This dissertation presents two kinds of model extraction approaches, direct extraction and adaptive rational approximation methods, for establishing a novel broadband model, the modified T-equivalent circuit. Both methods skillfully use the simplified and decomposed schemes to dramatically reduce the complexity of modeled parameter extraction procedures and the needed computational efforts. As a result, any two-port microwave passive components or networks can be modeled efficiently using the proposed fully-analytical mathematic extraction formulations. In comparison with other broadband modeling techniques, the modified T-equivalent circuit can be constructed with much less elements. Model with such a compact character attributes the frequency responses of two decomposed circuits having obvious resonances to be identified and utilized for constituting equivalent circuits using only necessary elements. It is worth to note that the modified T-equivalent circuit model can utilize two expandable multilayer resonators to achieve very wide bandwidth but maintain model still in a single-stage equivalent circuit. Several successful modeling examples verified on the LTCC- and organic- embedded type of band-pass filters and inductors, the most crucial passive components to affect the performances of RF communication system, demonstrate the presented model with the superior character of accuracy and broadband indeed.

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Pulp and paper mills are being placed under increasing pressure to maximise the use of the biomass being processed for pulp, and move towards integrated biorefineries (IFBRs), where a diverse range of products can be produced and not just pulp exclusively. Extracting hemicelluloses prior to the pulping process could increase the profitability of the mills as the hemicelluloses could be used to produce a number of additional products. Hemicelluloses are a plant polysaccharides with the most abundant hemicellulose in hardwoods being xylan, with xylose being the primary monosaccharide constituent of xylan. The majority of pulps produced in the Southern Hemisphere are done with hardwoods as feedstock, typically with the Kraft process. The attraction of the concept of extracting hemicellulose prior to pulping is further augmented by the fact that hemicellulose is underutilised in the Kraft process. In the Kraft process the hemicellulose is dissolved during pulping and burned along with lignin for the production of energy, however, hemicellulose has about half the heating value when compared to that of lignin. The main objective of this study was to find a pre-extraction method that is effective in releasing xylan from Eucalyptus grandis, the most important hardwood feedstock used for pulping in the Southern Hemisphere. The method also needs to be practical in terms of integrating it into the Kraft process and should have a minimal effect on pulp yield and subsequent paper qualities. Xylan extractions from E. grandis as feedstock were carried out with white liquor, green liquor and NaOH. Green liquor is the dissolved smelt originating from the recovery boiler in the Kraft process and consists mainly sodium carbonate and sodium sulphide. White liquor’s principal components include sodium hydroxide and sodium sulphide and is used in the digesters during the pulping stage of the Kraft process. NaOH is a make up chemical used in the Kraft process. These chemicals were chosen since they are all already present within the Kraft process. The suitability of these chemicals as xylan extraction methods is further bolstered by the fact that their alkalinity may actually reduce chemical usage in pulping. This provides scope for integration of hemicellulose extraction into Kraft pulping without implementing major changes to the existing industrial process. Moreover, alkali chemicals for pre-extraction allow for minimal effect on resulting pulp and paper. In terms of the extracted product, the alkaline conditions provided by these chemicals create conditions that are suitable for a high degree of polymerisation of hemicelluloses. Xylan pre-extracted chips from selected extraction conditions were subjected to varying pulping conditions, to replicate pulp yields and properties obtained with untreated E. grandis chips when using conventional pulping. Handsheets were also produced from the pulps produced under the highest pulp yield