperatures. The anomalous behaviors of the measured properties are explained as caused by the structural transitions in the liquid and discussed in terms of Eyring's and Bachiskii's predicted behaviors for homogeneous liquids. The Properties were also measured as a function of time after the liquid was coded from approximately 1173 or 1123 to 823 K. No relaxation phenomena were observed in the properties after the temperature of liquid Te was decreased to 823 K, in contrast to the relaxation behavior observed for some of the Te compounds.

  13. Crystal Growth, Electrical, and Magnetic Properties of Niobium Phosphate Bronze: Na 2+ xP 4Nb 6O 26

    NASA Astrophysics Data System (ADS)

    Xu, J.; Greenblatt, M.

    1996-02-01

    Large single crystals of the bronze Na2+xP4Nb6O26were grown by chemical vapor transport technique with either NH4Cl or NaCl as the transporting agent. The directional electrical transport properties along the three orthorhombic crystallographic axes show anisotropic semiconducting behavior with the activation energies of 0.13, 0.15, and 0.12 eV forEa,Eb, andEc, respectively. Magnetic susceptibility measurements indicate Curie-Weiss behavior with μeff= 1.14 μB/Nb4+.

  14. Electrical properties of single CuO nanowires for device fabrication: Diodes and field effect transistors

    SciTech Connect

    Florica, Camelia; Costas, Andreea; Boni, Andra Georgia; Negrea, Raluca; Preda, Nicoleta E-mail: encu@infim.ro; Pintilie, Lucian; Enculescu, Ionut E-mail: encu@infim.ro; Ion, Lucian

    2015-06-01

    High aspect ratio CuO nanowires are synthesized by a simple and scalable method, thermal oxidation in air. The structural, morphological, optical, and electrical properties of the semiconducting nanowires were studied. Au-Ti/CuO nanowire and Pt/CuO nanowire electrical contacts were investigated. A dominant Schottky mechanism was evidenced in the Au-Ti/CuO nanowire junction and an ohmic behavior was observed for the Pt/CuO nanowire junction. The Pt/CuO nanowire/Pt structure allows the measurements of the intrinsic transport properties of the single CuO nanowires. It was found that an activation mechanism describes the behavior at higher temperatures, while a nearest neighbor hopping transport mechanism is characteristic at low temperatures. This was also confirmed by four-probe resistivity measurements on the single CuO nanowires. By changing the metal/semiconductor interface, devices such as Schottky diodes and field effect transistors based on single CuO p-type nanowire semiconductor channel are obtained. These devices are suitable for being used in various electronic circuits where their size related properties can be exploited.

  15. Electronic contributions to linear and nonlinear electric properties in fullerene-based molecular systems

    NASA Astrophysics Data System (ADS)

    Skwara, B.; Loboda, O.; Avramopoulos, A.; Luis, J.-M.; Reis, H.; Papadopoulos, M. G.

    2012-12-01

    Recent studies of the linear and nonlinear electric properties of various fullerene-based subsystems are reviewed. The electric properties of derivatives of C60 fullerene with carbazole, benzothiazole, benzothiazole-triphenyloamine and free-base porphyrin substituents at different levels of theory are summarized. In addition, the electronic and vibrational electric properties of endohedral Sc2@C72 system are reported.

  16. Electric heating for high-temperature heat transport fluids

    NASA Astrophysics Data System (ADS)

    Holmes, J. T.

    1985-12-01

    Recent experiences with electric resistance heaters at the solar Central Receiver Test Facility are described. These heaters are used to preheat or maintain equipment used with molten nitrate salt or liquid sodium heat transfer fluids. Results of extensive testing performed to improve the reliability of similar heating systems used in the development program for the sodium-cooled liquid metal fast breeder nuclear reactor are also reviewed. Recommendations are made for increasing the reliability of trace heating systems for high-melting-point heat transfer fluids including thermal design, heating element selection, installation, insulation, and controls.

  17. Electrical-driven transport of endohedral fullerene encapsulating a single water molecule.

    PubMed

    Xu, Baoxing; Chen, Xi

    2013-04-12

    Encapsulating a single water molecule inside an endohedral fullerene provides an opportunity for manipulating the H2O@C60 through the encapsulated polar H2O molecule. Using molecular dynamic simulations, we propose a strategy of electrical-driven transport of H2O@C60 inside a channel, underpinned by the unique behavior of a water molecule free from a hydrogen-bonding environment. When an external electrical field is applied along the channel's axial direction, steady-state transport of H2O@C60 can be reached. The transport direction and rate depend on the applied electrical intensity as well as the polar orientation of the encapsulated H2O molecule.

  18. Decoupling Mechanical and Ion Transport Properties in Polymer Electrolyte Membranes

    NASA Astrophysics Data System (ADS)

    McIntosh, Lucas D.

    Polymer electrolytes are mixtures of a polar polymer and salt, in which the polymer replaces small molecule solvents and provides a dielectric medium so that ions can dissociate and migrate under the influence of an external electric field. Beginning in the 1970s, research in polymer electrolytes has been primarily motivated by their promise to advance electrochemical energy storage and conversion devices, such as lithium ion batteries, flexible organic solar cells, and anhydrous fuel cells. In particular, polymer electrolyte membranes (PEMs) can improve both safety and energy density by eliminating small molecule, volatile solvents and enabling an all-solid-state design of electrochemical cells. The outstanding challenge in the field of polymer electrolytes is to maximize ionic conductivity while simultaneously addressing orthogonal mechanical properties, such as modulus, fracture toughness, or high temperature creep resistance. The crux of the challenge is that flexible, polar polymers best-suited for polymer electrolytes (e.g., poly(ethylene oxide)) offer little in the way of mechanical robustness. Similarly, polymers typically associated with superior mechanical performance (e.g., poly(methyl methacrylate)) slow ion transport due to their glassy polymer matrix. The design strategy is therefore to employ structured electrolytes that exhibit distinct conducting and mechanically robust phases on length scales of tens of nanometers. This thesis reports a remarkably simple, yet versatile synthetic strategy---termed polymerization-induced phase separation, or PIPS---to prepare PEMs exhibiting an unprecedented combination of both high conductivity and high modulus. This performance is enabled by co-continuous, isotropic networks of poly(ethylene oxide)/ionic liquid and highly crosslinked polystyrene. A suite of in situ, time-resolved experiments were performed to investigate the mechanism by which this network morphology forms, and it appears to be tied to the

  19. EMERGING TECHNOLOGY SUMMARY: THEORETICAL AND EXPERIMENTAL MODELING OF MULTI-SPECIES TRANSPORT IN SOILS UNDER ELECTRIC FIELDS

    EPA Science Inventory

    This project investigated an innovative approach for transport of inorganic species under the influence of electric fields. This process, commonly known as electrokinetics uses low-level direct current (dc) electrical potential difference across a soil mass applied through inert...

  20. Survey and assessment of electric and magnetic field (EMF) public exposure in the transportation environment

    SciTech Connect

    Dietrich, F.M.; Jacobs, W.L.

    1999-03-01

    This research, conducted under the support of the Federal Electric and Magnetic Field Research and Public Information Dissemination (EMF RAPID) Engineering Program, characterized the extreme-low-frequency (ELF) electric and magnetic fields (EMF) which a traveler might encounter while using various forms of transportation. Extensive measurement of field level, frequency, temporal variability and spatial variability are reported for: conventional internal-combustion cars, trucks and buses; electric cars, trucks and buses; commuter trains; ferry boats; jetliners; airport shuttle trams; and escalators and moving sidewalks. Static magnetic field levels are also reported. Where possible, the source of the fields is identified. This effort extends extensive past work which investigated field in electrified trains, subways, light rail vehicles, and a magnetically levitated train by using similar protocols to characterize the complex ELF (3 Hz to 3000 Hz) electric and magnetic fields found in virtually all transportation systems.

  1. Transport and dielectric properties of dense ionized matter from the average-atom RESEOS model

    NASA Astrophysics Data System (ADS)

    Ovechkin, A. A.; Loboda, P. A.; Falkov, A. L.

    2016-09-01

    Electron transport properties of warm and hot dense matter are calculated using two versions of the average-atom approach: Liberman's model and the neutral Wigner-Seitz-sphere model. Electrical conductivity calculations employed the extended Ziman formula, the relaxation-time approximation, the Zubarev method, and the Kubo-Greenwood formula. Thermal conductivities were evaluated in the relaxation-time approximation. The results obtained are in good agreement with experimental data and ab initio calculations. The origin of nonphysical features appearing in the DC electrical and thermal conductivities calculated with the relaxation-time approximation and the Zubarev method is analyzed. AC conductivity and dielectric properties of dense ionized matter are obtained from the radiative opacity data calculated using the RESEOS model.

  2. Seismic properties of volcanic rocks from Montagne Pelée (Martinique, Lesser Antilles) and their relations to transport properties

    NASA Astrophysics Data System (ADS)

    Bernard, M.-L.; Zamora, M.

    2012-04-01

    Numerous laboratory and theoretical studies on the physical properties of rocks and their relationships - lead mainly in the framework of petroleum exploration - show that rock physics is necessary for an accurate quantitative interpretation of geophysical observations. Moreover joint inversion of different geophysical datasets is emerging as an important tool to enhance resolution and decrease inversion artifacts in imaging of structurally complex areas such as volcanoes. In many cases, the coupling between the inverted parameters is based on empirical or theoretical relationships derived from laboratory data. Consequently rock physics can be used to: interpret simultaneously several geophysical datasets on volcanoes when they are available, improve the imaging of volcano structures, and better understand the coupled processes that can occur during volcanic unrest. It's in this context that we lead a laboratory study on the transport properties (permeability, thermal and electrical conductivities) and seismic properties (velocity and attenuation of P and S waves) of volcanic rocks representative of Montagne Pelée (Martinique) deposits. In this presentation we will focus on (1) the seismic properties and (2) the relations between seismic and transport properties. The 43 samples collected are representative of the main lithological units of this volcano: vesicular lava blocks and indurated ashed from indurated block-and-ash flows also called breccias, vesicular lava blocks from "Pelean nuee ardente" flows, scoriae from scoria flows, pumices from ash-and-pumices flows, and dense lava blocks from lava flows and lava domes. Their total porosity varies over a wide range from 4 to 73%. Since the samples present similar chemical and mineralogical compositions (andesites), the main difference between the samples comes from their pore structure and reflects differences in the mechanisms of magma degassing and vesiculation during their formation (Bernard et al., 2007). This

  3. Electrical transport studies of Ag nanoclusters embedded in glass matrix

    NASA Astrophysics Data System (ADS)

    Magudapathy, P.; Gangopadhyay, P.; Panigrahi, B. K.; Nair, K. G. M.; Dhara, S.

    2001-05-01

    Silver nanoclusters embedded in glass matrices have been obtained by the combined use of ion exchange and subsequent ion implantation. XRD and UV-visible spectro-photometric analysis have confirmed the formation of Ag nano-clusters in the ion-irradiated samples. Temperature-dependent resistivity measurements of the irradiated samples have been found to follow ρ( T)∝exp√( T0/ T) in the temperature range of 80-280 K. The observed behaviour of ρ( T) is consistent with charge transport due to hopping between isolated, conducting islands. The separation distance between the conducting islands has been found to be a function of fluence.

  4. Electrical properties of strontium doped yttrium manganite oxide

    NASA Astrophysics Data System (ADS)

    Thakur, Rajesh K.; Thakur, Rasna; Kaurav, N.; Okram, G. S.; Gaur, N. K.

    2013-02-01

    Powders of Y1-xSrxMnO3 (x = 0.1 and 0.2) pervoskites were obtained by using conventional solid state reaction method and their electrical properties are carefully analyzed. The XRD pattern showed the pointed peaks which correspond to the hexagonal structure of the reported compounds with space group P63cm (25-1079). The resistivity versus temperature plot infers a semiconducting like behavior in both reported compounds. The suppression in the resistivity has been witnessed with increasing concentration Sr2+ ions at yttrium site. The small polaron hopping conductivity model adequately describes the electrical conductivity behavior. The activation energy (Ea) is found to decrease as the 'x' (Sr content) increases.

  5. Electrical properties of individual ZnO nanowires.

    PubMed

    Sakurai, M; Wang, Y G; Uemura, T; Aono, M

    2009-04-15

    The electrical properties of individual ZnO nanowires were investigated for two methods of fabricating nanowire-electrode junctions. The number of carriers in the nanowires was increased by electrostatically doping them by applying a gate voltage. The nanowires were chemically doped by introducing impurities during growth. The Ga-doped nanowires had a linear current-voltage relationship over a wide voltage region. The nanowire-electrode junctions were formed either by using lithography to form electrodes on the nanowire or by using an AFM probe to move a nanowire onto prepared electrodes. With both methods, electrodes made of Ga-doped ZnO were found to make better electrical contact with the nanowire than those made of Ti/Au.

  6. Preparation and Electrical Property of Polypyrrole-Polyethylene Composite

    NASA Astrophysics Data System (ADS)

    Yoshino, Katsumi; Yin, Xiao Hong; Morita, Shigenori; Nakanishi, Yutaka; Nakagawa, Shinichi; Yamamoto, Hideo; Watanuki, Toshiro; Isa, Isao

    1993-02-01

    Polypyrrole-polyethylene composites have been prepared by pressing the mixture of polypyrrole coated and non-coated polyethylene spheres. Electrical conductivity is enhanced by more than 16 orders of magnitude and its activation energy decreases remarkably at concentration of polypyrrole coated polyethylene above around 10-20%, which corresponds to effective polypyrrole concentration of 0.1-0.2%. These characteristics can be explained by a percolation model. That is, at this concentration electrodes are bridged by conducting channel of doped polypyrrole. Thermoelectric power increases in proportion to absolute temperature and is independent on concentration of polypyrrole coated polyethylene sphere above 30%, which support the percolation model. The electrical property of this polypyrrole-polyethylene composite is found to be stable up to 160°C. The application of this composite to the semiconducting layer of a cable has been proposed.

  7. Transport in Halobacterium Halobium: Light-Induced Cation-Gradients, Amino Acid Transport Kinetics, and Properties of Transport Carriers

    NASA Technical Reports Server (NTRS)

    Lanyi, Janos K.

    1977-01-01

    Cell envelope vesicles prepared from H. halobium contain bacteriorhodopsin and upon illumination protons are ejected. Coupled to the proton motive force is the efflux of Na(+). Measurements of Na-22 flux, exterior pH change, and membrane potential, Delta(psi) (with the dye 3,3'-dipentyloxadicarbocyanine) indicate that the means of Na(+) transport is sodium/proton exchange. The kinetics of the pH changes and other evidence suggests that the antiport is electrogenic (H(+)/Na(++ greater than 1). The resulting large chemical gradient for Na(+) (outside much greater than inside), as well as the membrane potential, will drive the transport of 18 amino acids. The I9th, glutamate, is unique in that its accumulation is indifferent to Delta(psi): this amino acid is transported only when a chemical gradient for Na(+) is present. Thus, when more and more NaCl is included in the vesicles glutamate transport proceeds with longer and longer lags. After illumination the gradient of H+() collapses within 1 min, while the large Na(+) gradient and glutamate transporting activity persists for 10- 15 min, indicating that proton motive force is not necessary for transport. A chemical gradient of Na(+), arranged by suspending vesicles loaded with KCl in NaCl, drives glutamate transport in the dark without other sources of energy, with V(sub max) and K(sub m) comparable to light-induced transport. These and other lines of evidence suggest that the transport of glutamate is facilitated by symport with Na(+), in an electrically neutral fashion, so that only the chemical component of the Na(+) gradient is a driving force.

