Dissertations / Theses: 'Temperature dependent electrical transport'

1

Kaya, Savas. "Electrical transport in strained silicon quantum wells on vicinal substrates." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313699.

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2

Webb, Alexander James. "Temperature dependence and touch sensitivity of electrical transport in novel nanocomposite printable inks." Thesis, Durham University, 2014. http://etheses.dur.ac.uk/10764/.

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Printed electronics is an established industry allowing the production of electronic components such as resistors, and more complex structures such as solar cells, from functional inks. Composites, a mixture of two or more materials with different physical and/or chemical properties that combine to create a new material with properties differing from its constituent parts, have been important in areas such as the textile and automotive industries, and are significant in printed electronics as inks for printed circuit components, touch and vapour sensors. Here, the functional performance and physical behaviour of two screen printable multi-component nanocomposite inks, formulated for touch-pressure sensing applications, are investigated. They each comprise a proprietary mixture of electrically conducting and insulating nanoparticles dispersed in an insulating polymer binder, where one is opaque and the other transparent. The opaque ink has a complex surface structure consisting of a homogeneous dispersion of nanoparticles. The transparent inks structure is characterised by large aggregates of nanoparticles distributed through the printed layer. Temperature dependent electrical transport measurements under a range of compressive loadings reveal similar non-linear behaviour in both inks, with some hysteresis observed, and this behaviour is linked to the inks structures. A physical model comprising a combination of linear and non-linear conduction contributions, with the linear term attributed to direct connections between conductive particles and the non-linear term attributed to field-assisted quantum tunnelling, has been developed and used successfully to describe the underpinning physical processes behind the unique electrical functionality of the opaque ink and, to a lesser extent, the transparent ink.

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3

Whitfield, Thomas Britain. "An analysis of copper transport in the insulation of high voltage transformers." Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/843581/.

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Examination of the paper insulation and copper stress braiding during stripdown of a number of Current Transformers (FMK type 400kV) has revealed the presence of dark deposits. Copper foils are often interspersed within layers of paper insulation and mineral oil found in transformer windings. The dark deposits were often found in association with these foils, affecting several layers of paper in addition to the layer in contact with the copper foil. This thesis describes the research undertaken to identify these deposits and establish a mechanism for the transportation through the paper layers. Preliminary investigation using scanning electron microscopy (SEM) in conjunction with energy dispersive X-ray analysis (EDX) has shown these dark deposits to be copper based. X-ray photoelectron spectroscopy was used to show that the transport of the copper deposit through the paper insulation was working under the influence of a diffusion controlled process, related to Fick's law. Laboratory studies in support of work designed to eliminate the problem have shown that corrosion of copper occurs in mineral oils containing a trace of oxygen. This corrosion is non protective in character and leads to migration of copper into adjacent layers of paper. It has been shown that the transport of copper through several layers of paper can be measured by XPS and that the concentration from one paper winding to the next declines in accord with Fick's law for non-steady state diffusion. Measurements of surface concentrations by XPS correlate well with measurements made with atomic absorption spectroscopy on solutions of extracts of the contaminated paper. The laboratory measurements have allowed determination of the diffusion coefficients and activation energy for the transport process and thus give a basis for interpretation of the diffusion profiles found in the transformer in terms of time and temperature of operation. The diffusion process is temperature dependant. The results have been used to produce long term prediction curves.

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4

Falasco, Gianmaria, Manuel V. Gnann, Daniel Rings, Dipanjan Chakraborty, and Klaus Kroy. "Effective time-dependent temperature in hot Brownian motion." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-183309.

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Falasco, Gianmaria, Manuel V. Gnann, Daniel Rings, Dipanjan Chakraborty, and Klaus Kroy. "Effective time-dependent temperature in hot Brownian motion." Diffusion fundamentals 20 (2013) 63, S. 1-2, 2013. https://ul.qucosa.de/id/qucosa%3A13640.

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6

Hai, Md. "Minimizing temperature dependent spectral shift in SOI DPSK demodulators." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104852.

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Silicon on insulator (SOI) photonic devices are becoming popular due to their compatibility with complementary metal oxide semiconductor (CMOS) technology. Over the last five years, we have seen several practical demonstrations of high-speed optical modulators, switches, filters designed on SOI platform. Some of these devices were made utilizing one fundamental property of light: Interference. However, interference-based SOI devices show disastrous spectral phase shift with temperature change which result in the necessity of integrating active temperature control circuits to stabilize them. In this work we present a 50 Gb/sec SOI Mach-Zehnder interferometer (MZI) differential phase shift keying (DPSK) demodulator which exhibits over 90% improvement in thermal stability with 0.05 nm/C of its spectral profile compared to 0.9 nm/C for a noncompensated demodulators. Our proposed method is a fully passive way of minimizing temperature dependant spectral shift in DPSK demodulators, which employs the waveguide engineering method. A full analytical approach to address the problem is derived first, which is followed by extensive numerical simulations to find out the exact device dimensions. Through this, we present a step by step approach to design the demodulator by achieving required waveguide geometry. After we get the design values of our device parameters we calculate the spectral shift with temperature change by our customized computer program and observe improved performance of the device with temperature change. With the values of design variables, we fabricate our device through Canadian Microelectronics Corporation (CMC). The waveguide width of our device varies from 280 nm to 450 nm at different stage of the device while its height was fixed to 220 nm. For thermally non-compensated demodulator, waveguide width was 450 nm throughout the device. Both thermally compensated and non-compensated demodulators are built on the same chip. Experimental result of the fabricated device is presented and we compare different performance metric of the demodulator with and without the proposed temperature compensation technique.
La recherche sur les composantes photoniques en silicium sur isolant (SOI) est devenue populaire en raison de leur compatibilité avec la technologie des semi-conducteur en métal complémentaire d'oxyde (CMOS). Pendant les cinq dernières années, nous avons vu plusieurs démonstrations pratiques de modulateurs optiques à grande vitesse, de commutateurs, et de filtres en SOI. Certaines de ces composantes utilisent une propriété fondamentale de lumière : l'interférence. Pourtant, les composantes en SOI à base d'interférence montrent un changement de phase spectral désastreux avec le changement de température qui s'ensuit d'une nécessité d'intégrer des circuits de contrôle actifs de température pour les stabiliser. Dans ce travail nous présentons un interféromètre Mach-Zehnder (MZI) en SOI à 50 Gb/sec pour la modulation de phase différentielle (DPSK). Le démodulateur a une stabilité thermale de 0.05 nm/0C qui est 90% meilleure que les démodulateurs non-compensés qui eux ont un profil spectral de 0.9 nm/0C. Notre méthode propose une façon complètement passive de minimiser l'effet de la température sur le changement spectral des démodulateurs DPSK. Une approche analytique complète suivi pardes simulations numériques permettent de définir les dimensions exactes du démodulateur. Nous présentons la géométrie due démodulateur. En utilisant les paramètres obtenus, nous calculons le changement spectral avec le changement de température en utilisant notre programme informatique conçu pour observer la performance du démodulateur. Le démodulateur a été fabriqué par la société de microélectrique Canadian (CMC). La largeur de la guide d'onde du démodulateur varie de 280 nm 450 nm et la hauteur est fixe à 220 nm. Pour le démodulateur non-compensé, la largeur du guide d'onde est 450 nm. Les démodulateurs tant compensés que non-compensés sont construits sur le même fragment. Les résultats expérimentaux sont présentés et nous comparons les différentes performances du démodulateur avec et sans la technique de compensation proposée.

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7

Zhang, Zhaohui. "Spin-dependent electrical and thermal transport in magnetic tunnel junctions." APS, 2012. http://hdl.handle.net/1993/31947.

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Thermoelectricity can directly convert a temperature difference into a voltage or charge current. Recently, the development of spin caloritronics has introduced spin as another degree of freedom in traditional thermoelectrics. This discovery bodes a new generation of magnetic random access memories (MRAMs), where thermal spin-transfer torque (TSTT) rather than voltage driven spin-transfer torque (STT) is used to switch the magnetization in magnetic tunnel junctions (MTJs). To advance the rising trend of spin caloritronics, the coupling of charge, spin, and heat flow during electron transport in MTJs was systematically studied in this thesis. To begin with, the static transport properties of MTJs were studied by observing current dependent tunnel magnetic resistance (TMR). The observed decrease of TMR with a biased current is attributed to the change in spin polarization of the free ferromagnetic layer. A phenomenological model has been built based on the current dependent polarization, which agrees with our experimental results. Next, the Seebeck rectification effect in MTJs was studied. By applying microwave currents to MTJs, an intrinsic thermoelectric coupling effect in the linear response regime of MTJs was discovered. This intrinsic thermoelectric coupling contributes a nonlinear correction to Ohm's law. In addition, this effect can be controlled magnetically since the Seebeck coefficient is related to magnetization configuration. Finally, TSTT in MTJs was systematically studied. A laser heating technique was employed to apply a temperature difference across the tunnel barrier and ferromagnetic resonance (FMR) spectra were measured electrically through spin rectification. By analyzing the FMR spectra, TSTT in MTJs was observed and the angular dependence of TSTT was found to be different from dc-biased STT. By solving the Landau-Lifshitz-Gilbert equation including STT, the experimental observations were well explained. The discovery of Seebeck rectification refines the previous understanding of magneto-transport and microwave rectification in MTJs and provides a new possibility for utilizing spin caloritronics in high-frequency applications. The study of TSTT in MTJs shows clear experimental evidence of TSTT in MTJs. Further optimization of the design of MTJs may succeed in decreasing the necessary switching fields strength or even achieve a switching by only TSTT in MTJs.
February 2017

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8

Ohlendorf, Gerd, Denny Richter, Jan Sauerwald, and Holger Fritze. "High-temperature electrical conductivity and electromechanical properties of stoichiometric lithium niobate." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-192902.

