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Dissertations / Theses on the topic 'Dielectric Materials'
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1
Blandin, Christopher. "Production of dielectric materials." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26568.
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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Colton, Jonathan; Committee Member: Schultz, John; Committee Member: Zhou, Min. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Barelli, Eleonora. "Dielectric relaxation in biological materials." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9102/.
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The study of dielectric properties concerns storage and dissipation of electric and magnetic energy in materials. Dielectrics are important in order to explain various phenomena in Solid-State Physics and in Physics of Biological Materials.
Indeed, during the last two centuries, many scientists have tried to explain and model the dielectric relaxation. Starting from the Kohlrausch model and passing through the ideal Debye one, they arrived at more com- plex models that try to explain the experimentally observed distributions of relaxation times, including the classical (Cole-Cole, Davidson-Cole and Havriliak-Negami) and the more recent ones (Hilfer, Jonscher, Weron, etc.).
The purpose of this thesis is to discuss a variety of models carrying out the analysis both in the frequency and in the time domain. Particular attention is devoted to the three classical models, that are studied using a transcendental function known as Mittag-Leffler function. We highlight that one of the most important properties of this function, its complete monotonicity, is an essential property for the physical acceptability and realizability of the models.
Lo studio delle proprietà dielettriche riguarda l’immagazzinamento e la dissipazione di energia elettrica e magnetica nei materiali. I dielettrici sono importanti al fine di spiegare vari fenomeni nell’ambito della Fisica dello Stato Solido e della Fisica dei Materiali Biologici.
Infatti, durante i due secoli passati, molti scienziati hanno tentato di spiegare e modellizzare il rilassamento dielettrico. A partire dal modello di Kohlrausch e passando attraverso quello ideale di Debye, sono giunti a modelli più complessi che tentano di spiegare la distribuzione osservata sperimentalmente di tempi di rilassamento, tra i quali modelli abbiamo quelli classici (Cole-Cole, Davidson-Cole e Havriliak-Negami) e quelli più recenti (Hilfer, Jonscher, Weron, etc.).
L’obiettivo di questa tesi è discutere vari modelli, conducendo l’analisi sia nel dominio delle frequenze sia in quello dei tempi. Particolare attenzione è rivolta ai tre modelli classici, i quali sono studiati utilizzando una funzione trascendente nota come funzione di Mittag-Leffler. Evidenziamo come una delle più importanti proprietà di questa funzione, la sua completa monotonia, è una proprietà essenziale per l’accettabilità fisica e la realizzabilità dei modelli.
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Pliakostathis, Konstantinos. "Novel dielectric resonator antennas based on high permettivity dielectric materials." Thesis, University of Essex, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410507.
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Cho, Taiheui. "Anisotropy of low dielectric constant materials and reliability of Cu/low-k interconnects /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Gulia, Kiran. "Pulsed laser processing of dielectric materials." Thesis, Heriot-Watt University, 2007. http://hdl.handle.net/10399/2035.
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The thesis investigates the wavelength dependent laser ablp..~ion in dielectric materials used for the fabrication ofhigh density Printed Circuit Boards (PCBs) in the electronics industry. Here the market for consumer and industrial products of ever-rising complexity has led to a demand for increased miniaturisation and low costs of multilevel printed circuit boards (PCBs) interconnected by microvias, which electrically connect the various circuit layers. Laser machining offers a potential solution to this need. The main objective of the research is to investigate the wavelength-dependence of the laser machining/drilling efficiency of two important sets of PCB materials, categorised as Organics and Ceramics using a carbon dioxide laser which can be tuned across its emission spectrum in the 9flm - 11 flm spectral region.. The organics include commercially available electronic materials with trade names such as Kapton, ArIon, FR4 and RCC and the ceramics materials studied are alumina and low temperature cofired ceramic (LTCC). The aim is to determine the optimum laser wavelength for maximum processing efficiency Le. to find the wavelength where the laser parameters are best matched to the optical, thermal and mechanical properties of each of the materials. A CO2 laser machining system was constructed which incorporated a novel laser source developed in the research programmes. The laser source was a MOPA system with a line-tuneable cw oscillator and a five pass power planar waveguide rf discharge-excited power operating in the so-called enhanced power regime to produce maximum peak power. An Acousto-optic modulator between the master oscillator and the amplifier allowed convenient control of pulse amplitude and duration. The system enabled the wavelength dependent studies on the wavelength and pulse energy dependence of the laser ablation properties (e.g. ablation threshold fluence and ablation rates) - to derive the so-called 'ablation spectrum' of the selected materials A comparison is made of the wavelength dependence of ablation with the room temperature absorption spectrum measured for each material using ellipsometry. It was observed that the 'ablation spectrum' information does not always appear to match the simple expectations derived from the room temperature 'absorption spectrum' of the material. This disparity in results is likely due to the change of absorption properties of • material because of rise in temperature, chemical decomposition or melting of material during ablation. However, the room temperature absorption spectrum (while not adequate alone), did provide a useful guide to the selection of a sub-set of the 40+ lines that would otherwise have to be studied. The results may be of direct application in the electronics industry to increase the efficiency oflaser machining.
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Zhou, Yuan. "Modeling and Simulation of Dielectric Materials." University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1185810210.
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Killian, Tyler Norton Rao S. M. "Numerical modeling of very thin dielectric materials." Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SUMMER/Electrical_and_Computer_Engineering/Thesis/Killian_Tyler_16.pdf.
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Martini, David M. "Metallization and Modification of Low-k Dielectric Materials." Thesis, University of North Texas, 2008. https://digital.library.unt.edu/ark:/67531/metadc9754/.
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Aluminum was deposited onto both Teflon AF and Parylene AF surfaces by chemical vapor deposition of trimethylaluminum. This work shows that similar thin film (100 Angstroms) aluminum oxide adlayers form on both polymers at the low temperature dosing conditions used in the studies. Upon anneal to room temperature and above, defluorination of the polymer surfaces increased and resulted in fluorinated aluminum oxide adlayers; the adlayers were thermally stable to the highest temperatures tested (600 K). Angle-resolved spectra showed higher levels of fluorination toward the polymer/adlayer interface region. Copper films were also deposited at low temperature onto Teflon AF using a copper hexafluoroacetylacetonate-cyclooctadiene precursor. Annealing up to 600 K resulted in the loss of precursor ligands and a shift to metallic copper. As with aluminum adlayers, some polymer defluorination and resulting metal (copper) fluoride was detected. Parylene AF and polystyrene films surfaces were modified by directly dosing with water vapor passed across a hot tungsten filament. Oxygen incorporation into polystyrene occurred exclusively at aromatic carbon sites, whereas oxygen incorporation into parylene occurred in both aromatic and aliphatic sites. Oxygen x-ray photoelectron spectra of the modified polymers were comparable, indicating that similar reactions occurred. The surface oxygenation of parylene allowed enhanced reactivity toward aluminum chemical vapor deposition. Silicon-carbon (Si-Cx) films were formed by electron beam bombardment of trimethylvinylsilane films which were adsorbed onto metal substrates at low temperatures in ultra-high vacuum. Oxygen was also added to the films by coadsorbing water before electron beam bombardment; the films were stable to more than 700 K, with increasing silicon-oxygen bond formation at elevated temperatures. Copper metal was sputter deposited in small increments onto non-oxygenated films. X-ray photoelectric spectra show three-dimensional copper growth (rather than layer-by-layer growth), indicating only weak interaction between the copper and underlying films. Annealing at elevated temperatures caused coalescence or growth of the copper islands, with spectra indicating metallic copper rather than copper oxide.
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Anwar, M. "Spectroscopic investigations of amorphous complex dielectric materials." Thesis, Brunel University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234036.
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Yu, Chuying. "Dielectric materials for high power energy storage." Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/24852.
