Дисертації з теми "Nanonets"

Initial attachment to the extracellular matrix (ECM) and consequent spreading is a necessary process in the cell cycle of which little is known. Cell spreading has been well-recognized in 2D systems, however, the native fibrous ECM presents cells with 3D biophysical cues. Thus, using suspended fibers as model systems, we present the development of a novel platform (Cell-STEPs) capable of capturing cell attachment dynamics and forces from the moment a cell in suspension contacts the fiber. Cell-STEPs comprises of a custom glass-bottom petri dish with a lid to deliver a constant supply of CO2 to maintain pH. Fibrous scaffolds are attached in the dish to allow cellular investigations over extended periods of time. We find that cell-fiber attachment occurs in three progressive phases: initial attachment of cell to fiber (phase 0), rapid drop in circularity (phase 1), and increase in cell spread area (phase 2). Furthermore, using iterative inverse methods, forces involved in cell spreading through deflection of fibers were estimated. Our findings provide new insights in attachment biomechanics, including initial sensing and latching of cell to fiber with a negligible or protrusive force, followed by rapid loss in circularity through protrusion sensing at nearly constant spread area and minimal force generation, transitioning to a final phase of increased contractile forces until spread area and force saturation is observed. Also, anisotropic spreading of cells on single and two-fibers are closely related, while cells attached to several fibers take longer and spread isotropically. The Cell-STEPs platform allows, for the first time, detailed interrogations in the discrete and orchestrated adhesion steps involved in cell-fibrous matrix recognition and attachment along with simultaneous measurements of forces involved in cell attachment.
Master of Science

Ce travail se concentre sur l'étude des propriétés piézoélectriques des nanofils semi-conducteurs horizontaux de ZnO placés dans une structure de réseau orientée de manière aléatoire conduisant à la formation de nanonets (NN). Ces nanofils ont été cultivés verticalement par la méthode de synthèse hydrothermale et ont ensuite été transférés sur le substrat souhaité pour la fabrication de dispositifs afin d'effectuer d'autres caractérisations électriques. L'avantage de la synthèse hydrothermale est qu'elle permet de régler et d'obtenir des diamètres variés de nanofils en fonction de la concentration du bain de croissance. Cette capacité a été utilisée ici pour obtenir des échantillons en fonction des exigences conditionnelles finales de l'expérience.Ici, les propriétés piézoélectriques des fils semi-conducteurs ont été étudiées en utilisant l'effet piézoélectrique inverse et l'effet piézoélectrique direct. L'effet piézoélectrique inverse utilise l'entrée électrique pour apporter des changements mécaniques aux fils, tandis que l'effet piézoélectrique direct utilise la déformation mécanique comme entrée pour générer une sortie électrique.Tout d'abord, nous avons étudié le comportement d'un fil de ZnO unique placé latéralement en lui conférant un effet piézoélectrique inverse. Ces mesures ont été effectuées au synchrotron de l'ESRF en collaboration avec le projet LATINO de l'ANR. Par la suite, pour pouvoir transmettre avec succès la déformation mécanique, le NN a été transféré sur un substrat flexible en kapton et la fabrication éventuelle de résistances à base de NN a été effectuée. Ces résistances fabriquées ont été exposées à un environnement de salle blanche pour favoriser la fabrication de dispositifs à motifs de longueur de canal variable.Les caractéristiques mécaniques de ces NN soumis à une déformation par traction ont été étudiées à l'aide d'un MEB et d'un XRD in situ. Ces études ont été menées à l'aide d'un dispositif de traction qui allonge le substrat dans la direction x tout en enregistrant la modification des caractéristiques mécaniques, en collaboration avec le projet Carnot MECANET. En raison de l'augmentation de la force piézoélectrique et du module de Young des fils de ZnO lors de la diminution du diamètre des fils, ces fils de 20 nm de diamètre ont été choisis pour les études piézoélectriques.Enfin, les caractéristiques piézoélectriques de ces dispositifs de résistance NN à base de kapton ont été déterminées en exposant les dispositifs à différentes configurations de déformation, de traction et de flexion, et la sortie électrique correspondante générée a été enregistrée. L'ampleur de la déformation a été modifiée en même temps que la configuration de la déformation pour les tests de traction et de flexion. La liberté d'orientation, de compression et de traction, de la déformation a été permise dans la configuration de la déformation par flexion. Une tendance inverse des caractéristiques électriques a été observée lors de l'augmentation de l'amplitude de la déformation en compression et en traction. Ce comportement a été expliqué par la modification de la hauteur de la barrière Schottky à l'interface métal-semiconducteur. L'évolution du courant et de la courbe caractéristique IV a été étudiée pour les caractéristiques électriques de sortie enregistrées sous déformation mécanique. Une augmentation du courant de 6 ordres de grandeur a été observée ainsi qu'une transformation de la courbe schottky en courbe ohmique IV lors de l'augmentation de l'ampleur de la déformation par compression. Enfin, ces mesures ont montré que ces dispositifs à base de ZnO NN pourraient être utilisés à l'avenir pour des applications de production d'énergie
This work focusses on the study of piezoelectric properties of horizontal ZnO semiconducting Nanowires (NWs) placed in randomly oriented network structure leading to the formation of Nanonets (NN). These Nanowires were vertically grown by hydrothermal synthesis method which were thereafter transferred onto desired substrate for device fabrication to conduct further electrical characterizations. Advantages posed by hydrothermal synthesis is the ability to tune and obtain varied diameter of NWs based on the concentration of the growth bath. This ability was employed here to obtain samples depending on the final conditional requirements of the experiment.Here, the piezoelectric properties of semiconducting NWs were both studied using converse and direct piezoelectric effect. Converse piezoelectric effect employs the use of electrical input to impart mechanical changes to the NWs whereas direct piezoelectric effect uses mechanical deformation as an input to generate electrical output.Firstly, we studied the behaviour of laterally placed single ZnO NW via imparting converse piezoelectric effect. These measurements were conducted at ESRF synchrotron in collaboration with ANR LATINO project. Thereafter, to be able to impart successfully the mechanical deformation, the NN was transferred to flexible kapton substrate and eventual fabrication of NN based resistors was conducted. These resistors fabricated were exposed to clean room environment to favour fabrication of varying channel length patterned devices.The mechanical characteristics of these NN under exposure of traction deformation were studied using in-situ SEM and in-situ XRD. These studies were conducted using traction setup which elongated the substrate in x-direction while recording the mechanical characteristic modification conducted in collaboration with Carnot MECANET project. Owing to the increased piezoelectric and young modulus strength of ZnO NWs upon decrease in NW diameter, these 20 nm diameter NWs were chosen for piezoelectric studies.At the end, piezoelectric characteristics of these kapton based NN resistor devices was determined by exposing the devices to different configuration of strain, traction and bending, corresponding electrical output generated was thus recorded. Magnitude of strain was varied along with the configuration of strain for both traction and bending testing. Freedom in orientation, compressive and tensile, of strain was allowed under bending configuration of strain. Reverse trend in electrical characteristics upon increase in magnitude under compressive and tensile strain orientation was observed. This behaviour was explained using Schottky Barrier Height modification at Metal-Semiconductor interface. Evolution of both current and IV characteristic curve were studied for recorded output electrical characteristics under mechanical deformation. An increase in current by 6 orders of magnitude was observed along with transformation of schottky to ohmic IV curve upon increase in magnitude of compressive strain. Finally, these measurements showed possible future implementation of these ZnO NN based devices for energy generating applications

