SILVA, Roger Ribeiro. Estudo das propriedades dielétricas do Niobato de Bismuto e Titânio dopado com PbO e Bi2O3 para aplicações em antenas. 2009. 93 f. Dissertação (Mestrado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2009. / Submitted by Edvander Pires (edvanderpires@gmail.com) on 2015-06-16T21:40:35Z No. of bitstreams: 1 2009_dis_rrsilva.pdf: 3731493 bytes, checksum: ea1e0ca9dd5b082cce643034649ad572 (MD5) / Approved for entry into archive by Edvander Pires(edvanderpires@gmail.com) on 2015-06-18T18:22:11Z (GMT) No. of bitstreams: 1 2009_dis_rrsilva.pdf: 3731493 bytes, checksum: ea1e0ca9dd5b082cce643034649ad572 (MD5) / Made available in DSpace on 2015-06-18T18:22:11Z (GMT). No. of bitstreams: 1 2009_dis_rrsilva.pdf: 3731493 bytes, checksum: ea1e0ca9dd5b082cce643034649ad572 (MD5) Previous issue date: 2009 / Dielectric resonators based on type structure compound Bi3TiNbO9 show singular characteristics for microwave applications, including high dielectric constants, low dissipation losses and low temperature coefficients. Single phase of the Bi3TiNbO9 powder was obtained by x-ray diffraction technique. The ceramics doped during manufacture, with lead oxide and bismuth oxide, were synthesized by solid state reaction at 950°C for two hours. Samples were analysed by Archimedes method and exhibited good levels of density for doped ceramics with bismuth and lead oxide. Grain morphology and stoichiometry of ceramics were investigated by scanning electron microscopy and energy dispersive spectroscopy technique. Far infrared spectroscopy identified large bands on the Bi3TiNbO9 structure by attenuated total reflection technique. Radiofrequency measurements showed that doped ceramics exhibited higher dielectric constants than pure phase. Microwave measurements were investigated by Hakki-Coleman and resonant cylindrical cavity. The ceramics called as BTNO3BiP, BTNO5BiP, BTNO10BiP, BTNO3PbG e BTNO5PbG, showed high dielectric constants and high quality factors demonstrating that they can be applied in dielectric antennas on microwave range. / Ressoadores dielétricos baseados na estrutura do composto Bi3TiNbO9 apresentam características singulares para aplicações em microondas, incluindo altas constantes dielétricas, baixos fatores de dissipação e baixos coeficientes de temperatura. Obteve-se a fase pura da amostra em pó de Bi3TiNbO9 pela técnica de difração de raios X. As amostras cerâmicas dopadas durante a fabricação, com óxido de chumbo e óxido de bismuto, foram sintetizadas pelo método de reação do estado sólido a 950°C por 2 horas. As amostras foram analisadas pelo método de Arquimedes e apresentaram bons níveis de densidade nas dopagens com os óxidos de bismuto e chumbo. A morfologia dos grãos e a estequiometria das amostras cerâmicas foram investigadas pelas técnicas de microscopia eletrônica de varredura e análise por energia dispersiva de raios X. A espectroscopia no infravermelho distante identificou bandas largas na estrutura do Bi3TiNbO9 pela técnica de reflexão total atenuada. As medidas de constante dielétrica e perda dielétrica em radiofreqüência demonstraram que as dopagens com chumbo e bismuto exibiram maiores constantes dielétricas em relação à cerâmica pura. As medidas em microondas foram estudadas pelos métodos Hakki-Coleman e a cavidade ressonante metálica. As cerâmicas denominadas como BTNO3BiP, BTNO5BiP, BTNO10BiP, BTNO3PbG e BTNO5PbG, apresentaram altas constantes dielétricas e altos fatores de qualidade, demonstrando que podem ser aplicadas em antenas dielétricas na faixa de micro-ondas.

