Dissertations / Theses: 'Thin solid film measurement'

1

Hughes-Davies, T. T. "An X-ray reflectometer for the study of liquid surfaces." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234985.

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2

Taplin, Stephen. "Measurement of thin oil films using fibre-optic interferometry." Thesis, University of Kent, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360976.

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3

Ellgren, Alex. "Analysis of vortex movement in an YBCO thin film : Models of the vortex solid-to-liquid transition compared to a sensitive resistive measurement of a strongly pinned YBCO thin film." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-140589.

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When a high-temperature superconductor transitions in the presence of a magnetic field, the resistance does not immediately go to zero. Instead, the transition is smoothed by the resistive effects of moving vortices so that perfect conductivity isn't reached until several K below Tc, where the vortices have frozen into a glass state. The properties of this glass depend mainly on the amount and correlation between impurities in the superconductor. This report describes a study of the glass transition in an YBCO thin film rich in uncorrelated impurities. The aim was to use sensitive resistive measurements to determine which of two models of this transition, the vortex glass model and the vortex molasses model, is more accurate. After evaluation, both models are found lacking and a third model is put forth. This model, which resembles the normal distribution, excellently describes the YBCO thin film case. When the new model is tested against data from similar measurements, an YBCO single crystal and a TlBaCaCuO thin film, the results are mixed. Further study is suggested to determine the model's range of validity.

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4

Attrill, K. J. "Ellipsometric and photometric techniques for the measurement of the optical constants of thin films and surfaces." Thesis, University of Bradford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376351.

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5

Ismail, Bakar Bin. "Electrical conductivity measurements in evaporated cadmium telluride thin films." Thesis, Keele University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293964.

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6

Bozeat, Robert John. "Thin film optical waveguides on silicon." Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320551.

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7

Gu, Erdan. "Studies in thin film systems and X-ray multilayer film design." Thesis, University of Aberdeen, 1992. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU547604.

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The design and optimization of soft X-ray multilayer film mirrors have been studied using optical theory. Our investigations show that the reflectivity of multilayer films is sensitive to their modulation wavelength and that their reflectivity can be improved by structural optimization. A new design method has been developed which can be used to increase the bandwidth and to change the shape of the reflectivity curves of multilayer film mirrors. Detailed studies of the formation and structure of practical vacuum deposited erbium(Er) thin film systems are presented. It was found that the phase and structure of these deposited films are strongly influenced by deposition conditions and film thickness. On the basis of these studies, very high purity low thicknesss erbium films (&'60 300 AA) with h.c.p. structure have be grown for the first time. The preferred orientation of crystallites and its dependence on deposition conditions in these erbium films are also investigated in detail. We have prepared Er/C multilayer films using the ultra high vacuum electron beam evaporation technique. The compositional periodic structure and intra-layer structure of these multilayer films have been studied using X-ray diffraction. The diffusion and short-range order formation occurring at the interfaces and within layers of C-Er thin-film systems and Er/C multilayer films were investigated by extended X-ray absorption fine structure technique (EXAFS).

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Pottage, John Mark. "Analysis of thin-film photonic crystal microstructures." Thesis, University of Bath, 2003. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269994.

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9

Sugden, Stephen. "Thin film adhesion modification by MeV ions." Thesis, University of Surrey, 1991. http://epubs.surrey.ac.uk/843281/.

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The adhesion of a thin films, and in paiticular the way in which such adhesion may be improved by irradiation, is a rather poorly understood field of thin film technology. The radiation enhanced adhesion effect has been investigated through the use of Ultra High Vacuum sample preparation, analysis and irradiation techniques, in order to gain control over surface and interface composition. In the systems studied, films deposited on atomically clean surfaces show good adhesion, and no evidence of enhancement due to irradiation is observed in the case of such clean interfaces. The results are entirely consistent with the radiation enhanced adhesion phenomenon being due to radiolytic effects on contaminant containing layers at the film/substrate interface. In addition, on silicon substrates the observations highlight the superiority of thermal cleaning over low energy sputtering as a route for producing a clean surface. A model of the radiation enhanced adhesion observations for dirty interface systems is developed, which takes into account the two dimensional nature of the ion energy deposition process. All the observations on such systems are broadly consistent with an activation energy for the process of approximately 5eV. This value is sufficiently large to bring about chemical bonding rearrangement at the critical film/substrate interface.