Les nanofils sont des structures combinant dimensions nanométriques, leur diamètre, et dimension micrométrique, leur longueur, à des propriétés intéressantes pour de nombreux domaines tels que l’électronique, l’optique et la détection de molécules. Cependant, en raison de leur petite taille, ils sont difficiles à manipuler ce qui rend leur intégration au sein de dispositifs complexe et coûteuse. Une solution de contournement à ce problème est de les assembler de sorte à former un réseau de nanofils aléatoirement orientés, aussi appelé nanonet, et qui présente alors une dimension macroscopique. Dans ce travail, nous utilisons comme support de recherche les nanofils d’oxyde de zinc assemblés en nanonets que nous avons intégrés avec succès pour trois applications : les transistors à effet de champ, la détection d’ADN et la détection d’acétone. Nous présentons tout d’abord toute la chaîne de fabrication des dispositifs comprenant la synthèse des nanofils, leur assemblage en nanonet et l’intégration de ces derniers dans des dispositifs selon deux voies totalement différentes. D’une part, nous avons développé l’intégration directe sur des microplateformes chauffantes porteuses d’électrodes, réalisées par un partenaire industriel, pour l’utilisation en tant que capteur de gaz. D’autre part, nous avons mis au point une filière de fabrication complète, qui a été développée et testée au cours de ce travail, pour les transistors à effet de champ. Nous abordons ensuite les performances des différents dispositifs développés. Les transistors à effet de champ que nous avons fabriqués présentent des performances remarquables encore jamais obtenues dans la littérature pour des dispositifs similaires. Ensuite, nous avons pu détecter avec succès l’ADN par fluorescence et mis en évidence l’effet de la densité du nanonet sur cette détection. Enfin, la détection d’acétone sous forme gazeuse a été réalisée sur une large gamme de conditions allant d’une atmosphère sèche à température ambiante jusqu’à une atmosphère très humide à 360°C. Ainsi, ce travail démontre que les nanonets de ZnO présentent des propriétés intéressantes qui offrent des perspectives d’applications dans des domaines aussi variés que l’électronique ou la détection de molécules chimiques ou biologiques
Nanowires are structures combining a diameter of nanometric dimensions and length of micrometric dimension with interesting features for many fields of application such as electronics, optics and molecular detection. However, their small size makes them difficult and costly to integrate into devices. One way to overcome this issue is to assemble them to form a network of randomly oriented nanowires, also called nanonet, which is of macroscopic scale. This work deals with zinc oxide nanonets, which were successfully integrated into three different types of devices: field-effect transistors, DNA sensors and acetone detectors. First, we present the whole fabrication process, from nanowires synthesis to nanonet fabrication and integration into functional devices. Two integration processes were used. The first one involved direct nanonet integration on micro-hotplates with electrodes, provided by our industrial partner, for gaz sensing applications. The second one was a full microelectronic process, which was developed and tested in this work, for the fabrication of field effect transistors. We then discuss the performance of the different devices developed. The fabricated field effect transistors demonstrated remarkable properties which had never been achieved before in the literature for similar devices. We successfully detected DNA by fluorescence and showed the influence of nanowires density on such a sensor. Finally, the electrical detection of gaseous acetone was carried out over a wide range of conditions from dry atmosphere at room temperature to very humid atmosphere at 360°C. This work shows that ZnO nanonets have interesting properties that offer prospects for applications in fields as varied as electronics or the detection of chemical or biological molecules

