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Dedigamuwa, Gayan S. "Formation of nanocoatings by laser-assisted spray pyrolysis and laser ablation on 2d gold nanotemplates." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001205.
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Guest, Andrew John. "Precursors for doped boron carbide thin films." Thesis, University of Salford, 2010. http://usir.salford.ac.uk/26700/.
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This Thesis is concerned with the development of high yield synthetic strategies to phosphaboranes and phosphacarboranes. These compounds have attracted attention due to their potential as single-source precursors for the deposition of thin films of doped boron carbide via plasma enhanced chemical vapour deposition. It has shown that suitable doping of the boron carbide can lead to wide band gap semiconductors and incorporation of phosphorus into the cage structure of the solid-state material is one way of achieving this aim. Chapter one discusses the chemical vapour deposition of boron carbide and goes on to describe its uses as neutron detectors and semiconductors. Chapter two presents the existing methods used for the synthesis of aminophosphines and highlights the importance of two such species, PH(NBus2)2 and PCl2N(CJln)2 . The remaining chapters cover the experimental work used for the preparation of phosphaboranes and phosphacarboranes that contain the phosphorus atom as a vertex. Chapter three focuses on the reaction of bis(dialkylamino)phosphines with decaborane and describes the synthesis of the nido-[l-nido-?^\o\\\2\ anion in high yield. In Chapter four, the use of the nido-[l-PB}oH\2\ anion to prepare a range of cluster complexes via reaction with a variety of electrophiles is discussed. Chapter five focuses on the reaction of bis(dialkylamino)phosphines with nido-5,6- dicarbadecaborane(12) and describes the synthesis of novel compounds of the formulae 6,9-R2NHP-5,6-C2 Bs Hn, (R = Pr', Bu1 ). This is considered as an intermediate product which subsequently gives a mixture of the nit/<>-7,8,\ 1- PC2B8Hn, mWo-[7,8,9-PC;>BxHio]~ and /m/o-[7,8,l 1-PC:B8 H IO ] species whose ratio is dependant on the R group. Each chapter contains a brief introduction, discusses the results obtained including multinuclear NMR spectroscopy and crystal structure data and concludes with an experimental section.
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Wilhelmsson, Ola. "Synthesis and Characterization of Ternary Carbide Thin Films." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8265.
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Tengstrand, Olof. "Transition metal carbide nanocomposite and amorphous thin films." Doctoral thesis, Linköpings universitet, Tunnfilmsfysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-104929.
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This thesis explores thin films of binary and ternary transition metal carbides, in the Nb-C, Ti-Si-C, Nb-Si-C, Zr-Si-C, and Nb-Ge-C systems. The electrical and mechanical properties of these systems are affected by their structure and here both nanocomposite and amorphous thin films are thus investigated. By appropriate choice of transition metal and composition the films can be designed to be multifunctional with a combination of properties, such as low electric resistivity, low contact resistance and high mechanical strength. Electrical contacts are one example of application that has been of special interest in this thesis. Since some industrially important substrates used in electrical contacts soften at higher temperature, all films were deposited with dc magnetron sputtering at a low substrate temperature (200-350 °C). I show that the electrical resistivity and mechanical properties of composites consisting of nanocrystalline NbC grains (nc-NbC) in a matrix of amorphous C (a-C) depend strongly on the amount of amorphous C. The best combination of hardness (23 GPa) and electrical resistivity (260 μΩ*cm) are found in films with ~15 at.% a-C phase. This is a higher hardness and lower resistivity than measured for the more well studied Ti-C system if deposited under similar conditions. The better results can be explained by a thinner matrix of amorphous C phase in the case of NbC. The nc-NbC/a-C is therefore interesting as a material in electrical contacts. Si can be added to further control the structure and thereby the properties of binary Me-C systems. There are however, different opinions in the literature of whether Si is incorporated on the Ti or C site in the cubic NaCl (B1) structure of TiC. In order to understand how Si is incorporated in a Me-Si-C material I use a model system of epitaxial TiCx (x ~0.7). In this model system a few atomic percent of Si can be incorporated in the cubic TiC structure. The experimental results together with theoretical stability calculations suggest that the Si is positioned at the C sites forming Ti(Si,C)x. The calculation further shows a strong tendency for Si segregation, which is seen at higher Si contents in the experiments, where Si starts segregate out from the TiCx to the grain boundaries causing a loss of epitaxy. If Si is added to an Nb-C nanocomposite, it hinders the grain growth and thus a reduced size of the NbC grains is observed. The Si segregates to the amorphous matrix forming a-SiC. At the same time the resistivity increases and the hardness is reduced. With even higher amounts of Si (>25 at.%) into the Nb-Si-C material, grain growth is no longer possible and the material becomes amorphous. In order to separate between effects from the addition of Si and the choice of transition metal I compare the Nb-Si-C system to already published results for the Zr-Si-C system. I find that the hardness of the material depends on the amount of strong Si-C bonds rather than the type of transition metal. The reduced elastic modulus is, however, dependent on the choice of transition metal. I therefore suggest that it is possible to make Me-Si-C films with high wear resistance by an appropriate choice of transition metal and composition. Electron microscopy was of importance for determining amorphous structures of Nb-Si-C and Zr-Si-C at high Si contents. However, the investigations were obstructed by electron beam induced crystallization. Further investigations show that the energy transferred from the beam electrons to C and Si atoms in the material is enough to cause atomic displacements. The displacements cause volume fluctuations and thereby enhance the mobility of all the atoms in the material. The result is formation of MeC grains, which are stable to further irradiation. Finally, I have studied substitution of Ge for Si in a ternary system looking at Nb-Ge-C thin films. I show that the films consist of nc-NbC/a-C/a-Ge and that Ge in a similar way to Si decreases the size of the crystalline NbC grains. However, a transition to a completely amorphous material is not seen even at high Ge contents (~30 at.%). Another dissimilarity is that while Si bonds to C and forms a matrix of a-SiC, Ge tends to bond to Ge.
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Deva, Reddy Jayadeep. "Mechanical properties of Silicon Carbide (SiC) thin films." [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002615.
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Scabarozi, Theodore H. Jr Barsoum M. W. "Combinatorial investigation of nanolaminate ternary carbide thin films /." Philadelphia, Pa. : Drexel University, 2009. http://hdl.handle.net/1860/3189.
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Deva, Reddy Jayadeep. "Mechanical Properties of Silicon Carbide (SiC) Thin Films." Scholar Commons, 2007. https://scholarcommons.usf.edu/etd/210.
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There is a technological need for hard thin films with high elastic modulus. Silicon Carbide (SiC) fulfills such requirements with a variety of applications in high temperature and MEMS devices. A detailed study of SiC thin films mechanical properties was performed by means of nanoindentation. The report is on the comparative studies of the mechanical properties of epitaxially grown cubic (3C) single crystalline and polycrystalline SiC thin films on Si substrates. The thickness of both the Single and polycrystalline SiC samples were around 1-2 µm. Under indentation loads below 500 µ-Newton both films exhibit Elastic contact without plastic deformation. Based on the nanoindentation results polycrystalline SiC thin films have an elastic modulus and hardness of 422 plus or minus 16 GPa and 32.69 plus or minus 3.218 GPa respectively, while single crystalline SiC films elastic modulus and hardness of 410 plus or minus 3.18 Gpa and 30 plus or minus 2.8 Gpa respectively. Fracture toughness experiments were also carried out using the nanoindentation technique and values were measured to be 1.48 plus or minus 0.6 GPa for polycrystalline SiC and 1.58 plus or minus 0.5 GPa for single crystal SiC, respectively. These results show that both polycrystalline SiC thin films and single crystal SiC more or less have similar properties. Hence both single crystal and polycrystalline SiC thin films have the capability of becoming strong contenders for MEMS applications, as well as hard and protective coatings for cutting tools and coatings for MEMS devices.