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10

Beckel, Daniel. "Thin film cathodes for micro solid oxide fuel cells." kostenfrei, 2007. http://e-collection.ethbib.ethz.ch/view/eth:29741.

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11

Flack, Natasha. "Thin film components for solid oxide fuel Cells (SOFCs)." Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/2007271/.

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Thin film components for solid oxide fuel cells (SOFCs) have been investigated in this thesis. This work focuses on electrolyte materials such as samarium doped ceria (SDC) and cathode materials including neodymium barium cobalt oxide (NBCO) and barium calcium yttrium iron oxide. Single layer growth of NBCO or SDC is achieved on single crystal strontium titanate (001) before these materials were grown via pulsed laser deposition as a bi-layer and multilayers. Ordered NBCO required deposition at 850°C, whereas it was found that the SDC grew with a lower surface roughness at lower temperatures of around 650°C. The motivation was to investigate how the conductivity is affected by the interfaces between these layers, as motivated by previous studies of yttrium stabilised zirconia (YSZ) with strontium titanate (STO). NBCO was found to be unstable at the temperatures required for AC impedance measurements. From the transmission electron microscopy (TEM) and Energy Dispersive X-ray (EDX) data there is likely migration of Nd into the SDC layers. The interfaces are also less sharp for the multilayer films deposited at the higher temperature for the SDC growth. However, in all cases the SDC growth appears more favourable in the TEM when compared to the NBCO, with some regions even showing Co-metal and fluorite structures potentially attributed to Co-Ox where we would expect to see the perovskite block. Thin films of barium calcium yttrium iron oxide were grown on single crystal strontium titanate (001). The material is a candidate cathode for solid oxide fuel cells (SOFCs) and in the intermediate temperature (IT) region at 600°C the in-plane AC conductivity of the thin film is found to be 30.0Scm-1, significantly enhanced over 3.5Scm-1 found for the polycrystalline form. This is assigned to reduction of the grain boundary density and alignment of the planes predicted to have the highest electronic and ionic conductivities. The symmetry of the film appears to be tetragonal within the resolution of the measurements employed, as opposed to the orthorhombic symmetry of the bulk phase, which may be attributed to the in-plane structural match between the cubic STO substrate and the grown layer. Three potential geometries investigating both single and double-sided growth for measuring the area specific resistance of thin films are discussed and an experimental prototype constructed and tested.

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12

Blanchet, Aaron R. (Aaron Robert) 1974. "Microelectromechanical (MEMS) structures for thin film property measurement." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9735.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1998.
Includes bibliographical references (leaf 87).
Microelectromechanical systems (MEMS) are becoming the bases for an important industry with potential applications in numerous fields. The current study explores the use of MEMS-based, electrically-actuated structures to determine thin film mechanical properties, including intrinsic stresses of deposited metal films. An overview of the importance of thin film stress measurement and the advantages of this particular MEMS-based technique provides motivation for this study. A new analysis of the mechanics in bilayer beams is presented, and is used to relate changes in electrical measurements to the intrinsic stress of films deposited on micromachined beams. Proof-of-principle studies using evaporatively deposited silver films were carried out, and showed agreement in stresses measured using different MEMS-based devices, but the same beam analysis. Stress was measured through experiments using electrical "pull-in" of beams and results are compared both to curvature studies using MEMS-based cantilevers and to standard wafer-based, scanning-laser curvature analysis. Thermal cycling was performed on all the devices, yielding data suggesting different rates of thin film stress relaxation for the films deposited on MEMS-based devices and a film on an oxidized Si wafer. Differences in stress relaxation rates are attributed to the different interfaces involved. These studies point to future work which will lead to optimized MEMS-based devices to be used for high-sensitivity, in-situ, thin film stress measurements.
by Aaron R. Blanchet.
S.M.

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13

McQuillan, Scott. "Electromagnetic waves in Langmuir Blodgett thin film microstructures." Thesis, Queen Mary, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271335.

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14

Sethu, Murugesan. "Performance studies of thin film electroluminescent (TFEL) devices." Thesis, Nottingham Trent University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250453.