Thesis advisor: Dunwei Wang
When their electrodes are made of nanomaterials or materials with nanoscale features, devices for energy conversion and energy storage often exhibit new and improved properties. One of the main challenges in material science, however, is to synthesize these nanomaterials with designed functionality in a predictable way. This thesis presents our successes in synthesizing TiSi₂ nanostructures with various complexities using a chemical vapor deposition (CVD) method. Attention has been given to understanding the chemistry guiding the growth. The governing factor was found to be the surface energy differences between various crystal planes of orthorhombic TiSi₂ (C54 and C49). This understanding has allowed us to control the growth morphologies and to obtain one-dimensional (1D) nanowires, two-dimensional (2D) nanonets and three-dimensional (3D) complexes with rational designs by tuning the chemical reactions between precursors. Among all these morphologies, the 2D nanonet, which is micrometers wide and long but only approximately 15 nm thick, has attracted great interest because it is connected by simple nanostructures with single-crystalline junctions. It offers better mechanical strength and superior charge transport while preserving unique properties associated with the small-dimension nanostructure, which opens up the opportunity to use it for various energy related applications. In this thesis we focus on its applications in lithium ion batteries. With a unique heteronanostructure consisting of 2D TiSi₂ nanonets and active material coating, we demonstrate the performances of both anode and cathode of lithium ion batteries can be highly improved. For anode, Si nanoparticles are deposited as the coating and at a charge/discharge rate of 8400 mA/g, we measure specific capacities >1000 mAh/g with only an average of 0.1% decay per cycle over 100 cycles. For cathode, V₂O₅ is employed as an example. The TiSi₂/V₂O₅ nanostructures exhibit a specific capacityof 350 mAh/g, a power rate up to 14.5 kW/kg, and 78.7% capacity retention after 9800 cycles. In addition, TiSi₂ nanonet itself is found to be a good anode material due to the special layer-structure of C49 crystals
Thesis (PhD) — Boston College, 2012
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry

Les réseaux bidimensionnels de nanofils (NFs) d’oxyde de zinc (ZnO) aléatoirement orientés, ou nanonets (pour « nanowire networks »), constituent des nanostructures innovantes et prometteuses pour de nombreuses applications. L’objectif de cette thèse est de développer des nanonets de ZnO en vue d’applications à la détection de molécules biologiques ou gazeuses, en particulier de l’ADN, ceci selon une procédure bas coût et industrialisable. Dans ce but, il est essentiel de bien maitriser les différentes étapes d’élaboration qui sont : (i) le dépôt de couches minces de germination de ZnO sur des substrats de silicium par voie sol-gel, (ii) la croissance de NFs de ZnO sur ces couches de germination par synthèse hydrothermale, et (iii) l’assemblage par filtration sous vide de ces NFs en nanonets de ZnO. Des études approfondies de chacun de ces procédés ont donc été menées. Ces travaux ont permis d’élaborer des couches minces, des NFs et des nanonets de ZnO reproductibles et homogènes dont les propriétés morphologiques sont précisément contrôlées sur une large gamme. Deux protocoles de biofonctionnalisation des nanonets avec de l’ADN ont ensuite été développés et ont abouti à des résultats encourageants mais restant à optimiser. Les nanonets ont également été intégrés au sein de dispositifs fonctionnels et les premières caractérisations électriques ont fourni des résultats prometteurs. A terme, ce travail ouvre la voie à l’intégration collective de NFs de ZnO qui permettrait la réalisation d’une nouvelle génération de capteurs (de biomolécules, de gaz…) à la fois portables, rapides et très sensibles
Two-dimensional randomly oriented zinc oxide (ZnO) nanowire (NW) networks, or nanonets, represent innovative and promising nanostructures for numerous applications. The objective of this thesis is to develop ZnO nanonets for the detection of biological or gaseous molecules, in particular DNA, by using a low cost and scalable procedure. To this end, it is essential to control the different elaboration steps which are: (i) the deposition of ZnO seed layer films on silicon substrates by sol-gel approach, (ii) the growth of ZnO NWs on these seed layer films by hydrothermal synthesis, and (iii) the assembly of these NWs into ZnO nanonets by vacuum filtration. In-depth studies of each of these processes were thus carried out. This work enabled to elaborate reproducible and homogenous ZnO thin films, NWs and nanonets whose morphological properties are precisely controlled over a wide range. Two DNA biofunctionnalization protocols were then developed for the nanonets and led to encouraging results which need however to be further optimized. The nanonets were also integrated into functional devices and the first electrical characterizations provided promising results. In the longer term, this work opens the way to the collective integration of ZnO NWs which would enable the development of a new generation of portable, fast and ultra-sensitive (bio- or gas-) sensors

