[pt] Este estudo tem por finalidade mostrar que os Estados Unidos adotaram uma nova estratégia para orientar sua política externa no mundo pós-Guerra Fria. A Doutrina da Contenção guiou as relações internacionais dos Estados Unidos durante o período de confronto entre as duas superpotências. Com o fim do mundo bipolar, os Estados Unidos consolidaram-se como a única superpotência mundial. Na ordem do pós-Guerra Fria, o novo referencial da política externa dos Estados Unidos seria a estratégia da Primazia. Preservar o mundo unipolar tem sido o principal objetivo da diplomacia norte-americana desde a queda do muro de Berlim. / [en] This study intends to show that the United States adpoted a new strategy to guide its foreign policy in the post Cold War world. The Doctrine of Containment has oriented the American foreign affairs throughout the period of confrontation between the two superpowers. As a result of the end of the bipolar world, the United States has emerged as the world´s only superpower. In the post Cold War order, the new beacon of the United States foreign policy would be the strategy of Primacy. Since the fall of the Berlin Wall, the maintenance of the unipolar world has been the main objective of the American foreign policy.

Introdução: Os mecanismos moleculares envolvidos na fisiopatologia dos Transtornos de Humor ainda não estão completamente elucidados. Nos últimos anos tem-se verificado um crescente reconhecimento de que alterações no sistema imune, no estresse oxidativo e de fatores neurotróficos poderiam contribuir para o desenvolvimento dos episódios de humor. O diagnóstico de Transtorno de Humor Bipolar é um desafio a ser reconhecido devido ao elevado grau de sobreposição de sintomas, que são apresentados por um paciente bipolar durante o episódio depressivo e se correlacionam com os critérios de diagnóstico para depressão maior. Neste contexto, a busca por marcadores periféricos para transtornos psiquiátricos segue há muitos anos, contudo permanece indefinida. Objetivos: Em vista disso, neste estudo avaliamos diferentes marcadores periféricos em pacientes com Depressão Unipolar e Depressão Bipolar, visando à busca de possíveis diferenças entre estes dois transtornos do humor. Métodos: Para este fim, medimos os níveis séricos de BDNF, IL-2, IL- 4, IL-6, IL-10, TNF, IFN-P, IL-17, danos a lipídios e proteínas em 54 pacientes ambulatoriais com depressão Bipolar e Unipolar pareados a 54 voluntários saudáveis. Episódio depressivo foi avaliado através da Escala Hamilton de Depressão (HAM-D). Resultados: Neste estudo encontramos aumento da IL-6 em ambos os grupos estudados comparados ao controles (p = 0,020 e p = 0, 001, respectivamente), bem como o aumento do dano a proteínas em pacientes unipolares (p = 0,003). Não foram observadas alterações nos níveis de BDNF em ambos os grupos de pacientes (p =0,295) e no conteúdo de peroxidação de lipídios (p = 0,860). Uma correlação positiva foi encontrada entre os valores de HAM-D e níveis de carbonilação (r =0,291; p =0,036) em pacientes bipolares. Conclusão: Nossos resultados indicam o envolvimento do estresse oxidativo e de uma alteração no sistema imune inflamatório em pacientes depressivos, contudo os marcadores aqui estudados não seriam ideais para diferenciação dos transtornos depressivos bipolares e unipolares, sendo necessários mais estudos, com uma amostra maior, para validação destes achados. / Background: The molecular mechanisms linked to pathophysiology of mood disorders are not yet fully elucidated. In recent years there has been a growing recognition that changes in the immune system, oxidative stress and neurotrophic factors could contribute to the development of mood episodes. The diagnosis of Bipolar disorder is a challenge to be recognized due to the high degree of overlap of symptoms, which are presented by a patient during bipolar depressive episode and correlate with the diagnostic criteria for major depression. In this context, the search for peripheral markers for psychiatric disorders has followed for many years, yet remains undefined. Objective: As a result, this study aims to search for peripheral markers for use in aiding the differential diagnosis of unipolar and bipolar depression. Methods: To this end, we measured serum levels of BDNF; IL-2, IL-4, IL-6, IL-10, TNF, IFN-P, IL-17, damage to lipids and proteins in 54 depressive Bipolar and Unipolar outpatients matched to 54 healthy volunteers. Depressive episode was assessed using the Hamilton Depression Rating Scale (HDRS). Results: In this study we found increased interleukin-6 in both groups compared to controls (p = 0.020 and p = 0.001, respectively), as well as increased damage to proteins in unipolar patients (p = 0.003). There were no changes in BDNF levels in both groups of patients (p = 0.295) and the content of lipid peroxidation (p = 0.860). A positive correlation was found between the values of HDRS and protein carbonyl levels (r = 0.291, p = 0.036) in bipolar patients. Conclusion: Our results indicate the involvement of oxidative stress, for damage to proteins, and a change in the inflammatory immune system in depressed patients; however the markers evaluated here were not suitable for differentiation of unipolar and bipolar depressive disorders, more research is needed, with a larger sample to validate these findings.