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High temperature properties such as electrical conductivity (σ) and resonance behaviour of stoichiometric lithium niobate (LiNbO3) are determined in the temperature range from 20 to 950 °C. The activation energy of the conductivity is found to be 0.9 and 1.7 eV in the temperature range from 500 to 750 °C and from 800 to 950 °C, respectively. During thermal treatments in ambient air up to 950 °C and back, the conductivity remains unchanged at a given temperature, i.e., the crystal is stable under these conditions. The oxygen partial pressure (pO2) dependence of the conductivity shows two distinct ranges. At 750 °C, the property remains unchanged down to 10−15 bar. Below 10−15 bar, the conductivity increases according to σ ~ (pO2)−1/5. Z-cut LiNbO3 plates can be excited to thickness mode vibrations up to at least 900 °C. At this temperature, the quality factor Q is found to be between 30 and 100. As for changes of the conductivity, a decrease of the resonance frequency is observed below 10−15 bar indicating a correlation of both properties. In order to evaluate the lithium evaporation, the crystals are tempered at 900 °C in ambient air for 24 h. A depth profile of the constituents does not indicate lithium loss within the accuracy of the secondary ion mass spectroscopy. The preliminary results underline the potential of stoichiometric LiNbO3 for high-temperature applications and justify its closer investigation.

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9

Sirisathitkul, C. "Studies of transport phenomena at ferromagnet/semiconductor interfaces." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325445.

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10

Green, Paul Elijah. "View-dependent precomputed light transport using non-linear Gaussian function approximations." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/35605.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2006.
Includes bibliographical references (p. 43-46).
We propose a real-time method for rendering rigid objects with complex view-dependent effects under distant all-frequency lighting. Existing precomputed light transport approaches can render rich global illumination effects, but high-frequency view-dependent effects such as sharp highlights remain a challenge. We introduce a new representation of the light transport operator based on sums of Gaussians. The non-linear parameters of the representation allow for 1) arbitrary bandwidth because scale is encoded as a direct parameter; and 2) high-quality interpolation across view and mesh triangles because we interpolate the average direction of the incoming light, thereby preventing linear cross-fading artifacts. However, fitting the precomputed light transport data to this new representation requires solving a non-linear regression problem that is more involved than traditional linear and non-linear (truncation) approximation techniques. We present a new data fitting method based on optimization that includes energy terms aimed at enforcing good interpolation. We demonstrate that our method achieves high visual quality for a small storage cost and fast rendering time.
by Paul Elijah Green.
S.M.

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11

Ainslie, Mark Douglas. "Transport AC loss in high temperature superconducting coils." Thesis, University of Cambridge, 2012. https://www.repository.cam.ac.uk/handle/1810/244077.

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In this dissertation, the problem of calculating and measuring AC losses in superconducting coils is addressed, with a particular focus on the transport AC loss of coils for electric machines. In order to model the superconducting coil's electromagnetic properties and calculate the AC loss, an existing two dimensional (2D) finite element model that implements a set of equations known as the H formulation, which directly solves the magnetic field components in 2D, is extended to model a superconducting coil, where the cross-section of the coil is modelled as a 2D stack of superconducting coated conductors. The model is also modified to allow the nclusion of a magnetic substrate, which is present in some commercially available HTS wire. The analysis raises a number of interesting points regarding the use of superconductors with magnetic substrates. In particular, the presence of a magnetic substrate affects the penetration of the magnetic flux front within the coil and increases the magnetic flux density within the penetrated region, both of which can increase the AC loss significantly. In order to investigate these findings further, a comprehensive analysis on stacks of tapes with weak and strong magnetic substrates is carried out, using a symmetric model that requires only one quarter of the cross-section to be modelled. In order to validate the modelling results, an extensive experimental setup is designed and built to measure the transport AC loss of a superconducting coil using an electrical method based on inductive compensation by means of a variable mutual inductance. Measurements are carried out on the superconducting racetrack coil and it is found that the experimental results agree with the modelling results for low current, but some phase drift occurs for higher current, which affects the accuracy of the measurement. In order to overcome this problem, a number of improvements are made to the initial setup to improve the lock-in amplifier's phase setting and other aspects of the measurement technique. New measurements are carried out on a single, circular pancake coil and the discrepancies between the experimental and modelling results are described in terms of the assumptions made in the model and aspects of the coil that cannot be modelled. Using the original measured properties of the superconducting tape, there is an order of magnitude difference between the experiment and model. The properties of the superconductor can degrade during the winding and cooling processes, and a critical current measurement of the coil showed that the tape critical current reduced from nearly 300 A, down to around 100 A. Applying this finding to the model, the experimental and modelling results show good agreement, and the difference in the slope of the AC loss curve can be described in terms of the B-dependent critical current dependency Jc(B) used in the model. Finally, methods used to mitigate AC loss in superconducting wires and coils are summarised, and the use of weak and strong magnetic materials as a flux diverter is investigated as a technique to reduce AC loss in superconducting coils. This technique can achieve a significant reduction in AC loss and does not require modification to the conductor itself, which can be detrimental to the superconductor's properties.

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12

Lohstroh, Annika. "Temperature dependent charge transport studies in polycrystalline and single crystal CVD diamond detectors." Thesis, University of Surrey, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426025.

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13

Eshghi, Hosein. "Electron and hole transport in GaN and InGaN." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/2237/.

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14

Barraclough, Jack Matthew. "Electrical transport properties of URhGe and BiPd at very low temperature." Thesis, University of St Andrews, 2015. http://hdl.handle.net/10023/6327.

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URhGe has garnered interest recently as one of the few known ferromagnetic superconductors. The superconductivity in this material appears to arise from magnetic fluctuations rather than phonons, and take a triplet form which is remarkably resistant to field. In this thesis, a number of measurements on the material are presented. Some probe the Fermiology, with strong evidence appearing for a model which as both light open sheets and heavy, small, closed pockets. The open sheets, associated with chains of real-space electron density running along the b axis, dominate the conductivity in most circumstances. Evidence for their existence arises from the general large and non-saturating magnetoresistance, and from the unusual observation of negative temperature coefficient of resistance at high fields. The closed pockets have provided a few Shubnikov-de Haas oscillations, but mostly they remain inferred from the high specific heat γ and their role in the magnetism. In order to better probe the superconductivity, a high precision low noise DC resistance measurement bridge was built using a SQUID. Along with conventional measurements, this provides evidence that the two pockets of superconductivity on the phase diagram are the same phase. The re-entrance an be understood simply as a result of magnetic field being a tuning parameter, but also suppressing bulk superconductivity through orbital limiting. The SQUID bridge allowed the detection of domain wall superconductivity linking up these two pockets. The SQUID bridge was also used to study the highly structured superconducting transition in BiPd. This material lacks inversion symmetry in its crystal structure, so is a good candidate for unusual forms of superconductivity. Here again non-bulk superconductivity is considered the most likely cause for the structure. Unusual and distinctive IV curves have been measured, and a simple model of inhomogeneous conductivity channels with different critical currents is proposed as an explanation.

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15

Cheung, Terence Chi-Hin 1980. "Room temperature transport measurements on Bridgman-grown Culn₁-xGaxSe₂." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97879.

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Filamentary samples were cut from ingots of the chalcopynte semiconductor CuIn1-x,GaxSe2, grown by a vertical Bridgman method for compositions x = 0, 0.2, and 0.3. On these, room-temperature measurements were made of thermoelectric power (alpha), Hall coefficient (RH), and electrical conductivity (sigma). Analysis of the measured results was made on a two-carrier basis, taking the minority electrons into account. Assuming dominant acoustic lattice scattering and an effective hole mass ratio, m p/m0 = 0.7, the only common acceptable value for the electron-to-hole mobility ratio, b, was found to be b = 5, for all filamentary samples. Using this value, hole concentrations were found to be lower than those derived from a one-carrier model, and hole mobilities were correspondingly higher. The mobilities in quaternary samples were lower than those in the ternaries. Furthermore, the hole concentrations were much higher in the quaternary filaments cut from the end of the grown ingots than from the middle.

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16

Ohlendorf, Gerd, Denny Richter, Jan Sauerwald, and Holger Fritze. "High-temperature electrical conductivity and electromechanical properties of stoichiometric lithium niobate." Diffusion fundamentals 8 (2008) 6, S. 1-7, 2008. https://ul.qucosa.de/id/qucosa%3A14152.

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High temperature properties such as electrical conductivity (σ) and resonance behaviour of stoichiometric lithium niobate (LiNbO3) are determined in the temperature range from 20 to 950 °C. The activation energy of the conductivity is found to be 0.9 and 1.7 eV in the temperature range from 500 to 750 °C and from 800 to 950 °C, respectively. During thermal treatments in ambient air up to 950 °C and back, the conductivity remains unchanged at a given temperature, i.e., the crystal is stable under these conditions. The oxygen partial pressure (pO2) dependence of the conductivity shows two distinct ranges. At 750 °C, the property remains unchanged down to 10−15 bar. Below 10−15 bar, the conductivity increases according to σ ~ (pO2)−1/5. Z-cut LiNbO3 plates can be excited to thickness mode vibrations up to at least 900 °C. At this temperature, the quality factor Q is found to be between 30 and 100. As for changes of the conductivity, a decrease of the resonance frequency is observed below 10−15 bar indicating a correlation of both properties. In order to evaluate the lithium evaporation, the crystals are tempered at 900 °C in ambient air for 24 h. A depth profile of the constituents does not indicate lithium loss within the accuracy of the secondary ion mass spectroscopy. The preliminary results underline the potential of stoichiometric LiNbO3 for high-temperature applications and justify its closer investigation.