conditions, and these were tested for pulp quality properties. Furthermore, mass balances were performed to gauge the impact that hemicellulose pre-extraction would have using green liquor, white liquor and NaOH on the sodium and sulphur balances of the mill. From the extractions performed, the highest fraction of xylan recovered was 15.15% w/w utilising 2M NaOH, at 120°C for 90 minutes extraction time. This was followed by white liquor extraction at 13.27% w/w utilising 20% AA at 140°C for 90 minutes. Green liquor extraction produced the lowest xylan recovery at 7.83% w/w with 2% TTA and 160°C with an h-factor of 800. The residues from selected extraction conditions were utilised for these pulping optimisation experiments. Selected extraction conditions used for further pulping included 2% TTA and 160°C for green liquor, 20% AA and 120°C and 140°C extraction temperature for white liquor, as well as 2M concentration and 120°C for NaOH. The highest yielding pulping conditions were achieved with a 35% reduction in pulping chemicals and 45 minutes pulping time in combination with green liquor pre-extraction, while for pulping combined with white liquor pre-extraction a 50% reduction in chemicals and 30 minute pulping time was preferred. For pulping subsequent to NaOH pre-extraction a 75% reduction in the NaOH dosage and a 45 minute pulp time was preferred. All pulp steps were performed at 170°C. Unbeaten handsheets produced from the selected pulping conditions for white liquor and green liquor extracted chips showed similar physical properties (burst, tear, tensile indices) when compared to the control (pulps from non-extracted chips). However the greater quantity of xylan removed from cellulose fibres with NaOH extraction, resulted in pulps with lower xylan contents, which affected the burst and tear indices of the handsheets formed from these pulps. An increase in tear, while a reduction in the burst index, was observed for the pulp produced from NaOH extracted chips. It was concluded that although white liquor and NaOH extraction allows for greater xylan recovery, the large chemical expenditure associated with these methods will impose significant cost impacts on the existing Kraft process. From mass balances performed, green liquor xylan extraction due to its lower alkalinity, will be more forgiving in terms of additional make up chemical costs. It also allowed for minimum effect on both the pulp and paper quality, thus making it the most practical of the pre-extraction methods. However, whether the additional make chemicals required for the green liquor extraction method will be justified by the quantity of xylan extracted will only be answered by a thorough economic assessment, which was not in the scope of this project. / AFRIKAANSE OPSOMMING: Pulp- en papiermeule word onder toenemende druk geplaas om die gebruik van die biomassa wat vir pulp verwerk word, te maksimaliseer, en om te beweeg na geïntegreerde bioraffinaderye, waar ʼn groot verskeidenheid produkte vervaardig kan word, en nie slegs uitsluitlik pulp nie. Die ekstraksie van hemisellulose voor die verpulpingsproses kan die winsgewendheid van die meule verhoog, aangesien die hemisellulose gebruik kan word vir die vervaardiging van verskeie bykomende produkte. Hemisellulose is ʼn plantpolisakkaried, met xilaan as die hemisellulose wat die oorvloedigste in hardehout gevind word, en met xilose as die primêre monosakkaried-bestanddeel van xilaan. Die meerderheid van die pulp wat in die Suidelike Halfrond geproduseer word, word met hardehout as voerstof gedoen, tipies met behulp van die Kraft-proses. Die aanloklikheid van die konsep om hemisellulose voor verpulping te win, word verder versterk deur die feit dat hemisellulose in die Kraft-proses onderbenut word. In die Kraft-proses word die hemisellulose tydens verpulping opgelos en saam met lignien verbrand vir die opwekking van energie, maar hemisellulose het egter ongeveer die helfte van die verhittingswaarde van dié van lignien. Die vernaamste doelstelling van hierdie studie was om ʼn pre-ekstraksiemetode te vind wat xilaan doeltreffend van Eucalyptus grandis, die belangrikste hardhout-voerstof wat in die Suidelike Halfrond vir verpulping gebruik word, kan vrystel. Die metode moet ook prakties wees met betrekking tot integrering met die Kraft-proses, en dit moet ʼn minimale uitwerking op pulpopbrengs en gevolglike papiergehalte hê. Xilaan-ekstraksie uit E. grandis as