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Energy storage is currently gaining considerable attention due to the current energy crisis and severe air pollution. The development of new and clean forms of energy and related storing devices is in high demanded. Dielectric capacitors, exhibiting high power density, long life and cycling life, are potential candidates for portable devices, transport vehicles and stationary energy resources applications. However, the energy density of dielectric capacitors is relatively low compared to that of traditional batteries, which inhibits their future development. In the current work, three types of dielectrics, namely antiferroelectric samarium-doped BiFeO3 (Bi1-xSmxFeO3), linear dielectric (potential antiferroelectric) BiNbO4 and incipient ferroelectric TiO2, have been investigated to develop their potential as energy storage capacitors. For the samarium-doped BiFeO3 (Bi1-xSmxFeO3) system, the effect of samarium content in the A-site (x=0.15, 0.16, 0.165 and 0.18) on the structural phase transitions and electrical properties across the Morphotropic Phase Boundary (MPB) were studied. A complex coexistence of rhombohedral R3c, orthorhombic Pbam and orthorhombic Pnma was found in the selected compositions. The R3c phase is the structure of pure BiFeO3, the Pbam phase has a PbZrO3-like antiferroelectric structure and the Pnma phase has a SmFeO3-like paraelectric structure. The presence of the PbZrO3-like antiferroelectric structure was confirmed by the observation of the 14{110}, 14{001}, 12{011} and 12{111} superlattice reflections in the transmission electron microscopy diffraction patterns. The weight fractions of the three phases varied with different calcination conditions and Sm substitution level. By increasing the calcination temperature, the weight fractions of the Pbam increased, while that of the R3c decreased. The fraction of the Pnma phase is mainly derived by the Sm concentration and is barely affected by the calcination temperature. The increase of Sm concentration, determined an increase of the weight fraction of the Pnma phase and a decrease of the Pbam and the R3c phases. Temperature dependent dielectric measurements and high temperature XRD of Bi0.85Sm0.15FeO3 revealed several phase transitions. The drastic weight fraction change between the Pbam and the Pnma phase around 200 °C is assumed as the Curie transition of the antiferroelectric Pbam phase. The transition at 575 °C is related to the diminishing of the R3c phase and is suggested as the Curie transition of the ferroelectric R3c phase. The Curie point of the antiferroelectric Pbam phase and the ferroelectric R3c phase in the Bi1-xSmxFeO3 ceramics shifted towards lower temperature with an increase of the Sm concentration. Current peaks were obtained in current-electric field loops in Bi0.85Sm0.15FeO3, which are correlated to domain switching in the R3c phase. The ferroelectric behavior was suppressed in Bi1-xSmxFeO3 (x=0.16, 0.165, 0.18), which is due to the gradually diminished contribution from the R3c phase. The system Bi0.82Sm0.18FeO3 showed the highest energy density of 0.64 J cm-3 (error bar ±0.02). For the BiNbO4 system, single phase α-BiNbO4 (space group Pnna) and β-BiNbO4 (space group P-1) powder and ceramics were produced. The longstanding issue related to the sequence of the temperature-induced phase transitions has been clarified. It is demonstrated that the β phase powder could be converted back to the phase when annealed in the temperature range 800 °C -1000 °C with certain incubation time. The β to phase transition is a slow kinetic process because sufficient temperature and time are required for the transition. In bulk ceramics with β phase, this transformation is impeded by inner stress, while it is favored by graphite-induced reducing atmosphere. A high temperature phase has been revealed and the structure has been resolved. The structure of the phase is monoclinic with a space group of P21/c. The lattice parameters are: a = 7.7951(1) Å, b = 5.64993(9) Å, c = 7.9048(1) Å, = 104.691(2) Z=4. The volume is 336.76 (2) Å3. The calculated density is 7.217 g cm-3. The phase relationships among , and phases have been clarified. It was found that the phase (for both powder and ceramic) transforms into the phase at 1040 °C on heating, and that the phase always transforms into the phase at 1000 °C on cooling. Meanwhile, a reversible first-order to phase transition is observed at ca. 1000 °C for both powder and ceramic if no incubation is processed on heating. The electric properties of both α- and - BiNbO4 have been investigated. The breakdown field of both ceramics were too low to observe any possible field-induced transition. As a result, linear P-E loops were obtained in each phase. The energy densities of α- and - BiNbO4 ceramics are 0.03 and 0.04 J cm-3 (error bar ±0.001), respectively. For the TiO2 system, ceramics were produced by conventional sintering and spark plasma sintering (SPS). Compared to conventional sintering, SPS technique produced dense ceramics without using sintering aids and avoided abnormal grain growth. Relaxation behavior related to the oxygen hopping among vacant sites is observed in the temperature range of 200 to 600 °C. TiO2 exhibits ultra-low loss at terahertz frequencies due to the reduced contribution of oxygen vacancies relaxation. TiO2 has a high breakdown field, but still has low polarization. The highest energy density obtained inTiO2 ceramics is 0.3 J cm-3 (error bar ±0.01).
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Lisachuk, G. V., R. V. Kryvobok, Y. M. Pitak, O. Lapuzina, N. A. Kryvobok, and N. S. Maystat. "Radio-absorbing materials with adjustable dielectric properties." Thesis, Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, 2018. http://repository.kpi.kharkov.ua/handle/KhPI-Press/38982.
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Braganza, Clinton Ignatuis. "High Dielectric Constant Materials Containing Liquid Crystals." Kent State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=kent1248065159.
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Umaña, Juan Antonio. "Measurement of complex dielectric permittivity of pavement materials." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0004/MQ32519.pdf.
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Hunt-Lowery, Alisa. "STATISTICAL ANALYSIS OF NOVEL DIELECTRIC MATERIALS FOR MICROELECTRONICS." NCSU, 2004. http://www.lib.ncsu.edu/theses/available/etd-09212004-100243/.
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This research analyzes the re-oxidation annealing process of Barium titanate thin films on copper foils made by Chemical Solution Deposition. During this anneal, the temperature and oxygen pressure settings must be optimized to ensure the elimination of oxygen vacancies without oxidizing the copper foil substrate. This research utilizes Design of Experiments (DOE) to study the impact of re-oxidation furnace temperature and pressure on the dielectric loss tangent response. Two designs of experiments were run. The first experiment, a 32 DOE, examined a large range of temperature and pressure levels. Due to the high susceptibility of uncontrollable factors such as humidity and film position in the crystallization anneal furnace, an adequate model could not be developed. However, the temperature at 550ºC and a pressure of 10-5 Torr yielded a lower mean and standard deviation of the loss tangent response. A second and smaller scale experiment, a 22 with a center point, was run around 550ºC and 10-5 Torr to determine if more optimal temperature and pressure settings existed in the local area. Two second order response surface models were developed from two crystallization anneals that were statistically significant. The most significant finding was that the optimum level for temperature and pressure in the re-oxidation anneal furnace in this experiment is 550ºC and 2x10-5 Torr. While the models concluded that the temperature, pressure, temperature quadratic, and interaction between pressure and temperature were important effects in the model, there were differences in the curvature of the models due to the temperature quadratic effect.
15
Farsari, Maria. "Dielectric and optical properties of organic photorefractive materials." Thesis, Durham University, 1996. http://etheses.dur.ac.uk/5226/.