Anorexia nervosa und unipolare Affektive Störungen stellen häufige und schwerwiegende kinder- und jugendpsychiatrische Störungsbilder dar, deren Pathogenese bislang nicht vollständig entschlüsselt ist. Verschiedene Studien zeigen bei erwachsenen Patienten gravierende Auffälligkeiten in den kognitiven Funktionen. Dahingegen scheinen bei adoleszenten Patienten lediglich leichtere Einschränkungen in den kognitiven Funktionen vorzuliegen. Die Prävalenz der Anorexia nervosa und unipolaren Affektiven Störung ist mit Beginn der Adoleszenz deutlich erhöht. Es ist anzunehmen, dass kognitive Dysfunktionen, die sich bereits in diesem Alter abzeichnen, den weiteren Krankheitsverlauf bis in das Erwachsenenalter, die Behandlungsergebnisse und die Prognose maßgeblich beeinträchtigen könnten. Zudem ist von einem höheren Chronifizierungsrisiko auszugehen. In der vorliegenden Arbeit wurden daher kognitive Funktionen bei adoleszenten Patientinnen mit Anorexia nervosa sowie Patienten mit unipolaren Affektiven Störungen untersucht. Die Überprüfung der kognitiven Funktionen bei Patientinnen mit Anorexia nervosa erfolgte vor und nach Gewichtszunahme. Weiterhin wurden zugrundeliegende biologische Mechanismen überprüft. Zudem wurde die Spezifität kognitiver Dysfunktionen für beide Störungsbilder untersucht und bei Patienten mit unipolaren Affektiven Störungen geschlechtsbezogene Unterschiede exploriert. Insgesamt gingen 47 Patientinnen mit Anorexia nervosa (mittleres Alter 16,3 + 1,6 Jahre), 39 Patienten mit unipolaren Affektiven Störungen (mittleres Alter 15,5 + 1,3 Jahre) sowie 78 Kontrollprobanden (mittleres Alter 16,5 + 1,3 Jahre) in die Untersuchung ein. Sämtliche Studienteilnehmer durchliefen eine neuropsychologische Testbatterie, bestehend aus Verfahren zur Überprüfung der kognitiven Flexibilität sowie visuellen und psychomotorischen Verarbeitungsgeschwindigkeit. Neben einem Intelligenzscreening wurden zudem das Ausmaß der depressiven Symptomatik sowie die allgemeine psychische Belastung erfasst. Die Ergebnisse legen nahe, dass bei adoleszenten Patientinnen mit Anorexia nervosa, sowohl im akut untergewichtigen Zustand als auch nach Gewichtszunahme, lediglich milde Beeinträchtigungen in den kognitiven Funktionen vorliegen. Im akut untergewichtigen Zustand offenbarten sich deutliche Zusammenhänge zwischen dem appetitregulierenden Peptid Agouti-related Protein und kognitiver Flexibilität, nicht jedoch zwischen Agouti-related Protein und visueller oder psychomotorischer Verarbeitungsgeschwindigkeit. Bei dem Vergleich von Anorexia nervosa und unipolaren Affektiven Störungen prädizierte die Zugehörigkeit zu der Patientengruppe Anorexia nervosa ein Risiko für das Vorliegen kognitiver Dysfunktionen. Es zeigte sich zudem, dass adoleszente Patienten mit unipolaren Affektiven Störungen lediglich in der psychomotorischen Verarbeitungsgeschwindigkeit tendenziell schwächere Leistungen offenbarten als gesunde Kontrollprobanden. Es ergab sich jedoch ein genereller geschlechtsbezogener Vorteil für weibliche Probanden in der visuellen und psychomotorischen Verarbeitungsgeschwindigkeit. Die vorliegenden Befunde unterstreichen die Notwendigkeit der Überprüfung kognitiver Funktionen bei adoleszenten Patienten mit Anorexia nervosa sowie unipolaren Affektiven Störungen in der klinischen Routinediagnostik. Die Patienten könnten von spezifischen Therapieprogrammen profitieren, die Beeinträchtigungen in den kognitiven Funktionen mildern bzw. präventiv behandeln. / Anorexia nervosa and unipolar affective disorders are common and severe psychiatric disorders whose pathogenesis is not fully understood so far. Several studies have revealed serious impairments in cognitive functions among adult patients whereas recent research in adolescent patients shows only subtle cognitive dysfunctions. The prevalence in both disorders increases with the beginning of adolescence. Cognitive impairments that occur during adolescence may exacerbate the course of disease. Early cognitive deficits may also hinder treatment efforts and prognosis to a greater extent than during adulthood. Moreover, there is a higher risk for chronification. In the present study cognitive functions in adolescent patients with anorexia nervosa and unipolar affective disorders were examined. Cognitive functions in patients with anorexia nervosa were assessed before and after weight gain. Furthermore, the underlying biological mechanisms were explored. Moreover, the specificity for these psychiatric diagnoses as well as gender differences in patients with unipolar affective disorders were investigated. 47 patients with anorexia nervosa (mean age 16.3 + 1.6), 39 patients with unipolar affective disorders (mean age 15.5 + 1.3) and 78 healthy adolescents (mean age 16.5 + 1.3) participated in this study. Each of them completed a battery of neuropsychological tests for cognitive functions including tests for assessing cognitive flexibility as well as visual and psychomotor processing speed. Moreover, intelligence, depressive symptoms and psychological stress were explored. The findings revealed only subtle cognitive impairments in adolescent patients with anorexia nervosa, both in underweight condition and after weight gain. Besides, the results showed an association between cognitive flexibility and plasma agouti-related protein levels in female adolescent patients with acute anorexia nervosa, but not for visual or psychomotor speed and plasma agouti-related protein levels. Comparing anorexia nervosa and unipolar affective disorders, the results suggested a higher risk for cognitive dysfunctions when belonging to the anorexia nervosa group. Furthermore, the results only revealed a slightly weaker performance in psychomotor processing speed in adolescent patients with unipolar affective disorders compared to healthy adolescents. Moreover, female subjects generally displayed a better performance in visual and psychomotor processing speed. The present findings underlie the necessity of exploring cognitive functions in adolescent patients with anorexia nervosa and unipolar affective disorders within routine clinical diagnostic. Patients may benefit from specific therapy programs to reduce or prevent cognitive dysfunctions.

Η παρούσα διπλωματική εργασία πραγματεύεται τη μελέτη μίας διάταξης φωτοβολταϊκών πλαισίων εναλλασσόμενου ρεύματος (AC-PV module) και τη σύνδεση αυτής στο δίκτυο χαμηλής τάσης. Επιπρόσθετα πραγματεύεται την κατασκευή του μονοφασικού αντιστροφέα που ενσωματώνεται στην εν λόγω τοπολογία. Η εργασία αυτή εκπονήθηκε στο Εργαστήριο Ηλεκτρομηχανικής Μετατροπής Ενέργειας του Τμήματος Ηλεκτρολόγων Μηχανικών και Τεχνολογίας Υπολογιστών της Πολυτεχνικής Σχολής του Πανεπιστημίου Πατρών. Απώτερος σκοπός της εργασίας είναι η συνολική κατασκευή μίας διάταξης δύο βαθμίδων για τη διασύνδεση ενός φωτοβολταϊκού πλαισίου (Φ/Β) με το δίκτυο χαμηλής τάσης. Οι διατάξεις αυτές περιλαμβάνουν μια πρώτη βαθμίδα ανύψωσης της τάσης του Φ/Β πλαισίου και μια δεύτερη βαθμίδα που μετατρέπει τη συνεχή τάση σε εναλλασσόμενη (αντίστροφέας) και παράγει ρεύμα συμφασικό με την τάση του δικτύου (μοναδιαίος συντελεστής ισχύος). Αρχικά παραθέτουμε συγκρίνουμε τις τεχνολογίες διασύνδεσης Φ/Β στο δίκτυο χαμηλής τάσης στοχεύοντας στο να εντάξουμε ομαλά τον αναγνώστη στην υπό μελέτη τοπολογία. Στη συνέχεια παραθέτουμε μια βήμα προς βήμα θεωρητική ανάλυση όλων των εμπλεκομένων μονάδων της τοπολογίας. Πιο συγκεκριμένα πέραν της ανάλυσης των φωτοβολταικών χαρακτηριστικών, συγκρίνουμε και προσομοιώνουμε δύο τοπολογίες μετατροπέων συνεχούς τάσης σε συνεχή (boost και flyback). Επιπρόσθετα μελετούμε και προσομοιώνουμε τη μέθοδο παλμοδότησης του μονοφασικού αντιστροφέα, που είναι γνωστή υπό τον όρο "Ημιτονοειδής Διαμόρφωση του Εύρους Παλμών" (sPWM). Επόμενο βήμα αποτέλεσε η λεπτομερής διαστασιολόγηση ολόκληρου τού υπό μελέτη συστήματος και η μετέπειτα προσομοίωση της κάθε μονάδας του ξεχωριστά. Αφού διασφαλίσουμε ότι οι αυτοτελείς μοντελοποιημένες μονάδες λειτουργούν με επιτυχία προχωρούμε στην προσομοίωση της πλήρους διάταξης τόσο απουσία κλειστού βρόχου ελέγχου όσο και παρουσία αυτού. Τέλος αναλύουμε τα τεχνικά χαρακτηριστικά του αντιστροφέα που κατασκευάστηκε, καθώς και των κυκλωμάτων από τα οποία αποτελείται. και περιγράφουμε τη διαδικασία παραγωγής του κώδικα προγραμματισμού του μικροελεγκτή. Παράλληλα παραθέτουμε παλμογραφήματα και μετρήσεις που προέκυψαν από τα πειράματα που διενεργήσαμε μετά την ολοκλήρωση της κατασκευής σε εργαστηριακό περιβάλλον. / Analysis and practical implementation of a two stage topology for connection between PV modules and the common grid.