voerstof is uitgevoer met wit loog, groen loog en NaOH. Hierdie chemikalieë is gekies omdat hulle reeds in die Kraft-proses teenwoordig is. Die geskiktheid van hierdie chemikalieë as xilaan-ekstraksiemetodes is verder ondersteun deur die feit dat hul alkaliniteit moontlik chemiese verbruik in verpulping kan verlaag, wat ruimte vir die integrasie van hemisellulose-ekstraksie in Kraft-verpulping laat sonder om grootskaalse veranderinge aan bestaande nywerheidsprosesse te implementeer. Alkali-chemikalieë vir preekstraksie lei boonop tot ʼn minimale uitwerking op resultante pulp en papier, terwyl die alkalitoestande, met betrekking tot die geëkstraheerde produk, toestande skep wat geskik is vir ʼn hoë mate van polimerisasie van hemisellulose. Uit die ekstraksies wat uitgevoer is, is die hoogste fraksie xilaan gewin deur die gebruik van NaOH teen 15.15% w/w met 2M NaOH, teen 120 °C vir 90 minute ekstraksietyd. Dit is gevolg deur witloog-ekstraksie teen 13.27% w/w met die gebruik van 20% AA teen 140 °C vir 90 minute. Groenloog-ekstraksie het die laagste xilaan-winning teen 7.83% w/w met 2% TTA en 160°C met ʼn h-faktor van 800 voortgebring. Houtspaanders wat aan xilaan-pre-ekstraksie met groen loog onderwerp is, het pulp met kappanommers en opbrengste soortgelyk aan dié van nie-geëkstraheerde spaanders voortgebring toe die chemiese lading met 35% verlaag is, in verhouding tot dít wat vir niegeëkstraheerde spaanders gebruik is. Xilaan-pre-geëkstraheerde spaanders met wit loog het ʼn 50%-vermindering in verpulpingschemikalieë gelewer in verhouding tot houtspaanders wat aan konvensionele verpulping onderwerp is. Die chemiese reduksie van groen loog was minder as dié van wit loog weens die laer alkalilading wat tydens hemisellulose-ekstraksie voor verpulping gebruik is. Vir witloog-ekstraksie kon pulpopbrengste gehandhaaf word, alhoewel pregeëkstraheerde spaanders met wit loog ʼn neiging getoon het om pulp met laer kappanommers voort te bring. Alhoewel pulp wat uit houtspaanders gemaak is wat aan NaOH-ekstraksie onderwerp is, gelei het tot ʼn 75%-vermindering van NaOH gebruik in verhouding tot dié van konvensionele verpulping, is verwag dat geen NaOH benodig sou word nie, aangesien die houtspaanders reeds tydens xilaan-ekstraksie aan 2M NaOH blootgestel is. Voorts, in die literatuur is verpulping uitgevoer ná 2M NaOH-ekstraksie sonder dat die toevoeging van NaOH tydens verpulping nodig was [61]. Handvelle is vervaardig uit die pulp wat in die hoogste pulpopbrengs-toestande vervaardig is, en dit is vir pulpgehalte-eienskappe getoets. Die verpulpingstoestande met die hoogste opbrengs is bereik met ʼn 35%-vermindering van verpulpingschemikalieë en 45 minute verpulpingstyd in kombinasie met groenloog-pre-ekstraksie, terwyl vir verpulping met witloogpre- ekstraksie ʼn 50%-vermindering van chemikalieë en 30 minute verpulpingstyd verkies is. Vir verpulping ná NaOH-pre-ekstraksie is ʼn 75%-vermindering van die NaOH-dosis en 45 minute verpulpingstyd verkies. Alle verpulpingstappe is teen 170°C uitgevoer. Ongeklopte handvelle vervaardig uit die gekose verpulpingstoestande vir witloog- en groenloog- geëkstraheerde spaanders het soortgelyke fisiese eienskappe getoon (bars-, skeuren trek-indeks) in vergelyking met die kontrole (pulp uit nie-geëkstraheerde spaanders). Die grootste hoeveelheid xilaan is egter uit sellulose vesel met NaOH-ekstraksie verkry, wat gelei het tot pulp met laer xilaaninhoud, wat die bars- en skeur-indeks van die handvelle wat uit hierdie pulp vervaardig is, beïnvloed het. ʼn Toename in die skeur-indeks, met ʼn afname in die bars-indeks, is waargeneem vir die pulp wat uit NaOH-geëkstraheerde spaanders vervaardig is. Die gevolgtrekking is gemaak dat alhoewel witloog- en NaOH-ekstraksie groter xilaanwinning moontlik maak, die groot chemiese uitgawe geassosieer met hierdie metode ʼn aanmerklike koste-impak vir die bestaande Kraft-proses inhou. Groenloog-xilaanekstraksie sal, weens die laer alkaliniteit, meer geskik wees met betrekking tot die koste van bykomende aanvullende chemikalieë. Dit hou ook ʼn kleiner uitwerking op die pulp- en papiergehalte in, wat dit dus die praktieste van die pre-ekstraksiemetodes maak. Of die bykomende chemikalieë nodig vir die witloog- en NaOH-ekstraksies egter geregverdig kan word deur die hoeveelheid xilaan wat gewin is, kan slegs deur ʼn deeglike ekonomiese assessering beantwoord word, wat nie binne die omvang van hierdie projek geval het nie.

