In this work, carbon nanotubes (CNTs) have been synthesized by microwave chemical vapor deposition technique using Ni as catalyst and at different experimental parameters. Catalysts Ni plays an important role in the process of synthesizing carbon nanotubes. Sputtered Ni film can agglomerate into uniformly distributed nanometer size particles, which can be employed to assist the growth of carbon nanotubes. The effect of Ni catalyst on CNTs growth have been investigated and an optima Ni thickness has been found. There are series experiments performed in order to improve the CNT growth environment and a characteristics for CNTs under the condition at 30 torr, 800¢J, 600W and ¡V 350V was observed. The growth characteristics was evaluated with TEM, SEM, Raman and FTIR. From Raman spectra, the degree of graphitization is proportional to growth temperature and microwave power. In addition to extending the growth time, the length of CNT did not increase.

In this thesis, we calculate the energy states of one electron attracted by an impurity(hole) in finite carbon nanotubes. Comparing our calculations with Pederson¡¦s result, the ground state energy of the electron (attracted by an impurity in finite carbon nanotube) is close to the exciton binding energy in infinite carbon nanotube, but there is no bound state in short length carbon nanotubes. Further more, we study energy states under an uniform magnetic along the z axes. The energy levels of the impurity vary in periods of an unit magnetic flux. And some of the energy states are degeneracy in short length carbon nanotubes but not in long length carbon nanotubes.

One-dimension (1D) nanostructures such as wires, rods, belts and tubes have become the focus of intensive researches for investigating structure-property relationships and related scientific and technological applications. Few-walled carbon nanotubes (FWNTs), a special type of small diameter multi-walled carbon nanotubes with superb structural perfection, are first discovered in our laboratory and systemically studied in this dissertation, including the synthesis by chemical vapor deposition (CVD) method, the purification and their applications. Moreover, iron phosphide nanorods/nanowires with controlled structures have been synthesized in solution phase and their magnetic properties have been investigated. The first parts of this dissertation are mainly focused on the studies of FWNTs synthesized by CVD method using binary catalyst Co (or Fe) with Mo (or W) supported on MgO made by modified combustion method. The structures of as-grown FWNTs can be controlled by three basic growth parameters: temperature, catalyst composition and carbon feeding rate. It is found that the as-grown FWNT materials prepared from W-containing catalysts are much more easily purified than those from Mo-containing catalysts. Both raw and purified FWNTs show enhanced electron field emission characteristics compared to other current commercial nanotubes. The highly pure FWNTs are then used to prepare composite materials with polymers and noble metal nanocrystals. Furthermore, the structures of FWNTs are attempted to be controlled by adjusting the growth parameters of carbon monoxide CVD. Highly pure DWNTs (over 95%) are obtained and well characterized by TEM, Raman and fluorescence spectrum. The optical properties of DWNTs and their application in bio-imaging are primarily investigated. In addition, conducing films are fabricated using highly pure FWNTs and the relationship between the structure and the conductivity is surveyed and further possible improvements are discussed. The second parts of this dissertation describe a solution-phase route for the preparation of single-crystalline iron phosphide nanorods and nanowires. The mixture of trioctylphosphine oxide (TOPO) and trioctylphosphine (TOP) which are commonly used as the solvents for semiconductor nanocrystal synthesis is not entirely inert. TOP serves as phosphor source and reacts with Fe precursors to generate iron phosphide nanostructures with large aspect ratios. In addition, the morphology of the produced iron phosphide structures can be controlled by the ratio of TOPO/TOP. A possible growth mechanism is discussed. / Dissertation