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17

Murphy, Helen Marie. "Quantum transport in superlattice and quantum dot structures." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364637.

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18

Ghorbani, Shaban Reza. "Structural and Electrical Transport Properties of Doped Nd-123 Superconductors." Doctoral thesis, KTH, Physics, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3461.

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It is generally believed that one of the key parameterscontrolling the normal state and superconducting properties ofhigh temperature superconductors is the charge carrierconcentrationpin the CuO₂planes.By changing the non-isovalent dopingconcentration on the RE site as well as the oxygen content in(RE)Ba₂Cu₃O_7−δ, an excellent tool is obtained tovary the hole concentration over a wide range from theunderdoped up to the overdoped regime.In the present thesis thefocus is on the doping effects on the structural and normalstate electrical properties in Nd-123 doped with Ca, La, Pr,Ca-Pr, and Ca-Th.T he effects of doping have been investigatedby X-ray and neutron powder diffraction, and by measurements ofthe resistivity, thermoelectric powerS, and Hall coefficient R_H.T he thermoelectric power is a powerful tool forstudies of high temperature superconductivity and is highlysensitive to details of the electronic band structure.Sas a function of temperature has been analyzed in twodifferent two band models.The parameters of these models arerelated to charactristic features of the electron bands and asemiempirical physical description of the doping dependence ofSis obtained.So me important results are following:

(i)The valence of Pr in the RE-123 family.Results from thestructural investigations, the critical temperature Tc, and thethermoelectric power indicated a valence +4 at low dopingconcentration, which is in agreement with results of chargeneutral doping in the RE-123 family.(ii)Hole localization. The results of bond valence sum (BVS)calculations from neutron diffraction data showed that holelocalization on the Pr⁺⁴site was the main reason for the decrease of thehole concentration p.Differ ent types of localization wereinferred by S measurements for Ca-Th and Ca-Pr dopings.(iii)Competition between added charge and disorder. Theresults of RH measurements indicated that Ca doping introduceddisorder in the CuO₂planes in addition to added charge.This could bethe main reason for the observed small decrease of thebandwidth of the density of states in the description of aphenomenological narrow band model.(iv) Empirical parabolic relation between γ and p.S data were analyzed and well described by a two-band modelwith an additional linear T term, γT.An empiricalparabolic relation for γ as a function of holeconcentration has been found.

Key words:high temperature superconductors, criticaltemperature, resistivity, thermoelectric power, Hallcoefficient, X-ray diffraction, Neutron diffraction, NdBa₂Cu₃O_7−δ, hole concentration,substitution.

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19

Yunus, Mamoon I. (Mamoon Iqbal). "Spatial- and time-dependent thermal and electrical behavior of quenching high-temperature superconducting composite tapes." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/35046.

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20

Pell, Wendy. "Temperature dependent transport properties of aluminum chloride in thionyl chloride solutions: A non-aqueous battery electrolyte study." Thesis, University of Ottawa (Canada), 1991. http://hdl.handle.net/10393/7954.

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This thesis is a physical chemical study of the AlCl$\sb3$/SOCl$\sb2$ system. Conductivity, viscosity, and density were determined for AlCl$\sb3$ concentrations ranging from 0 to 35 weight percent in SOCl$\sb2$, and over the temperature range $-$35 to 20$\sp\circ$C. The measured conductivity was in the $\mu$Scm$\sp{-1}$ range, indicating the solution to be a weak electrolyte. Viscosities ranging from 0.7 cP for pure SOCl$\sb2$, to 3.0 cP for 4.0M AlCl$\sb3$ were found, with viscosity increasing with increasing salt concentration. The solution densities for all concentrations considered were approximately 1.7g/ml, and thermal expansivity, $\alpha\sb{\rm TE}$, was approximately 1000$\sp\circ$K$\sp{-1}$, (5 times greater than $\alpha\sb{\rm TE}$ of water). Experimental results indicate that no abrupt change in the distribution of species in solution occurs, either as a function of solute concentration or temperature. The physical properties of these solutions were observed to change gradually and smoothly with both solute concentration and temperature indicating that a mechanistic change in the Li/SOCl$\sb2$ cell operation does not likely occur as a result of changes in bulk electrolyte properties. (Abstract shortened by UMI.)

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21

俞大風 and Tai-fung Yu. "An analysis of electrical transport and magnetic susceptibility properties of YBa2Cu3O7-[delta] and La2-xSrxCuO4 high Tcsuperconductors." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1997. http://hub.hku.hk/bib/B31238014.

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Chalashkanov, Nikola M. "Influence of water absorption and temperature on charge transport and electrical degradation in epoxy resins." Thesis, University of Leicester, 2011. http://hdl.handle.net/2381/9997.

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The work aims to understand bulk transport mechanisms in epoxy resins and their influence on partial discharge and electrical treeing phenomena. The charge transport processes in two bisphenol-A epoxy resin systems were studied using dielectric spectroscopy and related to moisture uptake. In both resins, absorbed moisture was implicated in the formation of a bulk quasi-dc (QDC) charge transport mechanism above the glass transition temperature. Complementary investigations of the electrical degradation process in epoxy resins, principally electrical treeing, were also found to be dependent on temperature and moisture absorbed by the samples. A model for electrical tree growth in flexible epoxy resins has been proposed. The novelty of the model is that it considers a QDC charge transport through the bulk polymer, where proton hopping is suggested as a long range transport mechanism. The time needed for the neutralisation of the space charge accumulated ahead of a growing tree structure by charges involved in the QDC process is suggested as a governing parameter of the tree growth rate. Electrical tree growth is related to changes in the time constant of the QDC process and hence the percolation distance that the protons can travel. At high levels of moisture and/or temperature, multiple percolation paths can be established thus increasing the effective ionic conductivity of the material leading to thermal breakdown when tanδ is greater than 1.

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Yu, Tai-fung. "An analysis of electrical transport and magnetic susceptibility properties of YBa2Cu3O7-[delta] and La2-xSrxCuO4 high Tc superconductors /." Hong Kong : University of Hong Kong, 1997. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19036607.

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24

Arabshahi, Hadi. "Simulations of electron transport in GaN devices." Thesis, Durham University, 2002. http://etheses.dur.ac.uk/4119/.

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This thesis deals with the development and application of Monte Carlo simulations to study electron transport in bulk GaN in the wurtzite crystal structure and the properties of field effect transistors made from the material. There is a particular emphasis on transport in the high electric field regime and transistors operating at high voltages. The simulation model includes five sets of non-parabolic conduction band valleys which can be occupied by electrons during high field transport. The effects on electron transport of impurities and the relevant phonon scattering mechanisms have been considered. Results for electron transport at both low and high electric field are presented and compared with the properties of GaN in the zincblende structure, of other group-III nitride semiconductors, and of GaAs. The dependence of the transport properties on the material parameters is discussed and also with regard to the temperature, donor concentration and electric field magnitude and direction. The transport properties of electrons in wurtzite GaN n+-i(n)-n+ diodes are also explored, including the effect of the upper valleys and the temperature on hot electron transport. Simulations have also been carried out to model the steady-state and transient properties of GaN MESFETs that have recently been the subject of experimental study. It has been suggested that traps have a substantial effect on the performance of GaN field effect transistors and we have developed a model of a device with traps to investigate this suggestion. The model includes the simulation of the capture and release of electrons by traps whose charge has a direct effect on the current flowing through the transistor terminals. The influence of temperature and light on the occupancy of the traps and the /- V characteristics are considered. It is concluded that traps are likely to play a substantial role in the behaviour of GaN field effect transistors. Further simulations were performed to model electron transport in AlGaN/GaN hetero-junction FETs. So called HFET structures with a 78 nm Alo.2Gao.8N pseudomorphically strained layer have been simulated, with the inclusion of spontaneous and piezoelectric polarization effects in the strained layer. The polarization effects are shown to not only increase the current density, but also improve the electron transport by inducing a higher electron density close to the positive charge sheet that occurs in the channel.

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25

Le, Poul Nicolas. "Charge transfer at the high-temperature superconductor/liquid electrolyte interface." Thesis, University of Exeter, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391279.

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Ryder, J. "An experimental investigation into the electrical transport properties of Laâ†2CuOâ†4â†+â†#delta# and Ndâ†2CuOâ†4â†+â†#delta#." Thesis, University of Bristol, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279724.

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Muchharla, Baleeswaraiah. "Low Temperature Electrical Transport in 2D Layers of Graphene, Graphitic Carbon Nitride, Graphene Oxide and Boron-Nitrogen-Carbon." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/dissertations/1132.