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15

Yalamanchili, Hyma. "Dynamic bandgap tuning of solid thin film photonic crystal structures." Morgantown, W. Va. : [West Virginia University Libraries], 2010. http://hdl.handle.net/10450/10976.

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Thesis (M.S.)--West Virginia University, 2010.
Title from document title page. Document formatted into pages; contains viii, 95 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 89-95).

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16

Simrick, Neil Jonathan. "Patterned thin film cathodes for micro-solid oxide fuel cells." Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/11910.

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17

Akizuki, Makoto. "Gas Cluster Ion-Solid Surface Interaction and Thin Film Formation." Kyoto University, 1999. http://hdl.handle.net/2433/181783.

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18

Loh, Kian Ping. "Growth studies and surface modification of thin film diamonds." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320658.

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19

Farrar, Simon Richard. "Excimer laser ablation characterisation for superconducting thin film applications." Thesis, University of Hull, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282366.

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20

Xu, Jiansheng. "Characterisation and magneto-optical enhancement of thin film TbFeCo." Thesis, Queen's University Belfast, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317538.

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21

Rose, John. "Nanomagnetic and nanostructural studies of thin film magnetic systems." Thesis, University of Glasgow, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241740.

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22

Zahrir, A. "Thin film growth and characterization on high temperature superconductors." Thesis, University of Bristol, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335477.

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23

Huq, Syed Ejazul. "Thin film deposition by the ionized cluster beam method." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304288.

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24

Coxon, Penelope Anne. "Polycrystalline silicon thin-film transistors for large-scale microelectronics." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358595.

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25

Lee, Wen-Chieh. "Thin film adhesion measurement using excimer laser ablation test /." Online version of thesis, 1991. http://hdl.handle.net/1850/11034.

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26

Heutz, Sandrine Elizabeth Monique. "Structural, spectroscopic and morphological properties of molecular thin film heterostructures." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252184.

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27

Swift, Michael Joseph Robert. "Aspects of single crystal and thin film high field electroluminescence." Thesis, University of Hull, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304437.

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28

Kilvert, Paul Vyvyan Andrew. "The synthesis and evaluation of Langmuir-Blodgett thin film materials." Thesis, University of Hull, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292691.

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29

Connolly, M. P. "Surface plasmon polaritons in thin film structures : calculations & experiment." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333810.

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30

Al-Samarrie, A. K. "The application of thin film and microwave technology in instrumentation." Thesis, University of Salford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334054.

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31

Gottschalg, Ralph. "Environmental influences on the performance of thin-film solar cells." Thesis, Loughborough University, 2001. https://dspace.lboro.ac.uk/2134/35675.

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The response of thin-film photovoltaic devices to changes in the environment is not well understood. There are a large number of conflicting reports, reflecting largely the superimposed nature of the environmental effects. A separation of the effects is not often attempted mainly because of the lack of appropriate spectral data. An experimental system has been designed and operated to facilitate the separation of the environmental effects, including spectral effects. This involves measurements in a controlled laboratory environment as well as outdoor monitoring. Furthermore, a number of analysis tools have been developed and tested for their suitability. In order to develop a system model, the applicability of parametric models for thin-film devices is probed. The thermal variation of the underlying physical parameters is investigated and problems of describing thin-film devices with parametric models are discussed.

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32

VAN, MILLIGEN FRED JOSEPH. "IN-SITU MONITORING OF THIN FILM GROWTH USING A WIDE-BAND SCANNING MONOCHROMATOR." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/188057.

