Indiana University-Purdue University Indianapolis (IUPUI) / The prevalent applications of energy storage devices have incited wide-spread efforts on production of thin, flexible, and light-weight lithium-ion batteries. In this work, lithium-ion batteries using novel flexible paper-based current collectors have been developed. The paper-based current collectors were fabricated from carbon nanotube (CNT)-coated wood microfibers (CNT-microfiber paper). This thesis presents the fabrication of the CNT-microfiber paper using wood microfibers, coating electrode materials, design and assemblies of battery, testing methodologies, and experimental results and analyses. Wood microfibers were coated with carbon nanotubes and poly(3,4-ethylenedioxythiophene) (PEDOT) through an electrostatic layer-by-layer nanoassembely process and formed into a sheet, CNT-microfiber paper. The CNT loading of the fabricated paper was measured 10.1 μg/cm2 subsequently considered. Electrode material solutions were spray-coated on the CNT-microfiber paper to produce electrodes for the half and full-cell devices. The CNT current collector consists of a network structure of cellulose microfibers at the micro-scale, with micro-pores filled with the applied conductive electrode materials reducing the overall internal resistance for the cell. A bending test revealed that the paper-based electrodes, compared to metal ones, incurred fewer damages after 20 bends at an angle of 300o. The surface fractures on the paper-based electrodes were shallow and contained than metallic-based electrodes. The micro-pores in CNT-microfiber paper structure provides better adherence to the active material layer to the substrate and inhibits detachment while bending. Half-cells and full-cells using lithium cobalt oxide (LCO), lithium titanium oxide (LTO), and lithium magnesium oxide (LMO) were fabricated and tested. Coin cell assembly and liquid electrolyte was used. The capacities of half-cells were measured 150 mAh/g with LCO, 158 mAh/g with LTO, and 130 mAh/g with LMO. The capacity of the LTO/LCO full-cell also was measured 126 mAh/g at C/5 rate. The columbic efficiency of the LTO/LCO full-cell was measured 84% for the first charging cycle that increased to 96% after second cycle. The self-discharge test of the full-cell after charging to 2.7 V at C/5 current rate is showed a stable 2 V after 90 hours. The capacities of the developed batteries at lower currents are comparable to the metallic electrode-based devices, however, the capacities were observed to drop at higher currents. This makes the developed paper-based batteries more suitable for low current applications, such as, RFID tags, flexible electronics, bioassays, and displays. The capacities of the batteries at higher current can be improved by enhancing the conductivity of the fibers, which is identified as the future work. Furthermore, fabrication of an all solid state battery using solid electrolyte is also identified as the future work of this project.