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Tan, Keng Ean. "Quantum mechanical modelling of refractory transition metal carbide films." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294188.
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Folkenant, Matilda. "Synthesis and Characterization of Amorphous Carbide-based Thin Films." Doctoral thesis, Uppsala universitet, Oorganisk kemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-247282.
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In this thesis, research on synthesis, structure and characterization of amorphous carbide-based thin films is presented. Crystalline and nanocomposite carbide films can exhibit properties such as high electrical conductivity, high hardness and low friction and wear. These properties are in many cases structure-related, and thus, within this thesis a special focus is put on how the amorphous structure influences the material properties. Thin films within the Zr-Si-C and Cr-C-based systems have been synthesized by magnetron sputtering from elemental targets. For the Zr-Si-C system, completely amorphous films were obtained for silicon contents of 20 at.% or higher. Modeling of these films, as well as experimental results suggest that the films exhibit a network-type structure where the bond types influence the material properties. Higher hardness and resistivity were observed with high amounts of covalent Si-C bonds. Several studies were performed in the Cr-C-based systems. Cr-C films deposited in a wide composition range and with substrate temperatures of up to 500 °C were found to be amorphous nanocomposites, consisting of amorphous chromium carbide (a-CrCx) and amorphous carbon (a-C) phases. The carbon content in the carbidic phase was determined to about 30-35 at.% for most films. The properties of the Cr-C films were very dependent of the amount of a-C phase, and both hardness and electrical resistivity decreased with increasing a-C contents. However, electrochemical analysis showed that Cr-C films deposited at higher substrate temperature and with high carbon content exhibited very high oxidation resistance. In addition, nanocomposite films containing Ag nanoparticles within an amorphous Cr-C matrix were studied in an attempt to improve the tribological properties. No such improvements were observed but the films exhibited a better contact resistance than the corresponding binary Cr-C films. Furthermore, electrochemical analyses showed that Ag nanoparticles on the surface affected the formation of a stable passive film, which would make the Cr-C/Ag films less resilient to oxidation than the pure Cr-C films.
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Lai, Chung-Chuan. "Phase Formation of Nanolaminated Transition Metal Carbide Thin Films." Doctoral thesis, Linköpings universitet, Tunnfilmsfysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-137367.
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Research on inherently nanolaminated transition metal carbides is inspired by their unique properties combining metals and ceramics, such as higher damage tolerance, better machinability and lower brittleness compared to the binary counterparts, yet retaining the metallic conductivity. The interesting properties are related to their laminated structure, composed of transition-metalcarbide layers interleaved by non-transition-metal (carbide) layers. These materials in thin-film form are particularly interesting for potential applications such as protective coatings and electrical contacts. The goal of this work is to explore nanolaminated transition metal carbides from the aspects of phase formation and crystal growth during thin-film synthesis. This was realized by studying phases in select material systems synthesized from two major approaches, namely, fromdirect-deposition and post-deposition treatment. The first approach was used in studies on the Mo-Ga-C and Zr-Al-C systems. In the former system, intriguing properties have been predicted for the 3D phases and their 2D derivatives (socalled MXenes), while in the latter system, the phases are interesting for nuclear applications. In this work, the discovery of a new Mo-based nanolaminated ternary carbide, Mo2Ga2C, is evidenced from thin-film and bulk processes. Its structure was determined using theoretical and experimental techniques, showing that Mo2Ga2C has Ga double-layers in simple hexagonal stacking between adjacent Mo2C layers, and therefore is structurally very similar to Mo2GaC, except for the additional Ga layers. For the Zr-Al-C system, the optimization of phase composition and structure of Zr2Al3C4 in a thin-film deposition process was studied by evaluating the effect of deposition parameters. I concluded that the formation of Zr2Al3C4 is favored with a plasma flux overstoichiometric in Al, and with a minimum lattice-mismatch to the substrates. Consequently, epitaxial Zr2Al3C4 thin film of high quality were deposited on 4H-SiC(001) substrates at 800 °C. With the approach of post-deposition treatment, the studies were focused on a new method of thermally-induced selective substitution reaction of Au for the non-transition-metal layers in nanolaminated carbides. Here, the reaction mechanism has been explored in Al-containing (Ti2AlC and Ti3AlC2) and Ga-containing (Mo2GaC and Mo2Ga2C) phases. The Al and Ga in these phases were selectively replaced by Au while the carbide layers remained intact, resulting in the formation of new layered phases, Ti2Au2C, Ti3Au2C2, Mo2AuC, and Mo2(Au1-xGax)2C, respectively. The substitution reaction was explained by fast outward diffusion of the Al or Ga being attracted to the surface Au, in combination with back-filling of Au, which is chemically inert to the carbide layers,to the vacancies. The substitution reaction was further applied to Ga-containing nanolaminated carbides, (Cr0.5Mn0.5)2GaC and Mo2GaC, motivated by development of novel magnetic nanolaminates. The former experiment resulted in the formation of (Cr0.5Mn0.5)2AuC, where the retained (Cr0.5Mn0.5)2C layers allowed a comparative study on the magnetic properties under the exchange of Ga for Au. After Au substitution, reduction in the Curie temperature and the saturation magnetization were observed, showing a weakened magnetic exchange interaction of the magnetic (Cr0.5Mn0.5)2 Clayers across the Au. In the Mo2GaC case, an Fe-containing MAX phase, Mo2AC with 50 at.% of Fe on the A site, was synthesized through selective substitution of Au-Fe alloy for the Ga layers, showing the first direct evidence for Fe in the MAX-phase structure. The substitution of Fe did not take place on another Mo2GaC sample tested for Fe exchange only, indicating the essential role of Au in catalyzing the Fe-substitution reaction. The knowledge gained from this thesis work contributes to improved approaches for attaining thin films of nanolaminated transition metal carbides with desired phase composition and crystal quality. The reports on the new nanolaminated phases through exchange interactions are likely to expand the family of nanolaminated carbides and advance their properties, and trigger more studies on related (quasi-) 2D materials.
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Gan, Wee Yong Chemical Sciences & Engineering Faculty of Engineering UNSW. "Synthesis and characterization of titanium dioxide thin films." Publisher:University of New South Wales. Chemical Sciences & Engineering, 2009. http://handle.unsw.edu.au/1959.4/43310.