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In this work, we have investigated temperature dependent electrical transport properties of carbon based two-dimensional (2D) nanomaterials. Various techniques were employed to synthesize the samples. For instance, high quality large area graphene and boron, nitrogen doped graphene (BNC) were grown using thermal catalytic chemical vapor deposition (CVD) method. Liquid phase exfoliation technique was utilized to exfoliate graphene and graphitic carbon nitride samples in isopropyl alcohol. Chemical reduction technique was used to reduce graphene oxide (rGO) by utilizing ascorbic acid (a green chemical) as a reducing agent. Detailed structural and morphology characterization of these samples was performed using state of the art microscopy as well as spectroscopic techniques (for example; Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), UV-Visible spectroscopy as well as Raman Spectroscopy). The low temperature (5 K< T <400 K) electrical transport properties of these materials show substantial difference from sample to sample studied. For instance, CVD grown graphene film has displayed metallic behavior over a wide range of temperature (5 K < T <300 K). At higher temperatures, resistivity followed linearly with the temperature (ρ(T) ~T). A power law dependence (ρ(T) ~ T4) observed at lower temperatures. Where as liquid phase exfoliated graphene and graphitic carbon nitride samples displayed nonmetallic nature: increasing resistance with decrease in temperature over a wide range (8 K < T < 270 K) of temperature. Electrical transport behavior in these samples was governed by two different Arrhenius behaviors in the studied temperature range. In the case of rGO and BNC layers, electrical conduction show two different transport mechanisms 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, Mott's two dimensional-Variable Range Hopping (2D-VRH) behavior was observed.

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Lotse, Henrik. "Electrical analysis of interface recombination of thin-film CIGS solar cells." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-426324.

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In this master thesis, electrical characterization of thin film CuInxGa(1−x)Se2 solar cells produced by Midsummer AB were performed with the aim of determining the dominant recombination path of these cells. Current-Voltage (IV), Quantum Effinciency (QE), temperature dependent IV (IVT) and Drive-Level Capacitance Profiling (DLCP) was used with the objective to investigate the dominant recombination path as well as provide some insight of the solar cells in order to create a baseline model using the modelling software SCAPS (Solar cell CAPacitance Simulator). The IV produced mostly consistent results with slight variation, most likely due to non uniformity of equipment. The QE showed consistent results between all cells indicating a stable process for the sample preparation. Using IVT measurements were taken from a temperature of 115K −300K in order to obtain the activation energy for the dominant recombination path. By comparing it with the band gap energy from the QE measurement, it was found that the dominant recombination path is in either the space charge region or in the bulk of the CIGS and not at the hetero interface. DLCP measurement were made at both low temperature and at room temperature and revealed that the cells had a similar doping as other comparable cells at 7×1016cm−3 . The initial baseline model created in SCAPS show a good agreement with the measured IV and currently indicates a spike in the band alignment, supporting the results for the IVT measurement.

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29

Tirino, Louis. "Transport Properties of Wide Band Gap Semiconductors." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5210.

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Transport Properties of Wide Band Gap Semiconductors Louis Tirino III 155 pages Directed by Dr. Kevin F. Brennan The objective of this research has been the study of the transport properties and breakdown characteristics of wide band gap semiconductor materials and their implications on device performance. Though the wide band gap semiconductors have great potential for a host of device applications, many gaps remain in the collective understanding about their properties, frustrating the evaluation of devices made from these materials. The model chosen for this study is based on semiclassical transport theory as described by the Boltzmann Transport Equation. The calculations are performed using an ensemble Monte Carlo simulation method. The simulator includes realistic, numerical energy band structures derived from an empirical pseudo-potential method. The carrier-phonon scattering rates and impact ionization transition rates are numerically evaluated from the electronic band structure. Several materials systems are discussed and compared. The temperature-dependent, high-field transport properties of electrons in gallium arsenide, zincblende gallium nitride, and cubic-phase silicon carbide are compared. Since hole transport is important in certain devices, the simulator is designed to simulate electrons and holes simultaneously. The bipolar simulator is demonstrated in the study of the multiplication region of gallium nitride avalanche photodiodes.

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30

Poudel, Chhetri Tej Bahadur. "EFFECTS OF LIGHT ILLUMINATION, TEMPERATURE AND OXYGEN GAS FLOW ON THE ELECTRICAL TRANSPORT PROPERTIES OF Sb-DOPED ZnO MICRO AND NANOWIRES." Miami University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=miami1501776637539529.

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31

Bertilsson, Tobias, and Mårten Persson. "Situation-dependent spontaneous mobile information service for travelers." Thesis, Blekinge Tekniska Högskola, Avdelningen för telekommunikationssystem, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-3586.

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This application is created to provide valid and relevant travel information to travelers on their journey. The application is proposed as a demonstration for seamless communications in the VINNOVA-sponsored project PIITSA (Personal Information Intelligent Transport systems through Seamless communications and Autonomous decisions). The PIITSA-project is a cooperation between Blekinge Institute of Technology (BTH), Saab AB, SP Swedish National Testing and Research Institute and Swedish Road Administration region Stockholm. The project is going on under three years, and the goal is to define communication and decision functions which will make it easier for ITS-applications (Intelligent Transport Systems and Services) that have the need of supplying personalised information. This project presents a solution to the question “How do I get from point A to point B in any case”. All that the user needs is a PDA with the application installed and being able to connect to the service via a mobile network. If the user has specified a route in the application, then the user will receive up-to-date information on how to get to his destination. This information is presented on the user’s PDA. If something happens on the current route, then the user will get an automatic message sent to him presenting the problem and give him a new travel route. Thanks to this the user won’t be stuck in the traffic problem and will probably reach its destination in time.
Examensarbetet tog fram en demonstrationstjänst för det VINNOVA-sponsrade projekt PIITSA (Personlig Information i Intelligenta Transportsystem genom Sömlös kommunikation och Autonoma beslut). Den används på en handdator och hjälper resenrärer "att komma från A till B i alla fall" genom att ge möjlighet att söka eller lägga in reserutter och övervaka aktuell trafikinformation i samband med dessa rutter, främst avseende kollektivtrafik i Stockholmsområdet. Mervärdet består i att resenären blir varnat automatiskt om någonting händer längs de valda rutterna och ges möjlighet att få en ny rutt. Applikationen kan användas i skarp läge.
Primary contact: Markus Fiedler, +46 708 537339

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32

Sixou, Bruno. "Proprietes de transport dans les polymeres conducteurs electroniques." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10271.

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Ce travail est consacre a l'etude des proprietes de transport, conductivite et pouvoir thermoelectrique, de plusieurs polymeres conducteurs electroniques. Le suivi de l'evolution de ces proprietes en fonction d'un seul parametre de structure, a savoir: le desordre cree par le vieillissement dans le polypyrrole ou dans la polyaniline protonee a l'acide camphre sulfonique, le taux de reticulation dans des reseaux a base de polyoctylthiophene, ou la composition dans des composites polyaniline-nafion ou polyaniline-polyoxyde d'ethylene, nous a permis de preciser la nature du processus de conduction dans chacun de ces materiaux, et de degager des caracteristiques communes a ces systemes. Dans les polymeres conducteurs tres desordonnes, on observe un processus de sauts limite par l'energie de charge entre ilots conducteurs polaroniques separes par des barrieres isolantes. Nous montrons que la variation thermique de la conductivite observee experimentalement peut etre obtenue par des simulations numeriques a partir de methodes de milieu effectif. Dans les reseaux de polyoctylthiophene, une correlation est fortement suggeree entre ilots conducteurs et ilots cristallins. Dans les melanges a base de polyaniline, les ecarts observes par rapport a la theorie classique de la percolation sont attribues a ces processus de hopping. Pour des niveaux de conduction croissants, interviennent un effet tunnel entre gros ilots induit par les fluctuations thermiques puis des processus de conduction de type metallique, lies a la structure interne des grains conducteurs et de nature quasi-unidimensionnel. Les mesures de pouvoir thermoelectrique confirment cette image heterogene de la structure. De facon generale, a un terme lineaire en fonction de la temperature, de type metallique, se superpose, une contribution de type semi-conducteur amorphe. Dans les polymeres conducteurs, c'est la microstructure, les heterogeneites de dopage ou les zones plus ou moins cristallines qui determinent en premier lieu les proprietes de transport macroscopiques. La structure locale des chaines intervient dans les processus de conduction a l'interieur des ilots conducteurs et en filigrane dans les proprietes de transport macroscopiques. Dans cette perspective, le vieillissement peut etre decrit comme un grignotage d'ilots conducteurs au profit de barrieres isolantes

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33

Crivelli, Dawid Wiesław. "Particle and energy transport in strongly driven one-dimensional quantum systems." Doctoral thesis, Katowice: Uniwersytet Śląski, 2016. http://hdl.handle.net/20.500.12128/5879.

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This Dissertation concerns the transport properties of a strongly–correlated one–dimensional system of spinless fermions, driven by an external electric field which induces the flow of charges and energy through the system. Since the system does not exchange information with the environment, the evolution can be accurately followed to arbitrarily long times by solving numerically the time–dependent Schrödinger equation, going beyond Kubo’s linear response theory. The thermoelectric response of the system is here characterized, using the ratio of the induced energy and particle currents, in the nonequilibrium state under the steady applied electric field. Even though the equilibrium response can be reached for vanishingly small driving, strong fields produce quantum–mechanical Bloch oscillations in the currents, which disrupt the proportionality of the currents. The effects of the driving on the local state of the ring are analyzed via the reduced density matrix of small subsystems. The local entropy density can be defined and shown to be consistent with the laws of thermodynamics for quasistationary evolution. Even integrable systems are shown to thermalize under driving, with heat being produced via the Joule effect by the flow of currents. The spectrum of the reduced density matrix is shown to be distributed according the Gaussian unitary ensemble predicted by random–matrix theory, both during driving and a subsequent relaxation. The first fully–quantum model of a thermoelectric couple is realized by connecting two correlated quantum wires. The field is shown to produce heating and cooling at the junctions according to the Peltier effect, by mapping the changes in the local entropy density. In the quasiequilibrium regime, a local temperature can be defined, at the same time verifying that the subsystems are in a Gibbs thermal state. The gradient of temperatures, established by the external field, is shown to counterbalance the flow of energy in the system, terminating the operation of the thermocouple. Strong applied fields lead to new nonequilibrium phenomena. At the junctions, observable Bloch oscillations of the density of charge and energy develop at the junctions. Moreover, in a thermocouple built out of Mott insulators, a sufficiently strong field leads to a dynamical transition reversing the sign of the charge carriers and the Peltier effect.

