Rozprawy doktorskie na temat „Detectors”

El gran col· lisionador de hadrons (LHC), el qual te un circumferencia de 27 quilometres, és l'accelerador de partícules més gran i potent del món. El LHC esta dissenyat per fer col· lisionar protons a 14 TeV en el seu centre de massa, aconseguint una lluminositat de 1024 cm-2 s-1, quan 2808 paquets amb 1011 protons cada un, circulen per l'accelerador. Els paquets estan espaiats per 25 ns, que corresponen a una freqüencia de col · lisió de 40 MHz en cada un dels quatre punts d'interacció. Actualment, la principal prioritat de la estrategia europea per la física de partícules consisteix la explotació del LHC al seu maxim potencial. Es per aquest motiu que una actualització del LHC va ser planejada per tal d'assolir una nova fase d'intensa lluminositat del LHC (HL­ LHC). Aquesta nova fase del LHC (HL-LHC) necessitara una actualització tant de la maquina com dels detectors per tal que en 2030 es col · lecti deu vegades més dades que en el disseny inicial. El principals reptes que hauran de combatre els detectors per aquesta nova fase d'intensa lluminositat seran l'increment de l'ocupació, del pile-up, del ritme de dades i la resistencia a la radiació dels detectors. L'increment en l'ocupació sera mitigat utilitzant detectors amb major granularitat. Per altra banda detectors amb una resolució temporal de 30 ps seran utilitzats per recluir el pile-up. L'objectiu de la present tesis es el disseny, desenvolupament i estudi de detectors de silici amb una elevada granularitat i amb una resolució temporal de 30 ps, els quals compleixen amb les especificacions necessaries per l'actualització del experiment ATLAS (A Toroidal LHC Apparatus). La col· laboració RD50, la qual investiga en l'estudi de detectors resistents a la radiació, ha proposat els detectors de allau amb baix guany (LGAD) com a detectors per a timing en les Endcap Timing Layers (ETL). En aquesta tesis tres estrategies diferents s'han dut a terme per tal de complir amb les especificacions de granularitat, resolució temporal i resistencia a la radiació de la ETL. La primera estrategia ha consistit en la reducción del gruix dels LGAD per tal de recluir el temps de col · lecció, el temps de pujada i la contribució del intrínsec Landau noise en la resolució temporal. La segona estrategia duta a terme ha estat la minimització de la capacitat per tal de recluir el soroll i la contribució del jitter en la resolució temporal, desenvolupant detectors LGAD pixelats i en strips. Finalment, l'última estrategia s'ha focalitzat en l'ús de diferents impureses per tal de recluir efectes de la radiació derivats de l'ús del bor coma impuresa dopant. La estructura d'aquesta tesis es la següent: en el capítol 2 s'introdueixen el experiments d'altes energies on els detectors seran col · locats, les especificacions que han de complir els detectors en la nova fase d'intensa lluminositat, el funcionament dels detectors, la determinació de la resolució temporal, els efectes de la radiació en els detectors i un resum dels detectors utilitzats actualment per realitzar mesures de timing; en el capítol 3 es presenta les simulacions tecnologiques i experimentals dels detectors dissenyats; en el capítol 4 es resumeix els processos tecnológics realitzats en la fabricació dels detectors; el capítol 5 presenta els resultats cxpcrirncntals dcls dispositius fabricats aba.ns i dcsprós de irradiar-los: el capítol 6 sintctitza la simulació, producció i resultats dels inverse Low Gain Avalanche Detectors (i-LGAD), i el capítol 7 presenta les conclusions i treball fntur dels detectors fabricats.
The Large Hadron Collider (LHC) with its 27 kilometer in circumference is the world's largest and most powerful particle accelerator. The LHC was designed to collide protons at 14 TeV energy at the center-of-mass. The design luminosity is 1034 cm2 s-1, which is achieved with 2808 circulating bunches, each with - 1011 protons. Bunches are spaced by 25ns, corresponding to a collision rate of 40 MHz at each of the four interaction points. The main priority of the European Strategy for P article Physics is the exploitation of the full potential of the LHC. An upgrade of the LHC to the high-luminosity LHC (HL-LHC) was planned for this purpose. The HL-LHC will require an upgrade of the machine and detectors with a view to collecting ten times more data than in the initial design, by around 2030. The major challenges for the high-luminosity phase are the occupancy, pile-up, high data rates, and radiation tolerance of the detectors. The increase in occupancy will be mitigated using higher granularity. Fast timing detectors with time resolution in the range of 30 ps will be used to reduce pile-up. Fur thermore , precision timing will provide additional physics capabilities. The purpose of the present thesis is the design, development and study of silicon detectors with high granularity and 30 ps time resolution suitable for the upgrade of the A Toroidal LHC Apparatus (ATLAS) experiment in the HL-LHC phase. Low Gain Avalanche Detectors (LGAD) have been proposed by RD50 collaboration as timing detectors for the Endcap Timing Layer (ETL) of ATLAS experiment. Three different strategies have been studied in order to fulfil with the high granularity, time resolution and radiation hardness specifications of devices for the ET L. The first strategy has consisted in detectors thickness reduction to decrease its collection time, rise time and intrinsic Landau noise. The second strategy has been the minimization of the capacitance developing strips and pixels with gain. Finally, the last strategy has lied in the use of other dopants to reduce radiation effects as boron removal. The structure of the thesis is as follows: chapter 2 introduces the major issues in the LHC upgrade, the CERN experiments, the required specifications of particle detectors for the HL­ LHC phase, their working principles, the measurement of time resolution, the microscopic and macroscopic radiation effects, and the state of the art in timing detectors; chapter 3 presents the technological and electrical simulation of the designed devices after the calibration of the technological simulation with the process characterization; chapter 4 gives an outline of the different device processes; chapter 5 presents the obtained results of unirradiated and irradiated devices; chapter 6 condenses the simulation, production and results of inverse Low Gain Avalanche Detectors (i-LGAD), and chapter 7 reports the conclusions and future work of the measured devices.

Electronic noses (e-noses) have been utilized during the past three decades as general purpose instruments for chemical sensing. These instruments are inspired by natural olfactory systems, where fine odour discrimination is performed without the necessity for highly specialized receptors. Instead, odour information is extracted in these systems using arrays of broadly tuned receptors organized in a convergent pathway. Such a sensing architecture allows combining the responses of the array of receptors, giving rise to particular representations of the different odour stimuli. The key advantage provided by this approach is that odour representation is more efficient and robust when the encoding is performed by the population of receptors than by any of its individual elements (hyper-acuity). A population of receptors obtains its maximum performance in encoding odour stimulus features when it balances the benefits of sensory diversity and redundancy. By sensor diversity we understand the number of different receptor types responsible for enhancing the variability of the array response to a collection of odours. Likewise, by sensor redundancy we refer to the average number of receptor replicates on a population. The role of sensor redundancy accounts for the robustness to receptor damage and noise exhibited by the odour stimuli representation. This variety of odour receptor types along with its outstanding number of receptors is characteristic of natural olfactory systems. Though, traditional electronic noses tend to exhibit a limited number of sensor units with very much correlated responses to odour stimuli. Several strategies to enhance odour representation in gas sensor arrays are based on boosting sensor diversity and redundancy. However, it has not been until recently that large arrays of cross-selective have become technologically available. In this dissertation, we have developed one of these new generation arrays to investigate the advantages odour stimuli representation through population coding in artificial olfaction. In particular, we proposed to build a chemical sensing system based on an array of metal oxide (MOX) gas sensors, and endowed with a high a degree of sensor diversity and redundancy. We proposed the use this bio-inspired sensing architecture alongside statistical pattern recognition techniques to cope with some of the unsolved problems in machine olfaction (robustness to sensor damage, feature selection, and calibration transfer). The main contributions of this work were the following: We defined functionally sensor diversity and redundancy. These definitions were based on the clustering of the array features according to their similitude when responding to an odour dataset. We compared the different manner how natural and artificial olfactory systems encode for odour information using simple sensors models. We found that natural olfactory system principally encoded odour information in terms of odour quality, whereas that artificial ones in terms of odour quantity. Also, we studied the effect of sensor noise on odour concentration encoding. We proposed to decrease the contribution of the sensor noise by means of the redundant sensor feature averaging and sensor array optimization. These strategies were effective in case of independent sensor noise, but not for removing common sources of sensor noise. Similarly, we detected the importance of sensor failure dependency on the odour discrimination capabilities of a sensor. We found that this sensor fault distribution across had to be independent of the sensor type to prevent a dramatic worsening on the array’s predictive performance. In addition to this, we proposed an update of a feature selection method including a dimensionality reduction stage so as to take into account the redundant information provided by the sensor array. Finally, we performed instrument standardization between temperature modulated sensor arrays to correct global shifts of temperature. A method to categorize the quality of the calibration transfer based on the bias-variance trade-off was presented.
La nariz electrónica (e-nose) ha sido utilizada durante las últimas tres décadas como instrumento de propósito general para la detección química. Este instrumento está inspirado en los sistemas olfativos naturales, donde la discriminación de olores se realiza eficientemente sin la necesidad de receptores altamente especializados. La ventaja clave proporcionada por esta aproximación es que la representación de los olores es más eficiente y robusta cuando la codificación del olor es llevada a cabo por una población de receptores, pues esta supera la calidad de cualquiera realizada por sus elementos individuales. Una población de receptores obtiene su máximo rendimiento en la codificación de las características de un estímulo odorífero cuando se equilibran los beneficios de la diversidad y redundancia sensoriales. Lamentablemente, las narices electrónicas tradicionales tienden a exhibir un número limitado de sensores con respuestas muy correlacionas ante diferentes conjuntos de estímulos odoríferos. Sin embargo, no ha sido hasta hace relativamente poco que la creación grandes matrices de sensores con selectividades cruzadas ha sido tecnológicamente posibles. El objetivo de esta tesis es el desarrollo de una de estas matrices de nueva generación para investigar las ventajas de la representación de los estímulos odoríferos través de una codificación poblacional soportada por la diversidad y redundancia sensoriales. En particular, hemos construido un sistema de detección química basado en una matriz de sensores de gas de óxido metálico (MOX), y dotada de un alto grado de diversidad y redundancia sensoriales. Hemos utilizado esta arquitectura de detección química bioinspirada junto técnicas de reconocimiento de patrones estadísticas para hacer frente a algunos de los problemas sin resolver en olfacción artificial, a saber, la robustez al fallo de sensores, la selección de características, y la transferencia de calibración entre diferentes narices electrónicas.

