A dispersão e absorção das ondas eletromagnéticas que se propagam através de um material dielétrico podem ser medidas ao longo de uma ampla região do espectro que se estende desde a região de freqüências extremamente baixas até a região óptica incluindo as faixas das microondas, objeto de interesse do presente estudo. Dentre os dielétricos, incluem-se os materiais cristalinos e amorfos isolantes e semicondutores. Os vidros de composições (1-x)(60\'P IND. 2\'\'O IND.5\'.\'40\'BA\'\'O).x(\'M\'\'O\'), (1-X)(25\'LI IND. 2\'\'O\'.25\'NA IND. 2\'\'O\'.50\'P IND. 2\'\'O IND. 5\').x(\'M\'\'O\') e 60\'B IND. 2\'\'O IND. 3\'.30\'BA\'\'O\'.\'10\'AL IND. 2\'\'O IND. 3\' onde x é a concentração (mol%) de óxido do metal de transição \'FE\' ou \'CO\' (\'M\'\'O\'), foram escolhidos para representar o comportamento das propriedades dielétricas dos vidros óxidos, tanto na região das freqüências mais baixas (0 - 100 MHz), como na faixa de microondas (2 - 30 GHz). Os íons de metais de transição, quando ocupam posições intersticiais da rede vítrea, como ocorre com os elementos modificadores alcalinos e alcalinoterrosos atuam como compensadores de carga junto às unidades estruturais tetraédricas eletricamente carregadas, formando dipolos permanentes locais, contribuindo para a constante dielétrica do vidro. A polarização desses dipolos, quando submetido ao campo elétrico oscilatório de uma onda eletromagnética, atinge valores maiores às freqüências mais baixas decrescendo gradualmente à medida que estas atingem a região de microondas. Um novo método alternativo foi desenvolvido para a medida da temperatura da transição vítrea (\'T IND. g\') utilizando técnicas de microondas. Mostramos que a posição da inflexão do gráfico da constante dielétrica em função da temperatura do vidro 25\'LI IND. 2\'\'O\'.25\'NA IND. 2\'\'O\'.50\'P IND. 2\'\'O IND. 5\' medida em 9 GHz, na faixa de temperaturas em torno de \'(270 \'+ OU -\' 10) GRAUS\' C coincidiu com o valor da \'T IND. g\' deste vidro obtida por análise térmica diferencial (DTA). Outro método também foi desenvolvido para monitorar o resfriamento do vidro em função do tempo a partir do estado liquido até a solidificação, registrando o sinal de microondas refletido sobre o material vertido no interior de um guia de ondas. Pudemos observar, também, mudanças no espectro de ressonância paramagnética eletrônica (EPR) do vidro fosfato contendo níquel após ter sido irradiado com diferentes níveis de potência das microondas, por cerca de duas horas. Este efeito pode estar relacionado com mecanismos de acoplamento de spins paramagnéticos. Os espectros de transmissão de microondas das amostras de vidros fosfatos contendo diferentes concentrações de cobalto, bário, ferro e manganês, obtidos por meio de uma varredura de freqüências desde 7 até 13 GHz, mostraram a presença de uma intensa atenuação do sinal próximo de 9,7 GHz. Essa atenuação diminuiu conforme aumenta a concentração dos modificadores. / The dispersion and absorption of electromagnetic waves that propagate through a dielectric material can be measured along a wide spectral region ranging from extremely low frequency to the optical region, including microwaves one, which is the subject of interest of the present study. Among dielectrics, there are crystalline and amorphous materials that can be either insulators or semiconductors. Glasses of compositions (1-x)(60\'P IND. 2\'\'O IND.5\'.\'40\'BA\'\'O).x(\'M\'\'O\'), (1-X)(25\'LI IND. 2\'\'O\'.25\'NA IND. 2\'\'O\'.50\'P IND. 2\'\'O IND. 5\').x(\'M\'\'O\') and 60\'B IND. 2\'\'O IND. 3\'.30\'BA\'\'O\'.