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34

Nichterwitz, Melanie [Verfasser], and Bernd [Akademischer Betreuer] Rech. "Charge carrier transport in Cu(In,Ga)Se2 thin-film solar-cells studied by electron beam induced current and temperature and illumination dependent current voltage analyses / Melanie Nichterwitz. Betreuer: Bernd Rech." Berlin : Universitätsbibliothek der Technischen Universität Berlin, 2012. http://d-nb.info/1023762145/34.

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35

Thérond, Pierre-Guy. "Etude des propriétés de transport de composés d'actinides." Grenoble 1, 1986. http://www.theses.fr/1986GRE10109.

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Mesures de la conductivite electrique, de la magnetoconductivite et de l'effet hall sur echantillons monocristallins de npas::(2) et pusb::(1-x)te::(x); analyse des variations en fonction de la temperature et du champ magnetique, modes de diffusion dominants. Etude de l'effet d'un champ magnetique intense sur la conductivite de uas et up et attribution des variations observees soit a un changement de structure antiferromagnetique soit a l'anisotropie du tenseur de conductivite par rapport au vecteur de modulation de la structure magnetique

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36

Dou, Ziwei. "Investigation on high-mobility graphene hexagon boron nitride heterostructure nano-devices using low temperature scanning probe microscopy." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/283618.

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This thesis presents several experiments, generally aiming at visualising the ballistic and topological transport on the high-mobility graphene/boron nitride heterostructure using the scanning gate microscope. For the first experiment, we use the scanning gate microscopy to map out the trajectories of ballistic carriers in high-mobility graphene encapsulated by hexagonal boron nitride and in a weak perpendicular magnetic field. We employ a magnetic focusing transport configuration to image carriers that emerge ballistically from an injector, follow a cyclotron path due to the Lorentz force from an applied magnetic field, and land on an adjacent collector probe. The local potential generated by the scanning tip in the vicinity of the carriers deflects their trajectories, modifying the proportion of carriers focused into the collector. By measuring the voltage at the collector while scanning the tip, we are able to obtain images with arcs that are consistent with the expected cyclotron motion. We also demonstrate that the tip can be used to redirect misaligned carriers back to the collector. For the second experiment, we investigate the graphene van der Waals structures formed by aligning monolayer graphene with insulating layers of hexagonal boron nitride which exhibit a moiré superlattice that is expected to break sublattice symmetry. However, despite an energy gap of several tens of millielectronvolts opening in the Dirac spectrum, electrical resistivity remains lower than expected at low temperature and varies between devices. While subgap states are likely to play a role in this behaviour, their precise nature is still unclear in the community. We therefore perform a scanning gate microscopy study of graphene moiré superlattice devices with comparable activation energy but with different charge disorder levels. In the device with higher charge impurity ($\sim$ 10$^-$ cm$^{-2}$) and lower resistivity ($\sim$ 10 k$\Omega$) at the Dirac point we observe scanning gate response along the graphene edges. Combined with simulations, our measurements suggest that enhanced edge doping is responsible for this effect. In addition, a device with low charge impurity ($\sim$ 10$^{9}$ cm$^{-2}$) and higher resistivity ($\sim$ 100 k$\Omega$) shows subgap states in the bulk. Our measurements provide alternative model to the prevailing theory in the literature in which the topological bandstructures of the graphene moiré superlattices entail an edge currents shunting the insulating bulk. In the third experiment, we continue our study in the graphene moir$\acute e$ superlattices with the newly reported non-local Hall signals at the main Dirac point. It has been associated with the non-zero valley Berry curvature due to the gap opening and the nonlocal signal has been interpreted as the signature of the topological valley Hall effects. However, the nature of such signal is still disputed in the community, due to the vanishing density of states near the Dirac point and the possible topological edge transport in the system. Various artificial contribution without a topological origin of the measurement scheme has also been suggested. In connection to the second experiment, we use the scanning gate microscope to image the non-local Hall resistance as well as the local resistance in the current path. By analysing the features in the two sets of images, we find evidence for topological Hall current in the bulk despite a large artificial components which cannot be distinguished in global transport measurement. In the last experiment, we show the development of a radio-frequency scanning impedance microscopy compatible with the existing scanning gate microscopy and the dilution refrigerator. We detailed the design and the implementation of the radio-frequency reflectometry and the specialised tip holder for the integration of the tip and the transmission lines. We demonstrate the capability of imaging local impedance of the sample by detecting the mechanical oscillation of the tip, the device topography, and the Landau levels in the quantum Hall regime at liquid helium temperature and milli-Kelvin temperature.

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Almansour, Amjad Saleh Ali. "USE OF SINGLE TOW CERAMIC MATRIX MINICOMPOSITES TO DETERMINE FUNDAMENTAL ROOM AND ELEVATED TEMPERATURE PROPERTIES." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron148640184494135.

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38

Joo, Min Kyu. "Caractérisation électrique de transistors à effet de champ avancés : transistors sans jonctions, sur réseaux de nanotubes de carbone ou sur nanofil en oxyde d'étain." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENT041/document.

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Les matériaux de faible dimensionnalité, tels que les nanotubes de carbone, le graphène, les nanofils de semi-conducteurs ou d'oxydes métalliques, présentent des propriétés intéressantes telles qu'un rapport surface/ volume important, des mobilités électroniques élevées, des propriétés thermiques et électriques particulières, avec la possibilité de constituer une alternatives à certaines fonctions CMOS ou d'intégrer de nouvelles fonctions comme la récupération d'énergie ou des capteurs. Pour la bio-détection, les nanofils permettent par exemple d'obtenir une grande sensibilité à la présence de biomolécules cibles grâce à la modification de charge qui accompagne leur hybridation sur des biomolécules sondes greffées à la surface du nanofil et au fort couplage électrostatique de cette charge de surface avec le cœur du nanofil. La fabrication de ce type de structure suit différentes voies: une voie dite "top-down" qui est utilisée par la production microélectronique de masse et qui permet un excellent contrôle technologique grâce à l'utilisation d'équipements, notamment de lithographie, extrêmement performants; une seconde voie moins coûteuse mais moins contrôlée dite "bottom-up" dont un exemple répandu est la réalisation de réseaux aléatoires, obtenus par dispersion de nanostructures réalisées directement sous forme 1D par croissance et en général relativement dopés de façon non nécessairement contrôlée. Dans les deux cas, le mécanisme de base est le contrôle électrostatique du canal par effet de champ d'un ensemble (organisé ou non) de nanostructures. Dans cette thèse, trois types de transistors différents sont explorées ; des transistors à nanofils SnO2, des réseaux aléatoires de nanotubes de carbone, des transistors à nanofil à canal uniformément dopé, dits "junctionless transistors" ou JLTs). Par rapport à la configuration classique d'un transistor MOS à inversion, le contrôle demande en général à être reconsidéré pour tenir compte des spécificités de ce type de structures: topologie du canal, isolants non standards (résines), effets de percolation dans les réseaux désordonné, contrôle électrostatique dans les nanofils fortement dopés, rôle crucial des états d'interface. Le travail s'appuie sur (i) une caractérisation approfondie de ces composants en statique (contrôle du courant), en petit signal (contrôle de la charge) et en bruit (pièges et états d'interfaces), (ii) une analyse critique des méthodologies d'extraction de paramètres et des modèles utilisés pour analyser ce fonctionnement avec dans certains cas l'appui de simulations et (iii) le développement, lorsque cela s'avère nécessaire, de nouvelles méthodologies d'extraction
In this dissertation, the electrical characterization of heavily-doped junctionless transistors (JLTs) and individual tin-oxide (SnO2) nanowire field-effect transistors (FETs) and single-walled carbon nanotube (SWCNT) random network thin film transistors (RN-TFTs) are presented in terms of I-V, C-V, low frequency noise (LFN), and low temperature measurement including a numerical simulation, respectively. As a potential emerging candidate for more than Moore, recently developed heavily doped JLTs were studied in low-temperature (77K ~ 350K) with double gate mode to have physical insights of carrier scattering mechanism with account for both the position of flat-band voltage and doping concentration, respectively. Besides, as a nano-scaled bottom-up device, polymethyl methacrylate passivated individual SnO2 nanowire FET was discussed. A large contribution of channel access resistance to carrier mobility and LFN behavior was found as same as in nano-structure devices. Furthermore, various electrical characteristics of percolation dominant N-type SWCNT RN-TFTs were demonstrated by taking into account for I-V, C-V, LFN and a numerical percolation simulation

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39

GADENNE, PETIT MIREILLE. "Proprietes de transport de couches minces d'or granulaire : absorption infra-rouge, effets dimensionnels." Paris 6, 1987. http://www.theses.fr/1987PA066385.

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Etude dans des milieux inhomogenes: couches minces d'or granulaires et cermets au-al::(2)o::(3) dans un regime isolant ou conducteur. Analyse des relations entre la morphologie, la conductivite en courant continu, la magnetoresistance, les proprietes optiques. Etude a l'aide de la theorie de champ moyen de bruggeman, de la fonction dielectrique optique. Mise en evidence a la percolation d'un cross-over de la concentration critique en fonction de l'epaisseur et d'un comportement critique caracteristique de l'absorption optique. Explication theorique par une correlation entre l'inverse du temps de relaxation des electrons de conduction et la tortuosite de la morphologie fractale

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40

Cazimajou, Thibauld. "Étude de l’effet de champ et du transport dans des réseaux aléatoires percolants de nanofils de silicium." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAT105.

