Este trabalho apresenta a pesquisa e desenvolvimento de algoritmos de pré-processamento digital de imagens para câmeras térmicas não refrigeradas na faixa espectral do infravermelho distante. O estudo de câmeras infravermelhas é uma questão estratégica, uma vez que tem aplicações militares, civis e científicas. Este trabalho define a concepção e implementação de algoritmos de pré-processamento de imagem necessários para obter imagens com baixo ruído e alto contraste, tais como: correção de não-uniformidade, substituição de pixels defeituosos, geração de histograma, aumento de contraste e processamento de saída do pixel, com taxa de 30 quadros por segundo, utilizando detector não-resfriado com matriz de plano focal de 320 x 240 pixels. Neste trabalho todos os algoritmos foram implementados em software para se obter resultados rapidamente e, assim, facilitar a validação dos códigos. Foram gerados resultados de caracterização eletro-óptica do sistema montado com indicação das principais figuras de mérito que norteiam o estudo desta tecnologia, tais como: componentes de ruído tridimensionais, potência equivalente de ruído, responsividade e relação sinal-ruído. Os resultados indicam que os algoritmos de pré-processamento de imagem propostos aumentam a qualidade da imagem a ser exibida, e os resultados das figuras de mérito calculadas sobre o vídeo digital mostram que todas as métricas apresentaram resultados satisfatórios. / This work aims to present the research and development of digital image processing algorithms for uncooled LWIR thermal camera in Brazil. The study of an infrared thermal camera is a strategic issue since that has more and more applications in military, judicature, rescue, industry, hospital and science areas. This work describes the design and implementation of all image-processing algorithms required to obtain high-performance images with low noise and high contrast, such as: functions for non-uniformity correction of sensor deficiencies, dead-pixel replacement algorithms, histogram generation, contrast enhancement methods and output pixel processing with frame rate of 30 frames per second based on 320 x 240 Uncooled Focal Plane Array (UFPA). In this work all algorithms was implemented in software to get results quickly and to facilitate the validation of computer codes. There are some results of electro-optical characterization on the assembled system, indicating the main figures of merit that guide the study of this technology, such as: 3D noise components, noise equivalent power (NEP), signal transfer function (SiTF) and noise equivalent temperature difference (NETD). The results indicate that the proposed imageprocessing algorithms increase the quality of the corrected image, and the test results through the digital video of the infrared camera show that all metrics are in accordance with its nominal value.

Dans des conditions de croissance spécifiques, des sections nanofilaires d’AlGaN peuvent croître en épitaxie sur des bases nanofilaires de GaN. De telles croissances, effectuées par épitaxie par jets moléculaires dans le cadre dans le cas présent, permettent la caractérisation ultérieure de petits volumes d’AlGaN exempt de défauts étendus communément observés dans les couches planaires. Cette absence de défauts rend ces fils prometteurs pour les dispositifs optoélectroniques émettant dans l’ultraviolet. Cependant, la réalisation de tels composants nécessite de mieux comprendre les propriétés fondamentales des fils.La question des inhomogénéités d’alliage à l’échelle nanométrique reste notamment à éclaircir. Afin d’y voir plus clair, ces dernières ont été dans un premier temps étudiées dans cette thèse. Pour nos expériences, des nanofils d’AlGaN non-intentionnellement dopés (NID) ont été crûs dans des conditions variées afin d’ajuster potentiellement les fluctuations de composition de l’alliage et ainsi sonder éventuellement des centres de localisation de porteurs de taille et composition différentes. Il a premièrement été observé au moyen de méthodes de caractérisation structurale que la longueur des sections plus riches Al qui nucléent préférentiellement au sommet des fils de GaN peut être ajustée en variant les paramètres cinétiques de croissance, mettant en lumière un mécanisme de croissance gouverné par la cinétique. Des études optiques ont ensuite démontré que les fluctuations de composition induisent de la localisation et présentent un comportement de type boîte quantique. Ce dernier a été observé quel que soit les conditions de croissance explorées dans ce travail. Il est ensuite démontré que les régions plus riches Ga spontanément formés durant la synthèse de l’AlGaN partagent des propriétés µ-optiques similaires sur une plage de longueur d’onde d’émission donnée, pour toutes les conditions de croissance utilisées dans cette étude. De telles régions, émettrices de photons uniques, sont présentes à très petite échelle, puisque elles ont été également mises en évidence dans des nanodisques quantiques d’AlGaN très fins.En