abstract: Estimation of complex permittivity of arsenic-doped silicon is the primary topic of discussion in this thesis presentation. The frequency that is of interest is 2.45 GHz, frequency typically used in conventional microwave ovens. The analysis is based on closed-form analytical expressions of cylindrical symmetry. A coaxial/radial line junction with the central conductor sheathed in dielectric material, which is As-doped silicon in this case, are analyzed. Electrical and magnetic field equations governing the wave propagation in this setup are formulated by applying the necessary boundary conditions. Input admittance is computed using the fields in the device and reflection coefficient is calculated at the input. This analytical solution is matched to the reflection coefficient acquired by experiments conducted, using VNA as the input source. The contemplation is backed by simulation using High Frequency Structural Simulator, HFSS. Susceptor-assisted microwave heating has been shown to be a faster and easier method of annealing arsenic-doped silicon samples. In that study, it was noticed that the microwave power absorbed by the sample can directly be linked to the heat power required for the annealing process. It probes the validity of the statement that for arsenic-doped silicon the heating curve depends only on its sheet properties and not on the bulk as such and the results presented here gives more insight to it as to why this assumption is true. The results obtained here can be accepted as accurate since it is known that this material is highly conductive and electromagnetic waves do not penetrate in to the material beyond a certain depth, which is given by the skin depth of the material. Hall measurements and four-point-probe measurements are performed on the material in support of the above contemplation. / Dissertation/Thesis / M.S. Electrical Engineering 2014

Nesse trabalho foram fabricados filmes finos de TiO2 por RF magnetron sputtering reativo sobre substrato de silício (1 0 0). A pressão parcial do oxigênio na câmara foi variada de 5 a 100% em relação ao argônio. Após a deposição os filmes foram submetidos a tratamento térmico em atmosfera de oxigênio. A estequiometria dos filmes e o perfil de profundidade foram obtidos por RBS. A estrutura cristalina foi obtida por XRD. As propriedades ópticas foram obtidas por interferometria e reflectância e as elétricas por meio das curvas C-V. Os valores de espessura dos filmes sem tratamento térmico aumentaram aproximadamente 41% com o aumento do oxigênio na câmara de deposição. Essa variação está ligada ao aumento da eficiência do sputtering do alvo. Os índices de refração dos filmes sem tratamento térmico se mantiveram dentro de um intervalo de aproximadamente 2,3 a 2,4. A diminuição do band gap com o tratamento térmico é consequência da mudança de fase cristalográfica de anatase para rutila. A estequiometria TiOx dos filmes antes do tratamento térmico apresentaram valores de x entre 2,0 e 2,4. A espessura em TFU dos filmes aumentou com o percentual de oxigênio na câmara. As amostras que receberam tratamento térmico apresentaram difusão de titânio na interface do substrato e incorporação de oxigênio no filme. Os valores da constante dielétrica aumentaram com o percentual de oxigênio na câmara, em contraposição com o efeito do tratamento térmico que diminuiu o valor. Todos os resultados observados são coerentes do ponto de vista da mudança de fase anatase rutila e aumento do percentual de oxigênio na câmara. / In this work thin films of TiO2 were produced by reactive RF magnetron sputtering on silicon substrate (1 0 0). The oxygen partial pressure in the chamber was varied from 5 to 100% in relation to argon. After deposition the films were submitted to thermal treatment under an oxygen atmosphere. The stoichiometry of the films and the depth profile were obtained by RBS. The crystal structure was obtained by XRD. Its optical properties were obtained by interferometry and reflectance and the electrical were obtained by means of the C-V curves. The thickness values of films without heat treatment increased approximately 41% with the increase of oxygen in the deposition chamber. This variation is linked to the increased sputtering efficiency of the target. The refractive indexes of films without heat treatment remained within a range of about 2.3 to 2.4. The decrease of the band gap with the heat treatment is a consequence of the change of crystallographic phase from anatase to rutile. The TiOx stoichiometry of the films before the heat treatment showed values of x between 2.0 and 2.4. The TFU thickness of the films increased with the percentage of oxygen in the chamber. The samples that received heat treatment shows diffusion of titanium at the interface of the substrate and incorporation of oxygen in the film. The values of the dielectric constant increased with the percentage of oxygen in the chamber, as opposed to the effect of the thermal treatment that decreased the value. All the results observed are consistent from the point of view of the anatase - rutile phase transition and the increase in the oxygen percentage in the chamber.

