This diploma thesis deals with the design and optimization of the device for measurement of field emission from gallium nitride (GaN) nanocrystals surface. The first part of the thesis is the topic review, which contains the introduction to the problematics of field emissio focused on GaN. Then there were designed, constructed and optimized two versions of the device for the measurement of field emission. Through the optimization phase, the first successful test has been performed with zinc oxide (ZnO) nanowires. Simultaneously GaN nanocrystals were fabricated on the silicon substrate Si(111) with 2 nm of silicon dioxide SiO2 and also on the copper foil covered by graphene by molecular beam epitaxy (MBE). In the last chapter, there are presented the results of the measurement for emission of GaN nanocrystals. Finally, this study is comparing results with the current research in the area of field emission, which displays the improved characteristics for field emission of GaN nanocrystals on the copper foil covered by graphene.

The aim of this work was to find a correlation between the electrical, optical and microstructural properties of thin SiO2 layers containing group IV nanostructures produced by ion beam synthesis. The investigations were focused on two main topics: The electrical properties of Ge- and Si-rich oxide layers were studied in order to check their suitability for non-volatile memory applications. Secondly, photo- and electroluminescence (PL and EL) results of Ge-, Si/C- and Sn-rich SiO2 layers were compared to electrical properties to get a better understanding of the luminescence mechanism.

<p>   The arrival of Si transistors and integrated circuit technology more than half a century ago made vacuum electronic technology almost extinct. Today, there are only a few niche applications for vacuum electronics. The main issues with this technology are its high voltage requirement and high-power consumption, difficult and costly fabrication technology, lack of integration capability, and poor reliability characteristics. Some of these issues may be addressed by going to nm scale fabrication that did not exist 60 years ago. Other problems such as reliability and lack of integration capability require alternative solutions to what has been proposed so far. Vacuum is the ultimate conduction media allowing electrons to reach the speed of light without any scattering. Consequently, a vacuum transistor, if designed correctly, can achieve THz frequency performance, while delivering Watt-level powers. No semiconductor technology can compete with vacuum technology to deliver such performance. </p> <p>In this work, novel methods for implementing nanoscale field emitter arrays used in vacuum electronics are proposed. Gated and ungated field emitters are fabricated with self-assembly technology and electron beam lithography. Different anisotropic dry etching recipes are developed to achieve emitters with different sharpness and aspect ratios. Our methods lead to field emitter array operation under low voltages (less than 20 V) and high current densities (around 50 A/cm2) using self-assembly and soft film anode-cathode isolator, and field emitter devices with ~4.5 A/cm2 current density with a turn-on voltage less than 50 V using electron beam lithography and oxide anode-cathode isolator. </p> <p>Making reliable field emitter devices is challenging. Due to Joule heating, ion bombardment, and geometrical variations for each tip in the field emitter arrays, emission current becomes nonuniform across the array. Sharper tips emit at a higher rate and eventually, the heat generated at the tip deforms the tips leading to electron emission at a lower rate. With ultra-low doped emitters, the current of each tip is limited to a few nano-amperes leading to a negligible current fluctuation at the tips. </p> <p>Our fabricated ultra-low doped devices with both self-assembly and electron beam lithography techniques presented constant emission current with almost no change over 24 hours of continuous operation. Such excellent reliability characteristics in vacuum field emitter devices have not been demonstrated to date.</p> <p>The screening effect in close-packed field emitter arrays which occurs by nearby conductive or semiconductive objects is thoroughly investigated and different solutions are proposed to reduce this effect between the emitters. Simulation studies using Sentaurus TCAD, MATLAB, and COMSOL Multiphysics simulators facilitated the design and optimization of gated and ungated field emitter arrays. These studies included the effect of sharpness, the distance between neighboring emitters, enclosing the emitters by a Si block around the emitters as well as anode-cathode separation on the electrical characterization of field emitter arrays. </p> <p>The optimum location and operating voltages which lead to a maximum gate control and emitter current density are also studied for gated field emitter arrays. Instead of individually gating each field emitter, it was found that controlling the emission of a sub-array with a metallic all-around gate is more efficient and it leads to higher current densities. Guided by simulations, gated field emitter arrays with 5×5 and 2×2 sub-arrays are developed. In terms of strength of the grid control (transconductance), turn-on voltage, maximum emission current, and field intensification factor, the device with the 2×2 sub-array was superior to the one with the 5×5 sub-array. The VFET with 5×5 sub-arrays achieved a higher current density due to a larger number of field emitters packed per active emission area. Finally, plans to further improve the technology and transitioning into the fabrication of vacuum integrated circuits are discussed.</p> <p>  </p>