outre, le dopage des nanofils d’AlGaN, surtout de type p, est loin d’être totalement compris. En particulier, En particulier, le problème de l’incorporation ainsi que de l’activation optique et électrique dans les fils demeure nébuleux. Cette question a été étudiée pour des jonctions pn nanofilaires d’AlGaN dopées avec des atomes Mg et Si. Premièrement, des signatures propres à l’incorporation des dopants dans les nanofils ont été mises en exergue au travers de techniques de caractérisation structurale, avant que des jonctions pn AlGaN soient mises en évidence électriquement. De plus, des analyses optiques ont mis en lumière des dopants de type n et p optiquement actifs. Néanmoins, les dopants Mg ne sont que partiellement actifs électriquement en raison de la passivation par l’hydrogène mise en évidence par l’observation de complexes Mg-H. Pour résoudre ce problème, des recuits post-croissance ont été effectués. En parallèle, des jonctions pn nanofilaires d’AlN ont été préliminairement examinées et présentent des caractéristiques morphologiques intéressantes. En effet, des creux profonds ont été observés dans les fils et associés au dopage Mg effectué à basse température de croissance. La morphologie des fils peut être ajustée en jouant sur les paramètres cinétiques de croissance et sur l’effet surfactant des atomes Mg. En augmentant la température, les creux disparaissent tandis que la forme du sommet des fils, usuellement hexagonale, change pour devenir « étoilée », mettant en exergue des conditions de croissance très éloignées de l’équilibre thermodynamique. L’activation électrique des dopants n’a pas été observée jusqu’à présent dans ces jonctions pn d’AlN. / Using specific growth conditions, AlGaN nanowire (NW) sections can be grown in epitaxy on top of GaN NW templates. Such NW growth, performed by plasma-assisted molecular beam epitaxy in the present case, allows the subsequent characterization of very small volume of material free of extended defects commonly observed in planar structures. This absence of defects makes these NWs very promising for optoelectronic devices operating in the ultraviolet. However, achieving such devices requires a better understanding of the NW fundamental properties.The issue of alloy inhomogeneity at nanoscale has notably remained obscure so far. In order to make it clearer, the latter has been first investigated in the present work, especially through optical characterization. For our experiments, non-intentionally doped (NID) AlGaN NWs have been grown in various conditions in order to potentially tune the compositional fluctuations within the AlGaN alloy and therefore possibly probe for carrier localization centers of different size and Al composition. It has been firstly observed through structural characterization that the length of Al-rich sections preferentially nucleating on top of GaN NWs can be tuned by varying the growth kinetical parameters, emphasizing a growth mechanism governed by kinetics. Optical studies have then evidenced that compositional fluctuations induce carrier localization and exhibit a quantum dot-like behavior. The latter has been observed whatever the growth conditions explored in this work. Our results are consistent with the spontaneous formation during growth of tiny Ga-richer regions shown to share similar micro-optical features over a given emission wavelength range for all investigated growth conditions. Such regions exhibiting the single-photon emission character are present at very small scale, as signs of their existence have been also evidenced in thin NID AlGaN quantum disks.In addition, doping in Al(Ga)N NW, especially p-type, is far from being fully comprehended. In particular, the issue of dopant incorporation as well as optical and electrical activation in such NWs remains unclear. The latter has been examined in Al(Ga)N NW pn junctions doped with Mg and Si atoms. First, signatures specific to dopant incorporation in NWs have been highlighted through structural characterization, before evidencing AlGaN pn junctions electrically. Moreover, optical analysis have exhibited optically active both dopant types. Nonetheless, Mg dopants are but partially active electrically due to passivation by hydrogen emphasized by the observation of Mg-H complexes. To cope with the latter issue, post-growth annealing experiments have been attempted. Concomitantly, AlN NW pn junctions have been also preliminarily investigated and present interesting morphological features. Indeed, deep hollows have been observed in NWs and associated with Mg doping carried out at low growth temperature. The NW morphology can be tuned by varying growth kinetical parameters and by using the surfactant effect of Mg atoms. When increasing growth temperature, these hollows disappear, while the NW top shape has been observed to switch from hexagonal to star-like, emphasizing growth conditions very far from thermodynamical equilibrium. Electrical activation of dopants has not been evidenced so far in AlN NW pn junctions.

