In this study, the design and fabrication of a monolithic InP-based 1550-nm photonic-crystal surfaceemitting laser (PCSEL) is reported. The device is composed by an InGaAsP multi-quantum well (MQW) active layer and InP photonic crystal (PhC) formed by metal organic chemical vapour deposition (MOCVD). A theoretical study based mainly on the Fourier modal method using Stanford Stratified Structure Solver (S 4) and finite element analysis using COMSOL Multiphysics was carried out in order to optimize the emission at 1550 nm due to the two-dimensional band-edge resonance effect at the Γ point.The device design and modeling, materials testing (annealing and MOCVD regrowth), process optimization and the fabrication of light emitting diodes (LEDs) based on the same structure as the PCSELs (without the PhC) is reported. The fabricated devices show a low series resistance of 8.19 Ω and a turn-on voltage of 0.84 V. The average differential output power is 41 mW/A with an electroluminescent peak at 1511 nm. The full assembly of the final PCSEL devices is beyond the scope of the present thesis and corresponds to an ongoing project expected to be finalized within the coming year. However, detailed guidelines and fabrication instructions, including the manufacturing of an appropriate lithographic mask set, are provided. / Föreliggande examensarbete rapporterar designen och tillverkningsprocessen för en monolitisk InPbaserad 1550-nm så kallad Photonic-Crystal Surface-Emitting Laser (PCSEL). Komponenten bestå r av en aktiv kvantbrunnsstruktur i InGaAsP och ett fotoniskt-kristall (PhC)-lager i InP, bägge odlade med hjälp av metalorganisk gasfasepitaxi (MOCVD). En teoretisk studie baserad på Fourier-modalmetoden med användning av Stanford Stratified Structure Solver (S4) och finit elementanalys-metoden med med hjälp av av COMSOL Multiphysics utfördes för att optimera emissionen vid 1550 nm genom en tvådimensionell bandkantsresonanseffekt vid Γ punkten.Rapporten går igenom komponentdesign och modellering, materialtestning (värmebehandling och MOCVDåterväxt), processoptimering och tillverkning av lysdioder (LED) baserade på samma struktur som PCSELkomponenterna (men utan PhC-strukturering). De tillverkade lysdioderna uppvisar en låg serieresistans på 8.19 Ω och en framspänning på 0.84 V. Den genomsnittliga differentiella utgångseffekten är 41 mW/A med en luminescenstopp vid 1511 nm. Den slutliga tillverkningen av färdiga PCSEL-enheter ligger utanför ramen för detta examensarbete och motsvarar istället ett pågående projekt som förväntas bli slutfört inom det kommande året. Däremot ges detaljerade riktlinjer och tillverkningsinstruktioner, för vilket ett fotolitografiskt mask-set även tagits fram.

The pursuit of high quality, large area graphene has been a major research focus of contemporary materials science research, in the wake of the discovery of the multitude of exceptional properties exhibited by the material. The DPhil project was undertaken with the objective of developing an understanding of the growth of large graphene sheets by chemical vapour deposition (CVD), and also in the subsequent characterisation of their material properties. By conducting atmospheric pressure CVD growth at high methane flow rates, it was found that few-layered graphene (FLG) could be deposited on a copper catalyst. It is demonstrated that the self-limiting property of a copper catalyst is not universal to all deposition conditions, and shown that FLG grows in a terrace-like configuration. In depth transmission electron microscopy (TEM) studies were carried out on FLG. By selective image reconstruction from the inverse power spectrum of the TEM images, it was possible to elucidate the inter-grain connectivity of few-layer graphenes. It was determined that there were two possible inter-grain configurations possible; specifically an overlap of graphene layers or a discrete atomic bonding edge. The perturbation of the few-layer structure when subject to an out of plane distortion was found to incur a shift in the conventional AB-Bernal stacking of FLG. By utilising the aberration corrected TEM (AC-TEM) at Oxford it was possible to resolve atomic detail in CVD synthesised monolayer films, including atomic bond rotations and vacancies. The use of a high current density at low accelerating voltage (80 kV) was demonstrated to allow for the controlled defect creation in graphene sheets. This permitted the creation of monovacancies and iron doped vacancy complexes suitable for further study. The behaviour of these two defect types under electron beam irradiation was subsequently studied.