Orientador: Neri Alves
Banca: Dante Luis Chanaglia
Banca: Felippe Jose Pavinatto
O Programa de Pós Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi
Resumo: Nesta dissertação é apresentada a produção e caracterização de sensores de umidade e amônia totalmente impressos, usando uma impressora jato de tinta comercial. "Tintas" de PANI e PEDOT:PSS foram preparadas e impressas usando uma impressora HP Deskjet D2460. Filmes do polímero condutor PEDOT:PSS foi impresso sobre substratos de papeis e de plásticos e suas propriedades morfológicas e elétricas foram avaliadas em função da densidade superficial de material impresso e da rugosidade dos substratos a fim de obter filmes impressos correntes elétricas suficientes para atuação como eletrodos. Filmes de PANI, com diferentes número de impressões, foram impressos entre os eletrodos de PEDOT:PSS e caracterizações elétricas para o dispositivo PANI/PEDOT/papel antes e após expor ao vapor de HCI, processo no qual promove a dopagem do dispositivo, usando medidas DC e de espectroscopia de impedância (EI). Mostra-se que os resultados, para o sistema impresso PANI/PEDOT/papel, podem ser modelados por um circuito equivalente contendo um resistor R em paralelo com um capacitador C, ambos em série com outro resistor r. As variações de cada parâmetro foram avaliadas em função da exposição a direrentes percentuais de umidade relativa do ar (%UR) e concentrações de amônia (% e ppm). O resistor r, contido no circuito equivalente demonstrou maior resposta e sensibilidade à exposição tanto de umidade quanto de gás amônia mostrando a viabilidade de aplicação deste sistema impresso como sensor. Uma maior sensibilidade para o sistema PANI/PEDOT/papel (sensores de papel) pode ser obtida realizando um tratamento térmico promovendo a evaporação do excesso de HCI no sistema. Para monitoramentos em baixas concentrações de NH3 dispositivos na configuração PANI/PEDOT/PET (sensores plásticos) apresentaram tanto resposta sensitiva quanto tempo de resposta melhores quando comparados aos sensores de papel tratados termicamente
Abstract: This work presents the production and characterization of humidity sensors and fully printed ammonia, using an inkjet printer commercial. "Inks" of PANIN and PEDOT:PSS were prepared and printed using an HP Deskjet D2460 printer. Films of the conducting polymer PEDOT:PSS was printed on paper and plastic substrates and their morphological and electrical properties were evaluated in function of the surface density of printed material and roughness of the substrate in order to obtain printed films with sufficient electrical current to operate as electrodes. Films of PANI, with different number of prints, were printed between the electrodes of PEDOT:PSS AND electrical characterization for the device PANI/PEDOT/paper, before and after exposed to steam HCI, process in which promoting the device doping, were realized using measures DC and impedance spectroscopy (EI). It shows that the results for the printing sytem PANI/PEDOT/paper can be modeled by an equivalent circuit comprising a resistor R in parallel with a capacitor C, both in series with another resistor r. Variations of each parameter were evaluated in function of exposure to different humidity percentage of the air (%RH) and ammonia concentrations (ppm and %). The resistor r contained in the equivalent circuit shown greater response and sensitivity to exposure as much moisture as gas ammonia showing the application feasibility of this system as printed sensor. An increased sensibility to the sytem PANI/PEDOT/paper (paper sensors) can be obtained by performing a heat treatment to promote evaporation of the excess of HCI in the system. For monitoring low concentrations of NH3, devices in PANI configuration PANI/PEDOT/PET (plastic sensors) demonstrated so much an better sensitive response low much an better time response compared to paper sensors treated thermally
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Nesta dissertação é apresentada a produção e caracterização de sensores de umidade e amônia totalmente impressos, usando uma impressora jato de tinta comercial. Tintas de PANI e PEDOT:PSS foram preparadas e impressas usando uma impressora HP Deskjet D2460. Filmes do polímero condutor PEDOT:PSS foi impresso sobre substratos de papeis e de plásticos e suas propriedades morfológicas e elétricas foram avaliadas em função da densidade superficial de material impresso e da rugosidade dos substratos a fim de obter filmes impressos correntes elétricas suficientes para atuação como eletrodos. Filmes de PANI, com diferentes número de impressões, foram impressos entre os eletrodos de PEDOT:PSS e caracterizações elétricas para o dispositivo PANI/PEDOT/papel antes e após expor ao vapor de HCI, processo no qual promove a dopagem do dispositivo, usando medidas DC e de espectroscopia de impedância (EI). Mostra-se que os resultados, para o sistema impresso PANI/PEDOT/papel, podem ser modelados por um circuito equivalente contendo um resistor R em paralelo com um capacitador C, ambos em série com outro resistor r. As variações de cada parâmetro foram avaliadas em função da exposição a direrentes percentuais de umidade relativa do ar (%UR) e concentrações de amônia (% e ppm). O resistor r, contido no circuito equivalente demonstrou maior resposta e sensibilidade à exposição tanto de umidade quanto de gás amônia mostrando a viabilidade de aplicação deste sistema impresso como sensor. Uma maior sensibilidade para o sistema PANI/PEDOT/papel (sensores de papel) pode ser obtida realizando um tratamento térmico promovendo a evaporação do excesso de HCI no sistema. Para monitoramentos em baixas concentrações de NH3 dispositivos na configuração PANI/PEDOT/PET (sensores plásticos) apresentaram tanto resposta sensitiva quanto tempo de resposta melhores quando comparados aos sensores de papel tratados termicamente
This work presents the production and characterization of humidity sensors and fully printed ammonia, using an inkjet printer commercial. Inks of PANIN and PEDOT:PSS were prepared and printed using an HP Deskjet D2460 printer. Films of the conducting polymer PEDOT:PSS was printed on paper and plastic substrates and their morphological and electrical properties were evaluated in function of the surface density of printed material and roughness of the substrate in order to obtain printed films with sufficient electrical current to operate as electrodes. Films of PANI, with different number of prints, were printed between the electrodes of PEDOT:PSS AND electrical characterization for the device PANI/PEDOT/paper, before and after exposed to steam HCI, process in which promoting the device doping, were realized using measures DC and impedance spectroscopy (EI). It shows that the results for the printing sytem PANI/PEDOT/paper can be modeled by an equivalent circuit comprising a resistor R in parallel with a capacitor C, both in series with another resistor r. Variations of each parameter were evaluated in function of exposure to different humidity percentage of the air (%RH) and ammonia concentrations (ppm and %). The resistor r contained in the equivalent circuit shown greater response and sensitivity to exposure as much moisture as gas ammonia showing the application feasibility of this system as printed sensor. An increased sensibility to the sytem PANI/PEDOT/paper (paper sensors) can be obtained by performing a heat treatment to promote evaporation of the excess of HCI in the system. For monitoring low concentrations of NH3, devices in PANI configuration PANI/PEDOT/PET (plastic sensors) demonstrated so much an better sensitive response low much an better time response compared to paper sensors treated thermally

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O presente trabalho está baseado na construção de sensores biomiméticos para monitoramento sensível e seletivo do agrotóxico metribuzin (MTZ). Para isto, eletrodos à base de pasta de carbono e nanotubos de carbono foram modificados com diversos complexos potenciais catalisadores biomiméticos das enzimas P450, que são enzimas que catalisam um grande número de reações incluindo os agrotóxicos. O complexo que apresentou perfil biomimético e melhores resultados na determinação amperométrica do metribuzin foi à ftalocianinacobalto (II) [CoPc]. Quando construídos sensores à base de pasta de carbono modificada com CoPc, os melhores resultados foram obtidos usando 15% (m/m) de complexo na preparação da pasta e realizando as medidas em tampão Britton-Robinson 0,08 mol L-1 (pH 2,0), aplicando potencial de -690 mV vs Ag|AgCl. Sob estas condições obteve-se uma faixa linear de resposta de 2,4 x 10-5 a 2,0 x 10-4 mol L-1, com uma boa sensibilidade e LOD e LOQ de 4,3 x 10-6 e 1,4 x 10-5 mol L-1, respectivamente. Estudos relacionados a elucidar a biomimeticidade do sensor, incluíram avaliação da influência da velocidade de varredura empregando voltametria cíclica, exploração do perfil hiperbólico da resposta do sensor e estudo de interferentes e de seletividade. A seguir, foi avaliada a influencia de nanotubos de carbono de paredes múltiplas (MWCNT) na preparação da pasta no intuito de tentar aumentar a detectabilidade do sensor modificado com ftalocianinacobalto (II). Entretanto, os resultados obtidos não foram àqueles esperados, devido principalmente, à grande quantidade de material aglutinante (Nujol® que é isolante) necessário para a obtenção da pasta. Assim, a seguir, foi realizada a avaliação de eletrodos impressos à base de grafite, contendo MWCNT a 0,3% e CoPc a 5%, 10% e 15% (m/m). Sob as condições de...
This work is based on the construction of biomimetic sensors for monitoring sensitive and selective pesticide metribuzin (MTZ). For this, the base electrodes of carbon paste and carbon nanotubes have been modified with various complex catalysts potential biomimetic of P450 enzymes, which are enzymes that catalyze a large number of reactions including pesticides. The complex profile that showed better results in biomimetic and amperometric determination of metribuzin was the ftalocianinacobalto (II) [CoPc]. When constructed sensors based on a modified carbon paste CoPc with the best results were obtained using 15% (m/ m) complex in the preparation of the folder and making the measurements in Britton-Robinson buffer 0,08 mol L-1 (pH 2,0), by applying potential to -690 mV vs Ag | AgCl. Under these conditions gave a linear response range of 2.4 x 10-5 to 2.0 x 10-4 mol L-1, and with good sensitivity and LOQ and LOD of 4,3 x 10-6 and 1 , 4 x 10-5 mol L-1, respectively. Related studies to elucidate the biomimeticidade sensor, included evaluation of the influence of scan rate using cyclic voltammetry, exploitation of hyperbolic profile of the sensor response and the study of interferences and selectivity. Next, we evaluated the influence of carbon nanotubes multi-walled (MWCNT) in the preparation of the folder in order to try to increase the detectability of the sensor modified with ftalocianinacobalto (II). However, the results were not those expected, mainly due to the large amount of binder material (Nujol ® which is an insulator) necessary for obtaining the paste. Thus, the following evaluation was made electrodes printed based on graphite containing MWCNT CoPc 0,3% and 5%, 10% and 15% (m / m). Under the above conditions optimized for the analysis carbon paste, the printed electrode that provided the best... (Complete abstract click electronic access below)

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O presente trabalho está baseado no desenvolvimento de um sistema biomimético para monitoramento sensível e seletivo do metabólito TCP (3,5,6-tricloro-2-piridinol), proveniente do agrotóxico clorpitifós, o qual é mais solúvel que o próprio agrotóxico e cuja ocorrência em águas subterrâneas e superficiais é mais provável e perigosa. Foi construído um sensor biomimético com detecção voltamétrica por onda quadrada, os eletrodos, foram confeccionados à base de pasta de carbono modificada com o complexo cloro-5,10,15,20-tetraquis(pentafluorofenil)-21H,23H-porfirina ferro (III), o qual apresenta uma estrutura química semelhante à do sítio ativo da enzima P450. O sensor construído apresentou as melhores respostas em tampão fosfato 0,20 mol L-1 e pH 6,0, usando a voltametria de onda quadrada a 50 Hz, 150 mV de amplitude e 1,5 mV de E. Com os parâmetros otimizados o sensor apresentou limites de detecção e de quantificação de 1,9 e 5,2 μmol L-1, respectivamente. Estudos realizados para averiguar a biomimeticidade do sensor, incluíram: velocidade de varredura por voltametria cíclica, exploração do perfil hiperbólico da resposta no sensor e avaliação da seletividade. O sensor foi satisfatoriamente usado na análise em diversos tipos de amostras de interesse ambiental. Foram feitos testes de recuperação e nas amostras de solo, águas superficiais e subterrâneas obtendo recuperação de 91%, 107% e 96% respectivamente, mostrando que o sensor pode ser usado como método alternativo para quantificação de TCP em diferentes matrizes. O sensor também foi empregado no monitoramento da eficiência de polímeros de impressão molecular (MIP) para TCP. Buscando obter o polímero biomimético mais eficiente para o analito, foram usadas ferramentas computacionais que permitiram escolher o melhor monômero (acrilonitrila)...
This work is based on developing a biomimetic system for sensitive and selective monitoring of the TCP (3,5,6-trichloro-2-pyridinol), the principal metabolite of the pesticide chlorpyrifos, which is more soluble than the pesticide and whose occurrence in groundwater and surface water is more likely and dangerous. For this, a biomimetic sensor was constructed and the square wave voltammetric was used for measurements. The electrodes were fabricated using carbon paste modified with the complex chloro-5,10,15,20-tetrakis-(pentafluorophenyl)-21H,23H-porphyrin iron(III), which has a chemical structure similar to the active site of the enzyme P450. The sensor presented the best responses in phosphate buffer 0.20 mol L-1 and pH 6.0, using the square wave voltammetry with 50 Hz, amplitude of potential of 150 mV and ΔE of 1.5 mV. With the optimized parameters the sensor showed limits of detection and quantification of 1.9 and 5.2 μmol L-1, respectively. Studies conducted to investigate the mimicking of the sensor, included evaluation of the influence on scan rate in the cyclic voltammetry, the verification of the hyperbolic profile of the sensor response and evaluation of selectivity. The sensor has been satisfactorily applied in the analysis of different samples of environmental interest. Recovery experiments in samples of soil, surface water, and groundwater showed values of 91%, 107% and 96% respectively, showing that the sensor can be used as an alternative method for the quantification of TCP in different matrices. The sensor was also used to monitor the efficiency of molecularly imprinted polymers (MIP) for TCP. In order to obtain the most efficient biomimetic polymer to this analyte were used computational tools that allowed select the best monomer (acrylonitrile). In order to verify the results obtained by the theoretical... (Complete abstract click electronic access below)

