39 research outputs found
Plasmonics-integrated Ge PIN-photodetectors
No full textRefractive index sensors can be designed for high sensitivities at small device foot-print. Using a complementary metal-oxide-semiconductor compatible process for fabrication paves the way to cheap devices enabling integrated biosensors. We present results on combining vertical Ge PIN photodetectors with metallic nanostructures such as Al nanohole arrays placed directly on top of the diode. The interaction of plasmonic resonances and photonic modes such as waveguide modes or optical modes in nanostructured photodetectors can potentially be exploited to design refractive index sensors with very high sensitivities. We discuss how the interplay of material properties and device geometry can be tailored for applications in integrated biosensing
Optofluidic sensor system with Ge PIN photodetector for CMOS-compatible sensing
No full textVertical optofluidic biosensors based on refractive index sensing promise highest sensitivities at smallest area footprint. Nevertheless, when it comes to large-scale fabrication and application of such sensors, cheap and robust platforms for sample preparation and supply are needed—not to mention the expected ease of use in application. We present an optofluidic sensor system using a cyclic olefin copolymer microfluidic chip as carrier and feeding supply for a complementary metal–oxide–semiconductor compatibly fabricated Ge PIN photodetector. Whereas typically only passive components of a sensor are located within the microfluidic channel, here the active device is directly exposed to the fluid, enabling top-illumination. The capability for detecting different refractive indices was verified by different fluids with subsequent recording of the optical responsivity. All components excel in their capability to be transferred to large-scale fabrication and further integration of microfluidic and sensing systems. The photodetector itself is intended to serve as a platform for further sophisticated collinear sensing approaches
Optical characterization of highly n-type doped Ge0.95Sn0.05 rod antennas on Si(001) substrates
No full textPlasmonic excitations in metal nanostructures can be used to control and manipulate optical energy in the visible and infrared spectrum and have been used to enable biosensing, to enhance absorption and quantum yields for photovoltaics and to enhance the energy efficiency of light-emitting devices. For light at mid-infrared (MIR) wavelengths, metals become less suitable for plasmonic applications as a result of the high Drude losses. At those wavelengths, highly doped semiconductors are potential alternatives. The doped group IV alloy Ge x Sn y has been shown to be particularly interesting. We present results on the fabrication and optical characterization of rod antennas fabricated from highly n-type doped Ge 0.95 Sn 0.05 (n-Ge x Sn y ) on Si(001) substrates. Extinction spectra were obtained via Fourier Transform Infrared (FTIR) Spectroscopy. To verify the measurement results the behavior of the n-Ge 0.95 Sn 0.05 rod antennas was simulated. The results show that the n-Ge 0.95 Sn 0.05 rod antennas absorb MIR radiation through plasmonic excitation. Two different peaks could be observed in the extinction spectra of the n-Ge 0.95 Sn 0.05 rod antennas and attributed to two locally separated plasmonic modes. One mode forms on the n-Ge 0.95 Sn 0.05 /Si interface of the n-Ge 0.95 Sn 0.05 rod antennas, the other one forms at the n-Ge 0.95 Sn 0.05 /air interface. We discuss possible applications of this type of n-Ge 0.95 Sn 0.05 rod antennas for MIR sensing
Ge(Sn) nano-island/Si heterostructure photodetectors with plasmonic antennas
No full textWe report on photodetection in deep subwavelength Ge(Sn) nano-islands on Si nano-pillar substrates, in which self-aligned nano-antennas in the Al contact metal are used to enhance light absorption by means of local surface plasmon resonances. The impact of parameters such as substrate doping and device geometry on the measured responsivities are investigated and our experimental results are supported by simulations of the three-dimensional distribution of the electromagnetic fields. Comparatively high optical responsivities of about 0.1 A W-1 are observed as a consequence of the excitation of localized surface plasmons, making our nano-island photodetectors interesting for applications in which size reduction is essential
Growth and Characterization of SiGeSn Quantum Well Photodiodes