Cette thèse présente une étude des applications des groupes de réflexion finis aux problems liés aux réseaux bidimensionnels et aux polytopes tridimensionnels. Plusieurs familles de fonctions orbitales, appelées fonctions orbitales de Weyl, sont associées aux groupes de réflexion cristallographique. Les propriétés exceptionnelles de ces fonctions, telles que l’orthogonalité continue et discrète, permettent une analyse de type Fourier sur le domaine fondamental d’un groupe de Weyl affine correspondant. Dans cette considération, les fonctions d’orbite de Weyl constituent des outils efficaces pour les transformées discrètes de type Fourier correspondantes connues sous le nom de transformées de Fourier–Weyl. Cette recherche limite notre attention aux fonctions d’orbite de Weyl symétriques et antisymétriques à deux variables du groupe de réflexion cristallographique A2. L’objectif principal est de décomposer deux types de transformations de Fourier–Weyl du réseau de poids correspondant en transformées plus petites en utilisant la technique de division centrale. Pour les cas non cristallographiques, nous définissons les indices de degré pair et impair pour les orbites des groupes de réflexion non cristallographique avec une symétrie quintuple en utilisant un remplacement de représentation-orbite. De plus, nous formulons l’algorithme qui permet de déterminer les structures de polytopes imbriquées. Par ailleurs, compte tenu de la pertinence de la symétrie icosaédrique pour la description de diverses molécules sphériques et virus, nous étudions la brisure de symétrie des polytopes doubles de type non cristallographique et des structures tubulaires associées. De plus, nous appliquons une procédure de stellation à la famille des polytopes considérés. Puisque cette recherche se concentre en partie sur les fullerènes icosaédriques, nous présentons la construction des nanotubes de carbone correspondants. De plus, l’approche considérée pour les cas non cristallographiques est appliquée aux structures cristallographiques. Nous considérons un mécanisme de brisure de symétrie appliqué aux polytopes obtenus en utilisant les groupes Weyl tridimensionnels pour déterminer leurs extensions structurelles possibles en nanotubes. / This thesis presents a study of applications of finite reflection groups to the problems related to two-dimensional lattices and three-dimensional polytopes. Several families of orbit functions, known as Weyl orbit functions, are associated with the crystallographic reflection groups. The exceptional properties of these functions, such as continuous and discrete orthogonality, permit Fourier-like analysis on the fundamental domain of a corresponding affine Weyl group. In this consideration, Weyl orbit functions constitute efficient tools for corresponding Fourier-like discrete transforms known as Fourier–Weyl transforms. This research restricts our attention to the two-variable symmetric and antisymmetric Weyl orbit functions of the crystallographic reflection group A2. The main goal is to decompose two types of the corresponding weight lattice Fourier–Weyl transforms into smaller transforms using the central splitting technique. For the non-crystallographic cases, we define the even- and odd-degree indices for orbits of the non-crystallographic reflection groups with 5-fold symmetry by using a representation-orbit replacement. Besides, we formulate the algorithm that allows determining the structures of nested polytopes. Moreover, in light of the relevance of the icosahedral symmetry to the description of various spherical molecules and viruses, we study symmetry breaking of the dual polytopes of non-crystallographic type and related tube-like structures. As well, we apply a stellation procedure to the family of considered polytopes. Since this research partly focuses on the icosahedral fullerenes, we present the construction of the corresponding carbon nanotubes. Furthermore, the approach considered for the non-crystallographic cases is applied to crystallographic structures. We consider a symmetry-breaking mechanism applied to the polytopes obtained using the three-dimensional Weyl groups to determine their possible structural extensions into nanotubes.

No description available.

For biomedical electronics the compatibility to the biological environment should be well-considered. Therefore this paper evaluates dispensed carbon nanotubes (CNT's) on polyimide (PI) foil for conductive tracks and electrodes for flexible, biomedical applications. A CNT based ink is investigated regarding biocompatibility, flexibility, conductivity and suitability for electrode materials with contact to artificial body fluids. The testing methods comprise bending tests with resistance monitoring, adhesion tests and the utilization of dynamic fluidic and electrical load on dispensed structures. The CNT ink showed good bending properties up to 2653 cycles with an average sheet resistance of 32.5 Ohm/sq. A demonstration of biocompatibility using the adherent cell line HFFF2 resulted negatively. No delamination or dissolving effects occurred during exposure to 0.9 % sodium chloride solution.