Orientador: Maria Del Pilar Taboada Sotomayor
Banca: Iara Lucia Tescarollo Dias
Banca: Emerson Schwingel Ribeiro
Resumo: O presente trabalho está baseado na construção de sensores biomiméticos para monitoramento sensível e seletivo do agrotóxico metribuzin (MTZ). Para isto, eletrodos à base de pasta de carbono e nanotubos de carbono foram modificados com diversos complexos potenciais catalisadores biomiméticos das enzimas P450, que são enzimas que catalisam um grande número de reações incluindo os agrotóxicos. O complexo que apresentou perfil biomimético e melhores resultados na determinação amperométrica do metribuzin foi à ftalocianinacobalto (II) [CoPc]. Quando construídos sensores à base de pasta de carbono modificada com CoPc, os melhores resultados foram obtidos usando 15% (m/m) de complexo na preparação da pasta e realizando as medidas em tampão Britton-Robinson 0,08 mol L-1 (pH 2,0), aplicando potencial de -690 mV vs Ag|AgCl. Sob estas condições obteve-se uma faixa linear de resposta de 2,4 x 10-5 a 2,0 x 10-4 mol L-1, com uma boa sensibilidade e LOD e LOQ de 4,3 x 10-6 e 1,4 x 10-5 mol L-1, respectivamente. Estudos relacionados a elucidar a biomimeticidade do sensor, incluíram avaliação da influência da velocidade de varredura empregando voltametria cíclica, exploração do perfil hiperbólico da resposta do sensor e estudo de interferentes e de seletividade. A seguir, foi avaliada a influencia de nanotubos de carbono de paredes múltiplas (MWCNT) na preparação da pasta no intuito de tentar aumentar a detectabilidade do sensor modificado com ftalocianinacobalto (II). Entretanto, os resultados obtidos não foram àqueles esperados, devido principalmente, à grande quantidade de material aglutinante (Nujol® que é isolante) necessário para a obtenção da pasta. Assim, a seguir, foi realizada a avaliação de eletrodos impressos à base de grafite, contendo MWCNT a 0,3% e CoPc a 5%, 10% e 15% (m/m). Sob as condições de... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This work is based on the construction of biomimetic sensors for monitoring sensitive and selective pesticide metribuzin (MTZ). For this, the base electrodes of carbon paste and carbon nanotubes have been modified with various complex catalysts potential biomimetic of P450 enzymes, which are enzymes that catalyze a large number of reactions including pesticides. The complex profile that showed better results in biomimetic and amperometric determination of metribuzin was the ftalocianinacobalto (II) [CoPc]. When constructed sensors based on a modified carbon paste CoPc with the best results were obtained using 15% (m/ m) complex in the preparation of the folder and making the measurements in Britton-Robinson buffer 0,08 mol L-1 (pH 2,0), by applying potential to -690 mV vs Ag | AgCl. Under these conditions gave a linear response range of 2.4 x 10-5 to 2.0 x 10-4 mol L-1, and with good sensitivity and LOQ and LOD of 4,3 x 10-6 and 1 , 4 x 10-5 mol L-1, respectively. Related studies to elucidate the biomimeticidade sensor, included evaluation of the influence of scan rate using cyclic voltammetry, exploitation of hyperbolic profile of the sensor response and the study of interferences and selectivity. Next, we evaluated the influence of carbon nanotubes multi-walled (MWCNT) in the preparation of the folder in order to try to increase the detectability of the sensor modified with ftalocianinacobalto (II). However, the results were not those expected, mainly due to the large amount of binder material (Nujol ® which is an insulator) necessary for obtaining the paste. Thus, the following evaluation was made electrodes printed based on graphite containing MWCNT CoPc 0,3% and 5%, 10% and 15% (m / m). Under the above conditions optimized for the analysis carbon paste, the printed electrode that provided the best... (Complete abstract click electronic access below)
Mestre

Orientador: Maria Del Pilar Taboada Sotomayor
Banca: Marcos Roberto de Vasconcelos Lanza
Banca: Rosa Amália Fireman Dutra
Resumo: O presente trabalho está baseado no desenvolvimento de um sistema biomimético para monitoramento sensível e seletivo do metabólito TCP (3,5,6-tricloro-2-piridinol), proveniente do agrotóxico clorpitifós, o qual é mais solúvel que o próprio agrotóxico e cuja ocorrência em águas subterrâneas e superficiais é mais provável e perigosa. Foi construído um sensor biomimético com detecção voltamétrica por onda quadrada, os eletrodos, foram confeccionados à base de pasta de carbono modificada com o complexo cloro-5,10,15,20-tetraquis(pentafluorofenil)-21H,23H-porfirina ferro (III), o qual apresenta uma estrutura química semelhante à do sítio ativo da enzima P450. O sensor construído apresentou as melhores respostas em tampão fosfato 0,20 mol L-1 e pH 6,0, usando a voltametria de onda quadrada a 50 Hz, 150 mV de amplitude e 1,5 mV de E. Com os parâmetros otimizados o sensor apresentou limites de detecção e de quantificação de 1,9 e 5,2 μmol L-1, respectivamente. Estudos realizados para averiguar a biomimeticidade do sensor, incluíram: velocidade de varredura por voltametria cíclica, exploração do perfil hiperbólico da resposta no sensor e avaliação da seletividade. O sensor foi satisfatoriamente usado na análise em diversos tipos de amostras de interesse ambiental. Foram feitos testes de recuperação e nas amostras de solo, águas superficiais e subterrâneas obtendo recuperação de 91%, 107% e 96% respectivamente, mostrando que o sensor pode ser usado como método alternativo para quantificação de TCP em diferentes matrizes. O sensor também foi empregado no monitoramento da eficiência de polímeros de impressão molecular (MIP) para TCP. Buscando obter o polímero biomimético mais eficiente para o analito, foram usadas ferramentas computacionais que permitiram escolher o melhor monômero (acrilonitrila)... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This work is based on developing a biomimetic system for sensitive and selective monitoring of the TCP (3,5,6-trichloro-2-pyridinol), the principal metabolite of the pesticide chlorpyrifos, which is more soluble than the pesticide and whose occurrence in groundwater and surface water is more likely and dangerous. For this, a biomimetic sensor was constructed and the square wave voltammetric was used for measurements. The electrodes were fabricated using carbon paste modified with the complex chloro-5,10,15,20-tetrakis-(pentafluorophenyl)-21H,23H-porphyrin iron(III), which has a chemical structure similar to the active site of the enzyme P450. The sensor presented the best responses in phosphate buffer 0.20 mol L-1 and pH 6.0, using the square wave voltammetry with 50 Hz, amplitude of potential of 150 mV and ΔE of 1.5 mV. With the optimized parameters the sensor showed limits of detection and quantification of 1.9 and 5.2 μmol L-1, respectively. Studies conducted to investigate the mimicking of the sensor, included evaluation of the influence on scan rate in the cyclic voltammetry, the verification of the hyperbolic profile of the sensor response and evaluation of selectivity. The sensor has been satisfactorily applied in the analysis of different samples of environmental interest. Recovery experiments in samples of soil, surface water, and groundwater showed values of 91%, 107% and 96% respectively, showing that the sensor can be used as an alternative method for the quantification of TCP in different matrices. The sensor was also used to monitor the efficiency of molecularly imprinted polymers (MIP) for TCP. In order to obtain the most efficient biomimetic polymer to this analyte were used computational tools that allowed select the best monomer (acrylonitrile). In order to verify the results obtained by the theoretical... (Complete abstract click electronic access below)
Mestre

Orientador: Maria Valnice Boldrin Zanoni
Banca: Hideko Yamanaka
Banca: Orlando Fatibello Filho
Banca: Mauro Bertotti
Banca: Auro Atsushi Tanaka
Resumo: O presente trabalho investiga a aplicação de eletrodos impressos, de carbono (SPCE) e ouro (SPGE), na determinação de espécies de interesse farmacêutico, tais como, aurotiomalato, L-dopa e procaína, utilizando sistemas convencionais, com fluxo de solução e análise por injeção em fluxo, respectivamente. Após a otimização de todos os parâmetros voltamétricos e inerentes da técnica construí-se curvas analíticas para cada composto farmacêutico com respostas lineares entre concentrações de 1,4 x 10-6 a 1,5 x 10-4 mol L-1, 1,5 x 10-6 a 6,6 x 10-4 mol L-1 e 1,0 x 10-5 a 1,0 x 10-4 mol L-1 para o aurotiomalato, a L-dopa e a procaína, respectivamente. O método foi aplicado na determinação dessas espécies em formulações farmacêuticas. A construção e caracterização voltamétrica de. eletrodos de carbono impresso (SPCE) por filmes de poli-histidina (PH) foi também investigada com intuito de ampliar o nível de sensibilidade e seletividade dos métodos voltamétricos. Para isso, foram testados três diferentes procedimentos de para a construção dos eletrodos modificados: a adição direta de uma solução do polímero (SPCE/PH), a utilização de uma reação cruzada entre a poli-histidina e o glutaraldeído (SPCE/Glu-PH) e a eletropolimerização a partir do monômero histidina (SPCE/EPH). O comportamento voltamétrico dos eletrodos modificados mostrou-se fortemente dependente do procedimento de preparação dos filmes. Eletrodos SPCE/PH e SPCE/Glu-PH apresentaram uma alta eficiência na pré-concentração de ânions, como o ferricianeto. Não sendo observado nenhum efeito eletrocatalítico para a oxidação de ácido ascórbico com esses eletrodos. Já para o SPCE/EPH foi observado um baixo desempenho na pré-concentração de ânions, mas um pronunciado efeito eletrocatalítico para a oxidação de ácido ascórbico. A aderência e estabilidade das respostas obtidas...(Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The present work investigated the application of screen-printed carbon (SPCE) and screen-printed gold electrodes (SPGE) in the determination of species of pharmaceutical interest, such as, aurothiomalate, L-dopa and procaine. The performance of all electrodes was tested in a conventional electrochemical system, and also in two electrochemical cells using amperometric detection. The first one was constructed to operate on hydrodynamic system and the second one to work on flow injection analysis (FIA) system. Analytical curves were obtained for all systems with linear relationship from peak current vs concentration from 1.4 x 10-6 to 1.5 x 10-4 mol L-1 for aurothiomalate; 1.5 x 10-6 to 6.6 x 10-4 mol L-1 for L-dopa and 1.0 x 10-5 to 1.0 x 10-4 mol L-1 for procaine, respectively. The method was tested in pharmaceutical compounds with good recovery. Screen-printed carbon electrodes (SPCE) can be easily modified with poly-histidine (PH) films using three different procedures: by direct addition of a poly-histidine solution on the electrode surface (SPCE/PH), using a cross-link reaction between poly-histidine and glutaraldehyde (SPCE/Glu-PH) and by electropolymerization of the histidine monomer (SPCE/EPH). The voltammetric behavior of the three modified electrodes was evaluated using potassium hexacyanoferrate(III) and ascorbic acid as model compounds. All modified electrode from stable films, but SPCE coated by deposition of PH and Glu-PH presented higher efficiency for pre concentration anions, while SPCE coated by electropolymerization of the monomer (EPH) presented pronounced electrocatalytic effect in the ascorbic acid oxidation. The resulting PH films presented good adherence and high stabilities and they were applied in the voltammetric analysis of isoniazide, pyrazinamide, aurothiomalate and chromium (VI). The best experimental condition for isoniazide and pyrazinamide...(Complete abstract click electronic access below)
Doutor