Uma vasta gama de sensores são aplicados no mercado atual na busca pela melhoria de processos e produtos. Há um grande crescimento em novos sistemas que possam apresentar recursos que técnicas convencionais não apresentam. A busca por uma nova plataforma de sensoriamento surge a partir do interesse em identificar e controlar parâmetros ambientais isolados. Esta pesquisa em área incipiente no Brasil mostra o desenvolvimento de um sensor a partir de um material inteligente (smart material), que por definição, possui uma ou mais propriedades que podem sofrer mudanças significativas a partir de um estímulo externo. O presente trabalho é baseado na investigação de uma fita de material magnético amorfo, que ao exibir propriedades magnéticas e elásticas pelo efeito da magnetostricção, permite o monitoramento remoto de fenômenos físico-químicos do ambiente em que estiver exposta. O desenvolvimento deste sensor tem finalidade no monitoramento sem fio de solicitação mecânica, e alteração do tipo de fluido presente em um dado ambiente. O estudo e avaliação do sensor contou com técnicas de caracterização experimentais e de simulação. São apresentados sistemas e ensaios capazes verificar as ressonâncias do modo de vibração puro da amostra a partir de medidas ópticas e elétricas, quando submetidos a variação de fenômenos físicos. Os resultados indicam a dependência do efeito direto ao estímulo na ação externa do campo magnético em decorrências das características do material. Os resultados quantificados e qualificados na correlação entre os métodos utilizados, justificam a aplicação do smart material no sensoriamento de viscosidade e carregamento aplicado em ambientes isolados. Em consequência das discussões apresentadas para as curvas comportamentais na variação dos parâmetros físico-químico a plataforma de sensoriamento é validada. / New amorphous magnetic materials have magnetic and elastic properties which allows the identification and control of environmental parameters remotely. This work was based in the investigation of a magnetoelastic thin strip, widely used as anti-theft device. In this study it was discussed the employment of this material as a sensor capable identify an environmental change through magnetoelasticity. In order to characterize the strips it was employed several techniques, namely: finite element modeling of the vibrational modes, electromagnetic impedance and laser interferometry. It was presented an analysis of the displacement of the longitudinal modes. The knowledge of the vibration mode allowed the sensor electric characterization when subjected to environmental changes. According to the sample dimensions under magnetic field, test systems were developed in order to perform optic and electric measurements. A proper parameter adjustment of the power supply allowed the determination of the fundamental and higher order resonance frequencies. The magnetostrictive behaviour of the anti-theft strips is related to the Young modulus where the vibration frequency is inversely proportional to the length of the strip. Studies showed that the strip performance is also related to many other parameters, such as the mechanical and electromagnetic properties and the environment to which it is exposed. The strips here presented are largely employed as sensor for temperature, pressure, density, mas variation, viscosity and flux velocity mainly because their wireless capabilities. The data from the polarization field are a section of the knowledge required to better investigate the best performance of the sensor. The sensor characterization through several techniques applied in viscous media and under pressure raise some issues. However, the construction of some devices allowed the application of different values of viscosity and pressure upon the magnetized strip. This made the results interpretation less complex. The resonances were observed in the experimental data and mathematical modellin. Calibration curves were defined to make the results interpretation easier.Previously applied and studied techniques which cover the characterization and behaviour of the material provide valid justifications for the implementation of remote sensors made of amorphous metallic strips. The results presented here justify the application of the analysed amorphous strip as a viscosity and pressure sensor in isolated enviroments.

