Dissertations / Theses on the topic 'Chemical vapor deposition'
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1
Haberer, Elaine D. (Elaine Denise) 1975. "Particle generation in a chemical vapor deposition/plasma-enhanced chemical vapor deposition interlayer dielectric tool." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/8992.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1998.Includes bibliographical references (p. 77-79).
The interlayer dielectric plays an important role in multilevel integration. Material choice, processing, and contamination greatly impact the performance of the layer. In this study, particle generation, deposition, and adhesion mechanisms are reviewed. In particular, four important sources of interlayer dielectric particle contamination were investigated: the cleanroom environment, improper wafer handling, the backside of the wafer, and microarcing during process.
by Elaine D. Haberer.
S.M.
2
Karaman, Mustafa. "Chemical Vapor Deposition Of Boron Carbide." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12608778/index.pdf.
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Boron carbide was produced on tungsten substrate in a dual impinging-jet CVD reactor from a gas mixture of BCl3, CH4, and H2. The experimental setup was designed to minimise the effect of mass transfer on reaction kinetics, which, together with the on-line analysis of the reactor effluent by FTIR,
allowed a detailed kinetic investigation possible.
The phase and morphology studies of the products were made by XPS, XRD,micro hardness and SEM methods. XPS analysis showed the existence of chemical states attributed to the boron carbide phase, together with the existence of oxy-boron carbide species. SEM pictures revealed the formation
of 5-fold icosahedral boron carbide crystals up to 30 micron sizes for the samples produced at 1300oC. Microhardness tests showed change of boron carbide hardness with the temperature of tungsten substrate. The hardness
values (Vickers Hardness) observed were between 3850 kg/mm2 and 4750 kg/mm2 corresponding to substrate temperatures of 1100 and 1300 C, respectively.
The FTIR analysis of the reaction products proved the formation of reaction intermediate BHCl2, which is proposed to occur mainly in the gaseous boundary layer next to the substrate surface. The experimental parameters are
the temperature of the substrate, and the molar fractions of methane and borontrichloride at the reactor inlet. The effects of those parameters on the reaction rates, conversions and selectivities were analysed and such analyses were used in mechanism determination studies. An Arrhenius type of a rate
expression was obtained for rate of formation of boron carbide with an energy of activation 56.1 kjoule/mol and the exponents of methane and boron trichloride in the reaction rate expression were 0.64 and 0.34, respectively, implying complexity of reaction. In all of the experiments conducted, the rate of formation of boron carbide was less than that of dichloroborane.
Among a large number of reaction mechanisms proposed only the ones considering the molecular adsorption of boron trichloride on the substrate surface and formation of dichloroborane in the gaseous phase gave reasonable
fits to the experimental data. Multiple non-linear regression analysis was carried out to predict the deposition rate of boron carbide as well as formation rate of dichloroborane simultaneously.
3
Pickering, Elliot. "Chemical vapor deposition of Ti₃SiC₂." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/19463.
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Barua, Himel Barua. "COMPUTATIONAL MODELING OF CHEMICAL VAPOR DEPOSITION." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1469721885.
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Sukkaew, Pitsiri. "A Quantum Chemical Exploration of SiC Chemical Vapor Deposition." Doctoral thesis, Linköpings universitet, Halvledarmaterial, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-133941.
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SiC is a wide bandgap semiconductor with many attractive properties. It hasattracted particular attentions in the areas of power and sensor devices as wellas biomedical and biosensor applications. This is owing to its properties suchas large bandgap, high breakdown electric field, high thermal conductivitiesand chemically robustness. Typically, SiC homoepitaxial layers are grownusing the chemical vapor deposition (CVD) technique. Experimental studiesof SiC CVD have been limited to post-process measuring of the layer ratherthan in situ measurements. In most cases, the observations are presented interms of input conditions rather than in terms of the unknown growth conditionnear the surface. This makes it difficult to really understand the underlyingmechanism of what causes the features observed experimentally. Withhelp of computational methods such as computational fluid dynamic (CFD)we can now explore various variables that are usually not possible to measure.CFD modeling of SiC CVD, however, requires inputs such as thermochemicalproperties and chemical reactions, which in many cases are not known. In thisthesis, we use quantum chemical calculations to provide the missing detailscomplementary to CFD modeling. We first determine the thermochemical properties of the halides and halohydridesof Si and C species, SiHnXm and CHnXm, for X being F, Cl and Brwhich were shown to be reliable compared to the available experimentaland/or theoretical data. In the study of gas-phase kinetics, we combine ab initiomethods and DFTs with conventional transition state theory to derive kineticparameters for gas phase reactions related to Si-H-X species. Lastly, westudy surface adsorptions related to SiC-CVD such as adsorptions of small CHand Si-H-X species, and in the case of C-H adsorption, the study was extendedto include subsequent surface reactions where stable surface productsmay be formed.
6
Martin, Tyler Philip. "Platinumisilica Thin Films by Chemical Vapor Deposition." Fogler Library, University of Maine, 2002. http://www.library.umaine.edu/theses/pdf/MartinTP2002.pdf.
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Danielsson, Örjan. "Simulations of silicon carbide chemical vapor deposition /." Linköping : Univ, 2002. http://www.bibl.liu.se/liupubl/disp/disp2002/tek773s.pdf.
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Park, Jae-hyoung. "Process planning for laser chemical vapor deposition." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/18367.
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Nemirovskaya, Maria A. 1972. "Multiscale modeling strategies for chemical vapor deposition." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8500.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2002.Includes bibliographical references.
In order to predict the quality of the fabricated devices as a function of growth conditions in chemical vapor deposition (CVD) reactors, a model should describe multiple time and length scales. These scales include the reactor scale ([approx]0.1-1 m), the feature scale ([approx.]0.1-100 [mu]m), and the atomistic morphology evolution scale ([approx.]10 nm). At present, good reactor and feature scale models are available. However, the linking between them has been done only for low pressure CVD. Also, the atomistic Kinetic Monte Carlo models have been developed only for deposition on unpatterned substrates or over V-grooves. In this work the linking between reactor and feature scale models for both low and high pressure CVD is achieved by matching concentrations and fluxes across the interface. For low-pressure systems, we improve the convergence of the previously developed linking schemes by applying a flux-split algorithm. We analyze the assumptions underlying the linking, and demonstrate that the size of the feature domain is constrained by these assumptions and not simply by the assumption of collisionless gas phase transport. At high-pressure, mass transport between features complicates solution of the entire feature field. To capture the diffusive inter-feature transport, we develop the overlapping computational domains method. The simulation results obtained with the multiscale method are in excellent agreement with experimental data for selective epitaxy of AlGaAs in the presence of HC1. A KMC model is developed for AlGaAs surface morphology evolution during selective epitaxy. The model takes into account zincblende structure of AlGaAs, and reproduces the c(4x4) reconstruction on (100) surfaces.