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The work presented in this thesis is derived from experimentation in the field of polymeric photorefractive materials. Low T(_g) polymeric composites were prepared, based on the well-known photoconductive polymer PVK (maximum 50% w/w), sensitized with TNF (2% w/w) and C(_60) (0.2% w/w), plasticized with ECZ (maximum 49.3% w/w) and doped with the nonlinear optical materials NPP (50% w/w), DAN (20% w/w), DED (5% w/w), DCNQI (0.5% w/w), ULTRA-DEMI (5% w/w) and DI-DEMI (2% w/w), and their dielectric, linear and non linear optical properties were investigated. All the materials, except DCNQI, exhibited good solubility and sample processibility. The dielectric properties of the composites at 1 KHz and 1 MHz were determined using a parallel-plate capacitance bridge. The dielectric constant and loss at 10 GHz were measured using a novel adaptation of the resonant cavity technique, which was designed for measurements at ambient and elevated temperatures. The method was used to measure of the dielectric constant and loss of two novel, high T(_g), electro-optic polymers at temperatures up to 100 ºC. The dielectric properties measured were typical of polymeric materials. The absorption coefficient and the refractive index at different wavelengths were measured using a spectrophotometer. For the refractive index, an interference fringe analysis was used. The nonlinear measurements consisted of second harmonic generation, to prove the nonhnearity of the composites, two-beam coupling measurements, to prove their photorefractivity and degenerate four-wave mixing to measure their diffraction efficiency. The NPP, DAN, DED and ULTRA-DEMI doped investigated composites exhibited second order nonlinearity with highest the one of ULTRA-DEMI, at 292 pm/V for 19 kV of corona poling field. The photorefractivity of the NPP, DAN and DED doped composites was proven at 632.8 nm, while ULTRA-DEMI doped composites photooxidized before any measurements were possible. The two-beam coupling coefficients measured were lower than 20 cm(^-3), while net gain was observed only in the NPP doped composite. The diffraction efficiencies of the NPP, DAN and DED doped composites were measured at 632.8 nm, and were found to be l0(^-5)-l0(^-6).
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Rybak, Michelle (Michelle A. ). "Characterizing dielectric materials with a feedback-based model." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91866.
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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 54-55).
As signal frequencies continue to increase, conductor surface roughness losses of interconnects are becoming more prominent. There is currently no industry standard for separating the dielectric and conductor losses that appear in PCBs. As part of the thesis work, test vehicles composed of six different dielectric materials were fabricated with different trace widths, copper foil profiles, and oxide surface treatments. A Feedback-Based Model was used to simulate and extract the dielectric and conductor losses from measurements made with the different test vehicles. Simulation software such as MATLAB, Agilent ADS, and Polar Si9000 were utilized. Dielectric material Megtron 4 had the lowest Df of the materials of interest. The Feedback Based Model was able to fit the data well for either low frequencies and high frequencies, but not both. Further, the model was able to model the effects of changes in copper roughness well. Small variations were seen in the extracted Df associated with changes in width of the measurement traces.
by Michelle Rybak.
M. Eng.
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Lazraq, Byström Joseph. "Characterization of Magneto-Dielectric Materials for Microwave Devices." Thesis, Uppsala universitet, Fasta tillståndets elektronik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-419515.
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There is an increasing interest in using new composite materials in microwave devices, to reduce size and weight while maintaining similar performances. A new promising material group is named magneto-dielectric materials, which have the permittivity and permeability values both larger than one. Compared to the commercially used dielectric materials, magneto-dielectric materials can achieve a larger miniaturization factor with the equivalent properties as dielectric materials. There is a very limited availability of commercial magneto-dielectric materials. A recent addition was from Rogers Corporation with MAGTREX 555, [1], that is available as a printed circuit board laminate. The material is limited to 500 MHz operational frequency due to its increased magnetic and dielectric losses. In this thesis the purpose is to understand the loss mechanisms, characterize and understand the state-of-the-art magneto-dielectric materials at microwaves, and to produce a magneto-dielectric material in the lab to understand the material better. A new material was developed with magneto-dielectric properties. The material was based on a polymer base of polystyrene that serves as a dielectric material and doped with nickel nanoparticles that produce the magnetic properties. The contents of the nanoparticles in the mix is a design variable. Nickel-polystyrene samples with different nickel contents of 0%, 2.3% and 4.5%, were produced in the lab and measured in-house to understand the loss mechanism and RF performance.
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Tanner, Carey Marie. "Engineering high dielectric constant materials on silicon carbide." Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1459913391&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Martini, David M. Kelber Jeffry Alan. "Metallization and modification of low-k dielectric materials." [Denton, Tex.] : University of North Texas, 2008. http://digital.library.unt.edu/permalink/meta-dc-9754.
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Abbas, Zulkifly. "Determination of the dielectric properties of materials at microwave frequencies using rectangular dielectric waveguide." Thesis, University of Leeds, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.569541.
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Han, Lei. "Investigation of Gate Dielectric Materials and Dielectric/Silicon Interfaces for Metal Oxide Semiconductor Devices." UKnowledge, 2015. http://uknowledge.uky.edu/ece_etds/69.
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The progress of the silicon-based complementary-metal-oxide-semiconductor (CMOS) technology is mainly contributed to the scaling of the individual component. After decades of development, the scaling trend is approaching to its limitation, and there is urgent needs for the innovations of the materials and structures of the MOS devices, in order to postpone the end of the scaling. Atomic layer deposition (ALD) provides precise control of the deposited thin film at the atomic scale, and has wide application not only in the MOS technology, but also in other nanostructures. In this dissertation, I study rapid thermal processing (RTP) treatment of thermally grown SiO2, ALD growth of SiO2, and ALD growth of high-k HfO2 dielectric materials for gate oxides of MOS devices. Using a lateral heating treatment of SiO2, the gate leakage current of SiO2 based MOS capacitors was reduced by 4 order of magnitude, and the underlying mechanism was studied. Ultrathin SiO2 films were grown by ALD, and the electrical properties of the films and the SiO2/Si interface were extensively studied. High quality HfO2 films were grown using ALD on a chemical oxide. The dependence of interfacial quality on the thickness of the chemical oxide was studied. Finally I studied growth of HfO2 on two innovative interfacial layers, an interfacial layer grown by in-situ ALD ozone/water cycle exposure and an interfacial layer of etched thermal and RTP SiO2. The effectiveness of growth of high-quality HfO2 using the two interfacial layers are comparable to that of the chemical oxide. The interfacial properties are studied in details using XPS and ellipsometry.
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Seo, Cheong Soo. "Electromechanics of dielectric particles in dielectric liquids acted on by a microelectrode array." Texas A&M University, 2005. http://hdl.handle.net/1969.1/3301.
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Arrays of microelectrodes were used to apply forces to dielectric (soda lime glass)
spheres in a thin (200 micrometer thick) layer of a dielectric liquid polymer (EOPN
8021). The microelectrodes were fabricated using standard photolithographic methods of
evaporating and electroplating gold onto a glass substrate. The objective is to use the
electric body forces in the sphere and the electric surface tractions on the sphere to
position the spheres in a microscale pattern, in this case a square array in-plane.
Three sizes of spheres were used: 30, 90, and 170 microns in diameter. The 30
micron spheres formed clusters associated with the regions of highest electric energy
density, whereas single 90 micron spheres were located at the regions of highest electric
energy density. The 170 micron spheres generally did not form patterns. The
experiments indicated that free charges, either in the volume of the sphere and/or on the
sphere surface, significantly influence the motion of the sphere.
A finite element analysis was performed to study the electro-fluid mechanics.
The liquid velocity and streamlines were plotted, and the force resultants due to the
liquid acting on the sphere were calculated. Also, the electric body force and surface tractions resultants were calculated. In general, the forces on the sphere and the liquid
velocity are in agreement with the experimental results.
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Addington, J. Shawn. "Wideband electrical characterization of multilayer low-loss dielectric materials." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-10312009-020154/.
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Sun, Minwei. "Applying zeolites as low dielectric constant (low-k) materials." Diss., UC access only, 2009. http://proquest.umi.com/pqdweb?index=14&did=1907180231&SrchMode=1&sid=4&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1270059102&clientId=48051.
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Alshami, Ali Saleh. "Dielectric properties of biological materials : a physical-chemical approach." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Dissertations/Spring2007/A_Alshami_053107.pdf.
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McGowan, Brian Thomas. "Magnetoresistance of a Low-k Dielectric." Thesis, State University of New York at Albany, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10100441.