Cette thèse s’intéresse à une technique de caractérisation particulièrement bien adaptée à l’étude de couches diélectriques ultra-minces sur semiconducteurs. La génération de seconde harmonique (SHG) est une méthode très prometteuse, basée sur l’optique non-linéaire. Un laser est focalisé sur l'échantillon à caractériser et le signal à deux fois la fréquence fondamentale est mesuré. Pour les matériaux centrosymétriques comme c-Si, SiO2 et Al2O3, le signal SHG est dû aux défauts et au champ électrique Edc d’interface (induit par les charges préexistantes Qox et/ou piégées au niveau des pièges d’interface Dit). La SHG donne ainsi accès à la qualité des interfaces entre diélectriques/semiconducteurs. Néanmoins, le signal SHG dépend aussi des phénomènes de propagation optique dans les structures multicouches. Pour cette raison, nous avons développé un programme de simulation qui prend en compte les phénomènes optiques et les champs électriques statiques aux interfaces. Nous avons utilisé la SHG pour analyser la qualité de passivation de structures Al2O3/Si préparées avec des procédés différents et nous avons montré une corrélation entre SHG et mesure de durée de vie des porteurs de charges. Les valeurs de Qox et Dit ont été extraites par des mesures de capacité-tension et elles ont permis de calculer le champ Edc. La simulation optique, avec les valeurs extraites de Edc a permis de reproduire les données expérimentales de SHG dans ces structures. La SHG a été utilisée également pour la caractérisation des substrats Silicium-sur-Isolant (SOI). Pour les structures SOI épaisses, la simulation et les résultats expérimentaux ont montré que la réponse SHG est dominée par les interférences optiques (faible impact de Edc). Pour les structures SOI ultraminces, les interfaces sont couplées électriquement et des valeurs de Edc sont nécessaires pour reproduire les données expérimentales par simulation. Cela implique que pour les SOI ultraminces, la SHG pourrait donner accès aux champs électriques au niveau des interfaces d’une manière non-destructive. / This PhD work was developed in the context of research for novel characterization methods for ultra-thin dielectric films on semiconductors and their interfacial quality. Second harmonic generation (SHG) is a very promising non-invasive technique based on nonlinear optics. A laser emitting at the fundamental frequency is incident upon the sample which responds through its 2nd order polarization, generating a signal at twice the fundamental frequency. For centrosymmetric materials such as c-Si, amorphous SiO2 or Al2O3, the SHG signal is mainly due to the defects and to the static electric field Edc present at the interface (due to pre-existing charges Qox and/or photo-injected charge trapping/detrapping at interface traps Dit). Thus, SHG measurement gives access to the quality of dielectric/semiconductor interfaces. Nevertheless, the SHG signal is also dependent on multilayer optical propagation phenomena. For this reason, we have developed a simulation program which accounts for the optical phenomena and the static electric fields at the interfaces. We have used SHG to monitor the passivation quality of Al2O3/Si structures prepared with different processes and showed a correlation between SHG and minority carrier lifetime measurements. Qox and Dit were extracted from capacitance-voltage measurements and helped calculating the Edc values. The optical simulation, fed with known Edc values reproduced the experimental SHG data in these structures. The SHG was also used for Silicon-on-Insulator (SOI) substrates characterization. In thick SOI structures, both simulations and experimental results show that the SHG response is mainly given by optical interferences (Edc has no impact). In ultrathin SOI, the interfaces are electrically coupled and Edc is needed as input in the simulation in order to reproduce the experimental SHG data. This implies that in ultrathin SOI, SHG can access the interface electric fields in a non-destructive way.