\'10\'AL IND. 2\'\'O IND. 3\', where x is the concentration (mol %) of the \'FE\' or \'CO\' (\'M\'\'O\') transition metal oxide, were selected to investigate the behavior of the dielectric properties of oxide glasses in the lower frequency range (0 - 100 MHz) and in the microwave region (2- 30 GHz). When transition metal ions occupy interstitial positions in the glass matrix, as it happens with the regular alkaline and alkaline-earth modifier ions, they compensate the electrically charged tetrahedral structural units. As a consequence, local permanent dipoles are formed, contributing to the dielectric constant of the glass. The polarization of these dipoles, when submitted to an oscillating electromagnetic field, is higher at lower frequencies and decreases gradual1y as the frequency approaches the microwave region. An alternative new method was developed to measure the glass transition temperature (\'T IND. g\') using microwave techniques. It was shown that the inflexion position of the dielectric constant of the glass 25\'LI IND. 2\'\'O\'.25\'NA IND. 2\'\'O\'.50\'P IND. 2\'\'O IND. 5\' measured at 9 GHz, in the temperature range about \'(270 \'+ OU -\' 10) GRAUS\' C, coincided with the \'T IND. g\' value obtained by differential thermal analysis (DTA). Another method was also developed for monitoring the melt cooling as a function of time from the liquid to the solid state, by recording the reflected microwave signal crossing the material poured inside the wave guide. We observed, also, changes in the electronic paramagnetic resonance (EPR) spectrum of phosphate glass containing nickel after being irradiated for two hours with several microwave power levels. This effect may be related with coupling and decoupling mechanisms among the spin clusters developed in the sample. The microwave transmission spectra of the phosphate glass samples containing different concentrations of iron, cobalt, barium, manganese and barium, obtained by a frequency sweep from 7 to 13 GHz, presented an intense attenuation of the signal near to 9,7 GHz. This attenuation was found to decrease with the increase of modifier content.

It is essential to properly monitor in-situ soil compaction properties during most earthwork construction projects. Traditional in-situ soil compaction monitoring methods are often limited in their application. As a result, new methods are being developed to more accurately measure in-situ compaction parameters. Time domain reflectometry (TDR) is one such method. Relying on the propagation of an electromagnetic wave through the soil sample, TDR can be used to measure both in-situ moisture content as well as soil dry density. Although TDR is relatively new to the field of geotechnical engineering, it has previously been implemented in other fields with success. Researchers at Purdue University have made several advances to further incorporate the use of TDR technology into the field of geotechnical engineering and as a result an innovative TDR measurement system has been developed for compaction control monitoring. The method was standardized in the form of ASTM D 6780 in 2002. Further advancements led to an improved method referred to as the Purdue one-step TDR method. Research has indicated that the ASTM TDR method is sufficiently accurate for application in compaction monitoring applications. A comparison between the ASTM TDR method and traditional methods was carried out to evaluate the accuracy of the TDR method to traditional methods. To further expand the application of the TDR method, a correlation was developed between the TDR spike driving process with the in-situ CBR test. A comprehensive review of previous research was conducted to examine recent advancements leading to the improved Purdue one-step method. A study was also performed to evaluate the effect of variable pore fluid conductivity on the calibration of the Purdue one-step method.

