No description available.

Fabrication of ordered anodic alumina nanopore arrays and anodization parameters including electrolyte, concentration, voltage, temperature and time have been investigated. Cobalt nanoparticles were electrodeposited at the bottom of the pores. Vertically aligned, open-tipped multi-walled carbon nanotube arrays of high density and uniformity were synthesized via a flame method on silicon substrates using a nanoporous template of anodized aluminum oxide. The diameter and length of the nanotubes are controlled by the geometry of the aluminum oxide template. It is the cobalt catalyst particles, not the porous aluminum templates, help the growth of carbon nanotubes through graphitization and bonding of carbon nanotubes to the silicon substrates. Fabrication of nano-structures has been demonstrated. Nano-trenches of 20 nm have been achieved using single-walled nanotube bundles as shadow masks, which were aligned across electrodes under high frequency AC voltage.

This work aims to study the pressure dependence of the thickness of the epitaxial silicon carbide SiC film growing from crystalline silicon Si due to the heterogeneous reaction with gaseous carbon monoxide CO.

No description available.

[pt] O Nitreto de Boro Hexagonal (h-BN) é um material composto por átomosalternados de Boro (B) e Nitrogênio (N) com um aspecto hexagonal. Os filmesfinos de h-BN desempenham um papel crucial no desenvolvimento de aplicações como em dispositivos 2D baseados em heteroestruturas de Van der Waals,revestimentos protetivos, tribológicos, entre outros. A síntese de h-BN aindarepresenta um desafio significativo. Nesta tese, investigou-se a síntese do h-BNutilizando o método de low pressure chemical vapour deposition (LPCVD),empregando amônia borane (AB) como fonte precursora de B e N. O estudofocou-se no crescimento direto sobre o substrato de silício <100>, eliminando,assim, a necessidade de transferência do filme para posterior caracterizaçãoe evitando a degradação e contaminações associadas ao processo de transferência. A primeira parte deste estudo concentrou-se no crescimento por CVD,controlando os parâmetros de quantidade de material precursor, temperaturade evaporação do precursor e do forno, fluxo de gases nas etapas de reduçãoe de síntese, temperatura, tempo de redução, síntese e resfriamento. Foramsintetizadas duas séries: uma em função da temperatura de crescimento entre1173 e 1373 K, e uma segunda em função do tempo de síntese a uma temperatura de 1373 K. Os filmes foram caracterizados por espectroscopias Raman,infravermelho por transformada de Fourier (FTIR), UV-visível (UV-Vis), de fotoelétrons excitados por raios X (XPS), microscopia de força atômica (AFM),ângulo de contato, microscopia eletrônica de varredura (SEM), microscopiaeletrônica de varredura por transmissão (STEM) e tribologia. Inicialmente,foi estudado o efeito da temperatura de crescimento na qualidade dos filmescrescidos por 10 minutos. Os resultados de espectroscopia Raman confirmamo crescimento de h-BN, evidenciado pelo pico E2g em aproximadamente 1375cm−1. Estudos morfológicos mostraram que variações de temperatura levam àformação de diferentes estruturas na superfície do Si. O crescimento é observado a partir de 1273 K, enquanto amostras crescidas abaixo de 1223 K nãoapresentam sinais de crescimento. Observamos a formação de folhas bidimensionais (2D) com dimensões laterais variando de 80 a 500 nm, assim como ocrescimento contínuo de filmes com nanocristais de tamanhos variados. A razão B:N determinada por XPS foi de aproximadamente 1:1 e o gap óptico dosfilmes de h-BN foi determinado em 5,75 eV. O estudo de tribologia demonstrouum coeficiente de atrito de 0,1 e