Neste trabalho, foi realizada a síntese de compostos do sistema PbO CrO3, em especial as composições PbCrO4 e Pb2CrO5, pelo método dos precursores poliméricos, avaliando sua aplicação como pigmentos. Para eliminar o aspecto negativo quanto à toxicidade dos materiais envolvidos, foi realizada a dispersão dos mesmos em SiO2, pelo método sol-gel. As amostras foram caracterizadas estruturalmente por difração de raios X, espectroscopia Raman e por microscopia eletrônica de varredura e transmissão. Pelos resultados de difratometria de raios X e espectroscopia Raman, foi verificado que o método dos precursores poliméricos possibilita a formação de Pb2CrO5 e PbCrO4 monofásicos para ambas as estequiometrias estudadas. Contudo, as imagens de microscopia eletrônica de varredura mostram que as partículas das duas composições apresentam forte coalescência e aglomeração. A caracterização óptica foi realizada pela técnica de reflectância difusa e coordenadas colorimétricas, em que foi determinado que as amostras de PbCrO4 possuem coloração verde-amarelada e que as amostras de Pb2CrO5 possuem coloração que varia do laranja escuro ao vermelho. A dispersão em SiO2 das partículas de Pb2CrO5 foi alcançada, no entanto, este processo provocou a formação de diferentes fases cristalinas, além de alterações na cor, as quais têm uma contribuição significativa da própria matriz SiO2, fato confirmado pela teoria de Kubelka-Munk. A incorporação dessas partículas em uma matriz polimérica de um copolímero de etileno e acetato de vinila (EVA) resultou em uma coloração homogênea da mesma, confirmando a eficácia destas partículas como pigmentos. / In this work, the synthesis of particles from the PbO-CrO3 system, in particular the PbCrO4 and Pb2CrO5 compositions were accomplished, by a polymeric precursor method, evaluating its application as pigments. In order to eliminate the negative toxic aspect of these materials, the dispersion of the same in SiO2 was achieved, by the sol-gel method. The samples were characterized structurally by X-Ray diffraction, Raman spectroscopy and scanning and transmission electron microscopy. From X-Ray diffraction and Raman spectra results it was verified that the polymeric precursors method is able to form single phase Pb2CrO5 and PbCrO4 for both studied stoichiometries. Although, scanning electron microscope images revealed that both compositions present strong coalescence and agglomeration of the particles. Optical characterization was carried out by diffuse reflectance technique and colorimetric coordinates. It was verified that the PbCrO4 samples possess green-yellowish coloration and the Pb2CrO5 samples presents coloration that varies from dark orange to red. The dispersion of Pb2CrO5 particles in SiO2 was reached, however, this process causes the formation of different crystalline phases, besides alteration in color, which have a significant contribution from the SiO2 matrix, confirmed by Kubelka-Munk theory. The incorporation of these particles in a polymeric matrix of ethylene vinyl acetate copolymer (EVA) resulted in the coloration of the same, confirming the efficiency of these particles as pigments.

This dissertation focuses on near-field radiative transfer, which can be defined as the discipline concerned with energy transfer via electromagnetic waves at sub-wavelength distances. Three specific subjects related to this discipline are investigated, namely nearfield thermal radiation, nanoscale-gap thermophotovoltaic (nano-TPV) power generation and optical characterization. An algorithm for the solution of near-field thermal radiation problems in one-dimensional layered media is developed, and several tests are performed showing the accuracy, consistency and versatility of the procedure. The possibility of tuning near-field radiative heat transfer via thin films supporting surface phononpolaritons (SPhPs) in the infrared is afterwards investigated via the computation of the local density of electromagnetic states and the radiative heat flux between two films. Results reveal that due to SPhP coupling, fine tuning of near-field radiative heat transfer is possible by solely varying the structure of the system, the structure being the film thicknesses and their distance of separation. The coexistence of two regimes of near-field thermal radiation between two thin films of silicon carbide is demonstrated via numerical simulations and an asymptotic analysis of the radiative heat transfer coefficient. The impacts of thermal effects on the performances of nano-TPV power generators are investigated via the solution of the coupled near-field thermal radiation, charge and heat transport problem. The viability of nano-TPV devices proposed so far in the literature, based on a tungsten radiator at 2000 K and indium gallium antimonide cell, is questioned due to excessive heating of the junction converting thermal radiation into electricity. Using a convective thermal management system, a heat transfer coefficient as high as 105 Wm-2K-1 is required to maintain the junction at room temperature. The possibility of characterizing non-intrusively, and potentially in real-time, nanoparticles from 5 nm to 100 nm in size via scattered surface wave is explored. The feasibility of the characterization framework is theoretically demonstrated via a sensitivity analysis of the scattering matrix elements. Measurements of the scattering matrix elements for 200 nm and 50 nm gold spherical particles show the great sensitivity of the characterization tool, although an ultimate calibration is difficult with the current version of the experimental set-up.

Various carbon content hydrogenated amorphous silicon carbide (a-Si1&iexcl / xCx:H) and hydrogenated amorphous silicon (a-Si:H) thin films have been deposited on various substrates by using plasma enhanced chemical vapour deposition (PECVD) technique. Transmission spectra of these films have been determined within UV-Visible region and the obtained data were analysed to find related physical constants such as / refractive indices, thicknesses, etc. Fourier transform infrared (FT-IR) spectrometry technique has been used to determine transmission &amp / reflection type spectra of these films. Obtained data were analysed to determine bond structures of the films. E&reg / ects of relative concentration of ethylene (C2H4) gas on thin film bond structure and on optical constants have been questioned.