Introdução: Os mecanismos moleculares envolvidos na fisiopatologia dos Transtornos de Humor ainda não estão completamente elucidados. Nos últimos anos tem-se verificado um crescente reconhecimento de que alterações no sistema imune, no estresse oxidativo e de fatores neurotróficos poderiam contribuir para o desenvolvimento dos episódios de humor. O diagnóstico de Transtorno de Humor Bipolar é um desafio a ser reconhecido devido ao elevado grau de sobreposição de sintomas, que são apresentados por um paciente bipolar durante o episódio depressivo e se correlacionam com os critérios de diagnóstico para depressão maior. Neste contexto, a busca por marcadores periféricos para transtornos psiquiátricos segue há muitos anos, contudo permanece indefinida. Objetivos: Em vista disso, neste estudo avaliamos diferentes marcadores periféricos em pacientes com Depressão Unipolar e Depressão Bipolar, visando à busca de possíveis diferenças entre estes dois transtornos do humor. Métodos: Para este fim, medimos os níveis séricos de BDNF, IL-2, IL- 4, IL-6, IL-10, TNF, IFN-P, IL-17, danos a lipídios e proteínas em 54 pacientes ambulatoriais com depressão Bipolar e Unipolar pareados a 54 voluntários saudáveis. Episódio depressivo foi avaliado através da Escala Hamilton de Depressão (HAM-D). Resultados: Neste estudo encontramos aumento da IL-6 em ambos os grupos estudados comparados ao controles (p = 0,020 e p = 0, 001, respectivamente), bem como o aumento do dano a proteínas em pacientes unipolares (p = 0,003). Não foram observadas alterações nos níveis de BDNF em ambos os grupos de pacientes (p =0,295) e no conteúdo de peroxidação de lipídios (p = 0,860). Uma correlação positiva foi encontrada entre os valores de HAM-D e níveis de carbonilação (r =0,291; p =0,036) em pacientes bipolares. Conclusão: Nossos resultados indicam o envolvimento do estresse oxidativo e de uma alteração no sistema imune inflamatório em pacientes depressivos, contudo os marcadores aqui estudados não seriam ideais para diferenciação dos transtornos depressivos bipolares e unipolares, sendo necessários mais estudos, com uma amostra maior, para validação destes achados. / Background: The molecular mechanisms linked to pathophysiology of mood disorders are not yet fully elucidated. In recent years there has been a growing recognition that changes in the immune system, oxidative stress and neurotrophic factors could contribute to the development of mood episodes. The diagnosis of Bipolar disorder is a challenge to be recognized due to the high degree of overlap of symptoms, which are presented by a patient during bipolar depressive episode and correlate with the diagnostic criteria for major depression. In this context, the search for peripheral markers for psychiatric disorders has followed for many years, yet remains undefined. Objective: As a result, this study aims to search for peripheral markers for use in aiding the differential diagnosis of unipolar and bipolar depression. Methods: To this end, we measured serum levels of BDNF; IL-2, IL-4, IL-6, IL-10, TNF, IFN-P, IL-17, damage to lipids and proteins in 54 depressive Bipolar and Unipolar outpatients matched to 54 healthy volunteers. Depressive episode was assessed using the Hamilton Depression Rating Scale (HDRS). Results: In this study we found increased interleukin-6 in both groups compared to controls (p = 0.020 and p = 0.001, respectively), as well as increased damage to proteins in unipolar patients (p = 0.003). There were no changes in BDNF levels in both groups of patients (p = 0.295) and the content of lipid peroxidation (p = 0.860). A positive correlation was found between the values of HDRS and protein carbonyl levels (r = 0.291, p = 0.036) in bipolar patients. Conclusion: Our results indicate the involvement of oxidative stress, for damage to proteins, and a change in the inflammatory immune system in depressed patients; however the markers evaluated here were not suitable for differentiation of unipolar and bipolar depressive disorders, more research is needed, with a larger sample to validate these findings.

Introdução: Os mecanismos moleculares envolvidos na fisiopatologia dos Transtornos de Humor ainda não estão completamente elucidados. Nos últimos anos tem-se verificado um crescente reconhecimento de que alterações no sistema imune, no estresse oxidativo e de fatores neurotróficos poderiam contribuir para o desenvolvimento dos episódios de humor. O diagnóstico de Transtorno de Humor Bipolar é um desafio a ser reconhecido devido ao elevado grau de sobreposição de sintomas, que são apresentados por um paciente bipolar durante o episódio depressivo e se correlacionam com os critérios de diagnóstico para depressão maior. Neste contexto, a busca por marcadores periféricos para transtornos psiquiátricos segue há muitos anos, contudo permanece indefinida. Objetivos: Em vista disso, neste estudo avaliamos diferentes marcadores periféricos em pacientes com Depressão Unipolar e Depressão Bipolar, visando à busca de possíveis diferenças entre estes dois transtornos do humor. Métodos: Para este fim, medimos os níveis séricos de BDNF, IL-2, IL- 4, IL-6, IL-10, TNF, IFN-P, IL-17, danos a lipídios e proteínas em 54 pacientes ambulatoriais com depressão Bipolar e Unipolar pareados a 54 voluntários saudáveis. Episódio depressivo foi avaliado através da Escala Hamilton de Depressão (HAM-D). Resultados: Neste estudo encontramos aumento da IL-6 em ambos os grupos estudados comparados ao controles (p = 0,020 e p = 0, 001, respectivamente), bem como o aumento do dano a proteínas em pacientes unipolares (p = 0,003). Não foram observadas alterações nos níveis de BDNF em ambos os grupos de pacientes (p =0,295) e no conteúdo de peroxidação de lipídios (p = 0,860). Uma correlação positiva foi encontrada entre os valores de HAM-D e níveis de carbonilação (r =0,291; p =0,036) em pacientes bipolares. Conclusão: Nossos resultados indicam o envolvimento do estresse oxidativo e de uma alteração no sistema imune inflamatório em pacientes depressivos, contudo os marcadores aqui estudados não seriam ideais para diferenciação dos transtornos depressivos bipolares e unipolares, sendo necessários mais estudos, com uma amostra maior, para validação destes achados. / Background: The molecular mechanisms linked to pathophysiology of mood disorders are not yet fully elucidated. In recent years there has been a growing recognition that changes in the immune system, oxidative stress and neurotrophic factors could contribute to the development of mood episodes. The diagnosis of Bipolar disorder is a challenge to be recognized due to the high degree of overlap of symptoms, which are presented by a patient during bipolar depressive episode and correlate with the diagnostic criteria for major depression. In this context, the search for peripheral markers for psychiatric disorders has followed for many years, yet remains undefined. Objective: As a result, this study aims to search for peripheral markers for use in aiding the differential diagnosis of unipolar and bipolar depression. Methods: To this end, we measured serum levels of BDNF; IL-2, IL-4, IL-6, IL-10, TNF, IFN-P, IL-17, damage to lipids and proteins in 54 depressive Bipolar and Unipolar outpatients matched to 54 healthy volunteers. Depressive episode was assessed using the Hamilton Depression Rating Scale (HDRS). Results: In this study we found increased interleukin-6 in both groups compared to controls (p = 0.020 and p = 0.001, respectively), as well as increased damage to proteins in unipolar patients (p = 0.003). There were no changes in BDNF levels in both groups of patients (p = 0.295) and the content of lipid peroxidation (p = 0.860). A positive correlation was found between the values of HDRS and protein carbonyl levels (r = 0.291, p = 0.036) in bipolar patients. Conclusion: Our results indicate the involvement of oxidative stress, for damage to proteins, and a change in the inflammatory immune system in depressed patients; however the markers evaluated here were not suitable for differentiation of unipolar and bipolar depressive disorders, more research is needed, with a larger sample to validate these findings.