Biocides are widely used as a preservative or as an antiseptic agent in consumer care products such as toothpaste, mouthwash, and soaps, as well as in household cleaners and even in textiles due to their high antimicrobial effectiveness. The usage of this compounds results in discharge to wastewater treatment plants and so into surface waters. Their existence in the environment is of importance due to their negative effects on aquatic environment microorganisms and human health in terms of occurrence in surface waters and their fate in wastewater treatment plants. In this scope, this study focuses on occurrence and fate of selected biocides, namely triclosan (TCS) and chlorhexidine (CHD), in wastewater treatment plants and in surface waters. It was aimed to determine the biocides levels in surface water and wastewater in Turkey. For the wastewater treatment plant (WWTP) studies, several WWTPs with different process configurations, namely, Tatlar WWTP, METU WWTP, Kayseri WWTP and Antalya WWTPs were selected. Composite wastewater samples were taken from various points along the WWTPs on a seasonally basis for one year period. For the surface water part, samples were taken monthly from three different sources with different pollution levels, namely, Kesikk&ouml / pr&uuml / Reservoir, &Ccedil / amlidere Reservoir and Eymir Lake for one year period. All water samples were analyzed for their biocide level using liquid chromatography, following solid phase cartridge extraction. As a result of analyses, TCS concentration in surface water samples was detected as in the range of 0.65-11.15 ng/L, 0.86-48.96 ng/L and 0.86-757.7 ng/L for clean, moderately polluted and polluted water sources respectively. The recovery of solid phase extraction analyses for TCS was achieved as %92. CHD concentration was determined as in the range of &lt / 1.33-5.31 ng/L for surface water samples and the recovery of extraction were calculated as %96 for CHD. The concentration of TCS in wastewater samples was measured as in the range of 1.77-94.47 ng/L and 1.40-15.09 ng/L for influent and effluent samples respectively. These ranges became 1.39-10.45 ng/L and &lt / 1.32-2.44 ng/L for CHD. The highest concentrations of biocides were observed in sludge samples with concentrations of 1117-3687 &mu / g/kg and 510-2742 &mu / g/kg for TCS and CHD. Biocide removal efficiency of primary and biological treatment together was reported as % 67.5&plusmn / 8.2 in January 2012 Tatlar WWTP analyses.

Silver concentrations in natural water are very low and generally require preconcentration prior to instrumental analysis. Solvent extraction and anion exchange methods are the most commonly applied techniques for the determination of Ag in water samples. In this study, solvent extraction and anion exchange techniques are combined and modified to an ¡§organic complexation-acid extraction¡¨ method. The procedure developed involves four steps: (1) a buffer is added and the pH of the solution is adjusted for optimization purpose; (2) APDC and DDDC chelating agents were added and the silver in the solution is organically complexed; (3) the solution was passed through AG-MP1 anion exchange resins and silver complexes and their flocculant were retained and; and (4) acid solutions were used to extract silver from the column for subsequent determination of sliver by a graphite furnace atomic absorption spectrophotometer. After the experiments, the optimal procedures were established as the following: The pH of a 1-L aqueous sample was adjusted to ~4.5 by adding a buffer solution. Aliquots of 2.5-mL solutions containing chelating agents (2% w/v each of APDC and DDDC) were added. After being mixed, the solution was passed through an anion exchange column (AG MP-1) and silver complexes (and their flocculated particles) retained. Two 0.5¡VmL aliquots of 6, 4 and 2 N HNO3 were used to extract Ag from the column, aided by sonication for 3 min during each extraction procedure. The final volume is 3 ml, yielding a concentration factor of ~333. Determination of sliver was done by a graphite furnace atomic absorption spectrophotometer. The detection limit is 1.03 pM. This method was suitable for both freshwater and seawater samples, and was successfully applied for the determination of Ag in coastal and off-shore seawaters collected from coastal region off southwestern Taiwan.