Un « Nanonet », acronyme pour « NANOstructured NETwork », est défini comme un réseau de nanostructures unidimensionnelles à fort facteur de forme et aléatoirement orientées sur un substrat. Dans ce travail de thèse, une étude approfondie de nanonets à base de nanofils de silicium est présentée en vue d'une intégration dans des capteurs d'ADN. Une méthode de fabrication simple de ces réseaux a tout été d'abord développée afin d'obtenir des nanonets homogènes et reproductibles. La surface des nanofils a ensuite été fonctionnalisée afin de permettre la détection de l'hybridation de l'ADN par fluorescence. Les capteurs ainsi réalisés présentent une excellente sélectivité et une meilleure limite de sensibilité que des substrats plans. Les propriétés électriques des nanonets de silicium ont également été étudiées ce qui a mené à la description des mécanismes de conduction de ces réseaux. Ainsi, il a été démontré que le comportement électrique de ces structures est dominé par les nombreuses jonctions nanofil-nanofil et suit la théorie de la percolation électrique. De plus, une procédure d'optimisation de ces jonctions a finalement permis de stabiliser les propriétés électriques des nanonets de silicium.Ces réseaux possèdent donc des propriétés remarquables provenant des constituants individuels, les nanofils, qui présentent une surface spécifique élevée, mais également de leur structure en réseaux aléatoires offrant la possibilité de les manipuler simplement et à bas coût à l'échelle macroscopique. Ces travaux ouvrent la voie à l'intégration des nanonets de silicium dans des capteurs d'ADN reposant sur la détection électrique
A "nanonet", acronym for "NANOstructured NETwork", is defined as a network of one-dimensional nanostructures with high aspect ratio and randomly oriented on a substrate. In this work, a comprehensive study of nanonets based on silicon nanowires is presented for integration into DNA sensors. First, a simple method for the network fabrication has been developed in order to obtain homogeneous and reproducible nanonets. Then, the nanowire surface has been functionalized, so that the DNA hybridization detection is possible by fluorescence. The elaborated sensors exhibit excellent selectivity and a better sensitivity limit than planar substrates. The electrical properties of the silicon nanonets have also been investigated which resulted in the description of the conduction mechanisms of these networks. It has been shown that the electrical behaviour of such structures is ruled by the numerous nanowire-nanowire junctions and follows the electrical percolation theory. Moreover, an optimization procedure of these junctions has allowed stabilizing the electrical properties of silicon nanonets.Therefore, these networks have attractive characteristics which arise from the individual components, the nanowires with a high specific surface, but also from the structural properties of the network itself which can be simply manipulated, at a low cost, on macroscopic scales. This work paves the way for the integration of silicon nanonets into DNA sensors based on electrical detection

In this work we made a review of how a multi-probes microscope using Atomic Force and Near Field Scanning Microscopy works. Currently, the Nanonics Multiview 4000 instaled at the Materials Caracterization and Microscopy Laboratory (LCMMAT) is not completly working. Nowadays, we are able to do Atomic Force Microscopy (AFM) and reflection and transmission Scanning Near Field Microscopy (SNOM) measurements. This kind of microscope have three probes which are able to do simultaneaous mesurements of AFM, C-AFM, SNOM, Raman Microscopy and nanolitography. It is the first multi-probe microscope to be instaled in Latin America. This work consists in studying the structure of this kind of microscope, how does it make AFM and SNOM measurements and how to analise them. We study the different electronic circuits which are used in this kind of microscopes and we compare both optical and tuning-fork feedback. It was explain step by step how to do and AFM and SNOM measurement. We study the processing and analise of this measurements. Finally, we made some different measurements using this tecniques. Some of this measurements were compared with that found in references in order to try to find some possible aplications which could be useful for future researches at our laboratory.
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Neste trabalho realizamos uma revisão do funcionamento do Microscópio Raman Confocal Multipontas com Campo Próximo e Força Atômica modelo Multiview 4000 da empresa Nanonics. Atualmente, o microscópio Multiview 4000 do Laboratório de Caracterização e Microscopia de Materiais (LCMMAT) ainda não se encontra operando aos 100%. Ele encontra-se em fase de montagem, estando disponível hoje em dia para uso só o Microscópio de Força Atômica (AFM) e o Microscópio de Campo Próximo (SNOM) nos modos reflexão e transmissão. Este modelo de microscópio, o qual possui três ponteiras que são capazes de fazer medidas em simultâneo de AFM, C-AFM, SNOM e microscopia Raman Confocal, alem de poder fazer nanolitografia, é o primeiro a ser instalado na America Latina. Durante a realização do presente trabalho, estudamos a estrutura do microscópio, como ele realiza as medidas destas duas técnicas e como elas são feitas. No estudo estrutural do Microscópio foram descritos os princípios físicos que são usados para a formação da imagem, alem dos diferentes tipos de circuitos eletrônicos usados em equipamentos de este tipo. Explicou-se passo a passo como são feitas as medidas de AFM e de SNOM. Estudamos também como é feito o analise e o processamento das imagens. Finalmente foram mostradas algumas imagens que foram feitas usando o microscópio, e comparou-se com alguns resultados encontrados na bibliografia a fim de encontrar possíveis aplicações de cada uma das amostras aqui mostradas.