De nos jours, l'effet du réchauffement planétaire devient une question primordiale pour l'humanité. La plupart des sources d'énergie traditionnelles comme l’énergie thermique, le nucléaire, l'hydroélectricité, etc. sont dangereux et/ou potentiellement dangereux pour la nature et l'être humain. Par conséquent, une «énergie verte» est fortement souhaitée. L'énergie verte a deux caractéristiques : d'une part l’utilisation de sources d'énergie renouvelables comme l'énergie solaire ou géothermique, etc au lieu des sources d'énergie traditionnelles, ainsi qu’un meilleur rendement. Un rapport récent a souligné que la perte d'énergie aux États-Unis est plus importante que la somme de toutes les énergies renouvelables générées. Il est donc essentiel d'utiliser efficacement l'électricité et de limiter les pertes. Malheureusement, les pertes sont l'endémie des composants semi-conducteurs, le dispositif central de tout système de conversion de puissance. Le silicium (Si), le matériau le plus utilisé dans les composants semi-conducteurs a atteint sa limite physique. Des semi-conducteurs à large bande interdite tels que SiC, GaN, Ga2O3 et le diamant sont des matériaux prometteurs pour fabriquer des dispositifs à faibles pertes en état ON et avec une tension de claquage à l’état OFF élevée. Parmi eux, le diamant est un semi-conducteur idéal pour les appareils de haute puissance en raison de ses propriétés physiques supérieures aux autres matériaux. Les progrès récents sur ce sujet permettent de considérer le développement de dispositifs de puissance en diamant, par exemple les MOSFETs. Afin de réaliser un MOSFET en diamant semi-conducteur, le nombre de problèmes à surmonter est important, particulièrement maîtriser l'interface diamant/oxyde. Dans ce contexte, G. Chicot et A. Marechal (anciens doctorants de notre groupe) ont introduit les dispositifs de test MOSCAP O-diamant/Al2O3 et montré que l'alignement des bandes est de type I à l'interface O-diamant/Al2O3, ce qui est favorable pour réaliser à la fois un MOSFET à inversion et un MOSFET à déplétion. Ce doctorat s’inscrit dans la suite de ces deux thèses. Il a eu deux objectifs principaux: 1. Les recherches fondamentales, qui se consacrent à la compréhension de la caractéristique électrique d'un dispositif de test de diamant MOSCAP; 2. Partant de la compréhension du MOSCAP, un MOSFET en diamant est réalisé par le contrôle de la conduction de courant volumique. La thèse comprend ainsi trois chapitres : Le chapitre 1 traite du contexte des dispositifs de puissance ainsi que des propriétés physiques du diamant et de l'état de l'art des dispositifs en diamant. Nous introduisons également le principe de fonctionnement d'un dispositif de test MOSCAP idéal et de l'état de l'art des O-diamant MOSCAP. Le chapitre 2 est consacré à la compréhension fondamentale des O-diamant MOS capacités et comprennent trois parties principales: la partie 1 traite des questions de méthodologie liées à la croissance du diamant, le procédé de fabrication et de caractérisation électrique. Nous allons construire un modèle électrostatique empirique pour les MOSCAP O-diamant. La partie 2 discute de l'origine du courant de fuite et de la dispersion de la caractéristique capacitance-fréquence lorsque la MOSCAP est polarisée en négatif. La partie 3 traite de l'origine du courant de fuite et de la dispersion de la caractéristique capacitance-fréquence lorsque la MOSCAP est polarisée en positif. Le chapitre 3 présente notre approche pour réaliser un MOSFET en diamant dopé au Bore. Les performances du transistor et ses paramètres importants seront quantifiées. Le benchmark du dispositif et la projection vers son amélioration seront mentionnés. / Nowadays, global warming effect is one of most challenging issue for human being. Most of “traditional energy” sources like thermal power; nuclear power, hydroelectricity power, etc. are dangerous and/or potentially dangerous for nature and human being. Therefore, the "greener energy" is highly desired. The "greener energy" has two folds meaning: on one hand, using renewable energy sources like solar power, wind power or geothermal energy, etc. instead of the traditional energy sources. One another hand, use the electricity more effectively and more efficiency. A recent report has pointed out that the energy loss in US is in fact more than sum of all renewable energy generate in US. Therefore, effectively utilizing electricity and limiting the waste is critical.Unfortunately, losses are the endemic of semiconductor components, the central device of all power conversion system. Silicon (Si), the main material for semiconductor components has reached its physical limit. Wide band-gap semiconductors such as SiC, GaN, Ga2O3 and diamond are promising materials to fabricate the devices low ON-state loss and high OFF-state breakdown voltage. Among them, diamond is an ideal semiconductor for power devices due to its superior physical properties. Recent progresses on diamond technology permits one consider the diamond power devices, e.g. MOSFET.In order to realize a diamond MOSFET by controlled diamond semiconductor, the numbers of issues needed to be overcome is important, especially mastering the diamond/oxide interface. In this context, G. Chicot and A. Marechal (former PhD students in our group) has introduced the O-diamond/Al2O3 MOSCAP test devices and measured the type I band alignment at O-diamond/Al2O3 interface, which is favorable to realize both inversion MOSFET and depletion MOSFET in his PhD these. This PhD project is a continuation of two-mentioned thesis and including two main objects: 1. Fundamental investigations dedicate to understand the electrical characteristic of an O-diamond MOSCAP test device; 2. Realize a unipolar diamond MOSFET by controlling the diamond semiconductor epilayer. The thesis will include three chapters:Chapter 1 discusses the context of power devices as well as the physical properties of diamond and state-of-the-art of diamond devices. We also introduce the working principle of an ideal MOSCAP test device and States-of-the-art of O-diamond MOSCAP test devices.Chapter 2 dedicates for the fundamental understanding O-diamond MOSCAP and include three main parts: Part 1 addresses the methodology issues related to diamond growth, fabrication processing and electrical characterizations. We will construct an empirical electrostatics model for O-diamond MOSCAP. Part 2 discusses the origin of leakage current and capacitance-frequency dependent when O-diamond MOSCAP is biasing in negative direction. We quantify the interface states density at O-diamond/Al2O3 interface by conductance method and the complete electrostatics model for O-diamond/Al2O3 MOSCAP will be constructed. Part 3 discusses the origin of leakage current and the capacitance-frequency dependent when the O-diamond MOS capacitor is biasing in positive direction.Chapter 3 introduces our approach to realize a depletion mode diamond MOSFET. Transistor performance and the important parameters of the transistor will be quantified. The benchmark of the device and the projection towards its improvement will be mentioned.