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Low-k dielectrics have been incorporated into advanced computer chip technologies as a part of the continuous effort to improve computer chip performance. One drawback associated with the implementation of low-k dielectrics is the large leakage current which conducts through the material, relative to silica. Another drawback is that the breakdown voltage of low-k dielectrics is low, relative to silica [1]. This low breakdown voltage makes accurate reliability assessment of the failure mode time dependent dielectric breakdown (TDDB) in low-k dielectrics critical for the successful implementation of these materials. The accuracy with which one can assess this reliability is currently a topic of debate.
These material drawbacks have motivated the present work which aims both to contribute to the understanding of electronic conduction mechanisms in low-k dielectrics, and to improve the ability to experimentally characterize changes which occur within the material prior to TDDB failure. What follows is a study of the influence of an applied magnetic field on the conductivity of a low-k dielectric, or in other words, a study of the material’s magnetoresistance.
This study shows that low-k dielectrics used as intra-level dielectrics exhibit a relatively large negative magnetoresistance effect (∼2%) at room temperature and with modest applied magnetic fields (∼100 Oe). The magnetoresistance is attributed to the spin dependence of trapping electrons from the conduction band into localized electronic sites. Mixing of two-electron spin states via interactions between electron spins and the the spins of hydrogen nuclei is suppressed by an applied magnetic field. As a result, the rate of trapping is reduced, and the conductivity of the material increases.
This study further demonstrates that the magnitude of the magnetoresistance changes as a function of time subjected to electrical bias and temperature stress. The rate that the magnetoresistance changes correlates to the intensity with which the material was stressed. It is postulated that the change in magnetoresistance which occurs as a result of bias temperature stress could be used as an alias for measuring the degradation which contributes to TDDB.
Finally, it is shown that the magnetoresistance behavior is non-monotonic. That is, for small values of applied magnetic field (∼2 Oe) the conductivity initially decreases, while for further increase of the magnetic field the conductivity increases to a saturation. The non-monotonic behavior is consistently described in the context of competing spin mixing mechanisms.
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Nakhwal, Jaspal Singh. "Investigation of microwave converters using Perovskite-type materials." Thesis, Leeds Beckett University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314814.
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Azari, Arash. "Casimir effect in presence of dielectric and metallic materials." Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531132.
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McLaughlin, Bryan L. "Biological materials characterisation using microwave and optical dielectric spectroscopy." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612520.
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Hartley, Jon. "Simultaneous structural and dielectric measurement of ammonia storage materials." Thesis, Cardiff University, 2015. http://orca.cf.ac.uk/89378/.
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The principal aims of this thesis are to design, build and experiment with simultaneous measurement systems, designed to measure ammonia adsorption in a wide range of sample materials. These simultaneous measurement systems will integrate dielectric spectroscopy methods with structural analysis techniques in order to obtain a more complete understanding of the dynamic adsorption processes that occur. Some of the new and most promising materials for ammonia storage applications are tested in this thesis in order to understand the possible strengths and weaknesses that these materials have in becoming used in real world applications. Dielectric spectroscopy in this thesis is achieved by using microwave resonant structures. These devices measure permittivity, dielectric losses and electrical conduction by way of the cavity perturbation technique. Structural analysis is conducted by way of neutron and X-ray diffraction, both of these measurement techniques give insight into the crystal structure of materials. With these two measurement techniques, changes in bulk material properties (measured from the dielectric spectroscopy) can be compared and contrasted with changes in the crystal structure (measured from the diffraction techniques). The materials tested within the simultaneous measurement systems were alkali earth and transition metal halides. On introducing gaseous ammonia to these materials, the dielectric properties and molecular structure changed. Using the combined information from multiple measurement techniques, a wide range of physical phenomena was able to be observed and analysed. This included assessment of the total amount of ammonia adsorbed, the amount of chemisorbed ammonia to physisorbed ammonia and if the ammoniated material was stable after the ammoniation process. Phase transformations involving coordination geometry were observed, as well as suppression of hole conduction processes due to ammoniation.
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Seligman, Jeffrey M. "Spectral Characterization of Dielectric Materials Using Terahertz Measurement Systems." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/566237.
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The performance of modern high frequency components and electronic systems are often limited by the properties of the materials from which they are made. Over the past decade, there has been an increased emphasis on the development of new, high performance dielectrics for use in high frequency systems. The development of these materials requires novel broadband characterization, instrumentation, and extraction techniques, from which models can be formulated. For this project several types of dielectric sheets were characterized at terahertz (THz) frequencies using quasi-optical (free-space) techniques. These measurement systems included a Fourier Transform Spectrometer (FTS, scalar), a Time Domain Spectrometer (TDS, vector), a Scalar Network Analyzer (SNA), and a THz Vector Network Analyzer (VNA). Using these instruments the THz spectral characteristics of dielectric samples were obtained. Polarization based anisotropy was observed in many of the materials measured using vector systems. The TDS was the most informative and flexible instrument for dielectric characterization at THz frequencies. To our knowledge, this is the first such comprehensive study to be performed. Anisotropy effects within materials that do not come into play at microwave frequencies (e.g. ~10 GHz) were found, in many cases, to increase measured losses at THz frequencies by up to an order of magnitude. The frequency dependent properties obtained during the course of this study included loss tangent, permittivity (index of refraction), and dielectric constant. The results were largely consistent between all the different systems and correlated closely to manufacturer specifications over a wide frequency range (325 GHz-1.5 THz). Anisotropic behavior was observed for some of the materials. Non-destructive evaluation and testing (NDE/NDT) techniques were used throughout. A precision test fixture was developed to accomplish these measurements. Time delay, insertion loss, and S-parameters were measured directly, from which loss tangent, index of refraction, and permittivity was extracted. The test materials were low-loss dielectric slabs ranging in thickness from 1-60 mils. The substrate sheets were PTFE, fiberglass, and epoxy-ceramic composite substrates. The other group was polyethylene plastic sheets (LDPE/HDPE/UMHW) and 3D printer Photopolymers. The results were verified by using several online THz spectral databases and compared to manufacturer data sheets. Permittivity and loss of some of the test samples varied as a function of polarization angle. 0 - 90 degrees of rotation were tested (i.e., H-V, and 45 degrees polarization). Inter-molecular scattering in the composite materials raised the loss considerably. This effect was verified. Standard, well documented, material types were selected for the project for best comparison. These techniques can also be applied to analyze newer substances such as nanodielectrics.
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Feng, Shan. "Dielectric materials for triboelectric and piezo/triboelectric hybrid generators." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLC098.