No description available.

Les besoins de la microélectronique pour les condensateurs de type DRAM sont résumés dans la feuille de route ITRS (International Technology Roadmap for Semiconductors). Pour descendre en dessous du noeud technologique 22 nm, des performances électriques telles qu'une épaisseur d'oxyde équivalent (EOT) < 0.5 nm et un niveau de courant de fuite < 1.10-7 A/cm² à 0.8 V sont nécessaires. Ces performances sont difficiles à atteindre si l'on considère des oxydes standards largement utilisés tels que le SiO2, le Si3N4 ou l'Al2O3. Le dioxyde de Titane constitue un matériau diélectrique de choix pour ce type d'application si l'on considère sa forte constante diélectrique, la plus haute des oxydes binaires. Selon les conditions de croissance de la couche de TiO2, celle-ci peut se présenter sous forme amorphe ou posséder une structure cristalline appelé phase anatase ou phase rutile. Cette dernière présente une très forte constante diélectrique (90 à 170 selon l'orientation de la maille cristalline) et en fait un atout indéniable pour le développement de condensateur DRAM. Toutefois, cette phase rutile est aussi à l'origine d'un fort courant de fuite mesuré à partir des structures Métal - Isolant - Métal (MIM) associées. De ce fait, il est primordial de savoir contrôler ces courants de fuite tout en gardant la forte valeur de constante diélectrique de la phase rutile. Dans ce travail, nous proposons de travailler sur la croissance des couches minces de TiO2 intégrées dans des structures MIM et déposées sur des substrats différents tels que des électrodes de RuO2/Ru ou de Pt. La technique de dépôt employée pour les couches minces de TiO2 est la technique ALD pour son contrôle très précis de l'épaisseur déposée et sa souplesse d'utilisation pour ce type d'applications. Les propriétés physico-chimiques des couches de TiO2 et l'influence du substrat sur ces propriétés sont analysées. Des compositions différentes de diélectriques sont élaborées au moyen de la technique de dépôt par ALD et notamment des couches minces de TiO2 dopés à l'aluminium. Les propriétés électriques de ces couches sont étudiées afin de déterminer les performances électriques des structures MIM associées en termes de courant de fuite et de densité capacitive. / The requirements for future dynamic random access memory (DRAM) capacitors are summarized in the International Technology Roadmap for Semiconductors. For sub-22 nm node, performances like equivalent oxide thickness (EOT) < 0.5 nm and leakage current density < 1.10-7 A/cm² at 0.8 V are required but are difficult to meet. Titanium dioxide (TiO2) is an attractive dielectric material for such application regarding its high dielectric constant (k). Depending on its growth conditions, TiO2 can be prepared in amorphous, anatase or rutile phase. From the structural point of view, it is generally preferred that TiO2 remains amorphous throughout a complete technological process to minimize leakage transport along grain boundaries. However, the rutile phase exhibits very high dielectric constant ranging from 90 to 170, depending on the lattice orientation. Due to this high dielectric constant, TiO2 rutile phase is considered as a promising material for capacitors in future generations of Dynamic Random Access Memories (DRAMs). A key issue is how to control the high leakage current of rutile phase while keeping the highest dielectric constant in order to get the best electrical performances. In this work, we investigate the growth of high dielectric constant rutile TiO2 films in Metal - Insulator - Metal (MIM) structures deposited on different substrates such as RuO2/Ru or Pt electrodes using ALD (Atomic Layer Deposition). A study of physico-chemical properties of TiO2 layer and influence of bottom electrodes on TiO2's crystalline structure is proposed. Different compositions of dielectrics are processed using flexibility of ALD deposition technique, including Al-doped TiO2 layers and pure TiO2 layers. Electrical properties in terms of leakage current or capacitance density of MIM structures embedding that kind of dielectrics and comparison between these MIM structures in terms of electrical performances is proposed in order to determine the best dielectric film composition to meet the requirements for next generation of DRAM capacitors.