Uma vasta gama de sensores são aplicados no mercado atual na busca pela melhoria de processos e produtos. Há um grande crescimento em novos sistemas que possam apresentar recursos que técnicas convencionais não apresentam. A busca por uma nova plataforma de sensoriamento surge a partir do interesse em identificar e controlar parâmetros ambientais isolados. Esta pesquisa em área incipiente no Brasil mostra o desenvolvimento de um sensor a partir de um material inteligente (smart material), que por definição, possui uma ou mais propriedades que podem sofrer mudanças significativas a partir de um estímulo externo. O presente trabalho é baseado na investigação de uma fita de material magnético amorfo, que ao exibir propriedades magnéticas e elásticas pelo efeito da magnetostricção, permite o monitoramento remoto de fenômenos físico-químicos do ambiente em que estiver exposta. O desenvolvimento deste sensor tem finalidade no monitoramento sem fio de solicitação mecânica, e alteração do tipo de fluido presente em um dado ambiente. O estudo e avaliação do sensor contou com técnicas de caracterização experimentais e de simulação. São apresentados sistemas e ensaios capazes verificar as ressonâncias do modo de vibração puro da amostra a partir de medidas ópticas e elétricas, quando submetidos a variação de fenômenos físicos. Os resultados indicam a dependência do efeito direto ao estímulo na ação externa do campo magnético em decorrências das características do material. Os resultados quantificados e qualificados na correlação entre os métodos utilizados, justificam a aplicação do smart material no sensoriamento de viscosidade e carregamento aplicado em ambientes isolados. Em consequência das discussões apresentadas para as curvas comportamentais na variação dos parâmetros físico-químico a plataforma de sensoriamento é validada. / New amorphous magnetic materials have magnetic and elastic properties which allows the identification and control of environmental parameters remotely. This work was based in the investigation of a magnetoelastic thin strip, widely used as anti-theft device. In this study it was discussed the employment of this material as a sensor capable identify an environmental change through magnetoelasticity. In order to characterize the strips it was employed several techniques, namely: finite element modeling of the vibrational modes, electromagnetic impedance and laser interferometry. It was presented an analysis of the displacement of the longitudinal modes. The knowledge of the vibration mode allowed the sensor electric characterization when subjected to environmental changes. According to the sample dimensions under magnetic field, test systems were developed in order to perform optic and electric measurements. A proper parameter adjustment of the power supply allowed the determination of the fundamental and higher order resonance frequencies. The magnetostrictive behaviour of the anti-theft strips is related to the Young modulus where the vibration frequency is inversely proportional to the length of the strip. Studies showed that the strip performance is also related to many other parameters, such as the mechanical and electromagnetic properties and the environment to which it is exposed. The strips here presented are largely employed as sensor for temperature, pressure, density, mas variation, viscosity and flux velocity mainly because their wireless capabilities. The data from the polarization field are a section of the knowledge required to better investigate the best performance of the sensor. The sensor characterization through several techniques applied in viscous media and under pressure raise some issues. However, the construction of some devices allowed the application of different values of viscosity and pressure upon the magnetized strip. This made the results interpretation less complex. The resonances were observed in the experimental data and mathematical modellin. Calibration curves were defined to make the results interpretation easier.Previously applied and studied techniques which cover the characterization and behaviour of the material provide valid justifications for the implementation of remote sensors made of amorphous metallic strips. The results presented here justify the application of the analysed amorphous strip as a viscosity and pressure sensor in isolated enviroments.