  8. Transport Properties of Metallic Ruthenates: A DFT +DMFT Investigation

    NASA Astrophysics Data System (ADS)

    Deng, Xiaoyu; Haule, Kristjan; Kotliar, Gabriel

    2016-06-01

    We present a systematical theoretical study on the transport properties of an archetypal family of Hund's metals, Sr2RuO4 , Sr3 Ru2 O7 , SrRuO3 , and CaRuO3 , within the combination of first principles density functional theory and dynamical mean field theory. The agreement between theory and experiments for optical conductivity and resistivity is good, which indicates that electron-electron scattering dominates the transport of ruthenates. We demonstrate that in the single-site dynamical mean field approach the transport properties of Hund's metals fall into the scenario of "resilient quasiparticles." We explain why the single layered compound Sr2 RuO4 has a relative weak correlation with respect to its siblings, which corroborates its good metallicity.

  9. Technological Support of Critical Parts for Railway Transport Working Properties

    NASA Astrophysics Data System (ADS)

    Gabets, A. V.; Gabets, D. A.; Markov, A. M.; Radchenko, M. V.; Leonov, S. L.

    2017-01-01

    The materials of complex research of operational properties of a new brand cast iron CHMN-35M. Optimal chemical composition was determined. The obtained results allow to conclude about possibility of its use for the manufacture of critical parts of rolling stock of railway transport, in particular of a side bearing cap

  10. Reference Fluid Thermodynamic and Transport Properties Database (REFPROP)

    National Institute of Standards and Technology Data Gateway

    SRD 23 NIST Reference Fluid Thermodynamic and Transport Properties Database (REFPROP) (PC database for purchase)   NIST 23 contains revised data in a Windows version of the database, including 105 pure fluids and allowing mixtures of up to 20 components. The fluids include the environmentally acceptable HFCs, traditional HFCs and CFCs and 'natural' refrigerants like ammonia

  11. Hybrid-Electric and Distributed Propulsion Technologies for Large Commercial Transports: A NASA Perspective

    NASA Technical Reports Server (NTRS)

    Madavan, Nateri K.; Del Rosario, Ruben; Jankovsky, Amy L.

    2015-01-01

    Develop and demonstrate technologies that will revolutionize commercial transport aircraft propulsion and accelerate development of all-electric aircraft architectures. Enable radically different propulsion systems that can meet national environmental and fuel burn reduction goals for subsonic commercial aircraft. Focus on future large regional jets and single-aisle twin (Boeing 737- class) aircraft for greatest impact on fuel burn, noise and emissions. Research horizon is long-term but with periodic spinoff of technologies for introduction in aircraft with more- and all-electric architectures. Research aligned with new NASA Aeronautics strategic R&T thrusts in areas of transition to low-carbon propulsion and ultra-efficient commercial transports.

  12. Electrical properties of methane hydrate + sediment mixtures

    USGS Publications Warehouse

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

    2015-01-01

    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.

  13. Irradiation response of commercial, high-Tc superconducting tapes: Electromagnetic transport properties

    DOE PAGES

    Gapud, A. A.; Greenwood, N. T.; Alexander, J. A.; ...

    2015-07-01

    Effects of low dose irradiation on the electrical transport current properties of commercially available high-temperature superconducting, coated-conductor tapes were investigated, in view of potential applications in the irradiative environment of fusion reactors. Three different tapes, each with unique as-grown flux-pinning structures, were irradiated with Au and Ni ions at energies that provide a range of damage effects, with accumulated damage levels near that expected for conductors in a fusion reactor environment. Measurements using transport current determined the pre- and post-irradiation resistivity, critical current density, and pinning force density, yielding critical temperatures, irreversibility lines, and inferred vortex creep rates. Results showmore » that at the irradiation damage levels tested, any detriment to as-grown pre-irradiation properties is modest; indeed in one case already-superior pinning forces are enhanced, leading to higher critical currents.« less

  14. Transport, Structural and Mechanical Properties of Quaternary FeVTiAl Alloy

    NASA Astrophysics Data System (ADS)

    Bhat, Tahir Mohiuddin; Gupta, Dinesh C.

    2016-11-01

    The electronic, structural, magnetic and transport properties of FeVTiAl quaternary alloy have been investigated within the framework of density functional theory. The material is a completely spin-polarized half-metallic ferromagnet in its ground state with F-43m structure. The structural stability was further confirmed by elastic constants in the cubic phase with high Young's modulus and brittle nature. The present study predicts an energy band gap of 0.72 eV in a localized minority spin channel at equilibrium lattice parameter of 6.00 Å. The transport properties of the material are discussed based on the Seebeck coefficient, and electrical and thermal conductivity coefficients. The alloy presents large values of Seebeck coefficients, ~39 μV K-1 at room temperature (300 K), and has an excellent thermoelectric performance with ZT = ~0.8.

  15. Transport properties of Nd1-xFexOF polycrystalline films

    NASA Astrophysics Data System (ADS)

    Corrales-Mendoza, I.; Rangel-Kuoppa, Victor-Tapio; Conde-Gallardo, A.

    2013-12-01

    The transport properties of Nd1-xFexOF films with 0.2electrical conductivity indicates that the transport properties are not governed by a typical band conduction mechanism but by a variable range hopping process.

  16. Irradiation response of commercial, high-Tc superconducting tapes: Electromagnetic transport properties

    SciTech Connect

    Gapud, A. A.; Greenwood, N. T.; Alexander, J. A.; Khan, A.; Leonard, K. J.; Aytug, T.; List III, F. A.; Rupich, M. W.; Zhang, Y.

    2015-07-01

    Effects of low dose irradiation on the electrical transport current properties of commercially available high-temperature superconducting, coated-conductor tapes were investigated, in view of potential applications in the irradiative environment of fusion reactors. Three different tapes, each with unique as-grown flux-pinning structures, were irradiated with Au and Ni ions at energies that provide a range of damage effects, with accumulated damage levels near that expected for conductors in a fusion reactor environment. Measurements using transport current determined the pre- and post-irradiation resistivity, critical current density, and pinning force density, yielding critical temperatures, irreversibility lines, and inferred vortex creep rates. Results show that at the irradiation damage levels tested, any detriment to as-grown pre-irradiation properties is modest; indeed in one case already-superior pinning forces are enhanced, leading to higher critical currents.

  17. High-density carbon nanotube buckypapers with superior transport and mechanical properties.

    PubMed

    Zhang, Ling; Zhang, Guang; Liu, Changhong; Fan, Shoushan

    2012-09-12

    High-density buckypapers were obtained by using well-aligned carbon nanotube arrays. The density of the buckypapers was as high as 1.39 g cm(-3), which is close to the ultimate density of ideal buckypapers. Then we measured the transport and mechanical properties of the buckypapers. Our results demonstrated that its electrical and thermal conductivities could be almost linearly improved by increasing its density. In particular, its superior thermal conductivity is nearly twice that of common metals, which enables it a lightweight and more efficient heat-transfer materials. The Young's modulus of the buckypapers could reach a magnitude over 2 GPa, which is greatly improved compared with previous reported results. In view of this, our work provided a simple and convenient method to prepare high-density buckypapers with excellent transport and mechanical properties.

  18. Molecular Caging of Graphene with Cyclohexane: Transfer and Electrical Transport

    PubMed Central

    2016-01-01

    Transfer of large, clean, crack- and fold-free graphene sheets is a critical challenge in the field of graphene-based electronic devices. Polymers, conventionally used for transferring two-dimensional materials, irreversibly adsorb yielding a range of unwanted chemical functions and contaminations on the surface. An oil–water interface represents an ideal support for graphene. Cyclohexane, the oil phase, protects graphene from mechanical deformation and minimizes vibrations of the water surface. Remarkably, cyclohexane solidifies at 7 °C forming a plastic crystal phase molecularly conforming graphene, preventing the use of polymers, and thus drastically limiting contamination. Graphene floating at the cyclohexane/water interface exhibits improved electrical performances allowing for new possibilities of in situ, flexible sensor devices at a water interface. PMID:28058279

  19. Transport properties in semiconducting NbS{sub 2} nanoflakes

    SciTech Connect

    Huang, Y. H.; Chen, R. S. Ho, C. H.; Peng, C. C.; Huang, Y. S.

    2014-09-01

    The electronic transport properties in individual niobium disulphide (NbS{sub 2}) nanoflakes mechanically exfoliated from the bulk crystal with three rhombohedral (3R) structure grown by chemical vapor transport were investigated. It is found that the conductivity values of the single-crystalline nanoflakes are approximately two orders of magnitude lower than that of their bulk counterparts. Temperature-dependent conductivity measurements show that the 3R-NbS{sub 2} nanoflakes exhibit semiconducting transport behavior, which is also different from the metallic character in the bulk crystals. In addition, the noncontinuous conductivity variations were observed at the temperature below 180 K for both the nanoflakes and the bulks, which is attributed to the probable charge density wave transition. The photoconductivities in the semiconducting nanoflakes were also observed under the excitation at 532 nm wavelength. The probable mechanisms resulting in the different transport behaviors between the NbS{sub 2} nanostructure and bulk were discussed.

  20. Measurement of gas transport properties for chemical vapor infiltration

    SciTech Connect

    Starr, T.L.; Hablutzel, N.

    1996-12-01

    In the chemical vapor infiltration (CVI) process for fabricating ceramic matrix composites (CMCs), transport of gas phase reactant into the fiber preform is a critical step. The transport can be driven by pressure or by concentration. This report describes methods for measuring this for CVI preforms and partially infiltrated composites. Results are presented for Nicalon fiber cloth layup preforms and composites, Nextel fiber braid preforms and composites, and a Nicalon fiber 3-D weave composite. The results are consistent with a percolating network model for gas transport in CVI preforms and composites. This model predicts inherent variability in local pore characteristics and transport properties, and therefore, in local densification during processing; this may lead to production of gastight composites.

  1. Electrical Property Analytical Prediction on Archimedes Chiral Carbon Nanoscrolls

    NASA Astrophysics Data System (ADS)

    Hassanzadazar, M.; Ahmadi, M. T.; Ismail, Razali; Goudarzi, Hadi

    2016-10-01

    Carbon nanoscrolls (CNS) with flexible exterior areas and interesting electrical and mechanical properties have gained interest in recent years, both experimentally and theoretically. These structures have been employed as ion channels, tunable water channels, molecular sensors, and gene and drug distribution systems. In this study, electrical behaviour of all types of CNS containing armchair, zigzag, and chiral CNSs band structure is investigated. In armchair CNSs, the small band gap among valence and the conduction band as a pseudo-gap are reported, which reveals a semimetallic property for some of these CNSs. This small band gap, as a result of layer interaction, has been confirmed. Also, in many other types of armchair CNSs at the Fermi level, related levels cross each other, illustrating metallic characteristics. On the other hand, our numerical results show small band gaps for zigzag types of CNSs, which means that they are semiconductors. However, it cannot be considered as a general occurrence because only in rare circumstances is a very small band gap observed that gives rise to semimetallic CNSs. In addition, the electrical properties of chiral CNSs are explored. Small band gaps between the associated valence and the conduction band reveals that chiral CNSs mainly exhibit semiconducting behaviour. Finally, all the numerical results are tabulated in the form of a CNS periodic table and a symmetric arrangement with respect to the armchair nanoscrolls and as a table diagonal data for the chiral CNSs is noticed. In addition, this investigation highlights the variations of the energy structure of chiral CNSs with respect to their length. Presented results offer significant potential for chiral CNSs as an alternative to silicon-based sensors in nanotechnology. Therefore, the band gap variations in the presence of attached materials as a sensor platform need to be explored.

  2. Electrical Property Characterization of Neural Stem Cells in Differentiation

    PubMed Central

    Sun, He; Chen, Deyong; Li, Zhaohui; Fan, Beiyuan; George, Julian; Xue, Chengcheng; Cui, Zhanfeng; Wang, Junbo

    2016-01-01

    Electrical property characterization of stem cells could be utilized as a potential label-free biophysical approach to evaluate the differentiation process. However, there has been a lack of technology or tools that can quantify the intrinsic cellular electrical markers (e.g., specific membrane capacitance (Cspecific membrane) and cytoplasm conductivity (σcytoplasm)) for a large amount of stem cells or differentiated cells. In this paper, a microfluidic platform enabling the high-throughput quantification of Cspecific membrane and σcytoplasm from hundreds of single neural stem cells undergoing differentiation was developed to explore the feasibility to characterize the neural stem cell differentiation process without biochemical staining. Experimental quantification using biochemical markers (e.g., Nestin, Tubulin and GFAP) of neural stem cells confirmed the initiation of the differentiation process featured with gradual loss in cellular stemness and increased cell markers for neurons and glial cells. The recorded electrical properties of neural stem cells undergoing differentiation showed distinctive and unique patterns: 1) in the suspension culture before inducing differentiation, a large distribution and difference in σcytoplasm among individual neural stem cells was noticed, which indicated heterogeneity that may result from the nature of suspension culture of neurospheres; and 2) during the differentiation in adhering monolayer culture, significant changes and a large difference in Cspecific membrane were located indicating different expressions of membrane proteins during the differentiation process, and a small distribution difference in σcytoplasm was less significant that indicated the relatively consistent properties of cytoplasm during the culture. In summary, significant differences in Cspecific membrane and σcytoplasm were observed during the neural stem cell differentiation process, which may potentially be used as label-free biophysical markers

  3. Thermal dependence of passive electrical properties of lizard muscle fibres.

    PubMed

    Adams, B A

    1987-11-01

    1. The thermal dependence of passive electrical properties was determined for twitch fibres from the white region of the iliofibularis (IF) muscle of Anolis cristatellus (15-35 degrees C) and Sceloporus occidentalis (15-40 degrees C), and for twitch fibres from the white (15-45 degrees C) and red (15-40 degrees C) regions of the IF of Dipsosaurus dorsalis. These species differ in thermal ecology, with Anolis being the least thermophilic and Dipsosaurus the most thermophilic. 2. Iliofibularis fibres from the three species reacted similarly to changing temperature. As temperature was increased, input resistance (Rin) decreased (average R10 = 0.7), length constant (L) decreased (average R10 = 0.9), time constant (tau) decreased (average R10 = 0.8), sarcoplasmic resistivity (Rs) decreased (average R10 = 0.8) and apparent membrane resistance (Rm) decreased (average R10 = 0.7). In contrast, apparent membrane capacitance (Cm) increased with increasing temperature (average R10 = 1.3). 3. Rin, L, tau and apparent Rm were lowest in fibres from Anolis (the least thermophilic species) and highest in fibres from Dipsosaurus (the most thermophilic species). Anolis had the largest and Dipsosaurus the smallest diameter fibres (126 and 57 micron, respectively). Apparent Cm was highest in fibres from Sceloporus, which had fibres of intermediate diameter (101 micron). Rs did not differ significantly among species. 4. The effect of temperature on the passive electrical properties of these lizard fibres was similar to that reported for muscle fibres from other ectothermic animals (crustaceans, insects, fish and amphibians) but qualitatively different from that reported for some mammalian (cat tenuissimus, goat intercostal) fibres. The changes that occur in the passive electrical properties render the fibres less excitable as temperature increases.