No full textWe report on the fabrication and electro-optical characterization of SiGeSn multi-quantum well PIN diodes. Two types of PIN diodes, in which two and four quantum wells with well and barrier thicknesses of 10 nm each are sandwiched between B- and Sb-doped Ge-regions, were fabricated as single-mesa devices, using a low-temperature fabrication process. We discuss measurements of the diode characteristics, optical responsivity and room-temperature electroluminescence and compare with theoretical predictions from band structure calculations
A interferência do Banco Mundial na Guiné-Bissau: a dimensão da educação básica - 1980 - 2005
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Filosofia e Ciências Humanas, Programa de Pós-Graduação em Sociologia Política, Florianópolis, 2009Na Guiné-Bissau a questão da educação é muito preocupante. Preocupação esta que se estende a partir da educação básica. Esta pesquisa analisou a interferência do Banco Mundial na Guiné-Bissau na dimensão da educação básica no período de 1980 a 2005. A questão principal que norteou a pesquisa relaciona-se com a atuação do Banco Mundial no ensino básico guineense, através do seu projeto denominado firkidja. Uma das questões cruciais seria: quais são seus os efeitos sobre a educação e especificamente sobre "o ensino de base" na Guiné-Bissau, decorrente dos acordos internacionais? Ocorreram mudanças de diretrizes na educação? Os acordos internacionais oferecem alternativas efetivas, em termos de indicadores, para o "ensino de base"? Foram também analisadas questões relacionadas à influência do Banco Mundial nas políticas educativas da Guiné-Bissau, que em muitos casos embute condicionalidades aos Estados. Uma vez que a Guiné-Bissau depende totalmente de "ajuda externa", comprometendo a ação estatal com as políticas do Banco Mundial, a soberania guineense sofre abalos e termina por submeter-se aos desenhos tecnocráticos propostos pela instituição financeira, aqui, em particular, no que tange à educação básica. Para abordar essa problemática, recorreu-se, como caminho metodológico, à pesquisa bibliográfica como passo inicial para o levantamento de referência bibliográfica. Cumprida essa etapa e de posse de uma listagem minimamente suficiente de trabalhos relacionados ao tema, estabeleceram-se leituras que seriam de interesse para aplicar-lhes a análise de discurso como meio viável. Para obter esse resultado, fez-se necessário analisar os documentos do Banco Mundial, bem como os do Estado da Guiné-Bissau. Três modelos de ensino foram aí elencados: ensino colonial português, ensino das zonas libertadas e ensino pós-colonial. A pesquisa passou ainda em revista o contexto sociológico do continente africano e a perspectiva da África na colonialidade do saber. A ausência e o silêncio do Continente nos clássicos das Ciências Sociais não passaram despercebidos. A abordagem dessa peculiaridade meandra o texto como um todo; ao menos à pequena parte que coube a este esforço analítico, o silêncio foi rompido.In Guinea Bissau the question of education is alarming, a problem which extends from the basic education. This research analysed the interference of the World Bank in Guinea Bissau in the dimension of basic education in the period of 1980 to 2005. The principal question which led to the research is related to the action of the World Bank on the Guinean basic teaching, through its project called firkidja. One of the crucial questions would be: what are the effects on education and especially on "basic education" in the Guinea-Bissau as a consequence of international accords? Did changes occur in the educational policies? Do the international accords offer effective alternatives, in terms of indicators, for the "Basic Education"? Questions were also analysed in relation to the influence of the World Bank in the educational policies of Guinea-Bissau, which in a lot of cases is embedded in the conditionalities of the States. Since Guinea-Bissau depends entirely on "external help", compromising the state-owned action with the policies of the World Bank, the Guinean sovereignty suffers concussions and ends in submission to technocratic plans proposed by the financial institution, which in this case, sounds as basic education. To tackle this problem in a methodological way, bibliographic research was resorted to as the initial step for the survey of bibliographic reference. After accomplishing this stage and taking possession of a minimum list of sufficient projects related to the topic, lections of interest were established to apply them to the analysis of discourse as a viable way. To obtain this result, it was necessary to analyse the documents of the World Bank as well as those of the State of Guinea-Bissau. Three models of education were then enumerated: colonial Portuguese education, liberated Zone Education and Post-colonial Education. The research also underwent a review in the sociological context of the African continent and the perspective of Africa in the coloniality of knowledge. The absence and silence of the continent in the classics of social sciences did not go unperceived. The approach of this peculiarity meander the text as a whole; at least with the small part which fits in this analytic effort, the silence was broken