não houve delaminação após 3000 ciclos deida e volta lineares no teste esfera no disco percorrendo 10 mm em cada ciclono filme, enquanto o do Si foi de 0,6. Para os filmes sintetizados em função dotempo, a caracterização por espectroscopia Raman revelou um pico de modode vibração E2g em 1374 cm−1com intensidade correlacionada à espessura dofilme. A espectroscopia FTIR confirmou a presença de ligações B-N, e a bandaóptica foi determinada em 5,65 eV. O ângulo de contato mostrou filmes hidrofóbicos. Os dados de XPS indicaram uma relação estequiométrica 1:1 entre Be N, e a espessura foi analisada pela medida de seção transversal por STEM,sendo da ordem de 20 nm para filmes crescidos por 10 minutos a 1373 K. / [en] Hexagonal Boron Nitride (h-BN) is a material composed of alternating Boron (B) and Nitrogen (N) atoms with a hexagonal aspect. Thin films of h-BN play a crucial role in the development of applications such as 2D devices based on Van der Waals heterostructures, protective coatings, tribological applications, among others. The synthesis of h-BN still represents a significant challenge. In this thesis, the synthesis of h-BN was investigated using the low-pressure chemical vapor deposition (LPCVD) method, employing ammonia borane (AB) as a precursor source of B and N. The study focused on direct growth on the silicon <100> substrate, thus eliminating the need for film transfer for subsequent characterization and avoiding degradation and contamination associated with the transfer process. The first part of this study focused on CVD growth, controlling parameters such as the amount of precursor material, precursor and furnace evaporation temperature, gas flow rates during the reduction and synthesis stages, temperature, reduction time, synthesis, and cooling. Two series were synthesized: one as a function of growth temperature between 1173 and 1373 K, and a second as a function of synthesis time at a temperature of 1373 K. The films were characterized by spectroscopy, Raman, Fourier-transform infrared (FTIR), UV-visible (UV-Vis), X-ray photoelectron (XPS), atomic force microscopy (AFM), contact angle measurements, scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), and tribology. Initially, the effect of growth temperature on the quality of films grown for 10 minutes was studied. Raman spectroscopy results confirmed the growth of h-BN, evidenced by the E2g peak at approximately 1375 cm−1 . Morphological studies showed that temperature variations lead to the formation of different structures on the Si surface. Growth is observed from 1273 K, while samples grown below 1223 K show no signs of growth. We observed the formation of two-dimensional (2D) nanosheets with lateral dimensions ranging from 80 to 500 nm, as well as the continuous growth of films with nanocrystals of varying sizes. The B:N ratio determined by XPS was approximately 1:1, and the optical gap of the h-BN films was determined to be 5.75 eV. Tribology studies demonstrated a friction coefficient of 0.1, and there was no delamination after 3000 linear reciprocating cycles in the ball-on-disk test, covering 10 mm in each cycle on the film, while for Si it was 0.6. For films synthesized as a function of time, Raman spectroscopy characterization revealed an E2g vibration mode peak at 1374 cm−1 with intensity correlated to the film thickness. FTIR spectroscopy confirmed the presence of B-N bonds, and the optical band was determined to be 5.65 eV. Contact angle measurements showed hydrophobic films. XPS data indicated a stoichiometric 1:1 ratio between B and N, and the thickness was analyzed by cross-sectional STEM measurements, being around 20 nm for films grown for 10 minutes at 1373 K.