Uma vasta gama de sensores são aplicados no mercado atual na busca pela melhoria de processos e produtos. Há um grande crescimento em novos sistemas que possam apresentar recursos que técnicas convencionais não apresentam. A busca por uma nova plataforma de sensoriamento surge a partir do interesse em identificar e controlar parâmetros ambientais isolados. Esta pesquisa em área incipiente no Brasil mostra o desenvolvimento de um sensor a partir de um material inteligente (smart material), que por definição, possui uma ou mais propriedades que podem sofrer mudanças significativas a partir de um estímulo externo. O presente trabalho é baseado na investigação de uma fita de material magnético amorfo, que ao exibir propriedades magnéticas e elásticas pelo efeito da magnetostricção, permite o monitoramento remoto de fenômenos físico-químicos do ambiente em que estiver exposta. O desenvolvimento deste sensor tem finalidade no monitoramento sem fio de solicitação mecânica, e alteração do tipo de fluido presente em um dado ambiente. O estudo e avaliação do sensor contou com técnicas de caracterização experimentais e de simulação. São apresentados sistemas e ensaios capazes verificar as ressonâncias do modo de vibração puro da amostra a partir de medidas ópticas e elétricas, quando submetidos a variação de fenômenos físicos. Os resultados indicam a dependência do efeito direto ao estímulo na ação externa do campo magnético em decorrências das características do material. Os resultados quantificados e qualificados na correlação entre os métodos utilizados, justificam a aplicação do smart material no sensoriamento de viscosidade e carregamento aplicado em ambientes isolados. Em consequência das discussões apresentadas para as curvas comportamentais na variação dos parâmetros físico-químico a plataforma de sensoriamento é validada. / New amorphous magnetic materials have magnetic and elastic properties which allows the identification and control of environmental parameters remotely. This work was based in the investigation of a magnetoelastic thin strip, widely used as anti-theft device. In this study it was discussed the employment of this material as a sensor capable identify an environmental change through magnetoelasticity. In order to characterize the strips it was employed several techniques, namely: finite element modeling of the vibrational modes, electromagnetic impedance and laser interferometry. It was presented an analysis of the displacement of the longitudinal modes. The knowledge of the vibration mode allowed the sensor electric characterization when subjected to environmental changes. According to the sample dimensions under magnetic field, test systems were developed in order to perform optic and electric measurements. A proper parameter adjustment of the power supply allowed the determination of the fundamental and higher order resonance frequencies. The magnetostrictive behaviour of the anti-theft strips is related to the Young modulus where the vibration frequency is inversely proportional to the length of the strip. Studies showed that the strip performance is also related to many other parameters, such as the mechanical and electromagnetic properties and the environment to which it is exposed. The strips here presented are largely employed as sensor for temperature, pressure, density, mas variation, viscosity and flux velocity mainly because their wireless capabilities. The data from the polarization field are a section of the knowledge required to better investigate the best performance of the sensor. The sensor characterization through several techniques applied in viscous media and under pressure raise some issues. However, the construction of some devices allowed the application of different values of viscosity and pressure upon the magnetized strip. This made the results interpretation less complex. The resonances were observed in the experimental data and mathematical modellin. Calibration curves were defined to make the results interpretation easier.Previously applied and studied techniques which cover the characterization and behaviour of the material provide valid justifications for the implementation of remote sensors made of amorphous metallic strips. The results presented here justify the application of the analysed amorphous strip as a viscosity and pressure sensor in isolated enviroments.