La miniaturisation de la structure de transistor MOS a conduit à l'amincissement de l’oxyde de grille. Ainsi, la dégradation et le claquage sous contrainte électrique est devenu l'un des problèmes de fiabilité les plus importants des couches minces d'oxydes. L'utilisation de techniques de caractérisation permettant de mesurer les courants de fuite avec une résolution spatiale nanométrique a montré que le phénomène de claquage des oxydes est un phénomène très localisé. Le diamètre des «points chauds», des endroits où le courant de fuite est très élevé pour une tension appliquée continue, peut-être de quelques nanomètres uniquement. Ceci illustre pourquoi les méthodes de caractérisation avec une résolution spatiale à l’échelle nanométrique peuvent fournir des informations supplémentaires par rapport à la caractérisation classique macroscopique. Il y a deux instruments, dérivés de la microscopie à force atomique (AFM) qui peuvent être utilisés pour faire ce travail, soit le Tunneling Atomic Force Microscope (TUNA) ou le Conductive Atomic Force Microscope (C-AFM). Le mode TUNA qui est utilisé dans notre travail est capable de mesurer des courants très faibles variant entre 60 fA et 100 pA. Notre travail peut être divisé en deux thèmes principaux: - La caractérisation électrique des couches minces d'oxydes high-k (LaAlO3 et Gd2O3) à l'échelle nanométrique en utilisant le Dimension Veeco 3100 où nous avons montré que la différence de leurs techniques d'élaboration influe largement sur le comportement électrique de ces oxydes. - Les caractérisations électriques et physiques à l’échelle nanométrique des couches minces d’oxydes thermiques SiO2 sous différentes atmosphères, c.à.d. dans l'air et sous vide (≈ 10-6 mbar) en utilisant le microscope Veeco E-Scope. L'influence de l’atmosphère a été bien étudiée, où nous avons montré que les phénomènes de claquage des couches minces d'oxydes peuvent être fortement réduits sous vide surtout en l'absence du ménisque d'eau sur la surface de l'oxyde pendant les expériences. En utilisant les plusieurs modes de l'AFM, il a été démontré que l'existence de bosses anormales (hillocks) sur la surface de l'oxyde après l'application d'une tension électrique est une combinaison de deux phénomènes: la modification morphologique réelle de la surface de l'oxyde et la force électrostatique entre les charges piégées dans le volume de l'oxyde et la pointe de l'AFM. Selon les images du courant obtenues par AFM en mode TUNA, deux phénomènes physiques pour la création de ces hillocks ont été proposés: le premier est l'effet électro-thermique et la seconde est l'oxydation du substrat Si à l’interface Si/oxyde. / Miniaturization of the MOS transistor structure has led to the high thinning of the gate oxide. Hence, degradation and breakdown under electrical stress became one of the important reliability concerns of thin oxide films. The use of characterization techniques allowing to measure leakage currents with a nanometric spatial resolution has shown that breakdown phenomenon of oxides is a highly localized phenomenon. So called “hot spots”, places where the leakage current is very high for a given applied continuous voltage, can be several nanometers wide only. This illustrates why nanometric characterization methods with a nanometer range spatial resolution provide additional information compared to the classical macroscopic characterization. There are two instruments that can be used to do this job, either the Tunneling Atomic Force Microscope (TUNA) or the Conductive Atomic Force Microscope (C-AFM). TUNA which is used in our work is capable to measure very low currents ranging between 60 fA and 100 pA. Our work can be divided into two principle topics: - Electrical characterization of thin high-k oxides (LaAlO3 and Gd2O3) at the nano-scale using the Veeco Dimension 3100 where we have shown that the difference in their elaboration techniques largely influence the electrical behavior of these oxides. - Nano-scale electrical and physical characterization of thin SiO2 thermal oxides in different surrounding ambient, that is in air and under vacuum (≈ 10-6 mbar) using the Veeco E-scope microscope. The influence of the experiment surrounding ambient has been well studied where we have shown that the breakdown phenomena of thin oxide films can be highly reduced under vacuum especially in the absence of the water meniscus on the oxide’s surface under study. Using different AFM modes, it was demonstrated that the existence of the well-known hillock (protrusions) on the oxide’s surface after the application of an electrical stress is a combination of two phenomena: the real morphological modification of the oxide’s surface and the electrostatic force between the trapped charges in the oxide’s volume and the AFM tip. Depending on the current images obtained by TUNA AFM mode, two physical phenomena for the creation of these hillocks have been proposed: the first is the electro-thermal effect and the second is the oxidation of the Si substrate at the Si/oxide interface.