Aquesta tesi presenta la caracterització d’un disseny de detector pxel de CdTe per aplicació en imatge en medicina nuclear. El treball d’aquesta tesi s’ha portat a terme en el marc del projecte Voxel Imaging PET (VIP) Pathnder. El projecte VIP es un projecte ambiciós que pretén provar la viabilitat d’utilitzar detectors pixel·lats de CdTe en imatge en medicina nuclear. El disseny proposat és el mòdul VIP, que consta de blocs de CdTe de 10 mm 10 mm de superfcie i 2 mm de gruix, que estan segmentats en pxels de 1 mm 1 mm. Cada diode de CdTe és llegit pel VIP-PIX, un xip desenvolupat pel projecte VIP i que ofereix una lectura intelligent i independent per píxel i proporciona la mesura en energia i en temps per cada detecció. El treball presentat en aquesta tesi és la caracterització del rendiment de tres experiments per validar el comportament del mòdul VIP. En primer lloc s’ha realitzat la mesura de la resolució en energia i la resolució en coincidència temporal per un detector coplanar de 2 mm de gruix. En segon lloc, s’ha mesurat el charge sharing entre píxels. Per a aquest propòsit, s’ha utilitzat un experiment amb un diode de CdTe llegit per xip VATAGP7.1. L’efecte del charge sharing en la resolució en energia dels píxels també s’ha estudiat. Finalment, s’ha evaluat el rendiment d’un diode de CdTe llegit pel xip VIP-PIX. El rendiment dels circuits electrònics del VIP-PIX s’han caracteriztat i s’ha mesurat la resolució en energia dels píxels de CdTe Aquesta tesi consta de 7 capítols. El capítol 1 parla de la física en la detecció de radiació, especialment centrada en la detecció gamma. El capítol 2 parla de la medicina nuclear, les tècniques utilitzades i els escàners més novedosos emprats en aquest àmbit. El capítol 3 parla del projecte VIP, mostra els detalls del disseny VIP, els objectius aconseguits ns al moment i els objectius a assolir per al nal del projecte. Els capítols 4, 5, i 6 mostren cadascuna de les tres etapes dels experiments realitzats durant la tesi. El capítol 4 mostra les mesures de resolució en energia i coincidència en temps de detecció d’un detector amb un únic píxel de 2 mm de gruix. El capítol 5 mostra les mesures de charge sharing per un detector amb píxels de 2 mm 1 mm i el seu efecte en la resolució en energia. El capítol 6 mostra la mesura de resolució en energia per un detector de CdTe pixel·lat llegit pel xip VIP-PIX, que té píxels de 1 mm 1 mm. El capítol 7 presenta les conclusions assolides amb els tres anàlisis i els posa en el context del camp de deteccio de radiacions per a imatge mèdica.
This thesis presents the characterization of a pixel CdTe detector design for application in nuclear medicine imaging. The thesis work has been carried out within the framework of the Voxel Imaging PET (VIP) Pathfinder project. The VIP project is an ambitious project that aims to prove the feasibility of using pixelated CdTe detectors in nuclear medicine imaging. The proposed design is the VIP module, which consists of slabs of CdTe of 10 mm x 10 mm surface and 2 mm thickness, which are segmented into pixels of 1 mm x 1 mm. Each CdTe diode is readout by the VIP-PIX, an ASIC developed by the VIP project which others smart readout per pixel and provides the energy measurement and the timestamp for each detection. The work presented in this thesis is the characterization of the performance of three different setups to validate the behavior of the VIP module. One of the steps consists of the measurement of the energy resolution and the coincidence time resolution for a CdTe coplanar detector of 2 mm thickness. In the second step the charge sharing between pixels has been measured. A setup with a CdTe diode readout by the VATAGP7.1 has been used. The e ect of the charge sharing on the energy resolution of the pixels has been studied as well. Finally, the performance of a CdTe diode readout by a VIP-PIX ASIC has been evaluated. The performance of the VIP-PIX electronics has been characterized and the energy resolution of the CdTe pixels has been measured. The thesis consists of 7 chapters. Chapter 1 is about the physics behind radiation detection, especially focused on gamma detection. Chapter 2 is about nuclear medicine, the techniques used and the state-of-the-art of nuclear medicine scanner devices. Chapter 3 is about the VIP project, it shows the details of the VIP design, the goals achieved so far, and the targets for the end of the project. Chapters 4, 5, and 6 show each of the three stages of experiments carried out in the thesis. Chapter 4 shows the energy resolution and coincidence time resolution of a single pixel detector with 2 mm thickness. Chapter 5 shows the measurement of charge sharing for a pixel detector with pixels of 2 mm x 1 mm and its effect on the energy resolution. Chapter 6 shows the measurement of the energy resolution for a pixelated CdTe diode readout by the VIP-PIX ASIC, which has pixels of 1 mm x 1 mm. Chapter 7 presents the conclusions achieved with the three analyses and puts them in the context of the radiation detection science for medical imaging.

Orientadores: Jose Alexandre Diniz, Davies William de Lima Monteiro
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Resumo: Sensores de Pixel Ativo (APS) baseados em tecnologia nMOS simples e com alta razão de aspecto podem apresentar boa sensibilidade para fotodetecção e oferecer uma opção de baixo custo para circuitos de sensoreamento de imagens. Neste trabalho são apresentados o leiaute, fabricação e caracterização de fotodiodos, transitores e APSs construídos no Centro de Componentes Semicondutores (CCS). Todas as etapas do projeto foram realizadas no CCS, incluindo as máscaras litográficas, fabricadas em um processo óptico. Foi utilizado um processo nMOS de 5[j,m, de porta metálica, com uma camada de metal para interconexões e apenas quatro níveis de litografia. Os dispositivos apresentam resultados satisfatórios e compatíveis ao comportamento previsto em simulações SPICE, indicando que podem obter bom desempenho em circuitos para aplicações específicas, como sensores ópticos de posição e sensores de frente de onda, em diversas áreas, como astronomia, oftalmologia e microscopia de força atômica (AFM)
Abstract: Active Pixel Sensors (APS) based on a simple nMOS technology with high aspect ratio may present good sensitivity to photodetection and offer a low cost option for image sensing circuits. This work presents the layout, fabrication and characterization of photodiodes, transistors and APSs built at the Center for Semiconductor Components (CCS). All the process stages took place in CCS, including the manufacturing of the lithography masks through an optical process. The technology used was an nMOS, 5[j,m, metal gate, with a single metal layer for interconnections and only four lithography levels. The devices presented satisfactory results, compatible to the behavior predicted by SPICE simulations, suggesting a good performance in application specific circuits, such as optical position sensitive detectors and wavefront sensors, and in several fields, such as astronomy, ophthalmology and atomic force microscopy (AFM)
Mestrado
Eletrônica, Microeletrônica e Optoeletrônica
Mestre em Engenharia Elétrica

Neste trabalho, construímos um novo e versátil forno de crescimento de cristais pela técnica de Bridgman, o qual pode operar em temperaturas de até 2000 °C em alto-vácuo ou atmosferas inertes. Visto que o problema mais importante após o crescimento de um cristal por esta técnica é a aderência entre o mesmo e as paredes do caidinho, construímos também um sistema para tratamento do material de partida que eliminou este fenômeno. Este procedimento permitiu a obtenção de monocristais cilíndricos de NaI(Tl) transparentes, com alta qualidade e com cerca de 60 mm de comprimento e diâmetro de 20 mm. Utilizando a técnica de Czochralski, crescemos também vários monocristais cilíndricos transparentes de NAI(Tl) com comprimentos de 50 mm e diâmetros de 30 mm. Descrevemos também um método para eliminar o excesso de iodo dissolvido na fase líquida durante o processo de crescimento do cristal. Medidas de absorção ótica realizadas com os cristais de NAI(Tl) à temperatura ambiente e do nitrogênio líquido, mostram bandas de absorção características do Tálio próximas de 304, 291, 257, 249 e 236 nm. Através da relação entre a densidade ótica da banda de absorção em 304 nm e a concentração de tálio, estimamos o perfil da concentração deste elemento ao longo de um cristal crescido por Cz e por Bridgman. Através de espectroscopia de fluorescência encontramos, à temperatura ambiente, uma banda de emissão centrada em 425 nm. Protótipos de detetores foram construídos para avaliar as resoluções de energia dos monocristais crescidos pelos métodos de Bridgman e Czochralski. A performance dos detetores também foi analisada
In this work we constructed a new versatile Bridgman crystal growth furnace that can operate to 2.000 °C in high vacuum or in inert atmospheres. Since the most important post-growth problem in this technique is related with the adherence between crystal-crucible, we also developed an initial materials-treatment system that could prevent this phenomenon, by previously saturating with HI gas. These procedures allowed us to get clear and high quality NaI(Tl) cylindric single crystals up to 60mm length and 20mm diameter. Using the Czochralski technique, we also grew several clear NaI(Tl) single crystals with dimensions up to 50 mm length and 30 mm diameter. A method to prevent the excess of Iodine in the liquid phase during the crystal growth process is also described. Optical absorption measurements in NaI(Tl) single crystals, at room and liquid nitrogen temperatures, show characteristic Thallium bands near 304, 291, 257, 249 and 236 nm. Through the relationship between optical density of the absorption band at 304 nm and Thallium concentration, we could estimate the concentration profile through the entire crystal, grown by each method: Bridgman and Czochralski. By fluorescence spectroscopy we also find, at room temperature, one emission band near to 425 nm. Radiation detector prototypes were developed to evaluate the energy resolution of the single crystals grown by Bridgman and Czochralski methods. The performance of the radiation detectors is also analyzed

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Neste trabalho foram estudadas a produção e caracterização de filmes finos poliméricos escovas sobre substrato de óxido de indio e estanho (ITO), a fim de se avaliar as propriedades estímulo-responsivas que levam às mudanças estruturais dos filmes. Para a caracterização das superfícies dos filmes foram utilizadas as técnicas de microscopia atômicac de varredura (MEV), energia dispersiva de raio-X (EDX) e microscopia de força atômica (AFM). A influência do pH e da força iônica foram avaliadas pelos métodos eletroquímicos e de ressonância plasmônica de superfície localizada (L-SPR). Os polímeros (Poli(ácido acrílico)-(PAA), Poli(2-vinil piridina)-(P2VP), Poli(2-dimetil amino etil metacrilato) (PDMAEMA) e a mistura de P2VP com PAA foram utilizados na construção dos filmes em escova. Os ensaios eletroquímicos revelaram uma dependência da conformação dos polímeros escovas com a variação da força iônica e pH, sendo que, P2VP e PDMAEMA tiveram melhor resposta em pH ácido, um vez que as cadeias poliméricas estavam estendidas e carregadas positivamente, permitindo a difusão da espécie redox carregada negativamente até a superfície do eletrodo. Contra intuitivamente, o polímero PAA também apresentou uma resposta amperométrica ótima em pH ácido, quando suas cadeias estavam neutras colapsadas sobre a superfície, esse fato curioso foi devido ao fato da espécie redox utilizada nos ensaios ser carregada negativamente, ocorrendo, portanto, repulsão eletrostática na configuração em que o PAA estava com suas cadeias estendidas e carregadas negativamente (pH básico). Os ensaios de L-SPR corroboraram com os obtidos por via eletroquímica. Também foi possível obter o valor da sensibilidade dos eletrodos frente a variação de pH, sendo que o sensor mais sensível foi o de P2VP, para cada unidade de pH o sensor deslocou 11 unidade de comprimento de onda. Foi possível a determinação dos regimes osmótico...
This study describes the production and characterization of polymer brushes thin films build on indium tin oxide substrate (ITO) in order to study the stimuli-responsive properties that lead to structural changes of the films. To characterize the surfaces atomic microscopy, energy dispersive X-ray and atomic force microscopy techniques were used. The influence of pH and ionic strength were evaluated by electrochemical methods and localized surface plasmon resonance (L-SPR). The polymers ply (acrylic acid) - (PAA), poly (2-vinyl pyridine) - (P2VP), poly (2-dimethyl amino ethyl methacrylate) (PDMAEMA) and the mixture P2VP with PAA were used to construct the brush films. Electrochemical tests showed a dependence of the polymer brushes conformation with ionic strengh and pH. P2VP and PDMAEMA had better response at acidic pH, since the polymer chains were extended and positively charged, allowing the diffusion of the negatively charged redox species through the film to the electrode surface. Not intituitively, PAA polymer film also showed a better amperometric response in acid pH, when their chains were collapsed on the surface. This curious response was because the redox species used in the tests were charged negatively, occurring thus electrostatic repulsion between the PAA negatively streched chains (basic pH) and the negatively charged redox specie, thus leading to a major signal in acidic pH where the PAA brushes were neutral. The results obteined by electrochemistry were corroborated usign L-SPR assays. It was also possible to obtain the sensitivity value due to pH variation using L-SPR measurements. P2VP showed the highest sensibility: for each pH unit, 1 unitis wavelength were shifted. It was also determined the range of salt concentration related with the osmotic regime, unconventional osmotic regime and salted regime transitions for each electrode. The electrodes P2VP, PAA, PDMAEMA and P2VP/PAA were applied as glucose biosensor...
FAPESP: 13/12623-2