(cont.) In order to model selective epitaxy, the mask is represented as a hard wall boundary condition, and overgrowth on (111)A facets is included. With this model, we investigate the effects of the unknown parameters and the growth conditions on film morphology evolution. The observed trends are in agreement with the experimental data. Since KMC simulations are limited to small surfaces and short deposition times we propose algorithms for linking the KMC and mesoscale feature shape evolution models. Finally, the feasibility of linking the coupled KMC-mesoscale model and the reactor or reactor-feature scale models is assessed.
by Maria A. Nemirovskaya.
Ph.D.
10
Martin, Tyler Philip 1977. "Chemical vapor deposition of antimicrobial polymer coatings." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38968.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2007.Includes bibliographical references.
There is large and growing interest in making a wide variety of materials and surfaces antimicrobial. Initiated chemical vapor deposition (iCVD), a solventless low-temperature process, is used to form thin films of polymers on fragile substrates. To improve research efficiency, a new combinatorial iCVD system was fabricated and used to efficiently determine the deposition kinetics for two new polymeric thin films, poly(diethylaminoethylacrylate) (PDEAEA) and poly(dimethylaminomethylstyrene) (PDMAMS), both candidates for antimicrobial coatings. Fourier transform infrared (FTIR) spectroscopy shows that functional groups are retained in iCVD of PDMAMS and PDEAEA, whereas essentially all fine chemical structure of the material is destroyed in plasma-enhanced CVD. It was found that the combinatorial system in all cases provided agreement, within experimental certainty, with results of blanket iCVD depositions, thus validating the use of the combinatorial system for future iCVD studies. Finished nylon fabric was subsequently coated with PDMAMS by iCVD with no affect on the color or feel of the fabric. Coatings PDMAMS of up to 540 gg/cm2 were deposited on fabric.
(cont.) A coating of 40 gpg/cm2 of fabric was found to be very effective against gram-negative E. coli, with over a 99.9999%, or 6 log, reduction in viable bacteria in one hour. A coating of 120 gg/cm2 was most effective against the gram-positive B. subtilis. Further tests confirmed that the iCVD polymer did not leach off the fabric. Type-II photoinitiation was utilized to perform vapor phase deposition of covalently-bound polymer coatings of the polymer PDMAMS. The durability was improved so that 80 wt% of the fabric coating was retained after extended antimicrobial testing and three rounds of ultrasonication. The coating was effective, killing 99.9% of E. coli in one hour. The gCVD process was then further explored using the less-UV-sensitive monomer DEAEA for deposition onto spun cast PMMA thin films. Durable films up to 54 nm thick retained 94% of their thickness after 10 rounds of ultrasonication. Gel Permeation Chromatography (GPC) and Variable Angle Spectroscopic Ellipsometry (VASE) swelling cell measurements gave estimated ranges of 72-156 kDa for the molecular weight and 0.1-0.24 chains/nm2 for the graft density.
by Tyler P. Martin.
Ph.D.
11
Olsson, Ylva Kristina. "Chemical vapor deposition of functionalized isobenzofuran polymers." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38584.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007.Includes bibliographical references (leaves 47-48).
This thesis develops a platform for deposition of polymer thin films that can be further tailored by chemical surface modification. First, we explore chemical vapor deposition of functionalized isobenzofuran films using two different functional groups: pentafluorophenolate ester and alkyne. Both functional groups can be further modified using either ester substitution or click chemistry, respectively. The resulting thin films are characterized extensively using nuclear magnetic resonance (NMR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). We show that the functional groups remain on the surface post deposition for both films at cracking temperature not exceeding 6000C. However, gel permeation chromatography(GPC) measurements of the pentafluorophenolate ester films show only marginal polymerization. On the other hand, the alkyne films appear crosslinked and showed defect formation. Films deposited at ambient temperature show formation of a large number of micro defects. Increasing the deposition temperature, in addition to increasing the growth rate, also leads to formation of films with two distinct domains: one smooth domain with no micro defects and another filled with defects.
(cont.) Analogous to the deposition of unmodified isobenzofuran films, the films with alkyne moiety have a high refractive index and are transparent in the visible and near IR range. Second, we explore coating of poly(dimethyl siloxane) (PDMS) microfluidic devices with poly(glycidyl methacrylate) (PGMA) thin films using initiated hot filament chemical vapor deposition. We demonstrate a use of a new ultra violet (UV) initiated bonding method that allows PGMA coated PDMS devices to be sealed to PGMA coated glass, while maintaining the integrity of the majority of surface functional groups. This approach allowed us to further functionalize the channel walls with hexamethylene diamine (HMDA) and poly(ethylene glycol) (PEG)-bis(amine) to make a lasting hydrophilic surface. Bonding of devices proved to be stable up to 2 bar.
by Ylva Kristina Olsson.
S.M.
12
Danielsson, Örjan. "Simulations of Silicon Carbide Chemical Vapor Deposition." Doctoral thesis, Linköpings universitet, Halvledarmaterial, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-104594.
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Most of the modern electronics technology is based on the semiconducting material silicon. The increasing demands for smaller electronic devices with improved performance at lower costs drive the conventional silicon technology to its limits. To meet the requirements from the industry and to explore new application areas, other materials and fabrication methods must be used. For devices operating at high powers, high temperatures and high frequencies, the so-called wide bandgap semiconductors can be used with great success. Silicon carbide (SiC) and III-nitrides are wide bandgap materials that have gained increased interest in recent years. One important technique in manufacturing of electronic devices is chemical vapor deposition (CVD), by which thin layers can be deposited. These layers may have different electrical properties, depending on the choice of material and doping. Generally in CVD, a reactive gas mixture flows through a heated reactor chamber, where the substrates are placed. Complex chemical reactions take place in the gas and on the substrate surface, leading to many intermediate species and by-products, and eventually to the desired deposition. For the growth of device quality material it is important to be able to control the properties of the grown layers. These properties generally depend on the growth conditions in the reaction chamber, and on the chemistry of the deposition process. So far, empirical trial-and-error methods have been employed in the development of growth processes. Due to the lack of basic understanding of the governing physical processes, progress is costly and time consuming. Improving and optimizing the CVD process, as well as improving the fundamental understanding of the whole process is of great importance when good quality material should be produced. For this, computer simulations of the relevant physical and chemical phenomena can provide the necessary tools. This thesis focuses on computer simulations of the CVD process, in particular CVD of SiC. Simulations can be used not only as a tool for optimizing growth processes and reactor designs, they can also give information about physical phenomena that are difficult to measure, such as the gas-phase composition or the flow paths inside the reactor. Heating of the CVD susceptor is a central part of the process. For the growth of high quality SiC a relatively high temperature must be used. A convenient method for heating to high temperatures is by induction. A low resistive material, such as graphite, is placed inside a coil, which is given an alternating current. The graphite is then heated by the induced currents due to ohmic resistance. In this thesis the temperature distribution inside a CVD reactor, and how it is influenced by changes in coil frequency, power input to the coil and graphite thickness, is investigated. It is shown that by changing the placement and shape of the coil and by using insulation material correctly, a more uniform temperature distribution can be obtained. A model for the growth of SiC is used to predict growth rates at various process parameters. A number of possible factors influencing the growth rate are investigated using this model. The importance of including thermal diffusion and the effect of etching by hydrogen is shown, and the effect of parasitic growth investigated. Simulations show a mass transport limited growth, as seen from experiments. An improved susceptor design with an up-lifted substrate holder plate is investigated and compared to a conventional hot-wall reactor and to a cold-wall reactor. It is shown that stress induced by thermal gradients through the substrate is significantly reduced in the hot-wall reactor, and that stress due to backside growth can be diminished using the new design. Positive side effects are that slightly higher growth rates can be achieved, and that the growth temperature can be slightly lowered in the new susceptor. The doping incorporation behavior is thoroughly investigated experimentally for intentional doping with nitrogen and aluminum. The doping incorporation on both faces of SiC, as well as on two different polytypes is investigated. Equilibrium calculations are preformed, giving possible candidates for species responsible for the doping incorporation. To predict nitrogen doping concentrations, a simplified quantitative model is developed and applied to a large number of process parameters. It is seen that the same species as predicted by equilibrium calculations are produced, but the reactions producing these species are relatively slow, so that the highest concentrations are at the outlet of the reactor. It is thus concluded that N2 must be the major specie responsible for the nitrogen incorporation in SiC. For the growth of III-nitrides, ammonia is often used to give the nitrogen needed. It is well known that ammonia forms a solid adduct with the metalorganic gas, which is used as the source for the group III elements. It would thus be beneficial to use some other gas instead of ammonia. Since purity is of great importance, N2 gas would be the preferred choice. However, N2 is a very stable molecule and difficult to crack, even at high temperatures. It is shown that hydrogen can help in cracking nitrogen, and that growth of III-nitrides can be performed using N2 as the nitrogen-bearing gas, by only small changes to a conventional hot-wall CVD reactor.