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To augment the monitoring capabilities of a Balzers 760 coating chamber, we replaced the simple, single wavelength optical monitor with a wide-band scanning monochromator system which records transmission data over the visible region of the spectrum. The system is controlled by an IBM-PC. The same computer is also interfaced to a quartz crystal monitoring system which was purchased with the Balzers chamber. The scanning monochromator system required a new brighter light source to deliver sufficient signal to the detector array through the more complex, dispersive optical train. Above the chamber the filter and the photomultiplier pair were removed, and replaced by a flat mirror which diverts the beam horizontally into the scanning monochromator system. The beam passes first through a telescope-slit configuration onto a Jobin-Yvon holographic grating, built to disperse the 400-800 nm band of which we use approximately 360 nm. This reflective grating images the spectrum of the slit onto a Fairchild CCD array, which consists of 1728 elements. These elements are then averaged into 173 data points and recorded by the IBM-PC. The 173 data points allows us a wavelength resolution of about 2 nm. The IBM incorporates a Tecmar A/D board in accepting data from both the quartz crystal monitor and the scanning monochromator system. Although the system is capable of recording data at a faster rate, it is generally stored once every three seconds. This is adequate since at normal deposition rates this gives us information every 10 - 20 Angstroms of deposited material. The system has been used in several applications which will be discussed in this dissertation. They include in situ measurements of water adsorption into a film, derivation of optical constant profiles during the film deposition, both of which may lead us to a better understanding of the growth of a thin film. The monochromator has also been used to analyze the components of a multilayer coating by monitoring the film's transmission spectra while it was sputter-etched off. The extension of the system into the ultraviolet region of the spectrum and some future applications are also considered.

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Ewing, Jerrod Albert. "Development of a Direct-Measurement Thin-Film Heat Flux Array." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/30918.

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A new thin film heat flux array (HFA) was designed and constructed using a series of nickel/copper thermocouples deposited onto a thin KaptonÂ® polyimide film. The HFA is capable of withstanding temperatures up to 300 Â°C and produces signals of 42 μV/(W/cm2). As a result of its thin film construction, the HFA has a first order time constant of 32 ms. Calibrations were completed to determine the gageâ s output as well as its time response. In order to measure the signal from the HFA amplifiers were designed to increase the magnitude of the voltage output. An example case is given where the HFA is used in an experiment to correlate time-resolved heat flux and velocities.
Master of Science

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34

Clough, Francis John. "The performance and stability of hydrogenated amorphous silicon thin film transistors." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386233.

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35

Giles, Luis Felipe. "Characterization and control of crystallographic defects in thin film SIMOX materials." Thesis, University of Surrey, 1994. http://epubs.surrey.ac.uk/844322/.

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Crystallographic defects present in the silicon over layer of thin (< 1000 A) SIMOX material have been characterized using a newly developed etchant and by transmission electron microscopy. Rutherford backscattering spectroscopy has also been used to determine the chemical composition and thickness of the synthesised layers. The thin SIMOX layers were produced by two different methods, namely (i) sacrificial oxidation of the silicon over layer of thick (2000 A) SIMOX films and (ii) low energy O+ implantation. The main crystallographic defects present in materials prepared by sacrificial oxidation are threading dislocations and oxidation induced stacking faults (OISF) whose density and size depends mainly upon the oxidation conditions (temperature, time) and also on the number of nucleation sites present before oxidation. The nucleation of these OISF has been investigated and it has been observed that stacking fault (SF) complexes are the main nucleation sites. The density of threading dislocations within the Si over layer does not increase during oxidation. The lowest density of OISF (5.0x102 cm-2) was observed in layers thinned by dry oxidation although some layers contained up to 5.0x105 cm-2. This difference in OISF densities was attributed to differences in the densities of the SF complexes before oxidation. Thin film SIMOX structures formed by low energy implantations also contain two principal defect types namely, threading dislocations and stacking fault complexes, where the densities depend upon the implantation and annealing conditions, A low density of threading dislocations is only obtained when parameters, such as dose and implantation temperature are optimised. Furthermore, it is also observed that thermal and mechanical stresses produced in the silicon over layer during implantation or annealing, need to be minimised in order to obtain low defect density material. It has been shown by whole wafer defect mapping of six inch SIMOX wafers implanted under optimised conditions, that a uniform distribution of defects can be achieved, having an average defect density as low as 1.0x104 cm-2. Additionally, the effects of implantation damage on the formation of secondary defects have also been investigated. The results have shown that the coalescence of point defects generated during implantation produce a high density of dislocation loops that, depending upon the annealing treatment, develop into threading dislocations or OISF. These experiments confirm that careful optimisation of the processing conditions, such as implantation temperature and dose uniformity, can significantly reduce defect densities thus enhancing the prospect of thin film SIMOX as a suitable substrate for fully depleted MOS devices.

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36

Cao, Jing. "Growth, characterization and measurement of epitaxial Sr2RuO4 thin films." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/274542.