The first part of this dissertation deals with the application of a luminescence quenching method to measure diffusion and permeation coefficients of oxygen in polymers. Most luminescence oxygen sensors do not follow linearity of the Stern-Volmer (SV) equation due to heterogeneity of luminophore in the polymer matrix, thus the complexity of data analysis is increased. To circumvent this limitation, inverted fluorescence microscopy is utilized in this work to investigate the SV response of the sensors at the micron-scale. In these diffusion experiments, oxygen concentration is measured by luminescence changes in regions with high SV constants and good linearity. Thus, we avoid numerical complexity of combining nonlinear SV equation with a diffusion model. This technique allows us to measure oxygen diffusion properties in different type of polymers like transparent, opaque, free-standing polymers and polymers that cannot be cast into free standing films and polymer composites. In the second part of this thesis, we have explored the effect of Ag-Cu alloy nanoparticles on the emission intensity of luminophores at their close proximity. Alloy nanoparticles offer additional degrees of freedom for tuning their optical properties by altering atomic composition and atomic arrangement and thus can be an attractive option for manipulating signal of a wide range of luminophores. In this work, surface plasmon resonance spectrum of Ag-Cu alloy nanoparticles deposited by sputtering was easily tuned in wide wavelength range by varying one experimental condition- annealing temperature. Large metal enhanced luminescence for different luminophores viz Alexa Fluor 594 and Alexa Fluor 488 were achieved at the vicinity of Ag-Cu nanoparticles when maximum spectral overlap between SPR spectra of Ag-Cu nanoparticles and the emission and absorption spectra of the luminophores occur. We also studied the effect of composition of Ag-Cu nanoparticles synthesized by the polyol process on the luminescence of low quantum yield dye Cy3. In the third part of this thesis, quenching effect of Cu nanoparticles on CdSe/ZnS nanocrystal quantum dots has been explored. As Cu nanoparticles have comparable dielectric properties with gold nanoparticles, they are expected to show similar quenching effects. It was found that Cu is an efficient quencher of fluorescence from CdSe/ZnS quantum dots and the quenching effect is due to resonance energy transfer from quantum dots to Cu nanoparticles.

No description available.

<p>The phenomenon of image blurring on laser-printed or electro-photocopied paper has been discovered since the 1980s. In the 1990s, the problem was confirmed to be associated with the undesired surface conduction along the unique photoconductive polymer surface during the photoconduction process. Other than this, little progress has been made in investigating this phenomenon, due to the limited experimental techniques.</p> <p>In this thesis, the electrical properties of a commercially available photoconductor as a result of Corona charging were studied. Various techniques including vacuum deposition and step-function impedance spectroscopy were employed, to overcome the nature of the photoconductor that prevented the use of conventional techniques such as AC impedance spectroscopy. Negative dielectric constant (NDC) has been prevalently discovered at a broad range of frequencies (below 1Hz and up to 1 MHz) and it was questioned in the form of a physically-impossible inductor. This precipitous sign switch of dielectric constant is found in various areas ranging from physics, chemistry, biology to electronics. The magnitude of the NDC decreased drastically with the decrease of electric field frequency. The system obeyed the proposed free-carrier plasma model with a resonance frequency at MHz level.</p> <p>Commercially available polymeric photoconducting materials showing NDC at extremely low frequency are expected to provide unusual scattering to electromagnetic waves and therefore demonstrate profound implications with reduced cost. It has paved the way for many applications such as inductors in integrated chips without bulky coils and provides an insight into a possible revolution in electronics and photonics.</p> / Doctor of Philosophy (PhD)