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Kostogrud, I. A., and D. V. Smovzh. "Chemical Vapor Deposition of Graphene on Copper." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35637.
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There are several methods for obtaining graphene. They could be divided into three main groups: me-chanical exfoliation, wet chemical methods, chemical vapor deposition (CVD). In this work CVD method was used for synthesis of graphene. The aim of the work was to obtain samples of graphene and to deter-mine the influence of the synthesis parameters. Synthesis of graphene was carried out in thermal reactor under ambient pressure. Methane was used as a precursor gas. Copper foil was used as a substrate. Exper-iments were carried out at different temperatures (970-1010 °С), varying consists of gas mixtures (Ar/He+H2+CH4), different exposition times (5-30 min) and different rates of samples cooling. Synthesized films were analyzed by Raman-spectroscopy method. In our experiments were obtained samples of few-layered graphene. It showed that the parameters of cooling significantly affect the properties of films.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35637
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Sanwick, Alexis. "Heteroatom-Doped Chemical Vapor Deposition Carbon Ultramicroelectrodes." Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/honors/592.
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Metal nanoparticles have been a primary focus in areas of catalysis and electrocatalysis applications as a result of their large surface area-to-volume ratios. While there is an increased interest in understanding the properties and behaviors of metal nanoparticles, they can become expensive over time. Recent research has incorporated the idea of using heteroatom-doped materials as a cheaper catalytic alternative to metal nanoparticles. In this study nitrogen-doping and phosphorous-doping techniques were applied to chemical vapor-deposited carbon ultramicroelectrodes in order to study the electrocatalytic properties toward the oxygen reduction reaction and the enhanced affinity for the deposition of gold nanoparticles onto the electrodes.
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Si, Jie. "Metalorganic chemical vapor deposition of metal oxides." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-12302008-063204/.
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Chen, Yu-Chun Wilamowski Bogdan M. Tzeng Y. "Diamond chemical vapor deposition and practical applications." Auburn, Ala., 2009. http://hdl.handle.net/10415/1774.
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Ayhan, Umut Baris. "Production Of Carbon Nanotubes By Chemical Vapor Deposition." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605199/index.pdf.
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ABSTRACT
PRODUCTION OF CARBON NANOTUBES BY
CHEMICAL VAPOR DEPOSITION
Ayhan, Umut BariS
M.S., Department of Chemical Engineering
Supervisor: Prof. Dr. Güngö
r Gü
ndü
z Co-Supervisor: Assoc. Prof. Dr. Burhanettin Ç
iç
ek July 2004, 75 pages Carbon nanotubes, which is one of the most attractive research subject for scientists, was synthesized by two different methods: Chemical vapor deposition (CVD), a known method for nanotube growth, and electron beam (e-beam), a new method which was used for the first time for the catalytic growth of carbon nanotubes. In both of the methods, iron catalyst coated silica substrates were used for the carbon nanotube growth, that were prepared by the Sol-Gel technique using aqueous solution of Iron (III) nitrate and tetraethoxysilane. The catalytic substrates were then calcined at 450 °
C under vacuum and iron was reduced at 500°
C under a flow of nitrogen and hydrogen. In CVD method the decomposition of acetylene gas was achieved at 600 °
C and 750 °
C and the carbon was deposited on the iron catalysts for nanotube growth. However, in e-beam method the decomposition of acetylene was achieved by applying pulsed high voltage on the gas and the carbon deposition on the silica substrate were done. The samples from both of the methods were characterized using transmission electron microscopy (TEM) and Raman spectroscopy techniques. TEM images and Raman spectra of the samples show that carbon nanotube growth has been achieved in both of the method. In TEM characterization, all nanotubes were found to be multi-walled carbon nanotubes (MWNT) and no single-walled carbon nanotubes (SWNT) were pictured. However, the Raman spectra show that there are also SWNTs in some of the samples.
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Lee, Woo Young. "Chemical vapor deposition of dispersed phase ceramic composites." Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/11857.
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Amaya, John. "Numerical study of combustion chemical vapor deposition processes." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/12991.
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Book, Gregory W. "Aerosol size effects in combustion chemical vapor deposition." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/20501.
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Hunt, Andrew J. "Combustion chemical vapor deposition from liquid organic solutions." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/16836.
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Liu, Yuh-Shiuan. "Ultraviolet emitters grown by metalorganic chemical vapor deposition." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50415.