Desenvolvimento sócio-econômico e dependência da Guiné-Bissau: caso do cajú
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Filosofia e Ciências Humanas, Programa de Pós-Graduação em Sociologia Política, Florianópolis, 2013.A dissertação analisa aspectos econômicos e sociopolíticos relacionados com o desenvolvimento da Guiné-Bissau, com foco principal nos processos de produção, transformação e comercialização da castanha do caju, principal produto na pauta de exportação do país. Além das políticas governamentais, são consideradas as condições sociais e econômicas dos diferentes produtores e comerciantes do produto. Ao mesmo tempo se avalia o relacionamento estabelecido pelos distintos governos do país com o Fundo Monetário Internacional e o Banco Mundial e as implicações dos programas desses organismos na manutenção do status quo relacionado com o universo do caju. Constatou-se a dependência e importância do caju na economia do país e na sobrevivência de grande parte da população, mas que a mesma não é maior beneficiária do processo e que o sistema produtivo carece de melhor infraestrutura, possui carência de transformação do produto, que é exportado basicamente in natura, desvalorização dos seus produtores e a falta de comprometimento do governo guineense face as suas responsabilidades com o setor e com o desenvolvimento de forma mais ampla. Os procedimentos metodológicos incluíram a pesquisa bibliográfica e documental além de pesquisa de campo realizada nas oito regiões do país (Cacheu, Bafatá, Gabú, Quínara, Tombali, Bolama, Oio) e o setor autônomo de Bissau durante o período de abril-junho de 2012. As entrevistas (total de 56) foram realizadas com agricultores, comerciantes e empresários envolvidos na produção e exportação do caju, além de autoridades governamentais, acadêmicos e membros de ONGs que atuam na área.Résumé : La thèse examine les aspects économiques et socio-politiques liés au développement de la Guinée-Bissau, avec un accent mis sur les procédés de production, de transformation et de commercialisation de la noix de cajou, principal produit d'exportation du pays. Outre les politiques gouvernementales, les conditions sociales et économiques des différents producteurs et distributeurs du produit sont considérés. De plus on évalue la relation établie par les différents gouvernements du pays avec le Fonds Monétaire International et la Banque Mondiale et les implications des programmes de ces organismes à maintenir le status quo relationné à l'univers de la noix de cajou. On a constaté la dépendance et l'importance de noix de cajou dans l'économie du pays et la survie de la majorité de la population, mais aussi que la population n'est pas la plus grande bénéficiaire du processus et que le système de production n'a pas de bonnes infrastructures, possède un manque de transformation du produit, qui est essentiellement exportée sans transformation, une dévaluation de leurs producteurs et le manque d'engagement du gouvernement guinéen face à leurs responsabilités avec l'industrie et avec le développement plus largement. Les procédures méthodologiques comprendrons la recherche bibliographique et documentaire ainsi que la recherche de terrain menée dans les huit régions du pays (Cacheu, Bafata, Gabu, Quinara, de Tombali, Bolama, Oio) et le Secteur Autonome de Bissau pour la période Avril-Juin 2012. Les entretiens (total de 56) ont été menées avec des agriculteurs, des commerçants et des hommes d'affaires impliqués dans la production et l'exportation de la noix de cajou ainsi que des représentants du gouvernement, des universitaires et des membres d'ONG travaillant dans le domaine
An integrated plasmonic refractive index sensor: Al nanohole arrays on Ge PIN photodiodes
No full textSimulation-based optimization of Ge-PIN-photodiodes with Al nanohole arrays for refractive index sensing
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