Un nanonet possède des propriétés remarquables qui proviennent non seulement des propriétés intrinsèques de chaque nanostructure mais aussi de leur assemblage en réseau ce qui les rend particulièrement attractifs pour de multiples applications, notamment dans les domaines de l’optique, l’électronique ou encore le biomédical. Dans ce travail de thèse, des nanonets constitués de nanofils de silicium ont été intégrés pour la première fois sous forme de transistors à effet de champ avec une grille en face arrière. La filière technologique développée est parfaitement compatible avec une production des dispositifs en masse, à bas coût et à grande échelle pour un budget thermique n’excédant pas 400°C. Des avancées technologiques majeures ont été réalisées grâce à la maîtrise du frittage des jonctions entre nanofils, de la siliciuration des contacts et de la passivation des nanofils avec de l’alumine. Les transistors à nanonets fabriqués présentent des caractéristiques électriques excellentes, stables sous air et reproductibles qui sont capables de concurrencer celles des transistors à nanofil unique. Une étude approfondie de la percolation par des mesures expérimentales et des simulations Monte-Carlo a mis en évidence que la limitation de la conduction par les jonctions entre nanofils permet d’améliorer considérablement les performances électriques. Après une intégration des dispositifs sous forme de biocapteurs, il a été montré que les transistors sont sensibles électriquement à l’hybridation de l’ADN. Bénéficiant d’un procédé de fabrication compatible avec l’industrie de la microélectronique, une intégration 3D de ces transistors à nanonet sur un circuit de lecture peut alors être envisagée ce qui ouvre la voie à des biocapteurs portables, capables de détecter l’ADN en temps réel et sans marquage. De plus, la flexibilité mécanique et la transparence optique du nanonet offrent d’autres opportunités dans le domaine de l’électronique flexible
A nanonet exhibits remarkable properties which arises from, not only, the intrinsic properties of each nanostructure but also from their assembly into network which makes them particularly attractive for various applications, notably in the field of optics, electronics or even biomedical. During this Ph.D. work, silicon nanowire-based nanonets were integrated for the first time into field effect transistors with a back gate configuration. The developed technological process is perfectly suitable with a large-scale and massive production of these devices at low cost without exceeding a thermal budget of 400°C. Major technological breakthroughs were achieved through the control of the sintering of nanowire junctions, the contact silicidation and the nanowire passivation with alumina. The as-fabricated nanonet transistors display outstanding, air stable and reproducible electrical characteristics which can compete with single nanowire-based devices. An in-depth study of percolation using experimental measurements and Monte-Carlo simulations highlighted that the conduction limitation by nanowire junctions allow to enhance drastically the electrical performances. After device integration into biosensors, it has been shown that transistors are electrically sensitive to DNA hybridization.Beneficiating from a fabrication process compatible with the microelectronic industry, a 3D integration of these nanonet-based transistors onto a readout circuit can therefore be envisioned which opens new avenues for portable biosensors, allowing direct and label-free detection of DNA. Furthermore, mechanical flexibility and optical transparency offer other opportunities in flexible electronic field

Les réseaux aléatoires de nanofils, parfois appelés nanonets, pourraient être des candidats prometteurs pour l’intégration 3D de biocapteurs sur CMOS. Dans cette thèse nous présentons les résultats de caractérisations et de simulations de transistors à effet de champ à base de nanonets de silicium (Si NN-FET). Nous montrons que les résultats de mesure ne peuvent pas s’interpréter sans prendre en compte les dispersions au sein du nanonet.Les caractéristiques électriques statiques des Si NN-FET ont été mesurées en fonction des paramètres géométriques (dimension du canal et densité de nanofils) sur un grand nombre de composants de façon à disposer de grandeurs statistiquement significatives pour les paramètres électriques principaux (mobilité apparente à bas champ, facteur d’idéalité de la pente sous le seuil et tension de seuil) qui sont extraits grâce à un modèle compact. Nous évaluons en parallèle les variations théoriques de ces mêmes paramètres en utilisant la théorie de la percolation et des simulations Monte Carlo. Par rapport aux approches généralement utilisées dans la littérature pour des réseaux percolants, l’originalité de nos simulations est de prendre en compte l’effet de champ ainsi que les dispersions. Les dispersions en tension de seuil se sont avérées essentielles pour comprendre la dépendance expérimentale des caractéristiques électriques avec les caractéristiques du réseau. L’analyse du bruit basse fréquence des Si NN-FET permet l’estimation de la variation de l’aire électrique du nanonet avec la densité. L’étude de la variation en température des caractéristiques électriques des Si NN-FET met en évidence l’activation en température des jonctions entre nanofils. La relation inattendue de la mobilité avec la température fait soupçonner une dispersion de la hauteur de barrière des jonctions, hypothèse validée par les simulations Monte Carlo
Random networks of nanowires, sometimes called nanonets, could be promising candidates for the 3D integration of CMOS biosensors. In this thesis we present characterization and simulation results of field effect transistors based on silicon nanonets (Si NN-FET). We show that measurements cannot be understood without account for dispersions within the nanonet.The static electrical characteristics of these Si NN-FETs were measured for different geometric parameters (channel length and nanowire density) on a large number of devices, in order to obtain statistically significant orders of magnitude for the main electrical parameters (apparent low field mobility, subthreshold slope ideality factor and threshold voltage), which were extracted by means of a compact model. In parallel, the theoretical variations of these parameters were evaluated using percolation theory and Monte Carlo simulations. Compared to the usual approaches found in the literature for percolating networks, the originality of our simulations is to take into account both field-effect and dispersions. Threshold voltage dispersions proved to be essential to understand the experimental dependence of electrical parameters with network parameters. The analysis of Si NN-FET low frequency noise (LFN) made it possible to estimate the variation, with nanowire density, of the electrical area of the nanonet. From the temperature variation of Si NN-FET electrical parameters, it was found that inter-nanowire junctions were thermally activated. The unexpected variation of mobility with temperature suggests that junction barrier heights are widely dispersed, an assumption which was validated by the Monte Carlo simulations