La miniaturisation de la structure de transistor MOS a conduit à l'amincissement de l'oxyde de grille. Ainsi, la dégradation et le claquage sous contrainte électrique est devenu l'un des problèmes de fiabilité les plus importants des couches minces d'oxydes. L'utilisation de techniques de caractérisation permettant de mesurer les courants de fuite avec une résolution spatiale nanométrique a montré que le phénomène de claquage des oxydes est un phénomène très localisé. Le diamètre des "points chauds", des endroits où le courant de fuite est très élevé pour une tension appliquée continue, peut-être de quelques nanomètres uniquement. Ceci illustre pourquoi les méthodes de caractérisation avec une résolution spatiale à l'échelle nanométrique peuvent fournir des informations supplémentaires par rapport à la caractérisation classique macroscopique. Il y a deux instruments, dérivés de la microscopie à force atomique (AFM) qui peuvent être utilisés pour faire ce travail, soit le Tunneling Atomic Force Microscope (TUNA) ou le Conductive Atomic Force Microscope (C-AFM). Le mode TUNA qui est utilisé dans notre travail est capable de mesurer des courants très faibles variant entre 60 fA et 100 pA. Notre travail peut être divisé en deux thèmes principaux: - La caractérisation électrique des couches minces d'oxydes high-k (LaAlO3 et Gd2O3) à l'échelle nanométrique en utilisant le Dimension Veeco 3100 où nous avons montré que la différence de leurs techniques d'élaboration influe largement sur le comportement électrique de ces oxydes. - Les caractérisations électriques et physiques à l'échelle nanométrique des couches minces d'oxydes thermiques SiO2 sous différentes atmosphères, c.à.d. dans l'air et sous vide (≈ 10-6 mbar) en utilisant le microscope Veeco E-Scope. L'influence de l'atmosphère a été bien étudiée, où nous avons montré que les phénomènes de claquage des couches minces d'oxydes peuvent être fortement réduits sous vide surtout en l'absence du ménisque d'eau sur la surface de l'oxyde pendant les expériences. En utilisant les plusieurs modes de l'AFM, il a été démontré que l'existence de bosses anormales (hillocks) sur la surface de l'oxyde après l'application d'une tension électrique est une combinaison de deux phénomènes: la modification morphologique réelle de la surface de l'oxyde et la force électrostatique entre les charges piégées dans le volume de l'oxyde et la pointe de l'AFM. Selon les images du courant obtenues par AFM en mode TUNA, deux phénomènes physiques pour la création de ces hillocks ont été proposés: le premier est l'effet électro-thermique et la seconde est l'oxydation du substrat Si à l'interface Si/oxyde.

Quanto mais nostálgicas e românticas se tornam as noções que apresentam sobre mundo idealizado de Austen, mais claramente podemos perceber as carências que fazem com que assim o percebam. Portanto, o objetivo desta tese é apresentar uma leitura de The Jane Austen Book Club através da aproximação com a obra de Austen, e assim entender o que as personagens de Fowler estão procurando, e por quê. A premissa é que essa busca revela muito a respeito do mundo contemporâneo. No âmbito da literatura, tomando Austen e Fowler como autoras que revelam os protocolos de leitura de suas épocas, espero explicitar algumas das razões do fascínio exercido por Austen sobre o leitor de hoje. Para tanto, utilizo como apoio teórico o contraste entre os conceitos de modernidade sólida e modernidade líquida propostos por Zygmunt Bauman, especialmente em relação às considerações sobre os termos fluidez, ética, velocidade, desimpedimento e medo. / Almost two hundred years separate Karen Joy Fowler from Jane Austen. The latter is a great English literary icon, author to six of the best treasured novels in English literature, admired for her style, wit and subtlety in the delineation of her characters and their social relations. The former is a contemporary awarded American Sci-fi and Fantasy writer, author to the novel The Jane Austen Book Club, which is the corpus of the present dissertation. In spite of the wide distance in time, subject matter, and even in literary stature that separates them, both authors are deeply involved in the investigation of human nature and human bonds. The Jane Austen Book Club not only pays homage to Jane Austen, it also offers a rich contrast between life as it was, in the 18th Century, in Austen’s rural England, and as it is now, in Fowler’s present-day sunny California. In Fowler’s novel we meet six interesting characters who undergo different kinds of personal crises. They form a book club and meet monthly, during half a year. In each meeting, they discuss one of Jane Austen´s novels. Each of them is in charge of leading the discussion on one of the novels. Fowler’s book is divided in six chapters, respectively: Jocelyn with Emma, Allegra with Sense and Sensibility, Prudie with Mansfield Park, Grigg with Northanger Abbey, Bernadette with Pride and Prejudice, and Sylvia with Persuasion. The way they interact with their assigned novels tells much not only about them and their circumstances, but also about the world in which they live. The more nostalgic and romantic their notion of Austen’s idealized past becomes, the clearer we can identify the circumstances in present-day life that provoke such reactions. The aim of this dissertation is to present a reading of The Jane Austen Book Club through an approximation with Austen’s work, so as to understand what Fowler’s characters are looking for, and why. The premise is that their quest tells about the world we live in nowadays, and about the difficulties we have in dealing with personal relations. To approach the contrast between the solid fictional world of Jane Austen and the liquid fictional world of Karen Joy Fowler, I rely on the theories presented by Zygmunt Bauman, especially on his use of concepts as fluidity, ethics, velocity, disengagement and fear.