La substitution du canal de silicium par un semi-conducteur III-V est une des voies envisagées pour accroitre la mobilité des électrons dans les transistors n-MOSFET et ainsi réduire la consommation des circuits. Afin de réduire les coûts et de profiter des plateformes industrielles de la microélectronique, les transistors III-V doivent être réalisés sur des substrats de silicium. Cependant, la différence de paramètre de maille entre le Si et les couches III-V induit de nombreux défauts cristallins dans le canal du transistor, diminuant la mobilité des porteurs. L’objectif de cette thèse est la réalisation de transistors à canal III-V sur substrat de silicium au sein de la plateforme microélectronique du CEA Leti. Dans le cadre de ces travaux, deux filières technologiques d’intégration ont été développées pour la réalisation de transistors tri-gate à base d’In0,53Ga0,47As sur substrat de silicium : par un collage moléculaire d’une couche d’InGaAs sur InP et par une épitaxie directe de la couche d’InGaAs sur substrat Si. Les différentes étapes technologiques spécifiques à l’InGaAs ont été mises au point au cours de ces travaux, en prenant en compte les contraintes de contamination des équipements. Le traitement de surface de l’InGaAs et le dépôt du diélectrique de grille à haute permittivité (type high-k) par ALD ont été particulièrement étudiés afin de réduire la quantité d’états d’interface (Dit) et d’optimiser l’EOT. Pour cela, des analyses XPS et des mesures électriques C(V) de capacités MOS ont été réalisées à l’échelle d’un substrat de 300mm de diamètre. / The replacement of the silicon channel by III-V materials is investigated to increase the electron mobility in the channel and reduce the power consumption. In order to decrease the cost and to take advantage of the microelectronic silicon platform, III-V transistors must be built on Silicon substrates. However, the lattice parameter mismatch between Silicon and the III-V layers leads to a high defects density in the channel and reduces the carrier mobility. This thesis aims to realize III-V transistors on silicon substrate in the CEA-Leti microelectronic clean room. In the frame of this PhD, two integration process are elaborated to realize In0,53Ga0,47As tri-gate transistors on silicon: the molecular bonding of an InGaAs layer grown on a InP substrate, and the direct epitaxy of InGaAs on a silicon substrate. The fabrication steps for InGaAs transistors were developed, taking into account the clean room contamination restriction. InGaAs surface treatment and high-permittivity dielectric deposition by ALD are studied in order to reduce the density of interface states (Dit) and to optimize the EOT. XPS analysis and C(V) measurement are performed at the scale of a 300mm Silicon substrate.

The present work has been focused on the growth of Group III-nitride epitaxial layers and nanostructures on Si (111) substrates by plasma-assisted molecular beam epitaxy. Silicon is regarded as a promising substrate for III-nitrides, since it is available in large quantity, at low cost and compatible to microelectronics device processing. However, three-dimensional island growth is unavoidable for the direct growth of GaN on Si (111) because of the extreme lattice and thermal expansion coefficient mismatch. To overcome these difficulties, by introducing β-Si3N4 buffer layer, the yellow luminescence free GaN can be grow on Si (111) substrate. The overall research work carried out in the present study comprises of five main parts. In the first part, high quality, crack free and smooth surface of GaN and InN epilayers were grown on Si(111) substrate using the substrate nitridation process. Crystalline quality and surface roughness of the GaN and InN layers are extremely sensitive to nitridation conditions such as nitridation temperature and time. Raman and PL studies indicate that the GaN film obtained by the nitridation sequences has less tensile stress and optically good. The optical band gaps of InN are obtained between ~0.73 to 0.78 eV and the blueshift of absorption edge can be induced by background electron concentration. The higher electron concentration brings in the larger blueshift, due to a possible Burstein–Moss effect. InN epilayers were also grown on GaN/Si(111) substrate by varying the growth parameters such as indium flux, substrate temperature and RF power. In the second part, InGaN/Si, GaN/Si3N4/n-Si and InN/Si3N4/n-Si heterostructures were fabricated and temperature dependent electrical transport behaviors were studied. Current density-voltage plots (J-V-T) of InGaN/Si heterostructure revealed that the ideality factor and Schottky barrier height are temperature dependent and the incorrect values of the Richardson’s constant produced, suggests an inhomogeneous barrier at the heterostructure interface. The higher value of the ideality factor compared to the ideal value and its temperature dependence suggest that the current transport is primarily dominated by thermionic field emission rather than thermionic emission. The valence band offset of GaN/β-Si3N4/Si and InGaN/Si heterojunctions were determined by X-ray photoemission spectroscopy. InN QDs on Si(111) substrate by droplet epitaxy and S-K growth method were grown in the third part. Single-crystalline structure of InN QDs (droplet epitaxy) was verified by TEM and the chemical bonding configurations of InN QDs were examined by XPS. The interdigitated electrode pattern was created and (I-V) characteristics of InN QDs were studied in a metal–semiconductor–metal configuration in the temperature range of 80–300 K. The I-V characteristics of lateral grown InN QDs were explained by using the trap model. A systematic manipulation of the morphology, optical emission and structural properties of InN/Si (111) QDs (S-K method) is demonstrated by changing the growth kinetics parameters such as flux rate and growth time. The growth kinetics of the QDs has been studied through the scaling method and observed that the distribution of dot sizes, for samples grown under varying conditions, has followed the scaling function. In the fourth part, InN nanorods (NRs) were grown on Si(111) and current transport properties of NRs/Si heterojunctions were studied. The rapid rise and decay of infrared on/off characteristics of InN NRs/Si heterojunction indicate that the device is highly sensitive to the IR light. Self-aligned GaN nanodots were grown on semi-insulating Si(111) substrate. The interdigitated electrode pattern was created on nanodots using photolithography and dark as well as UV photocurrent were studied. Surface band gaps of InN QDs were estimated from scanning tunneling spectroscopy (STS) I-V curves in the last part. It is found that band gap is strongly dependent on the size of InN QDs. The observed size-dependent STS band gap energy blueshifts as the QD’s diameter or height was reduced.