Ab initio calculations of the electronic structure of freestanding Cu and Na nanowires with a diameter of few atoms are presented. The calculations are based on density functional theory in local density approximation using a Screened Korringa-Kohn-Rostoker-Green's function method. The method was extended for the description of quasi-onedimensional systems. Translational invariance in direction of the wire is assumed. The dependence of the bandstructure and the density of states from thickness and shape of the cross-section is discussed. The quantum confinement of the eigenstates is analysed. By comparing the results of the Na and Cu wires, the influence of the d-electrons is shown. Based on the Landauer theory of transport the conductance is obtained within a Green's function formalism. The numerical description of the conductance is tested for ideal translationally invariant Na and Cu wires. The influence of substitutional transition metal impurities on the electronic structure and the conductance of the 2x2 Cu wire is studied. A spin-dependent discussion is given for magnetic impurities. / Es werden ab initio Berechnungen der elektronischen Struktur freistehender Na- und Cu-Nanodrähte mit einem Durchmesser von wenigen Atomen präsentiert. Für die Berechnung wird eine Screened Korringa-Kohn-Rostoker-Grennsche Funktionsmethode genutzt, die auf der Spindichtefunktionaltheorie in lokaler-Spindichtenäherung basiert. Diese Methode wurde für die Beschreibung von quasieindimensionalen Systemen erweitert. Die Drähte werden als translationsinvariant in Drahtrichtung beschrieben. Es wird die Abhängigkeit der Bandstruktur und der Zustandsdichte von der Dicke und der Form des Querschnitts diskutiert. Das Quantenconfinement der Eigenzustände wird analysiert. Durch den Vergleich der Resultate für den Na- und den Cu-Draht kann der Einfluss der d-Elektronen gezeigt werden. Ausgehend von der Landauer-Theorie des Transports wird der Leitwert im Rahmen eines Greenschen Funktions-Formalismus berechnet. Diese neue numerische Beschreibung des Leitwertes wird an idealen translationsinvarianten Drähten getestet. Es wird der Einfluss von substitutionellen 3d-Übergangsmetall-Störungen auf die elektronische Struktur und auf den Leitwert von 2x2-Cu-Drähten studiert. Im Fall magnetischer Defekte wird dieser Einfluss spinabhängig diskutiert.

The carbon nanotube-based field effect transistor (CNTFET) possesses the potential to overcome limitations of state-of-the-art technologies such as silicon-based complementary metal-oxide-semiconductors. However, the carbon nanotube (CNT) technology is still at its infancy and technology development is still necessary to exploit the CNT properties such as high charge carrier mobility, high current carrying capability, one-dimensional charge transport and their versatile integrability. Within this work significant progress has been achieved scientifically and technologically in the advance of high frequency (HF) CNTFETs for analog applications. According to simulations by others, a technology flow has been developed based on electron beam lithography for bottom gated HF CNTFETs which outperform state-of the art top gate architectures with respect to their parasitic capacitances. Moreover, the impact of electrostatic doping on the CNTFETs has been investigated. In particular, the dynamics of water desorption from the CNTFETs and the related reduction of p-type doping was investigated and the different impact of the n-type dopant polyethylenimine onto the channel region and contact region could be separated for the first time. Furthermore, the impact of doped CNT bundles on the device performance has been studied. It could be shown in detail for the first time, that high off-state source-drain leakage currents can be due to bundled semiconducting CNTs and does not necessarily imply the presence of metallic CNTs. The within the framework of this thesis designed and realized HF CNTFETs are operating in the GHz range with cut-off frequencies up to 14 GHz and maximum frequencies of oscillation up to 6 GHz at a channel length of 280 nm. Moreover, the impact of the spacer between the source-/ drain- to the gate electrode on the HF properties of the CNTFETs has been investigated experimentally for the first time. Simulations by others have successfully confirmed that a symmetrical reduction of the source to gate electrode spacer results in an increased device speed. By asymmetrically reducing the source to gate electrode spacer and in parallel increasing the drain-to-gate electrode spacer the device speed can be further enhanced. Moreover, within this work it has been experimentally indicated for the first time that the device properties of HF CNTFETs can be tuned by different device geometries towards either highest linearity or speed.

No description available.

No description available.