This study investigated the use of electroporation as an extraction method of lipids in oleaginous microorganisms. Electroporation is the process of placing a voltage gradient across a lipid membrane to create pores that vary in size and longevity with voltage magnitude and pulse duration. Once the voltage gradient is removed, the lipid membrane will seal the pore. The use of electroporation on oleaginous microorganisms to extract stored lipids could be a useful tool if the microorganism is allowed to regenerate and produce more lipids. Three high-lipid media were investigated: soybeans, Rhodococcus opacus (bacteria), and Rhodotorula glutinis (yeast). This study investigates varied voltage magnitude, pulse duration, quantity of pulses, and distance between electrodes. Electroporation proved to be moderately successful for lipid removal when using low voltages and long pulse durations. However, electroporation removed only a small percentage of the intracellular lipids.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Knowledge on earthworms diversity in Rio Grande do Sul (RS) State, as well as in Brazil, is lower than the range estimated by taxonomists. The study aimed to: 1) evaluate the diversity of earthworms present in ecosystems of three regions of the RS State; 2) characterize the physical and chemical properties of soil, vegetation and land use; and 3) determine the potential use of a nontoxic solution to extract earthworms from the soil, in order to reduce the environmental impacts on ecosystems assessed. A qualitative survey of earthworms was conducted by the withdrawal of monoliths and manual screening in 15 different ecosystems. Samples were collected in 29 municipalities of the northwestern, central and southwestern regions of the RS State, comprising 77 sampling sites. Species identification was based on morphological parameters and / or molecular. Twenty-one species of earthworms were found, belonging to the families Glossoscolecidae (10), Ocnerodrilidae (4), Megascolecidae (4), Acanthodrilidae (1), Lumbricidae (1) and Criodrilidae (1). Ten correspond to new records, belonging to the genus Glossoscolex (6), Fimoscolex (1), Kerriona (1), Eukerria (1) and a new specie of the Criodrilidae family. The occurrence of earthworms species was correlated with the type of ecosystem. The highest diversity was observed in sites of native forest fragment and native grassland. Most native species (Urobenus brasiliensis, Fimoscolex n. sp. and Glossoscolex sp.) predominated in ecosystems altered by human activities, while the exotic species (Amynthas gracilis, Amynthas rodericensis, Metaphire californica, Aporrectodea trapezoides) and pilgrim (Pontoscolex corethrurus) predominate in sites with highest degree of human disturbance. The degree of disturbance of ecosystems and land use influence the presence of earthworms, followed by physical and chemical characteristics of soil. The nuclear gene 28S rDNA, as well as mitochondrial genes 16S and subunit I of cytochrome c oxidase were important tools for the molecular characterization of earthworms. Assessments of the potential of onion extract as the extraction solution for soil earthworms showed that the concentration of 175 g L-1 extract shows capacity comparable to standard extraction solution (formaldehyde 0.5%) in the extraction of earthworms in clay and sandy soils. The results of this study indicated that the Rio Grande do Sul State has greater earthworms diversity than the currently known, justifying the importance of studies of the diversity of these soil organisms. / O conhecimento sobre a diversidade de minhocas no Estado do Rio Grande do Sul (RS), assim como no Brasil, está muito aquém da diversidade estimada pelos taxonomistas. O trabalho teve como objetivos: 1) avaliar a diversidade de minhocas em ecossistemas de três regiões do Estado do RS; 2) caracterizar propriedades físicas e químicas do solo, tipo de vegetação e uso da terra; e 3) determinar o potencial de uso de uma solução