This work focuses on the evaluation of the feasibility to employ silicon (Si) nanowire based parallel arrays of Schottky-barrier field effect transistors (SB-FETs) as transducers for potentiometric biosensors and their overall performance as building blocks for novel functional electronics. Nanowire parallel arrays of SB-FETs were produced and electrically characterized during this work. Nominally undoped Si nanowires with mean diameter of 20nm were synthesized by chemical vapor deposition (CVD) driven bottom-up growth and subsequently transferred via a printing process to Si/SiO2 chip substrates. Thereby, dense parallel aligned nanowire arrays are created. After dry oxidation of the nanowires, standard photolithography and deposition methods are employed to contact several hundred nanowires with interdigitated Ni electrodes in parallel. A silicidation step is used to produce axially intruded Ni-silicide (metallic) phases with a very abrupt interface to the Si (semiconducting) segment. Acting as front gate dielectric, the chip surface is entirely covered by an Al2O3 layer. For sensor applications, this layer further serves as electrical isolation of the electrodes and protects them from corrosion in electrolytes. Fabricated devices are part of the SOI (Si on insulator) transistor family with top (front) and back gate and exhibit ambipolar rectifying behavior. The top gate exhibits omega geometry with a 20nm thin Al2O3 dielectric, the back gate planar geometry with a 400nm thick SiO2 dielectric. The influence of both gates on the charge transport is summarized in the statistical analysis of transfer and output characteristic for 7 different lengths (for each 20 devices) of the Si conduction channel. A nonlinear scaling of on-currents and transconductance with channel length is revealed. Off-currents are influenced from both p- and n-type conduction at the same time. Increasing lateral electric fields (LEF) lead to a decline of suppression capability of both p- and n-currents by a single gate. This is reflected in a deteriorated swing and higher off-current towards decreasing channel lengths (increasing LEF). However, by individual gating of Schottky junction and channel, p- and n-type currents can be controlled individually. Both charge carrier types, p and n, can be suppressed efficiently at the same time leading to low off-currents and high on/off current ratio for all investigated channel lengths. This is achieved by a combined top and back double gate architecture, for which the back gate controls the Schottky junction resistance. It is demonstrated that a fixed high Schottky junction serial resistance, severely impairs the transconductance. However, the transconductance can be significantly increased by lowering this resistance via the back gate, enhancing the transducer performance significantly. Al2O3 covered SB-FETs were employed as pH sensors to evaluate their performance and signal to noise ratio (SNR). Current modulation per pH was observed to be directly proportional to the transconductance. The transistor related signal to noise ratio (SNR) is thus proportional to the transconductance to current noise ratio. Device noise was characterized and found to limit the SNR already below the peak transconductance regime. Statistical analysis showed that the nanowire SB-FET transconductance and noise both scale proportional with the current. Therefore, the SNR was found to be independent on the nanowire channel lengths under investigation. The high process yield of nanowire SB-FET parallel array fabrication close to hundred percent enables this platform to be used for simple logic and biosensor elements. Because of the low fabrication temperatures needed, the foundation is laid to produce complementary logic with undoped Si on flexible substrates. For previously reported results, the presence of Schottky junctions severely impaired the transconductance, restricting the applicability of SB-FETs as transducers. This work shows, that an electric decoupling of the Schottky junction can reduce these restrictions, making SB-FETs feasible for sensor applications. / Diese Dissertation ist der Bewertung von Silizium (Si) Nanodraht basierten Parallelschaltungen von Schottky-Barrieren-Feld-Effekt-Transistoren (SB-FETs) als Wandler für potentiometrische Biosensoren und deren generelle Leistungsfähigkeit als Bauelement neuartiger funktioneller Elektronik gewidmet. In dieser Arbeit wurden Parallelschaltungen von Nanodraht SB-FETs hergestellt und elektrisch charakterisiert. Nominell undotierte Si Nanodrähte mit durchschnittlichem Durchmesser von 20nm wurden mittels chemischer Dampfphasenabscheidung (CVD) synthetisiert und anschließend durch einen Druckprozess auf ein Si/SiO2 Chip-Substrat transferiert. Damit wurden dicht gepackte, parallel ausgerichtete Nanodraht Schichten erzeugt. Nach Trockenoxidation der Nanodrähte wurden diese mit Standard Lithographie und Abscheidungsmethoden mit interdigitalen Nickel (Ni) Elektroden als Parallelschaltung kontaktiert. Durch einen Temperprozess bilden sich axial eindiffundierte metallische Ni-Silizid-Phasen, mit einer sehr abrupten Grenzfläche zum halbleitenden Si Segments des Nanodrahts. Die Chipoberfläche wird vollständig mit einer Al2O3-Schicht bedeckt, welche als Frontgate-Dielektrikum oder als elektrische Isolation und Korrosionsschutzschicht für Elektroden in Elektrolytlösungen im Falle der Sensoranwendungen dient. Die hier gezeigten Bauelemente sind Teil der SOI (Si on insulator) Transistoren-Familie mit Top- (Front) und Backgate und zeigen ein ambipolares Schaltverhalten. Die Topgates besitzen eine Omega-Geometrie mit 20nm dickem