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Thorough understanding of the electronic and optical properties of single-walled carbon nanotubes (SWCNTs) will no doubt benefit future technological applications. Since the discovery of band gap photoluminescence from isolated semiconducting SWCNTs, significant progresses in studying the optical properties of SWCNTs have been made (e.g. linear polarization along the tube axis for the absorption and emission of light, excitonic nature in SWCNT excitation). However, there are still several controversial parameters of SWCNTs (e.g. quantum efficiency, absorption cross section, radiative lifetime, and Auger recombination lifetime). With the advancement in SWCNT sample preparation, studies of SWCNT intrinsic properties have shifted from ensemble to a single tube level, in which the ambiguities in elucidating intrinsic properties posed by the assortment of different tube species can be minimized. By examining individual SWCNTs suspended in air, in contrast to micelle-encapsulated SWCNTs, we believe that the environmental effects can be reduced. This thesis will demonstrate the capability of doing spectroscopy on a single semiconducting air-suspended SWCNT. In continuous-wave excitation, the photoluminescence excitation map and high resolution photoluminescence (PL) image of a SWCNT can be constructed, and PL polarization is proven. Quantum efficiency of 5% is experimentally estimated for (9,8) and (10,8) chiral SWCNTs. Pulse excitation allows us to study the intrinsic exciton dynamics of a SWCNT. To gain insight into exciton nonlinear decay processes, PL saturation in pump power dependence measurement is investigated and compared to the simulated results from stochastic models of exciton dynamics. Femtosecond excitation correlation spectroscopy with 150 fs time resolution is employed to time-resolve the PL of a single tube suspended in air. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2008-08-29 13:10:49.045

This thesis describes the development and testing of a range of electrodes designed to be able to measure electrical current produced by the respiration of bacteria in direct contact with the electrode surface. The electrodes are designed to directly wire into redox processes in the cytoskeleton of the bacteria so that electron transfer can be measured in real time without the need for solution based mediator molecules. The rate of electron transfer from the bacteria is enhanced by nanostructuring the surface of graphite electrodes with vertically aligned single and multiwalled carbon nanotubes (CNTs) and covalently coupling mediator molecules to the CNT tips. A selection of the prepared electrodes are tested with the non-electrogenic bacteria Proteus vulgaris and Bacillus subtilis to demonstrate the potential of the electrode designs to be used with a wide range of microbial species.

Le but de cette thèse est de caractériser des transistors à nanotube de carbone (CNTFETs) par des mesures de transport couplées aux techniques électriques dérivées de la microscopie à force atomique (microscopie à force électrostatique et microscopie à sonde de Kelvin). Ici, les CNTFETs sont utilisés comme détecteur de charges locales injectées directement par une pointe AFM à une centaine de nanomètres du nanotube. La réponse électrique à cette perturbation de charges est relevée par la mesure des caractéristiques de transfert et indique un effet de grille opposé à celui attendu par le signe des charges injectées. L'imagerie des potentiels de surface du dispositif permet l'observation de la délocalisation sur toute la longueur du nanotube de charges de signe opposé à celles de la tâche d'injection. De plus, suite aux injections de charges, un phénomène périodique résonant apparaît dans les caractéristiques de transfert. Nous proposons une explication en termes d'effet tunnel inélastique lors de l'injection des porteurs dans le CNTFET à travers le contact Schottky en présence de charges à l'interface nanotube/SiO2. / The aim of this thesis is to characterize Carbon Nanotube Field Effect Transistors (CNTFETs) with both electronic measurements and electrical scanning probe microscopy (Electrostatic Force Microscopy and Kelvin Force Probe Microscopy). Here, CNTFETs are used as a detector of charges. Theses charges are directly injected from an AFM tip to the silicon dioxide layer in the vicinity of the nanotube (typically 200e at 200 nm). Electrical response to this perturbation shows an opposite gate effect with one expected from the sign of injected charges. Surface potential imaging leads to the observation of a delocalization ail along the nanotube of opposite charges in comparison with those injected. Moreover, after charge injection, periodical resonance phenomena appear in transfer characteristics. An explication is given based on inelastic tunnel effect through the Schottky contact during carriers injection in the CNTFET when charges are stored at the nanotube/SiO2 interface.

The aim of the thesis is to fabricate Schottky contact carbon nanotube field effect transistor (CNFET) using the dielectrophoresis (DEP) to resolve the alignment issue and show its transistor behaviour. The work presented is a combination of fabrication and simulation of CNFET. Fabrication of the device electrode had been done using the electron beam lithography to achieve a channel length of 150nm and analysis was done on an optical microscope, SEM, AFM and Raman spectroscopy. Second half of the thesis provides a solution to “bottleneck communication” between microprocessor and memory to increase the computation for applications like AI, IoT etc and 3D monolithic memories. As a solution, we propose a novel CNFET based processing in-memory architecture using a novel CNFET dual port single-ended SRAM bit cell. The combination of the CNFET and processing in-memory can be a new phase for memory and computation.

No description available.