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In this thesis, the growth of c-axis oriented Sr2RuO4 thin films using pulsed laser deposition and their electrical transport properties are systematically discussed. The deposition and optimization process involved several progressive steps. Specifically, the first focus was on the Sr2RuO4 phase optimization in films grown on lattice-matched (LaAlO3)0.3(SrAl0.5Ta0.5O3)0.7 (LSAT) substrates. Film composition was found to be greatly influenced by changes in oxygen pressure, substrate temperature, target to substrate distance, and laser fluence. High oxygen pressure, low substrate temperature, large target to substrate distance, and high laser fluence increased the tendency to form the Ru-rich SrRuO3 phase in the film. The second focus was on improving the electrical transport properties of Sr2RuO4 from metal-insulating to fully metallic and eventually to superconducting behavior. It was observed that the full width at half maximum (FWHM) of the Sr2RuO4 (006) rocking curves in x-ray diffraction (XRD) scan was related to the quality of the electrical transport response. By fine tuning the deposition parameters to obtain low FWHM values, the electrical transport behavior of the Sr2RuO4 thin films was consistently improved from metal-insulating to fully metallic. In addition, localized superconductivity with enhanced superconducting transition temperature Tc onset was also observed among the fully metallic film. An in-depth study of the XRD results in fully metallic films indicated the existence of defects (intergrowths) along the c-axis direction, which caused localized c-axis tensile strain. The existence of structural defects within the film was likely to be responsible for the fact that only localized superconductivity was observed in the films. Furthermore, the enhanced superconducting transition temperature (Tc) relative to bulk single crystals is likely to be associated to localized strain in the film. Finally, Nb doped SrTiO3 substrates were used to achieve better quality growth of partial superconducting Sr2RuO4 thin films. Sr2RuO4 films grown on Nb doped SrTiO3 substrates had smaller FWHM values and lower level of c-axis tensile strain compared to those on LSAT substrates. Various partially superconducting films with different thicknesses and different superconducting Tc values are presented, and correlations between fabrication process, film crystalline quality as well as transport properties are discussed. This work provides better understanding of the importance of maximizing crystalline quality by delicate fine tuning of PLD deposition parameters to achieve high quality superconducting films.

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Hadland, Erik. "Thin Film van der Waals Heterostructures containing MoSe2 from Modulated Elemental Precursors." Thesis, University of Oregon, 2019. http://hdl.handle.net/1794/24520.

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Transition metal dichalcogenides (TMDs) are naturally occurring layered materials that have attracted immense research interest due to their high degree of chemical tunability. In particular, MoSe2 has been the focus of significant investigation stemming from reports that it converts to a direct band gap semiconductor material at ultralow dimensions. Yet, as more and more is learned about increasingly thin MoSe2, efforts are now aimed at imparting the novel functionality of MoSe2 into van der Waals heterostructures. This dissertation focuses on synthesis and characterization of novel MoSe2-based nanolaminate structures that have been self assembled from modulated elemental precursors. The first section describes a new treatment of x-ray fluorescence spectroscopy data and its use as a powerful probe for determining the absolute composition per unit area of a thin film with sub-monolayer accuracy. While this has widespread application in the thin film world, it is particularly useful for MER synthesis in the calibration of modulated elemental precursors. In order to crystallize a target structure, it is imperative to deposit the correct number of atoms, which is now possible with greater precision. The second section shows the importance of rotational (i.e. “turbostratic”) disorder on lowering cross-plane thermal conductivity in two systems—MoSe2 and the (SnSe2)1(MoSe2)1.32 heterostructure. The binary systems exhibits ultralow thermal conductivity that rivals that of WSe2, yet some interlayer atomic registry was noted in TEM images. By interleaving layers of MoSe2 with SnSe2—which also possesses hexagonal symmetry, but has a significantly larger basal plane—the cross-plane thermal iv conductivity was depressed to the lowest reported value in the literature for a fully dense solid. The final section presents the synthesis and characterization of a new, ternary phase of Bi|Mo|Se. The structure consists of alternating layers of a “puckered” rock salt BiSe lattice and nanosheets of MoSe2. Notably, the MoSe2 sublattice consists of a mixture of the semiconducting 2H phase (~60%) and the metallic 1T phase (~40%). This is the result of electron injection from the BiSe into the conduction band of the MoSe2, which is known to undergo a rearrangement upon reduction. This dissertation includes previously published and unpublished coauthored materials.
2021-04-30

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38

Yoon, Jongsik. "Nanostructured thin films for solid oxide fuel cells." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3164.