Afin d’améliorer les performances électriques dans les circuits intégrés en 3D, une large modélisation électromagnétique et une caractérisation haute fréquence sont requises. Cela a pour but de quantifier et prédire les phénomènes de couplage par le substrat qui peuvent survenir dans ces circuits intégrés. Ces couplages sont principalement dus aux nombreuses interconnexions verticales par unité de volume qui traversent le silicium et que l’on nomme « Through Silicon Vias » (TSV).L’objectif de cette thèse est de proposer des règles d’optimisation des performances, à savoir la minimisation des effets de couplage par les substrats en RF. Pour cela, différentes configurations de structures de test utilisées pour analyser le couplage sont caractérisées.Les caractérisations sont effectuées sur un très large spectre de fréquence. Les paramètres d’analyse sont les épaisseurs du substrat, les architectures des vias traversant (diamètres, densités, types de barrières), ainsi que la nature des matériaux utilisés. Des modèles électriques permettant de prédire les phénomènes de couplage sont extraits. Différents outils pour l’analyse de ces effets, sont développés dans notre laboratoire. Parallèlement un important travail de modélisation 3D est mené de façon à confronter mesure et simulation et valider nos résultats. Des stratégies d’optimisation pour réduire ces phénomènes dans les circuits 3D ont été proposées, ce qui a permis de fournir de riches informations aux designers. / In order to improve the electrical performance in 3D integrated circuits, a large electromagnetic modeling and a high frequency characterization are required. This has for goal to quantifiy and predicts the substrate coupling phenomena that can occur in these integrated circuits. These couplings are mainly due to the numerous vertical interconnections existing in a small volume and passing through the silicon, and so called “Through Silicon Vias” (TSV). The objective of this thesis is to propose rules for electrical performance optimization, in order to minimize the coupling effects in RF substrates. For this reason, different test structures configurations used to analyze the coupling are characterized.The characterizations are performed on a very wide frequency spectrum. The analysis parameters are the thicknesses of the substrate, the TSV architectures (diameters, densities, types of barriers), and the nature of the used materials. Electrical models for predicting the coupling phenomena are extracted. Different tools for the analysis of these effects are developed in our laboratory. At the same time, a considerable amount of 3D modeling is conducted to compare measurements with simulations and validate our results. Optimization strategies to reduce coupling phenomena in 3D circuits have been proposed; this has provided a wealth of information to designers.