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This thesis presents the development of III-nitride materials for deep-ultraviolet (DUV) light emitting devices. The goal of this research is to develop a DUV laser diode (LD) operating at room temperature. Epitaxial structures for these devices are grown by metalorganic chemical vapor deposition (MOCVD) and several material analysis techniques were employed to characterize these structures such as atomic force microscopy, electroluminescence, Hall-effect measurement, photoluminescence, secondary ion mass spectrometry, transmission electron microscopy, transmission line measurement, and X-ray diffraction. Each of these will be discussed in detail. The active regions of III-nitride based UV emitters are composed of AlxGa1-xN alloys, the bandgap of which can be tuned from 3.4 eV to 6.2 eV, which allows us to attain the desired wavelength in the DUV by engineering the molar fraction of aluminum and gallium. In order to emit photons in the DUV wavelength range (> 4.1 eV), high aluminum molar fraction AlxGa1-xN alloys are required. Since aluminum has very low ad-atom mobility on the growth surface, a very low group V to group III precursor ratio (known as V/III ratio), high growth temperature, and low growth pressure is required to form a smooth surface and subsequently abrupt heterointerfaces. The first part of this work focuses on developing high-quality multi-quantum well structures using high aluminum molar fraction ([Al] > 60%) AlxGa1-xN alloys. Optically pumped DUV lasers were demonstrated with threshold power density as low as 250 kW/cm² for the emission wavelength as short as 248.3 nm. Transverse electric (TE) -like emission dominates when the lasers were operating above threshold power density, which suggests the diode design requires the active region to be fully strained to promote better confinement of the optical mode in transverse direction. The second phase of this project is to achieve an electrically driven injection diode laser. Owing to their large bandgap, low intrinsic carrier concentration, and relatively high dopant activation energy, the nature of these high aluminum molar fraction materials are highly insulating; therefore, efficiently transport carriers into active region is one of the main challenges. Highly conducting p-type material is especially difficult to achieve because the activation energy for magnesium, a typical dopant, is relatively large and some of the acceptors are compensated by the hydrogen during the growth. Furthermore, due to the lack of a large work function material to form a p-type ohmic contact, the p-contact layer design is limited to low aluminum molar fraction material or gallium nitride. Besides the fabrication challenges, these low aluminum molar fraction materials are not transparent to the laser wavelength causing relatively high internal loss (αi). In this work, an inverse tapered p-waveguide design is employed to transport holes to active region efficiently while the graded-index separate-confinement heterostructure (GRINSCH) is employed for the active region design. Together, a multi-quantum well (MQW) ultraviolet emitter was demonstrated.
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Cheek, Roger W. (Roger Warren). "Selectivity Failure in the Chemical Vapor Deposition of Tungsten." Thesis, University of North Texas, 1994. https://digital.library.unt.edu/ark:/67531/metadc277954/.
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Tungsten metal is used as an electrical conductor in many modern microelectronic devices. One of the primary motivations for its use is that it can be deposited in thin films by chemical vapor deposition (CVD). CVD is a process whereby a thin film is deposited on a solid substrate by the reaction of a gas-phase molecular precursor. In the case of tungsten chemical vapor deposition (W-CVD) this precursor is commonly tungsten hexafluoride (WF6) which reacts with an appropriate reductant to yield metallic tungsten. A useful characteristic of the W-CVD chemical reactions is that while they proceed rapidly on silicon or metal substrates, they are inhibited on insulating substrates, such as silicon dioxide (Si02). This selectivity may be exploited in the manufacture of microelectronic devices, resulting in the formation of horizontal contacts and vertical vias by a self-aligning process. However, reaction parameters must be rigorously controlled, and even then tungsten nuclei may form on neighboring oxide surfaces after a short incubation time. Such nuclei can easily cause a short circuit or other defect and thereby render the device inoperable. If this loss of selectivity could be controlled in the practical applications of W-CVD, thereby allowing the incorporation of this technique into production, the cost of manufacturing microchips could be lowered. This research was designed to investigate the loss of selectivity for W-CVD in an attempt to understand the processes which lead to its occurrence. The effects of passivating the oxide surface with methanol against the formation of tungsten nuclei were studied. It was found that the methanol dissociates at oxide surface defect sites and blocks such sites from becoming tungsten nucleation sites. The effect of reactant partial pressure ratio on selectivity was also studied. It was found that as the reactant partial pressures are varied there are significant changes in the product partial pressure ratios, which are associated with gas phase reactions which contribute to the loss of selectivity.
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Trujillo, Nathan J. (Nathan Jeffrey). "Environmentally focused patterning and processing of polymer thin films by initiated chemical vapor deposition (iCVD) and oxidative chemical vapor deposition (oCVD)." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/62139.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references.
The new millennium has brought fourth many technological innovations made possible by the advancement of high speed integrated circuits. The materials and energy requirements for a microchip is orders of magnitude higher than that of "traditional" goods, and current materials management requirements for EHS friendly low-k processing require a 10% annual increase in raw materials utilization. Initiated Chemical Vapor Deposition (iCVD) is a low-energy, one step, solvent-free process for producing polymeric thin films This thesis describes the deposition of a novel low-k iCVD precursor, 1,3,5,7-tetravinyltetramethylcylcotetrasiloxane (V4D4). The high degree of organic content in the as-deposited film affords the ability to tune the film's properties by annealing. The incorporation of atmospheric oxygen at high temperatures enhances the mechanical and electrical properties of the films. Films annealed at 410'C have a dielectric constant of 2.15, hardness and modulus of 0.78 GPa and 5.4 GPa, respectively. These values are comparatively better than previously reported results for CVD low-k films. Environmentally friendly low-k processing encompasses materials and energy management in the entire integration process, including lithography. Colloidal lithography was combined with iCVD and capillary force lithography to create spatially addressable grafted polymer pattern nanostructures, without the need for expensive lithography tools. Using this method, we pattern our novel low dielectric constant polymer down to 25 nm without the need for environmentally harmful solvents. Furthermore, these grafted patterns were produced for a broad material set of functional organic, fluorinated, and silicon containing polymers. A variation of this process created amine functionalized biocompatible conducting polymer nanostructure patterns for biosensor applications. These were fabricated using grafting reactions between oxidative chemical vapor deposition (oCVD) PEDOT conducting polymers and amine functionalized polystyrene (PS) colloidal templates. Carboxylate containing oCVD copolymer patterns were used to immobilized fluorescent dyes. Fluorescent colloidal particles were assembled within dyed PEDOT-co-TAA copolymer nanobowl templates to create bifunctional patterns for optical data storage applications. Finally, UV and e-beam lithography were used to pattern covalently tethered vinyl monolayers for resist-free patterning of iCVD and oCVD polymers, using environmentally innocuous solvents.
by Nathan J. Trujillo.
Ph.D.
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Nuesca, Guillermo M. "Surface and Interfacial Studies of Metal-Organic Chemical Vapor Deposition of Copper." Thesis, University of North Texas, 1997. https://digital.library.unt.edu/ark:/67531/metadc278058/.
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The nucleation and successful growth of copper (Cu) thin films on diffusion barrier/adhesion promoter substrates during metal-organic chemical vapor deposition (MOCVD) are strongly dependent on the initial Cu precursor-substrate chemistry and surface conditions such as organic contamination and oxidation. This research focuses on the interactions of bis(1,1,1,5,5,5-hexafluoroacetylacetonato)copper(II), [Cu(hfac)2], with polycrystalline tantalum (Ta) and polycrystalline as well as epitaxial titanium nitride (TiN) substrates during Cu MOCVD, under ultra-high vacuum (UHV) conditions and low substrate temperatures (T < 500 K). The results obtained from X-ray photoelectron
spectroscopy (XPS), Auger Electron Spectroscopy (AES) and Temperature Programmed Desorption (TPD) measurements indicate substantial differences in the chemical reaction pathways of metallic Cu formation from Cu(hfac)2 on TiN versus Ta surfaces.