  4. A general design rule to manipulate photocarrier transport path in solar cells and its realization by the plasmonic-electrical effect.

    PubMed

    Sha, Wei E I; Zhu, Hugh L; Chen, Luzhou; Chew, Weng Cho; Choy, Wallace C H

    2015-02-17

    It is well known that transport paths of photocarriers (electrons and holes) before collected by electrodes strongly affect bulk recombination and thus electrical properties of solar cells, including open-circuit voltage and fill factor. For boosting device performance, a general design rule, tailored to arbitrary electron to hole mobility ratio, is proposed to decide the transport paths of photocarriers. Due to a unique ability to localize and concentrate light, plasmonics is explored to manipulate photocarrier transport through spatially redistributing light absorption at the active layer of devices. Without changing the active materials, we conceive a plasmonic-electrical concept, which tunes electrical properties of solar cells via the plasmon-modified optical field distribution, to realize the design rule. Incorporating spectrally and spatially configurable metallic nanostructures, thin-film solar cells are theoretically modelled and experimentally fabricated to validate the design rule and verify the plasmonic-tunable electrical properties. The general design rule, together with the plasmonic-electrical effect, contributes to the evolution of emerging photovoltaics.

  5. A General Design Rule to Manipulate Photocarrier Transport Path in Solar Cells and Its Realization by the Plasmonic-Electrical Effect

    NASA Astrophysics Data System (ADS)

    Sha, Wei E. I.; Zhu, Hugh L.; Chen, Luzhou; Chew, Weng Cho; Choy, Wallace C. H.

    2015-02-01

    It is well known that transport paths of photocarriers (electrons and holes) before collected by electrodes strongly affect bulk recombination and thus electrical properties of solar cells, including open-circuit voltage and fill factor. For boosting device performance, a general design rule, tailored to arbitrary electron to hole mobility ratio, is proposed to decide the transport paths of photocarriers. Due to a unique ability to localize and concentrate light, plasmonics is explored to manipulate photocarrier transport through spatially redistributing light absorption at the active layer of devices. Without changing the active materials, we conceive a plasmonic-electrical concept, which tunes electrical properties of solar cells via the plasmon-modified optical field distribution, to realize the design rule. Incorporating spectrally and spatially configurable metallic nanostructures, thin-film solar cells are theoretically modelled and experimentally fabricated to validate the design rule and verify the plasmonic-tunable electrical properties. The general design rule, together with the plasmonic-electrical effect, contributes to the evolution of emerging photovoltaics.

  6. A General Design Rule to Manipulate Photocarrier Transport Path in Solar Cells and Its Realization by the Plasmonic-Electrical Effect

    PubMed Central

    Sha, Wei E. I.; Zhu, Hugh L.; Chen, Luzhou; Chew, Weng Cho; Choy, Wallace C. H.

    2015-01-01

    It is well known that transport paths of photocarriers (electrons and holes) before collected by electrodes strongly affect bulk recombination and thus electrical properties of solar cells, including open-circuit voltage and fill factor. For boosting device performance, a general design rule, tailored to arbitrary electron to hole mobility ratio, is proposed to decide the transport paths of photocarriers. Due to a unique ability to localize and concentrate light, plasmonics is explored to manipulate photocarrier transport through spatially redistributing light absorption at the active layer of devices. Without changing the active materials, we conceive a plasmonic-electrical concept, which tunes electrical properties of solar cells via the plasmon-modified optical field distribution, to realize the design rule. Incorporating spectrally and spatially configurable metallic nanostructures, thin-film solar cells are theoretically modelled and experimentally fabricated to validate the design rule and verify the plasmonic-tunable electrical properties. The general design rule, together with the plasmonic-electrical effect, contributes to the evolution of emerging photovoltaics. PMID:25686578

  7. Electrical transport behavior of nonstoichiometric magnesium-zinc ferrite

    SciTech Connect

    Ghatak, S.; Sinha, M.; Meikap, A.K.; Pradhan, S.K.

    2010-08-15

    This paper presents the direct current conductivity, alternate current conductivity and dielectric properties of nonstoichiometric magnesium-zinc ferrite below room temperature. The frequency exponent (s) of conductivity shows an anomalous temperature dependency. The magnitude of the temperature exponent (n) of dielectric permittivity strongly depends on frequency and its value decreases with increasing frequency. The grain boundary contribution is dominating over the grain contribution in conduction process and the temperature dependence of resistance due to grain and grain boundary contribution exhibits two activation regions. The ferrite shows positive alternating current magnetoconductivity. The solid state processing technique was used for the preparation of nanocrystalline ferrite powder from oxides of magnesium, zinc and iron. The X-ray diffraction methods were used in determining the structure and composition of obtained ferrite, while multimeter, impedance analyzer, liquid nitrogen cryostat and electromagnet were used in the study of conducting and dielectric properties of ferrite.

  8. Charge transport in electrically doped amorphous organic semiconductors.

    PubMed

    Yoo, Seung-Jun; Kim, Jang-Joo

    2015-06-01

    This article reviews recent progress on charge generation by doping and its influence on the carrier mobility in organic semiconductors (OSs). The doping induced charge generation efficiency is generally low in OSs which was explained by the integer charge transfer model and the hybrid charge transfer model. The ionized dopants formed by charge transfer between hosts and dopants can act as Coulomb traps for mobile charges, and the presence of Coulomb traps in OSs broadens the density of states (DOS) in doped organic films. The Coulomb traps strongly reduce the carrier hopping rate and thereby change the carrier mobility, which was confirmed by experiments in recent years. In order to fully understand the doping mechanism in OSs, further quantitative and systematic analyses of charge transport characteristics must be accomplished.

  9. Transport properties of the mesothelium and interstitium measured in rabbit pericardium.

    PubMed

    Tang, Sonja M Moe; Lai-Fook, Stephen J

    2005-11-01

    The contribution of the pleural mesothelium to pleural liquid and protein transport is still vigorously debated. Recent in vitro studies of stripped pleural membrane and free-standing pericardium have demonstrated active ion solute coupled transport of liquid and transcytosis of protein. However, the relative contribution of the passive transport properties of the pleural mesothelium compared to the pleural interstitium has not been extensively studied. In in vitro studies, we measured the albumin diffusion coefficient, reflection coefficient, hydraulic conductivity and electrical resistance of rabbit pericardium. We used two techniques, treatment with 40 muM nocodazole and a 1-min hypotonic cell lysis with distilled water, to eliminate the effect of the two mesothelial layers on diffusional and hydraulic resistances. Each technique increased the albumin diffusion coefficient and hydraulic conductivity 3- to 4-fold. In hydraulic conductivity experiments using tracer 125I-albumin, nocodazole reduced the reflection coefficient to zero, rendering the pericardium completely permeable to albumin. We applied the cell-lysis technique to the pleural and pericardial mesothelium in sequence to evaluate the separate contribution of each mesothelium. Both diffusional and hydraulic resistances, but not electrical resistance, of the mesothelium were overestimated by the cell-lysis technique. The pleural mesothelium contributed at most 30% of diffusional resistance, 10% of hydraulic resistance and 14% of electrical resistance of the total pericardial resistances. We conclude that the pleural mesothelium is not the primary barrier to protein diffusion or bulk flow of liquid from the pericardial microcirculation to the pleural liquid.

  10. Transport properties of silicate melts at high pressure

    NASA Astrophysics Data System (ADS)

    Lesher, C. E.; Gaudio, S. J.; Clark, A. N.; O'Dwyer-Brown, L.

    2012-12-01

    It is well appreciated that the transport properties (e.g., diffusion, viscosity) of silicate melts are intimately linked by melt structure and the time scales of structural relaxation. These linkages have been explored exten-sively at low pressure, but our understanding is more limited for high-pressure conditions relevant to the Earth's deep interior. Transport property models based on free-volume, activation energy and/or configurational entropy have merits, but their validity in extrapolation is uncertain. Moreover, the structural implications at high pressure are conflicting and lack experimental support. We examine these issues and review theoretical efforts to model transport properties at high pressure, as well as, those constraints provided by laboratory experiments and simulations. We emphasis the need to consider the properties of melt not only for high-pressure superheated conditions, but also for supercooled conditions in the vicinity of the glass transition. For example, the time scales for density relaxation traversing the glass transition at high pressure can be monitored using in situ X-ray miroctomography/absorption and ex vivo by the Archimedes' method combined with spectroscopy. These approaches are amenable to both strong and fragile liquids. Taken together with superliquidus data, we can greatly improve the interpolation of melt properties within the melting interval for refractory mantle compositions.

  11. Correlation of Critical Temperatures and Electrical Properties in Titanium Films

    NASA Astrophysics Data System (ADS)

    Gandini, C.; Lacquaniti, V.; Monticone, E.; Portesi, C.; Rajteri, M.; Rastello, M. L.; Pasca, E.; Ventura, G.

    Recently transition-edge sensors (TES) have obtained an increasing interest as light detectors due to their high energy resolution and broadband response. Titanium (Ti), with transition temperature up to 0.5 K, is among the suitable materials for TES application. In this work we investigate Ti films obtained from two materials of different purity deposited by e-gun on silicon nitride. Films with different thickness and deposition substrate temperature have been measured. Critical temperatures, electrical resistivities and structural properties obtained from x-ray are related to each other.

  12. Surface electrical properties experiment study phase, volume 1

    NASA Technical Reports Server (NTRS)

    Meyer, J. W.; Baker, R. H.; Johnson, L. B.

    1973-01-01

    The evolution of a conceptual design of the flight hardware for the surface electrical properties experiment (SEP), the definition of requests for proposals, the analysis of proposals submitted by prospective flight hardware subcontractors, and recommendations for the flight configuration to be implemented are discussed. Initial efforts were made to assess the electromagnetic environment of the SEP experiment. An EMI receiver and tri-loop antenna were constructed and tests of opportunity were performed with a lunar roving vehicle (LRV). Initial analyses were made of data from these tests with support from this contract, analyses which were continued in depth under the hardware contract.

  13. Homogeneous precipitation synthesis and electrical properties of scandia stabilized zirconia

    NASA Astrophysics Data System (ADS)

    Xu, Gang; Zhang, Yawen; Liao, Chunsheng; Yan, Chunhua

    2001-12-01

    Homogeneous precipitation employing urea was utilized to prepare ultrafine and weakly-agglomerated 8 mol% scandia-stabilized zirconia (8ScSZ) powders. Their crystal structure, particle and electrical properties were investigated by scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, thermo-gravimetry and differential thermal analysis, BET surface area analysis, and impedance spectroscopy, respectively. 8ScSZ polycrystals in a pure cubic phase were obtained after sintering at a low temperature of 600 °C. Elevating sintering temperature can increase the oxide ion conductivity, especially the grain boundary conductivity.

  14. Thermal transport properties of niobium and some niobium base alloys from 80 to 1600/sup 0/K

    SciTech Connect

    Moore, J.P.; Graves, R.S.; Williams, R.K.

    1980-01-01

    The electrical resistivities and absolute Seebeck coefficients of 99.8 at. % niobium with a RRR of 36, Nb-4.8 at. % W, Nb-5 at. % Mo, Nb-10 at. % Mo, and Nb-2.4 at. % Mo-2.4 at. % Zr were measured from 80 to 1600/sup 0/K, and the thermal conductivities of the niobium and Nb-5 at. % W were measured from 80 to 1300/sup 0/K. A technique is described for measuring the electrical resistivity and Seebeck coefficient of a specimen during radial heat flow measurements of the thermal conductivity. The transport property results, which had uncertainties of +-0.4%for electrical resistivity and +-1.4% for thermal conductivity, showed the influence of tungsten and molybdenum solutes on the transport properties of niobium and were used to obtain the electronic Lorenz function of pure niobium, which was found to approach the Sommerfeld value at high temperatures.

  15. Exploration of electric properties of bone compared to cement: streaming potential and piezoelectirc properties

    NASA Astrophysics Data System (ADS)

    Dry, Carolyn

    2015-03-01

    Bone is a material after which to model construction materials for many reasons, including its great strength, toughness, and adaptability. This paper focuses on bone's intrinsic ability to adapt to its environment, namely loading conditions. Research on bone's electrical properties reveals that two phenomena occur in bone to allow it to adapt to environmental changes; they are the inherent piezoelectric property of bone and the streaming potential of bone [1]. Together they create charge differences that attract ions to specific regions of the bone, namely those under greatest stress, in order to build up the region to handle the applied load. Research on the utilization of these properties in cement in order to increase adaptability was studied along with 1) the inherent electric properties of the cement itself and 2) considered the introduction of a different polymer or ceramic within the cement to impart piezoelectricity and streaming potential.

  16. Electron transport properties of bis[2-(2-hydroxyphenyl)-pyridine]beryllium investigated by impedance spectroscopy

    SciTech Connect

    Wang, Yanping; Chen, Jiangshan; Huang, Jinying; Ma, Dongge E-mail: dongls@ciac.jl.cn; Dong, Lisong E-mail: dongls@ciac.jl.cn; Chen, Hui

    2014-06-14

    The electron transport properties of bis[2-(2-hydroxyphenyl)-pyridine] beryllium (Bepp{sub 2}) are investigated by impedance spectroscopy over a frequency range of 10 Hz to 13 MHz. The Cole-Cole plots demonstrate that the Bepp{sub 2}-based device can be represented by a single parallel resistance R{sub p} and capacitance C{sub p} network with a series resistance R{sub s}. The current-voltage characteristics and the variation of R{sub p} with applied bias voltage indicate the electron conduction of space-charge-limited current with exponential trap distributions in Bepp{sub 2}. It can be seen that the electron mobility exhibits strong field-dependence in low electric field region and almost saturate in high electric field region. It is experimentally found that Bepp{sub 2} shows dispersion transport and becomes weak as the electric field increases. The activation energy is determined to be 0.043 eV by temperature-dependent conductivity, which is consistent with the result obtained from the temperature-dependent current density characteristics. The electron mobility reaches the orders of 10{sup −6}–10{sup −5} cm{sup 2} V{sup −1} s{sup −1}, depending on the electric field.

  17. Plug-in Electric Vehicle Infrastructure: A Foundation for Electrified Transportation: Preprint

    SciTech Connect

    Markel, T.

    2010-04-01

    Plug-in electric vehicles (PEVs)--which include all-electric vehicles and plug-in hybrid electric vehicles--provide a new opportunity for reducing oil consumption by drawing power from the electric grid. To maximize the benefits of PEVs, the emerging PEV infrastructure--from battery manufacturing to communication and control between the vehicle and the grid--must provide access to clean electricity, satisfy stakeholder expectations, and ensure safety. Currently, codes and standards organizations are collaborating on a PEV infrastructure plan. Establishing a PEV infrastructure framework will create new opportunities for business and job development initiating the move toward electrified transportation. This paper summarizes the components of the PEV infrastructure, challenges and opportunities related to the design and deployment of the infrastructure, and the potential benefits.