The flexible substrate was fabricated by BaTi4O9 mixed with O-Cresol Novolac Epoxy, polyether imide or surface active agents. The electrical and physical characteristic measured had been finished. The dielectric property influence of substrate was changed from percentage of BaTi4O9. The dielectric constant model was used by Jayasundere and Smith equation (J. S. eq.) and Lichtenecker equation (L. eq.) The study of crystalline grain, orientation and phase transfer temperature was used by SEM, XRD, and DSC, respectively. The dielectric constant and dielectric loss tangent of the composite was measured using an HP4294A impedance analyzer. The TM mode calculated by resonate frequency of the composite was measured using an HP4156C network analyzer. The dielectric constant was obtained to TM mode at high frequency. The result was showed that dielectric constant at low frequency of BaTi4O9, OCN Epoxy and PEI are 57, 5.8 and 3.65, respectively. OCN Epoxy is better than PEI of electrical characteristic. However, OCN Epoxy is not flexible. For this reason, the PEI was focused on electrical property at high frequency. The BaTi4O9 exhibited a dielectric constant of 39 at frequency during 3~10 GHz. The dielectric constant was measured of 10 at frequency during 2~16 GHz with 70 wt% PEI composite. The dielectric constant is higher than FR-4 substrate to 6.4 of the composite. The low dielectric constant is obtaining to reduce stuffing.

The objective of this thesis is to develop high dielectric constant nanoparticle dispersion for switchable aircraft antenna systems. Two steps were designed to achieve the objective. First, obtain high dielectric, high aspect ratio nanoparticles and disperse them in dielectric oil medium. Second, manipulate the particle-oil dispersion using an external alternating current (AC) electric field to increase the effective dielectric constant. In order to obtain high dielectric dispersions, different sizes and shapes of titanium dioxide (TiO2) and barium titanate (BaTiO3) nanoparticles were purchased and measured. However, after a number of experiments detailed in the thesis, it was found that none of the commercially available nanoparticles could satisfy our requirements for a minimum effective dielectric constant. Thus, to achieve the goals above, we synthesized high aspect ratio BaTiO3 nanowires with BaC2O4 and TiO2 powders as precursors using a molten salt method. The as-synthesized BaTiO3 nanowires were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS) mapping. The nanowires have a diameter ranging from 100 nm to 300 nm, and their lengths range from 1.5 micrometers to 5 micrometers. Mechanical stirring and bath sonication were used to obtain even colloidal dispersions. Different concentrations of BaTiO3 nanoparticles well dispersed in the oil medium were successfully manipulated using AC electric field. To monitor the change in microstructure of BaTiO3 nanoparticles, optical microscopy was used to observe the alignment of particles in the sample under the applied electric field. Various parameters including the magnitude, frequency, and duration of the electric field, and the concentration of BaTiO3 nanoparticles were investigated to achieve the optimal alignment of nanoparticles. The experimental results were validated by theoretical analysis using Maxwell-Garnett mixing rule. It was demonstrated that the effective dielectric constant of the colloidal dispersions would increase with the increase of the magnitude, frequency and duration of applied electric field. Synthesized BaTiO3 nanowire-based dispersions exhibit significant enhancement of the effective dielectric constant compared to other colloidal materials. The effective dielectric constant of 5 wt percent BaTiO3-oil dispersions could reach up to 10 when aligned at 1000 V/mm electric field at 1 kHz frequency for 1 hour.

HfO2 is a popular replacement for SiO2 in modern CMOS technology. It is used as the gate dielectric layer isolating the transistor channel from the gate. For this application, certain material property demands need to be met, most importantly, a high static dielectric constant is desirable as this positively influences the effectiveness and reliability of the device. Previous theoretical calculations have found that this property varies with the crystal structure of HfO2; specifically, the tetragonal structure possesses the highest dielectric constant (~70 from theoretical calculations) out of all possible stable structures at atmospheric pressure, with the cubic phase a far second (~29, also calculated). Following the results from previous experimental work on the phase formation of sputtered HfO2, this study investigates the possibility of producing thin films of HfO2 with the cubic or tetragonal structure by the addition of nitrogen to a reactive sputtering process at various deposition temperatures. Also, a new physical vapor deposition method known as High Power Impulse Magnetron Sputtering (HiPIMS) is employed for its reported deposition stability in the transition zone of metal-oxide compounds and increased deposition rate. Structural characterization of the produced films shows that films deposited at room temperature with a low N content (~6 at%) are mainly composed of amorphous HfO2 with mixed crystallization into t-HfO2 and c-HfO2, while pure HfO2 is found to be composed of amorphous HfO2 with signs of crystallization into m-HfO2. At 400o C deposition temperature, the crystalline quality is enhanced and the structure of N incorporated HfO2 is found to be c-HfO2 only, due to further ordering of atoms in the crystal lattice. Optical and dielectric characterization revealed films with low N incorporation (< 6 at%) to be insulating while these became conductive for higher N contents. For the insulating films, a trend of increasing static dielectric constant with increasing N incorporation is found.