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Kunz, Oliver Photovoltaics &amp Renewable Energy Engineering Faculty of Engineering UNSW. "Evaporated solid-phase crystallised poly-silicon thin film solar cells on glass." Publisher:University of New South Wales. Photovoltaics & Renewable Energy Engineering, 2009. http://handle.unsw.edu.au/1959.4/43644.

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The cost of photovoltaic electricity needs to be significantly reduced in order to achieve a high electricity market penetration. Thin-film solar cells have good potential to achieve such cost savings though (i) large-area deposition onto low-cost foreign substrates, (ii) more streamlined processing, (iii) monolithic cell interconnection, and very efficient use of the expensive semiconductor material. Polycrystalline silicon (poly-Si) on glass is a promising technology for the cost-effective large volume production of PV modules since it (i) makes use of an abundant raw material, (ii) is non-toxic, (iii) does not suffer from light-induced degradation, and (iv) does not rely on TCO layers. Usually plasma enhanced chemical vapour deposition (PECVD) is used for the layer formation. This thesis explores the use of e-beam evaporation as deposition method since it is potentially much faster and cheaper than PECVD. The resulting solar cells are referred to as EVA (from EVAporation). Two inherent shunting mechanisms in EVA cells are demonstrated to be shunting through sub-micron sized pinholes when the back electrode is deposited and shunting between the emitter and the absorber layer at the glass-side electrode. Through the improved understanding of these shunting mechanisms it was possible to develop a suitable metallisation scheme for EVA cells using an aligned deposition of emitter and back surface field line contacts and a specially developed shunt mitigation etching technique. For the first time appreciable efficiencies of up to 5.2% were demonstrated on this material. It was also shown that only very lightly doped absorber layers can lead to the required high short-circuit currents in EVA cells. The resulting cells are currently completely limited by space charge region recombination occurring with comparatively low ideality factors of only ~ 1.4 This thesis also demonstrates the usefulness of Jsc-Suns measurements and investigates optical loss mechanisms in the current devices. Advanced modelling of distributed series resistance effects, influencing Suns-Voc, m-Voc and Jsc-Suns curves, is employed. PC1D modelling is used to extract relevant device parameters. In this work it was found that the diffusion length in the best EVA cells is longer than the absorber layer and that insufficient light trapping is currently the major hurdle to higher cell efficiencies. From the obtained results it can be concluded that EVA solar cells are promising candidates for the low-cost and high-volume production of solar modules.

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40

Bagge-Hansen, Michael. "Enhanced Field Emission from Vertically Oriented Graphene by Thin Solid Film Coatings." W&M ScholarWorks, 2011. https://scholarworks.wm.edu/etd/1539623349.