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In this thesis, titanium dioxide (TiO2)-based thin film photocatalysts of different morphologies were synthesized and studied for their photoelectrocatalytic and photocatalytic properties. The superhydrophilicity of selected TiO2 films were also assessed. The work started with the synthesis of nanocrystalline TiO2 thin films with minimal porosity. A photoelectrocatalytic study was performed to evaluate the films?? photocurrent response in the presence of various organic compounds. At low concentrations, the amount of photocurrent generated was found to be influenced by the molecular structure of the organic compounds. As the concentration increased, the photocurrent response became dependent on the level of interaction of the organic compounds and their partially degraded intermediates with the TiO2 surface. Highly dispersed platinum (Pt) were added onto TiO2 films by a photo-deposition method, and their photocatalytic and photoelectrocatalytic activities were assessed using a novel thin-layer photo(electrochemical)-catalytic system. The system allowed the photocurrent data that originated from the photoelectrocatalysis process to be collected in the reaction cell, and the amount of organic compound being oxidized to be quantified. The Pt deposits were found to enhance photocatalysis by increasing the photogenerated charge-carriers separation, but conversely they retarded the photoelectrocatalysis process. The next part of the work covered the development of mesoporous TiO2 films via the evaporative-induced self-assembly procedure. The structural characteristics of the films were altered by controlling the relative humidity and temperature during the coating and thermal treatment processes. The effect of key structural parameters, such as film porosity, surface area and crystallinity, on the photoelectrocatalytic activity was investigated. These parameters were found to affect the photoelectrocatalysis because the performance of a catalyst in the photoelectrocatalysis application relies strongly on attributes such as the photocatalyst particles?? interconnectivity and the contact to the conducting substrate. The last part of this thesis demonstrated the effort undertaken to improve the UV-induced superhydrophilic effect of a TiO2 film. A multilayer structure of TiO2 nanoparticles was assembled to create a novel TiO2 film that required no UV-activation to induce a uniform water sheeting across its surface. The novel TiO2 thin film exhibited stable superhydrophilic wetting and anti-fogging behaviors after repetitive cycles of heat and wetting treatment, and this performance was affected by the porosity and surface hydroxyl (-OH) contents.
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Kandasamy, Ispran S. "Metalorganic chemical vapour deposited titanium dioxide thin films." Thesis, Brunel University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235909.
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Desai, Amit Y. "Fabrication and characterization of titanium-doped hydroxyapatite thin films." Thesis, University of Cambridge, 2007. http://www.dspace.cam.ac.uk/handle/1810/194740.
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Hydroxyapatite [Ca10(PO4)6(OH)2, HA] is used in many biomedical applications including bone grafts and joint replacements. Due to its structural and chemical similarities to human bone mineral, HA promotes growth of bone tissue directly on its surface. Substitution of other elements has shown the potential to improve the bioactivity of HA. Magnetron co-sputtering is a physical vapour deposition technique which can be used to create thin coatings with controlled levels of a substituting element. Thin films of titanium-doped hydroxyapatite (HA-Ti) have been deposited onto silicon substrates at three different compositions. With direct current (dc) power to the Ti target of 5, 10, and 15W films with compositions of 0.7, 1.7 and 2.0 at.% titanium were achieved. As-deposited films, 1.2 μm thick, were amorphous but transformed into a crystalline film after heat-treatment at 700C. Raman spectra of the PO4 band suggests the titanium does not substitute for phosphorous. X-ray diffraction revealed the c lattice parameter increases with additional titanium content. XRD traces also showed titanium may be phase separating into TiO2, a result which is supported by analysis of the Oxygen 1s XPS spectrum. In-vitro observations show good adhesion and proliferation of human osteoblast (HOB) cells on the surface of HA-Ti coatings. Electron microscopy shows many processes (i.e. filopodia) extended from cells after day one in-vitro and a confluent, multi-layer of HOB cells after day three. These finding indicate that there may be potential for HA-Ti films as a novel implant coating to improve upon the bioactivity of existing coatings.
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LeClair, Patrick R. (Patrick Royce) 1976. "Titanium nitride thin films by the electron shower process." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50025.
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Valente, João Pedro Mire Dores Pulido. "Calcium copper titanium oxide thin films for microelectronic applications." Master's thesis, Universidade de Aveiro, 2010. http://hdl.handle.net/10773/7612.
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Mestrado em Ciência de MateriaisRecent research has shown that the perovskite-related body-centred cubic material CaCu3Ti4O12 (CCTO) exhibit extraordinarily giant dielectric constant at room temperature (ε ≈ 104-105). Besides, these high dielectric constants were found to be nearly constant in the temperature range between 100 and 500K [1, 2]; which makes it even more attractive from the technological point of view. These properties are very important for device implementation and make CCTO a promising candidate for microelectronic applications (like decoupling capacitors, random access memories), microwave devices (for applications in mobile phones), antennas (for example, planar micro-strip antenna on CCTO substrate for 3-GHz operation) [3]. In the microelectronics device field, homogeneous and smooth thin films with colossal dielectric constant and with low dielectric loss are desirable. In the literature, only five reports on undoped CCTO films on silicon based substrates prepared by sol-gel method can be found. The majority of these authors did not present the dielectric and microstructural properties of the produced CCTO films. In this work, thin films of CCTO were prepared by sol-gel method by spin coating a nontoxic chemical solution on typical microelectronic substrates, Si (wafer) / SiO2 (300 nm) / TiO2 (20 nm) / Pt (150 nm). Two different precursor solutions were studied and optimized for film production. These two solutions differ mainly on the titanium precursor, although some preparation parameters where changed as well. One of the main objectives of the thesis was to develop nontoxic precursors for CSD method and accordingly, solutions were prepared without methoxyethanol (highly toxic). This constitutes a great improvement considering the good properties obtained for the 300-400 nm thick CCTO films prepared in this work: dielectric permittivity, ε of 500 and dielectric loss, tan of 0.19, for films derived from titanium butoxide precursor solutions (BUT-CCTO) and ε ≈ 620 and dielectric loss 0.18 for those derived from titanium isopropoxide precursor solutions (ISO-CCTO), all values at 1 kHz. In literature, toxic precursor solution of CCTO leads to films with values for dielectric permittivity of 1000-2000 and dielectric loss between 0.5 – 0.04 [52]. Best reports on nontoxic solutions for spin coating method presented dielectric constant (≈ 150-250) and losses around 0.2-0.5 [45]. The physical properties of the films were characterised. The structural and microstructural characterization was conducted via X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). [CALCIUM COPPER TITANIUM OXIDE THIN FILMS FOR MICROELECTRONIC APPLICATIONS] 10 For the electrical characterization the dielectric constant and dielectric losses were measured at room temperature in the range 100 Hz-1 MHz. AFM microstructure and especially potential images, confirmed IBLC model for conduction, since grain and grain boundaries presented different potentials due to their different electrical behaviour. This result was obtained for every sample made with both solutions. Grain size has a considerable influence on the dielectric properties of the thin films. grain films present high dielectric constant and high dielectric loss. Small grain origins lower dielectric constant but also low dielectric loss. In this work and based on IBLC model, it was found that grain and high grain boundaries density will guarantee good permittivity according with [6, 9], although with grain size increase, grain boundaries density decrease. An intermediate stage for grain size must be achieved depending on the solution used. Considering the dielectric loss, it was found to respect mainly to grain boundaries. High density of grain boundaries promotes second phase segregation (TiO2) due to low temperature heat treatments and worst insulator behaviour [18,24]. For one side, high density will lower dielectric loss confirming [6,13], on the other side, second phase segregation will increase it, as reported in [18, 24]. A compromise between the capacity of the semiconductor grains to admit charges and the resistivity of the insulator grain boundaries must be achieved to obtain good quality CCTO thin films. The admission of charges by the grain is controlled by the grain size (heat treatment procedure) meanwhile the current density of the grain boundaries is controlled by second phase segregation (solution procedure) and grain boundaries density (heat treatment procedure). As a final output of this work a new non-toxic precursor solution was developed as an alternative way for preparing CCTO thin films of high dielectric constant for microelectronic applications.
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Johnson, Saccha Ellen. "Atmospheric pressure chemical vapour deposition of titanium nitride from titanium tetrachloride and ammonia." Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242208.