atóxica para extração de minhocas do solo, como forma de reduzir os impactos ambientais sobre os ecossistemas avaliados. Realizou-se levantamento qualitativo de minhocas, através da retirada de monólitos e triagem manual, em 15 diferentes ecossistemas. As coletas foram realizadas em 29 municípios das regiões noroeste, central e sudoeste do Estado do RS, totalizando 77 locais amostrados. A identificação das espécies foi realizada com base em parâmetros morfológicos e/ou moleculares. Vinte e uma espécies de minhocas foram encontradas, pertencentes às famílias Glossoscolecidae (10), Ocnerodrilidae (4), Megascolecidae (4), Acanthodrilidae (1), Lumbricidae (1) e Criodrilidae (1). Destas, dez corresponderam a novos registros, pertencentes aos gêneros Glossoscolex (6), Fimoscolex (1), Kerriona (1), Eukerria (1) e uma nova espécie da família Criodrilidae. A ocorrência das espécies de minhocas apresentou relação com o tipo de ecossistema avaliado, sendo observada maior diversidade em áreas de fragmento de mata nativa e campo nativo. A maioria das espécies nativas (Urobenus brasiliensis, Fimoscolex n. sp. 1 e Glossoscolex sp.) predominou em ecossistemas pouco alterados pelo homem, enquanto que as espécies exóticas (Amynthas gracilis, Amynthas rodericensis, Metaphire californica, Aporrectodea trapezoides) e peregrina (Pontoscolex corethrurus) predominam em áreas com maior grau de antropização. O grau de perturbação dos ecossistemas e o uso do solo interferem na presença de minhocas, seguido pelas características físicas e químicas do solo. O gene nuclear 28S rDNA, assim como os genes mitocondriais 16S e subunidade I da citocromo c oxidase foram ferramentas importantes para caracterização molecular das minhocas. As avaliações do potencial do extrato de cebola como solução extratora de minhocas do solo demonstraram que a concentração de 175 g L-1 de extrato apresenta capacidade semelhante à solução extratora padrão (formaldeído 0,5%) na extração de minhocas em solos de textura argilosa e arenosa. Os resultados obtidos neste trabalho evidenciaram que o Estado do Rio Grande do Sul apresenta diversidade de minhocas superior à conhecida atualmente, justificando a importância de estudos da diversidade de organismos do solo em ecossistemas.

Neste trabalho é apresentado um estudo dos transistores MOS sem junções (Junctionless Nanowire Transistors - JNTs), cujo foco é a modelagem de suas características elétricas e a análise do funcionamento dos mesmos quanto à tensão de limiar, ponto invariante com a temperatura e operação analógica. Os JNTs possuem uma concentração de dopantes constante da fonte ao dreno sem apresentar gradientes. Eles foram desenvolvidos a fim de se evitar as implantações iônicas de fonte e dreno, que requerem condições rigorosamente controladas para se evitar a difusão de dopantes para o interior do canal em dispositivos de tamanho extremamente reduzido (sub-20 nm). Dessa forma, esses dispositivos permitem um maior escalamento, com um processo de fabricação simplificado. Os trabalhos recentes de modelagem desses transistores consideram dispositivos de canal longo, de forma geral o comprimento utilizado é de 1 µm, de porta dupla ou cilíndricos. Pouco tem sido feito relacionado à modelagem de JNTs porta tripla e a influência da temperatura no funcionamento dos mesmos. Assim, este trabalho tem como objetivo a modelagem do funcionamento dos dispositivos MOS sem junções de porta tripla quanto à tensão de limiar, potencial de superfície, carga de condução e corrente de dreno. Os modelos são derivados da solução da equação de Poisson com as condições de contorno adequadas, apresentando grande concordância com simulações numéricas tridimensionais e com resultados experimentais para dispositivos com comprimento de canal de até 30 nm. No caso do modelo da tensão de limiar, o maior erro obtido entre modelo e simulação foi de 33 mV, que representa uma percentagem menor que 5 %. Também foi apresentado um método de extração da tensão de limiar baseado