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Les réseaux aléatoires de nanofils, parfois appelés nanonets, pourraient être des candidats prometteurs pour l’intégration 3D de biocapteurs sur CMOS. Dans cette thèse nous présentons les résultats de caractérisations et de simulations de transistors à effet de champ à base de nanonets de silicium (Si NN-FET). Nous montrons que les résultats de mesure ne peuvent pas s’interpréter sans prendre en compte les dispersions au sein du nanonet.Les caractéristiques électriques statiques des Si NN-FET ont été mesurées en fonction des paramètres géométriques (dimension du canal et densité de nanofils) sur un grand nombre de composants de façon à disposer de grandeurs statistiquement significatives pour les paramètres électriques principaux (mobilité apparente à bas champ, facteur d’idéalité de la pente sous le seuil et tension de seuil) qui sont extraits grâce à un modèle compact. Nous évaluons en parallèle les variations théoriques de ces mêmes paramètres en utilisant la théorie de la percolation et des simulations Monte Carlo. Par rapport aux approches généralement utilisées dans la littérature pour des réseaux percolants, l’originalité de nos simulations est de prendre en compte l’effet de champ ainsi que les dispersions. Les dispersions en tension de seuil se sont avérées essentielles pour comprendre la dépendance expérimentale des caractéristiques électriques avec les caractéristiques du réseau. L’analyse du bruit basse fréquence des Si NN-FET permet l’estimation de la variation de l’aire électrique du nanonet avec la densité. L’étude de la variation en température des caractéristiques électriques des Si NN-FET met en évidence l’activation en température des jonctions entre nanofils. La relation inattendue de la mobilité avec la température fait soupçonner une dispersion de la hauteur de barrière des jonctions, hypothèse validée par les simulations Monte Carlo
Random networks of nanowires, sometimes called nanonets, could be promising candidates for the 3D integration of CMOS biosensors. In this thesis we present characterization and simulation results of field effect transistors based on silicon nanonets (Si NN-FET). We show that measurements cannot be understood without account for dispersions within the nanonet.The static electrical characteristics of these Si NN-FETs were measured for different geometric parameters (channel length and nanowire density) on a large number of devices, in order to obtain statistically significant orders of magnitude for the main electrical parameters (apparent low field mobility, subthreshold slope ideality factor and threshold voltage), which were extracted by means of a compact model. In parallel, the theoretical variations of these parameters were evaluated using percolation theory and Monte Carlo simulations. Compared to the usual approaches found in the literature for percolating networks, the originality of our simulations is to take into account both field-effect and dispersions. Threshold voltage dispersions proved to be essential to understand the experimental dependence of electrical parameters with network parameters. The analysis of Si NN-FET low frequency noise (LFN) made it possible to estimate the variation, with nanowire density, of the electrical area of the nanonet. From the temperature variation of Si NN-FET electrical parameters, it was found that inter-nanowire junctions were thermally activated. The unexpected variation of mobility with temperature suggests that junction barrier heights are widely dispersed, an assumption which was validated by the Monte Carlo simulations

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41

Maloufi, Nabila. "Contribution à l'étude des propriétés de transport à basse température dans les semiconducteurs amorphes du groupe IV : Application au système SI::(X) SN::(1-X)." Nancy 1, 1986. http://www.theses.fr/1986NAN10357.

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Étude des mécanismes de transport par diffusion entre états localisés. L'effet de la température, de l'épaisseur des échantillons, du recuit a été examiné dans le cadre des théories existantes. Deux domaines de température ont été mis en évidence : au-dessus de 30 K, le modèle du petit polaron, reproduit bien les résultats expérimentaux, tandis qu'au dessus de 100 K, l'accord est bon avec le modèle de pollack inspiré de la théorie de Mott complétée

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42

Giroud, Franck. "Elaboration et études des propriétés de transport de couches minces quasicristallines AlCuFe." Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10251.

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Ce travail est consacre a l'elaboration, la caracterisation structurale et microstructurale, ainsi qu'a l'etude de la conductivite electrique de couches minces de l'alliage quasicristallin alcufe. Les echantillons ont ete fabriques par evaporation sequentielle des elements constitutifs de l'alliage, puis traitement thermique. Nous avons etudie les chemins reactionnels conduisant a la phase quasicristalline par diffraction des rayons x lors du traitement thermique de tricouches metalliques. La phase quasicristalline peut etre obtenue quelle que soit la sequence d'empilement du tricouche. Nous montrons que la premiere phase qui cristallise est al#2cu y compris lorsque la couche de fer est placee entre celles de al et cu. Dans ce cas on observe la formation d'alliages binaires al, cu de part et d'autre de la couche de fe, indiquant une diffusion croisee des deux elements al et cu a travers celle-ci. A plus haute temperature le fer participe aux reactions, s'alliant d'abord avec l'aluminium, avant que des phases ternaires n'apparaissent, qui conduisent ensuite au quasicristal. Nous nous sommes ensuite concentre sur l'elaboration de couches tres minces (jusqu'a 125 angstroms). Nous avons pu fabriquer des couches quasicristallines tres minces compactes et d'epaisseur homogene. Ainsi nous avons pu etudier la conductivite electrique des echantillons en fonction de leur epaisseur. A basse temperature, les dependances en temperature et en champ magnetique de la conductivite font apparaitre une transition vers un regime bidimensionnel, qui est une signature de la presence d'effets d'interferences quantiques. Cette etude confirme leur importance dans la conductivite des quasicristaux, et permet de preciser les valeurs des parametres microscopiques qui la regissent.

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Madhavi, S. "Carrier Mobility And High Field Transport in Modulation Doped p-Type Ge/Si1-xGex And n-Type Si/Si1-xGex Heterostructures." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/294.

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Modulation doped heterostructures have revolutionized the operation of field effect devices by increasing the speed of operation. One of the factors that affects the speed of operation of these devices is the mobility of the carriers, which is intrinsic to the material used. Mobility of electrons in silicon based devices has improved drastically over the years, reaching as high as 50.000cm2/Vs at 4.2K and 2600cm2/Vs at room temperature. However, the mobility of holes in p-type silicon devices still remains comparatively lesser than the electron mobility because of large effective masses and complicated valence band structure involved. Germanium is known to have the largest hole mobility of all the known semiconductors and is considered most suitable to fabricate high speed p-type devices. Moreover, it is also possible to integrate germanium and its alloy (Si1_zGex ) into the existing silicon technology. With the use of sophisticated growth techniques it has been possible to grow epitaxial layers of silicon and germanium on Si1_zGex alloy layers grown on silicon substrates. In tills thesis we investigate in detail the electrical properties of p-type germanium and n-type silicon thin films grown by these techniques. It is important to do a comparative study of transport in these two systems not only to understand the physics involved but also to study their compatibility in complementary field effect devices (cMODFET). The studies reported in this thesis lay emphasis both on the low and high field transport properties of these systems. We report experimental data for the maximum room temperature mobility of holes achieved m germanium thin films grown on Si1_zGex layers that is comparable to the mobility of electrons in silicon films. We also report experiments performed to study the high field degradation of carrier mobility due to "carrier heating" in these systems. We also report studies on the effect of lattice heating on mobility of carriers as a function of applied electric field. To understand the physics behind the observed phenomenon, we model our data based on the existing theories for low and high field transport. We report complete numerical calculations based on these theories to explain the observed qualitative difference in the transport properties of p-type germanium and ii-type silicon systems. The consistency between the experimental data and theoretical modeling reported in this work is very satisfactory.

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Zeghib, Abdelhakim. "Contribution à l'étude de phénomènes de transport dans les couches minces Ni-Ag amorphes et microcristallisées." Rouen, 1987. http://www.theses.fr/1987ROUES014.

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Extension du modèle de Ziman aux alliages Ni-Ag et interprétation qualitative du comportement de la résistivité et du coefficient de température en fonction de la composition atomique d'argent. Etude de la structure de bandes de Ni-Ag à partir de mesures magnétiques. Mise en évidence d'un niveau lié virtuel dans les alliages majoritaires en argent, par la technique des plasmons de surface

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45

Nixdorf, Erik. "Combining measurements, remote sensing and numerical modelling to assess multi-scale flow dynamics in groundwater-dependent environmental systems." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-236485.