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Nedfors, Nils. "Synthesis and Characterization of Multifunctional Carbide- and Boride-based Thin Films." Doctoral thesis, Uppsala universitet, Oorganisk kemi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-219040.
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This thesis present research on synthesis, microstructure, and properties of carbide- and boride- based thin films. The films have been synthesized by dc magnetron sputtering, and their microstructures have been characterized mainly by X-ray photoelectron spectroscopy (XPS), X-ray diffraction, and transmission electron microscopy. One of the main objectives with this research has been to evaluate the thin films potential as materials for sliding electrical contact applications and this have influenced, which properties that have been evaluated. Co-sputtered Nb-C films have a microstructure comprising of nanocrystalline NbCx (nc-NbCx) grains embedded in a matrix of amorphous C (a-C). A thinner a-C matrix form in the Nb-C films compared to the well-studied Ti-C system. As a consequence, the Nb-C films have a higher hardness and conductivity than previously studied Ti-C sputtered under similar conditions. The promising electrical contact properties are attained for reactively sputtered Nb-C films under industrial conditions, at deposition rates two orders of magnitude higher. A reduction in crystallinity is seen when Si is added to the Nb-C films and amorphous films forms at Si content > 25 at.%. The alloying of Si was however not beneficial for the electrical contact properties. Substoichiometric CrB2-x (B/Cr = 1.5) and NbB2-x (B/Nb = 1.8) films are achieved when deposited from MeB2 targets. Boron segregates to grain boundaries forming a B-rich tissue phase. This result in superhardness for the NbB2-x films (42 ± 4 GPa) as well as a low friction attributed to the formation of a boric acid film. Carbon forms a solid solution in the MeB2 grains as well as segregating to grain boundaries forming an amorphous BCx (a-BCx) phase when alloyed to CrB2-x and NbB2-x films. The formation of the a-BCx phase drastically improves the electrical contact resistance of the NbB2-x films. However, the mechanical properties are degraded, which result in a high friction and wear rate. It was in TEM studies of the metastable amorphous structures for the Nb-Si-C films found that the electron beam induces crystallization. Hence, great care is required when studying these types of metastable structures.
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Raghavan, Srikanth. "Comparative studies of 6H-SiC surface preparation." Morgantown, W. Va. : [West Virginia University Libraries], 2008. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5766.
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Thesis (M.S.)--West Virginia University, 2008.Title from document title page. Document formatted into pages; contains xii, 56 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 51-53).
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Thomas, T. "Chemical vapour deposition of titanium and vanadium arsenide thin films." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1310479/.
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This thesis describes the chemical vapour deposition (CVD) of titanium and vanadium arsenide thin films. The compounds [TiCl4(AsPh3)], [TiCl4(AsPh3)2], [TiCl4(Ph2AsCH2AsPh2)], [TiCl4(tBuAsH2)n] have been synthesised from the reaction of TiCl4 with the corresponding arsine, and they have been investigated as potential single-source precursors to TiAs. Additionally, [TiCl3(NMe2)(μ-NMe2)2AsCl] has been synthesised from the reaction of TiCl4 and As(NMe2)3, and although was thought not to be a suitable single-source precursor to TiAs due to its lack of preformed Ti-As bonds, its use a potential single-source precursor to TiN has been investigated. All synthesised compounds have been characterised using NMR, mass spectrometry and elemental analysis, and decompositional profiles studied by thermogravimetric analysis (TGA). Aerosol assisted (AA) and low pressure (LP)CVD have been used to investigate the use of the compounds as single-source precursors, with deposited films analysed by X-ray powder diffraction, wavelength dispersive X-ray (WDX) analysis and scanning electron microscopy (SEM). Thin films of TiAs have been deposited via the dual-source atmospheric pressure (AP)CVD reactions of tBuAsH2 with both TiCl4 and [Ti(NMe2)4]. This arsenic precursor has also been investigated within the deposition of VAs films via dual-source routes with its reaction with VCl4 and VOCl3. All deposited films have been characterised using X-ray powder diffraction, WDX, X-ray photoelectron spectroscopy (XPS), Raman microscopy, and SEM, with properties such as adherence, hardness, water contact angles and reflectivity measured.
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Gulses, Alkan Ali. "Ellipsometric And Uv-vis Transmittance Analysis Of Amorphous Silicon Carbide Thin Films." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605589/index.pdf.
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The fundamentals of the ellipsometry are reviewed in order to point out the strengths and weaknesses of the ellipsometric measurements. The effects of the surface conditions (such as degree of cleanliness, contaminated thin layer, roughness etc&hellip) on the ellipsometric variables are experimentally studied
the optimum procedures have been determined. Hydrogenated amorphous silicon carbide (a-Si1-xCx:H) thin films are produced by plasma enhanced chemical vapor deposition (PECVD) technique with a circular reactor, in a way that RF power and carbon contents are taken as variables. These samples are analyzed using multiple angle of incidence ellipsometer and uv-vis spectrometer. These measurements have inhomogeneities in optical constants, such as thicknesses, refractive indices and optical energy gaps along the radial direction of the reactor electrode for different power and carbon contents.
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Künle, Matthias [Verfasser]. "Silicon carbide single and multilayer thin films for photovoltaic applications / Matthias Künle." München : Verlag Dr. Hut, 2011. http://d-nb.info/1017353514/34.
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Högström, Jonas. "Corrosion and Surface Studies of Stainless Steel and Chromium Carbide Thin-Films." Doctoral thesis, Uppsala universitet, Institutionen för kemi - Ångström, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-208410.
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Although the passive films that form on stainless steels have been extensively studied, the concentration depth profiles are not fully understood. Their thinness makes passive films hard to study, but angle-resolved X-ray photoelectron spectroscopy (ARXPS) is a non-destructive technique that can be used to obtain depth information. An iterative approach to deconvolute ARXPS measurements into depth profiles is discussed, and the chemistry of passive films on a molybdenum-containing 316L stainless steel is investigated. Bipolar electrochemistry, in which the sample is placed along an electric field created by two driving electrodes in an electrolyte, is investigated as a screening tool. It is shown that the method is useful to create corrosion gradients on 304 stainless steel, both under pitting and non-pitting conditions. Chromium carbide thin films were deposited by magnetron sputtering with a variety of deposition parameters on stainless steel, and subsequently analyzed. It is shown that these films present a promising material system for protective coatings to improve the corrosion resistance of stainless steels while also maintaining other useful properties, such as low interfacial contact resistance. Particular attention is given to the electrochemical evaluation of the films, whose high carbon concentrations necessitates different interpretations of the electrochemical results compared to for stainless steels.
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Khoele, Joshua Relebogile. "Deposition and structural properties of silicon carbide thin films for solar cell applications." University of the Western Cape, 2014. http://hdl.handle.net/11394/4345.
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>Magister Scientiae - MScThe growth of hydrogenated amorphous silicon carbide (a-SiC:H) thin films deposited by Hot- Wire Chemical Vapour Deposition (HWCVD) for solar cell applications has been studied. The films were characterized for structural properties using Fourier Transform Infrared Spectroscopy FTIR, Elastic Recoil Detection Analysis (ERDA), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Raman Spectroscopy (RS). A low temperature of the substrate heater maintained at 280 °C was used in this thesis due to the demand of low-cost solar cells based on cheap substrate that require deposition at such low temperatures. In this thesis, we showed that the structural properties of a-SiC:H films are dependent on the filament temperature and also on the CH4 gas flow rate. It was shown that in non-stoichiometric a-SiC:H, hydrogen content throughout the deposited films varies with depth. An attempt is done in this study to determine, for the first time the absorption strength of the C-Hn bonds in the 950 -1050 cm-1 band of the FTIR spectrum. Real-time ERDA was used to determine the hydrogen kinetics parameters in a single temperature ramp; a model based on the solution of the diffusion equation is used for this effect.