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Les crises énergétiques et environnementales nous obligent à chercher les sources d’énergies renouvelables, qui contribuent à la fois à réduire l’effet de serre et la consommation des sources traditionnelles d’énergie fossile. Récemment, un nouveau système, le nano-générateur triboélectrique (TENG), se convertit l’énergie mécanique en énergie électrique en combinant l’effet de la triboélectronique et de l’induction électrostatique. TENG montre comme un outil alternatif et prometteur pour la récupération des énergie s renouvelables. Pour réaliser des matériaux plus performants, la plupart des recherches s’appuie sur le choix des différents types des céramiques ou charges conductrices, de taux de charge et de nouvelle structure, l’effet de l’interface entre charge, ainsi que la taille des charges, matrice a été très peu étudié. Donc, l’objectif de cette thèse consiste à étudier les effets de taille des charges, de l’interface entre charge-matrice et de la polarisation sur les performances électriques du TENG et les nano-générateurs du type piézo/tribohybride (P-TENG). Tout d’abord, un TENG fonctionnant sous la mode de contact-séparation avec la motion de l’accélération/décélération a été utilisé dans notre expérimentation et les équations progressives du type du second ordre polynomial ont été choisi pour l’ajustement des courbes. Différents paramètres cinétiques comme distance entre deux électrodes, fréquence de déplacement, pression de contact et temp du repos du TENG basés sur les conditions expérimentales ont été étudiés dans le chapitre 2 afin de comprendre leur contributions sur les performances des sorties électriques. Deuxièmement, deux différentes tailles (BT-70, BT-500) des nanoparticules de BaTiO3 sont considérées et utilisées pour préparer des composites di électriques BaTiO3/PDMS et BaTiO3-MWCNT/PDMS dans le chapitre 3. Les propriétés di électriques de tous ces composites ont été caractérisées et le déplacement électrique entre les particules et le polymère a été analysé théoriquement. En plus, l’effet synergique de MWCNT, de nitrure de bore (BN) et de noir de carbone (CB) avec BaTiO3 dans BaTiO3-70-MWCNT (CB, BN) / PDMS ont été comparés. Tous ces films composites fabriqués précédemment sont ensuite utilisés dans l’assemblage des dispositifs TENG dans le chapitre 4. Les performances électriques ont été mesurées pour étudier l’influence de l’interface charge-matrice et l’effet synergique des particules MWCNT (CB, BN) pour les dispositifs TENG. Les résultats de la différence potentielle surfacique induite par les effets synergiques des BaTiO3/MWCNT ont été confirmé avec les simulations COMSOL Multiphysics. En outre, dans le chapitre 5 les films composites contenant des particules de BaTiO3 sont polarisés pour étudier les effets piézoélectriques et triboélectriques couplés pour P-TENG. Les effets des différents paramètres de polarisation, tels que la direction de polarisation, la température, le ratio massique du BaTiO3, le champ électrique et la taille des BaTiO3 sur les performances de P-TENG ont été discutées. Enfin, les conclusions générales sont présentées et certains ou quelques perspectives sont proposées pour le futurThe increasing energy crisis and environmental pollution stimulate the development of renewable energies, which contribute to reducing the greenhouse effect and the consumption of traditional fossil fuels. As a new type of renewable energy harvesting system, triboelectric nanogenerator (TENG) converts mechanical energy to electrical energy by coupling the effect of triboelectrification and electrostatic induction. TENG has been proved to be an alternative and promising approach to harvest renewable energy in recent years. For the dielectric material candidates, more attention has been paid to choosing different types of ceramic or conductive fillers, filler loading and surface structure design, rather than considering the filler-matrix interface effect. Thus, it is desired to clarify the effect of filler size and fillermatrix interface on the performance of compositebased TENGs. This work aims to research the influence of filler size, filler-matrix interface, and polarization on the output performance of TENG and piezo/tribo-hybrid nanogenerator (P-TENG). Firstly, the contact-separation mode TENG with acceleration/deceleration motion is utilized in our experiments. The piecewise second-order polynomial fitting is chosen for the motion process curve fitting. Various kinematic parameters including gap distance, motion frequency, contact pressure, and pause time of TENG are studied theoretically based on the experiment conditions in chapter 2, to understand their contributions to the electrical output performance. Secondly, in chapter 3, BaTiO3 nanoparticles with two different sizes (BT-70, BT-500) are considered and utilized to prepare BaTiO3/PDMS and BaTiO3-MWCNT/PDMS dielectric composites. The dielectric properties of all composites are characterized, and the electric displacement between particle and polymer are theoretically analyzed. Moreover, the synergistic effect of MWCNT, boron nitride (BN) and carbon black (CB) with BaTiO3 in BaTiO3-70-MWCNT(CB, BN)/PDMS are compared. Then, all composite films fabricated were further utilized to assemble TENG devices in chapter 4. The output voltage, current, and charges densities of TENGs are evaluated to investigate the influence of fillermatrix interface and synergistic effect of MWCNT (CB, BN) particles on the output performance of TENG devices. COMSOL Multiphysics simulation are performed to further confirm the surface potential difference introduced by the synergistic effects of BaTiO3/MWCNTs. Furthermore, the composite films with BaTiO3 particles are polarized to further explore the interaction of piezoelectric and triboelectric effects for P-TENG in chapter 5. Influences of different polarization parameters, such as polarization direction, poling temperature, BaTiO3 mass ratio, poling electric field and BaTiO3 sizes, on the output performance of the PTENG have been discussed. Finally, general conclusions are presented and perspectives are proposed for the future work
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Lu, Jiongxin. "High dielectric constant polymer nanocomposites for embedded capacitor applications." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26666.
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Thesis (Ph.D)--Materials Science and Engineering, Georgia Institute of Technology, 2009.Committee Chair: Wong, C. P.; Committee Member: Jacob, Karl; Committee Member: Liu, M. L.; Committee Member: Tannenbaum, Rina; Committee Member: Wang, Z. L.. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Rybka, Marcin. "Optical properties of MAX-phase materials." Thesis, Linköping University, Applied Optics, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-60008.
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MAX-phase materials are a new type of material class. These materials are potentiallyt echnologically important as they show unique physical properties due to the combination of metals and ceramics. In this project, spectroscopic ellipsometry in the spectral range of 0.06 eV –6.0 eV was used to probe the linear optical response of MAX-phases in terms of the complexd dielectric function ε(ω) = ε1(ω) + iε2(ω). Measured data were fit to theoretical models using the Lorentz and generalized oscillator models. Data from seven different samples of MAX-phase materials were obtained using two ellipsometers. Each sample dielectric function was determined, including their infrared spectrum.
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Giatti, Brandon. "Optical Properties of Nanostructured Dielectric Coatings." PDXScholar, 2014. https://pdxscholar.library.pdx.edu/open_access_etds/1940.
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Solar cells have extrinsic losses from a variety of sources which can be minimized by optimization of the design and fabrication processes. Reflection from the front surface is one such loss mechanism and has been managed in the past with the usage of planar antireflection coatings. While effective, these coatings are each limited to a single wavelength of light and do not account for varying incident angles of the incoming light source. Three-dimensional nanostructures have shown the ability to inhibit reflection for differing wavelengths and angles of incidence. Nanocones were modeled and show a broadband, multi-angled reflectance decrease due to an effective grading of the index.
Finite element models were created to simulate incident light on a zinc oxide nanocone textured silicon substrate. Zinc oxide is advantageous for its ease of production, benign nature, and refractive index matching to the air source region and silicon substrate. Reflectance plots were computed as functions of incident angle and wavelength of light and compared with planar and quintic refractive index profile models. The quintic profile model exhibits nearly optimum reflection minimization and is thus used as a benchmark. Physical quantities, including height, width, density, and orientation were varied in order to minimize the reflectance. A quasi-random nanocone unit cell was modeled to better mimic laboratory results. The model was comprised of 10 nanocones with differing structure and simulated a larger substrate by usage of periodic boundary conditions. The simulated reflectance shows approximately a 50 percent decrease when compared with a planar model. When a seed layer is added, simulating a layer of non-textured zinc oxide, on which the nanocones are grown, the reflectance shows a fourfold decrease when compared with planar models. At angles of incidence higher than 75 degrees, the nanocone model outperformed the quintic model.
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Hsu, Shuo-Lin. "Hafnium Oxide Films for Application as Gate Dielectric." Diss., The University of Arizona, 2005. http://hdl.handle.net/10150/196101.