na igualdade das componentes de deriva e difusão da corrente de dreno. Este método foi igualmente validado com resultados simulados, apresentando um erro máximo de 3 mV (menor que 0,5 %) e aplicado à dispositivos experimentais. A influência da temperatura na tensão de limiar também foi analisada tanto pelo modelo proposto como por simulações e resultados experimentais, mostrando que a dependência da concentração de dopantes ionizados com a temperatura devido à ionização incompleta dos portadores tem grande influência na tensão de limiar. No caso da modelagem da corrente de dreno e do potencial de superfície, foi acrescentada uma correção de efeitos de canal curto. O erro médio foi menor que 12 % para as curvas de corrente e suas derivadas quando comparadas à dos dispositivos experimentais de comprimento de canal de 30 nm. Também foi realizado um estudo do funcionamento dos JNTs, mostrando que o ponto invariante com a temperatura, onde a corrente de dreno se mantém constante independente da temperatura, pode ou não existir nesses dispositivos dependendo da resistência série e de sua dependência com a temperatura. Por fim, a operação analógica dos dispositivos sem junções é analisada para dispositivos de diferentes dimensões. / In this work, a study of the Junctionless Nanowire Transistors (JNTs) is presented, focusing their modeling and analyzing their operation. The JNTs are heavily doped devices with a doping concentration constant from source to drain, without presenting doping gradients. They have been developed in order to avoid drain and source ion implantation, which requires rigorous controlled conditions to avoid dopants diffusion into the channel in extremely reduced devices (sub-20 nm). Therefore, these devices provide a higher scalability with a simplified fabrication process. Recent works on junctionless nanowire transistors modeling have considered long-channel (a length of 1 µm is commonly used) double-gate or cylindrical devices. Few works have presented the modeling of triple-gate JNTs and the temperature influence on the device operation. The goal of this work is the modeling of the threshold voltage, surface potential, conduction charge and drain current in triple-gate junctionless nanowire transistors. The models are derived from the solution of the Poisson equation with the appropriate boundary conditions and exhibit a great concordance with three-dimensional numerical simulations and experimental data even for devices with channel length of 30 nm. In the case of the threshold voltage, the higher error obtained between model and simulation was 33 mV, which represents an error lower than 5 %. A method for the threshold voltage extraction based on the equality of the drift and diffusion components of the drain current has also been presented. This method was also validated using simulated results, with a maximum error of 3 mV (lower than 0.5 %), and applied to experimental devices. The influence of the temperature on the threshold voltage has also been analyzed through the proposed model, the numerical simulations and the experimental data. It has been shown that the dependence of the ionized dopant concentration with the temperature due to the incomplete carrier ionization has a great influence on the threshold voltage. In the case of the surface potential and drain current modeling, a correction for the short channel effects has been proposed. The mean error has been lower than 12 % for the drain current curves and their derivatives when compared to the ones of experimental devices with a channel length of 30 nm. An analysis on the operation of the JNTs has been also performed, showing that the zero temperature coefficient point, in which the current is the same independent of the temperature, can or not exist depending on the series resistance and its dependence on the temperature. Finally, the operation of junctionless nanowire transistors in analog applications has been analyzed for devices of different dimensions.