Orientador: Valber de Albuquerque Pedrosa
Banca: Gustavo Rocha de Castro
Banca: Ivana Cesarino
O "Programa de Pós Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi
Resumo: Neste trabalho foram estudadas a produção e caracterização de filmes finos poliméricos escovas sobre substrato de óxido de indio e estanho (ITO), a fim de se avaliar as propriedades estímulo-responsivas que levam às mudanças estruturais dos filmes. Para a caracterização das superfícies dos filmes foram utilizadas as técnicas de microscopia atômicac de varredura (MEV), energia dispersiva de raio-X (EDX) e microscopia de força atômica (AFM). A influência do pH e da força iônica foram avaliadas pelos métodos eletroquímicos e de ressonância plasmônica de superfície localizada (L-SPR). Os polímeros (Poli(ácido acrílico)-(PAA), Poli(2-vinil piridina)-(P2VP), Poli(2-dimetil amino etil metacrilato) (PDMAEMA) e a mistura de P2VP com PAA foram utilizados na construção dos filmes em escova. Os ensaios eletroquímicos revelaram uma dependência da conformação dos polímeros escovas com a variação da força iônica e pH, sendo que, P2VP e PDMAEMA tiveram melhor resposta em pH ácido, um vez que as cadeias poliméricas estavam estendidas e carregadas positivamente, permitindo a difusão da espécie redox carregada negativamente até a superfície do eletrodo. Contra intuitivamente, o polímero PAA também apresentou uma resposta amperométrica ótima em pH ácido, quando suas cadeias estavam neutras colapsadas sobre a superfície, esse fato curioso foi devido ao fato da espécie redox utilizada nos ensaios ser carregada negativamente, ocorrendo, portanto, repulsão eletrostática na configuração em que o PAA estava com suas cadeias estendidas e carregadas negativamente (pH básico). Os ensaios de L-SPR corroboraram com os obtidos por via eletroquímica. Também foi possível obter o valor da sensibilidade dos eletrodos frente a variação de pH, sendo que o sensor mais sensível foi o de P2VP, para cada unidade de pH o sensor deslocou 11 unidade de comprimento de onda. Foi possível a determinação dos regimes osmótico...
Abstract: This study describes the production and characterization of polymer brushes thin films build on indium tin oxide substrate (ITO) in order to study the stimuli-responsive properties that lead to structural changes of the films. To characterize the surfaces atomic microscopy, energy dispersive X-ray and atomic force microscopy techniques were used. The influence of pH and ionic strength were evaluated by electrochemical methods and localized surface plasmon resonance (L-SPR). The polymers ply (acrylic acid) - (PAA), poly (2-vinyl pyridine) - (P2VP), poly (2-dimethyl amino ethyl methacrylate) (PDMAEMA) and the mixture P2VP with PAA were used to construct the brush films. Electrochemical tests showed a dependence of the polymer brushes conformation with ionic strengh and pH. P2VP and PDMAEMA had better response at acidic pH, since the polymer chains were extended and positively charged, allowing the diffusion of the negatively charged redox species through the film to the electrode surface. Not intituitively, PAA polymer film also showed a better amperometric response in acid pH, when their chains were collapsed on the surface. This curious response was because the redox species used in the tests were charged negatively, occurring thus electrostatic repulsion between the PAA negatively streched chains (basic pH) and the negatively charged redox specie, thus leading to a major signal in acidic pH where the PAA brushes were neutral. The results obteined by electrochemistry were corroborated usign L-SPR assays. It was also possible to obtain the sensitivity value due to pH variation using L-SPR measurements. P2VP showed the highest sensibility: for each pH unit, 1 unitis wavelength were shifted. It was also determined the range of salt concentration related with the osmotic regime, unconventional osmotic regime and salted regime transitions for each electrode. The electrodes P2VP, PAA, PDMAEMA and P2VP/PAA were applied as glucose biosensor...
Mestre

Orientador: Marcelo Ornaghi Orlandi
Banca: Silvio Rainho Teixeira
Banca: Neftal Lenin Villarreal Carreño
Banca: José Roberto Siqueira Junior
Banca: Regina Célia Galvão Frem
Resumo: A eficiência dos materiais semicondutores óxidos metálicos utilizados em dispositivos sensores, depende fortemente de parâmetros morfológicos e estruturais. É de grande interesse que os materiais apresentem um elevado grau nos parâmetros de medidas que definem um bom sensor, como: sinal, sensibilidade, seletividade. Devido a isso, métodos de sínteses adequados têm grande influência no desempenho dos dispositivos, já que interferem diretamente na morfologia e estrutura dos materiais semicondutores. Através dessa perspectiva, nesse trabalho, morfologias do composto semicondutor óxido metálico ZnO foram superficialmente modificadas com o intuito de realizar melhorias para aplicações em sensores de gás e de radiação luminosa (fotocondução) na faixa do ultravioleta. Dois métodos de sínteses foram utilizados: i) evaporação térmica por redução carbotérmica e ii) hidrotermal assistido por micro-ondas, responsáveis por obter morfologias tipo tetrapés e estrelas multipontas, respectivamente. Processos de evaporação térmica por redução carbotérmica tem a grande vantagem de obter estruturas com morfologias unidimensionais, em contrapartida, o método hidrotermal assistido por micro-ondas pode sintetizar uma enorme gama de diferentes morfologias com a vantagem de ser um processo rápido e de baixos custos energéticos. Técnicas como microscopia eletrônica de varredura, microscopia eletrônica de transmissão, difração de raios-X, espectroscopia ultravioleta visível e infravermelho, foram utili... (Resumo completo, clicar acesso eletrônico abaixo)
Doutor

Materiais amorfos demonstraram possuir um comportamento magnetomecânico superior ao de qualquer outro material magnético. Isso vêm permitindo sua utilização para um crescente número de finalidades de sensoriamento. A capacidade de interrogar remotamente a frequência de ressonância de fitas de material amorfo através de campos magnéticos permite a aplicação destas como sensores em situações que não permitem acesso direto à superfície de medição. Essa qualidade pode ser útil no monitoramento de risers que trazem petróleo do fundo do mar até plataformas na superfície. A frequência de ressonância das fitas amorfas depende, entre outras propriedades, da intensidade do campo magnético no qual estão inseridas. Desta forma, a deformação de um substrato pode ser monitorada através do uso de um transdutor nele colado, o qual se magnetiza à medida que o substrato deforma, consequentemente mudando o campo magnético imposto sobre o ressonador e a sua frequência de ressonância. Neste trabalho, a construção de um sensor magnetoelástico de deformação é investigada, onde uma liga policristalina de FeAlB foi utilizada como transdutor, e fitas de materiais amorfos, de nomes comerciais Metglas 2826 MB3 e 1K501, foram utilizadas como ressonadores. A liga de Fe80Al20, com 2%at. de B, mostrou ter uma magnetostricção de 80 ppm, o que inspirou o seu uso como transdutor, o que possibilita a substituição das fitas amorfas utilizadas anteriormente. Uma bancada de testes, capaz de aplicar tensão mecânica a um substrato de latão, foi construída com o objetivo de testar a sensibilidade do sensor magnetoelástico à deformação. Foi observado um comportamento altamente linear da frequência de ressonância do sensor com a tensão aplicada sobre o substrato de latão, com Gauge Factors de 120 e 90 para os sensores que utilizaram Metglas 2028 MB3 e 1K501 como ressonadores, respectivamente. Este resultado instigou a exploração da aplicabilidade do sensor magnetoelástico em substratos ferromagnéticos. Por fim, ensaios de tração foram realizados, nos quais a deformação dos substratos de aço SAE 1010 foram monitoradas simultaneamente pelo sensor magnetoelástico e por um Strain Gauge. A variação de frequência de ressonância do sensor nestes esaios apresentou uma forma mais sigmoidal, com uma região quase linear. O monitoramento de um riser com este dispositivo seria factível
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES
Amorphous metals have been shown to have magnetomechanical properties which are superior to those of any other magnetic materials. This has allowed their usage in a growing number of sensing purposes. The capacity of remotely interrogating the resonant frequency of amorphous material stripes trough magnetic fields allows their application as sensor in situations that do now allow direct contact with the measurement surface. This quality may be useful for the monitoring of risers that bring petrol from deep sea to platforms on the surface. The resonant frequency of the stripes is a function of, alongside other properties, the intensity of the magnetic field in which they are inserted. Thus, a substrate’s deformation may be monitored trough the use of a transducer in him affixed, which magnetizes as the substrate deforms, consequently altering the magnetic field imposed over the resonator, and its resonant frequency. In this work, the construction of a magnetoelastic strain sensor is investigated, where a polycrystalline FeAlB alloy was used as transducer, and amorphous materials, by the commercial name of Metglas 2826 MB3 and 1K501, were used as resonators. The Fe80Al20 alloy, with 2%at. B, was shown to have an 80 ppm magnetostriction, which inspired its use as transducer, which enabled the substitution of the amorphous ribbons previously used. A testing bench, capable of applying mechanical stress to a brass substrate, was built with the goal of teste the sensibility of the magnetoelastic sensor to strain. A highly linear behavior of the sensor’s resonant frequency to the applied stress on the brass substrate was observed, with Gauge Factors of 120 for the sensors that used Metglas 2826 MB3 and 1K501 as resonators, respectively. This result instigated the exploration of the magnetoelastic sensor’s applicability on ferromagnetic surfaces. Finally, mechanical stress tests were conducted, in which the deformation of the SAE 1010 steel substrate were simultaneously monitored by the magnetoelastic sensor, and a Strain Gauge. The resonant frequency of the sensor is this test showed a sigmoidal form, with a nearly linear region. The monitoring of a riser with this device is feasible

A new set of thermal neutron detectors has been developed as a near term 3He tube replacement. The zinc oxide scintillator is an ultrafast scintillator which can be doped to have performance equal to or superior to 3He tubes. Originally investigated in the early 1950s, this room temperature semiconductor has been evaluated as a thermal neutron scintillator. Zinc oxide can be doped with different nuclei to tune the band gap, improve optical clarity, and improve the thermal neutron detection efficiency. The effects of various dopant effects on the scintillation properties, materials properties, and crystal growth parameters have been analyzed. Two different growth modalities were investigated: bulk melt grown materials as well as thin film scintillators grown by metalorganic chemical vapor deposition (MOCVD). MOCVD has shown significant advantages including precise thickness control, high dopant incorporation, and epitaxial coatings of neutron target nuclei. Detector designs were modeled and simulated to design an improved thermal neutron detector using doped ZnO layers, conformal coatings and light collection improvements including Bragg reflectors and photonic crystal structures. The detectors have been tested for crystalline quality by XRD and FTIR spectroscopy, for scintillation efficiency by photo-luminescence spectroscopy, and for neutron detection efficiency by alpha and neutron radiation tests. Lastly, a novel method for improving light collection efficiency has been investigated, the creation of a photonic crystal scintillator. Here, the flow of optical light photons is controlled through an engineered structure created with the scintillator materials. This work has resulted in a novel radiation detection material for the near term replacement of 3He tubes with performance characteristics equal to or superior to that of 3He.

Energy or DFT detector using a fixed window size is very efficient when signal start time and duration is matched with that of the window'
s. However, in the case of unknown signal duration, the performance of this detector decreases. For this scenario, a detector system composed of multiple windows may be preferred. Window sizes of such a system will also be fixed beforehand but they will be different from each other. Therefore, one of the windows will better match the signal duration, giving better detection results. In this study, multiple window detectors are analyzed. Their false alarm and detection probability relations are investigated. Some exact and approximate values are derived for these probabilities. A rule of thumb for the choice of window lengths is suggested for the case of fixed number of windows. Detectors with overlapping window structure are considered for the signals with unknown delay. Simulation results are added for these types of detectors.