  18. Kinetic theory of transport processes in partially ionized reactive plasma, II: Electron transport properties

    NASA Astrophysics Data System (ADS)

    Zhdanov, V. M.; Stepanenko, A. A.

    2016-11-01

    The previously obtained in (Zhdanov and Stepanenko, 2016) general transport equations for partially ionized reactive plasma are employed for analysis of electron transport properties in molecular and atomic plasmas. We account for both elastic and inelastic interaction channels of electrons with atoms and molecules of plasma and also the processes of electron impact ionization of neutral particles and three-body ion-electron recombination. The system of scalar transport equations for electrons is discussed and the expressions for non-equilibrium corrections to electron ionization and recombination rates and the diagonal part of the electron pressure tensor are derived. Special attention is paid to analysis of electron energy relaxation during collisions with plasma particles having internal degrees of freedom and the expression for the electron coefficient of inelastic energy losses is deduced. We also derive the expressions for electron vector and tensorial transport fluxes and the corresponding transport coefficients for partially ionized reactive plasma, which represent a generalization of the well-known results obtained by Devoto (1967). The results of numerical evaluation of contribution from electron inelastic collisions with neutral particles to electron transport properties are presented for a series of molecular and atomic gases.

  19. Electrical Transport Properties of Polycrystalline Monolayer Molybdenum Disulfide

    DTIC Science & Technology

    2014-07-14

    PERFORMING ORGANIZATION REPORT William Marsh Rice University NUMBER 6100 Main St., MS- 16 Houston, TX 7700S -1827 9. SPONSORING/MONITORING AGENCY... Rice University, Houston, Texas 77005, United States and *Sensors and Electron Devices Directorate, US Anny Research Laboratory, Adelphi, Maryland 20723

  20. Transport processes in partially saturate concrete: Testing and liquid properties

    NASA Astrophysics Data System (ADS)

    Villani, Chiara

    The measurement of transport properties of concrete is considered by many to have the potential to serve as a performance criterion that can be related to concrete durability. However, the sensitivity of transport tests to several parameters combined with the low permeability of concrete complicates the testing. Gas permeability and diffusivity test methods are attractive due to the ease of testing, their non-destructive nature and their potential to correlate to in-field carbonation of reinforced concrete structures. This work was aimed at investigating the potential of existing gas transport tests as a way to reliably quantify transport properties in concrete. In this study gas permeability and diffusivity test methods were analyzed comparing their performance in terms of repeatability and variability. The influence of several parameters was investigated such as moisture content, mixture proportions and gas flow. A closer look to the influence of pressure revealed an anomalous trend of permeability with respect to pressure. An alternative calculation is proposed in an effort to move towards the determination of intrinsic material properties that can serve as an input for service life prediction models. The impact of deicing salts exposure was also analyzed with respect to their alteration of the degree of saturation as this may affect gas transport in cementitious materials. Limited information were previously available on liquid properties over a wide range of concentrations. To overcome this limitation, this study quantified surface tension, viscosity in presence of deicing salts in a broad concentration range and at different temperatures. Existing models were applied to predict the change of fluid properties during drying. Vapor desorption isotherms were obtained to investigate the influence of deicing salts presence on the non-linear moisture diffusion coefficient. Semi-empirical models were used to quantify the initiation and the rate of drying using liquid

  1. Electric Pulse Discharge Activated Carbon Supercapacitors for Transportation Application

    NASA Astrophysics Data System (ADS)

    Nayak, Subhadarshi; Agrawal, Jyoti

    2012-03-01

    ScienceTomorrow is developing a high-speed, low-cost process for synthesizing high-porosity electrodes for electrochemical double-layer capacitors. Four types of coal (lignite, subbituminous, bituminous, and anthracite) were used as precursor materials for spark discharge activation with multiscale porous structure. The final porosity and pore distribution depended, among other factors, on precursor type. The high gas content in low-grade carbon resulted in mechanical disintegration, whereas high capacitance was attained in higher-grade coal. The properties, including capacitance, mechanical robustness, and internal conductivity, were excellent when the cost is taken into consideration.

  2. Electrical properties and initial permeability of Cu-Mg ferrites

    NASA Astrophysics Data System (ADS)

    Ateia, E.; Ahmed, M. A.; Ghouniem, R. M.

    2014-05-01

    A series of polycrystalline spinel ferrites with composition Cu1-xMgxFe2O4 where 0.0 ≤ x ≤ 1 are prepared by the standard ceramic method. The single-phase cubic spinel structure of all the samples has been confirmed from X-ray diffraction analysis. The lattice constant increases linearly with increasing magnesium content obeying Vegard's law. The electrical properties (ɛ‧, and σ) of the prepared samples are measured at different temperatures as a function of applied frequency ranging from 100 kHz up to 5 MHz. The general trend of ɛ‧, and σ is decreased with increasing Mg2+ and increases with increasing temperature. The observed variation of dielectric properties is explained on the basis of Cu2+/Cu1+ ionic concentration as well as the electronic hopping frequency between Fe2+ and Fe3+ ions in the present samples. The data of initial permeability is also discussed.

  3. DNA-linked nanoparticle materials: optical, electrical, and structural properties

    NASA Astrophysics Data System (ADS)

    Lazarides, A.; Park, S.-J.; Mirkin, C.; Storhoff, J.; Schatz, G.; Brazis, P.; Kannewurf, C.

    2001-03-01

    Novel bioinorganic materials composed of Au nanoparticles linked with DNA have been developed as colorimetric DNA sensors. In the presence of complimentary DNA, particles dressed with one of two oligonucleotide sequences are linked to form binary nanoparticle aggregates. Assemblies linked at 298K have plasmon frequency shifts that decrease with increasing linker length; annealing, however, eliminates the length dependence of the shift. Neither sedimentation rate measurements nor theoretical studies of the optical properties provide unambiguous explanation. However, small-angle X-ray scattering (SAXS) measurements indicate that separations between nanoparticles with or without annealing are proportional to the number of base pairs in the oligonucleotide linkers. DNA is thus shown to offer a means for tuning separations in nanoparticle materials. We have also investigated the electrical and structural properties of dry Au nanoparticle films linked by DNA. The assemblies are semiconducting, which suggests that DNA can be used as a chemically specific scaffolding material for assembly of conductive structures.

  4. Electrical properties of teflon and ceramic capacitors at high temperatures

    NASA Technical Reports Server (NTRS)

    Hammoud, A. N.; Baumann, E. D.; Myers, I. T.; Overton, E.

    1992-01-01

    Space power systems and components are often required to operate efficiently and reliably in harsh environments where stresses, such as high temperature, are encountered. These systems must, therefore, withstand exposure to high temperature while still providing good electrical and other functional properties. Experiments were carried out to evaluate Teflon and ceramic capacitors for potential use in high temperature applications. The capacitors were characterized in terms of their capacitance and dielectric loss as a function of temperature, up to 200 C. At a given temperature, these properties were obtained in a frequency range of 50 Hz to 100 kHz. DC leakage current measurements were also performed in a temperature range from 25 to 200 C. The results obtained are discussed and conclusions are made concerning the suitability of the capacitors studied for high temperature applications.

  5. Mechanical and Electrical Properties of Organogels with Multiwall Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Moniruzzaman, Mohammad; Winey, Karen

    2008-03-01

    Organogels are fascinating thermally reversible viscoelastic materials that are comprised of an organic liquid and low concentrations (typically <2 wt %) of low molecular mass organic gelators. We have fabricated the first organogel/carbon nanotube composites using 12-hydroxystearic acid (HSA) as the gelator molecule and pristine and carboxylated multi-wall carbon nanotubes as the nanofillers and 1,2-dichlorobenzene as the organic solvent. We have achieved significant improvements in the mechanical and electrical properties of organogels by incorporating these carbon nanotubes. For example, the linear viscoelastic regime of the HSA organogel, an indicator of the strength of the gel, extends by a factor of 4 with the incorporation of 0.2 wt% of the carboxylated nanotubes. Also, the carbon nanotubes (specially the pristine tubes) improve the electrical conductivity of the organogels, e.g. six orders of magnitude enhancement in electrical conductivity with 0.2 wt% of pristine tubes. Differential scanning calorimetry experiments indicate that the nanotubes do not affect the thermoreversibility of the organogels.

  6. Modeling electron transport in the presence of electric and magnetic fields.

    SciTech Connect

    Fan, Wesley C.; Drumm, Clifton Russell; Pautz, Shawn D.; Turner, C. David

    2013-09-01

    This report describes the theoretical background on modeling electron transport in the presence of electric and magnetic fields by incorporating the effects of the Lorentz force on electron motion into the Boltzmann transport equation. Electromagnetic fields alter the electron energy and trajectory continuously, and these effects can be characterized mathematically by differential operators in terms of electron energy and direction. Numerical solution techniques, based on the discrete-ordinates and finite-element methods, are developed and implemented in an existing radiation transport code, SCEPTRE.

  7. Transportation and dynamic networks: Models, theory, and applications to supply chains, electric power, and financial networks

    NASA Astrophysics Data System (ADS)

    Liu, Zugang

    Network systems, including transportation and logistic systems, electric power generation and distribution networks as well as financial networks, provide the critical infrastructure for the functioning of our societies and economies. The understanding of the dynamic behavior of such systems is also crucial to national security and prosperity. The identification of new connections between distinct network systems is the inspiration for the research in this dissertation. In particular, I answer two questions raised by Beckmann, McGuire, and Winsten (1956) and Copeland (1952) over half a century ago, which are, respectively, how are electric power flows related to transportation flows and does money flow like water or electricity? In addition, in this dissertation, I achieve the following: (1) I establish the relationships between transportation networks and three other classes of complex network systems: supply chain networks, electric power generation and transmission networks, and financial networks with intermediation. The establishment of such connections provides novel theoretical insights as well as new pricing mechanisms, and efficient computational methods. (2) I develop new modeling frameworks based on evolutionary variational inequality theory that capture the dynamics of such network systems in terms of the time-varying flows and incurred costs, prices, and, where applicable, profits. This dissertation studies the dynamics of such network systems by addressing both internal competition and/or cooperation, and external changes, such as varying costs and demands. (3) I focus, in depth, on electric power supply chains. By exploiting the relationships between transportation networks and electric power supply chains, I develop a large-scale network model that integrates electric power supply chains and fuel supply markets. The model captures both the economic transactions as well as the physical transmission constraints. The model is then applied to the New

  8. Transport properties of the Fermi hard-sphere system

    SciTech Connect

    Mecca, Angela; Lovato, Alessandro; Benhar, Omar; Polls, Artur

    2016-03-01

    The transport properties of neutron star matter play an important role in many astrophysical processes. We report the results of a calculation of the shear viscosity and thermal conductivity coefficients of the hard-sphere fermion system of degeneracy ν = 2, that can be regarded as a model of pure neutron matter. Our approach is based on the effective interaction obtained from the formalism of correlated basis functions and the cluster expansion technique. The resulting transport coefficients show a strong sensitivity to the quasiparticle effective mass, reflecting the effect of second-order contributions to the self-energy that are not taken into account in nuclear matter studies available in the literature.

  9. Mechanical and Electrical Properties of Aluminum/Epoxy Nanocomposites

    NASA Astrophysics Data System (ADS)

    Dong, Lina; Zhou, Wenying; Sui, Xuezhen; Wang, Zijun; Cai, Huiwu; Wu, Peng; Zhang, Yating; Zhou, Anning

    2016-11-01

    Surface-modified self-passivated aluminum (Al) nanoparticles were used for reinforcing epoxy (EP) resin, and the curing behavior, mechanical and electrical properties of the Al/EP nanocomposites were investigated. The incorporation of Al nanoparticles into EP significantly decreases the cure reaction enthalpy of the nancomposites, and the apparent activation energy of Al/EP systems is 64.96 kJ/mol. The coefficient of thermal expansion of the nanocomposites decreases with increasing the Al loading due to the strong interaction between the Al and the EP matrix. The storage modulus of the nanocomposites increases continuously with Al content, whereas, the glass transition temperature declines slightly. With increasing the Al content, the tensile modulus, flexural modulus and compressive modulus of the nanocomposites increase continuously compared with the neat one. The mechanical properties are improved by Al nanoparticles at low Al contents. The best overall dielectric and electrical performance are achieved about at 1 wt.% of Al concentration. The enhanced dielectric breakdown strength is mainly related to the insulating alumina shell on the surface of core Al and the strong interfacial interactions.

  10. Properties of electric turbulence in the polar cap ionosphere

    NASA Astrophysics Data System (ADS)

    Golovchanskaya, I. V.; Kozelov, B. V.

    2010-10-01

    Small-scale (scales of ˜0.5-256 km) electric fields in the polar cap ionosphere are studied on the basis of measurements of the Dynamics Explorer 2 (DE-2) low-altitude satellite with a polar orbit. Nineteen DE-2 passes through the high-latitude ionosphere from the morning side to the evening side are considered when the IMF z component was southward. A rather extensive polar cap, which could be identified using the ɛ- t spectrograms of precipitating particles with auroral energies, was formed during the analyzed events. It is shown that the logarithmic diagrams (LDs), constructed using the discrete wavelet transform of electric fields in the polar cap, are power law (μ ˜ s α). Here, μ is the variance of the detail coefficients of the signal discrete wavelet transform, s is the wavelet scale, and index α characterizes the LD slope. The probability density functions P(δ E, s) of the electric field fluctuations δ E observed on different scales s are non-Gaussian and have intensified wings. When the probability density functions are renormalized, that is constructed of δ E/ s γ, where γ is the scaling exponent, they lie near a single curve, which indicates that the studied fields are statistically self-similar. In spite of the fact that the amplitude of electric fluctuations in the polar cap is much smaller than in the auroral zone, the quantitative characteristics of field scaling in the two regions are similar. Two possible causes of the observed turbulent structure of the electric field in the polar cap are considered: (1) the structure is transferred from the solar wind, which is known to have turbulent properties, and (2) the structure is generated by convection velocity shears in the region of open magnetic field lines. The detected dependence of the characteristic distribution of turbulent electric fields over the polar cap region on IMF B y and the correlation of the rms amplitudes of δ E fluctuations with IMF B z and the solar wind transfer

  11. Variation in electrical properties of gamma irradiated cadmium selenate nanowires

    NASA Astrophysics Data System (ADS)

    Chauhan, R. P.; Rana, Pallavi; Narula, Chetna; Panchal, Suresh; Choudhary, Ritika

    2016-07-01

    Preparation of low-dimensional materials attracts more and more interest in the last few years, mainly due to the wide field of potential commercial applications ranging from life sciences, medicine and biotechnology to communication and electronics. One-dimensional systems are the smallest dimension structures that can be used for efficient transport of electrons and thus expected to be critical to the function and integration of nanoscale devices. Nanowires with well controlled morphology and extremely high aspect ratio can be obtained by replicating a nanoporous polymer ion-track membrane with cylindrical pores of controlled dimensions. With this technique, materials can be deposited within the pores of the membrane by electrochemical reduction of the desired ion. In the present study, cadmium selenate nanowires were synthesized potentiostatically via template method. These synthesized nanowires were then exposed to gamma rays by using a 60Co source at the Inter University Accelerator Centre, New Delhi, India. Structural, morphological, electrical and elemental characterizations were made in order to analyze the effect of gamma irradiation on the synthesized nanowires. I-V measurements of cadmium selenate nanowires, before and after irradiation were made with the help of Keithley 2400 source meter and Ecopia probe station. A significant change in the electrical conductivity of cadmium selenate nanowires was found after gamma irradiation. The crystallography of the synthesized nanowires was also studied using a Rigaku X-ray diffractrometer equipped with Cu-Kα radiation. XRD patterns of irradiated samples showed no variation in the peak positions or phase change.