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The deposition and characterization of HfO2 films for potential application as a high-k gate dielectric in MOS devices has been investigated. DC magnetron reactive sputtering was utilized to prepare the HfO2 films. Structural, chemical, and electrical analyses were performed to characterize the various physical, chemical and electrical properties of the sputtered HfO2 films. The sputtered HfO2 films were annealed to simulate the dopant activation process used in semiconductor processing, and to study the thermal stability of the high-k films. The changes in the film properties due to the annealing are also discussed in this work.Glancing angle XRD was used to analyse the atomic scale structure of the films. The as deposit films are amorphous, regardless of the film thickness. During postdeposition annealing, the thicker films crystallized at lower temperature 600 C, and ultra-Thin (5.8 nm) film crystallized at higher temperature (600 - 720 C). The crystalline phase which formed depended on the thickness of the films. The low temperature phase (monoclinic) formed in the $10-20$ nm annealed films, and high temperature phase (tetragonal) formed in the ultra--thin annealed HfO2 film. The TEM cross-section studies of as deposited samples show the interfacial layer (< 1nm) exists between HfO2/Si for all film thicknesses. The interfacial layer grows thicker during heat treatment, and grows more rapidly when grain boundaries are present. XPS surface analysis shows the as deposited films are fully oxidized with an excess of oxygen. Interfacial chemistry analysis indicated that the interfacial layer is a silicon-rich silicate layer, which tends to transform to silica-like layer during heat treatment.I-V measurements show the leakage current density of the Al/as deposit-HfO2/Si MOS diode is of the order of 10^{-3} A/cm^2, which is two orders of magnitude lower than that of ZrO2 film with similar physical thickness. Carrier transport is dominated by Schottky emission at lower electric fields, and by Frenkel-Poole emission in the higher electric field region. After annealing, the leakage current density decreases significantly as the structure remains amorphous structure. It is suggested that this decrease is assorted with the densification and defect healing which accures when the porous as-deposited amorphous structure is annealed. The leakage current density increases of the HfO2 layer crystallizes on annealing, which is attributed to the presence of grain boundaries. C-V measurements of the as deposited film shows typical C-V characteristics, with negligible hystersis, a small flat band voltage shift, but great frequency dispersion. The relative permittivity of HfO2/interfacial layer stack obtained from the capacitance at accumulation is 15, which corresponds to EOT (equivalent oxide thickness)= 1.66 nm. After annealing, the frequency dispersion is greatly enhanced, and the C-V curve is shifted toward negative voltage. Reliability tests show that the HfO2* 0films which remain amorphous after annealing possess superior resistance to constant voltage stress and ambient aging.This study concluded that the sputtered HfO2 films are amorphous as deposited. The postdeposition annealing alters the crystallinity, interfacial properties, and electrical characteristics. The HfO2 films which remain amorphous structure after annealing possess the best electrical properties.
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Golt, Michael C. "Magnetic and dielectric properties of magneto-dielectric materials consisting of oriented, iron flake filler within a thermoplastic host." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 150 p, 2008. http://proquest.umi.com/pqdweb?did=1597633721&sid=13&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Tripathi, Pragya. "Dielectric spectroscopy studies of low-disorder and low-dimensional materials." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/404420.
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In this thesis we employ dielectric spectroscopy (in different implementations) to study the dielectric properties of different materials ranging from completely disordered supercooled liquids to low-disorder solids with only ratcheting reorientational motions, to low-dimensional systems such as thin films or needle-like crystals. The probed material properties include the electrical conductivity, the space-charge processes due to sample heterogeneities, molecular dynamics, hydrogen-bond dynamics, and phase-transition temperature and kinetics. To study materials in thin film form, we implement silicon-based interdigital electrode devices, which we calibrate to obtain their equivalent capacity in vacuum. We also probe two-dimensional samples obtained by intercalating (sandwiching) organic molecules between parallel graphite oxide sheets.
We study both organic and hybrid (organic-inorganic) films, and compared the results with the bulk counterpart of the same materials. Rhodamine films are deposited by two different procedures starting from rhodamine 6G chloride: solution-deposited films are ionic and ordered, while vacuum-deposited films consist of a different, neutral species, namely rhodamine19, due to decomposition of rhodamine 6G upon sublimation. Both types of films display variable-range hopping electronic conduction, and a conductivity-induced space-charge relaxation. Solution deposited films display a dipolar relaxation, absent in rhodamine 19 films. We assign the dipolar relaxation to some intramolecular motion involving the charged nitrogen of the Rhodamine and the chlorine counter-ion. We also performed studies on hybrid films of cadmium iodide covalently attached to ethylamine (CdI2EA), deposited by the Langmuir-Blodgett process. Bulk CdI2EA material has a solid-to-solid (structural) phase transition, which in the Langmuir-Blodgett films occurs 5 degrees higher in temperature. The films displayed a dielectric relaxation dynamics absent in the bulk, and which is either due to the existence of molecular motions in the looser structure of the film, or to the motion of teh surfactant covalently attached to CdI2EA for Langmuir-Blodgett film deposition.
Another example of low-dimensional material is biclotymol, whose supercooled liquid form crystallizes into a metastable solid phase which consists of one-dimensional needle-like crystallites. The crystallization kinetics of bicotymol is a textbook example of the Avrami law with exponent n = 2 resulting from a temperature independent nucleation rate of the crystallites followed by unidimensional growth. The instability of the supercooled liquid phase may be related to the existence of fast secondary relaxation dynamics.
The last two chapters of the thesis focus on ethane derivatives with distinct side groups, namely tetrachloroethane and ethanolamine. The solid phase of tetrachloroethane displays three distinct relaxation processes. We carry out molecular dynamic simulations to identify the three processes: the slowest is a cooperative reorientational dynamics whereby the molecules rotate by passing through an intermediate equivalent state; such collective relaxation is accompanied by a ¿precursor¿ single-molecule relaxation. The third process is a non-cooperative ratcheting motion between the equilibrium orientation and a high-energy orientation.
In ethanolamine we observe the existence of a metastable solid phase besides the known stable one. A very prominent relaxation process is observed in both solid phases and in the liquid. The ubiquity of this relaxation indicates that it is related to local fluctuations of the hydrogen-bond network between the molecules. The same relaxation is also present when ethanolamine is sandwiched between graphite oxide sheets, but it is slower and characterized by a broader distribution of relaxation times due to the interaction with the graphite oxide matrix.En esta tesis utilizamos la espectroscopia dieléctrica para estudiar las propiedades dieléctricas de diferentes materiales que van desde líquidos subenfriados completamente desordenados a sólidos de bajo desorden con movimiento de reorientación, hasta sistemas de baja dimensionalidad tales como películas delgadas o cristales casi unidimensionales. Las propiedades estudiadas incluyen la conductividad eléctrica, los procesos de carga espacial debido a las heterogeneidades de la muestra, la dinámica molecular, la dinámica de enlaces por puente de hidrógeno, y la cinética de cristalización. Para el estudio de materiales en forma de película delgada, se han implementado nuevos dispositivos de electrodo interdigital a base de silicio. Muestras bidimensionales han sido obtenidas también por intercalación de moléculas orgánicas entre planos atómicos de óxido de grafito. Estudiamos películas orgánicas e híbridas orgánicas-inorgánicas depositadas mediante procedimientos diferentes, y comparamos los resultados con las fases puras de los mismos materiales. Obtenemos películas ordenadas de rodamina 6G clorada por crecimiento desde solución, y películas amorfas de rodamina 19 por condensación de vapor en vacío. Ambos tipos de películas presentan una conducción electrónica por salto de electrones y una relajación de carga espacial. Las películas de rodamina 6G clorada muestran además una relajación dipolar, que se asigna a movimientos intramoleculares que involucran la carga asociada al nitrógeno de la rodamina 6G y al átomo de cloro. También se han estudiado películas híbridas de ioduro de cadmio covalentemente unido a etilamina (CdI2EA), depositadas mediante el método Langmuir-Blodgett. El material en fase “bulk” presenta una transición estructural, que en la película delgada aparece a una temperatura superior de unos 5 K. Las películas presentan una relajación dinámica ausente en el material puro y que es debida a la existencia de movimientos moleculares en la estructura de la película (menos densa), o bien al movimiento del surfactante que ha sido enlazado químicamente al CdI2EA para lograr la deposición. Otro ejemplo distinto de material de baja dimensionalidad es el biclotymol, para el que el líquido subenfriado cristaliza en una fase sólida que consiste en cristales unidimensionales (en forma de aguja). La cinética de cristalización del bicotymol es un ejemplo perfecto de la ley de Avrami con exponente n = 2, resultante de una tasa de nucleación independiente de la temperatura, seguida por un crecimiento unidimensional. La inestabilidad de la fase líquida subenfriada puede estar relacionada con la existencia de dinámicas moleculares rápidas. Los dos últimos capítulos de la tesis se centran en dos derivados del etano con grupos laterales distintos, a saber, tetracloroetano y etanolamina. La fase sólida del tetracloroetano muestra tres procesos de relajación distintos. Mediante simulaciones moleculares se han podido identificar los tres procesos: el más lento es un proceso cooperativo en el que las moléculas “giran” sobre si mismas pasando por un estado equivalente intermedio; esta relajación colectiva se acompaña de una relajación "precursora", correspondiente al movimiento de una sola molécula. El tercer proceso es una rotación, no cooperativa, entre la orientación de equilibrio y una orientación de alta energía.