Abstract The multiple-input multiple-output (MIMO) technique combined with an orthogonal frequency division multiplexing (MIMO--OFDM) has been introduced as a promising approach for the ever increasing capacity and quality of service (QoS) requirements for wireless communication systems. An efficient radio spectrum utilization expects a flexible transceiver solution, which has been the reason for the development of the software defined radio (SDR) technologies which in their turn are expected to enable the creation of cognitive radios. As a result, any radio solution could be invoked on demand on any platform. In this thesis work, we have studied detector algorithms and programmable processor architectures in order to find practical solutions for the future wireless systems. A programmable receiver can reduce the energy dissipation of the receiver by changing the detection algorithm based on the current channel realizations. To provide a realistic aspect to the implementations in different channel realizations, we present a wide state-of-the-art detector comparison. In addition, we present an extensive number arithmetic and word length study in order to evaluate realistic hardware complexity and energy dissipations of the implementations. The study includes a comprehensive design chain from the algorithm development to the actual processor design and finally programming software for the platforms. We evaluate single and multi-core processor implementations by comparing the achieved results to the Long Term Evolution (LTE) performance requirements. We implement detectors on digital signal processors (DSPs), graphics processing unit (GPU) and transport triggered architecture (TTA). The implementation results are compared in throughput, silicon area and energy efficiency. Finally, we discuss the advantages and disadvantages of the architectures and the implementation effort
Tiivistelmä Usean antennin tekniikka yhdistettynä ortogonaaliseen taajuusvaihtelumodulointiin lähetin-vastaanotimessa on esitetty eräänä lupaavana ratkaisuna jatkuvasti kasvaviin kapasiteetti- ja palvelunlaatuvaatimuksiin langattomissa tietoliikennejärjestelmissä. Tehokas radiospektrin käyttö edellyttää joustavaa lähetin-vastaanotinratkaisua, mikä on ollut syynä ohjelmistoradioteknologioiden kehitykselle. Ohjelmistoradioiden kehityksen on puolestaan odotettu mahdollistavan kognitiiviradioiden syntymisen. Tuloksena, mikä tahansa radiosovellus voitaisiin herättää tarpeen mukaan millä tahansa ohjelmoitavalla sovellusalustalla. Tässä väitöskirjatyössä tutkitaan ilmaisinalgoritmeja sekä ohjelmoitavia prosessoriarkkitehtuureja tarkoituksena löytää käytännöllisiä ratkaisuja tulevaisuuden langattomiin järjestelmiin. Ohjelmoitavalla vastaanottimella voidaan vähentää vastaanottimen energiankulutusta vaihtamalla ilmaisinalgoritmeja vallitsevan kanavatilan mukaan. Työssä esitellään laaja, viimeisintä tutkimusta edustava ilmaisinalgoritmivertailu, joka antaa realistisen näkökannan toteutuksiin erilaisissa kanavatiloissa. Lisäksi työssä esitellään numeroaritmetiikka- ja sananpituustutkimus, jonka tarkoituksena on arvioida toteutusten realistista kovokompleksisuutta sekä energiankulutusta. Tutkimus sisältää kattavan suunnitteluketjun algoritmikehityksestä todelliseen prosessorisuunnitteluun ja lopulta algoritmin ohjelmointiin tietylle sovellusalustalle. Väitöskirjatyössä arvioidaan yksi- ja moniytimisiä prosessoritoteutuksia vertaamalla saavutettuja tuloksia Long Term Evolution -standardin suorituskykyvaatimuksiin. Ilmaisimia toteutetaan digitaalisilla signaaliprosessoreilla, grafiikkaprosessorilla sekä siirtoliipaisuarkkitehtuurilla. Toteutustuloksia vertaillaan laskentatehona, pinta-alana sekä energiatehokkuutena. Lopuksi käsitellään arkkitehtuurien hyviä ja huonoja puolia sekä suunnittelun työläyttä

The current network of three terrestrial interferometric gravitational wave detectors have observed ten binary black holes and one binary neutron star to date in the frequency band from 10 Hz to 5 kHz. Future detectors will increase the sensitivity by up to a factor of 10 and will push the sensitivity band down to lower frequencies. However, observing sources lower than a few Hz requires going into space where the interferometer arms can be longer and where there is no seismic noise. A new 100 km space detector, TianGO, sensitive to the frequency band from 10 mHz to 100 Hz is described. Through its excellent ability to localize sources in the sky, TianGO can use binary black holes as standard candles to help resolve the current tension between measurements of the Hubble constant. Furthermore, all of the current and future detectors, on both the ground and in space, are limited by quantum shot noise at high frequencies, and some will be limited by quantum radiation pressure at low frequencies as well. Much effort is made to use squeezed states of light to reduce this quantum noise, however classical noise and losses severely limit this reduction. One would ideally design a gravitational wave transducer that, using its own ability to generate ponderomotive squeezing due to the radiation pressure mediated interaction between the optical modes of the light and the mechanical modes of the mirrors, approaches the fundamental limits to quantum measurement. First steps in this direction are described and it is shown that it is feasible that a large scale 40 m interferometer can observe this ponderomotive squeezing in the near future. Finally, a method of removing the effects of the vacuum fluctuations responsible for the quantum noise in gravitational wave detectors and its application to testing for the presence of deviations from general relativity is described.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 153-161).
Superconducting nanowire single-photon detectors (SNSPDs) are a promising technology for long-distance optical communication and quantum information processing. Recent advances in single-photon generation, storage and detection technologies have spurred interest in integration of these components onto a single microchip, which would act as a low-power non-classical optical processor. In this thesis, I will present a method for the scalable integration of SNSPDs with photonic chips. I will show that, using a micron-scale flip-chip process, waveguide-coupled SNSPDs can be integrated onto a variety of material systems with high yield. This technology enabled the assembly of the first photonic chip with multiple adjacent SNSPDs with average system detection efficiencies beyond 10%. Using this prototype, we will show the first on-chip detection of non-classical light. I will further demonstrate optimizations to the detector design and fabrication processes. These optimizations increased the direct fabrication yield and improved the timing jitter to 24 ps for detectors with high internal efficiency. Furthermore, I will show a novel single-photon detector design that may have the potential to reach photodetection dead times below 1ns.
by Faraz Najafi.
Ph. D.

Lab measurements and Monte Carlo simulations have been carried out for the evaluation of the Straw-type detectors used in the NA62 experiment at CERN. In addition, analyses of experiment data was used in corrections to improve the reconstruction of particle tracks, ultimately leading to improved resolution of the detector system as a whole. 97.7 percent of the Straws were aligned to within 30 microns, quantified as the deviation from zero of the mean of the inherent residual distribution of each Straw. A drift time dependence on where along the Straw the particle ionized have been corrected for; before the correction the dependence was as big as 6 ns. A radius-drift time relation based on the leading edge timing distribution has been deduced and implemented. Upon implementation artifacts from the piecewise fits used became evident. An alternative approach using residuals has been put forward.

The development of new technologies and the advancement of existing technical expertise can allow for dramatic improvements to be realized in analytical instrumentation. The development of an integrating solid-state ion detector, designed to have a high sensitivity as well as maintaining a high-level of stability, is described and evaluated. Several versions of the charge-transimpedance amplifier (CTIA) technology were constructed with different operating features. The CTIA-1 is a 32-pixel array detector designed for mass spectrometry. It has the capability to simultaneously detect multiple ion channels with a detection limit less than 100 ions. The CTIA-2 detector features an independent selectable gain for each detection channel. The CTIA-2 is a 4-channel device designed for ion mobility. Further design features were built into the CTIA-5 such as differential noise reduction capabilities.The CTIA-1 technology was evaluated for use in isotope ratio mass spectrometry on a custom-built Mattauch-Herzog mass spectrometer. An evaluation was conducted in terms of the detector sensitivity, stability, accuracy, precision, resolution, and mass bias. The CTIA-2 was tested on a sector mass spectrometer for its response to low ion currents of both positive and negative ions. The detector stability, its accuracy, and its precision were studied.The technique of ion mobility spectrometry is rapidly growing, as it is the main technology used for the detection of explosives at security checkpoints. The need to improve the sensitivity of existing ion mobility instruments has led to the exploration of using the CTIA detector in ion mobility instruments. Improvements in sensitivity of two to three orders of magnitude have been demonstrated using the described CTIA detectors. Additional applications that use ion mobility instruments for the detection of analytes have been presented, the chemical mapping of a halogen-contaminated sand bed, the detection of pesticides, as well as the detection of TNT in drinking water.Results indicate that the CTIA detector technology is well suited for use in both mass spectrometry and ion mobility. The sensitive and stable multi-array CTIA detectors perform well in isotope ratio mass spectrometry. Ion mobility instruments of all types can benefit from the added sensitivity supplied by this technology.

L'experiment ATLAS al Laboratori Europeu de Física de Partícules (CERN), Ginebra, ha obtingut dades amb èxit des que el Gran Col·lisionador d'Hadrons (LHC en anglès) començà a ser operatiu el 2010. Des de llavors, ha estat generant col·lisions de protó-protó per estudiar les fronteres de la física de partícules, a una energia al centre de masses de, primer 7-8 TeV i més recentment de 13 TeV. Tot i això, l'experiment es troba en evolució constant: la degradació dels detectors a causa de la radiació, l'increment de la freqüència de les col·lisions i nous objectius científics sovint requereixen millores als detectors d'ATLAS. Aquests nous reptes motiven la continuada recerca i el desenvolupament de noves tecnologies de detectors. Per ampliar la recerca de física de partícules a l'experiment, la col·laboració d'ATLAS afegí recentment un detector "forward" per identificar protons emergits de col·lisions al LHC a angles petits. El detector de Protons Difractius d'ATLAS (o AFP, de l'anglès "ATLAS Forward Proton") capacita la identificació de processos difractius i esdeveniments centrals exclusius, permetent per exemple la cerca de noves ressonàncies pesades en esdeveniment nets. L'AFP consisteix en detectors de traces de silici instal·lats a poca distància del feix de protons del LHC i a ~210 m del punt d'interacció a cada costat d'ATLAS, juntament amb detectors de temps de vol per reduir senyals de fons produïts per l'acumulació de col·lisions. Els detectors de silici han de demostrar la suficient resistència a la radiació, una bona resolució espacial i els requeriments d'àrea activa necessaris per AFP. La tecnologia de sensors de píxels 3D, primerament utilitzada en el detector IBL d'ATLAS, ha sigut desenvolupat i qualificat per AFP. El “detector AFP d'un braç”, en el qual aquesta tesi està basada, es refereix a l'etapa en la qual el detector AFP consistia només de detectors de traces de silici en un dels costats d'ATLAS, que va ser instal·lat a principis de 2016. La instal·lació es va completar un any després, quan tant els detectors de traces com els de temps de vol es van instal·lar als dos costats d'ATLAS. Aquesta tesi descriu el procés complet de caracterització de la tecnologia del detector de traces de silici, producció, instal·lació i anàlisi de dades del detector AFP en la seva primera etapa.
The ATLAS experiment at the European Laboratory for Particle Physics (CERN), Geneva, has been taking data successfully since the Large Hadron Collider (LHC) accelerator started operations in 2010. Since then, it has been generating proton-proton collisions to study the frontiers of particle physics, at a centre of mass energy of 7-8 TeV first and, more recently, 13 TeV. However, the experiment is in constant evolution: detectors ageing due to radiation damage, increasing collision rates and pile-up, and new scientific objectives often require upgrades of the ATLAS detectors. These ever-growing challenges motivate the continued research and development of new detector technologies. To enhance the physics search of the experiment the ATLAS collaboration recently added a forward detector to identify intact protons that emerge from LHC collisions at very shallow angles. The ATLAS Forward Proton (AFP) detector enables the identification of diffractive processes and, ultimately, of central exclusive events, thus allowing, for example, the search of new heavy resonances in clean events. AFP consists of silicon trackers installed very close to the LHC proton beam and at ~210 m from the interaction point (IP) at each side of ATLAS, in addition to Time-of-Flight detectors for pile-up removal. AFP needs the silicon tracker to fulfil challenging radiation hardness, spatial resolution and active area requirements. The novel 3D pixel sensor technology, first employed in the ATLAS Insertable B-Layer, was further developed and qualified for AFP. The “one-armed AFP detector”, on which this thesis is focused, refers to the stage in which the AFP detector consisted only of silicon trackers in one side of ATLAS, installed at the beginning of 2016. The full installation was successfully finished one year later, when both silicon trackers and Time-of-Flight detectors were installed in both sides of ATLAS. This thesis describes the full process of technology characterization of the silicon tracker, production, installation, operation and particle physics data analysis of the one-armed AFP detector.

In the last decade, neutron detection has been attracting the attention of the scientific community for different reasons. On one side, the increase in the price of 3He, employed in the most efficient and the most widely used neutron detectors. On the other side, the harmfulness of traditional xylene based liquid scintillators, used in extremely large volumes for the detection of fast neutrons. Finally, the demand for most compact and rough systems pushed by the increased popularity of neutron imaging, neutron scattering and neutron diffraction techniques. Polysiloxanes could help addressing some of the existing issues regarding neutron detection thanks to their unique properties. For this reason, in this work, polysiloxane scintillators have been developed and characterized, with a special attention to their optical properties and their time response. In particular, this thesis describes the investigation of the scintillation performances of several different polysiloxane liquids. The results have been connected with the optical properties of the material, in turns linked to its molecular structure, allowing to select the most suitable polysiloxane solvent for liquid scintillators. The timing properties of scintillating mixtures employing the best performing polysiloxane solvent were consequently analyzed as a function of the primary dye concentration, with a special focus to the pulse shape discrimination (PSD) capability of the material. PSD is indeed one of the most important characteristic of liquid scintillators, and one of the factors determining their large use. Beside polysiloxane liquids, time response of polysiloxane plastic scintillators was also investigated with the aim of studying their PSD capability. At the moment, indeed, only few examples of plastic scintillators capable of PSD exist, and also in those cases some criticalities emerged connected with stability issues and efficiency. Production of red emitting polysiloxane plastic scintillators is also described in this work, analyzing the energy transfer process between dyes in order to optimize the readout with an avalanche photodiode. This would allow overcoming some issues connected with the use of photomultiplier tubes, in more compact and rugged systems. Finally some preliminary results about the HYDE experiment are presented. This project aims at the development of a hybrid detector for neutrons, combining a 3D silicon diode with a suitable neutron converter, in order to produce a compact efficient neutron detector with good spatial resolution. With this goal different types of converters for fast and thermal neutrons were tested and the performances of 3D and planar devices were compared.