  12. Passive Electrical Properties of Toad Urinary Bladder Epithelium

    PubMed Central

    Reuss, Luis; Finn, Arthur L.

    1974-01-01

    The electrical resistances of the transcellular and paracellular pathways across the toad urinary bladder epithelium (a typical "tight" sodium-transporting epithelium) were determined by two independent sets of electrophysiological measurements: (a) the measurement of the total transepithelial resistance, the ratio of resistance of the apical to the basal cell membrane, and cable analysis of the voltage spread into the epithelium; (b) the measurement of the total transepithelial resistance and the ratio of resistances of both cell membranes before and after replacing all mucosal sodium with potassium (thus, increasing selectively the resistance of the apical membrane). The results obtained with both methods indicate the presence of a finite transepithelial shunt pathway, whose resistance is about 1.8 times the resistance of the transcellular pathway. Appropriate calculations show that the resistance of the shunt pathway is almost exclusively determined by the zonula occludens section of the limiting junctions. The mean resistance of the apical cell membrane is 1.7 times that of the basal cell membrane. The use of nonconducting materials on the mucosal side allowed us to demonstrate that apparently all epithelial cells are electrically coupled, with a mean space constant of 460 µm, and a voltage spread consistent with a thin sheet model. PMID:4209766

  13. Interrelationships between electrical properties and microstructure of human trabecular bone

    NASA Astrophysics Data System (ADS)

    Sierpowska, J.; Hakulinen, M. A.; Töyräs, J.; Day, J. S.; Weinans, H.; Kiviranta, I.; Jurvelin, J. S.; Lappalainen, R.

    2006-10-01

    Microstructural changes, such as reduction of trabecular thickness and number, are characteristic signs of osteoporosis leading to diminished bone strength. Electrical and dielectric parameters might provide diagnostically valuable information on trabecular bone microstructure not extractable from bone mineral density measurements. In this study, structural properties of human trabecular bone samples (n = 26) harvested from the distal femur and proximal tibia were investigated using the computed microtomography (microCT) technique. Quantitative parameters, e.g. structural model index (SMI) or trabecular bone volume fraction (BV/TV), were calculated. In addition, the samples were examined electrically over a wide frequency range (50 Hz-5 MHz) using a two-electrode impedance spectroscopy set-up. Relative permittivity, loss factor, conductivity, phase angle, specific impedance and dissipation factor were determined. Significant linear correlations were obtained between the dissipation factor and BV/TV or SMI (|r| >= 0.70, p < 0.01, n = 26). Principal component analyses, conducted on electrical and structural parameters, revealed that the high frequency principal component of the dissipation factor was significantly related to SMI (r = 0.72, p < 0.01, n = 26). The linear combination of high and low frequency relative permittivity predicted 73% of the variation in BV/TV. To conclude, electrical and dielectric parameters of trabecular bone, especially relative permittivity and dissipation factor, were significantly and specifically related to a trabecular microstructure as characterized with microCT. The data gathered in this study constitute a useful basis for theoretical and experimental work towards the development of impedance spectroscopy techniques for detection of bone quality in vitro or in special cases of open surgery.

  14. Electrical, magnetic, and thermal properties of the δ-FeZn10 complex intermetallic phase

    NASA Astrophysics Data System (ADS)

    Jazbec, S.; Koželj, P.; Vrtnik, S.; Jagličić, Z.; Popčević, P.; Ivkov, J.; Stanić, D.; Smontara, A.; Feuerbacher, M.; Dolinšek, J.

    2012-08-01

    We report the electrical, magnetic, and thermal properties of the δ-FeZn10 phase in the zinc-rich domain of the Fe-Zn system. The δ-FeZn10 phase possesses high structural complexity typical of complex metallic alloys: a giant unit cell comprising 556 atoms, polyhedral atomic order with icosahedrally coordinated environments, fractionally occupied lattice sites, and statistically disordered atomic clusters that introduce intrinsic disorder into the structure. Structural disorder results in suppression of the electrical and heat transport phenomena, making δ-FeZn10 a poor electrical and thermal conductor. Structural complexity results in a complex electronic structure that is reflected in the opposite signs of the thermoelectric power and the Hall coefficient. The δ-FeZn10 phase is paramagnetic down to the lowest investigated temperature of 2 K with a significant interspin coupling of antiferromagnetic type. Specific heat indicates the formation of short-range-ordered spin clusters at low temperatures, very likely a precursor of a phase transition to a collective magnetic state that would take place below 2 K. The magnetoresistance of δ-FeZn10 is sizeable, amounting to 1.5% at 2 K in a 9-T field. The electrical resistivity exhibits a maximum at about 220 K, and its temperature dependence could be explained by the theory of slow charge carriers, applicable to metallic systems with weak dispersion of the electronic bands, where the electron motion changes from ballistic to diffusive upon heating.

  15. Investigation of structural, optical, electrical and dielectric properties of catalytic sprayed hausmannite thin film

    SciTech Connect

    Larbi, T.; Ouni, B.; Boukhachem, A.; Boubaker, K. Amlouk, M.

    2014-12-15

    Hausmannite Mn{sub 3}O{sub 4} thin film have been synthesized using spray pyrolysis method. These films are characterized using X-ray diffraction (XRD), atomic force microscope AFM, UV–vis–NIR spectroscopy and impedance spectroscopy. XRD study confirms the tetragonal structure of the as-deposited films with lattice parameters, a = 5.1822 Å and c = 9.4563 Å and a grain size of about 56 nm. UV–vis–NIR spectroscopy was further used to estimate optical constants such as extinction coefficient, refractive index, band gap and Urbach energy. Moreover, impedance spectroscopy analysis was employed to estimate electrical and dielectrical properties of the sprayed thin films. The activation energy values deduced from DC conductivity and relaxation frequency were almost the same, revealing that the transport phenomena is thermally activated by hopping between localized states. The AC conductivity is found to be proportional to ω{sup s}. The temperature dependence of the AC conductivity and the frequency exponent, s was reasonably well interpreted in terms of the correlated barrier-hopping CBH model. The dielectric properties were sensitive to temperature and frequency. The study of the electrical modulus indicated that the charge carrier was localized. Experimental results concerning optical constants as Urbach energy, dielectric constant, electric modulus and AC and DC conductivity were discussed in terms of the hopping model as suggested by Elliott.

  16. Evaluation of the electrical properties of dust storms by multi-parameter observations and theoretical calculations

    NASA Astrophysics Data System (ADS)

    Zhang, Huan; Bo, Tian-Li; Zheng, Xiaojing

    2017-03-01

    Dusty phenomena, such as wind-blown sand, dust devils, and dust storms, play key roles in Earth's climate and geological processes. Dust electrification considerably affects the lifting and transport of dust particles. However, the electrical properties of dust storms remain poorly understood. Here, we conducted multi-parameter measurements and theoretical calculations to investigate the electrical properties of dust storms and their application to dust storm prediction. The results show that the vertical electric field (E-field) decreases first, then increases, and finally decreases with the height above the ground, reversing its direction at two heights, ∼ 8- 12 and ∼ 24 m. This suggests that the charge polarity of dust particles changes from negative to positive and back to negative again as the height increases. By carefully analyzing the E-field and dust concentration data, we further found that there is a significant positive linear relationship between the measured E-field intensity and dust concentration at the given ambient conditions. In addition, measurements and calculations demonstrate that a substantial enhancement in the vertical E-field can be observed several hours before the arrival of the external-source dust storms, indicating that the E-field can be used to provide an early warning of external-source dust storms.

  17. The magnetic and transport properties of the Co2FeGa Heusler alloy

    NASA Astrophysics Data System (ADS)

    Zhang, Ming; Brück, Ekkes; de Boer, Frank R.; Li, Zhuangzhi; Wu, Guangheng

    2004-08-01

    The magnetic and transport properties of the Co2FeGa Heusler alloy have been investigated. The results show that the temperature dependence of the magnetization follows the spin-wave behaviour at low temperature. The electrical resistivity behaves according to a ~T2 power law, which may be mainly attributed to electron-electron scattering, and the contribution of electron-phonon scattering to the resistivity seems to be small. We have not observed remarkable magnetoresistance in our measurements. Point contact Andreev reflection measurements of the spin-polarization yield a polarization of 59%, which is consistent with the theoretical prediction by a first-principles calculation.

  18. Electrical properties of vanadium tungsten oxide thin films

    SciTech Connect

    Nam, Sung-Pill; Noh, Hyun-Ji; Lee, Sung-Gap; Lee, Young-Hie

    2010-03-15

    The vanadium tungsten oxide thin films deposited on Pt/Ti/SiO{sub 2}/Si substrates by RF sputtering exhibited good TCR and dielectric properties. The dependence of crystallization and electrical properties are related to the grain size of V{sub 1.85}W{sub 0.15}O{sub 5} thin films with different annealing temperatures. It was found that the dielectric properties and TCR properties of V{sub 1.85}W{sub 0.15}O{sub 5} thin films were strongly dependent upon the annealing temperature. The dielectric constants of the V{sub 1.85}W{sub 0.15}O{sub 5} thin films annealed at 400 {sup o}C were 44, with a dielectric loss of 0.83%. The TCR values of the V{sub 1.85}W{sub 0.15}O{sub 5} thin films annealed at 400 {sup o}C were about -3.45%/K.

  19. Using Reactive Transport Modeling to Understand Changes in Electrical Conductivity Associated with Bacterial Growth and Respiration

    NASA Astrophysics Data System (ADS)

    Regberg, A. B.; Singha, K.; Picardal, F.; Brantley, S. L.

    2011-12-01

    Previous research has linked measured changes in the bulk electrical conductivity (σb) of water-saturated sediments to the respiration and growth of anaerobic bacteria. If the mechanism causing this signal is understood and characterized it could be used to identify and monitor zones of bacterial activity in the subsurface. The 1-D reactive transport model PHREEQC was used to understand σb signals by modeling chemical gradients within two column reactors and corresponding changes in effluent chemistry. The flow-through column reactors were packed with Fe(III)-bearing sediment from Oyster, VA and inoculated with an environmental consortia of microorganisms. Influent in the first reactor was amended with 1mM Na-acetate to encourage the growth of iron-reducing bacteria. Influent in the second reactor was amended with 0.1mM Na-Acetate and 2mM NaNO3 to encourage the growth of nitrate-reducing bacteria. While effluent concentrations of acetate, Fe(II), NO3-, NO2-, and NH4+ remained at steady state, we measured a 3-fold increase (0.055 S/m - 0.2 S/m) in σb in the iron-reducing column and a 10-fold increase in σb (0.07 S/m - 0.8 S/m) in the nitrate-reducing column over 198 days. The ionic strength in both reactors remained constant through time indicating that the measured increases in σb were not caused by changing effluent concentrations. PHREEQC successfully matched the measured changes in effluent concentrations for both columns when the reaction database was modified in the following manner. For the iron-reducing column, kinetic expressions governing the rate of iron reduction, the rate of bacterial growth, and the production of methane were added to the reaction database. Additionally, surface adsorption and cation exchange reactions were added so that the model was consistent with measured effluent chemistry. For the nitrate-reducing column, kinetic expressions governing nitrate reduction and bacterial growth were added to the reaction database. Additionally

  20. Thermodynamic properties and transport coefficients of two-temperature helium thermal plasmas

    NASA Astrophysics Data System (ADS)

    Guo, Xiaoxue; Murphy, Anthony B.; Li, Xingwen

    2017-03-01

    Helium thermal plasmas are in widespread use in arc welding and many other industrial applications. Simulation of these processes relies on accurate plasma property data, such as plasma composition, thermodynamic properties and transport coefficients. Departures from LTE (local thermodynamic equilibrium) generally occur in some regions of helium plasmas. In this paper, properties are calculated allowing for different values of the electron temperature, T e, and heavy-species temperature, T h, at atmospheric pressure from 300 K to 30 000 K. The plasma composition is first calculated using the mass action law, and the two-temperature thermodynamic properties are then derived. The viscosity, diffusion coefficients, electrical conductivity and thermal conductivity of the two-temperature helium thermal plasma are obtained using a recently-developed method that retains coupling between electrons and heavy species by including the electron–heavy-species collision term in the heavy-species Boltzmann equation. It is shown that the viscosity and the diffusion coefficients strongly depend on non-equilibrium ratio θ (θ ={{T}\\text{e}}/{{T}\\text{h}} ), through the plasma composition and the collision integrals. The electrical conductivity, which depends on the electron number density and ordinary diffusion coefficients, and the thermal conductivity have similar dependencies. The choice of definition of the Debye length is shown to affect the electrical conductivity significantly for θ  >  1. By comparing with literature data, it is shown that the coupling between electrons and heavy species has a significant influence on the electrical conductivity, but not on the viscosity. Plasma properties are tabulated in the supplementary data.

  1. Maxwell-Wagner-Sillars effects on the thermal-transport properties of polymer-dispersed liquid crystals.

    PubMed

    Kuriakose, M; Longuemart, S; Depriester, M; Delenclos, S; Sahraoui, A Hadj

    2014-02-01

    We present the depolarization field effects (Maxwell-Wagner-Sillars effect) for the thermal transport properties of polymer dispersed liquid crystal composites under a frequency-dependent electric field. The experiments were conducted on polystyrene/4-Cyano-4'-pentylbiphenyl (PS/5CB) PDLCs of 73 vol.% and 85 vol.% liquid crystal (LC) concentrations. A self-consistent field approximation model is used to deduce the electrical properties of polymer and LC materials as well as the threshold electric field. Electric field-varying (at constant frequency) experiments were also conducted to calculate the interfacial thermal resistance between the LC droplets and polymer matrix as well as to find the elastic constant of LCs in droplet form.

  2. Electrical-transport, magnetoresistance and magnetic properties of La{sub 0.7}Ca{sub 0.3}MnO{sub 3} and La{sub 0.7}Ca{sub 0.24}Sr{sub 0.06}MnO{sub 3} single crystals

    SciTech Connect

    Tank, Tejas M. Sanyal, S. P.; Bodhaye, Ashish; Mukovskii, Ya. M.

    2015-06-24

    We report the electrical-transport, magnetoresistance and magnetic properties of the hole doped La{sub 0.7}Ca{sub 0.3}MnO{sub 3} (LCMO) and La{sub 0.7}Ca{sub 0.24}Sr{sub 0.06}MnO{sub 3} (LCSMO) single crystals. It was prepared using floating zone technique. The resistivity data shows the metal to insulator transition (T{sub MI}) occurs at 211 K along c-axis and T{sub MI} = 185 K the ab-plane for LCMO and T{sub MI} = 290 K along the c-axis and T{sub MI} = 280 K along the ab-plane for LCSMO single crystals. It is observed that the T{sub MI} is higher along the c-axis as compared to that in the ab-plane, consequently signifying more favorable hoping of electrons is along the c-axis. The ac-susceptibility measurement shows that this material exhibits ferromagnetic to paramagnetic transition temperature (TC) at 206 K for LCMO and T{sub C} = 277 K for LCSMO single crystals. For magnetic memory device application point of view, the sample shows the maximum MR of 98% for LCMO and 80% for LCSMO single crystals at 8T applied magnetic field. Doping small amount of Sr (0.06%) reveals that the electronic and magnetic phase transition in CMR single crystal increases substantially and useful for device application. This is first time such type of comparative study in these manganite single crystals.