Produire à grande échelle des nanotubes de carbone en maîtrisant les principaux paramètres de croissance et la morphologie de ces matériaux est un enjeu important en vue de leur exploitation industrielle dans de nombreux domaines tels que l’élaboration de composites ou le stockage de l’énergie. C’est dans ce contexte que s’inscrit ce travail, basé sur la technique de dépôt chimique à partir d’une phase vapeur (CVD) mise en oeuvre dans un procédé faisant appel à un lit fluidisé de particules catalytiques (FB-CCVD). Dans un premier temps, nous avons étudié le catalyseur mis au point par la société Arkema, de sa préparation à son utilisation en catalyse pour la croissance de nanotubes de carbone multi-parois. Nous avons ainsi mis en évidence que la phase active était principalement localisée à la surface du support sous la forme d’une gangue discontinue d’hématite. Lors de la synthèse, nous avons constaté deux régimes cinétiques différents que nous avons confrontés aux évolutions physico-chimiques du matériau au cours du dépôt. Par la suite, nous avons préparé à partir du procédé Arkema différents catalyseurs bimétalliques afin d’augmenter le rendement de la synthèse de nanotubes de carbone et de diminuer leur diamètre. Un système à base de fer et de molybdène a montré une activité trois fois supérieure au catalyseur initial sous réserve de travailler à une température particulière. Enfin, dans une dernière partie, nous avons tenté de proposer une explication sur le rôle joué par le molybdène lors de la croissance des nanotubes de carbone. Nos observations nous ont mené à la préparation de catalyseurs coeur-écorce à base de fer et de molybdène présentant des activités supérieures à un système homogène. / The large scale production of carbon nanotubes associated with control of the main growth parameters and of the morphology is a challenging aim for future industrial exploitation of these nanostructured materials in numerous fields like composite production and energy storage. This work based on the fluidized bed catalytic chemical vapour deposition technique (FB-CCVD) lies in this industrial framework. At first, we have studied the catalyst produced by Arkema, from its synthesis to its use for carbon nanotubes growth. We have shown that the active phase is mainly located at the support surface in the form of a discontinuous film of hematite. During the synthesis, we have noticed two kinetic regimes that we analysed through caracterisation of the material at different times of the reaction. Then, we have prepared bimetallic catalysts using the Arkema process in order to improve the reaction yield and to decrease carbon nanotubes diameter. We have discovered thaht an iron and molybdenum based catalyst shows three times higher activity than the classic one, if we work at a specific temperature. At last, we have tried to explain the role played by molybdenum in the growth of carbon nanotubes. Our findings have lead us to develop core shell iron and molybdenum based catalysts presenting higher activity than the homogeneous sytem.