In this study, the characteristics of Nickel-doped LPD-TiO2 films on silicon substrate were investigated. In our experiment, we do some measurement about physical, chemical and electrical properties for undoped and Nickel-doped LPD-TiO2 films and discussed with them. The TiO2 film thickness was characterized by field emission scanning electron microscopy ( FE-SEM ), structure was characterized by X-ray diffraction (XRD), chemical properties was characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and electrical properties was characterized by leakage current: current-voltage (B1500A) and dielectric constant: capacitance-voltage (4980A). For the electrical property improvements, we investigated the Ni-doped LPD-TiO2 films by the post-anneal treatments in nitrogen, oxygen and nitrous oxide ambient. For nickel doping, the nickel chloride was used as the doping solution and the electrical characteristics were improved. After thermal annealing in nitrous oxide at 700 oC, the dielectric constant of polycrystalline titanium oxide film is 29 and can be improved to 94 with nickel doping.

An uniform titanium oxide film was grown on indium tin oxide/glass substrate with the aqueous solutions of ammonium hexafluoro-titanate and boric acid. The as-deposition titanium oxide film shows good electrochromic property because of fluorine passivation on defects and dangling bonds. The transmittance of as-grown titanium oxide on indium tin oxide/glass with a thickness of 270 nm is about 85% at the wavelength of 550 nm. By 50 times electrochromic cycling test, the transparency ratio of TiO2 film is kept at 45% between fully colored state and fully bleached state at the wavelength of 550 nm. Under ultraviolet illumination, the growth of titanium oxide film grown is enhanced. The root mean squared value of surface roughness is improved from 3.723 to 0.523 nm. Higher fluorine concentration from (NH4)2TiF6 passivate defects and dangling bonds of titanium oxide during the growth. After 50 times electrochromic cycling test, the transparency ratio UV-TiO2 is improved from 37.5% to 42.4% at the wavelength of 550 nm. The electrical characteristics of nickel-doped titanium oxide films on p-type (100) silicon substrate by liquid phase deposition were investigated. For nickel doping, the nickel chloride was used as the doping solution and the electrical characteristics were improved. After thermal annealing in nitrous oxide at 700 oC, the dielectric constant of polycrystalline titanium oxide film is 29 and can be improved to 94 with nickel doping. Uniform nickel oxide film was grown on a conducting glass substrate with the aqueous solution of saturated NiF2¡E4H2O solution and H3BO3. The quality of NiO is improved after thermal annealing at 300 oC in air from the decrease of oxygen vacancy and better F ion passivation on defects and dangling bonds. The transmittance of as-deposited NiO/ITO/glass with a thickness of 100 nm is about 78% and improved to 88% after annealing at the wavelength of 550 nm. By the electrochromic cycling test 50 times on annealed NiO film, the transparency ratio is kept at 48% between fully colored state and fully bleached state at the wavelength of 550 nm. By the memory time test, the annealed LPD-NiO film has shorter memory time. The growth of nickel oxide film grown on indium-tin oxide/glass substrate by liquid phase deposition is enhanced under ultraviolet photo-irradiation was studied. a-Ni(OH)2 dominates the composition of as-grown NiO film. After thermal treatment at 300 oC,a-Ni(OH)2 is transformed into NiO. For thermally treated NiO under ultraviolet photo-irradiation, the recrystallization and the colored and bleached transmittance after 50 times electrochromic test were improved. Both improvements come from fluorine passivation. Transparent and conductive thin films consisting of p-type nickel oxide (NiO) semiconductors were prepared by liquid phase deposition. A resistivity of 8 x 10-1 -cm was obtained for NiO films prepared at liquid phase deposition. The transmittance of NiO is almost 70 % in the 550 nm wavelength was obtained for a 384.3 nm thick NiO film.