Al2O3 Dielektrikum, das Backgate eine planare Geometrie mit 400nm dickem SiO2 Dielektrikum. Der Einfluss beider Gates auf den Ladungstransport ist in einer statistischen Analyse der Transfer- und Output-Charaktersitiken für 7 unterschiedliche Si-Leitungskanallängen zusammengefasst. Eine nichtlineare Skalierung von Strom und Transkonduktanz mit Leitungskanallänge wurde aufgedeckt. Die Ströme im Aus-Zustand des Transistors sind durch das Vorhandensein gleichzeitiger p- als auch n-Typ Leitung bestimmt. Die Zunahme lateraler elektrischer Felder (LEF) führt zu einem Verlust des gleichzeitigen Ausschaltvermögens von p- und n-Strömen bei Ansteuerung mit einem einzelnen Gate. Dies äußert sich durch einen graduell verschlechterten Swing und höheren Strom im Aus-Zustand bei verringerter Leitungskanallänge (gleichbedeutend mit erhöhten LEF). Durch eine getrennte Ansteuerung von Schottky-Kontakt und Leitungskanal lassen sich p- and n-Leitung jedoch unabhängig voneinander kontrollieren. Beide Ladungsträgertypen können so simultan effizient unterdrückt werden, was zu einem geringen Strom im Aus-Zustand und einem hohen An/Aus- Stromverhältnis für alle untersuchten Kanallängen führt. Dies wird durch eine Gatearchitektur mit kombiniertem Top- und Backgate erreicht, bei der das Backgate den Ladungstransport durch den Schottky-Kontakt und dessen Serienwiderstand kontrolliert. Es wird gezeigt, dass ein konstant hoher Schottky-Kontakt bedingter Serienwiderstand die Transkonduktanz erheblich vermindert. Jedoch kann die Transkonduktanz im höchsten Maße durch eine Herabsetzung des Serienwiderstandes durch das Backgate gesteigert werden. Dies erhöht die Leistungsfähigkeit des SB-FET als Wandler deutlich. Al2O3 oberflächenbeschichtete SB-FETs wurden als pH-Sensoren erprobt, um deren Tauglichkeit und Signal-zu-Rausch-Verhältnis (SNR) zu evaluieren. Die Strommodulation pro pH-Wert konnte als direkt proportional zur Transkonduktanz bestätigt werden. Das Transistor bedingte SNR ist daher proportional zum Verhältnis von Transkonduktanz und Stromrauschen. Bei der Analyse des Transistorrauschens wurde festgestellt, dass dieses das SNR bereits bei einer niedrigeren Transkonduktanz als der maximal Möglichen limitiert. Eine statistische Auswertung zeigte, dass sowohl SB-FET Transkonduktanz als auch Stromrauschen proportional zu dem Transistorstrom skalieren. Somit ist deren Verhältnis unabhängig von der Nanodraht-Leitungskanallänge, im hier untersuchten Rahmen. Die geringe Ausschuss bei der Fabrikation der Nanodraht SB-FET-Parallelschaltungen ermöglicht eine Nutzung dieser Plattform für simple Logik und Biosensorelemente. Durch die geringen Prozesstemperaturen wurde die Grundlage geschaffen, komplementäre Logik mit undotiertem Si auf flexiblen Substraten zu fertigen. Vorangegangene Resultate zeigte eine verminderte Transkonduktanz durch die Präsenz von Schottky-Barrieren, was die Anwendbarkeit von SB-FETs als Wandler einschränkt. Diese Arbeit zeigt, dass eine elekrtische Entkopplung der Schottky-Kontakte zu einer Aufhebung dieser Beschränkung führen kann und somit den Einsatz von SB-FETs als praktikable Wandler für Sensoranwendungen zulässt.

La thèse intitulée "Conception, caractérisation et optimisation d’un transistor à effet de champ haute tension en Carbure de Silicium (SiC) et de leur diode associée", s’est déroulée au sein du laboratoire AMPERE sous la direction du Prof. D. PLANSON. Des premiers démonstrateurs de JFET ont été réalisés. Le blocage du JFET n'est pas efficace, ceci étant lié aux difficultés de réalisation technologique. Le premier travail a consisté en leur caractérisation précise puis en leur simulation, en tenant compte des erreurs de processus de fabrication. Ensuite, un nouveau masque a été dessiné en tenant en compte des problèmes technologiques identifiés. Les performances électriques de la nouvelle génération du composant ont ainsi démontré une amélioration importante au niveau de la tenue en tension. Dans le même temps, de nouveaux problèmes se sont révélés, qu’il sera nécessaire de résoudre dans le cadre de travaux futurs. Par ailleurs, les aspects de tenue en court-circuit des JFETs en SiC commercialement disponibles ont été étudiés finement. Les simulations électrothermiques par TCAD ont révélé les modes de défaillances. Ceci a permis d'établir finalement des modèles physiques valables pour les JFETs en SiC. / Silicon carbide (SiC) has higher critical electric field for breakdown and lower intrinsic carrier concentration than silicon, which are very attractive for high power and high temperature power electric applications. In this thesis, a new 3.3kV/20A SiC-4H JFET is designed and fabricated for motor drive (330kW). This breakdown voltage is beyond the state of art of the commercial unipolar SiC devices. The first characterization shows that the breakdown voltage is lower (2.5kV) than its theoretical value. Also the on-state resistance is more important than expected. By means of finite element simulation the origins of the failure are identified and then verified by optical analysis. Hence, a new layout is designed followed by a new generation of SiC-4H JFET is fabricated. Test results show the 3.3kV JFET is developed successfully. Meanwhile, the electro-thermal mechanism in the SiC JFETs under short circuit is studied by means of TCAD simulation. The commercial 1200V SIT (USCi) and LV-JFET (Infineon) are used as sample. A hotspot inside the structures is observed. And the impact the bulk thickness and the canal doping on the short circuit capability of the devices are shown. The physical models validated by this study will be used on our 3.3kV once it is packaged.