碩士
國立雲林科技大學
機械工程系碩士班
99
This study is to develop and fabricate the flexible carbon nanotubes nanonets (CNNs) electrodes. First, the multi-wall carbon nanotubes (MWCNTs) powder was used to fabricate the CNTs ink by using the hydrophilic treatments. Then, the CNTs ink was coated onto the paper substrate. Finally, after a thermal sintering process, the flexible CNNs electrodes were completed. In this study, (1) H2SO4/HNO3 mixed acid and (2) sodium dodecyl sulfate (SDS) were used for the hydrophilic treatments, respectively. The Raman spectra result shows that the mixed acid of H2SO4/HNO3 can damage the CNTs structure to reduce the G/D ratio (IG/D) of CNTs. For different treatment recipes results, the IG/D ratios of CNTs samples were decreased from 2.7 (CNTs raw material) to 1.98. However, the IG/D ratios of CNTs samples which treated by using SDS and an ultrasonication were increased. The IG/D ratios of CNTs samples were increased from 2.7 (CNTs raw material) to 3.96 (by an ultrasonication for 6 hours). Then, the CNTs ink made by using the mixed acid of H2SO4/HNO3 at 50 oC for 12 hours was coated onto the paper substrate as the thin CNNs. The average sheet resistance (Rs) of CNNs was 310 Ohm/sq.. After a thermal sintering process at 300 oC for 40 min, the average Rs of CNNs was reduced to 174 Ohm/sq.; The average Rs of CNNs treated by using SDS and an ultrasonication for 6 hours was 189 Ohm/sq.. After a thermal sintering process at 300 oC for 20 min, the average Rs of CNNs was reduced to 153 Ohm/sq.

碩士
國立雲林科技大學
機械工程系碩士班
100
This purpose of study is to fabricate and develop the flexible carbon nanotubes nanonets (CNNs) devices. Firstly, the carbon nanotubes (CNTs) are sorted and dispersed in the sodium dodecyl sulfate (SDS) solution by using an ultrasonic homogenizer. Next, the CNNs thin film is coated on the glass substrate by dip-coating method. Then, the CNNs thin film coated on the glass substrate is transferred and printed on the EVA/PET substrate by a laminator. Finally, the CNNs/EVA/PET film is cut to form as a strain gauge. In this study, many work tasks include with (1) CNTs sorting, dispersion, (2) CNNs thin film dip-coating, transfer printing, and (3) CNNs strain gauge fabrication are done and completed. In this result, a 0.5 mg/ml of CNTs can be dispersed in the 2 wt% SDS solution without agglomeration. After the dip treatment of 400 times under a dip-coating rate of 20 mm/min, a well uniform coated CNNs thin film with a sheet resistance of 0.66 kΩ/square is found. In addition, the CNNs can be transferred successfully on the flexible EVA/PET substrate by a lamination process at a process temperature of 105 oC for 20 seconds. Finally, the CNNs/EVA/PET strain gauge is fabricated and demonstrated. The gauge factor (GF) of CNNs/EVA/PET strain gauge is measured and is 4.6 after a tensile test and is great than the gauge factor of commercial metal strain gauge.

碩士
國立高雄應用科技大學
機械與精密工程研究所
98
This study presents a novel flexible strain sensor for real time bone strain sensing with higher resolution, and the material for strain sensing is Single-walled Carbon Nanonets (SWCNNs) that encapsulated between two layers of Parylene-C. All the micro-fabrication were compatible with standard IC process. Also, the prototype has been tested with commercial strain gauge using tensile testing. The gauge factor of biomedical strain sensor is over 4.5, and it is twice of commercial strain sensor. The gauge factor is small when the growth time is more, because the dense of SWCNNs can influence gauge factor. Also, the gauge facter is large when the width is less by the uniform SWCNNs.