Improvements in the treatment of breast cancer have resulted in better survival rates and less breast cancer related morbidity. Nevertheless, a significant group of patients still experience a diminished quality of life as a result of lymphedema. In the early, often reversible, stage of lymphedema patients can experience subjective changes in the affected area. However, with the traditionally available tools the lymphedema often remains clinically undetectable and patients are denied essential care that can prevent worsening. Furthermore, most lymphedema assessment tools fail to support a clear unambiguous definition of lymphedema. This underlines the need for a sensitive objective measurement method that can assess lymphedema in a subclinical stage. In this study we demonstrated that measuring tissue dielectric constant (TDC) using the MoistureMeter-D is an effective method to detect tissue water changes and could potentially provide a cost-effective adequate tool to measure the early onset of breast cancer related lymphedema (BCRL). Secondarily, we established the correlation between the novel TDC method and the frequently used arm volume measurements and self-assessment questionnaires. A group of 20 female patients with clinically BCRL were included. TDC measurements in both arms and all quadrant of both breast were recorded along with volumetric measurements of both arms. All patients were asked to complete a self-report questionnaire. The novel TDC method detected significantly higher tissue water levels in the affected arm and breast compared to the control side. The TDC ratio between control and affected side showed significant correlation with self-reported pain and discomfort in both arm and breast. In the arm, the TDC method also showed correlation with the volume measurement method. The TDC value of the arm was correlated to age, but not to BMI. This study demonstrates that measuring TDC using the MMD is an effective method for quantifying lymphedema in arm and breast and is an important tool in detecting early TWC changes.

Orientador: Valdeci Pereira Mariano de Souza / Resumo: Neste trabalho de Mestrado foram explorados aspectos fundamentais da Fı́sica do Estado Sólido através de três frentes de pesquisa. A primeira e principal frente de pesquisa é referente ao estudo da chamada fase ferroelétrica de Mott-Hubbard nos condutores moleculares orgânicos quase-unidimensionais da famı́lia (TMTTF)2X, onde TMTTF é a molécula tetrametiltetratiafulvaleno e X é um contra-ânion monovalente. Tal investigação foi realizada através de experimentos de constante dielétrica e o denominado Positive Up Negative Down (PUND) a qual permite obter informações acerca da polarização elétrica intrı́nseca de um sistema ferroelétrico. Os resultados mostram a anisotropia para a constante dielétrica e a presença de polarização intrı́nseca abaixo de Tco . Uma segunda frente é relacionada às oscilações de cargas em sólidos onde foi investigado o quão suscetı́vel tais oscilações são à variações de volume. Esta análise foi realizada através do cálculo do parâmetro de Grüneisen fonônico para a frequência de plasma. Os cálculos realizados mostram que as oscilações de carga são fortemente influenciadas por variações de volume e, consequentemente de pressão. A última frente de estudo é relacionada ao solo da Amazônia conhecido como Terra Preta de Índio para o qual foram realizadas medidas de ressonância paramagnética eletrônica. Esta permitiu obter informações acerca de propriedades conectadas ao spin eletrônico do sistema. As medidas mostram um possı́vel ordenamento ferromagnético na T... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this Master thesis, fundamental aspects of Solid State Physics were explored through three research topics. The first and main research topic is the investigation of the so-called Mott-Hubbard ferroelectric phase in quasi-one-dimensional organic molecular conductors of the (TMTTF)2X family, where TMTTF is the tetramethyltetrathiafulvalene molecule and X is a monovalent counter-anion. This investigation was carried out through dielectric constant and the so-called Positive Up Negative Down (PUND) experiments, which enable to obtain physical information about the intrinsic electric polarization of a ferroelectric system. Our results reveled the anisotropy of the the dielectric constant and the presence of intrinsic electric polarization below Tco . The second topic is related to the charge oscillations in solids, the so-called plasma frequency, where it was investigated how susceptible such frequency is to volume variations. This analysis was performed by calculating the phononic Grüneisen parameter for the plasma frequency. The calculations reveled that the charge oscillations are strongly influenced by changes in volume and, consequently, of pressure. The last research topic is related to the Amazonian soil known as Terra Preta de Índio, for which electron spin resonance measurements were performed. This allowed to obtain information about properties connected to the electronic spin of the system. The measurements reveled a possible ferromagnetic ordering in TPI, which may... (Complete abstract click electronic access below) / Mestre