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Ahmed, Fatema. "Structural properties and optical modelling of SiC thin films." University of the Western Cape, 2020. http://hdl.handle.net/11394/7284.
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>Magister Scientiae - MScAmorphous silicon carbide (a-SiC) is a versatile material due to its interesting mechanical, chemical and optical properties that make it a candidate for application in solar cell technology. As a-SiC stoichiometry can be tuned over a large range, consequently is its bandgap. In this thesis, amorphous silicon carbide thin films for solar cells application have been deposited by means of the electron-beam physical vapour deposition (e-beam PVD) technique and have been isochronally annealed at varying temperatures. The structural and optical properties of the films have been investigated by Fourier transform Infrared and Raman spectroscopies, X-ray diffraction, Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy and UV-VIS-NIR spectroscopy. The effect of annealing is a gradual crystallization of the amorphous network of as-deposited silicon carbide films and consequently the microstructural and optical properties are altered. We showed that the microstructural changes of the as-deposited films depend on the annealing temperature. High temperature enhances the growth of Si and SiC nanocrystals in amorphous SiC matrix. Improved stoichiometry of SiC comes with high band gap of the material up to 2.53 eV which makes the films transparent to the visible radiation and thus they can be applied as window layer in solar cells.
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Taylor, Matthew Bruce, and matthew taylor@rmit edu au. "A Study of Aluminium Nitride and Titanium Vanadium Nitride Thin Films." RMIT University. Applied Science, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080529.151820.
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Thin film coatings are used to improve the properties of components and products in such diverse areas as tool coatings, wear resistant biological coatings, miniature integrated electronics, micro-mechanical systems and coatings for optical devices. This thesis focuses on understanding the development of intrinsic stress and microstructure in coatings of the technologically important materials of aluminium nitride (AlN) and titanium vanadium nitride (TiVN) deposited by filtered cathodic arc deposition. Thin films of AlN are fabricated under a variety of substrate bias regimes and at different deposition rates. Constant substrate bias was found to have a significant effect on the stress and microstructure of AlN thin films. At low bias voltages, films form with low stress and no preferred orientation. At a bias voltage of -200 V, the films exhibited the highest compressive stress and contained crystals preferentially oriented with their c axis in the plane of the film. At the highest bias of -350 V, the film forms with low stress yet continue to contain crystallites with their c axis constrained to lie in the plane of the film. These microstructure changes with bias are explained in terms of an energy minimisation model. The application of a pulsed high voltage bias to a substrate was found to have a strong effect on the reduction of intrinsic stress within AlN thin films. A model has been formulated that predicts the stress in terms of the applied voltage and pulsing rate, in terms of treated volumes known as thermal spikes. The greater the bias voltage and the higher the pulse rate, the greater the reduction in intrinsic stress. At high pulsing and bias rates, a strong preference for the c axis to align perpendicular to the substrate is seen. This observation is explained by dynamical effects of the incident ions on the growing film, encouraging channelling and preferential sputtering. For the first time, the effect of the rate of growth on AlN films deposited with high voltage pulsed bias was investigated and found to significantly change the stress and microstructure. The formation of films with highly tensile stress, highly compressive stress and nano-composites of AlN films containing Al clusters were seen. These observations are explained in terms of four distinct growth regions. At low rates, surface diffusion and shadowing causes highly porous structures with tensile stress; increased rates produced Al rich films of low stress; increasing the growth rate further led to a dense AlN film under compressive stress and the highest rates produce dense, low stress, AlN due to increased levels of thermal annealing. Finally this thesis analyses the feasibility of forming ternary alloys of high quality TiVN thin films using a dual cathode filtered cathodic arc. The synthesised films show exceptional hardness (greater than either titanium nitride or vanadium nitride), excellent mixing of the three elements and interesting optical properties. An optimum concentration of 23% V content was found to give the highest stress and hardness.
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Hyde, Robert H. "Hollow-electrode pulsed plasma deposition of titanium and carbon thin films." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001856.
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Ahuja, Rajiv. "The synthesis, structure and properties of titanium-aluminum multilayered thin films /." The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487849696966896.
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Hu, Xiao. "Ultra-thin oxide films." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:d7373376-84f1-459e-bffb-f16ce43f02b7.
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Oxide ultra-thin film surfaces have properties and structures that are significantly different from the terminations of the corresponding bulk crystals. For example, surface structures of epitaxial ultra-thin oxide films are highly influenced by the crystallinity and electronegativity of the metal substrates they grown on. Some enhanced properties of the novel reconstructions are related to catalysis, sensing and microelectronics, which has resulted in an increasing interest in this field. Ultra-thin TiOx films were grown on Au(111) substrates in this work. Two well-ordered structures within monolayer coverage - honeycomb (HC) and pinwheel - were generated and investigated. Special attention has been paid to the uniform (2 x 2) Ti2O3 HC phase including its regular structure and imperfections such as domain boundaries (DBs) and point defects. Linear DBs with long-range repeating units have been observed; density functional theory (DFT) modelling has been used to simulate their atomic structures and calculate their formation energies. Rotational DBs/defects show up less frequently, however a six-fold symmetrical 'snowflake' DB loop stands out. Two types of point defects have been discovered and assigned to Ti vacancies and oxygen vacancies/hydroxyl groups. Their diffusion manners and pairing habits have been discussed within an experimental context. The results of growing NbOx ultra-thin films on Au(111) are also presented in this thesis. An identical looking (2 x 2) HC structure to the Ti2O3 ultra-thin film has been formed; a stoichiometry of Nb2O3 is suggested. Another interesting reconstruction is a hollow triangle structure. Various sizes have been found, and sides of these equilateral triangles all show a double-line feature aligned along the { 1 ₁⁻ } directions of the Au(111) lattice. Chemical composition characterisations of NbOx thin films are still required as is DFT modelling. Experimental techniques used in this thesis include scanning tunnelling microscopy (STM), low energy electron diffraction (LEED), and X-ray photoelectron spectroscopy (XPS). Ultra-thin oxide films were created by physical vapour deposition (PVD) in ultra-high vacuum (UHV) systems.
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Gold, Jeffrey Stephen. "Characterization of a novel methyl radical source and related thin film growth studies." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1787.
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Thesis (Ph. D.)--West Virginia University, 2000.Title from document title page. Document formatted into pages; contains xi, 108 p. : ill. (some col.) + appendix; 37 p. : ill. Includes abstract. Includes bibliographical references (p. 103-108; p. A-37).
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Ribeiro, A. Tome. "A study of the i-transition in rf-sputtered titanium nitride films." Thesis, Cranfield University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386196.
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Short, Eugene L. "Growth of oxide thin films on 4H- silicon carbide in an afterglow reactor." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001839.
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Crocker, Janina. "Measurement of the Young's modulus of Hexoloy silicon carbide thin films using nanoindentation." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=18414.