This work focuses on the evaluation of the feasibility to employ silicon (Si) nanowire based parallel arrays of Schottky-barrier field effect transistors (SB-FETs) as transducers for potentiometric biosensors and their overall performance as building blocks for novel functional electronics. Nanowire parallel arrays of SB-FETs were produced and electrically characterized during this work. Nominally undoped Si nanowires with mean diameter of 20nm were synthesized by chemical vapor deposition (CVD) driven bottom-up growth and subsequently transferred via a printing process to Si/SiO2 chip substrates. Thereby, dense parallel aligned nanowire arrays are created. After dry oxidation of the nanowires, standard photolithography and deposition methods are employed to contact several hundred nanowires with interdigitated Ni electrodes in parallel. A silicidation step is used to produce axially intruded Ni-silicide (metallic) phases with a very abrupt interface to the Si (semiconducting) segment. Acting as front gate dielectric, the chip surface is entirely covered by an Al2O3 layer. For sensor applications, this layer further serves as electrical isolation of the electrodes and protects them from corrosion in electrolytes. Fabricated devices are part of the SOI (Si on insulator) transistor family with top (front) and back gate and exhibit ambipolar rectifying behavior. The top gate exhibits omega geometry with a 20nm thin Al2O3 dielectric, the back gate planar geometry with a 400nm thick SiO2 dielectric. The influence of both gates on the charge transport is summarized in the statistical analysis of transfer and output characteristic for 7 different lengths (for each 20 devices) of the Si conduction channel. A nonlinear scaling of on-currents and transconductance with channel length is revealed. Off-currents are influenced from both p- and n-type conduction at the same time. Increasing lateral electric fields (LEF) lead to a decline of suppression capability of both p- and n-currents by a single gate. This is reflected in a deteriorated swing and higher off-current towards decreasing channel lengths (increasing LEF). However, by individual gating of Schottky junction and channel, p- and n-type currents can be controlled individually. Both charge carrier types, p and n, can be suppressed efficiently at the same time leading to low off-currents and high on/off current ratio for all investigated channel lengths. This is achieved by a combined top and back double gate architecture, for which the back gate controls the Schottky junction resistance. It is demonstrated that a fixed high Schottky junction serial resistance, severely impairs the transconductance. However, the transconductance can be significantly increased by lowering this resistance via the back gate, enhancing the transducer performance significantly. Al2O3 covered SB-FETs were employed as pH sensors to evaluate their performance and signal to noise ratio (SNR). Current modulation per pH was observed to be directly proportional to the transconductance. The transistor related signal to noise ratio (SNR) is thus proportional to the transconductance to current noise ratio. Device noise was characterized and found to limit the SNR already below the peak transconductance regime. Statistical analysis showed that the nanowire SB-FET transconductance and noise both scale proportional with the current. Therefore, the SNR was found to be independent on the nanowire channel lengths under investigation. The high process yield of nanowire SB-FET parallel array fabrication close to hundred percent enables this platform to be used for simple logic and biosensor elements. Because of the low fabrication temperatures needed, the foundation is laid to produce complementary logic with undoped Si on flexible substrates. For previously reported results, the presence of Schottky junctions severely impaired the transconductance, restricting the applicability of SB-FETs as transducers. This work shows, that an electric decoupling of the Schottky junction can reduce these restrictions, making SB-FETs feasible for sensor applications.:Table of contents 11 List of figures 14 Abbreviations 15 Introduction 17 1 Fundamentals 23 1.1 Bottom up growth of Si nanowires 23 1.2 MOS and Schottky barrier transistor theory 25 1.2.1 MOSFET: Metal Oxide Semiconductor Field Effect Transistor 25 1.2.2 Gate coupling 27 1.2.3 Oxide charges and flatband voltage 29 1.2.4 Charge trapping and charge-voltage hysteresis 30 1.2.5 Schottky barrier 32 1.2.6 SB-FETs 34 1.3 ISFET and BioFET technology 36 1.3.1 ISFET and BioFET working principle 37 1.3.2 Noise in ISFETs 41 2 Fabrication of Schottky barrier FET parallel arrays 43 2.1 Starting point of device fabrication 43 2.2 Parallel array transistor and sensor devices 44 2.2.1 Gold nano particle deposition 45 2.2.2 Bottom-up growth of Si nanowires 46 2.2.3 Nanowire deposition methods 48 Langmuir-Blodgett 48 Adhesion tape transfer 49 Contact printing/ smearing transfer 49 2.2.4 Nanowire oxidation 50 2.2.5 Chip design 51 2.2.6 UV lithography 53 2.2.7 Oxide removal and metal deposition 54 2.2.8 Nanowire silicidation 54 2.2.9 Ionsensitive, top gate dielectric and contact passivation 56 2.2.10 On chip reference electrode 57 3 Electrical characterization 59 3.1 Electrical characterization methods 59 3.2 Transfer characteristics 60 3.2.1 Silicidation: intruded silicide contacts 62 3.2.2 Scaling of the conduction channel length 63 3.2.3 Flatband voltage, built-in potentials, fixed and trapped oxide charge 71 3.2.4 Surface effects on the channel potential of back gated SB-FETs 72 3.3 Charge traps, hysteresis and Vth drifts 73 3.3.1 Screening of back gate fields by water molecules 74 3.3.2 Native oxides: unipolarity by water promoted charge trapping 76 3.3.3 Hysteresis for thermally grown oxide back and top gate devices 78 3.3.4 Hysteresis reduction by post anneal 79 3.4 Output characteristics 80 3.4.1 Unipolar output characteristics of nanowires with native oxide shell 80 3.4.2 Ambipolar output characteristics of nanowires with dry oxidized shell 82 3.5 Temperature dependence 84 3.6 Transistor noise 86 4 pH measurements 91 4.1 Experimental setup and data analysis method 91 4.2 Transfer function in electrolyte with liquid gate 92 4.3 Sensor response on pH 92 4.4 Sensor signal drifts 96 5 Schottky junction impact on sensitivity 97 5.1 Schottky junction electrostatic decoupling in solution 97 5.1.1 Experimental setup in solution 98 5.1.2 SU8/Al2O3 passivated junctions in electrolyte 98 5.2 Meander shaped gates without Schottky junction overlap 101 5.2.1 Separated gating of Schottky junctions and channel 102 5.2.2 Enhanced transducer performance by reduced Schottky junction resistance 104 6 Summary and Outlook 107 List of publications 111 Bibliography 126 Acknowledgements 127 / Diese Dissertation ist der Bewertung von Silizium (Si) Nanodraht basierten Parallelschaltungen von Schottky-Barrieren-Feld-Effekt-Transistoren (SB-FETs) als Wandler für potentiometrische Biosensoren und deren generelle Leistungsfähigkeit als Bauelement neuartiger funktioneller