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Mount, Mason B. "Chemical vapor deposition on a filament in a cylinder." Ohio : Ohio University, 1989. http://www.ohiolink.edu/etd/view.cgi?ohiou1182459287.
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Choo, Jae-Ouk. "Development of a spatially Controllable Chemical Vapor Deposition System." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/2345.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2005.Thesis research directed by: Chemical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Beaulieu, David Cartier. "Electron Beam Chemical Vapor Deposition of Platinum and Carbon." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6990.
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Electron Beam Chemical Vapor Deposition (EBCVD) is a process by which an electron beam is used to decompose adsorbed reagent molecules to produce a deposit. The primary electrons from the beam, and especially the secondary electrons emitted from the substrate, dissociate the adsorbed molecules. Important factors for the deposition process include the beam parameters and reagent gas composition. Simple structures are fabricated through utilization of the various scanning modes of an SEM. Fibers (pillar-like structures) can be deposited, and lines (wall-like structures) can be deposited easily.
This investigation focuses on the process parameters controlling deposition rate and geometry for platinum and carbon fibers and lines in a modified SEM. Platinum deposition was performed using a system with a small diameter needle that supplied a localized flow of gas from an organometallic platinum compound. Carbon deposition was performed in the Environmental mode, in which the microscope chamber is filled with a specified pressure of reagent gas.
Statistically designed experiments were performed for platinum fiber and line deposition. Analysis indicated that the beam current and deposition time were dominant factors in determining the deposition rate. The voltage also had a significant effect on fiber deposition. For platinum line deposition, the effects of the dwell time and line time were also studied. The line time had a significant effect on line height deposited per scan. Optimization analysis was performed, and results indicated that high voltage and high beam current led to higher aspect ratios. Medium voltage and low beam current were preferable for depositing minimal width lines (less than 200 nm). Low voltage and high beam current were preferable for maximum deposition rates. EDS and EELS performed for platinum deposits in a TEM indicated amorphous structure with no carbon detected. This differs significantly from previously reported results.
Statistically designed experiments were performed for carbon line deposition. The voltage, beam current, and dwell/line time were studied. Increasing line time led to a significant increase in line height/scan and appeared to be a dominant factor. Lower beam currents appeared to favor higher deposition rates. TEM analysis indicated that carbon deposits were mostly amorphous.
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Mao, Yu 1975. "Initiated chemical vapor deposition of functional polyacrylic thin films." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33608.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005.Includes bibliographical references.
Initiated chemical vapor deposition (iCVD) was explored as a novel method for synthesis of functional polyacrylic thin films. The process introduces a peroxide initiator, which can be decomposed at low temperatures (<200⁰C) and initialize addition reaction of monomer species. The use of low temperatures limits the decomposition chemistry to the bond scission of initiator, while retaining functional groups of monomers, which has been confirmed in the infrared spectroscopy, nuclear magnetic resonance, and x-ray photoelectron spectroscopy of iCVD poly(glycidyl methacrylate) (PGMA) thin films. Studies of PGMA iCVD deposition kinetics and molecular weights indicate a free radical polymerization mechanism and provide guide for vapor-phase synthesis of other vinyl monomers. The retained epoxy groups can crosslink under e-beam irradiation, resulting in e-beam patterning of iCVD PGMA thin films with 80 nm negative-tone features achieved. iCVD copolymerization was also investigated to further tune film composition and properties. A surface propagation mechanism was proposed based on the study of the monomer reactivity ratios and the copolymer molecular weights during iCVD copolymerization.
(cont.) The synthesized acrylic copolymers have been investigated in applications as positive-tone e- beam resists, CO₂-developable resists, and low surface energy coatings with improved mechanical properties. The process of iCVD polymerization is extendable to vapor-phase polymerization of other vinyl monomers and creates new opportunities for the application of functional polymer thin films.
by Yu Mao.
Ph.D.
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Rodgers, Seth Thomas 1970. "Multiscale modeling of chemical vapor deposition and plasma etching." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/28219.
Full textAbstract:
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2000.Includes bibliographical references.
In this work, a framework and a set of modeling tools capable of describing systems with key processes occurring on widely separated length and time scales has been developed. The major focus of this work is linking atomistic and continuum descriptions of gas phase transport. This problem is of considerable practical interest, as most etching and CVD processes are run at low pressures ~ 1 torr or less. Under these conditions, the continuum diffusion models used to describe flow and transport in a typical reactor will fail below scales of a few hundred microns, and thus are not useful in describing transport in and around microscale topography. This is a serious limitation, as such topography is present in most microelectronic devices. Two methods for linking discrete particle (or feature scale) and continuum models of precursor transport are presented. The discrete and continuum models are coupled by boundary conditions at their mutual interface (just above any reactive surface with microscale detail) The first approach employs an effective reactivity function e,, which is computed through a hybrid probabilistic-deterministic MC method e. can be interpreted as a representation of the average fate of molecules entering the feature scale domain from the macroscopic model. An example of tungsten CVD over a substrate with surface topography typical of modern microelectronic devices is presented. A second, deterministic technique was also developed as an improvement on the Monte Carlo approach. The deterministic method uses the matrix of transmission probabilities, or shape kernel, to summarize all microscale events in a fashion consistent with a continuum macroscopic model. The deterministic linking algorithm is over 1,000 times faster than the previously presented MC method. The speed advantage enables simulation of detailed chemistry. Plasma etching presents a very similar multiscale problem and a strategy for linked plasma etching simulations is presented. Finally, a study of ionized physical vapor deposition of aluminum is presented as an example of atomistic-continuum linking. Molecular dynamics simulations are used to represent atomistic events. The Molecular Dynamics results are summarized in a manner that allows the combination of atomistic information with a continuum (level -set) model for evolution of the deposited metal film.
by Seth Thomas Rodgers.
Ph.D.
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Lee, Long Hua. "Air-gap sacrificial materials by initiated chemical vapor deposition." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/44292.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2007.Includes bibliographical references (leaves 81-83).
P(neopentyl methacrylate-co-ethylene glycol dimethacrylate) copolymer, abbreviated as P(npMAco-EGDA), was selected as the potential air-gap sacrificial material among possible combination of twenty monomers and four crosslinkers. P(npMA-co-EGDA) was deposited onto substrates using initiated chemical vapor deposition (iCVD) technique. Spectroscopic data showed the effective incorporation of both components in the copolymer and the integrity of repeating units were retained. The onset temperature of decomposition of P(npMA-co-EGDA) copolymer could be tuned between 290-3500C by varying the composition of the copolymer. The removal rate of polymer was calculated based on interferometry signal-time curve. The activation energy was determined by fitting the rate of decomposition with logistic model and found to be 162.7+8kJ/mole, which was similar to published data. Flash pyrolysis gas chromatography mass spectroscopy analysis showed that the products of thermal decomposition are monomers, rearranged small molecules and low oligomers. The modulus and the hardness were in the range of 3.9 to 5.5 GPa and 0.38 to 0.75 GPa, respectively, and were higher than those of linear poly(methyl methacrylate) (PMMA). Air-gap structures were constructed in the following scheme: P(npMA-co-EGDA) was deposited on the substrate by iCVD, followed by spincasting PMMA electron beam resist and scanning electron beam lithography to implement patterns on the resist. Reactive ion etching (RIE) was then applied to simultaneously etch the PMMA resist and P(npMA-co-EGDA) sacrificial material away in a controlled manner, leaving the patterned sacrificial material on the substrate.