  3. Electrical characterization of non-Fickian transport in groundwater and hyporheic systems

    NASA Astrophysics Data System (ADS)

    Singha, Kamini; Pidlisecky, Adam; Day-Lewis, Frederick D.; Gooseff, Michael N.

    2008-04-01

    Recent work indicates that processes controlling solute mass transfer between mobile and less mobile domains in porous media may be quantified by combining electrical geophysical methods and electrically conductive tracers. Whereas direct geochemical measurements of solute preferentially sample the mobile domain, electrical geophysical methods are sensitive to changes in bulk electrical conductivity (bulk EC) and therefore sample EC in both the mobile and immobile domains. Consequently, the conductivity difference between direct geochemical samples and remotely sensed electrical geophysical measurements may provide an indication of mass transfer rates and mobile and immobile porosities in situ. Here we present (1) an overview of a theoretical framework for determining parameters controlling mass transfer with electrical resistivity in situ; (2) a review of a case study estimating mass transfer processes in a pilot-scale aquifer storage recovery test; and (3) an example application of this method for estimating mass transfer in watershed settings between streams and the hyporheic corridor. We demonstrate that numerical simulations of electrical resistivity studies of the stream/hyporheic boundary can help constrain volumes and rates of mobile-immobile mass transfer. We conclude with directions for future research applying electrical geophysics to understand field-scale transport in aquifer and fluvial systems subject to rate-limited mass transfer.

  4. Electrical characterization of non-Fickian transport in groundwater and hyporheic systems

    USGS Publications Warehouse

    Singha, K.; Pidlisecky, A.; Day-Lewis, F. D.; Gooseff, M.N.

    2010-01-01

    Recent work indicates that processes controlling solute mass transfer between mobile and less mobile domains in porous media may be quantified by combining electrical geophysical methods and electrically conductive tracers. Whereas direct geochemical measurements of solute preferentially sample the mobile domain, electrical geophysical methods are sensitive to changes in bulk electrical conductivity (bulk EC) and therefore sample EC in both the mobile and immobile domains. Consequently, the conductivity difference between direct geochemical samples and remotely sensed electrical geophysical measurements may provide an indication of mass transfer rates and mobile and immobile porosities in situ. Here we present (1) an overview of a theoretical framework for determining parameters controlling mass transfer with electrical resistivity in situ; (2) a review of a case study estimating mass transfer processes in a pilot-scale aquifer storage recovery test; and (3) an example application of this method for estimating mass transfer in watershed settings between streams and the hyporheic corridor. We demonstrate that numerical simulations of electrical resistivity studies of the stream/hyporheic boundary can help constrain volumes and rates of mobile-immobile mass transfer. We conclude with directions for future research applying electrical geophysics to understand field-scale transport in aquifer and fluvial systems subject to rate-limited mass transfer.

  5. Anomalous Structural Transition and Electrical Transport Behaviors in Compressed Zn2SnO4: Effect of Interface

    PubMed Central

    Zhang, Haiwa; Ke, Feng; Li, Yan; Wang, Li; Liu, Cailong; Zeng, Yi; Yao, Mingguang; Han, Yonghao; Ma, Yanzhang; Gao, Chunxiao

    2015-01-01

    The interface effect is one of the most important factors that strongly affect the structural transformations and the properties of nano-/submicro-crystals under pressure. However, characterization of the granular boundary changes in materials is always challenging. Here, using tetrakaidecahedral Zn2SnO4 microcrystals as an example, we employed alternating current impedance, X-ray diffraction methods and transmission electron microscopy to elucidate the effect of the interface on the structure and electrical transport behavior of the Zn2SnO4 material under pressure. We clearly show that grain refinement of the initial microcrystals into nanocrystals (approximately 5 nm) occurs at above 12.5 GPa and is characterized by an anomalous resistance variation without a structural phase transition. A new phase transition pathway from the cubic to hexagonal structure occurs at approximately 29.8 GPa in Zn2SnO4. The unexpected grain refinement may explain the new structural transition in Zn2SnO4, which is different from the previous theoretical prediction. Our results provide new insights into the link between the structural transition, interface changes and electrical transport properties of Zn2SnO4. PMID:26399167

  6. Temperature dependence of the electrical properties of all-inorganic, nanocrystal solar cells

    NASA Astrophysics Data System (ADS)

    Rodriguez, Yvonne W.

    Increased efficiency while keeping manufacturing costs down is the goal of next-generation photovoltaics. Studying the temperature dependence of the electrical properties of solar cell devices helps to determine how materials, device structures and transport properties affect the photovoltaic characteristics that determine device efficiency. This study focused on understanding the junction dynamics and current limiting mechanisms in CdTe and CdTe/CdSe solar cells. Electrical properties and recombination mechanisms were characterized in the temperature range of 150-376 K. The short-circuit current density in the ITO/CdTe/CdSe/Al devices increased with increasing temperature indicating thermally activated hopping with an activation energy of 45 meV. The open circuit voltage increased with decreasing temperature and the extrapolation to the zero kelvin value reveals that interface recombination is the limiting mechanism with an interface barrier height of 1.02 eV. In the dark, the dominant current limiting mechanism is tunneling enhanced bulk recombination, with a tunneling energy of 55 meV and a distribution of recombination centers with a characteristic energy of 159 meV. The CdTe devices form shottky barriers with values of 840 meV at the CdTe/Al interface and 629 meV at the ITO/CdTe interface. Tunneling enhanced interface recombination is the dominant transport mechanism and the characteristic tunneling energy is 120 meV. The CdTe/CdSe devices have been fit to a model that is based on the shockley diode theory and includes a spacecharge region due to depletion. Based on this, and the fact that a CeTe-only device exhibits photovoltaic properties, we conclude that this is not a donor-acceptor cell as previous reports suggest.

  7. Design of electrical conductive composites: tuning the morphology to improve the electrical properties of graphene filled immiscible polymer blends.

    PubMed

    Mao, Cui; Zhu, Yutian; Jiang, Wei

    2012-10-24

    Polystyrene (PS) and poly(methyl methacrylate) (PMMA) blends filled with octadecylamine-functionalized graphene (GE-ODA) have been fabricated to obtain conductive composites with a lower electrical percolation threshold according to the concept of double percolation. The dependence of the electrical properties of the composites on the morphology is examined by changing the proportion of PS and PMMA. Our results reveal that the electrical conductivity of the composites can be optimal when PS and PMMA phases form a cocontinuous structure and GE-ODA nanosheets are selectively located and percolated in the PS phase. For the PS/PMMA blend (50w/50w), the composites exhibit an extremely low electrical percolation threshold (0.5 wt %) because of the formation of a perfect double percolated structure. Moreover, the rheological properties of the composites are also measured to gain a fundamental understanding of the relationship between microstructure and electrical properties.

  8. Cross-plane electrical and thermal transport in oxide metal/semiconductor superlattices

    NASA Astrophysics Data System (ADS)

    Jha, Pankaj

    Perovskite oxides display a rich variety of electronic properties as metals, ferroelectrics, ferromagnetics, multiferroics, and thermoelectrics. Cross-plane electron filtering transport in metal/semiconductor superlattices provides a potential approach to increase the thermoelectric figure of merit (ZT). La0.67Sr0.33MnO3 (LSMO) and LaMnO3 (LMO) thin-film depositions were optimized using pulsed laser deposition (PLD) to achieve low resistivity constituent materials for LSMO/LMO superlattice heterostructures on (100)-strontium titanate (STO) substrates. X-ray diffraction and high-resolution reciprocal space mapping (RSM) indicate that the superlattices are epitaxial and pseudomorphic. Cross-plane devices were fabricated by etching cylindrical pillar structures in superlattices using inductively-coupled-plasma reactive-ion etching. The cross-plane electrical conductivity data for LSMO/LMO superlattices reveal an effective barrier height of 220 meV. The cross-plane LSMO/LMO superlattices showed a giant Seebeck coefficient of 2560 microV/K at 300K that increases to 16640 microV/K at 360K. The large Seebeck coefficient may arise due to hot electron and spin filtering as LSMO/LMO superlattice constituent materials exhibit spintronic properties where charges and spin current are intertwined and can generate a spin-Seebeck effect. The room temperature thermal conductivity achieved in low resistivity superlattices was 0.92 W/mK, which indicates that cross-plane phonon scattering at interfaces reduces the lattice contribution to the thermal conductivity. The giant contribution of spin-Seebeck, the large temperature dependence of the cross-plane power factor, and the low thermal conductivity in low resistance LSMO/LMO superlattices may offer opportunities to realize spin-magnetic thermoelectric devices, and suggests a direction for further investigations of the potential of LSMO/LMO oxide superlattices for thermoelectric devices.

  9. Transport properties of anyons in random topological environments

    NASA Astrophysics Data System (ADS)

    Zatloukal, V.; Lehman, L.; Singh, S.; Pachos, J. K.; Brennen, G. K.

    2014-10-01

    The quasi-one-dimensional transport of Abelian and non-Abelian anyons is studied in the presence of a random topological background. In particular, we consider the quantum walk of an anyon that braids around islands of randomly filled static anyons of the same type. Two distinct behaviors are identified. We analytically demonstrate that all types of Abelian anyons localize purely due to the statistical phases induced by their random anyonic environment. In contrast, we numerically show that non-Abelian Ising anyons do not localize. This is due to their entanglement with the anyonic environment, which effectively induces dephasing. Our study demonstrates that localization properties strongly depend on nonlocal topological interactions, and it provides a clear distinction in the transport properties of Abelian and non-Abelian anyons.

  10. Transport properties of β-FeSi2

    NASA Astrophysics Data System (ADS)

    Arushanov, Ernest; Lisunov, Konstantin G.

    2015-07-01

    The aim of this paper is to summarize considerable experimental efforts undertaken within the last decades in the investigations of transport properties of β-FeSi2. The β-FeSi2 compound is the most investigated among a family of semiconducting silicides. This material has received considerable attention as an attractive material for optoelectronic, photonics, photovoltaics and thermoelectric applications. Previous reviews of the transport properties of β-FeSi2 have been given by Lange and Ivanenko et al. about 15 years ago. The Hall effect, the conductivity, the mobility and the magnetoresistance data are presented. Main attention is paid to the discussion of the impurity (defect) band conductivity, the anomalous Hall effect, the scattering mechanisms of charge carriers, as well as to the hopping conduction and the magnetoresistance.

  11. Volume transport and property distributions of the Mozambique Channel

    NASA Astrophysics Data System (ADS)

    DiMarco, Steven F.; Chapman, Piers; Nowlin, Worth D.; Hacker, Peter; Donohue, Kathleen; Luther, Mark; Johnson, Gregory C.; Toole, John

    We summarize previous estimates of volume transport and property distributions through the Mozambique Channel and offer additional estimates and measurements based on recently acquired hydrographic and float data. Previously published property distributions are consistent with southward spreading through the Channel. Waters of the Mozambique Channel are characterized by shallow and intermediate oxygen minima separated by a relative maximum. Based on hydrographic sections, the intermediate maximum in dissolved oxygen is seen to decrease in value as it spreads southward. The highest values are found in the westward flow of the South Equatorial Current just north of Madagascar and within the western 200 km of the Channel. Similarly, oxygen concentrations at the intermediate oxygen minimum, which derives from the Arabian Sea, increase southwards, while its depth increases from 900 to 1100 m, supporting previous studies and indicating southward spreading and mixing along the Mozambique Channel. Historical transports based on hydrographic data in the Channel vary from 5 Sv northward to 26 Sv southward depending on reference level and time of the year. Balancing transport below 2500 m (the sill depth in the Channel), we estimate the net southward transports above this depth to be 29.1 and 5.9 Sv for the northern and southern sections, respectively—the difference is presumably related to seasonality and eddy variability superimposed on the mean flow. Individual deep float trajectories show the presence of many eddies, but the overall flow in the channel is southward, and broadly consistent with hydrography. Model outputs also show mean southward transport with considerable seasonal variability. Satellite data show high variability in sea surface height anomalies and high eddy kinetic energy associated with eddy activity. Although the geostrophic transport values are consistent with the historical limits, the lowered ADCP measurements suggest a substantial barotropic

  12. CALIPSO observations of changes in dust properties during transatlantic transport

    NASA Astrophysics Data System (ADS)

    Marshak, A.; Yang, W.; Varnai, T.; Kostinski, A. B.

    2015-12-01

    The vertical distribution of dust shape and size is highly important for understanding and estimating dust radiative forcing. We used CALIPSO nighttime datasets to examine the vertical structure and evolution of Saharan dust during transatlantic transport. The results show that most Saharan dust is lifted to high altitude and descends after traveling thousands of km-s. Initially, the depolarization ratio and color ratio of Saharan dust are uniformly distributed along altitude, suggesting vertically constant particle size and shape distributions. During transport, the depolarization ratio of Saharan dust drops at lower altitudes, suggesting that particle shapes become less irregular; while at relatively high altitudes, the depolarization ratio of dust increases during transport. The changes observed during transport likely come from the effects of gravitational sorting caused by variations in particle shape and size. A simple model with only two shapes qualitatively captures these features and confirms that shape-induced differential settling contribute significantly to the observed vertical stratification of dust properties. In addition, the effect of clouds on dust properties will be also discussed.

  13. Dispersed solar thermal generation employing parabolic dish-electric transport with field modulated generator systems

    NASA Technical Reports Server (NTRS)

    Ramakumar, R.; Bahrami, K.

    1981-01-01

    This paper discusses the application of field modulated generator systems (FMGS) to dispersed solar-thermal-electric generation from a parabolic dish field with electric transport. Each solar generation unit is rated at 15 kWe and the power generated by an array of such units is electrically collected for insertion into an existing utility grid. Such an approach appears to be most suitable when the heat engine rotational speeds are high (greater than 6000 r/min) and, in particular, if they are operated in the variable speed mode and if utility-grade a.c. is required for direct insertion into the grid without an intermediate electric energy storage and reconversion system. Predictions of overall efficiencies based on conservative efficiency figures for the FMGS are in the range of 25 per cent and should be encouraging to those involved in the development of cost-effective dispersed solar thermal power systems.

  14. Structural and Electrical Properties of Heteroepitaxial Magnetic Oxide Junction Diode Fabricated by Pulsed Laser Deposition

    NASA Astrophysics Data System (ADS)

    Li, M. K.; Wong, K. H.