Quanto mais nostálgicas e românticas se tornam as noções que apresentam sobre mundo idealizado de Austen, mais claramente podemos perceber as carências que fazem com que assim o percebam. Portanto, o objetivo desta tese é apresentar uma leitura de The Jane Austen Book Club através da aproximação com a obra de Austen, e assim entender o que as personagens de Fowler estão procurando, e por quê. A premissa é que essa busca revela muito a respeito do mundo contemporâneo. No âmbito da literatura, tomando Austen e Fowler como autoras que revelam os protocolos de leitura de suas épocas, espero explicitar algumas das razões do fascínio exercido por Austen sobre o leitor de hoje. Para tanto, utilizo como apoio teórico o contraste entre os conceitos de modernidade sólida e modernidade líquida propostos por Zygmunt Bauman, especialmente em relação às considerações sobre os termos fluidez, ética, velocidade, desimpedimento e medo. / Almost two hundred years separate Karen Joy Fowler from Jane Austen. The latter is a great English literary icon, author to six of the best treasured novels in English literature, admired for her style, wit and subtlety in the delineation of her characters and their social relations. The former is a contemporary awarded American Sci-fi and Fantasy writer, author to the novel The Jane Austen Book Club, which is the corpus of the present dissertation. In spite of the wide distance in time, subject matter, and even in literary stature that separates them, both authors are deeply involved in the investigation of human nature and human bonds. The Jane Austen Book Club not only pays homage to Jane Austen, it also offers a rich contrast between life as it was, in the 18th Century, in Austen’s rural England, and as it is now, in Fowler’s present-day sunny California. In Fowler’s novel we meet six interesting characters who undergo different kinds of personal crises. They form a book club and meet monthly, during half a year. In each meeting, they discuss one of Jane Austen´s novels. Each of them is in charge of leading the discussion on one of the novels. Fowler’s book is divided in six chapters, respectively: Jocelyn with Emma, Allegra with Sense and Sensibility, Prudie with Mansfield Park, Grigg with Northanger Abbey, Bernadette with Pride and Prejudice, and Sylvia with Persuasion. The way they interact with their assigned novels tells much not only about them and their circumstances, but also about the world in which they live. The more nostalgic and romantic their notion of Austen’s idealized past becomes, the clearer we can identify the circumstances in present-day life that provoke such reactions. The aim of this dissertation is to present a reading of The Jane Austen Book Club through an approximation with Austen’s work, so as to understand what Fowler’s characters are looking for, and why. The premise is that their quest tells about the world we live in nowadays, and about the difficulties we have in dealing with personal relations. To approach the contrast between the solid fictional world of Jane Austen and the liquid fictional world of Karen Joy Fowler, I rely on the theories presented by Zygmunt Bauman, especially on his use of concepts as fluidity, ethics, velocity, disengagement and fear.