This thesis contains four parts. In the first part, we investigate the post treatment of low-temperature-deposited high dielectric constant (high-k) thin films to enhance their properties. The high-pressure oxygen (O2 and O2+UV light) is employed to improve the properties of low-temperature-deposited metal oxide dielectric films and interfacial layer. In this study, 13nm HfO2 thin films are deposited by sputtering method at room temperature. Then, the oxygen treatments with a high-pressure of 1500 psi at 150 ¢J are performed to replace the conventional high temperature annealing. According to the XPS analyses, integration area of the absorption peaks of O-Hf and O-Hf-Si bonding energies apparently raise and the quantity of oxygen in deposited thin films also increases from XPS measurement. In addition, the leakage current density of standard HfO2 film after O2 and O2+UV light treatments can be improved from 3.12¡Ñ10-6 A/cm2 to 6.27¡Ñ10-7 and 1.3¡Ñ10-8 A/cm2 at |Vg| = 3 V. The leakage current density is significantly suppressed and the current transport mechanism is transformed from trap-assisted tunneling to Schottky-Richardson emission due to the passivation of traps inside HfO2 film and interfacial layer. The proposed treatment is applicable for the future flexible electronics. In the second part of this thesis, we study the memory characteristics of CoSi2 nanocrystals with SiO2 or Al2O3/HfO2 multiple layer tunnel oxide. Due to the property of high-k, it can provide thicker physics thickness than thermal oxide (SiO2) under identical equivalent oxide thickness (EOT) and enhances the reliability without reducing the programming speed. By engineering the different dielectric constant materials and the energy band structure, the performance of nonvolatile memory can be improved. The device that employs HfO2/Al2O3/HfO2 as tunnel oxide exhibits better memory window and carrier injection efficiency than the device employing thermal oxide. Furthermore, the device employs Al2O3/HfO2/Al2O3 as tunnel oxide present the better retention characteristics than the device employs HfO2/Al2O3/HfO2 as tunnel oxide. The corresponding mechanisms were also discussed. For the advanced nonvolatile application, high-k material - hafnium oxide was applied on the resistance switching nonvolatile memory device as resistive switching layer with TiN/Ti/HfO2/TiN structure in the third part of this thesis. By using a thin Ti layer as the reactive buffer layer into the anode side, the proposed device exhibits superior bistable characteristics. Since the Ti can easily absorb oxygen atoms from buried HfO2, the TiN/Ti bi-layer can greatly improve the resistive switching characteristics. The mechanism of the proposed device is dominated by the redox reaction between the Hf and HfOX. In addition, the proposed device has multi-bit storage ability to enhance the storage density. From the temperature-dependent measurements, the low ambient temperatures would cause the formation and rupture of the conduction path with discordant quality and quantity during every switching cycle, which give rise to a wide distribution of the HRS and LRS resistance and instability of resistive switching properties. In the fourth part of this thesis, we investigate the characteristics of an advanced Cu-induced resistance switching non-volatile memory with Pt/Cu/SiON/TiN/SiO2/Si structure. By inserting a Cu ultra thin film between the SiON layer and Pt top electrode, the device exhibits bipolar resistive switching characteristics after a forming process at 13.6 V. However, the forming and resistive switching process can not be observed in the device if the Cu thin film is omitted. Additionally, we employ a two-step forming process to reduce the forming voltage to 7.5 V. During the forming process, the bias-induced Cu could form a filament-like stretched electrode, but the ¡§set¡¨ and ¡§forming¡¨ voltage of the proposed device take place on different polarity. Therefore, we suppose a bipolar switching mechanism, and our device is dominated by the formation and rupture of the oxygen vacancies in a conduction path between the Cu filament and TiN button electrode. The device also demonstrates stable resistance states during 105 cycling bias pulse operations and acceptable retention characteristics after an endurance test at 85¢J. The I-V switching curves are analyzed to realize the carrier transport mechanisms in different bias regions and resistance states. Additionally, the effective thickness of the resistance switching layers (deff) for the samples with different SiON thickness is also extracted from the related mechanism and demonstrated that the deff is independent with the initial SiON thickness. The corresponding mechanisms and the deff verify the bipolar switching is dominated by the formation and rupture of the oxygen vacancies in conduction path between Cu filament and TiN bottom electrode.