    2010-11-01

    Heteroepitaxial junctions formed by p-type strontium doped lanthanum manganite and n-type cobalt doped titanium dioxide were fabricated on LaAlO3 (100) substrates by pulsed laser deposition. The La0.7Sr0.3MnO3 (LSMO) layers were grown at 650° C and under 150 mTorr ambient oxygen pressure. They showed room temperature ferromagnetism and metallic-like electrical conduction with a resistivity of 0.015 ohm cm at 300 K. The CoxTi1-xO2[x = 0.05 and 0.1] (CTO), which, at anatase phase, was reported as a wide-band-gap dilute magnetic semiconductor, was deposited on the LSMO film surface at 600° C with an ambient oxygen pressure of 20 mTorr. The as-grown CTO films exhibited pure anatase crystalline phase and semiconductor-like conduction. Under optimized fabrication conditions the CTO/LSMO junction revealed a heteroepitaxial relationship of (004)CTO‖‖(001)LSMO‖‖(001)LAO. Electrical characterization of these p-n junctions yielded excellent rectifying characteristics with a current rectifying ratio over 1000 at room temperature. The electrical transport across these diodes was dominated by diffusion current at low current (low bias voltage) regime and by recombination current at high current (high bias voltage) regime. Our results have demonstrated an all-oxide spintronic junction diode with good transport property. The simultaneous of electrical and magnetic modulation in a diode junction is therefore potentially realizable.

  15. Viscoelastic properties of actin networks influence material transport

    NASA Astrophysics Data System (ADS)

    Stam, Samantha; Weirich, Kimberly; Gardel, Margaret

    2015-03-01

    Directed flows of cytoplasmic material are important in a variety of biological processes including assembly of a mitotic spindle, retraction of the cell rear during migration, and asymmetric cell division. Networks of cytoskeletal polymers and molecular motors are known to be involved in these events, but how the network mechanical properties are tuned to perform such functions is not understood. Here, we construct networks of either semiflexible actin filaments or rigid bundles with varying connectivity. We find that solutions of rigid rods, where unimpeded sliding of filaments may enhance transport in comparison to unmoving tracks, are the fastest at transporting network components. Entangled solutions of semiflexible actin filaments also transport material, but the entanglements provide resistance. Increasing the elasticity of the actin networks with crosslinking proteins slows network deformation further. However, the length scale of correlated transport in these networks is increased. Our results reveal how the rigidity and connectivity of biopolymers allows material transport to occur over time and length scales required for physiological processes. This work was supported by the U. Chicago MRSEC

  16. Magneto transport in crossed electric and magnetic fields in compensated bulk GaN

    NASA Astrophysics Data System (ADS)

    Syngayivska, G. I.; Korotyeyev, V. V.; Kochelap, V. A.; Varani, L.

    2016-09-01

    Low-temperature high-field electron transport is studied for compensated bulk GaN subjected to crossed electric and magnetic fields. The electron kinetics, distribution function, and field dependencies of the magneto transport characteristics are analyzed by using the Monte-Carlo method. At zero magnetic field, for an ionized impurity concentration of 1016 cm-3 and an electron concentration of 1015 cm-3, it is shown that dissipative streaming transport with a strong anisotropic electron distribution in the momentum space is realized at electric fields in the range 3 -10 kV/cm and for a lattice temperature of 30 K. The magnetic field destroys the dissipative streaming transport. Indeed, for a magnetic field greater than 4 T, the electrons are predominantly confined in a region of the momentum space where their energy is smaller than the optical phonon energy and the strong inelastic scattering by optical phonons is practically eliminated. A quasi-ballistic electron transport occurs in the form of a vortex-like motion in the momentum space. The axis of rotation of this vortex coincides with the average electron momentum. A general analysis of the distribution function suitable for any configuration of the Hall circuit is presented. The main magneto transport characteristics (dissipative current, Hall current, and Hall electric field) are studied for the short and open Hall circuits. We show that the magneto transport measurements can provide valuable information on the main features of the electron distribution function and electron dynamics in GaN. Finally, we suggest that the strong dependency of the dissipative current on the parameters of the Hall circuit can be used for current modulation and current switching.

  17. Structural and electrical properties of evaporated Fe thin films

    NASA Astrophysics Data System (ADS)

    Mebarki, M.; Layadi, A.; Guittoum, A.; Benabbas, A.; Ghebouli, B.; Saad, M.; Menni, N.

    2011-06-01

    Series of Fe thin films have been prepared by thermal evaporation onto glass and Si(1 0 0) substrates. The Rutherford backscattering (RBS), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and the four point probe techniques have been used to investigate the structural and electrical properties of these Fe thin films as a function of the substrate, the Fe thickness t in the 76-431 nm range and the deposition rate. The Fe/Si samples have a <1 1 0> for all thicknesses, whereas the Fe/glass grows with a strong <1 0 0> texture; as t increases (>100 nm), the preferred orientation changes to <1 1 0>. The compressive stress in Fe/Si remains constant over the whole thickness range and is greater than the one in Fe/glass which is relieved when t > 100 nm. The grain size D values are between 9.2 and 30 nm. The Fe/glass films are more electrically resistive than the Fe/Si(1 0 0) ones. Diffusion at the grain boundary seems to be the predominant factor in the electrical resistivity ρ values with the reflection coefficient R greater in Fe/glass than in Fe/Si. For the same thickness (100 nm), the decrease of the deposition rate from 4.3 to 0.3 Å/s did not affect the texture and the reflection coefficient R but led to an increase in D and a decrease in the strain and in ρ for both Fe/glass and Fe/Si systems. On the other hand, keeping the same deposition rate (0.3 Å/s) and increasing the thickness t from 76 to 100 nm induced different changes in the two systems.

  18. Ion confinement and transport in a toroidal plasma with externally imposed radial electric fields

    NASA Technical Reports Server (NTRS)

    Roth, J. R.; Krawczonek, W. M.; Powers, E. J.; Kim, Y. C.; Hong, H. Y.

    1979-01-01

    Strong electric fields were imposed along the minor radius of the toroidal plasma by biasing it with electrodes maintained at kilovolt potentials. Coherent, low-frequency disturbances characteristic of various magnetohydrodynamic instabilities were absent in the high-density, well-confined regime. High, direct-current radial electric fields with magnitudes up to 135 volts per centimeter penetrated inward to at least one-half the plasma radius. When the electric field pointed radially toward, the ion transport was inward against a strong local density gradient; and the plasma density and confinement time were significantly enhanced. The radial transport along the electric field appeared to be consistent with fluctuation-induced transport. With negative electrode polarity the particle confinement was consistent with a balance of two processes: a radial infusion of ions, in those sectors of the plasma not containing electrodes, that resulted from the radially inward fields; and ion losses to the electrodes, each of the which acted as a sink and drew ions out of the plasma. A simple model of particle confinement was proposed in which the particle confinement time is proportional to the plasma volume. The scaling predicted by this model was consistent with experimental measurements.

  19. Calculation of effective transport properties of partially saturated gas diffusion layers

    NASA Astrophysics Data System (ADS)

    Bednarek, Tomasz; Tsotridis, Georgios

    2017-02-01

    A large number of currently available Computational Fluid Dynamics numerical models of Polymer Electrolyte Membrane Fuel Cells (PEMFC) are based on the assumption that porous structures are mainly considered as thin and homogenous layers, hence the mass transport equations in structures such as Gas Diffusion Layers (GDL) are usually modelled according to the Darcy assumptions. Application of homogenous models implies that the effects of porous structures are taken into consideration via the effective transport properties of porosity, tortuosity, permeability (or flow resistance), diffusivity, electric and thermal conductivity. Therefore, reliable values of those effective properties of GDL play a significant role for PEMFC modelling when employing Computational Fluid Dynamics, since these parameters are required as input values for performing the numerical calculations. The objective of the current study is to calculate the effective transport properties of GDL, namely gas permeability, diffusivity and thermal conductivity, as a function of liquid water saturation by using the Lattice-Boltzmann approach. The study proposes a method of uniform water impregnation of the GDL based on the "Fine-Mist" assumption by taking into account the surface tension of water droplets and the actual shape of GDL pores.

  20. Electrical properties of sub-100 nm SiGe nanowires

    NASA Astrophysics Data System (ADS)

    Hamawandi, B.; Noroozi, M.; Jayakumar, G.; Ergül, A.; Zahmatkesh, K.; Toprak, M. S.; Radamson, H. H.

    2016-10-01

    In this study, the electrical properties of SiGe nanowires in terms of process and fabrication integrity, measurement reliability, width scaling, and doping levels were investigated. Nanowires were fabricated on SiGe-on oxide (SGOI) wafers with thickness of 52 nm and Ge content of 47%. The first group of SiGe wires was initially formed by using conventional I-line lithography and then their size was longitudinally reduced by cutting with a focused ion beam (FIB) to any desired nanometer range down to 60 nm. The other nanowire group was manufactured directly to a chosen nanometer level by using sidewall transfer lithography (STL). It has been shown that the FIB fabrication process allows manipulation of the line width and doping level of nanowires using Ga atoms. The resistance of wires thinned by FIB was 10 times lower than STL wires which shows the possible dependency of electrical behavior on fabrication method. Project support by the Swedish Foundation for Strategic Research “SSF” (No. EM-011-0002) and the Scientific and Technological Research Council of Turkey (No. TÜBİTAK).

  1. SHI induced damage in electrical properties of silicon NPN BJTs

    NASA Astrophysics Data System (ADS)

    Kumar, M. Vinay; Kumar, Santhosh; Yashoda, T.; Krishnaveni, S.

    2016-05-01

    The investigation of radiation damage in Si microelectronic circuitry and devices are being carried out by various research groups globally. In particular the Si Bipolar junction transistors are very sensitive to high energetic radiation. In the present study, radiation response of NPN Bipolar junction transistor (2N3773) has been examined for 60 MeV B4+ ion. Key electrical properties like Gummel, dc current gain and capacitance - voltage (C-V) characteristics of 60 MeV B4+ ion irradiated transistor were studied before and after irradiation. Ion irradiation and subsequent electrical characterizations were performed at room temperature. Current voltage (I-V) measurements showed the increase in collector current for VBE ≤ 0.4 V as a function of fluence, which is due to B4+ ion induced surface leakage currents. Base current is observed to be more sensitive than collector current and gain appears to be degraded with ion fluence. Also, C-V measurements shows that both built in potential and doping concentration increased significantly after irradiation.

  2. THE STABILITY AND ELECTRICAL PROPERTIES OF HIGH TEMPERATURE PROTON CONDUCTORS

    SciTech Connect

    Brinkman, K.

    2010-07-06

    The morphological and electrical properties of Ba{sub 1-x}Sr{sub x}Ce{sub 0.8}Y{sub 0.2}O{sub 3-{delta}} with x varying from 0 to 1 prepared by a modified Pechini method were investigated as potential high temperature proton conductors. Dense microstructures were achieved for all the samples upon sintering at 1500 C for 5 h. The phase structure analysis indicated that perovskite phase was formed for 0 {le} x {le} 0.2, while for x larger than 0.5, impurity phases of Sr{sub 2}CeO{sub 4} and Y{sub 2}O{sub 3} appeared. The tolerance to H{sub 2}O for the samples improved with the increase in Sr content when exposed to boiling water, while the electrical conductivity decreased from x = 0 to 1. However, the resistance to CO{sub 2} attack at elevated temperatures was not improved within the whole x range studied.

  3. Electrical properties of dispersions of graphene in mineral oil

    SciTech Connect

    Monteiro, O. R.

    2014-02-03

    Dispersions of graphene in mineral oil have been prepared and electrical conductivity and permittivity have been measured. The direct current (DC) conductivity of the dispersions depends on the surface characteristics of the graphene platelets and followed a percolation model with a percolation threshold ranging from 0.05 to 0.1 wt. %. The difference in DC conductivities can be attributed to different states of aggregation of the graphene platelets and to the inter-particle electron transfer, which is affected by the surface radicals. The frequency-dependent conductivity (σ(ω)) and permittivity (ε(ω)) were also measured. The conductivity of dispersions with particle contents much greater than the percolation threshold remains constant and equal to the DC conductivity at low frequencies ω with and followed a power-law σ(ω)∝ ω{sup s} dependence at very high frequencies with s≈0.9. For dispersions with graphene concentration near the percolation threshold, a third regime was displayed at intermediate frequencies indicative of interfacial polarization consistent with Maxwell-Wagner effect typically observed in mixtures of two (or more) phases with very distinct electrical and dielectric properties.

  4. Electrical Conductivity and Dielectrical Properties of Bulk Methylene Green

    NASA Astrophysics Data System (ADS)

    El-Menyawy, E. M.; Zedan, I. T.; Mansour, A. M.

    2017-03-01

    Thermal stability, direct current electrical conductivity (σ DC), alternating current electrical conductivity (σ AC) and dielectric properties of bulk methylene green (MG) have been investigated. The thermal stability of MG was studied by differential scanning calorimetry and thermogravimetry techniques. Temperature dependence of σ DC showed that the MG has semiconductor behavior with two activation energies determined as 0.12 eV and 0.31 eV in the temperature range 303-343 K and 363-463 K, respectively. The σ AC of bulk MG was performed in the frequency range 150 Hz-5 MHz and temperature range 303-463 K. The dependence of AC conductivity on frequency for MG is found to satisfy Jonscher's universal power law, especially at high frequencies. The correlated barrier hopping model is found to be applicable in which the density of localized states is determined. The σ AC is thermally activated and the activation energy decreases with the increases in frequency. The variation of the real and imaginary parts of the dielectric constant with the frequency and temperature is explained.

  5. Understanding electric field-enhanced transport for the measurement of nanoparticles and their assembly on surfaces

    NASA Astrophysics Data System (ADS)

    Tsai, De-Hao

    The goal of this dissertation is to understand the synthesis, characterization, and integration of nanoparticles and nanoparticle-based devices by electric field-enhanced transport of nanoparticles. Chapter I describes the factors used for determining particle trajectories and found that electric fields provide the directional electrostatic force to overcome other non-directional influences on particle trajectories. This idea is widely applied in the nanoparticle classification, characterization, and assembly onto substrate surfaces as investigated in the following chapters. Chapter 2 presents a new assembly method to position metal nanoparticles delivered from the gas phase onto surfaces using the electrostatic force generated by biased p-n junction patterned substrates. Aligned deposition patterns of metal nanoparticles were observed, and the patterning selectivity quantified. A simple model accounting for the generated electric field, and the electrostatic, van der Waals, and image forces was used to explain the observed results. Chapter 2.2 describes a data set for particle size resolved deposition, from which a Brownian dynamics model for the process can be evaluated. Brownian motion and fluid convection of nanoparticles, as well as the interactions between the charged nanoparticles and the patterned substrate, including electrostatic force, image force and van der Waals force, are accounted for in the simulation. Using both experiment and simulation the effects of the particle size, electric field intensity, and the convective flow on coverage selectivity have been investigated. Coverage selectivity is most sensitive to electric field, which is controlled by the applied reverse bias voltage across the p-n junction. A non-dimensional analysis of the competition between the electrostatic and diffusion force is found to provide a means to collapse a wide range of process operating conditions and an effective indicator or process performance. Directed assembly of

  6. Two-Dimensional Porous Carbon: Synthesis and Ion-Transport Properties.

    PubMed

    Zheng, Xiaoyu; Luo, Jiayan; Lv, Wei; Wang, Da-Wei; Yang, Quan-Hong

    2015-09-23

    Their chemical stability, high specific surface area, and electric conductivity enable porous carbon materials to be the most commonly used electrode materials for electrochemical capacitors (also known as supercapacitors). To further increase the energy and power density, engineering of the pore structures with a higher electrochemical accessible surface area, faster ion-transport path and a more-robust interface with the electrolyte is widely investigated. Compared with traditional porous carbons, two-dimensional (2D) porous carbon sheets with an interlinked hierarchical porous structure are a good candidate for supercapacitors due to their advantages in high aspect ratio for electrode packing and electron transport, hierarchical pore structures for ion transport, and short ion-transport length. Recent progress on the synthesis of 2D porous carbons is reported here, along with the improved electrochemical behavior due to enhanced ion transport. Challenges for the controlled preparation of 2D porous carbons with desired properties are also discussed; these require precise tuning of the hierarchical structure and a clarification of the formation mechanisms.