Thin film nanostructures may be defined as assemblies, arrays, or randomly distributed nanoparticles, nanowires, or nanotubes, which together form a layer of materials supported on a substrate surface. Because such nanostructures are supported on a substrate surface, their potential applications cover a wide area in optical, magnetic, electrochemical, electromagnetic, and optoelectronic devices. The focus of the present thesis is the development of methodologies to grow certain thin film nanostructures of some transition metal oxides (TMOs), including copper oxides and LixCoO2, through CVD, sol-gel, and electromagnetic radiation-mediated approaches. The work towards this objective can be divided into three parts: first, the design, synthesis, and systematic identification of novel metalorganic precursors of copper (monometallic) and Li and Co (bimetallic); second, the growth of nanostructured oxides thin films using these precursors; and third, the application of electromagnetic radiation to control or tailor the growth of as grown nanostructures. The underlying growth mechanisms substantiated by appropriate evidence have been put forward, wherever found relevant and intriguing. It may be added that the principal objective of the work reported here has been to explore the several ideas noted above and examine possibilities, rather than to study any specific one of them in significant detail. It is hoped earnestly that this has been accomplished to a reasonable extent. Chapter 1 reviews briefly the reports available in the literature on three specific methods of growing thin films nanostructures, namely chemical vapour deposition, sol-gel processing and light-induced approach. The objective of this chapter has been to provide the background of the work done in the thesis, and is substantiated with a number of illustrative examples. Some of the fundamental concepts involved, viz., plasmons and excitons, have been defined with illustration wherever found relevant in the context of the work. Chapter 2 describes the various techniques used for synthesis and characterisation of the metalorganic complexes as well as of the thin films. This chapters covers mostly experimental details, with brief descriptions of the working principles of the analytical procedures adopted, namely, infrared spectroscopy, mass spectroscopy, elemental analysis, and thermal analysis for characterisation of the metalorganic complexes. This is followed by a similarly brief account of techniques employed to characterize the thin films prepared in this work, viz., glancing incidence X-ray diffraction (GIXRD), field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), electrostatic force microscopy (EFM), transmission electron microscopy (TEM), glancing incidence infra-red spectroscopy (GIIR) and, UV-visible spectroscopy. The metalorganic chemical vapour deposition (MOCVD) systems built in house and used for growth of films are described in detail. The topics in the different sections of the chapter are accompanied by pertinent diagrams. Chapter 3 deals with the design, synthesis and characterisation of novel polynuclear complexes of copper and cobalt. Keeping in mind the various advantages such as low toxicity, ease of synthesis, non-pyrophoricity, and low temperature volatility, of environmentally benign complexes based on biologically compatible such as triethanolamine, diethanolamine, the objective has been to synthesize complexes containing triethanolamine and diethanolamine of transition metals such as cobalt and copper, and to investigate their applicability in MOCVD processes as a novel class of precursors. With the notion of ‘better’ and efficient design of precursors, an attempt has been made, through a semi-empirical modeling, to understand the correlation between volatility and various intrinsic molecular parameters such as lattice energy, vibrational-rotational energy, and internal symmetry. Chapter 4 discusses the growth of nanoporous Cu4O3-C composite films through the MOCVD process employing Cu4(deaH)(dea)(oAc)5.(CH3)2CO as the precursor. The various characteristic aspects of as-grown films, such as their crystallinity, morphology, and composition have been covered elaborately in various sections of this chapter. The chapter describes the efficient guiding and confining of light exploiting the photonic band gap of these nanoporous films, which indicates the potential usefulness of these and similar films as optical waveguides. A model described in the literature on absorbing photonic crystals, wherein a periodically modulated absorption entails an inevitable spatial modulation of dispersion, i.e., of the index contrast to open a photonic band gap, has been used to calculate the indices of refraction of one of these nanoporous films. The chapter also reports briefly the preliminary electrochemical investigations carried out on a typical film, examining the notion of its application as the anode in a Li-ion rechargeable battery. Chapter 5 describes the synthesis of nanocrystalline LixCoO2 films by the sol-gel method. Reports available in literature indicate that the various phases of LixCoO2 are extremely sensitive to processing temperature, making it difficult to control dimensionality of a given phase using temperature as one of process parameters. We have investigated the possibility of using incoherent light to tailor the particle size/shape of this material. The as-grown and irradiated films were characterised by X-ray diffraction, and by microscopic and spectroscopic techniques.Optical spectroscopy was carried out in order to gain insight into the physico-chemical mechanism involved in such structural and morphological transformation. Chapter 6 deals with the synthesis of self-assembled nanostructures from the pre-synthesized nanocrystals building blocks, through optical means of exciton formation and dissociation. It has been demonstrated that, upon prolonged exposure to (incoherent) ultraviolet-visible radiation, LixCoO2 nanocrystals self-assemble into acicular architectures, through intermediate excitation of excitons. Furthermore, it has been shown that such self-assembly occurs in nanocrystals, which are initially anchored to the substrate surface such as that of fused quartz. This new type of process for the self-assembly of nanocrystals, which is driven by light has been investigated by available microscopic and spectroscopic techniques. Chapter 7 describes the stabilisation of chemically reactive metallic lithium in a carbonaceous nanostructure, viz., a carbon nanotube, achieved through the MOCVD process involving a lithium-alkyl moiety. This moiety is formed in situ during deposition through partial decomposition of a metalorganic precursor synthesized in house, which contains both lithium and cobalt. It is surmised that the stabilization of metallic Li in the nanostructure in situ occurs through the partial decomposition of the metalorganic precursor. Quantitative X-ray photoelectron spectroscopy carried out on such a film reveals that as much as 33.4% metallic lithium is trapped in carbon. Lastly, Chapter 8 briefly highlights the outlook for further investigations suggested by the work undertaken for this thesis. Novel precursors derived from biologically compatible ligands can open up possibility of growing new type of micro/nano-structures, and of unusual phases in the CVD grown films. Furthermore, it is proposed that the novel method of growth and alignment of nanocrystals through irradiation with incoherent light, employed for the specific material LixCoO2, may be employed for various other metallic and semiconducting materials.