In the last decade, neutron detection has been attracting the attention of the scientific community for different reasons. On one side, the increase in the price of 3He, employed in the most efficient and the most widely used neutron detectors. On the other side, the harmfulness of traditional xylene based liquid scintillators, used in extremely large volumes for the detection of fast neutrons. Finally, the demand for most compact and rough systems pushed by the increased popularity of neutron imaging, neutron scattering and neutron diffraction techniques. Polysiloxanes could help addressing some of the existing issues regarding neutron detection thanks to their unique properties. For this reason, in this work, polysiloxane scintillators have been developed and characterized, with a special attention to their optical properties and their time response. In particular, this thesis describes the investigation of the scintillation performances of several different polysiloxane liquids. The results have been connected with the optical properties of the material, in turns linked to its molecular structure, allowing to select the most suitable polysiloxane solvent for liquid scintillators. The timing properties of scintillating mixtures employing the best performing polysiloxane solvent were consequently analyzed as a function of the primary dye concentration, with a special focus to the pulse shape discrimination (PSD) capability of the material. PSD is indeed one of the most important characteristic of liquid scintillators, and one of the factors determining their large use. Beside polysiloxane liquids, time response of polysiloxane plastic scintillators was also investigated with the aim of studying their PSD capability. At the moment, indeed, only few examples of plastic scintillators capable of PSD exist, and also in those cases some criticalities emerged connected with stability issues and efficiency. Production of red emitting polysiloxane plastic scintillators is also described in this work, analyzing the energy transfer process between dyes in order to optimize the readout with an avalanche photodiode. This would allow overcoming some issues connected with the use of photomultiplier tubes, in more compact and rugged systems. Finally some preliminary results about the HYDE experiment are presented. This project aims at the development of a hybrid detector for neutrons, combining a 3D silicon diode with a suitable neutron converter, in order to produce a compact efficient neutron detector with good spatial resolution. With this goal different types of converters for fast and thermal neutrons were tested and the performances of 3D and planar devices were compared.

GEMs (Gas Electron Multiplier) and Thick-GEMs (Thick-Gas Electron Multiplier) are MPGDs (Micropattern Gas Detector) that make part of the new generation of gaseous detectors, allowing high counting rates, low cost when compared to solid state detectors, high radiation hardness and gain when using multiple structures. Besides that, the handling and maintenance of these detectors is relatively simple, being versatile to detect different types of radiation. Therefore, these detectors are an effective alternative to build imaging systems with large sensitive area. This work consists in the study and characterization of a set of gaseous detectors, more specifically the Thick-GEMs produced in the High Energy Physics and Instrumentation Center at IFUSP, which were tested showing promising results in terms of gain, energy resolution and operational stability. However, due to the low signal-to-noise ratio of the Thick-GEMs, the X-ray fluorescence imaging system was mounted using GEMs. During this work the necessary software tools for image processing and reconstruction were developed as a parallel study in computational simulations to better understand the operation of gaseous detectors. X-ray fluorescence techniques are essential in areas such as medicine and the study of historical and cultural heritage since they are non-invasive and non-destructive. Techniques to check the authenticity of masterpieces are required and museums are gradually becoming more interested in the Physics and instrumentation needed to characterize their patrimony.
Os GEMs (Gas Electron Multiplier) e Thick-GEMs (Thick-Gas Electron Multiplier) são estruturas do tipo MPGD (Micropattern Gas Detector) que fazem parte da nova geração de detectores de radiação a gás e permitem altas taxas de contagens, baixo custo quando comparados com os detectores de estado sólido, uma elevada resistência à radiação e ganhos elevados, quando utilizadas estruturas múltiplas para multiplicação. Além disso, o manuseio e manutenção desses detectores é relativamente simples, sendo versáteis em relação à montagem podendo detectar diferentes tipos de radiação. Sendo assim, a utilização desses detectores é uma alternativa eficiente para montar um sistema de imagem com grande área sensível. Este trabalho consiste no estudo e caracterização de um conjunto de detectores gasosos, mais especificamente os Thick-GEMs produzidos pelo grupo de Física de altas energias e Instrumentação do IFUSP, que foram testados para serem empregados em um sistema de imagem de fluorescência de raios-X. Os Thick-GEMs testados apresentaram resultados promissores em termos de ganho, resolução em energia e estabilidade operacional. No entanto, devido à baixa relação sinal-ruído, um sistema de imagem de fluorescência de raios-X foi montado utilizando GEMs. Durante o trabalho as ferramentas de software necessárias para processamento e reconstrução de imagens foram desenvolvidas, assim como um estudo paralelo de simulações computacionais para entender melhor o funcionamento de detectores gasosos. Técnicas como o imageamento por fluorescência de raios-X são de suma importância pois são consideradas não invasivas e não destrutivas. Sua utilização tem uma importância imprescindível nas áreas da medicina e na análise de patrimônios histórico e cultural. Atualmente, a verificação e validação de autenticidade de obras é um requisito obrigatório e alguns museus começam a se interessar cada vez mais em áreas da Física e da instrumentação necessária para caracterizar o seu patrimônio.

L’Organització Europea per a la Investigació Nuclear (CERN) està implementant actualment una important actualització del Gran Col·lisionador d’Hadrons (LHC) de 27 quilòmetres, amb l’objectiu d’expandir l’abast de la física, augmentant la lluminositat i desencadenant la consegüent multiplicació d’interaccions per feix de partícules. Les noves condicions operatives de l’LHC d’alta lluminositat (HL-LHC) tindran un impacte directe en els sensors de traçat de silici dels detectors principals, els experiments ATLAS i CMS, causant un gran augment de l’ocupació dels sensors i danys per radiació. Aquesta tesi doctoral investiga el disseny i l’optimització d’una nova generació de detectors de micropistes de silici capaços de suportar les severes condicions operatives esperades per a l’actualització HL-LHC. En primer lloc, l’estudi aborda el desenvolupament dels detectors de micropistes de silici des del punt de vista del disseny. Es presenten elements bàsics del dispositiu i es discuteix el seu disseny en base a consideracions de rendiment. Es presenta una nova eina de generació de disseny automàtic (ALGT) basada en Python, amb l’objectiu d’abordar la necessitat de prototips de detectors de micropistes de grans dimensions en les etapes d’I+D de l’actualització del traçador intern (ITk) d’ATLAS. El ALGT s’utilitza per dissenyar un prototip de sensor de micropistes de grans dimensions, diversos sensors en miniatura i díodes. Aquests dispositius es generen i s’organitzen en un disseny d’oblea complet de 6 polzades, per a la participació d’Infineon Technologies AG en l’enquesta de mercat per a la fabricació de sensors de micropistes per al ITk d’ATLAS. A més, es presenten dissenys d’una àmplia gamma d’estructures de test microelectròniques amb diferents aplicacions. Es proposa un conjunt d’estructures de test per al desenvolupament de tecnologies de micropistes, juntament amb un xip de test capaç de cobrir tots els tests planificats per al control de qualitat (QA) durant la producció dels sensors de micropistes d’ATLAS. D’altra banda, per millorar la connexió de lectura, també es proposen diversos dissenys d’adaptadors de “”pitch”” integrats (EPA) per minimitzar els possibles inconvenients associats amb la introducció d’una segona capa de metall en l’estructura del sensor. Es realitza una caracterització extensa en el marc de l’enquesta de mercat dels sensors de micropistes per l’ATLAS ITk. Els dispositius fabricats per les empreses candidates, Infineon Technologies AG i Hamamatsu Photonics K.K., s’avaluen abans i després d’irradiacions amb protons, neutrons i gammes, fins a les influències esperades a la fi de la vida útil de l’HL-LHC. Les estructures de test i els xips de test per QA dissenyats també es caracteritzen, amb l’objectiu de validar el seu disseny, ampliar l’avaluació de la tecnologia de micropistes i proporcionar valors de referència per als tests de producció d’ATLAS. Es presenten estudis i desenvolupaments addicionals amb aplicació en experiments de física d’altes energies (HEP) en general. Temes candents, com la sensibilitat a la humitat dels sensors de grans dimensions o l’efectivitat del “”punch-through protection”” en un escenari de pèrdua de feix, s’investiguen àmpliament. També es mostra un estudi complet de les noves estructures d’EPA proposades i els resultats dels primers sensors de micropistes fabricats en oblees de 6 polzades al Centro Nacional de Microelectrónica (IMB-CNM). Els dissenys i les caracteritzacions presentades contribueixen a definir el disseny final dels sensors de micropistes d’ATLAS per a l’actualització HL-LHC, i les investigacions addicionals revelen conclusions d’interès general que poden establir les bases per a futurs desenvolupaments.
La Organización Europea para la Investigación Nuclear (CERN) está implementando actualmente una importante actualización del Gran Colisionador de Hadrones (LHC) de 27 kilómetros, con el objetivo de expandir el alcance de la física, aumentando la luminosidad y desencadenando la consiguiente multiplicación de interacciones por haz de partículas. Las nuevas condiciones operativas del LHC de alta luminosidad (HL-LHC) tendrán un impacto directo en los sensores de trazado de silicio de los detectores principales, los experimentos ATLAS y CMS, causando un gran aumento de la ocupación del detector y daños por radiación. Esta tesis doctoral investiga el diseño y la optimización de una nueva generación de detectores de micropistas de silicio capaces de soportar las severas condiciones operativas esperadas para la actualización HL-LHC. En primer lugar, el estudio aborda el desarrollo de los detectores de micropistas de silicio desde el punto de vista del diseño. Se presentan elementos básicos del dispositivo y se discute su diseño en base a consideraciones de rendimiento. Se presenta una nueva herramienta de generación de diseño automático (ALGT) basada en Python, con el objetivo de abordar la necesidad de prototipos de detectores de micropistas de gran tamaño en las etapas de I + D de la actualización del trazador interno (ITk) de ATLAS. El ALGT se utiliza para diseñar un prototipo de sensor de micropistas de gran tamaño, varios sensores en miniatura y diodos. Estos dispositivos se generan y se organizan en un diseño de oblea completo de 6 pulgadas, para la participación de Infineon Technologies AG en la encuesta de mercado para la fabricación de sensores de micropistas para el ITk de ATLAS. Además, se presentan diseños de una amplia gama de estructuras de test microelectrónicas con diferentes aplicaciones. Se propone un conjunto de estructuras de test para el desarrollo de tecnologías de micropistas, junto con un chip de test capaz de cubrir todos los tests planificados para el Quality Assurance (QA) durante la producción de los sensores de micropistas de ATLAS. Por otro lado, para mejorar la conexión de lectura, también se proponen varios diseños de adaptadores de “pitch” integrados (EPA) para minimizar los posibles inconvenientes asociados con la introducción de una segunda capa de metal en la estructura del sensor. Se realiza una caracterización extensa en el marco de la encuesta de mercado de los sensores de micropistas para ATLAS ITk. Los dispositivos fabricados por las empresas candidatas, Infineon Technologies AG y Hamamatsu Photonics K.K., se evalúan antes y después de irradiaciones con protones, neutrones y gammas, hasta las fluencias esperadas al final de la vida útil del HL-LHC. Las estructuras de test y los chips de test para QA diseñados también se caracterizan, con el objetivo de validar su diseño, ampliar la evaluación de la tecnología de micropistas y proporcionar valores de referencia para los tests de producción de ATLAS. Se presentan estudios y desarrollos adicionales con aplicación en experimentos de física de altas energías (HEP) en general. Temas candentes, como la sensibilidad a la humedad de los sensores de gran tamaño o la efectividad del “punch-through protection” en un escenario de pérdida de haz, se investigan ampliamente. También se muestra un estudio completo de las nuevas estructuras de EPA propuestas y los resultados de los primeros sensores de micropistas fabricados en obleas de 6 pulgadas en el Centro Nacional de Microelectrónica (IMB-CNM). Los diseños y las caracterizaciones presentadas contribuyen a definir el diseño final de los sensores de micropistas de ATLAS para la actualización HL-LHC, y las investigaciones adicionales revelan conclusiones de interés general que pueden sentar las bases para futuros desarrollos.
The European Organization for Nuclear Research (CERN) is currently implementing a major upgrade of the 27-kilometre Large Hadron Collider (LHC), with the aim to expand the physics reach, increasing the luminosity and triggering the consequent multiplication of interactions per bunch crossing. The new High-Luminosity LHC (HL-LHC) operational conditions will have a direct impact in the silicon tracking sensors of the main detectors, the ATLAS and CMS experiments, causing a large increase of detector occupancy and radiation damage. This PhD thesis investigates the design and optimization of a new generation of silicon strip detectors able to withstand the severe operational conditions expected for the HL-LHC upgrade. Firstly, the study tackles the development of the silicon strip detectors from a layout design point of view. Basic device elements are presented and its design is discussed based on performance considerations. A new python-based Automatic Layout Generation Tool (ALGT) is presented, with the aim to address the need for large area prototypes of strip detectors at the R&D stages of the ATLAS Inner-Tracker (ITk) upgrade. The ALGT is used to design a large area strip sensor prototype, several miniature sensors and diodes. These devices are generated, and arranged in a full 6-inch wafer layout design, for the participation of Infineon Technologies AG in the ATLAS ITk strip sensor Market Survey. In addition, layout designs of a wide range of microelectronic test structures with different applications are presented. A set of test structures for the development of strip technologies is proposed, along with a test chip able to cover all the routine tests planned for the Quality Assurance (QA) works during the ATLAS strip sensor production. On the other hand, in order to improve the readout connection, several designs of Embedded Pitch Adaptors (EPA) are also proposed to minimize the possible drawbacks associated to the introduction of a second metal layer on the sensor structure. An extensive characterization is performed in the frame of the ATLAS ITk strip sensor Market Survey. Devices fabricated by the candidate foundries, Infineon Technologies AG and Hamamatsu Photonics K.K., are evaluated before and after proton, neutron and gamma irradiations, up to fluences expected at the end of the HL-LHC lifetime. Test structures and QA test chips designed are also characterized, with the objective to validate its design, expand the technology evaluation and provide reference values for the ATLAS production tests. Additional studies and developments are presented with application in High Energy Physics (HEP) experiments in general. Hot topics, such as the humidity sensitivity of large area sensors or the effectiveness of the punch-through protection in a beam-loss scenario, are extensively investigated. A complete study of the new EPA structures proposed, and results of the first strip sensors fabricated in 6-inch wafers at Centro Nacional de Microelectrónica (IMB-CNM), are also shown. The layout designs and characterizations presented, contribute to define the final design of the ATLAS strip sensors for the HL-LHC upgrade, and the additional investigations reveal conclusions of general interest that can lay the foundation for future developments.