  7. Electrical and magnetic properties of ion-exchangeable layered ruthenates

    SciTech Connect

    Sugimoto, Wataru . E-mail: wsugi@shinshu-u.ac.jp; Omoto, Masashi; Yokoshima, Katsunori; Murakami, Yasushi; Takasu, Yoshio

    2004-12-01

    An ion-exchangeable ruthenate with a layered structure, K{sub 0.2}RuO{sub 2.1}, was prepared by solid-state reactions. The interlayer cation was exchanged with H{sup +}, C{sub 2}H{sub 5}NH{sub 3}{sup +}, and ((C{sub 4}H{sub 9}){sub 4}N{sup +}) through proton-exchange, ion-exchange, and guest-exchange reactions. The electrical and magnetic properties of the products were characterized by DC resistivity and susceptibility measurements. Layered K{sub 0.2}RuO{sub 2.1} exhibited metallic conduction between 300 and 13K. The products exhibited similar magnetic behavior despite the differences in the type of interlayer cation, suggesting that the ruthenate sheet in the protonated form and the intercalation compounds possesses metallic nature.

  8. Nanofibrous Silver-Coated Polymeric Scaffolds with Tunable Electrical Properties

    PubMed Central

    Memic, Adnan; Aldhahri, Musab; Tamayol, Ali; Mostafalu, Pooria; Abdel-wahab, Mohamed Shaaban; Samandari, Mohamadmahdi; Moghaddam, Kamyar Mollazadeh; Annabi, Nasim; Bencherif, Sidi A.; Khademhosseini, Ali

    2017-01-01

    Electrospun micro- and nanofibrous poly(glycerol sebacate)-poly(ε-caprolactone) (PGS-PCL) substrates have been extensively used as scaffolds for engineered tissues due to their desirable mechanical properties and their tunable degradability. In this study, we fabricated micro/nanofibrous scaffolds from a PGS-PCL composite using a standard electrospinning approach and then coated them with silver (Ag) using a custom radio frequency (RF) sputtering method. The Ag coating formed an electrically conductive layer around the fibers and decreased the pore size. The thickness of the Ag coating could be controlled, thereby tailoring the conductivity of the substrate. The flexible, stretchable patches formed excellent conformal contact with surrounding tissues and possessed excellent pattern-substrate fidelity. In vitro studies confirmed the platform’s biocompatibility and biodegradability. Finally, the potential controlled release of the Ag coating from the composite fibrous scaffolds could be beneficial for many clinical applications. PMID:28336896

  9. Structural and electrical properties of In-implanted Ge

    SciTech Connect

    Feng, R. Kremer, F.; Mirzaei, S.; Medling, S. A.; Ridgway, M. C.; Sprouster, D. J.; Decoster, S.; Glover, C. J.; Russo, S. P.

    2015-10-28

    We report on the effects of dopant concentration on the structural and electrical properties of In-implanted Ge. For In concentrations of ≤ 0.2 at. %, extended x-ray absorption fine structure and x-ray absorption near-edge structure measurements demonstrate that all In atoms occupy a substitutional lattice site while metallic In precipitates are apparent in transmission electron micrographs for In concentrations ≥0.6 at. %. Evidence of the formation of In-vacancy complexes deduced from extended x-ray absorption fine structure measurements is complimented by density functional theory simulations. Hall effect measurements of the conductivity, carrier density, and carrier mobility are then correlated with the substitutional In fraction.

  10. Structural and electrical properties of In-implanted Ge

    DOE PAGES

    Feng, R.; Kremer, F.; Sprouster, D. J.; ...

    2015-10-22

    Here, we report on the effects of dopant concentration on the structural and electrical properties of In-implanted Ge. For In concentrations of ≤ 0.2 at. %, extended x-ray absorption fine structure and x-ray absorption near-edge structure measurements demonstrate that all In atoms occupy a substitutional lattice site while metallic In precipitates are apparent in transmission electron micrographs for In concentrations ≥0.6 at. %. Evidence of the formation of In-vacancy complexes deduced from extended x-ray absorption fine structure measurements is complimented by density functional theory simulations. Hall effect measurements of the conductivity, carrier density, and carrier mobility are then correlated withmore » the substitutional In fraction.« less

  11. Structural and electrical properties of In-implanted Ge

    SciTech Connect

    Feng, R.; Kremer, F.; Sprouster, D. J.; Mirzaei, S.; Decoster, S.; Glover, C. J.; Medling, S. A.; Russo, S. P.; Ridgway, M. C.

    2015-10-22

    Here, we report on the effects of dopant concentration on the structural and electrical properties of In-implanted Ge. For In concentrations of ≤ 0.2 at. %, extended x-ray absorption fine structure and x-ray absorption near-edge structure measurements demonstrate that all In atoms occupy a substitutional lattice site while metallic In precipitates are apparent in transmission electron micrographs for In concentrations ≥0.6 at. %. Evidence of the formation of In-vacancy complexes deduced from extended x-ray absorption fine structure measurements is complimented by density functional theory simulations. Hall effect measurements of the conductivity, carrier density, and carrier mobility are then correlated with the substitutional In fraction.

  12. Electrical Property of Conventionally Sintered ZnO

    NASA Astrophysics Data System (ADS)

    Tak, S. K.; Shekhwat, M. S.; Mangal, R.

    ZnO powder was synthesized by solid state reaction method. The synthesized powder was granulated and pressed using uni-axial press for preparing the pallets. The prepared pellets were sintered in conventional furnace at different temperatures (900-1300° C). The phase study was done by powder X-ray diffraction and it was found that the there is no other phase present in the synthesized material but the peak intensity is increasing with temperature. The crystallite size of the synthesized ZnO powder was found to be increase with temperature. The effect of sintering on grain growth is investigated by scanning electron microscopy (SEM). SEM revels that the average grain size is increases with increase in sintering temperature. AC impedance of these samples was decreased markedly with increased sintering temperature. In present work the effect of sintering temperatures and hold time on micro structural and electrical properties of ZnO ceramics is carried out.

  13. Note on electrical and thermodynamic properties of isolated horizons

    NASA Astrophysics Data System (ADS)

    Chen, Gerui; Wu, Xiaoning; Gao, Sijie

    2015-03-01

    The electrical laws and Carnot cycle of isolated horizons (IH) are investigated in this paper. We establish Ohm's law and Joule's law of isolated horizons and find that the conceptual picture of black holes (membrane paradigm) can also apply to this kind of quasilocal black holes. We also investigate the geometrical properties near nonrotating IHs and find that under the first-order approximation of r , there exist a Killing vector ∂∂u/ and a Hamiltonian conjugate to it, so this vector can be thought to be a physical observer. We calculate the energy as measured at infinity of a particle at rest outside a nonrotating IH, and we use this result to construct a reversible Carnot cycle with the isolated horizon as a cold reservoir, which confirms the thermodynamic nature of isolated horizons.

  14. Single-step electrical field strength screening to determine electroporation induced transmembrane transport parameters.

    PubMed

    Blumrosen, Gadi; Abazari, Alireza; Golberg, Alexander; Yarmush, Martin L; Toner, Mehmet

    2016-09-01

    The design of effective electroporation protocols for molecular delivery applications requires the determination of transport parameters including diffusion coefficient, membrane resealing, and critical electric field strength for electroporation. The use of existing technologies to determine these parameters is time-consuming and labor-intensive, and often results in large inconsistencies in parameter estimation due to variations in the protocols and setups. In this work, we suggest using a set of concentric electrodes to screen a full range of electric field strengths in a single test to determine the electroporation-induced transmembrane transport parameters. Using Calcein as a fluorescent probe, we developed analytical methodology to determine the transport parameters based on the electroporation-induced pattern of fluorescence loss from cells. A monolayer of normal human dermal fibroblast (NHDF) cells were pre-loaded with Calcein and electroporated with an applied voltage of 750V with 10 and 50 square pulses with 50μs duration. Using our analytical model, the critical electric field strength for electroporation was found for the 10 and 50 pulses experiments. An inverse correlation between the field strength and the molecular transport time decay constant, and a direct correlation between field strength and the membrane permeability were observed. The results of this work can simplify the development of electroporation-assisted technologies for research and therapies.

  15. Durability assessments of concrete using electrical properties and acoustic emission testing

    NASA Astrophysics Data System (ADS)

    Todak, Heather N.

    Premature damage deterioration has been observed in pavement joints throughout the Midwestern region of the United States. Over time, severe joint damage creates a transportation safety concern and the necessary repairs can be an extreme economic burden. The deterioration is due in part to freeze-thaw damage associated with fluid accumulation at the pavement joints. This very preventable problem is an indication that current specifications and construction practices for freeze-thaw durability of concrete are inadequate. This thesis serves to create a better understanding of moisture ingress, freeze-thaw damage mechanisms, and the effect of variations in mixture properties on freeze-thaw behavior of concrete. The concepts of the nick point degree of saturation, sorptivity rates, and critical degree of saturation are discussed. These factors contribute to service life, defined in this study as the duration of time a concrete element remains below levels of critical saturation which are required for damage development to initiate. A theoretical model and a simple experimental procedure are introduced which help determine the nick point for a series of 32 concrete mixtures with unique mixture proportions and air entrainment properties. This simple experimental procedure is also presented as a method to measure important electrical properties in order to establish the formation factor, a valuable measure of concrete transport properties. The results of freeze-thaw testing with acoustic emission monitoring are presented to help understand and quantify damage development in concrete specimens when conditioned to various degrees of saturation. This procedure was used to study the relationship between air entrainment properties and the critical degree of saturation. Applying the concepts of degree of saturation and sorptivity, a performance-based model is proposed as a new approach to specifications for freeze-thaw durability. Finally, a conceptual model is presented to

  16. Photo-transport properties of Pb{sub 2}CrO{sub 5} single crystals

    SciTech Connect

    Mondal, P. S.; Okazaki, R. Taniguchi, H.; Terasaki, I.

    2014-11-21

    We report photo-thermoelectric transport phenomena in Pb{sub 2}CrO{sub 5} single crystals. Without illumination, this material exhibits an insulating behavior characterized by an activation-type temperature variation of the electrical conductivity. The Seebeck coefficient contrastingly shows a crossover from high-temperature insulating to low-temperature metallic behavior, which is attributed to degenerate carriers in a donor level. We have found that under illumination, both the conductivity and the Seebeck coefficient increase in magnitude with increasing photon flux density in the degenerate-conduction regime. This result is difficult to understand within a simple photo-doping effect, which usually leads to a decrease in the Seebeck coefficient under illumination. The observed phenomenon is discussed in terms of a two-carrier contribution to the transport properties.

  17. Photo-transport properties of Pb2CrO5 single crystals

    NASA Astrophysics Data System (ADS)

    Mondal, P. S.; Okazaki, R.; Taniguchi, H.; Terasaki, I.

    2014-11-01

    We report photo-thermoelectric transport phenomena in Pb2CrO5 single crystals. Without illumination, this material exhibits an insulating behavior characterized by an activation-type temperature variation of the electrical conductivity. The Seebeck coefficient contrastingly shows a crossover from high-temperature insulating to low-temperature metallic behavior, which is attributed to degenerate carriers in a donor level. We have found that under illumination, both the conductivity and the Seebeck coefficient increase in magnitude with increasing photon flux density in the degenerate-conduction regime. This result is difficult to understand within a simple photo-doping effect, which usually leads to a decrease in the Seebeck coefficient under illumination. The observed phenomenon is discussed in terms of a two-carrier contribution to the transport properties.

  18. Automated system for removal and pneumatic transport of fly ash from electric precipitator hoppers

    SciTech Connect

    V.K. Konovalov; O.V. Yashkin; V.V. Ermakov

    2008-03-15

    A system for removal and pneumatic transport of fly ash is examined, in which air pulses act on batches (pistons) of ash formed in a duct. Studies are made of the effect of several physical parameters on the force required to displace a piston of ash and these serve as a basis for choosing a system for removal and pneumatic transport of ash simultaneously from several hoppers of an electric precipitator. This makes it possible to separate the ash particles according to size without introducing additional components. Formulas are given for calculating the structural and dynamic parameters of this system and measurements of indirect dynamic parameters are used to calculate the input-output characteristics of the system. In order to optimize the system, configurations for summing several ducts into a single transport duct for pneumatic ash transport are proposed. Some variants of dry ash utilization and the advantages of producing of size-separated particles are considered.

  19. Coupling mechanical forces to electrical signaling: molecular motors and the intracellular transport of ion channels.

    PubMed

    Barry, Joshua; Gu, Chen

    2013-04-01

    Proper localization of various ion channels is fundamental to neuronal functions, including postsynaptic potential plasticity, dendritic integration, action potential initiation and propagation, and neurotransmitter release. Microtubule-based forward transport mediated by kinesin motors plays a key role in placing ion channel proteins to correct subcellular compartments. PDZ- and coiled-coil-domain proteins function as adaptor proteins linking ionotropic glutamate and GABA receptors to various kinesin motors, respectively. Recent studies show that several voltage-gated ion channel/transporter proteins directly bind to kinesins during forward transport. Three major regulatory mechanisms underlying intracellular transport of ion channels are also revealed. These studies contribute to understanding how mechanical forces are coupled to electrical signaling and illuminating pathogenic mechanisms in neurodegenerative diseases.

  20. Materials Science and Materials Chemistry for Large Scale Electrochemical Energy Storage: From Transportation to Electrical Grid

    SciTech Connect

    Liu, Jun; Zhang, Jiguang; Yang, Zhenguo; Lemmon, John P.; Imhoff, Carl H.; Graff, Gordon L.; Li, Liyu; Hu, Jian Z.; Wang, Chong M.; Xiao, Jie; Xia, Guanguang; Viswanathan, Vilayanur V.; Baskaran, Suresh; Sprenkle, Vincent L.; Li, Xiaolin; Shao, Yuyan; Schwenzer, Birgit

    2013-02-15

    Large-scale electrical energy storage has become more important than ever for reducing fossil energy consumption in transportation and for the widespread deployment of intermittent renewable energy in electric grid. However, significant challenges exist for its applications. Here, the status and challenges are reviewed from the perspective of materials science and materials chemistry in electrochemical energy storage technologies, such as Li-ion batteries, sodium (sulfur and metal halide) batteries, Pb-acid battery, redox flow batteries, and supercapacitors. Perspectives and approaches are introduced for emerging battery designs and new chemistry combinations to reduce the cost of energy storage devices.