Abstract The main objectives of this thesis are to synthesize macroscopic well-aligned multi-walled carbon nanotube films and, based on their electrical conductivity, porosity and structural uniformity, highlight potential applications for further development. In this thesis, catalytic chemical vapour deposition from ferrocene-xylene precursors is optimized to grow high quality films of long, aligned multi-walled carbon nanotubes on lithographically patterned templates in high (~800ºC) temperatures. The impacts of reaction time, temperature and precursor concentration on MWCNT film quality (film thickness, purity, density and nanotube diameter distribution) are studied. Because of the excellent control of growth selectivity and film thickness inherent to the method, several interesting applications, including solar cell and capacitor electrodes, contact brushes, coolers, particulate filters and catalyst membranes, have been developed for nanotube films in collaboration between Finnish and international research groups over the past few years. In this thesis, advanced capacitor electrodes with improved charge storage and efficient particulate filters are discussed in closer detail. As the high temperatures used for growing high quality carbon nanotubes often cause complications in cases where nanotubes need to be directly integrated with other materials, experiments were also conducted with the aim of making the growth temperature as low as possible. After testing several catalyst and precursor combinations, cobalt nanoparticles deposited on silica surfaces were found to form carbon nanotubes from vaporized cyclopentene oxide precursor already at 470°C. The results show that catalytic chemical vapour deposition is a feasible and versatile method that can be combined with photolithography to produce multi-walled carbon nanotube films with desired footprint area and thickness on various substrates. The demonstrated new applications and technical solutions are expected to contribute to further development leading to competitive practical devices based on carbon nanotubes. / Tiivistelmä Tämän väitöstyön päätavoitteina ovat makroskooppisten, yhdensuuntaisista moniseinämäisistä hiilinanoputkista koostuvien kalvojen valmistaminen ja sovellutusten esittäminen perustuen kalvojen sähkönjohtavuuteen, huokoisuuten ja rakenteelliseen yhdenmukaisuuteen. Katalyyttis-kemiallinen höyryfaasikasvatusmenetelmä on optimoitu korkealaatuisten, yhdensuuntaisista, pitkistä moniseinämäisistä hiilinanoputkista koostuvien kalvojen tuottamiseen korkeissa lämpötiloissa (~800ºC) fotolitografialla kuvioiduille kasvualustoille käyttäen ferroseeni/ksyleeni-lähtöainetta. Reaktioajan, lämpötilan ja lähtöainepitoisuuden vaikutusta nanoputkikalvon laatuun on tutkittu tarkastelemalla kalvon paksuutta, puhtautta, tiheyttä ja nanoputkien läpimittajakaumaa. Erinomaisen kasvuselektiivisyyden ja kalvon paksuuden kontrolloimisen ansiosta nanoputkikalvoja voidaan räätälöidä useisiin mielenkiintoisiin sovellutuksiin (esim. aurinkokennot ja kondensaattorin elektrodit, hiiliharjat, jäähdyttimet, partikkelisuodattimet ja katalyyttikalvot), joita olemme kehittäneet viime vuosina yhdessä suomalaisten ja kansainvälisten tutkimusryhmien kanssa. Tässä väitöstyössä on tarkasteltu lähemmin uudentyyppisiä kondensaattorielektrodeja, joilla on parantunut sähkövarauksen varastointikyky, sekä tehokkaita partikkelisuodattimia. Hiilinanoputkien kasvattaminen korkeissa lämpötiloissa aiheuttaa usein ongelmia integroitaessa nanoputkia toisiin materiaaleihin. Tästä johtuen tutkimuksessa pyrittiin saamaan nanoputkien kasvatuslämpötila mahdollisimman alhaiseksi testaamalla useita lähtöaine-katalyytti-kombinaatioita, joista koboltti-nanopartikkelit piidioksidin päällä ja syklopenteenioksidi lähtöaineena muodostivat hiilinanoputkia jo 470°C:ssa. Tulosten perusteella katalyyttis-kemiallinen höyryfaasikasvatusmenetelmä yhdistettynä fotolitografiaan on hyvin monipuolinen tapa tuottaa moniseinämäisiä hiilinanoputkia halutulla kuviolla ja kalvonpaksuudella erilaisille substraateille. Tässä väitöstyössä demonstroitujen uusien sovellutusten ja teknisten ratkaisujen odotetaan johtavan uusiin, hiilinanoputkiin perustuviin kilpailukykyisiin käytännön laitteisiin.

No description available.

The main goal of this work is to introduce with the basic technologies of manufacturing MEMS (Micro-electro-mechanical-systems). Further there is mentioned properties and manufacturing of CNT (Carbon nanotubes), used in manufacturing of capacitance pressure sensor.