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Thin films of metals and ceramics are commonly used as the structural materials for microelectromechanical systems (MEMS). These systems are used for a wide range of applications that include sensors, displays, and portable power generators. Accurate measurement of the mechanical properties of these thin films is essential for the robust design of high-performance and reliable MEMS. In this thesis, the method of nanoindentation is used to characterize the elastic properties of thin films of Hexoloy-SG silicon carbide. This material is of particular interest for MEMS operating in harsh, hightemperature environments. Nanoindentation was performed using a commercial Hysitron TriboIndenter® equipped with a diamond Berkovich nanoindenter tip. During each nanoindentation test, the indenter was forced into the specimen by a calibrated load, while the indentation depth was recorded continuously with nanometer resolution. The first part of this thesis describes a detailed protocol for nanoindentation testing using the TriboIndenter® and discusses the calibration of the instrument using a quartz standard. The identification of errors due to drift, vibrations, and surface inhomogeneities is described in detail. This protocol was then used to test a 2.1 µm thick film of Hexoloy-SG silicon carbide film deposited on a 500 µm thick single-crystal silicon substrate. The film was tested with loads varying from 1,000 µN to 13,000 µN, such that the maximum indentation was always less than 10% of the film thickness. The nanoindentation load-displacement curves from a total of 155 individual indents were analyzed using three different methods to extract the value of the Young's modulus of the Hexoloy film. The first method, developed by Oliver and Pharr, is widely used in nanoindentation analysis, but does not account explicitly for the effects of the underlying substrate. It is valid strictly for monolithic materials. Therefore, refinements of the Oliver-Pharr method by King aDes structures formées de couches minces métalliques et céramiques sont couramment utilisées dans la conception de microsystèmes électromécaniques (MEMS). Ces derniers se retrouvent dans plusieurs domaines, tels que les capteurs, les vidéoprojecteurs et les systèmes de génération d'énergie portable. Pour concevoir des MEMS fiables, les propriétés mécaniques de ces couches minces doivent êtres connues précisément. Le but de cette thèse est d'utiliser la méthode de nanoindentation pour déterminer les propriétés mécaniques des couches minces de carbure de silicium Hexoloy-SG. Ce matériel à été développé pour des microsystèmes opérant dans des conditions thermiques et chimiques extrêmes. La nanoindentation a été réalisée par le système TriboIndenter® de Hysitron équipé d'une pointe Berkovich en diamant, de forme pyramidale à base triangulaire. Chaque indentation comprend un cycle charge/décharge durant lequel la pointe indentatrice est enfoncée et retirée du matériel par une force calibrée, tandis que la profondeur de l'indentation est surveillée continuellement au nanomètre près. La première partie de cette thèse décrit une procédure détaillée pour la nanoindentation avec le système TriboIndenter®, incluant la calibration de l'instrument utilisant une norme en quartz monolithique. Également, l'identification d'erreurs expérimentales reliées au système de nanoindentation dues à la dérive, aux vibrations et à la rugosité de l'échantillon et leurs mesures correctrices sont présentées. Par après, cette méthodologie a été utilisée pour tester les propriétés mécaniques d'une couche mince de Hexoloy-SG mesurant 2.1 µm d'épaisseur, déposée sur un substrat de silicium monocristallin comptant 500 µm d'épaisseur. La force exercée par l'indentateur sur l'échantillon varie de 1,000 µN à 11,000 µN, pour que la profondeur de l'indentation demeure en deçà de 10% de l'épaisseur totale de la co
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Yakovlev, A. V., and A. V. Vinogradov. "Colloids for Inkjet Printing of Highly Photoactive Thin Films." Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/42615.
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Creating of photovoltaic cells with high conversion of solar light – promising trend in the field of solar energy. In this paper, we proposed the use of inkjet printing technology of photoactive films based on MOFentrapped and pure TiO2 thin films. For this application we develop a unique low temperature sol-gel synthesis using physically activated sol of crystalline phases based on the titanium dioxide produced in the process of co-crystallisation with MOF. It is shown that the developed technology and materials not only provide point positioning photovoltaic layers with high efficiency, but also to promote self-cleaning properties, exhibiting photocatalytic properties.
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Tengdelius, Lina. "Growth and Characterization of ZrB2 Thin Films." Licentiate thesis, Linköpings universitet, Tunnfilmsfysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-98308.
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In this thesis, growth of ZrB2 thin films by direct current magnetron sputtering is investigatedusing a high vacuum industrial scale deposition system and an ultra-high vacuum laboratory scalesystem. The films were grown from ZrB2 compound targets at temperatures ranging from ambient (without external heating) to 900 °C and with substrate biases from -20 to -120 V. Short deposition times of typically 100 or 300 s and high growth rates of 80-180 nm/min were emphasized to yield films with thicknesses of 300-400 nm. The films were characterized by thinfilm X-ray diffraction with the techniques θ/2θ and ω scans, pole figure measurements andreciprocal space mapping, scanning and transmission electron microscopy, elastic recoil detection analysis and four point probe measurements. The substrates applied were Si(100), Si(111),4H-SiC(0001) and GaN(0001) epilayers grown on 4H-SiC. The Si(111), 4H-SiC(0001) substrates and GaN(0001) epilayers were chosen given their small lattice mismatches to ZrB2 making them suitable for epitaxial growth.The films deposited in the industrial system were found to be close to stoichiometric with a low degree of contaminants, with O being the most abundant at a level of < 1 at.%. Furthermore, the structure of the films is temperature dependent as films deposited in this system without external heating are fiber textured with a 0001-orientation while the films deposited at 550 °C exhibitrandom orientation. In contrast, epitaxial growth was demonstrated in the laboratory scale system on etched 4H-SiC(0001) and Si(111) deposited at 900 °C following outgassing of the substrates at 300 °C and in-situ heat treatment at the applied growth temperature to remove the native oxides. However, films grown on GaN(0001) were found to be 0001 textured at the applied deposition conditions, which make further studies necessary to enable epitaxial growth on this substrate material. Four point probe measurements on the films deposited in the industrial system show typical resistivity values ranging from ˜95 to 200 μΩcm with a trend to lower values for the films deposited at higher temperatures and at higher substrate bias voltages.
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Worbs, Peter. "Wetting behavior of titanium carbide films for carbon-copper braze joints in high heat flux components." kostenfrei, 2009. http://mediatum2.ub.tum.de/node?id=823480.
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Schmidt, Diedrich A. "Titanium dioxide thin films : understanding nanoscale oxide heteroepitaxy for silicon-based applications /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/9756.
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Alfredsson, Ylvi. "Electronic and Structural Properties of Thin Films of Phthalocyanines and Titanium Dioxide." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4802.
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Jain, Rakhi. "Biological interactions of fibroblasts with smooth microtextured commercially-pure titanium thin films /." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486457871784368.
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Schulz, Meghan E. "Nitrogen- and carbon-doped titanium dioxide thin films for solar hydrogen generation." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 95 p, 2009. http://proquest.umi.com/pqdweb?did=1896914051&sid=4&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Shelberg, Daniel Thomas. "PHYSICAL AND CHEMICAL PROPERTIES OF AMBIENT TEMPERATURE SPUTTERED SILICON CARBIDE FILMS." Cleveland, Ohio : Case Western Reserve University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1269963941.
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Thesis (Master of Sciences (Engineering))--Case Western Reserve University, 2010Department of Chemical Engineering Title from PDF (viewed on 2010-05-25) Includes abstract Includes bibliographical references and appendices Available online via the OhioLINK ETD Center
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Goyal, Amita. "Titanium dioxide-germanium nanocomposites for photovoltaic applications." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file Mb., 104 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:1435250.
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Ziemer, Katherine S. "Studies of the initial stage of silicon carbide growth on silicon." Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=1815.
