There has been much work on electron emission. It has lead to the concept of the photon and new electron sources for imaging such as electron microscopes and the rst formulation of holographic reconstructions [1-6]. Analytical derivations are important to gain physical insight into the problem of developing better electron sources. However, to date, such formulations have su ered by a number of approximations that have masked important physics. In this thesis, a new approach is provided that solves the Schrodinger wave equation for photoemission from a single atom tungsten tip barrier or more generally, for photoemission from a Schottky triangular barrier potential, with or without image potential e ects. We describe the system, then introduce the mathematical derivation. We conclude with the applications of the theory.

The current transport mechanisms in metal-oxide-semiconductor (MOS) capacitors have been studied. The devices used in this study have characterized by current-voltage analyses. Physical parameter extractions and computer generated fit methods have been applied to experimental data. Two devices have been investigated: A relatively thick oxide (125 nm) and an ultra-thin oxide (3 nm) MOS structures. The voltage and temperature dependence of these devices have been explained by using present current transport models.

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A bipolar charge transport (BCT) model is used to simulate charge injection and transportdynamics inside insulation material which are used in a high voltage direct current (HVDC)cable. Gaining knowledge about space charge density and electric field distribution in theinsulation material enables minimising charge injection at the metal-insulator interface andavoiding unnecessary energy loss. Simulation methods using the numerical Finite ElementMethod (FEM) are implemented in COMSOL multiphysics in order to investigate the effect ofchemical structure such as dipoles, physical defects such as interface roughness and impurityconcentration leading to ions, on the potential barrier and charge injection at the interface.Interface dipoles such as surface dipoles or chemical dipoles can increase or decrease thepotential barrier at the interface depending on direction/orientation of the dipole. Moreover,using a field enhancement factor to include the effect of interface roughness at the interfaceyields increased charge injection when higher values of the field enhancement factor wereused. The barrier height becomes therefore locally lower where the degree of roughness ishigher. Including the effect of ions, the electric field was observed to be enhanced near theelectodes, where it was weakened in the middle of the insulation, depending on the amount ofthe impurity concentration inside the insulation. Improvement on the charge injection lows isalso done using a combination of both Richardson-Schottky and Fowler-Nordheim chargeinjection laws to include both a classical and a quantum mechanical description in the BCTmodel. Solving for the transmission coefficient from Schrödinger equation could improve theaccuracy of Fowler-Nordheim as well. Including potentials due to image effect or chemicalcompositions such as water dipoles will affect the charge injection barrier and the transmission coefficient.

Depuis une vingtaine d'années, l'industrie de la microélectronique et en particulier le marché des mémoires non-volatiles connaît une évolution considérable, en termes d'augmentation de la capacité d'intégration et de diminution du prix de revient. Ceci a permis au grand public d'accéder aux produits électroniques (téléphones portables, baladeurs MP3, clés USB, appareils photos numériques...) qui connaissent actuellement un énorme succès. Cependant, la miniaturisation des mémoires Flash risque de rencontrer des limitations. C'est pourquoi les industriels et les laboratoires recherchent actuellement de nouvelles voies qui permettraient de prolonger la durée de vie de ces dispositifs. Dans ce contexte, l'objectif premier de cette thèse est l'étude expérimentale et théorique des mémoires non-volatiles à nanocristaux de silicium. Nous avons montré les différentes possibilités d'intégration des nanocristaux de silicium à partir d'un procédé de fabrication standard. Un démonstrateur Flash NOR 32 Mb à nanocristaux de silicium a été réalisé à partir d'un produit ATMEL. Nous nous sommes ensuite intéressés à la caractérisation électrique des cellules et matrices mémoires. Une étude exhaustive de l'influence des conditions de programmation ainsi que des paramètres technologiques sur les performances électriques a été menée. La modélisation de l'effacement Fowler-Nordheim et du « gate disturb » a permis de comprendre l'influence de certains de ces paramètres. Concernant l'écriture par porteurs chauds, nous avons étudié l'influence des conditions d'écriture sur la localisation de la charge à l'aide de simulations TCAD et d'un modèle analytique couplé à des mesures expérimentales.

Cette These experimentale examine le transport par effet tunnel entre deux couches ferromagnetiques separees par une barriere isolante ultrafine. L'enjeu de ces travaux est de rapprocher la comprehension theorique, basee sur des systemes ideaux, de la realite experimentale domin´ee par des jonctions comprenant une barriere amorphe. Au moyen de jonctions partiellement ou entierement epitaxiees integrant le materiau La0:7Sr0:3MnO3 dont nous avons confirme la polarisation de spin tunnel quasi-totale, l'influence de la structure electronique de materiaux isolants tels que SrTiO3, Ce0:69La0:31O1:845, TiO2, MgO (epitaxies) et Al2O3 (amorphe) sur le magnetotransport tunnel est mise en evidence. La theorie soutendant ces resultats est testee au moyen de mesures XMCD effectuees sur des barrieres de Al2O3 et MgO. La demi-metallicite de La0:7Sr0:3MnO3 est ensuite utilisee dans des jonctions La0:7Sr0:3MnO3 /SrTiO3 /La0:7Sr0:3MnO3 et La0:7Sr0:3MnO3 /SrTiO3 /Co afin d'affirmer quantitativement le caractere spectroscopique du transport tunnel polarise en spin entre electrodes ferromagnetiques. Ces etudes en tension montrent l'influence de la generation d'ondes de spin lors du transport tunnel sur l'ordre ferromagnetique de l'interface manganate/ isolant proche de sa temperature de transition metal-isolant. Enfin, nous utilisons l'electromigration aux interfaces afin de modifier la densite d'etats et le profil de potentiel des interfaces. Nous montrons comment il est possible de r´ealiser un dispositif aux proprietes de magnetotransport bistables; et nous examinons dans le regime tunnel Fowler-Nordheim les repercussions de ces modifications sur la formation d'etats quantifies au sein de la barriere, et l'evolution du couplage d'echange indirect entre les electrodes ferromagnetiques.

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.

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>