碩士
國立高雄應用科技大學
機械與精密工程研究所
99
This study presents a biocompatible strain sensor, which sensing material, carbon nanonets, growing by alcohol catalytic chemical vapor deposition (ACCVD) which provided by National Nano Device Laboratories (NDL). And by MEMS fabrication process technology, we used Parylene-C covering the top of sensor as the water layer and the bottom of sensor as the package structure. The prototype sensor has been tested by using tensile testing equipment. The gauge factor of proposed strain sensor is about 4.28, it is 1.8 to 2.0 times of commercial strain sensor. As for the wireless monitoring function, it is based on radio frequency identification system (RFID) and BASIC Stamp chip to control motion of the system. The sensor system can real time reading the data by the RFID wireless transmission system.

碩士
國立成功大學
化學工程學系碩博士班
100
In this thesis, it studies on the large area nanonets derived from silver nanowires and its application to Surface-Enhanced Raman Scattering. The contents include two parts: In first section, the nanonets derived from silver nanowires deposited on substrates was investigated and characterized. Silver nanowires would be spontaneously synthesized on substrate without any driving force such as potential, chemical grafting, surface modification. The scanning electron microscope (SEM) results revealed that the formation of holes on nanonets when the ITO glass was used as substrates. In addition, the UV/vis spectra showed that the surface plasmon resonant between silver substrate and silver nanowires. The crosslink of adjacent silver nanowires could be analyzed by annealing the nanonets. It was found that the weight flux of silver nanowires, substrate materials, and silver nanowires interval could affect the surface plasmon resonance. In the second section, the silver nanowires and silver substrate sandwich-like structure was applied in analysis of Rhodamine 6G(R6G) interaction with different polar solvents. From the results of Infrared spectroscopy and Raman spectra, solubility could be affected by solvents polarity and dielectric constant. The hydroxyl functional group of solvents could form hydrogen bond and then it could enhance the Raman signal. In addition, in R6G sensing, it could achieve a limit of detection sensitivity of 10-9M and enhancement factor was 107. Besides, the Raman signal and R6G concentration showed a good linear relationship. This characteristic could be on behalf of the enhanced substrate had good sensitivity and selectivity in R6G sensing.

博士
國立成功大學
系統及船舶機電工程學系碩博士班
100
Nano-transfer printing (nTP) is increasingly used for micro-fabrication of nano-scale materials onto flexible plastic substrates. This thesis reports a novel nTP process (called as “polymer tape bonding”) for single-walled carbon nanonets (SWCNNs) for use in strain sensors and flexible field effect transistors. Traditional SWCNNs grown on silicon substrate by alcohol catalytic chemical vapour deposition (ACCVD) can serve as strain sensing elements in strain sensors and nano electromechanical system (NEMS) sensors, but ACCVD is not well suited to the task. To improve SWCNN fabrication, this paper deposits a Parylene-C thin film on SWCNNs for transfer-printing onto flexible plastic substrates with polyimide tape. Quantification of the fabricated SWCNN strain sensing ability (gauge factor) is performed by comparing two specimens with different pattern features and substrates. Gauge factor is measured by tensile testing. SWCNN density variations relative to the observed gauge factors are discussed. Results show SWCNN gauge factors range from 1.46 to 8.22 depending on the substrate and pattern width. It is further observed that the gauge factor of the presented SWCNN thin film increases when the width of the SWCNN decreases to the low micro-dimensions, i.e. below 40m, indicating a significant scaling factor. Also, the presented nTP method is used to fabricate the SWCNN flexible top-gated field effect transistor on PEN and polyimide base with standard integrated circuit (IC) compatible processes. Finally, electric characteristics of the flexible SWCNN top-gate thin film transistors are measured by the I-V measurement, the SWCNN TFT achieved the averaged mobility of 53.89cm2/Vs with applied Vds=0.1V as a p-type FET, and the mobility is ranged from 30.10 to 96.85cm2/Vs. and the on-to-off ratio of the current devices is approximately 100.

碩士
國立高雄應用科技大學
機械與精密工程研究所
98
This research successfully synthesized high-quality single-walled carbon nanonets by low pressure thermal CVD. Using the Immersion method to make different proportions of acetic acid cobalt and molybdenum acetate evenly adsorb on the silicon wafer, and then explore their differences. We use field emission gun scanning electron microscopy, four-point probe and the BTS electrical measurement system to measure the density of carbon nanonets. The results show that, when acetate cobalt and molybdenum acetate have higher concentration, the carbon nanonets have higher density When the change in the thickness of silicon dioxide, the results showed that the more thickness, the higher density of carbon nanonets. Using the CARO acid-wash carbon nanonets of 0.08 wt% and 0.1 wt% respectively to found that the resistance values decreased significantly in the thickness of 10000Å. By the Raman spectroscopy we can know the graphitization ratio that we use CARO to acid-wash carbon nanonets before and after raised to 0.88 from 0.80 in the concentration of 0.08 wt%. And the graphitization ratio raised to 0.90 from. 0.86 in the concentration of 0.1wt%

碩士
國立成功大學
光電科學與工程學系
102
Silicon nanonet field-effect transistors are fabricated using top-down approach with the help from oxygen plasma-treated Nanosphere Lithography. Cr nanonet is first deposited on top of a silicon-on-insulator (SOI) wafer and silicon nanonet membrane can be obtained after the following silicon wet or dry etches. The sensor region and the electrons are defined using regular photolithography process and the device is operational after deposit the Ti contact pads. The electrical characteristics are measured and important parameters are subsequently extracted.In the future, we will finish fabricating the devices that can be operational using a liquid-gate electrode.We believe this device will be applied as economic sensor to detect chemical- or biological species in the near future.