Orientadores: Lisandro Pavie Cardoso, Marco Sacilotti / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-08T18:38:56Z (GMT). No. of bitstreams: 1 Chiaramonte_Thalita_D.pdf: 12073771 bytes, checksum: d01b6c585fd5556757aea0542ecf63f2 (MD5) Previous issue date: 2007 / Resumo: Os nitretos (Ga, Al, In)N assim como os compostos GaInP, GaCuO2, representam um sistema de materiais muito importante para as aplicações em opto-eletrônica e dispositivos tais como os diodos emissores de luz (LEDs), lasers e nanosensores. Entretanto, o requisito essencial para as aplicações industriais desses materiais é a redução em seus tamanhos. Neste trabalho foram crescidos materiais metálicos formados por nitretos de gálio e também de semicondutores do tipo GaInP, GaCuO2 na forma de estruturas 3D, pela técnica de deposição química de organometálicos em fase vapor (MOCVD). Foi utilizado como precursor organometálico (OM) o trimetil gálio Ga(CH3)3e o nitrogênio N2 como gás portador. A temperatura e a pressão foram controladas durante o crescimento variando entre 500 e 750 o C e 100 a 760 Torr, respectivamente. Duas classes de estruturas 3D foram obtidas a partir da decomposição total ou parcial do gás pre-cursor, devido a interação entre o OM e o substrato que gera diferentes morfologias: i) as ligas metálicas (Ga, Al, In) formando estruturas semelhantes a balões, cetros (hastes com terminações esféricas) e neurônios, todos apresentando uma fina membrana de carbono amorfo que reveste a estrutura. Após o crescimento, estas estruturas foram submetidas ao processo de nitretação sob atmosfera de NH3 para transformá-las em micro/nanocristais de GaN; ii) os fios semicondutores micro/nanométricos com uma esfera metálica em sua terminação (bambus e cetros) . Na formação de ambas as estruturas, os precursores OM são como moléculas catalisadoras do crescimento. Este crescimento é considerado como um método alternativo e original para se obter estruturas 3D. Uma possível associação com o modelo apresentado pelo mecanismo de crescimento Vapor-Líquido-Sólido (VLS), que utiliza uma partícula metálica para promover os nanotubos de carbono e os nanofios semicondutores, ainda está em discussão. Informações estruturais e ópticas dessas novas estruturas crescidas sobre substratos de Cu (grade de difração), Si (001), InP (policristalino) e Al/SiO2/Si (fotolitografia) foram obtidas através da caracterização por difração de raios-X, microscopia eletrônica de varredura e de transmissão em alta resolução, espectroscopia por energia disper-siva, catodoluminescência e a espectroscopia de excitação por dois fótons. Nas amostras nitretadas, micro/nano cristais de GaN obtidos da liga de Ga aparecem impregnados no carbono turbostrático (folhas de carbono sem orientação obtidas do amorfo) que revestem as estruturas, e emitem na região do espectro l £ 365 nm, devido às suas dimensões quânticas. As hastes das estruturas do tipo bambus apresentam nódulos formados por discos monocristalinos de GaInP rotacionados de 60 o um em relação ao outro. Óxidos CuGaO2 e CuGa2O4compondo nanofios, denominados cetros, também foram obtidos / Abstract: Nitride (Ga, Al, In)N as well as GaInP, GaCu O2 compounds represent a very important class of materials to be used in the opto-electronic and devices applications such as light emission diodes (LEDs) lasers and nanosensors. However, the essential requirement to the industrial applications of these materials is the reduction in theirs sizes. In this work 3D structures based on gallium nitride and also GaInP, GaCuO2 semiconductors were grown by metalorganic chemical vapor deposition (MOCVD) technique. Trimethyl-gallium Ga(CH3) was used as the metal-organic (MO) precursor and nitrogen N2as carrier gas. During the growth to the temperature and pressure intervals of 500 - 700 oC and 100 - 760 Torr, respectively. Two 3D material classes were obtained from the total or partial precursor gas decomposition, since the interaction between the MO compound and the substrate gives rise to different morphologies: i) (Ga,In,Al) metallic alloys form ballons, scepters (wires with spherical ends) and neurons like structures, all involved by a thin carbon amorphous membrane. After growth, these structures were turned into GaN micro/nanocrystals by nitridation process under NH3 atmosphere; ii) micro/nanometer semiconductor wires with a metallic sphere at its end (bamboos and scepters). In order to form both structures, the MO precursors are taken as a catalyst molecule of the growth process. This is an alternative and original method to obtain 3D structures and a possible association to the model used in the vapour-liquid-solid (VLS) growth mechanism, in which a metallic particle promotes the carbon nanotubes and semiconductors nanowires is still under discussion. Structural and optical informations on these new structures grown on Cu (diffraction grid), Si(001), InP (polycrystalline) and Si/Al (photolithography) substrates were obtained through the characterization by X-ray diffraction, scanning electron microscope, high resolution transmission electron microscopy, en-ergy dispersive x-rays, cathodoluminescence and two photon excitation. In the nitrided samples, GaN micro/nanocrystals obtained from Ga alloy appear embedded in the turbostratic carbon (C sheets at random obtained from the amorphous) which involves the structures and, they emit in the l £ 365 nm region specter, due to their quantum dimensions. The bamboo rods present nodes consisting of GaInP single crystal discs turned by 60o one with respect to the other. The CuGaO2 and CuGa2O4 oxides compounding nanowires, called scepters, also were obtained. / Doutorado / Física / Doutor em Ciências