(cont.) A layer of porous silica was deposited to cover the substrate and the patterned sacrificial material by plasma-enhanced chemical vapor deposition (PECVD) at 2500C and the sample was thermally annealed to allow the decomposed fragments to diffuse through the overlayer of silica. Using the scheme described above, it was possible to construct air-gap structures with feature size of 200nm and feature height of 1 00nm.
by Long Hua Lee.
S.M.
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Patnaik, Sanjay. "Modelling of transport processes in chemical vapor deposition reactors." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14192.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1989.Science hard copy bound in 2 v.
Includes bibliographical references (leaves 316-328).
by Sanjay Patnaik.
Ph.D.
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Anttila-Eriksson, Mikael. "Electrical Characterizationon Commercially Available Chemical Vapor Deposition (CVD) Graphene." Thesis, Uppsala universitet, Tillämpad materialvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-298357.
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Field-effect transistors (FET) based on graphene as channel has extraordinaryproperties in terms of charge mobility, charge carrier density etc. However, there aremany challenges to graphene based FET due to the fact graphene is a monolayer ofatoms in 2-dimentional space that is strongly influenced by the operating conditions.One issue is that the Dirac point, or K-point, shifts to higher gate voltage whengraphene is exposed to atmosphere. In this study graphene field-effect transistors(GFET) based on commercially available CVD graphene are electrically characterizedthrough field effect gated measurements. The Dirac point is initially unobservable andlocated at higher gate voltages (>+42 V), indicating high p-doping in graphene.Different treatments are tried to enhance the properties of GFET devices, such astransconductance, mobility and a decrease of the Dirac point to lower voltages, thatincludes current annealing, vacuum annealing, hot plate annealing, ionized water bathand UV-ozone cleaning. Vacuum annealing and annealing on a hot plate affect thegated response; they might have decreased the overall p-doping, but also introducedDirac points and non-linear features. These are thought to be explained by localp-doping of the graphene under the electrodes. Thus the Dirac point of CVDgraphene is still at higher gate voltages. Finally, the charge carrier mobility decreasedin all treatments except current – and hot plate annealing, and it is also observed that charge carrier mobilities after fabrication are lower than the manufacturer estimatesfor raw graphene on SiO2/Si substrate.
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Garman, Paul Douglas. "Chemical Vapor Deposition of Silicon Oxycarbide Catalyzed Graphene Networks." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1523898208600691.
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Freeman, Mathieu Jon. "Synthesizing diamond films from low pressure chemical vapor deposition /." Online version of thesis, 1990. http://hdl.handle.net/1850/11262.
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Chotsuwan, Chuleekorn. "Organometallic precursors for the chemical vapor deposition of LaB₆." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0005023.
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Cunha, Thiago Henrique Rodrigues da. "Chemical vapor deposition of graphene at very low pressures." Universidade Federal de Minas Gerais, 2014. http://hdl.handle.net/1843/BUBD-9WFHSS.
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The chemical vapor deposition (CVD) of hydrocarbons appears as the most suitable graphene production method for large area applications such as flexible displays and photovoltaics. However, the CVD mechanisms have not been fully understood and therefore a complete control over the morphology of the produced sheets has yet to be achieved. In this thesis we report a systematic investigation of graphene CVD at very low pressures performed on a cold wall reactor using copper substrates. A combination of scanning electron microscopy images and Raman spectroscopy measurements had demonstrated that the initial stages of graphene growth is strongly dependent of the growth temperature (T) and the nature of the carbon precursor. By using a high molecular weight liquid carbon precursor, growth of large graphene crystals (~up to 300 m) at very high rates (up to 3 m2.s-1) was achieved. For high temperature growth (T>900ºC), the shape and symmetry of the grains were found to depend on the underlying symmetry of the Cu crystal, whereas for lower temperatures (<900ºC), mostly rounded grains are observed. The temperature dependence of graphene nucleation density was determined, showing two thermally activated regimes, with activation energy values of (6±1) eV for 900 ºC < T < 960 ºC and (9±1) eV for T > 960 ºC. The comparison of such dependence with the temperature dependence of Cu surface self-diffusion suggests that graphene growth at high temperatures and low pressures is strongly influenced by copper surface rearrangement. A growth model was propose that incorporates Cu surface self-diffusion as an essential process to explain the orientation correlation between graphene and Cu crystals, and which can clarify the difference generally observed between graphene domain shapes in atmospheric-pressure and low-pressure chemical vapor deposition. In addition, we show that strain is induced over the graphene films during the coalescence of graphene individual domains.A deposição química de vapor (CVD) de hidrocarbonetos vem se tornando um paradigma para a produção de grafeno em larga escala. No entanto, os mecanismos de crescimento associados ao processo ainda não são totalmente compreendidos, de forma que ainda não é possível um controle sistemático da qualidade dos filmes sintetizados. Nesta tese, apresentamos uma investigação detalhada do crescimento de grafeno por CVD à baixa pressão em um reator de parede fria, utilizando substratos de cobre. Uma combinação de imagens de microscopia electrônica de varredura e de espectroscopia Raman demonstrou que a síntese é fortemente influenciada pela temperatura e pela natureza do precursor de carbono. Utilizando um precursor líquido de carbono e temperaturas próximas do ponto de fusão do cobre, sintetizamos monocristais de grafeno relativamente grandes (~ 300 m) a taxas muito elevadas (até 3 m2.s-1). Sob tais condições, as formas dos domínios de grafeno apresentaram uma clara dependência com a orientação cristalográfica do cobre. Além disso, verificamos através de um gráfico de Arrhenius da densidade de nucleação vs. temperatura que a síntese de grafeno exibe dois regimes distintos: para temperaturas variando de 900° C a 960° C, a energia de ativação foi estimada em (6±1) eV; enquanto que para temperaturas acima de 960° C, a energia de ativação foi calculada em (9±1) eV. A comparação de tal dependência com a dependência da autodifusão do cobre com a temperatura sugere que o crescimento de grafeno é fortemente influenciado pelo rearranjo da superfície de cobre. Propomos um modelo que incorpora a auto-difusão de superfície do cobre como um processo essencial para explicar a relação entre a orientação dos monocristais de grafeno cristais e do cobre. Este modelo também é capaz de explicar as diferenças observadas entre as formas dos domínios de grafeno crescidos à pressão atmosférica e os crescidos a baixas pressões. Por fim, mostramos que strain é induzido nos filmes durante a coalescência dos domínios individuais de grafeno.
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Zhang, Feng. "Chemical Vapor Deposition of Silanes and Patterning on Silicon." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2902.