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Groundwater flow modelling provides an important quantitative instrument for addressing issues related to the quantity and quality of groundwater and the connected water resources. Consequently, groundwater flow models have been developed and used ubiquitously in science to deepen the understanding of subsurface processes and their drivers as well as management and planning tools. The present work investigates how numerical models can be linked to field investigations and public databases to quantitatively approach questions in the area of groundwater research. The primary goal is to develop new, efficient ways to overcome limitations of the individual hydrological concepts for solving specific hydrological problems and to increase the understanding of practical applicability of different methods. For this purpose, tailor-made approaches were developed for different study areas covering diverse spatial scales: the hydrology of a small mining lake, the riparian aquifer at the scale of a single meander as well as the aquifer systems of a large-scale river basin in China. The first part of the work deals with the physical and mathematical modelling of water constituents balance in a meromictic mining lake in Lusatia. The capability of using a rather simple mass-balance model based on a sufficient dataset of field data to evaluate lake stratification and lake-groundwater interaction were shown. In the second part, a transient numerical groundwater flow model was developed for the riparian aquifer of a stream meander and was calibrated by three different salt tracer tests. The model was used to proof the reliability of subsurface travel times derived from time series analysis and to give insights in the riparian zone dynamics during changing hydraulic gradients. The third part of the work describes the methodology to conduct risk assessment of groundwater contamination on the large catchment scale of the Songhua River in China. A comprehensive literature study was conducted to get an overview about measurement data on water quality data in China. A three-dimensional numerical flow and mass transport model was applied to access the flow and matter transport dynamics in the aquifer system of a sub-basin considering changing groundwater exploitation scenarios. Consequently, numerical groundwater modelling was combined with processed remote sensing and web mapping service data to overcome field data limitations and to derive groundwater vulnerability, groundwater hazard and groundwater risk maps for the entire Songhua River Basin. Summarizing, this doctoral thesis could develop new methods of combining field measurements, data assimilation and aggregation from various sources and groundwater modelling strategies and successfully apply these methods to find solutions on problems of multiple scales and across water systems
Die Grundwassermodellierung stellt eine wichtige wissenschaftliche Methode zur quantitativen Analyse von Fragestellungen zum Schutz der Menge und Güte der Grundwasserressourcen sowie der angeschlossenen Wasserkörper dar. Dementsprechend werden Grundwassermodelle sowohl für Planungs- und Bewertungszwecke im Wasserressourcenmanagement als auch zur wissenschaftlichen Erforschung der Prozesse im Untergrund entwickelt und angewendet. Die vorliegende Arbeit untersucht in diesem Rahmen, wie numerische Modelle, Feldmessungen und Daten generiert aus Fernerkundungsdaten und Webplattformen systematisch verknüpft werden können, um Fragestellungen im Bereich der Grundwasserforschung quantitativ zu beantworten. Das Ziel der Arbeit ist es neue effiziente Abläufe zu entwickeln, die die Limitierung der einzelnen Methoden überwinden und diese auf deren Anwendbarkeit für die Lösung spezifischer hydrologischer Probleme zu analysieren. Zu diesem Zweck wurden in dieser Doktorarbeit fallspezifische Lösungen für verschiedene Untersuchungsgebiete entwickelt, die sowohl in der räumlichen Skale als auch in den zu untersuchenden hydrologischen Fragestellungen eine große Diversität aufweisen. Im ersten Teil der Arbeit wurde die Massenbilanz von Wasserinhaltsstoffen in einem meromiktischen Tagebaurestsee im Lausitzer Revier durch physikalische und mathematische Modellierungsmethoden untersucht. Dabei konnte gezeigt werden, dass auf Basis einer gewonnenen mehrjährigen Zeitreihe von Messdaten ein einfaches Massenbilanzmodell in der Lage ist, sowohl Seeschichtungs- als auch Grundwasseraustauschdynamiken quantitativ zu beschreiben. Der zweite Teil der Arbeit umfasst die Entwicklung eines transienten numerischen Grundwassermodells für den quartären Uferaquifer im Bereich eines Flussmäanders der Selke welches anhand von Daten aus mehreren Salztracertests kalibriert wurde. Das Modell wurde dafür verwendet die transienten Verweilzeiten in der gesättigten Zone des Mäanderbogens unter dem Einfluss dynamischer hydraulischer Bedingungen zu untersuchen. Die Ergebnisse wurden im Anschluss mit Verweilzeiten verglichen, die aus der Analyse der zeitlichen Verschiebung von gemessenen elektrischen Leitfähigkeitszeitreihen zwischen Fluss und Grundwassermessstellen gewonnen wurden. Durch dieses kombinierte Verfahren konnten sowohl die Beschränkungen der zeitreihenbasierten Verweilzeitberechnung aufgezeigt als auch ein tieferes Systemverständnis für die Interaktionsdynamiken zwischen Grund- und Flusswasser auf der Mäanderskala gewonnen werden. Der dritte Teil der Arbeit beschreibt die Vorgehensweise für die Bewertung des Grundwasserkontaminationsrisikos im Einzugsgebiet des Songhua Flusses in China. Eine umfassende Literaturstudie wurde durchgeführt, um einen Überblick über die Verfügbarkeit von Messdaten zur Belastung der Wasserressourcen Chinas mit organischen Schadstoffen zu erhalten. Danach wurde für ein Teileinzugsgebiet ein dreidimensionales numerisches Grundwassermodell auf Basis der vorhandenen hydrogeologischen Daten aufgebaut. Dieses wurde dazu verwendet die Änderungen im Stofftransports und den Schadstoffkonzentrationen innerhalb des Aquifersystems unter steigenden Entnahmeraten zu analysieren. Basierend auf diesen Studien wurden auf der Skale des Gesamteinzugsgebiets, um die beschränkte Verfügbarkeit von Felddaten auszugleichen, die Ergebnisse der numerischen Grundwassermodellierung mit Fernerkundungsdaten und Webdatenbanken in einem Indexsystem kombiniert mit dem für die oberflächennahen Aquifere Vulnerabilität, Gefährdungspotential und Verschmutzungsrisiko in einer räumlichen Auflösung von 1 km² bestimmt wurden. Zusammenfassend konnten durch die vorliegende Doktorarbeit neue passgenaue Methoden zur effektiven Kombination von in-situ Messungen, der Datenerhebung und Datenintegration aus vielfältigen Datenquellen sowie numerischen Grundwassermodellierungsstrategien entwickelt und zur Lösung der untersuchten hydrologischer Fragestellen auf den verschiedenen Skalen und über die Grenzen der einzelnen hydrologischen Teilsysteme hinaus erfolgreich angewandt werden

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46

Boujida, Mohamed. "Contribution à l'étude des propriétés de transport de quelques oxydes métalliques et supraconducteurs de basse dimensionnalité." Grenoble 1, 1988. http://www.theses.fr/1988GRE10157.

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Les proprietes de transport (magnetoconductivite, effet hall, ondes de densite de charge, ondes de densite de spin, transitions supraconductrices) des oxydes metalliques et supraconducteurs quasi-bidimensionnels sont etudiees a basse temperature

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47

Fiedler, Holger. "Preparation and characterization of Carbon Nanotube based vertical interconnections for integrated circuits." Doctoral thesis, Universitätsbibliothek Chemnitz, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-149474.

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(ULSI) causes an increase of the resistance of the wiring system by increased scattering of electrons at side walls and grain boundaries in the state of the art Cu technology, which increases the RC delay of the interconnect system and thus degrades the performance of the device. The outstanding properties of carbon nanotubes (CNT) such as a large mean free path, a high thermal conductance and a large resistance against electromigration make them an ideal candidate to replace Cu in future feature nodes. The present thesis contributes to the preparation and properties of CNT based vertical interconnections (vias). In addition, all processes applied during the fabrication are compatible to ULSI and an interface between CNT based vias and a Cu metallization is studied. The methodology for the evaluation of CNT based vias is improved; it is highlighted that by measuring the resistance of one multiwall CNT and taking into account the CNT density, the performance of the CNT based vias can be predicted accurately. This provides the means for a systematic evaluation of different integration procedures and materials. The lowest contact resistance is obtained for carbide forming metals, as long as oxidation during the integration is avoided. Even though metal-nitrides exhibit an enhanced contact resistance, they are recommended to be used at the bottom metallization in order to minimize the oxidation of the metal-CNT contact during subsequent processing steps. Overall a ranking for the materials from the lowest to the highest contact resistance is obtained: Ta < Ti < TaN < TiN « TiO2 « Ta2O5 Furthermore the impact of post CNT growth procedures as chemical mechanical planarization, HF treatment and annealing procedures after the CNT based via fabrication are evaluated. The conductance of the incorporated CNTs and the applicable electrical transport regime relative to the CNT quality and the CNT length is discussed. In addition, a strong correlation between the temperature coefficient of resistance and the initial resistance of the CNT based vias at room temperature has been observed
Die kontinuierliche Miniaturisierung der charakteristischen Abmessungen in hochintegrierten Schaltungen (ULSI) verursacht einen Anstieg des Widerstandes im Zuleitungssystem aufgrund der erhöhten Streuung von Elektronen an Seitenwänden und Korngrenzen in der Cu-Technologie, wodurch die Verzögerungszeit des Zuleitungssystems ansteigt. Die herausragenden Eigenschaften von Kohlenstoffnanoröhren (CNT), wie eine große mittlere freie Weglänge, hohe thermische Leitfähigkeit und eine starke Resistenz gegenüber Elektromigration machen diese zu einem idealen Kandidaten, um Cu in zukünftigen Technologiegenerationen zu ersetzen. Die vorliegende Arbeit beschreibt die Herstellung und daraus resultierenden Eigenschaften von Zwischenebenenkontakten (Vias) basierend auf CNTs. Alle verwendeten Prozessierungsschritte sind kompatibel mit der Herstellung von hochintegrierten Schaltkreisen und eine Schnittstelle zwischen den CNT Vias und einer Cu-Metallisierung ist vorhanden. Insbesondere das Verfahren zur Evaluierung von CNT Vias wurde durch den Einsatz verschiedener Methoden verbessert. Insbesondere soll hervorgehoben werden, dass durch die Messung des Widerstandes eines einzelnen CNTs, bei bekannter CNT Dichte, der Via Widerstand sehr genau vorausgesagt werden kann. Dies ermöglicht eine systematische Untersuchung des Einflusses der verschiedenen Prozessschritte und der darin verwendeten Materialien auf den Via Widerstand. Der niedrigste Kontaktwiderstand wird für Karbidformierende Metalle erreicht, solange Oxidationsprozesse ausgeschlossen werden können. Obwohl Metallnitride einen höheren Kontaktwiderstand aufweisen, sind diese für die Unterseitenmetallisierung zu empfehlen, da dadurch die Oxidation der leitfähigen Schicht minimiert wird. Insgesamt kann eine Reihenfolge beginnend mit dem niedrigsten zum höchsten Kontaktwiderstand aufgestellt werden: Ta < Ti < TaN < TiN « TiO2 « Ta2O5 Desweiteren wurde der Einfluss von Verfahren nach dem CNTWachstum wie die chemischmechanische Planarisierung, eine HF Behandlung und einer Temperaturbehandlung evaluiert, sowie deren Einfluss auf die elektrischen Parameter des Vias untersucht. Die Leitfähigkeit der integrierten CNTs und die daraus resultierenden elektrischen Transporteigenschaften in Abhängigkeit der CNT Qualität und Länge werden besprochen. Ebenso wird die starke Korrelation zwischen dem Temperaturkoeffizienten des elektrischen Widerstandes und des Ausgangswiderstandes der CNT basierten Vias bei Raumtemperatur diskutiert