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Chen, Minghan. "Optical studies of high temperature superconductors and electronic dielectric materials." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0012986.
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Xu, Ziguang. "Synthesis and characterization of magnetically ordered dielectric and ferroelectric materials." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0008/MQ61520.pdf.
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Xiao, Li. "An investigation of dielectric tunable materials for microwave tunable devices." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/12754/.
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Today, many of the communication systems are operated in several different bandwidths. Till now, the common solution to get a multi bandwidth transmitter/receiver is to insert several fixed microwave devices with different bandwidth to the required standard. This increases the size and power consumption of trans/receiver. One solution is to develop electronically tunable microwave devices. By replacing several fixed microwave devices with a single electronically tunable device, the size and power consumptions of the transmitter/receiver can be significantly reduced. The tunable devices are usually implemented by high permittivity tunable materials that exhibit a change of dielectric constant with respect to a DC electric field. In this work, two different types of tunable materials: ferroelectric Barium Strontium Titanate (BST) Oxide and pyrochloe Bismuth Zinc Niobate Oxide (BZN) thin films are investigated. A simple and cost effective chemical solution deposition (CSD) method has been used to prepare the thin films. In addition, two different types of microwave devices (coplanar waveguide and metal insulated metal capacitors) were fabricated to measure the microwave dielectric properties of BST and BZN thin films. The maximum errors in the measured dielectric constants are 24% due to the calibration errors. To improve the dielectric properties of BST thin films, acceptor ions such as lithium (Li) and cobalt (Co) were doped into BST thin films. According to the measured results, the Li doped BST thin film exhibits an increase of dielectric constant and a decrease of dielectric loss, which makes it highly attractive for implementing microwave device. In contrast, the BZN thin films exhibit little dielectric tunability (3.0%) even when a large DC electric field (500kV/cm) is applied. These results demonstrate that ferroelectric BST thin films are still the only practical materials for implementing tunable microwave devices due to its high tunability.
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Nam, Taesung. "A study of dielectric thin film materials for display applications." Thesis, Nottingham Trent University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442092.
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Akhtaruzzaman, Md. "Dielectric studies of some oxide materials, nitride ceramics and glasses." Thesis, Durham University, 1989. http://etheses.dur.ac.uk/6308/.
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This thesis is primarily concerned with the evaluation and comparison of the dielectric behaviour of materials which may find application as substrates in microelectronic high-performance packaging. In the introductory chapter the factors governing the choice of the most suitable dielectric substrate for compatibility with silicon technology are reviewed; it is shown that in addition to good dielectric properties the thermal conductivity is important if high power packages are required together with the ability to obtain good matching of thermal expansion coefficients. This is followed by a survey of the present theories of dielectric behaviour with special emphasis on the Universal law of dielectric response and its applicability to oxide and glass ceramics which exhibit hopping conductivity. The experimental methods for the measurement of dielectric parameters are outlined in Chapter 3 which includes an account of techniques developed for studying materials only available as powders. The three substrate systems studied were aluminium oxide, aluminium nitride and glass-on-molybdenum and in the case of the two former materials a range of both pure and impure specimens were examined both in single crystal and sintered polycrystalline form. The detailed experimental results are presented and discussed in the three succeeding chapters for each of the materials in turn; these results include the values of permittivity and dielectric loss, measured over a frequency range of 5 x 10(^2) Hz to 1 x 10(^7) Hz, the temperature variation of permittivity both in the low temperature (85K to 293k) and high temperature (20ºC to about 600ºC) regions and the d.c. and a.c. conductivity in the high temperature range. In their pure form each of these materials would be suitable as a substrate, having permittivities at room temperature of ϵ ' (_s) = 10.2 for polycrystalline Al(_2)(^0)(_3), ϵ' (_s) = 9.2 for polycrystalline AlN (which has a thermal conductivity of about one-hundred times that of alumina) and ϵ' (_s) - 6.5 for glass-on-molybdenum and dielectric losses in the region of tan δ - 10(^-3). The effect of impurities is shown to be very significant leading in all cases to some increase in permittivity and a much larger increase in dielectric loss. The measurements made on powders are given and discussed in Chapter 7. In the studies on the powders used as starting materials for the manufacture of substrates it was shown that by making measurements at low temperature (77K) the effects of intergranular space charge polarization could be overcome yielding information valuable for quality control of impurity content; measurements made on powders of some high temperature oxide superconducting materials are also given. The final chapter, Chapter 8, summarises the overall conclusions of the research and makes some suggestions for future work.
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"An efficient volume integral equation approach for characterization of lossy dielectric materials." 2004. http://library.cuhk.edu.hk/record=b6073666.
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Lui Man Leung."May 2004."
Thesis (Ph.D.)--Chinese University of Hong Kong, 2004.
Includes bibliographical references.
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Mode of access: World Wide Web.
Abstracts in English and Chinese.
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Cheng, Huei-Ju, and 鄭惠如. "Porosity material applied in supercapacitors and low dielectric materials." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/77587972480794449726.
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碩士中原大學
化學研究所
104
There were two parts in this thsis. One part described that Xanthosoma Sagittifolium leaves carbonized into porous materials, and then this materials were reprocessed by activation to produce the electrode material in supercapacitor. First of all, scanning electron microscope （SEM） and transmission electron microscopy （TEM） displayed that activated leaves were more holes than carbonized leaves, and surface area and pore analyzer （BET） demonstrated the specific surface area of activated leaves were 3 times higher than carbonized leaves. In the capacitor tests, the capacitance values of activated leaves was 131.11 F/g at 1M H2SO4 in 5 mV/s scan rate, which was more raise than carbonized leaf nearly 200%. In the charge-discharge test that activated leaves maintained good capacitance values, and it was also confirmed relatively small impedance in 1M H2SO4. The others part was that hollow polyimide sphere incorporated into polyimide and applied on the low dielectric and high insulating materials. First of all, synthesis of amino-modified silica （AMS） particles was prepared by using sol-gel method. Then, as-prepared was identified by using fourier transform infrared spectroscopy （FT-IR）, and solid state nuclear magnetic resonance spectrometer （13CNMR, 29SiNMR）. AMS was incorporated into polyimide polymerization to form the PI shell on the AMS surface. Moreover, using etching method hollow polyimide sphere were obtained, and identification of the material form was used of SEM and thermo-gravimetric analysis （TGA）. Next hollow polyimide spheres were added into polyimide, SEM can be observed from the high content of HPS uniformly dispersed in the substrate, and Ultraviolet-Visible spectrophotometer （UV-Visible） created more HPS content that the transmittance will reduce. Part of the thermal stability, it identified that adding HPS did not affect, compared with pure PI. In the thermal properties, it can be learned from TGA and DSC that added HPS in the film and did not affect materials decomposed temperature and glass transition temperature. In the thermal conductivity, it found that the lowest value was the 10 wt% HPS composite film which the thermal conductivity coefficient was 0.09874 W / mK. Finally, the dielectric constant of 3.25 on 15wt% HPS composite film by the lowest impact on the dielectric constant of the polymer itself.
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Yang, Fung-Kei, and 楊逢祺. "Development of X8R Dielectric Materials." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/fa86zr.