Full textAbstract:
Self assembled monolayers (SAMs) are widely used for surface modification. Alkylsilane monolayers are one of the most widely deposited and studied SAMs. My work focuses on the preparation, patterning, and application of alkysilane monolayers. 3-aminopropyltriethoxysilane (APTES) is one of the most popular silanes used to make active surfaces for surface modification. To possibly improve the surface physical properties and increase options for processing this material, I prepared and studied a series of amino silane surfaces on silicon/silicon dioxide from APTES and two other related silanes by chemical vapor deposition (CVD). I also explored CVD of 3-mercaptopropyltrimethoxysilane on silicon and quartz. Several deposition conditions were investigated. Results show that properties of silane monolayers are quite consistent under different conditions. For monolayer patterning, I developed a new and extremely rapid technique, which we termed laser activation modification of semiconductor surfaces or LAMSS. This method consists of wetting a semiconductor surface with a reactive compound and then firing a highly focused nanosecond pulse of laser light through the transparent liquid onto the surface. The high peak power of the pulse at the surface activates the surface so that it reacts with the liquid with which it is in contact. I also developed a new application for monolayer patterning. I built a technologically viable platform for producing protein arrays on silicon that appears to meet all requirements for industrial application including automation, low cost, and high throughput. This method used microlens array (MA) patterning with a laser to pattern the surface, which was followed by protein deposition. Stencil lithography is a good patterning technique compatible with monolayer modification. Here, I added a new patterning method and accordingly present a simple, straightforward procedure for patterning silicon based on plasma oxidation through a stencil mask. We termed this method subsurface oxidation for micropatterning silicon (SOMS).
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Battiato, Sergio Orazio. "Metal organic chemical vapor deposition of functional fluoride phases." Doctoral thesis, Università di Catania, 2016. http://hdl.handle.net/10761/3756.
Full textAbstract:
Inorganic metal fluorides and oxide-fluorides have significant importance in the development of many new technologies, and are impacting various key points of modern life, that is, energy production and storage, microelectronics and photonics, catalysis, automotive, building, etc.
In the past few years, fluoride materials have attracted a great and increasing interest due to their multifunctional properties, such as ferroelectricity, induced ferro/antiferromagnetism, thermal stability, high transparency and low phonon energy.
Currently, the research on multiferroic materials is directed towards Bi-containing perovskite such as BiFeO3 or BiMnO3 and toward both hexagonal and orthorhombic rare-earth manganites such as HoMnO3 and TbMnO3.
Among the few known ferroelectric fluoride crystals, the barium fluoride BaMF4 (M=Mg, Mn, Co, Ni, Zn) phases have recently caught substantial attention in view of their interesting and multifunctional properties.
The BaMF4 multiferroics have been proposed as systems where is possible to incorporate both magnetism and ferroelectricity in the same phase.
The goal of this work is to explore a new class of multiferroic non-oxide based materials, focusing on the class of BaMF4 systems, to widen the range of candidates for magnetoelectric device applications. In addition, fluoride compounds have compelling advantages for many optical applications due to their unique combination of low phonon energy, high UV absorption edge energy, and relatively weak crystal field.
Compared with oxides, fluorides are considered to be efficient hosts for down-conversion (DC) and upconversion (UC) luminescence of rare earth (RE) ions due to their low phonon energies and optical transparency over a wide wavelength range.
The choice of host materials is of great importance in designing lanthanide-based luminescent UC materials for efficient practical applications.
Among the fluorides reported, rare earth (RE) doped NaYF4 and NaGdF4 are considered as the most efficient DC and UC host lattices, and have recently raised increasing attention. Many applications of RE-doped fluorides have been demonstrated, such as lasers, optical communications, display devices, and so on.
On the other hand, trivalent RE-doped MF2 (with M=Sr, Ca, Ba, Cd) compounds are also considered a suitable material characterized by low energy phonons (usually less than 300 cm-1) and large transfer coefficients between the RE ions. In this typology of halide hosts, multiphonon relaxation is thought to be strongly suppressed and therefore efficient UC luminescence can be obtained.
In this context, the present work discusses about some different rare-earth doped fluoride materials based on NaREF4 and MF2 host lattices, which possess physical properties of technological interest. In this study, Metal Organic Chemical Vapor Deposition (MOCVD) approaches have been used to fabricate the fluoride phases of interest in form of thin films. A systematic study of precursors suitable for the MOCVD growth of the fluoride films has been addressed. The synthesized films have been characterized from a structural, morphological and compositional point of view.
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Ellzey, Karen Elizabeth. "Feasibility study of the chemical vapor infiltration of rhenium." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17534.
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Endle, James Patrick. "MOCVD of multimetal and noble metal films /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Shapiro, Michael Jay. "Chemical vapor deposition of silver films for superconducting wire applications." Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/19168.
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Beckloff, Bruce Nick. "Chemical vapor deposition of titanium diboride and polycrystalline silicon for use in thin film solar cells." Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/19988.
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Rönnby, Karl. "Quantum Chemical Feasibility Study of Methylamines as Nitrogen Precursors in Chemical Vapor Deposition." Thesis, Linköpings universitet, Kemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-132812.
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The possibility of using methylamines instead of ammonia as a nitrogen precursor for the CVD of nitrides is studied using quantum chemical computations of reaction energies: reaction electronic energy (Δ𝑟𝐸𝑒𝑙𝑒𝑐) reaction enthalpy (Δ𝑟𝐻) and reaction free energy (Δ𝑟𝐺). The reaction energies were calculated for three types of reactions: Uni- and bimolecular decomposition to more reactive nitrogen species, adduct forming with trimethylgallium (TMG) and trimethylaluminum (TMA) followed by a release of methane or ethane and surface adsorption to gallium nitride for both the unreacted ammonia or methylamines or the decomposition products. The calculations for the reaction entropy and free energy were made at both STP and CVD conditions (300°C-1300°C and 50 mbar). The ab inito Gaussian 4 (G4) theory were used for the calculations of the decomposition and adduct reactions while the surface adsorptions were calculated using the Density Functional Theory method B3LYP. From the reactions energies it can be concluded that the decomposition was facilitated by the increasing number of methyl groups on the nitrogen. The adducts with mono- and dimethylamine were more favorable than ammonia and trimethylamine. 𝑁𝐻2 was found to be most readily to adsorb to 𝐺𝑎𝑁 while the undecomposed ammonia and methylamines was not willingly to adsorb.
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Alf, Mahriah E. (Mahriah Elizabeth). "Functional and responsive surfaces via initiated chemical vapor deposition (iCVD)." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/65754.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references.