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Thesis (Ph. D.)--West Virginia University, 2001.Title from document title page. Document formatted into pages; contains xvi, 217, 2 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 198-207).
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Ge, Xiang. "Electrochemical deposition of fluoridated calcium phosphate on titanium substrates /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?MECH%202008%20GE.
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Palmquist, Jens-Petter. "Carbide and MAX-Phase Engineering by Thin Film Synthesis." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3972.
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Richards, Mark Rowse. "Process development for IrAl coated SiC-C functionally graded material for the oxidation protection of graphite /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/10574.
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Dusatko, Tomas A. "Silicon carbide RF-MEM resonators." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100250.
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A low-temperature (<300°C) method to fabricate electrostatically actuated microelectromechanical (MEM) clamped-clamped beam resonators has been developed. It utilizes an amorphous silicon carbide (SiC) structural layer and a thin polyimide spacer. The resonator beam is constructed by DC sputtering a tri-layer composite of low-stress SiC and aluminum over the thin polyimide sacrificial layer, and is then released using a microwave O 2 plasma etch. Deposition parameters have been optimized to yield low-stress films (<50MPa), in order to minimize the chance of stress-induced buckling or fracture in both the SiC and aluminum. Characterization of the deposited SiC was performed using several different techniques including scanning electron microscopy, EDX and XRD.Several different clamped-clamped beam resonator designs were successfully fabricated and tested using a custom built vacuum system, with measured frequencies ranging from 5MHz to 25MHz. A novel thermal tuning method is also demonstrated, using integrated heaters directly on the resonant structure to exploit the temperature dependence of the Young's modulus and thermally induced stresses.
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Ratclifife, Peter John. "Plasma assisted deposition of thin films using molecular titanium alkoxide and amido precursors." Thesis, Durham University, 1995. http://etheses.dur.ac.uk/5445/.
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Metal-containing polymer thin films are known to possess interesting electrical, magnetic, optical or barrier properties. Such coatings can be deposited by plasma assisted chemical vapour deposition (PACVD). This technique comprises the fragmentation and rearrangement of metallorganic precursors within a low pressure non-equilibrium electrical discharge. In this work, the deposition of titanium containing species embedded into a polymeric network from titanium tetraisopropoxide (TiTP), Ti[OCH(CH(_3))(_2)](_4), and tetrakis (dimethylamido) titanium (TMT), Ti[N(CH(_3))(_2)](_4), precursors has been investigated as a function of glow discharge power and substrate location. In addition these precursors have been mixed with hydrogen and ammonia gases during PACVD. These metal-containing plasma polymers layers have been characterized by X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and atomic force microscopy (AFM).It has been demonstrated that Ti02/polymer composite layers can be produced using the TiTP precursor with a wide range of stoichiometries. The mixing of hydrogen gas with TiTP create films which are stable towards oxidation and aging. TiTP/ammonia mixtures produced Ti(0,N)/polymer films which contained Ti-N bonds. Injection of TMT into a glow discharge has been found to result in a non-thermally assisted intramolecular alkyl (3-hydrogen activation mechanism to produce Ti(0,C,N)/polymer composite films. The film composition is found to be independent of glow discharge power beyond 5 W. Mixing with hydrogen gas lowers the carbon content due to recombination reactions competing with plasma polymerization. TMT/ammonia mixtures result in a gas phase transamination reaction prior to and during plasma activation causing a drop in the total carbon content due to replacement of the -N(CH(_3))(_2) ligand by –NH(_x).
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Edusi, C. "Aerosol assisted chemical vapour deposition of titanium dioxide and tungsten oxide thin films." Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1434745/.
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This thesis focuses on the Aerosol Assisted Chemical Vapour deposition (AACVD) of titanium dioxide (TiO2) thin films using titanum (IV) isopropoxide (TTIP) and also reports the deposition of tungsten oxide via AACVD using tungsten hexacarbonyl [W(CO)6] in different solvents including methanol and ethanol. Chapter 1 of this thesis gives an overview of TiO2, including its properties and functions and the motivation for this project. In chapter 2 brief descriptions are provided of the main characterisation techniques used throughout this thesis. The substrate and solvent effect on the phase of TiO2 obtained by AACVD is outlined in chapter 3 and 4. TiO2 was deposited via the AACVD of TTIP in different solvents including methanol, ethanol and other solvents. The films deposited showed some substrate dependent morphology and properties. In particular at 550°C the films on steel show needle and rod like particles. XRD and Raman spectra of the TiO2 films showed that on steel or titanium substrates only the rutile form could be obtained, whereas on glass either anatase, anatase-rutile mixtures or rutile could be obtained depending on substrate temperature. Using methanol as the carrier solvent produced exclusively the rutile films on steel and predominantly rutile on glass substrates while the use of the other solvents produced exclusively the anatase phase on the steel under the same conditions. TiO2 was also deposited by AACVD from a mixture of ethanol and methanol solvents. As little as 15% of methanol in ethanol produces rutile as the predominant phase. The photocatalytic properties and the hydrophilicity of the films deposited are also reported. X-ray absorption spectroscopy (XAS) was used to map across the surface of the TiO2 films deposited as described in chapter 5. The X-ray absorption near edge structure (XANES) was used to determine the phase of TiO2 present at each point on the substrate. The AACVD deposition tungsten oxide using tungsten hexacarbonyl (W(CO)6) in methanol and ethanol is reported in chapter 6. Preferred orientation was observed when using either ethanol or methanol as the carrier solvent. In chapter 7 insitu work was attempted to investigate the mechanism of the deposited titania and tungsten oxide films. A new reactor vessel was designed, constructed and tested to allow synchrotron radiation in and out using a kapton window. The XANES pattern recorded during in-situ deposition were not of high enough to resolve the mechanism. The in-situ work carried out has great potential in the growth study of thin film deposition and can in the future help control the phase and composition of deposited films to produce more desirable properties.
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Lin, Wen-Bin, and 林文彬. "Titanium carbide thin films grown by reactive r.f. magnetron sputtering." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/06076245950028682073.
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碩士國立交通大學
電子研究所
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The experiments were performed in a diode magnetron r.f. sputtering unit. The deposition rate, composition, diffraction spectra, depth profile, cross section and surface microstructure of the TiC thin films, obtained by sputtering in CH4 pressure range from 0.25 * 10-3 to 0.98 * 10-3 Torr, have been measured. The results of deposition rate and composition measurements show that the amount of reactive constituents incorporated into the growing films depends on whether a TiC compound has been formed on the surface of the target. At low CH4 partial pressure (<0.36 mT) the system operated under conditions such that pure Ti was sputtered. At CH4 partial pressure higher than 0.36mT species originating from the target determine the composition of the coatings. The result of depth profile measurement show that the depth of C penetration into the interfacial region is less than that of Ti , and the study of diffraction spectra of the flms show that the films are single TiC phase at PCH4 = 0.87 to 0.91 mT. The important process parameter was found to be the partial pressure ratio of reactive gases CH4 to the sputtering gases Ar.
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Kiran, Vankayala. "Physicochemical, Electrical and Electrochemical Studies on Titanium Carbide-Based Nanostructures." Thesis, 2013. http://etd.iisc.ac.in/handle/2005/3325.