碩士
國立成功大學
微電子工程研究所
103
In this thesis, silver nanowires (NWs) self-assembled to Ag nanonet via ethylene glycol (EG)-assisted route is studied. Two different approaches in adding EG solution to assist Ag NWs self-assembling to form Ag nanonet were conducted. The possible mechanism and theory of Ag nanonet self-assembling are discussed. The self-assembled Ag nanonet was annealed to form fused junctions in those overlap area between Ag NWs using quartz tube furnace. Thermal budget of this annealing to form fused junctions in Ag nanonet is studied. Sheet resistance and degree of AZO film’s transparency with or without Ag nanonet embedded are evaluated. The first part of results indicate that spray EG solution and then drip Ag NW solution on a substrate do help the self-assembling. When Ag NW solution drip onto the substrate with EG drops, it will slightly mix with EG drops. When the substrate temperature slowly increases to 40°C, the ethanol solvent evaporates first. This evaporation helps Ag NWs move slightly, the movement stops at the edges of the EG drops. (Note: EG does not evaporate easily at 40°C.) At the moment when the entire edges of EG drops surrounded by Ag NWs, the self-assembled Ag nanonet can be formed. In addition, if the EG drops contains poly(vinylpyrrolidone) (PVP), it is more effective to help the self-assembling. At 320°C, the annealing time required to fuse Ag NWs depends on the density of the Ag NWs in the nanonet and also depends on the method used for self-assembling. The time needed for fusing NWs is 10 min if drip Ag NW solution directly on the substrate. It takes 11 min to fuse together if the substrate was pre-sprayed with EG drops, and takes 31 min to fuse if the pre-sprayed EG drops contain small amount of PVP. The sheet resistance of the AZO film with fused Ag nanonet embedded has much lower sheet resistance than that without. In one particular case, an AZO film with fused Ag nanonet embedded exhibits transmittance of 58.15% and sheet resistance of 41.27 Ω/sq. The AZO sheet resistance with fused Ag nanonet embedded is about only 2.53% of that without one. The fused NW of the nanonet has a larger diameter than the original NW and results in lower transmittance.

碩士
國立成功大學
光電科學與工程學系
103
In this dissertation, we will demonstrate how to fabricate metallic metamaterials and Silicon nanonet Field-Effect Transistors (FETs) using Nanosphere-related lithography techniques. To fabricate metallic metamaterials, we have included techniques such as angled-exposure and angled deposition in Nanospheircal-Lens Lithography (NLL). Planar metamaterials consisting of nanoparticles or nanoholes can be successfully fabricated in large-scale. Plasma-treated Nanosphere Lithography is used to fabricate the etching mask for Silicon nanonet FETs. The patterning of the nanonet FETs is achieved by dry etch method. The minimum width of the nanonet can be as small as 103 nm. Silicon nanonet covering an area of 15μm x 15μm with connecting electrodes can be successfully fabricated using standard semiconductor fabrication procedures. Preliminary results from the electrical measurements of these devices are also presented. Various parameters, including the width and length of the nanonet, and their effects on the electrical properties of the devices are also studied. In the future, we will test how these devices can work in the liquid environment for biosensing applications.

碩士
國立成功大學
航空太空工程學系碩博士班
97
Carbon nanotube, a kind of different Carbon allotrope, with unique mechanical and electrical science identities, is the core that many researches focus on. Between different nano devices, carbon nanotube has outstanding potency. Organic solar energy cells possess many advantages: flexibility, low-cost, and easy processing technologies and so on, has distinctive position in solar energy cells. This research using Alcohol Catalytic Chemical Vapor Deposition to develop growth of single-wall carbon nanotube and combine with organic polymer thin film, to produce Heterojunction Solar Cell that contains nano structure. Based on the reveal, which showed that the carbon nanotube in this study is single wall carbon nanotube, whose Semiconductor is bi-polar, and is active layer in organic solar cell. Making e the elements to proceed series Electrical property and optics, the study showed that conversion efficiency is 0.012%, short-circuit current density (Jsc) is 0.132mA/cm2, open-circuit voltage(Voc) is 0,23V, and Fill Factor(FF) is 0.39. The compactness of carbon nanotube will affect the Efficiency of cell. Besides, it’s the study for the process of Alcohol Catalytic Chemical Vapor Deposition growing single wall carbon nanotube, put NH3 in to carry out Surface modification of carbon nanotube, observing the varietion of Morphology and optics, to produce solar energy cell; and further, probe into the alterations of electrical propert