La investigación presentada está centrada en la mejora de sensores de gas conductométricos de Sn02. Se analizan sensores en capa gruesa y en capa delgada. En el primer caso, el polvo de Sn02 necesario para fabricar los sensores ha sido elaborado mediante la técnica de sol-gel. Tras la obtención de un precursor (Sn02 hidratado), se han realizado estudios de calcinación, introducción de aditivos metálicos (Pt, Pd) y, por primera vez, un molido del material. Gracias a la disponibilidad de nanopartículas con tamaño de grano entre 3 y 100 nm, se ha podido analizar por primera vez el espectro Raman completo de nanoparticulas de Sn02, a partir el cual se presentan tres metodos diferentes para determinar de forma no destructiva el tamaño de grano medio y la distribución de tamaños de partícula en un sensor. Del estudio del molido del material de deduce que a través de éste se puede controlar la microestructura de las nanopartículas, asi como el estado de su superficie, permitiendo un control de la resistencia de base de los sensores y una mejora de su selectividad. Los sensores en capa delgada se han fabricado mediante las técnicas IBAD i RGTO, en crecimiento mono y multicapa. Se presenta en el trabajo un estudio detallado del depósito de Sn y de su oxidacón termica, extrayéndose de la investigación de los parámetros de la difusión del O en el Sn, así como las diferentes fases intermedias en la conversión de Sn a Sn02. Mediante el método RGTO multicapa se consigue reducir el tiempo de oxidación, así como mejorar la sensitividad de los sensores.

Thesis (M.S. in Applied Physics and M.S. in Electrical Engineering)--Naval Postgraduate School, June 2005.
Thesis Advisor(s): Gamani Karunasiri, James Luscombe, Robert Hutchins, John Powers. Includes bibliographical references (p. 129-131). Also available online.

Este trabalho propõe um método biotelemétrico para a determinação simultânea de duas características elétricas (moduláveis por parâmetros fisiológicos) de circuitos RLC passivos para microsensores injetáveis. Como o ambiente sob monitoração envolve a presença de íons (tecidos biológicos), a utilização de dipolos torna-se inviável, desta forma, o estabelecimento de um acoplamento indutivo entre o sensor e o dispositivo para o registro das medidas é necessário. Tratando-se de um dispositivo injetável, as dimensões da bobina do sensor são diminutas (diâmetro da ordem de mm), sugerindo cuidados especiais quanto ao acoplamento indutivo do circuito RLC com o dispositivo de registro das medidas. Desta forma, foi desenvolvido um detector digital de freqüências, associado a um conjunto otimizado de bobinas para obter, a determinada distância (5 mm), a melhor indutância mútua possível com o microcircuito RLC remoto. Este dispositivo monitora o sensor em tempo real, informando a freqüência de ressonância, a sua respectiva amplitude a partir de uma varredura em freqüência. Um estudo analítico modelando a resposta em tensão do circuito detector segundo os estímulos e respostas que este fornece e recebe do circuito RLC remoto foi desenvolvido. O resultado desta análise, verificada praticamente, possibilitou a identificação da constante de tempo que cada degrau de freqüência deve ser mantido no sensor para que a resposta indicada seja a mais precisa possível. Decorrente desta análise foi possível modelar teoricamente a resistência total que o circuito RLC remoto apresenta. Assim, a partir das medidas de freqüência e amplitude do detector e do modelo teórico da resistência total do sensor o método foi estabelecido. Para verificar na prática a validade do método um micro sensor (2,8 x 23 mm) foi desenvolvido. O sensor foi encapsulado dentro de um tubo de silicone, apresentando um indutor montado junto a um bastão de ferrite, um capacitor SMD e um NTC, todos associados em paralelo. Com a alteração da distância entre o bastão de ferrite e o indutor (através da tração do tubo de silicone) a freqüência do sensor é alterada e a variação da resistência do NTC, através da temperatura, altera o fator de qualidade do sensor. A utilização do método para monitorar o sensor apresentou erros inferiores a 0,57 % para a indicação da freqüência e 0,77 % para a indicação da temperatura. A influência medida da variação da temperatura sobre a indicação da freqüência foi inferior a 0,16 %, indicando que o método é viável.
This work proposes a biotelemetric method to determine simultaneously two electrical characteristics (modulated by physiological parameters) from a passive injectable RLC microcircuit. Due to the presence of free ions inside the biological tissue, inductive links (loop antennas) must be employed, instead of dipole antennas. As the coil of the sensor presents small dimensions (diameter of about mm) its magnetic coupling to the monitoring device requires special attention. To monitor the sensor, a digital device assembled with a group of coils to maximize the mutual inductance (at a distance of 5 mm) between them was developed, detecting its resonance frequencies and the respective amplitude (through a frequency sweep) in real-time. The electrical response acquired by the detector from the sensor was analytically modeled. The model indicates a time constant to consider for each change of the signal frequencies to prevent errors in the response. From that theoretical model, an equation to determine the total resistance from the RLC circuit was obtained and confirmed by experiments. Then, a method to determine the resonance frequency and the total resistance from remote RLC circuit was proposed. A sensor was developed to verify the accuracy and the limits from this method. A parallel RLC circuit was built inside a silicone rubber tube. When the tube is stretched, a ferrite rod assembled beside the inductor is displaced varying the resonance frequency and, changing the environmental temperature, a NTC varies the quality factor of the circuit. Tests using the proposed method to monitor the sensor were realized. Errors small than 0.57 % in the resonance frequencies and 0.77 % in the temperature were obtained. The measured influence of the temperature variation over frequency determination was less than 0.16 %, indicating that the method is feasible.

Thesis (M.S. in Applied Physics)--Naval Postgraduate School, June 2006.
Thesis Advisor(s): Gamani Karunasiri, James H. Luscombe. "June 2006." Includes bibliographical references (p. 49-50). Also available in print.

The lack of passive, wireless, chemical and biological sensor systems is a significant impediment to sensor system applications. While active sensors with a wireless communications link continue to decrease in power consumption, they still require a power source, such as a battery. This active power consumption limits the useful life of the sensor and its applications. A more attractive solution would be a passive, wireless, chemical and biological sensor integrated with a wireless interrogation platform to monitor the sensor. The focus of this thesis is the realization of a wireless sensor interrogator capable of monitoring multiple, passive, resonant-frequency sensors. It is demonstrated, using Frequency Modulation Spectroscopy techniques, that the resonant frequency of a passive sensor can be detected and tracked over time. Simulated results are presented that verify the functionality of the proposed wireless sensor interrogator. In addition, an experimental hardware setup and subsequent experimental results are presented that verify the simulation results. Considerations for the design of the wireless sensor interrogator and opportunities for future research are discussed.

Near infrared (NIR) light detection has drawn substantial attentions in a variety of applications. NIR detectors prepared by the solution processable organic semiconductors and organic-inorganic hybrid material systems have the advantages for achieving flexible, light weight and large area NIR detection devices. The aim of this research work is to study the modulation of the photo-generated charge carriers in perovskite and polymer systems for attaining high performing solution-processable NIR phototransistors (PTs) and photodiodes (PDs). In the first part, an organo-lead halide perovskite/polymer bi-layer channel PT is discussed. Compared to the performance of the polymer only PTs, the PTs with a perovskite/polymer hybrid channel exhibit a profound broadband enhancement in photoresponsivity over the light wavelength range from UV to NIR. The improved performance in the hybrid perovskite/polymer PTs is closely associated with the efficient charge separation and transfer between the perovskite and polymer functional layers in the heterojunction. With the success in developing the bi-layer perovskite/polymer PTs, the enhancement in NIR detection is further realized in PTs by incorporating a bulk heterojunction (BHJ) channel. The BHJ channel is formed by blending NIR sensitive polymer donor with three different acceptor materials for enhancing exciton dissociation and charge separation efficiency. It is shown that the use of donor/acceptor BHJ greatly facilitates the dissociation of photo generated excitons. The efficient exciton dissociation helps to boost the utilization of the photo generated excitons, and thereby improves the photoresponsivity. Although the PTs with a BHJ channel possess high photoresponsivity, the photosensitivity of these NIR PTs is still less than satisfactory. The results reveal that a higher activation energy of charge carriers is favorable for a lower carrier density in the channel. While under NIR light illumination, the mobile charge carriers, created due to the dissociation of the photo generated excitons, result in a dramatic increase in carrier density in the active channel. The increase in carrier density under NIR illumination, gives rise to a higher channel current, thereby a higher photosensitivity. A pixel-less NIR imaging device based on light up-conversion from near-infrared to green is demonstrated. A polymer donor/non-fullerene acceptor BHJ serving as the NIR sensitive unit is integrated monolithically with a perovskite-based light emitting diode (LED) unit for achieving light up-conversion from NIR to visible light. The BHJ serves as an NIR sensitive hole injection layer in the perovskite LEDs. Therefore, the efficient electroluminescence in area where NIR-induced efficient charge injection occurs in the LEDs can be displayed clearly, producing the visible light image. The photoresponsivity of perovskite based UV-Visible-NIR photodiodes (PDs) is discussed in the last part of the thesis. A periodic nano-grating hole transporting layer (HTL), formed by the nano-imprinting, is adopted for enhancing the photoresponsivity of the PDs. Theoretical simulation reveals that the periodic nano-grating HTL helps to improve light absorption in the active layer, caused by the enhanced light in-coupling effect. In the meantime, the nano-grating HTL based PDs exhibit weak angular dependency as compared to that of the planar control ones which is appealing for wide angle light detections.

Thesis (M.S. in Applied Physics)--Naval Postgraduate School, Dec. 2004.
Thesis Advisor(s): Nancy M. Haegel, Gamani Karunasiri. Includes bibliographical references (p. 43-45). Also available online.