Stimuli-responsive polymers provide a method to control system behavior through the use of an external stimulus, such as temperature, pH, or electric fields among others. Temperature-responsive polymers, especially those based on N-isopropylacryalmide (NIPAAm), are of particular research interest due the ease of implementation of temperature changes to systems as well as the large accessible range of hydrophilic / hydrophobic switching. Initiated chemical vapor deposition (iCVD) is shown to be a useful technique for surface modification with NIPAAm-based polymers due to its ability to provide complete functional retention and applicability to "real world" substrates, which many times have varying compositions and / or micro- or nano-structured surfaces. The novel copolymer thin film of iCVD poly(NIPAAm-co-di(ethylene glycol) divinyl ether) (p(NIPAAm-co-DEGDVE)) is shown to exhibit a sharp lower critical solution temperature (LCST) transition, better-than or equivalent to other surface modification techniques, while also being able to achieve a wider range of thicknesses from the nano- to micro-scale, which is especially useful for flow control, actuator or sensor applications. The bottom-up film growth of iCVD allows for compositional gradients throughout the thickness of a polymer film. A novel NIPAAm-based copolymer with a NIPAAm-rich surface layer is developed which exhibits both fast swelling and deswelling kinetics. Quartz crystal microbalance with dissipation monitoring (QCM-D) is used to study the transition behavior of these films. These data provide valuable information relating to the polymer conformational changes throughout the transition region and help elucidate thermodynamic and mesh characteristics of the films. Finally, an application is developed which utilizes both iCVD and a complementary technique, oxidative CVD (oCVD), to create self-heating membranes with responsive permeability characteristics.
by Mahriah E. Alf.
Ph.D.
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Liu, Kou-Liang, and 劉國良. "Electro-catalyzed Chemical Vapor Deposition." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/58370796945447288842.
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碩士國立臺灣科技大學
化學工程系
93
Abstract This study investigated a novel electro-catalyzed chemical vapor deposition (CVD) technique for the growth of copper thin films on TaNx/Si substrates using (hfac)Cu(COD) as the precursor. Without supplying direct current, copper films that deposited on TaNx/Si were loose and rough. As a result, this copper film can’t be used as a seed layer. Due to the fact that the disproportionation reaction occurred during CVD involves electron exchange through the substrate, we proposed a new idea of electro-catalyzed Cu-CVD technique by supplying direct current to the TaNx/Si substrates throughout the film growth. Surface morphology and film thickness were characterized by scanning electron microscopy (SEM). Chemical composition and film roughness were analyzed by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. Electrical resistivity of the films was measured with a four point probe. The results revealed that supplying direct current to TaNx/Si substrates during Cu-CVD were able to reduce the incubation time, significantly enhance nucleus density and reduce nucleus size. The proposed electro-catalyzed CVD was found to succeed in forming pure, smooth and continuous thin copper films.
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Kamel, John K. "Chemical vapor deposition/chemical vapor infiltration of pyrocarbon in porous carbon." 2007. http://etd.nd.edu/ETD-db/theses/available/etd-09222007-022308/.
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Thesis (Ph. D.)--University of Notre Dame, 2007.Thesis directed by Samuel Paolucci for the Department of Aerospace amd Mechanical Engineering. "September 2007." Includes bibliographical references (leaves 213-239).
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Shyu, Yih-Ming, and 徐逸明. "Low Temperature Growth of Carbon Nanotubes by Chemical Vapor Deposition and Plasma Assisted Chemical Vapor Deposition." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/43455215312083945152.
Full textAbstract:
博士國立成功大學
化學工程學系
90
The growth of carbon nanotubes at low temperature was studied by thermal chemical vapor deposition and plasma chemical vapor deposition methods. By thermal chemical vapor deposition method, carbon nanotubes could be synthesized from 400 to 700℃at 90Torr with catalysts using acetylene or carbon monoxide reactant. Well-aligned carbon nanotubes with defects and strain could be grown at 400℃. The strain of the nanotubes could be released with less defects when reaction temperature rose about 500℃. However, the well alignment disappeared due to the low growth density. Carbon soots, detected by Raman spectroscopy, were deposited on the substrate by thermal decomposition of acetylene in gas phase at a higher temperature. Compositions of Fe-Ni particle were also varied (2~55%Fe) to study its effect on the growth of carbon nanotubes at 400℃. The growth rate increased when the composition of Fe increased inside catalyst. The catalysts pretreated with dilute acetylene or carbon monoxide were suitable for carbon nanotube growth at a very low temperature. The turn on voltage for filed emission was 11V/mm. By plasma chemical vapor deposition method, carbon nanotubes could be grown from 400 to 700℃at 15Torr using CH4/N2/H2 as reactants. Well-aligned carbon nanotubes could be grown by free radicals produced from the plasma in a wide range of growth conditions. No carbon was deposited on the catalyst-covered substrate when it is exposed directly to the plasma. NH and CN radicals, detected by residual gas analyzer and optical emission spectroscopy, play an important role in growing carbon nanotubes. The substrate temperature, the most important parameter, affects the carbon nanotube growths, especially at a low temperature. Only carbon fibers were formed when the substrate temperature was below 460℃ due to the hydrogenation of carbon in the hydrogen plasma. The formation of C-H bonds, by hydrogen atom and the carbon precipitated from saturated catalyst, prohibits the formation of curly and seamless graphite planes. In both thermal and plasma chemical vapor deposition methods, bamboo type carbon nanotubes could be grown when active nitrogen atoms exist in the gas phase, possibly due to the modification of carbon nanotube structure by nitrogen reaction. Nitrogen atoms partially replace carbon atoms on the graphite network, inducing one carbon atom to be bonded to other species or destroying two six-member rings. The nitrogen addition increases the surface energy of carbon nanotubes, interacting more strongly with liquid catalysts when growing carbon nanotubes. The catalyst’s morphology thus varied periodically by minimizing its total energy. Bamboo type carbon nanotubes are then formed during this deformation processes. In the arc method, the high reaction temperature reduces the surface energy of the catalyst. Hence, catalysts can deform periodically balancing between the capillary force and the congregate force. Bamboo type carbon nanotubes were therefore formed. Only lithium carbide was formed when lithium nitrate acetone was used as catalyst due to small atomic size and low surface tension of lithium. In lower temperature, low than 350℃, curl graphite plane and quasi-hollow graphite structures were grown when methane and oxygen was used as reaction gases.
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LI, Mark Xiang. "Silicon Refining Through Chemical Vapor Deposition." Thesis, 2007. http://hdl.handle.net/1807/25713.
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Currently the cost of solar grade silicon accounts for approximately one third of the total solar cell cost, therefore a new silicon refining process is being proposed with the goal of lowering the cost of producing solar grade silicon.
In this new process, Si-Cu alloys were used as the silicon source. One to one molar ratio H2-HCl gas mixtures were used as transport agents to extract Si out from the Si-Cu alloy at about 300-700oC, with following reaction taking place:
Si+3HCl(g)=HSiCl3(g)+H2(g)
While at about 1000-1300oC, pure Si deposits onto a hot silicon rod according to:
Si+3HCl(g)=HSiCl3(g)+H2(g)
The role of the copper in the alloy was to trap impurities in the Si and catalyze the gas solid reaction. A study on determining the rate limiting step and impurity behavior was done. A possible silicon extraction reaction mechanism was also addressed.
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Tseng, Tzu-Yao, and 曾咨耀. "Growth Graphene by Chemical Vapor Deposition." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/53605718041228234463.
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