Cette thèse porte sur l’étude de la croissance auto-organisée de boîtes quantiques d’In(Ga)As sur substrat de silicium visant à l’intégration monolithique d’un émetteur de lumière sur silicium à base d’un matériau semiconducteur III-V. Le développement d’un tel système se heurte à deux verrous majeurs : le premier provient d’un très fort désaccord de maille qui rend difficile l’élaboration de boîtes quantiques d’In(Ga)As sur Si présentant de bonnes qualités structurales et optiques, et le second provient de la nature électronique de l’interface entre In(Ga)As et le Si dont il est prédit qu’elle est de type II et donc peu efficace pour l’émission de lumière. L’approche que nous avons proposée consiste à insérer des BQs d’In(Ga)As dans un puits quantique de silicium dans SiO2, fabriqué sur un substrat SOI. Les effets attendus de confinement quantique dans le puits de Si favoriseraient une interface In(Ga)As/Si de type I. D’un point de vue expérimental, nous avons donc étudié l’influence de différents paramètres de croissance (température de croissance, rapport V/III, quantité d’In(Ga)As déposé, teneur en indium des boîtes quantiques …) sur le mode de croissance et sur les propriétés structurales et optiques des BQs d’In(Ga)As épitaxiées sur substrat de Si(001). Nous avons proposé une interprétation des phénomènes microscopiques qui régissent la formation des boîtes quantiques d’In(Ga)As sur Si en fonction de la teneur en indium. Nous avons aussi montré qu’il est possible de fabriquer des boîtes quantiques d’In0,4Ga0,6As sur Si ne présentant pas de défauts structuraux liés à la relaxation plastique. La luminescence attendue des boîtes quantiques n’a pas pu être obtenue, probablement en raison de deux conditions requises mais antagonistes: la fabrication de boîtes quantiques de très haute qualité structurale (possible uniquement pour de l’In(Ga)As avec une teneur en In inférieure à 50%) et un alignement de bandes à l’interface BQs In(Ga)As/Si de type I (possible théoriquement pour une teneur en In supérieure ou égale à 70%). Ce travail a permis d’enrichir la connaissance et le savoir-faire concernant l’élaboration de boîtes quantiques d’In(Ga)As sur substrat de Si(001) et l’encapsulation de ces boîtes quantiques par du silicium dans un réacteur d’épitaxie par jets moléculaires III-V. / This thesis focuses on the study of the self-organized growth of In(Ga)As quantum dots (QDs) on a silicon substrate. The purpose of this work is to pave the way for a monolithic integration of III-V semiconductor-based light emitter on silicon. One of the big challenges of this project is to overcome the high lattice mismatch between InGaAs and Si which can induce structural defects in the QDs. Another key challenge comes from the expected type II In(Ga)As/Si interface that is detrimental for efficient light emission. In order to solve the “interface type” issue, we suggested to insert the In(Ga)As QD plane inside a thin silicon layer grown on a SOI substrate. Confinement effects of the Si/SiO2 quantum well are expected to raise the X-valley of the Si conduction band above the Γ-valley, leading to a type I interface in both direct and reciprocal space. The influence of different parameters (such as the amount of deposited In(Ga)As, the growth temperature, the V/III ratio and the gallium content...) on the growth mode and on the structural and optical properties of the In(Ga)As QDs grown on Si(001) are experimentally studied. We propose an interpretation of the microscopic phenomena governing the formation of the QDs as a function of gallium content. We finally show the possibility of making In0,4Ga0,6As QDs on Si(001) substrates, these QDs being free of ‘plastic relaxation’-related structural defects. The expected luminescence from the QDs was not obtained probably due to two incompatible conditions: the first, required for growing high structural quality QDs (possible only for In(Ga)As containing less than 50% of In) and the second, essential for maintaining a type I interface band alignment (theoretically possible for an In content greater than 50%). This work is contributing to the understanding of In(Ga)As QDs growth on Si(001) substrates and to the know-how of capping such QDs with silicon inside a III-V molecular beam epitaxy reactor.

No description available.