Research in nanoparticle-reinforced composites is predicated by the promise for exceptional properties. However, to date the performance of nanocomposites has not reached its potential due to processing challenges such as inadequate dispersion and patterning of nanoparticles, and poor bonding and weak interfaces. The main objective of this dissertation is to improve the physical properties of polymer nanocomposites at low nanoparticle loading. The first step towards improving the physical properties is to achieve a good homogenous dispersion of carbon nanofibers (CNFs) and single wall carbon nanotubes (SWNTs) in the polymer matrix; the second step is to manipulate the well-dispersed CNFs and SWNTs in polymers by using an AC electric field. Different techniques are explored to achieve homogenous dispersion of CNFs and SWNTs in three polymer matrices (epoxy, polyimide and acrylate) without detrimentally affecting the nanoparticle morphology. The three main factors that influence CNF and SWNT dispersion are: use of solvent, sonication time, and type of mixing. Once a dispersion procedure is optimized for each polymer system, the study moves to the next step. Low concentrations of well dispersed CNFs and SWNTs are successfully manipulated by means of an AC electric field in acrylate and epoxy polymer solutions. To monitor the change in microstructure, alignment is observed under an optical microscope, which identifies a two-step process: rotation of CNFs and SWNTs in the direction of electric field and chaining of CNFs and SWNTs. In the final step, the aligned microstructure is preserved by curing the polymer medium, either thermally (epoxy) or chemically (acrylate). The conductivity and dielectric constant in the parallel and perpendicular direction increased with increase in alignment frequency. The values in the parallel direction are greater than the values in the perpendicular direction and anisotropy in conductivity increased with increase in AC electric field frequency. There is an 11 orders magnitude increase in electrical conductivity of 0.1 wt% CNF-epoxy nanocomposite that is aligned at 100 V/mm and 1 kHz frequency for 90 minutes. Electric field magnitude, frequency and time are tuned to improve and achieve desired physical properties at very low nanoparticle loadings.

Most engineering as well as pavement materials are composites composed of two or more components to obtain a variety of solid properties to support internal and external loading. The composite materials rely on physical or chemical properties and volume fraction of each component. While the properties can be identified easily, the volume fraction is hard to be estimated due to the volumetric variation during the performance in the field. Various test procedures have been developed to measure the volume fractions; however, they depend on subjective determination and judgment. As an alternative, electromagnetic technique using dielectric constant was developed to estimate the volume fraction. Empirical and mechanistic approaches were used to relate the dielectric constant and volume fraction. While the empirical models are not very accurate in all cases, the mechanistic models require assumptions of constituent dielectric constants. For those reasons, the existing approaches might produce less accurate estimate of volume fraction. In this study, a mechanistic-based approach using the self consistent scheme was developed to be applied to multiphase materials. The new approach was based on calibrated dielectric constant of components to improve results without any assumptions. Also, the system identification was used iteratively to solve for dielectric parameters and volume fraction at each step. As the validation performed to verify the viability of the new approach using soil mixture and portland cement concrete, it was found that the approach has produced a significant improvement in the accuracy of the estimated volume fraction.