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Materials for studies related to nanoscience and nanotechnology have gained tremendous attention owing to their unique physical, chemical and electronic properties. Among various anisotropic nanostructures, one dimensional (1D) materials have received immense interest in numerous fields ranging from catalysis to electronics. Imparting multi-functionality to nanostructures is one of the major areas of research in materials science. In this direction, use of nanosized materials in energy systems such as fuel cells has been the subject of focus to achieve improved performance. Tuning the morphology of nanostructures, alloying of catalysts, dispersing catalytic particles onto various supports (carbon nanotubes, carbon nanofibers, graphene, etc.) are some of the ways to address issues related to electrochemical energy systems. It is worth mentioning that highly stable and corrosion resistant electrodes are mandatory as electrochemical cells operate under aggressive environments. Additionally, carbon, which is often used as a support for catalysts, is prone to corrosion and is subsequently implicated in reduced performance due to poor adherence of catalyst particles and loss in electrochemically active area. Hence, there is a quest for the development of stable and durable electrocatalysts / supports for various studies including fuel cells.
The present thesis is structured in exploring the multi-functional aspects of titanium carbide (TiC), an early transition metal carbide. TiC, a fascinating material, possesses many favorable properties such as extreme hardness, high melting point, good thermal and electrical conductivity. Its metal-like conductivity and extreme corrosion resistance prompted us to use this material for various electrical and electrochemical studies.
The current study explores the versatility of TiC in bulk as well as nanostructured forms, in electrical and electrochemical studies towards sensing, electrocatalytic reactions and active supports. 1D TiC nanowires (TiC-NW) are prepared by simple solvothermal method without use of any template and are characterized using various physico-chemical techniques. The TiC-NW comprise of 1D nanostructures with several µm length and 40 ± 15 nm diameter (figure 1). Electrical properties of individual TiC-NW are probed by fabricating devices using focused ion beam deposition (FIB) technique. The results depict the metallic nature of TiC-NW (figure 2).
Figure 1. (a) SEM, (b) TEM and (c) HRTEM images of TiC-NW prepared by solvothermal method.
Figure 2. (a) SEM image and (b) I-V characteristics of TiC-NW - based device as a function of temperature. The contact pads are made of Pt. Subsequently, oxidized TiC nanowires are prepared by thermal annealing of TiC-NW, leading to carbon - doped TiO2 nanowires (C-TiO2-NW) (figure 3). Photodetectors are fabricated with isolated C-TiO2-NW and the device is found to respond to visible light (figure 3) radiation with very good responsivity (20.5 A/W) and external quantum efficiency (2.7 X 104). The characteristics are quite comparable with several reported visible light photodetectors based on chalcogenide semiconductors.
Figure 3. (a) HRTEM, (b) EDAX, (c) Scanning TEM-DF images of C-TiO2-NW along with (d) Ti (e) O and (f) C mapping. (g) Current – voltage curves of single C-TiO2-NW recorded in dark (black) and in presence of visible light radiation (red) of intensity 57.7 mW/cm2 at 25oC. Inset of (g) shows the SEM image of the device (top) and schematic illustration of fabricated photodetector (bottom).
The next chapter deals with the electrochemical performance of TiC demonstrated for studies involving oxygen reduction and borohydride oxidation reactions. Electrochemical oxygen reduction reaction (ORR) reveal that TiC-NW possess high activity for ORR and involves four electron process while it is a two electron reduction for bulk TiC particles (figure 4). The data has been substantiated by density functional theory (DFT) calculations that reveal different modes of adsorption of oxygen on bulk and nanowire morphologies. Stable performance is observed for several hundreds of cycles that confirm the robustness of TiC. The study also demonstrates excellent selectivity of TiC for ORR in presence of methanol and thus cross-over issue can be effectively addressed in direct methanol fuel cells.
In the chapter on borohydride oxidation, bare TiC electrode is explored as a catalyst for the oxidation of borohydride. One of the major issues in direct borohydride fuel cells (DBFC) is the hydrolysis of borohydride that happens on almost all electrode materials leading to low efficiency. The present study reveals that TiC is a very good catalyst for borohydride oxidation with little or no hydrolysis of borohydride [figure 5 (a)] under the experimental conditions studied. Further, shape dependant activity of TiC has been studied and fuel cell performance is followed [figure 5 (b)]. Polarization data suggests that the performance of TiC is quite stable under fuel cell experimental conditions.
Figure 4. (a) Linear sweep voltammograms for ORR recorded using (i) bulk TiC particles and (ii) TiC-NW in O2-saturated 0.5 M KOH at 1000 rpm. Scan rate used is 0.005 Vs-1. (b) Variation of number of electrons with DC bias. Black dots correspond to TiC bulk particles while red ones represent nanowires.
Figure 5. (a) Cyclic voltammograms of borohydride oxidation on TiC coated GC electrode in 1 M NaOH containing 0.1 M NaBH4. Scan rate used is 0.05 Vs-1. (b) Fuel cell polarization data at 70oC for DBFC assembled with (i) bulk TiC particles and (ii) TiC-NW as anode catalysts and 40 wt% Pt/C as cathode. Anolyte is 2.1 M NaBH4 in 2.5 M NaOH, and catholyte is 2.2 M H2O2 in 1.5 M H2SO4. Anode loading is 1.5 mg cm-2 and cathode loading is 2 mg cm-2.
The corrosion resistance nature of TiC lends itself amenable to be used as an active support for catalytic particles (Pt and Pd) for small molecules oxidation reactions. In the present study, electro-oxidation of methanol, ethanol and formic acid have been studied. As shown in figure 6 (a), the performance of Pd loaded TiC (Pd-TiC) is found to be higher than that of Pd loaded carbon (Pd-C) suggesting the active role of TiC. The catalytic activities of TiC-based supports are further improved by tuning their morphologies. Figure 6 (c) reveals that the activities are higher in case of Pd-TiC-NW than that of Pd-TiC.
Figure 6. (a) Cyclic voltammograms of Pd-TiC and Pd-C for ethanol oxidation, (b) T EM image of Pd-TiC-NW and (c) voltammograms of Pd-TiC-NW in N2-saturated 1 M ethanol in 1 M KOH medium, scan rate used is 0.05 Vs-1.
The next aspect explored, is based on the preparation of C-TiO2 and its use as a substrate for surface enhanced Raman spectroscopy (SERS). Carbon doped titanium dioxide is prepared by thermal annealing of TiC. It is observed that the amount of dopant (carbon content) is dependent on the experimental conditions used. SERS studies using 4¬mercaptobenzoic acid (4-MBA) as the analyte, indicates that C-TiO2 [figure 7 (a)] enhances Raman signals based on chemical interactions between the analyte and the substrate. Raman signal intensities can be tuned with the amount of carbon content in C¬TiO2. Enhancement factors are calculated to be (7.7 ± 1.2) x 103 (for 4-MBA) and (1.7 ± 1.2) x 103 (for 4-nitrothiophenol). The SERS substrates are found to be surface renewable using visible light, a simple strategy to re-use the substrate [figure 7 (b)]. The regeneration of SERS substrates is based on self cleaning action of TiO2 that produces highly reactive oxygen containing radicals known to degrade the molecules adsorbed on TiO2.
Thus, the versatility of TiC has been demonstrated with various studies. In addition to using TiC-based materials, nanoparticles of Rh, Ir and Rh-Ir alloy structures have also been used for borohydride oxidation reaction. This is explained in the last section. In Appendix-I, preliminary studies on the preparation of TiC-polyaniline (PANI) composites using liquid-liquid interfacial polymerization is explained. Raman spectroscopy results suggest that the presence of TiC-NW makes PANI to assume preferential orientation in the polaronic (conducting) form. Appendix-II discusses the role of TiC-NW as a fluorescence quencher for CdS semiconductor nanoparticles.