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Recent progress and a coordinated national research program have brought considerable effort to bear on the synthesis and application of carbon nanostructures for field emission. at the College of William and Mary, we have developed field emission arrays of vertically oriented graphene (carbon nanosheets, CNS) that have demonstrated promising cathode performance, delivering emission current densities up to 2 mA/mm2 and cathode lifetime >800 hours. The work function (&phis;) of CNS and other carbonaceous cathode materials has been reported to be &phis;∼4.5-5.1 eV. The application of low work function thin films can achieve several orders of magnitude enhancement of field emission.;Initially, the intrinsic CNS field emission was studied. The mean height of the CNS was observed to decrease as a function of operating time at a rate of ∼0.05 nm/h (I 1∼40 muA/mm2). The erosion mechanism was studied using a unique UHV diode design which allowed line-of-site assessment from the field emission region in the diode to the ion source of a mass spectrometer. The erosion of CNS was found to occur by impingement of hyperthermal H and O neutrals and ions generated at the surface oxide complex of the Cu anode by electron stimulated desorption. Techniques for minimizing this erosion are presented.;The Mo2C (&phis;∼3.7 eV) beading on CNS at previously reported carbide formation temperatures of ∼800??C was circumvented by physical vapor deposition of Mo and vacuum annealing at ∼300??C which resulted in a conformal Mo2C coating and stable field emission of 1∼50 muA/mm2. For a given applied field, the emission current was >102 greater than uncoated CNS.;ThO2 thin film coatings were presumed to be even more promising because of a reported work function of &phis; ∼2.6 eV. The fundamental behavior of the initial oxidation of polycrystalline Th was studied in UHV (p<1x10-11 Torr), followed by studies of thin film coatings on Ir and thermionic emission characteristics. Although a work function of 3.3 eV was determined by a RichardDushman plot, activation of the thin film was not achieved at T<1700??C. Rather, the deposited ThO2 film decomposed, surface diffused and aggregated into stable ThO2(111) crystallites.;Thin film ThO2 coatings deposited on CNS initially demonstrated excellent field emission (up to ∼2 muA/mm2) and apparently activated spontaneously without significant thermal energy. Fowler-Nordheim plots suggested a work function of &phis; ∼2.6 eV. Undesired beading and ThO2 surface diffusion away from active emission sites resulted in rapidly deteriorating performance at higher field emission currents. Techniques that should provide a more stable ThO2/CNS conformal coating are presented.;The impact of thin films of Mo2C and ThO2on the magnitude of field emission from carbon nanosheets (CNS) was substantial. For a given field emission current density, J ∼2 muA/mm 2, the necessary applied field for uncoated CNS was ∼12 V/mum, but only ∼8 V/mum when coated with Mo2C (&phis;∼3.7 eV) and ∼5 V/mum when coated with ThO2 (&phis;∼2,6 eV). The mechanism for enhanced emission and the stability of the coatings are discussed, with special focus on the activation of ThO2 thin films. The major limitation observed in these studies has been the difference in surface energy of the graphene and the coatings which resulted in a tendency for the films to bead and separate from active emission sites at elevated currents. Suggested techniques to prevent this unwanted surface diffusion are presented.

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41

Zaidi, Syed Zulfiqar Ali. "Electrical and optical properties of some metal/SiOâ†x thin film systems." Thesis, Brunel University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307488.

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42

Pohl, John E. T. "The electrical properties of bulk polycrystalline and thin film high temperature superconductors." Thesis, University of Nottingham, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315041.

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43

Ma, Jun. "The deposition and electro-optical properties of thin film zinc sulphide phosphors." Thesis, University of Ulster, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388877.

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44

Bayhan, Murat. "Preparation and characterisation of n-CdS/p-CdTe thin film solar cells." Thesis, Durham University, 1994. http://etheses.dur.ac.uk/1697/.

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45

Marks, Robert Neil. "The optical and electronic response of poly(p-phenylene vinylene) thin film devices." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308338.

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46

Levoguer, Carl Louis. "An investigation of surface reaction mechanisms during thin film growth of compound semiconductors." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260715.

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47

Ma, Yong Qing. "Investigation into the materials and manufacturing of a new thin film magnetoresistive sensor." Thesis, University of Plymouth, 1998. http://hdl.handle.net/10026.1/2834.