The master’s thesis deals with the theory of thin film technology, especially creating these layers. The work includes the distribution of vacuum deposition techniques for physical (PVD) and chemical (CVD). The main aim is to create a theme in different ways of implementation by using magnetron sputtering device, and these motives evaluated in terms of the quality of sputtering.

Coordination complexes [M(O2CCH2OC2H4OMe)2] (M = Co, 4; M = Mn, 5) are accessible by the anion exchange reaction between the corresponding metal acetates [M(OAc)2(H2O)4] (M = Co, 1; M = Mn, 2) and the carboxylic acid HO2CCH2OC2H4OMe (3). IR spectroscopy confirms the chelating or μ-bridging binding mode of the carboxylato ligands to M(II). The molecular structure of 5 in the solid state confirms a distorted octahedral arrangement at Mn(II), setup by the two carboxylato ligands including their α-ether oxygen atoms, resulting in an overall two-dimensional coordination network. The thermal decomposition behavior of 4 and 5 was studied by TG-MS, revealing that decarboxylation occurs initially giving [M(CH2OC2H4OMe)2], which further decomposes by M–C, C–O and C–C bond cleavages. Complexes 4 and 5 were used as CCVD (combustion chemical vapour deposition) precursors for the deposition of Co3O4, crystalline Mn3O4 and amorphous Mn2O3 thin films on silicon and glass substrates. The deposition experiments were carried out using three different precursor solutions (0.4, 0.6 and 0.8 M) at 400 °C. Depending on the precursor concentration, particulated layers were obtained as evidenced by SEM. The layer thicknesses range from 32 to 170 nm. The rms roughness of the respective films was determined by AFM, displaying that the higher the precursor concentration, the rougher the Co3O4 surface is (17.4–43.8 nm), while the manganese oxide films are almost similar (6.2–9.8 nm).

D. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / In this study, few layer graphene (Gr) and heteroatom graphene (HGr) were synthesized by chemical vapour deposition (CVD) method. Acetylene gas was used as carbon source for the synthesis of graphene, while a mixture of nitrobenzene and dichloromethane (ratio 1:1) were used as both carbon and dopant sources for the synthesis of the heteroatom graphene (HGr). A mixture of argon and nitrogen gases were carefully combined and used as carrier gasses and purge for both the synthesis of graphene and the synthesis of heteroatom graphene. X-ray diffraction (XRD) characterized showed that the as synthesized materials were crystalline materials, Raman spectroscopy indicated that the synthesized materials consist of sp2 hybridized carbon atoms, while scanning electron microscopy (SEM) and atomic force microscopy (AFM) results showed that the synthesized materials possess regions of 2 to 7 nm of thickness. Transmission electron microscopy (TEM) characterization also showed that the synthesized heteroatom graphene possesses about 5 to 7 layers with about 2 nm thickness, and x-ray photoelectron spectroscopy (XPS) result showed the presence of nitrogen, oxygen and chlorine in the lattice of the synthesized heteroatom graphene while the synthesized material still retained about 80% sp2 hybridization. The synthesized materials were used in the fabrication of modified bioelectrodes for electrobiocatalytic biosensing of glucose and hydroquinone. The fabricated bioelectrodes were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The CV characterization showed a diffusion-controlled electrode processes in al modified electrodes, while the EIS characterization showed the presence of both diffusion controlled and kinetic controlled impedance at the electrode-electrolyte interface. The fabricated GC/PEDOT-PSS/HGr/Lac modified bioelectrode exhibited a kinetic controlled impedance of 3150 Ω, while the fabricated GC/PEDOT-PSS/Gr/Lac modified bioelectrode exhibited a kinetic controlled impedance of 4138 Ω. Chronoamperometric experiments showed that the fabricated bioelectrodes exhibited swift electrobiocatalytic activity towards glucose and hydroquinone sensing respectively for graphene and heteroatom graphene. The graphene modified bioelectrode exhibited a linear response of 0.2 to 9.8 mM glucose concentration and a sensitivity of 87.0 μA/mM/cm2, while the heteroatom modified bioelectrode also exhibited a swift response to step by step addition of hydroquinone with a limit of detection of 2.07 μM and dynamic range of 2.07μM to 2.97 mM, thus indicating the tremendous potential of the materials in a wide range of electrobiocatalytic and bioelectronics applications.