Search results for "conductivity"
showing 10 items of 1988 documents
Star-Shaped Conjugated Systems
2010
The present review deals with the preparation and the properties of star-shaped conjugated compounds. Three, four or six conjugated arms are attached to cross-conjugated cores, which consist of single atoms (B, C+, N), benzene or azine rings or polycyclic ring systems, as for example triphenylene or tristriazolotriazine. Many of these shape-persistent [n]star compounds tend to π-stacking and self-organization, and exhibit interesting properties in materials science: Linear and non-linear optics, electrical conductivity, electroluminescence, formation of liquid crystalline phases, etc.
Opportunity of metallic interconnects for ITSOFC : Reactivity and electrical property.
2006
International audience; Iron-base alloys (Fe-Cr) are proposed hereafter as materials for interconnect of planar-type intermediate temperature solid oxide fuel cell (ITSOFC); they are an alternative solution instead of the use of ceramic interconnects. These steels form an oxide layer (chrornia) which protects the interconnect from the exterior environment, but is an electrical insulator. One solution envisaged in this work is the deposition of a reactive element oxide coating, that slows down the formation of the oxide layer and that increases its electric conductivity. The oxide layer, formed at high temperature on the uncoated alloys, is mainly composed of chromia; it grows in accordance …
Individual arc-discharge synthesized multiwalled carbon nanotubes probed with multiple measurement techniques
2020
Arc-discharge synthesized multiwalled carbon nanotubes (AD-MWNT), or related MWNTs, exhibit a good quality compared to the more common type of MWNT synthesized by catalytic chemical vapor deposition methods. Yet experimental measurements on these are rather few and typically have not correlated data from different measurement techniques. Here, the authors report Raman spectroscopy, scanning probe microscopy, conductivity measurements, and force microscopy on single AD-MWNTs. The results demonstrate the high quality of AD-MWNTs and are compatible with the view of them as the best approximation of MWNTs as an assembly of defect-free concentric individual single-walled carbon nanotubes. The au…
Microwave photoassisted dissipation and supercurrent of a phase-biased graphene-superconductor ring
2021
Irradiating normal-superconducting junctions with microwave photons produce spectacular effects, such as Shapiro steps and photoinduced modifications of the dc supercurrent. Moreover, microwave irradiation can also have other, hitherto unexplored consequences, such as a photoassisted dissipation which is phase dependent. Here we present a finite-frequency measurement of both the dissipation and the supercurrent of a phase-biased graphene-superconductor junction in response to microwave photons. We find that, while the supercurrent response is well described by existing theory, the dissipation exhibits unexpected effects which need new theoretical elucidation. Especially with high frequency …
Low Temperature Growth of High Purity, Low Resistivity Copper Films by Atomic Layer Deposition
2011
The atomic layer deposition of copper metal thin films was achieved using a three precursor sequence entailing Cu(OCHMeCH2NMe2)2, formic acid, and hydrazine. A constant growth rate of 0.47−0.50 A/cycle was observed at growth temperatures between 100 and 170 °C. The resulting films are high purity and have low resistivities.
Tantalum nitride thin film resistors by low temperature reactive sputtering for plastic electronics
2008
This article describes the fabrication and characterisation of tantalum nitride (TaN) thin film for applications in plastic electronics. Thin films of comparable thickness (50-60 nm) have been deposited by RF-magnetron-reactive sputtering at low temperature (100 °C) and their structure and physical (electrical and mechanical) properties have been correlated by using sheet resistance, stress measurements, atomic force microscopy (AFM), XPS, and SIMS. Different film compositions have been obtained by varying the argon to nitrogen flow ratio in the sputtering chamber. XPS showed that 5:1, 2:1 and 1:1 Ar:N 2 ratios gives Ta 2 N, TaN and Ta 3 N 5 phases, respectively. Sheet resistance revealed a…
Minimizing coherent thermal conductance by controlling the periodicity of two-dimensional phononic crystals
2019
Periodic hole array phononic crystals (PnC) can strongly modify the phonon dispersion relations, and have been shown to influence thermal conductance coherently, especially at low temperatures where scattering is suppressed. One very important parameter influencing this effect is the period of the structure. Here, we measured the sub-Kelvin thermal conductance of nanofabricated PnCs with identical hole filling factors, but three different periodicities, 4, 8, and 16 $\mu$m, using superconducting tunnel junction thermometry. We found that all the measured samples can suppress thermal conductance by an order of magnitude, and have a lower thermal conductance than the previously measured small…
Conservative Averaging Method for Solutions of Inverse Problems for Heat Equation
2004
Inverse problems arise in various fields of science, technology and agriculture where from measurements of state of the system or process it is required to determine a certain typesetting of the causal characteristics. It is known that infrigement of the natural causal relationships can entail incorrectness of the mathematical formulation of inverse problem. Therefore the development of efficient methods for solving such problems allow us to simplify experimental research considerably and to increase the accuracy and reliability of the obtained results due to certain complication of algoritms for processing the experemental data. The problem of the determination of the coefficient of therma…
Reconstruction from boundary measurements for less regular conductivities
2012
In this paper, following Nachman's idea and Haberman and Tataru's idea, we reconstruct $C^1$ conductivity $\gamma$ or Lipchitz conductivity $\gamma$ with small enough value of $|\nabla log\gamma|$ in a Lipschitz domain $\Omega$ from the Dirichlet-to-Neumann map $\Lambda_{\gamma}$. In the appendix the authors and R. M. Brown recover the gradient of a $C^1$-conductivity at the boundary of a Lipschitz domain from the Dirichlet-to-Neumann map $\Lambda_{\gamma}$.
Finite-temperature geometric properties of the Kitaev honeycomb model
2018
We study finite temperature topological phase transitions of the Kitaev's spin honeycomb model in the vortex-free sector with the use of the recently introduced mean Uhlmann curvature. We employ an appropriate Fermionisation procedure to study the system as a two-band p-wave superconductor described by a BdG Hamiltonian. This allows to study relevant quantities such as Berry and mean Uhlmann curvatures in a simple setting. More specifically, we consider the spin honeycomb in the presence of an external magnetic field breaking time reversal symmetry. The introduction of such an external perturbation opens a gap in the phase of the system characterised by non-Abelian statistics, and makes the…