Elektronik gewidmet. In dieser Arbeit wurden Parallelschaltungen von Nanodraht SB-FETs hergestellt und elektrisch charakterisiert. Nominell undotierte Si Nanodrähte mit durchschnittlichem Durchmesser von 20nm wurden mittels chemischer Dampfphasenabscheidung (CVD) synthetisiert und anschließend durch einen Druckprozess auf ein Si/SiO2 Chip-Substrat transferiert. Damit wurden dicht gepackte, parallel ausgerichtete Nanodraht Schichten erzeugt. Nach Trockenoxidation der Nanodrähte wurden diese mit Standard Lithographie und Abscheidungsmethoden mit interdigitalen Nickel (Ni) Elektroden als Parallelschaltung kontaktiert. Durch einen Temperprozess bilden sich axial eindiffundierte metallische Ni-Silizid-Phasen, mit einer sehr abrupten Grenzfläche zum halbleitenden Si Segments des Nanodrahts. Die Chipoberfläche wird vollständig mit einer Al2O3-Schicht bedeckt, welche als Frontgate-Dielektrikum oder als elektrische Isolation und Korrosionsschutzschicht für Elektroden in Elektrolytlösungen im Falle der Sensoranwendungen dient. Die hier gezeigten Bauelemente sind Teil der SOI (Si on insulator) Transistoren-Familie mit Top- (Front) und Backgate und zeigen ein ambipolares Schaltverhalten. Die Topgates besitzen eine Omega-Geometrie mit 20nm dickem Al2O3 Dielektrikum, das Backgate eine planare Geometrie mit 400nm dickem SiO2 Dielektrikum. Der Einfluss beider Gates auf den Ladungstransport ist in einer statistischen Analyse der Transfer- und Output-Charaktersitiken für 7 unterschiedliche Si-Leitungskanallängen zusammengefasst. Eine nichtlineare Skalierung von Strom und Transkonduktanz mit Leitungskanallänge wurde aufgedeckt. Die Ströme im Aus-Zustand des Transistors sind durch das Vorhandensein gleichzeitiger p- als auch n-Typ Leitung bestimmt. Die Zunahme lateraler elektrischer Felder (LEF) führt zu einem Verlust des gleichzeitigen Ausschaltvermögens von p- und n-Strömen bei Ansteuerung mit einem einzelnen Gate. Dies äußert sich durch einen graduell verschlechterten Swing und höheren Strom im Aus-Zustand bei verringerter Leitungskanallänge (gleichbedeutend mit erhöhten LEF). Durch eine getrennte Ansteuerung von Schottky-Kontakt und Leitungskanal lassen sich p- and n-Leitung jedoch unabhängig voneinander kontrollieren. Beide Ladungsträgertypen können so simultan effizient unterdrückt werden, was zu einem geringen Strom im Aus-Zustand und einem hohen An/Aus- Stromverhältnis für alle untersuchten Kanallängen führt. Dies wird durch eine Gatearchitektur mit kombiniertem Top- und Backgate erreicht, bei der das Backgate den Ladungstransport durch den Schottky-Kontakt und dessen Serienwiderstand kontrolliert. Es wird gezeigt, dass ein konstant hoher Schottky-Kontakt bedingter Serienwiderstand die Transkonduktanz erheblich vermindert. Jedoch kann die Transkonduktanz im höchsten Maße durch eine Herabsetzung des Serienwiderstandes durch das Backgate gesteigert werden. Dies erhöht die Leistungsfähigkeit des SB-FET als Wandler deutlich. Al2O3 oberflächenbeschichtete SB-FETs wurden als pH-Sensoren erprobt, um deren Tauglichkeit und Signal-zu-Rausch-Verhältnis (SNR) zu evaluieren. Die Strommodulation pro pH-Wert konnte als direkt proportional zur Transkonduktanz bestätigt werden. Das Transistor bedingte SNR ist daher proportional zum Verhältnis von Transkonduktanz und Stromrauschen. Bei der Analyse des Transistorrauschens wurde festgestellt, dass dieses das SNR bereits bei einer niedrigeren Transkonduktanz als der maximal Möglichen limitiert. Eine statistische Auswertung zeigte, dass sowohl SB-FET Transkonduktanz als auch Stromrauschen proportional zu dem Transistorstrom skalieren. Somit ist deren Verhältnis unabhängig von der Nanodraht-Leitungskanallänge, im hier untersuchten Rahmen. Die geringe Ausschuss bei der Fabrikation der Nanodraht SB-FET-Parallelschaltungen ermöglicht eine Nutzung dieser Plattform für simple Logik und Biosensorelemente. Durch die geringen Prozesstemperaturen wurde die Grundlage geschaffen, komplementäre Logik mit undotiertem Si auf flexiblen Substraten zu fertigen. Vorangegangene Resultate zeigte eine verminderte Transkonduktanz durch die Präsenz von Schottky-Barrieren, was die Anwendbarkeit von SB-FETs als Wandler einschränkt. Diese Arbeit zeigt, dass eine elekrtische Entkopplung der Schottky-Kontakte zu einer Aufhebung dieser Beschränkung führen kann und somit den Einsatz von SB-FETs als praktikable Wandler für Sensoranwendungen zulässt.:Table of contents 11 List of figures 14 Abbreviations 15 Introduction 17 1 Fundamentals 23 1.1 Bottom up growth of Si nanowires 23 1.2 MOS and Schottky barrier transistor theory 25 1.2.1 MOSFET: Metal Oxide Semiconductor Field Effect Transistor 25 1.2.2 Gate coupling 27 1.2.3 Oxide charges and flatband voltage 29 1.2.4 Charge trapping and charge-voltage hysteresis 30 1.2.5 Schottky barrier 32 1.2.6 SB-FETs 34 1.3 ISFET and BioFET technology 36 1.3.1 ISFET and BioFET working principle 37 1.3.2 Noise in ISFETs 41 2 Fabrication of Schottky barrier FET parallel arrays 43 2.1 Starting point of device fabrication 43 2.2 Parallel array transistor and sensor devices 44 2.2.1 Gold nano particle deposition 45 2.2.2 Bottom-up growth of Si nanowires 46 2.2.3 Nanowire deposition methods 48 Langmuir-Blodgett 48 Adhesion tape transfer 49 Contact printing/ smearing transfer 49 2.2.4 Nanowire oxidation 50 2.2.5 Chip design 51 2.2.6 UV lithography 53 2.2.7 Oxide removal and metal deposition 54 2.2.8 Nanowire silicidation 54 2.2.9 Ionsensitive, top gate dielectric and contact passivation 56 2.2.10 On chip reference electrode 57 3 Electrical characterization 59 3.1 Electrical characterization methods 59 3.2 Transfer characteristics 60 3.2.1 Silicidation: intruded silicide contacts 62 3.2.2 Scaling of the conduction channel length 63 3.2.3 Flatband voltage, built-in potentials, fixed and trapped oxide charge 71 3.2.4 Surface effects on the channel potential of back gated SB-FETs 72 3.3 Charge traps, hysteresis and Vth drifts 73 3.3.1 Screening of back gate fields by water molecules 74 3.3.2 Native oxides: unipolarity by water promoted charge trapping 76 3.3.3 Hysteresis for thermally grown oxide back and top gate devices 78 3.3.4 Hysteresis reduction by post anneal 79 3.4 Output characteristics 80 3.4.1 Unipolar output characteristics of nanowires with native oxide shell 80 3.4.2 Ambipolar output characteristics of nanowires with dry oxidized shell 82 3.5 Temperature dependence 84 3.6 Transistor noise 86 4 pH measurements 91 4.1 Experimental setup and data analysis method 91 4.2 Transfer function in electrolyte with liquid gate 92 4.3 Sensor response on pH 92 4.4 Sensor signal drifts 96 5 Schottky junction impact on sensitivity 97 5.1 Schottky junction electrostatic decoupling in solution 97 5.1.1 Experimental setup in solution 98 5.1.2 SU8/Al2O3 passivated junctions in electrolyte 98 5.2 Meander shaped gates without Schottky junction overlap 101 5.2.1 Separated gating of Schottky junctions and channel 102 5.2.2 Enhanced transducer performance by reduced Schottky junction resistance 104 6 Summary and Outlook 107 List of publications 111 Bibliography 126 Acknowledgements 127