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碩士國立臺北科技大學
材料科學與工程研究所
98
In recent years, with the rapid technological development and application of increased demand, Multi-layer ceramic capacitors (MLCC) are toward smaller, multi-functional and trend of high capacitance, and must often operated under harsh environmental conditions, so its performance and life have to met a certain standards, such as automotive electronic components, including the CAS (Crank angle sensor), ABS (antilock brake system), ECU (engine electronic control unit). So based on these security considerations, high temperature capacitor, X8R meet the Electronics Industry Association (EIA) standard in the high temperature capacitor standard (-55 to 150℃, ΔC/C≦±15%) of dielectric material due to a high degree of attention and development, and as production technology continues to progress to make capacitors in a limited volume with maximum performance. According to the literature that the Curie temperature of BaTiO3 Ceramics is about 130℃, its dielectric constant will significantly increase in not for dielectric materials use. Therefore, this study makes use of adding the Bi0.5Na0.5TiO3(BNT) compounds in BaTiO3 to increase the Curie temperature above 150℃, further by adding different proportions of ZrO2, Mn3O4 to inhibit dielectric peak to achieve planarization dielectric curve, and improve ceramics capacitance change rate. The result shows that the Curie point can effectively shift to high temperature by adding BNT, and the rate of change of TCC can improve by ZrO2 addition, and the Curie point will shift to low temperature and dramatically decrease the dielectric constant by excessive doping.
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Vedula, Ramakrishna. "Low dielectric constant materials and processes for interlayer dielectric applications." 2006. https://scholarworks.umass.edu/dissertations/AAI3206194.
Full textAbstract:
At 0.18 microns and below minimum device dimensions in Ultra Large Scale Integrated Circuits, signal net parasitic delay amounts to 80% of the overall path delay. This leads to serious problems relating to signal timing, crosstalk, noise and power consumption. Although Copper is being used as an alternative to Aluminum interconnects to reduce the resistive component of the RC delays, finding a suitable material to replace Silicon Dioxide (SiO2) as the interlayer dielectric poses serious challenges. Most of the inorganic candidates are variants of SiO2, while the most prominent among polymeric materials belong to the polyparaxylylene family. The primary disadvantage of polyparaxylylene materials is their low thermal stability. While SiO2 based inorganic films exhibit excellent thermal stability, they offer only incremental improvement in the dielectric constant. The thin film deposition technique for these materials is important as it directly impacts the cost of manufacturing. Chemical Vapor Deposition is known to make high purity, conformal thin films, and is compatible with current silicon manufacturing technology. This research is primarily focused to develop materials which have (i) Low dielectric Constant; (ii) High thermal stability, and to deposit them using Chemical Vapor Deposition technique. The vision was to develop a composite thin film material with the thermal stability of SiO2 and the low dielectric constant of paraxylylenes. The first objective of this research was to develop a technique to deposit SiO2 films at near room temperatures. Thin conformal films of SiO2 were deposited at temperatures around 50°C using Di-acetoxy-di-tertiary-butoxy silane (DADBS) as the precursor. The thermal stability, optical and electrical properties of the codeposited thin films were systematically studied. It was possible to control the composition of these films smoothly and these films were shown to be of nanocomposite type. However, the thermal stability of these nanocomposite thin films was only marginally better than that of paraxylylenes. These films were then heat treated under oxygen to 'burn off' the polymer content. It was shown that annealing these films in oxygen environment leaves porous SiO 2 which exhibits the thermal stability of SiO2 and the porosity results in lower dielectric constant.
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"Mechanisms of Microwave Loss Tangent in High Performance Dielectric Materials." Doctoral diss., 2013. http://hdl.handle.net/2286/R.I.16430.
Full textAbstract:
abstract: The mechanism of loss in high performance microwave dielectrics with complex perovskite structure, including Ba(Zn1/3Ta2/3)O3, Ba(Cd1/3Ta2/3)O3, ZrTiO4-ZnNb2O6, Ba(Zn1/3Nb2/3)O3, and BaTi4O9-BaZn2Ti4O11, has been investigated. We studied materials synthesized in our own lab and from commercial vendors. Then the measured loss tangent was correlated to the optical, structural, and electrical properties of the material. To accurately and quantitatively determine the microwave loss and Electron Paramagnetic Resonance (EPR) spectra as a function of temperature and magnetic field, we developed parallel plate resonator (PPR) and dielectric resonator (DR) techniques. Our studies found a marked increase in the loss at low temperatures is found in materials containing transition metal with unpaired d-electrons as a result of resonant spin excitations in isolated atoms (light doping) or exchange coupled clusters (moderate to high doping) ; a mechanism that differs from the usual suspects. The loss tangent can be drastically reduced by applying static magnetic fields. Our measurements also show that this mechanism significantly contributes to room temperature loss, but does not dominate. In order to study the electronic structure of these materials, we grew single crystal thin film dielectrics for spectroscopic studies, including angular resolved photoemission spectroscopy (ARPES) experiment. We have synthesized stoichiometric Ba(Cd1/3Ta2/3)O3 [BCT] (100) dielectric thin films on MgO (100) substrates using Pulsed Laser Deposition. Over 99% of the BCT film was found to be epitaxial when grown with an elevated substrate temperature of 635 C, an enhanced oxygen pressures of 53 Pa and a Cd-enriched BCT target with a 1 mol BCT: 1.5 mol CdO composition. Analysis of ultra violet optical absorption results indicate that BCT has a bandgap of 4.9 eV.Dissertation/Thesis
Ph.D. Materials Science and Engineering 2013
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Tu, Hsien Ming, and 杜賢明. "Study of Advanced Low Dielectric Constant Materials for ULSI Intermetal Dielectric Applications." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/50335301534663409081.
Full textAbstract:
碩士國立交通大學
電子工程系
87
For ULSI circuits when feature size is scaled into the deep submicron region, The speed of the devices will be significantly limited by the interconnect delay. Low dielectric constant (K) materials will play a major role, with copper as the interconnect material, in offering to minimize the interconnect RC delay. A variety of inorganic or organic polymers, xerogel are being considered for low k applications. This thesis will describe two new siloxanes and porous xerogel with ultra-low dielectric constant for low k applications. We will explore thermal stability, moisture uptake, stress variations, leakage current and electrical dielectric breakdown strength of three types of low-k materials. In this work, the application of low-k to copper metallization is also investigated. Without MoN barrier, the Cu/T23(cured at 350C)/Si MOS capacitors are very leak after 3500C anneal and the thermal stability of Cu/T24(cured at 500C)/Si MOS capacitors is found to reach 400C. For the Cu/MoN/ T24(cured at 500C)/Si MOS capacitors, the stability temperature is up to 500C.
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Wei, Jang-ting, and 魏彰廷. "Dielectric Properties of TiO2-Bi1.5ZnNb1.5O7 Microwave Materials." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/21073450051298073366.
Full textAbstract:
碩士義守大學
電子工程學系碩士班
97
This study aims to achieve microwave dielectric materials TiO2-Bi1.5ZnNb1.5O7 (T-BZN) with high permittivity (εr) and low temperature coefficient of resonant frequency (τf) which is suitable for mobile communication. Sintering aids 0.29BaCO3–0.71CuO (BC)、0.81MoO3–0.19CuO (MC)、V2O5 are added to the TiO2-Bi1.5ZnNb1.5O7 composites for decreasing the sintering temperature. In addition, crystal phase, sintering behavior and microstructures of the sintered specimens are also discussed T-BZN doped with 5wt% BC, 3wt% MC, 3wt% V2O5 has value of density 5.5g/cm3, 6.1g/cm3, 6.35g/cm3 after sintered at 1000oC, 1000oC, 850oC for 4 hours, respectively. It is found that V2O5 is effective to decrease sintering temperature compared to BC and MC. For the 30mole% TiO2–70mol% Bi1.5ZnNb1.5O7 doped with 2wt% V2O5 composites sintered at 850oC, density is 6.35 g/cm3, εr =118，τf =15ppm/ oC and Q x f =992 measured at 3GHz