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48

Fiedler, Holger. "Preparation and characterization of Carbon Nanotube based vertical interconnections for integrated circuits: Preparation and characterization of Carbon Nanotube based verticalinterconnections for integrated circuits." Doctoral thesis, Universitätsverlag der Technischen Universität Chemnitz, 2013. https://monarch.qucosa.de/id/qucosa%3A20091.

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(ULSI) causes an increase of the resistance of the wiring system by increased scattering of electrons at side walls and grain boundaries in the state of the art Cu technology, which increases the RC delay of the interconnect system and thus degrades the performance of the device. The outstanding properties of carbon nanotubes (CNT) such as a large mean free path, a high thermal conductance and a large resistance against electromigration make them an ideal candidate to replace Cu in future feature nodes. The present thesis contributes to the preparation and properties of CNT based vertical interconnections (vias). In addition, all processes applied during the fabrication are compatible to ULSI and an interface between CNT based vias and a Cu metallization is studied. The methodology for the evaluation of CNT based vias is improved; it is highlighted that by measuring the resistance of one multiwall CNT and taking into account the CNT density, the performance of the CNT based vias can be predicted accurately. This provides the means for a systematic evaluation of different integration procedures and materials. The lowest contact resistance is obtained for carbide forming metals, as long as oxidation during the integration is avoided. Even though metal-nitrides exhibit an enhanced contact resistance, they are recommended to be used at the bottom metallization in order to minimize the oxidation of the metal-CNT contact during subsequent processing steps. Overall a ranking for the materials from the lowest to the highest contact resistance is obtained: Ta < Ti < TaN < TiN « TiO2 « Ta2O5 Furthermore the impact of post CNT growth procedures as chemical mechanical planarization, HF treatment and annealing procedures after the CNT based via fabrication are evaluated. The conductance of the incorporated CNTs and the applicable electrical transport regime relative to the CNT quality and the CNT length is discussed. In addition, a strong correlation between the temperature coefficient of resistance and the initial resistance of the CNT based vias at room temperature has been observed.
Die kontinuierliche Miniaturisierung der charakteristischen Abmessungen in hochintegrierten Schaltungen (ULSI) verursacht einen Anstieg des Widerstandes im Zuleitungssystem aufgrund der erhöhten Streuung von Elektronen an Seitenwänden und Korngrenzen in der Cu-Technologie, wodurch die Verzögerungszeit des Zuleitungssystems ansteigt. Die herausragenden Eigenschaften von Kohlenstoffnanoröhren (CNT), wie eine große mittlere freie Weglänge, hohe thermische Leitfähigkeit und eine starke Resistenz gegenüber Elektromigration machen diese zu einem idealen Kandidaten, um Cu in zukünftigen Technologiegenerationen zu ersetzen. Die vorliegende Arbeit beschreibt die Herstellung und daraus resultierenden Eigenschaften von Zwischenebenenkontakten (Vias) basierend auf CNTs. Alle verwendeten Prozessierungsschritte sind kompatibel mit der Herstellung von hochintegrierten Schaltkreisen und eine Schnittstelle zwischen den CNT Vias und einer Cu-Metallisierung ist vorhanden. Insbesondere das Verfahren zur Evaluierung von CNT Vias wurde durch den Einsatz verschiedener Methoden verbessert. Insbesondere soll hervorgehoben werden, dass durch die Messung des Widerstandes eines einzelnen CNTs, bei bekannter CNT Dichte, der Via Widerstand sehr genau vorausgesagt werden kann. Dies ermöglicht eine systematische Untersuchung des Einflusses der verschiedenen Prozessschritte und der darin verwendeten Materialien auf den Via Widerstand. Der niedrigste Kontaktwiderstand wird für Karbidformierende Metalle erreicht, solange Oxidationsprozesse ausgeschlossen werden können. Obwohl Metallnitride einen höheren Kontaktwiderstand aufweisen, sind diese für die Unterseitenmetallisierung zu empfehlen, da dadurch die Oxidation der leitfähigen Schicht minimiert wird. Insgesamt kann eine Reihenfolge beginnend mit dem niedrigsten zum höchsten Kontaktwiderstand aufgestellt werden: Ta < Ti < TaN < TiN « TiO2 « Ta2O5 Desweiteren wurde der Einfluss von Verfahren nach dem CNTWachstum wie die chemischmechanische Planarisierung, eine HF Behandlung und einer Temperaturbehandlung evaluiert, sowie deren Einfluss auf die elektrischen Parameter des Vias untersucht. Die Leitfähigkeit der integrierten CNTs und die daraus resultierenden elektrischen Transporteigenschaften in Abhängigkeit der CNT Qualität und Länge werden besprochen. Ebenso wird die starke Korrelation zwischen dem Temperaturkoeffizienten des elektrischen Widerstandes und des Ausgangswiderstandes der CNT basierten Vias bei Raumtemperatur diskutiert.

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49

Maurel, Philippe. "Contribution a l'etude des proprietes physiques des composes ga : :(x)in::(1-x)as::(y)p::(1-y) obtenus par croissance en phase vapeur par la methode des organometalliques." Paris 6, 1987. http://www.theses.fr/1987PA066517.

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Etude des proprietes electriques et optiques a basse temperature dans inp de haute purete. Observation de l'effet hall quantique par etude detaillee de proprietes de transport des porteurs bidimensionnels a l'heterojoncion, a dopage module de type p ou n dans inp/ga::(0,47) in::(0,53) as et inp/ga::(0,25) in::(0,75) as::(0,5) p::(0,5). Etude des proprietes structurelles et optiques des puits quantiques multiples inp/ga::(0,47) in::(0,53) as

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50

Ahmed, Mustafa M. Abdalla. "Alternating-Current Thin-Film Electroluminescent Device Characterization." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-233432.

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Jádrem této disertační práce bylo studovat optické a elektrické charakteristiky tenkovrstvých elektroluminiscenčních součástek řízených střídavým proudem (ACTFEL) a zejména vliv procesu stárnutí luminiforů na jejich optické a elektrické vlastnosti. Cílem této studie měl být příspěvek ke zvýšení celkové účinnosti luminoforů, vyjádřené pomocí jasu, účinnosti a stability. Vzhledem k tomu, že současnou dominantní technologií plochých obrazovek je LCD, musí se další alternativní technologie plošných displejů porovnávat s LCD. Výhodou ACTFEL displejů proti LCD je lepší rozlišení, větší teplotní rozsah činnosti, větší čtecí úhel, či možnost čtení při mnohem vyšší intenzitě pozadí. Na druhou stranu je jejich nevýhodou vyšší energetická náročnost, problém s odpovídající barevností tří základních barev a podstatně vyšší napětí nutné pro činnost displeje. K dosažení tohoto cíle jsme provedli optická, elektrická a optoelektrická měření ACTFEL struktur a ZnS:Mn luminoforů. Navíc jsme studovali vliv dotování vrstvy pomocí KCl na chování mikrostruktury a na elektroluminiscenční vlastnosti (zejména na jas a světelnou účinnost) ZnS:Mn luminoforů. Provedli jsme i některá, ne zcela obvyklá, měření ACTFEL součástek. Vypočítali jsme i rozptylový poměr nabitých barevných center a simulovali transportní charakteristiky v ACTFEL součástkách. Studovali jsme vliv stárnutí dvou typů ZnS:Mn luminoforů (s vrstvou napařenou či získanou pomocí epitaxe atomových vrstev) monitorováním závislostí svítivost-napětí (L-V), velikost vnitřního náboje - elektrické pole luminoforu (Q-Fp) a kapacitance-napětí (C-V) ve zvolených časových intervalech v průběhu stárnutí. Provedli jsme krátkodobá i dlouhodobá měření a pokusili jsme se i o vizualizaci struktury luminoforu se subvlnovým rozlišením pomocí optického rastrovacího mikroskopu pracujícího v blízkém poli (SNOM). Na praktickém případu zeleného Zn2GeO4:Mn (2% Mn) ACTFEL displeje, pracujícího při 50 Hz, jsme také studovali stabilitu svítivosti pomocí měření závislosti svítivosti na napětí (L-V) a světelné účinnosti na napětí (eta-V). Přitom byl zhodnocen význam těchto charakteristik. Nezanedbatelnou a neoddělitelnou součástí této práce je i její pedagogický aspekt. Předložený text by mohl být využit i jako učebnice pro studenty na mé univerzitě v Lybii.

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Dissertations / Theses on the topic 'Temperature dependent electrical transport'

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