Emerging electronic system architectures follow increasingly 3D integration concepts driven by further miniaturization, increase of performance, decrease of energy consumption, and implementation of further functionality. Following this More than Moore path, trendsetting on-top-of-complementary metal-oxide semiconductor (CMOS) technologies for nanodevices find increasing attention in semiconductor development roadmaps. Nanodevices implemented through nanomaterials such as semiconducting single-walled carbon nanotubes (CNTs) with their proceeded technology readiness level, give additional degree of freedom to upgrade such systems as substrate-independent and post-CMOS compatible technologies are already available. Although, they inherently feature extraordinary properties several technological obstacles are not yet addressed. Pronounced obstacles like inadequate CNT assembly structure, interfering parasitic effects related to CNT/substrate interfaces, as well as insufficient pre-stress state of the CNTs are tackled within this thesis aiming on CNT-based piezoresistive sensors. Following a holistic approach, the activities range from the implementation of chromatography-based length separation of CNTs over wafer-level micro- and nanotechnological process-, module-, and equipment developments towards comprehensive and statistical data analysis. It could be shown, that short CNTs adversely affect integrability and reproducibility, underlined by a 25% decline of the fabrication yield of CNT based field-effect transistors (CNT-FETs) with respect to long CNTs. It furthermore turns out, that performance of CNT-FETs built from long CNTs show significant benefits in terms of subthreshold swing (up to 163%) and hole mobility (up to 300%), which could be explained by suppressed CNT chain formation within the transistor channel. Furthermore, short-channel piezoresistive CNT sensors in FET configuration show a significant drain-induced barrier thinning characterized by a degradation of the subthreshold swing and a threshold voltage roll-off of (−1370± 130) mV · V−1 upon applied drain-source voltage. This device-specific effect enhances the intrinsic strain-sensitivity of the sensor of up to 150% with a maximum measured gauge factor of 800. In this regard, supporting transport simulations underline the importance of the Schottky barrier at the source/CNT junction as the dominating junction for tunneling currents responsible for the gained enhancement. Finally, a technology module was developed, which further reduce parasitic effects such as stick-slip and slack behavior of device-integrated CNTs upon mechanical load by incorporation of layout-determined pre-strain. Utilizing a post-CMOS compatible sacrificial layer approach combined with residual stressed membranes, the integrated CNTs were strained by almost 1% in axial direction. This consequences in an reduced sensor offset determined by a reduction of the detection limit to 30 MPa. In addition this modul was successfully implemented by heterogeneous on-top-of application-specific integrated circuit technologies where CNT-FETs were characterized over an embedded complementary metal-oxide semiconductor multiplexer circuit. Hence, this work displays novelty and provides significant contributions on heterointegrated system-on-chip applications of upcoming nanomaterial-based devices for environmental sensing, condition monitoring, photonic integrated circuits, up to promising architectures for neuromorphic computing and the quantum technology science and application.

Within the scope of this thesis, a theoretical study of liquid flow in graphitic nanopores was performed. More precisely, a combination of numerical simulations and analytic approach was used to establish the special properties of carbon nanotubes for fluid transport: Molecular dynamics flow simulations of different liquids in carbon nanotubes exhibited flow velocities that are 1-3 orders of magnitude higher than predicted from the continuum hydrodynamics framework and the no-slip boundary condition. These results support previous experiments performed by several groups reporting exceptionally high flow rates for water in carbon nanotube membranes. The reason for this important flow enhancement with respect to the expectation was so far unclear. In this work, a careful investigation of the water/graphite friction coefficient which we identified as the crucial parameter for fast liquid transport in the considered systems, was carried out. In simulations, the friction coefficient was found to be very sensitive to wall curvature: friction is independent of confinement for water between flat graphene walls with zero curvature, while it increases with increasing negative curvature (water at the outside of the tube), and it decreases with increasing positive curvature (water inside the tube), eventually leading to quasi frictionless flow for water in a single file configuration in the smallest tubes. A similar behavior was moreover found with several other liquids, such as alcohol, alcane and OMCTS. Furthermore, a theoretical approximate expression for the friction coefficient is presented which predicts qualitatively and semi-quantitatively its curvature dependent behavior. Moreover, a deeper analysis of the simulations according to the proposed theoretical description shed light on the physical mechanisms at the origin of the ultra low liquid/solid friction in carbon nanotubes. In fine, it is due to their perfectly ordered molecular structure and their atomically smooth surface that carbon nanotubes are quasi-perfect liquid conductors compared to other membrane pores like, for example, nanochannels in amorphous silica. The newly gained understanding constitutes an important validation that carbon nanotubes operate as fast transporters of various liquids which makes them a promising option for different applications like energy conversion or filtration on the molecular level.