Neste trabalho é apresentado um estudo dos transistores MOS sem junções (Junctionless Nanowire Transistors - JNTs), cujo foco é a modelagem de suas características elétricas e a análise do funcionamento dos mesmos quanto à tensão de limiar, ponto invariante com a temperatura e operação analógica. Os JNTs possuem uma concentração de dopantes constante da fonte ao dreno sem apresentar gradientes. Eles foram desenvolvidos a fim de se evitar as implantações iônicas de fonte e dreno, que requerem condições rigorosamente controladas para se evitar a difusão de dopantes para o interior do canal em dispositivos de tamanho extremamente reduzido (sub-20 nm). Dessa forma, esses dispositivos permitem um maior escalamento, com um processo de fabricação simplificado. Os trabalhos recentes de modelagem desses transistores consideram dispositivos de canal longo, de forma geral o comprimento utilizado é de 1 µm, de porta dupla ou cilíndricos. Pouco tem sido feito relacionado à modelagem de JNTs porta tripla e a influência da temperatura no funcionamento dos mesmos. Assim, este trabalho tem como objetivo a modelagem do funcionamento dos dispositivos MOS sem junções de porta tripla quanto à tensão de limiar, potencial de superfície, carga de condução e corrente de dreno. Os modelos são derivados da solução da equação de Poisson com as condições de contorno adequadas, apresentando grande concordância com simulações numéricas tridimensionais e com resultados experimentais para dispositivos com comprimento de canal de até 30 nm. No caso do modelo da tensão de limiar, o maior erro obtido entre modelo e simulação foi de 33 mV, que representa uma percentagem menor que 5 %. Também foi apresentado um método de extração da tensão de limiar baseado na igualdade das componentes de deriva e difusão da corrente de dreno. Este método foi igualmente validado com resultados simulados, apresentando um erro máximo de 3 mV (menor que 0,5 %) e aplicado à dispositivos experimentais. A influência da temperatura na tensão de limiar também foi analisada tanto pelo modelo proposto como por simulações e resultados experimentais, mostrando que a dependência da concentração de dopantes ionizados com a temperatura devido à ionização incompleta dos portadores tem grande influência na tensão de limiar. No caso da modelagem da corrente de dreno e do potencial de superfície, foi acrescentada uma correção de efeitos de canal curto. O erro médio foi menor que 12 % para as curvas de corrente e suas derivadas quando comparadas à dos dispositivos experimentais de comprimento de canal de 30 nm. Também foi realizado um estudo do funcionamento dos JNTs, mostrando que o ponto invariante com a temperatura, onde a corrente de dreno se mantém constante independente da temperatura, pode ou não existir nesses dispositivos dependendo da resistência série e de sua dependência com a temperatura. Por fim, a operação analógica dos dispositivos sem junções é analisada para dispositivos de diferentes dimensões. / In this work, a study of the Junctionless Nanowire Transistors (JNTs) is presented, focusing their modeling and analyzing their operation. The JNTs are heavily doped devices with a doping concentration constant from source to drain, without presenting doping gradients. They have been developed in order to avoid drain and source ion implantation, which requires rigorous controlled conditions to avoid dopants diffusion into the channel in extremely reduced devices (sub-20 nm). Therefore, these devices provide a higher scalability with a simplified fabrication process. Recent works on junctionless nanowire transistors modeling have considered long-channel (a length of 1 µm is commonly used) double-gate or cylindrical devices. Few works have presented the modeling of triple-gate JNTs and the temperature influence on the device operation. The goal of this work is the modeling of the threshold voltage, surface potential, conduction charge and drain current in triple-gate junctionless nanowire transistors. The models are derived from the solution of the Poisson equation with the appropriate boundary conditions and exhibit a great concordance with three-dimensional numerical simulations and experimental data even for devices with channel length of 30 nm. In the case of the threshold voltage, the higher error obtained between model and simulation was 33 mV, which represents an error lower than 5 %. A method for the threshold voltage extraction based on the equality of the drift and diffusion components of the drain current has also been presented. This method was also validated using simulated results, with a maximum error of 3 mV (lower than 0.5 %), and applied to experimental devices. The influence of the temperature on the threshold voltage has also been analyzed through the proposed model, the numerical simulations and the experimental data. It has been shown that the dependence of the ionized dopant concentration with the temperature due to the incomplete carrier ionization has a great influence on the threshold voltage. In the case of the surface potential and drain current modeling, a correction for the short channel effects has been proposed. The mean error has been lower than 12 % for the drain current curves and their derivatives when compared to the ones of experimental devices with a channel length of 30 nm. An analysis on the operation of the JNTs has been also performed, showing that the zero temperature coefficient point, in which the current is the same independent of the temperature, can or not exist depending on the series resistance and its dependence on the temperature. Finally, the operation of junctionless nanowire transistors in analog applications has been analyzed for devices of different dimensions.