The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Jiangyu Li - One of the best experts on this subject based on the ideXlab platform.
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quantitative nanoscale mapping of three phase thermal conductivities in filled skutterudites via scanning thermal microscopy
National Science Review, 2018Co-Authors: Ehsan Nasr Esfahani, Shanyu Wang, Yun Ou, Jihui Yang, Jiangyu LiAbstract:In the last two decades, a nanostructuring paradigm has been successfully applied in a wide range of thermoelectric materials, resulting in significant reduction in thermal conductivity and superior thermoelectric performance. These advances, however, have been accomplished without directly investigating the local thermoelectric properties, even though local electric current can be mapped with high spatial resolution. In fact, there still lacks an effective method that links the macroscopic thermoelectric performance to the local microstructures and properties. Here, we show that local thermal conductivity can be mapped quantitatively with good accuracy, nanometer resolution and one-to-one correspondence to the microstructure using a three-phase skutterudite as a model system. Scanning thermal microscopy combined with finite element simulations demonstrate close correlation between sample conductivity and Probe Resistance, enabling us to distinguish thermal conductivities spanning orders of magnitude, yet resolving thermal variation across a phase interface with small contrast. The technique thus provides a powerful tool to correlate local thermal conductivities, microstructures and macroscopic properties for nanostructured materials in general and nanostructured thermoelectrics in particular.
Ehsan Nasr Esfahani - One of the best experts on this subject based on the ideXlab platform.
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quantitative nanoscale mapping of three phase thermal conductivities in filled skutterudites via scanning thermal microscopy
National Science Review, 2018Co-Authors: Ehsan Nasr Esfahani, Shanyu Wang, Yun Ou, Jihui Yang, Jiangyu LiAbstract:In the last two decades, a nanostructuring paradigm has been successfully applied in a wide range of thermoelectric materials, resulting in significant reduction in thermal conductivity and superior thermoelectric performance. These advances, however, have been accomplished without directly investigating the local thermoelectric properties, even though local electric current can be mapped with high spatial resolution. In fact, there still lacks an effective method that links the macroscopic thermoelectric performance to the local microstructures and properties. Here, we show that local thermal conductivity can be mapped quantitatively with good accuracy, nanometer resolution and one-to-one correspondence to the microstructure using a three-phase skutterudite as a model system. Scanning thermal microscopy combined with finite element simulations demonstrate close correlation between sample conductivity and Probe Resistance, enabling us to distinguish thermal conductivities spanning orders of magnitude, yet resolving thermal variation across a phase interface with small contrast. The technique thus provides a powerful tool to correlate local thermal conductivities, microstructures and macroscopic properties for nanostructured materials in general and nanostructured thermoelectrics in particular.
Bruno Lengeler - One of the best experts on this subject based on the ideXlab platform.
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Intertube coupling in ropes of single-wall carbon nanotubes
Physical review letters, 2000Co-Authors: H. Stahl, Joerg Appenzeller, Richard Martel, Phaedon Avouris, Bruno LengelerAbstract:We investigate the coupling between individual tubes in a rope of single-wall carbon nanotubes using four Probe Resistance measurements. By introducing defects through the controlled sputtering of the rope we generate a strong nonmonotonic temperature dependence of the four terminal Resistance. This behavior reflects the interplay between localization in the intentionally damaged tubes and coupling to undamaged tubes in the same rope. Using a simple model we obtain the coherence length and the coupling Resistance. The coupling mechanism is argued to involve direct tunneling between tubes.
Satoshi Watanabe - One of the best experts on this subject based on the ideXlab platform.
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Effects of resonant scattering by Probe contacts on nanoscale four-Probe Resistance measurements
New Journal of Physics, 2010Co-Authors: Asako Terasawa, Keiji Tobimatsu, Tomofumi Tada, Takahiro Yamamoto, Satoshi WatanabeAbstract:The oscillation of the four-Probe electric Resistance of monatomic carbon chains as a function of electron energy was theoretically analysed on the basis of non-equilibrium Green's function formalism and the self-consistent charge density-functional tight-binding method. We constructed spectra from the spacing of the oscillation peaks in four-Probe Resistance spectra. The interference effect caused by multiple reflections and resonant scattering at the contacts were extracted separately from the peak spacing spectra. Analysis of the peak spacing spectra may provide a powerful tool to extract information about scattering processes in four-Probe Resistance measurements.
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Theoretical study of four-Probe Resistance in nanoscale measurements: Monatomic carbon chains and (5,5)-carbon nanotubes
Physical Review B, 2009Co-Authors: Asako Terasawa, Tomofumi Tada, Satoshi WatanabeAbstract:Simulations of four-Probe Resistance measurements of monatomic carbon chains and (5,5)-carbon nanotubes were carried out using the self-consistent charge density-functional tight-binding method and the Green's function method. The four-Probe Resistance spectra show oscillations depending on the Probe geometries and become negative at specific electron energies. These features coincide qualitatively with those experimentally observed by Gao et al. [Phys. Rev. Lett. 95, 196802 (2005)]. It is shown that the Resistance oscillations can be attributed to the interference of electron waves between the two voltage Probes.
Alan T. Johnson - One of the best experts on this subject based on the ideXlab platform.
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Transport properties of a potassium-doped single-wall carbon nanotube rope
Physical Review B, 2000Co-Authors: R. S. Lee, H. J. Kim, Julia Fischer, Jacques Lefebvre, M. Radosavljevic, James Hone, Alan T. JohnsonAbstract:Four-Probe Resistance vs temperature and gate voltage are reported for an individual single-wall carbon nanotube rope before and after doping in situ with potassium. All the features in R(T) from unoriented bulk material, before and after doping, are qualitatively reproduced by the rope data. The 5.3 K conductance of the pristine rope decreases with positive gate voltage, while G vs V{sub g} becomes featureless after K doping. (c) 2000 The American Physical Society.