Quanto mais nostálgicas e românticas se tornam as noções que apresentam sobre mundo idealizado de Austen, mais claramente podemos perceber as carências que fazem com que assim o percebam. Portanto, o objetivo desta tese é apresentar uma leitura de The Jane Austen Book Club através da aproximação com a obra de Austen, e assim entender o que as personagens de Fowler estão procurando, e por quê. A premissa é que essa busca revela muito a respeito do mundo contemporâneo. No âmbito da literatura, tomando Austen e Fowler como autoras que revelam os protocolos de leitura de suas épocas, espero explicitar algumas das razões do fascínio exercido por Austen sobre o leitor de hoje. Para tanto, utilizo como apoio teórico o contraste entre os conceitos de modernidade sólida e modernidade líquida propostos por Zygmunt Bauman, especialmente em relação às considerações sobre os termos fluidez, ética, velocidade, desimpedimento e medo. / Almost two hundred years separate Karen Joy Fowler from Jane Austen. The latter is a great English literary icon, author to six of the best treasured novels in English literature, admired for her style, wit and subtlety in the delineation of her characters and their social relations. The former is a contemporary awarded American Sci-fi and Fantasy writer, author to the novel The Jane Austen Book Club, which is the corpus of the present dissertation. In spite of the wide distance in time, subject matter, and even in literary stature that separates them, both authors are deeply involved in the investigation of human nature and human bonds. The Jane Austen Book Club not only pays homage to Jane Austen, it also offers a rich contrast between life as it was, in the 18th Century, in Austen’s rural England, and as it is now, in Fowler’s present-day sunny California. In Fowler’s novel we meet six interesting characters who undergo different kinds of personal crises. They form a book club and meet monthly, during half a year. In each meeting, they discuss one of Jane Austen´s novels. Each of them is in charge of leading the discussion on one of the novels. Fowler’s book is divided in six chapters, respectively: Jocelyn with Emma, Allegra with Sense and Sensibility, Prudie with Mansfield Park, Grigg with Northanger Abbey, Bernadette with Pride and Prejudice, and Sylvia with Persuasion. The way they interact with their assigned novels tells much not only about them and their circumstances, but also about the world in which they live. The more nostalgic and romantic their notion of Austen’s idealized past becomes, the clearer we can identify the circumstances in present-day life that provoke such reactions. The aim of this dissertation is to present a reading of The Jane Austen Book Club through an approximation with Austen’s work, so as to understand what Fowler’s characters are looking for, and why. The premise is that their quest tells about the world we live in nowadays, and about the difficulties we have in dealing with personal relations. To approach the contrast between the solid fictional world of Jane Austen and the liquid fictional world of Karen Joy Fowler, I rely on the theories presented by Zygmunt Bauman, especially on his use of concepts as fluidity, ethics, velocity, disengagement and fear.

No description available.

This thesis is concerned with one key aspect of the reception of the vernacular poetry of Francesco Petrarca (Petrarch), namely translations and imitations of the Rerum vulgarium fragmenta (Rvf) and Triumphi in English. It aims to provide a more comprehensive survey of the vernacular Petrarch’s legacy to English literature than is currently available, with a particular focus on some hitherto critically neglected texts and authors. It also seeks to ascertain to what degree the socio-historical phenomena of religion, politics, and culture have influenced the translations and imitations in question. The approach has been both chronological and comparative. This strategy will demonstrate with greater clarity the monumental effect of the Elizabethan Reformation on the English reception of Petrarch. It proposes a solution to the problem of the long gap between Geoffrey Chaucer’s re-writing of Rvf 132 and the imitations of Wyatt and Surrey framed in the context of Chaucer’s sophisticated imitative strategy (Chapter I). A fresh reading of Sir Philip Sidney’s Astrophil and Stella is offered which highlights the author’s misgivings about the dangers of textual misinterpretation, a concern he shared with Petrarch (Chapter II). The analysis of Edmund Spenser’s Amoretti and Epithalamion in the same chapter reveals a hitherto undetected Ovidian subtext to Petrarch’s Rvf 190. Chapter III deals with two English versions of the Triumphi: I propose a date for Lord Morley’s translation which suggests it may be the first post- Chaucerian English engagement with Petrarch; new evidence is brought to light which identifies the edition of Petrarch used by William Fowler as the source text for his Triumphs of Petrarcke. The fourth chapter constitutes the most extensive investigation to date of J. M. Synge’s engagement with the Rvf, and deals with the question of translation as subversion. On the theoretical front, it demonstrates how Synge’s use of “folk-speech” challenges Venuti’s binary foreignising/domesticating system of translation categorisation.