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There is increasing interest in utilising very thin anisotropic magnetoresistive films (typically in the range of a few nano-metres) to make magnetic sensors which can be made very small and with a high signal-to-noise ratio. In this thesis, a new type of sensor is investigated which has a pair of thin film MR stripes whose magnetisation is switched alternately in opposite directions using bias fields from currents in overlay conductor films. The investigation considers in particular the Barkhausen noise in these sensors and its relationship with factors such as sensor film thickness. The effect of thickness and grain size on the coercivity of Ni81Fe19 permalloy thin films deposited by r.f. sputtering with negative substrata bias is systematically investigated as a function of under-layer materials, thickness, and substrata temperature. The results show that there is a minimum in coercivity at a thickness of about 7.5 nm with a grain size of 4 nm. This may be attributed to the grain size via its relationship with magnetic domain wall thickness. A tantalum under-layer favours a (111) (low anisotropy) surface plane in permalloy sensor films. Elevated deposition temperature may reduce defects in the films. A comparison of the magnetic domain wall structure and the state of magnetisation in the very thin (5 - 30 nm) permalloy films with and without Ta underlayer is made by using Lorentz TEM observation. The result shows that it is different in both cases. With Ta underlayer, the wider, straighter and more regular domain walls together with less rippling in magnetisation in adjacent domains may lead to a reduction in the Barkhausen noise. Barkhausen noise studies of films are carried out by sweeping an ac field of 77 Hz onto the permalloy films and recording the induced output voltage due to the flux change as a function of time on a digital storage oscilloscope. Barkhausen noise and corresponding hysteresis of the sensor is studied by analysis of the MR response of various sensors together with their magnetoresistive hysteresis, which may be reduced or improved by using a suitable external high frequency field (5 kHz to 20 kHz). Variation in the sensitivity of the sensor to the magnitude of a switched-biasing field was measured by applying a very small alternating field (from about tens to a few hundreds of nano-Tesla) at frequency above about 250 Hz and varying a transverse de field component (δH.), The effect of biasing field frequency and external linearising field on the sensitivities of these MR sensors is studied using an in-house built measurement system. Highly sensitive magnetoresistive sensors (120 different types have been available within 30 substrates) have been designed and then fabricated by photolithography in a temperature and humidity controlled clean room. Sensor thicknesses are typically in the range from 5 nm to 40 nm and other dimensions typically (10 µm - 80 µm wide) and 6.4 mm long. The sensor is linear in the range from zero to 14 400 nT. It produces an almost noise-free output of 20 to 30 millivolts for a field change of about 160 nano-Tesla.

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48

Muirhead, Ian T. "An evolution in molecular beam epitaxy (MBE) techniques for optical thin film coatings." Thesis, Heriot-Watt University, 1991. http://hdl.handle.net/10399/849.

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49

Al-Achkar, Mohamed. "Efficiency enhancement and degradation processes in Cuâ†xS/CdS thin film solar cells." Thesis, University of Hull, 1990. http://hydra.hull.ac.uk/resources/hull:3703.

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An investigation has been made into the structure and properties of polycrystalline CuxS-CdS solar cells in order to develop an improved understanding of some of the processes which lead to unsatisfactory reproducibility and long term stability of the characteristics of these devices. The cells studied during this project were fabricated using vacuum evaporation for production of the CdS base layer and the well known chemical exchange process in a CuCl solution for formation of the CuxS layer. In view of the non-uniform thickness of the CuxS layer and non-planar structure of the Cu, S-CdS interface, it was found to be necessary to employ a variety of different characterisation techniques to monitor changes in the structure and properties of the devices. These techniques included I/V, C-V, spectral response and sheet resistance measurements, electrochemical analysis, cathodoluminescence spectroscopy and Rutherford backscattering. Detailed consideration was given to the influence of the conditions of formation on the properties of each cell component, in order to establish procedures necessary for the production of reproducible structures. particular attention was paid to the rate of growth of the CuxS layer and a theoretical analysis was developed to account for the time dependence of the growth in mean thickness of the CuxS layer in terms of the contributions associated with growth at the surface of the CdS layer and in the CdS grain boundary regions. The grain boundary contribution was found to be very sensitive to the CdS grain structure and to the previous treatment given to the CdS layer. Pre-annealing in air at 2000C enhanced the grain boundary penetration while the effect of ion implantation (with either Cu or Zn ions) was found to depend on the initial structure and the implantation conditions, but substantial improvements in the photovoltaic conversion efficiency were shown to be possible as a result of such treatment.The rate of degradation of cells exposed to air was also found to be dependent on the previous history of the cell. An increased concentration of Cd in the CuxS film (due to diffusion from the CdS layer) appeared to reduce the rate of qegradation while use of the standard stabilizing treatment (deposition of Cu overlayer followed by annealing in air) was shown to reduce interfacial diffusion as well as protecting the front surface of the CuxS layer against oxidation.

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50

Catlow, Brendan. "The determination of infrared optical constants of some liquids and thin-film solids." Thesis, Durham University, 1986. http://etheses.dur.ac.uk/7107/.

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Fourier transform infrared techniques have been applied in order to determine the optical constants of several liquid and thin-film solid systems over infrared frequencies. In the far infrared region, dispersive interferometry has been employed leading to the derivation of both real and imaginary parts of the complex refractive index in one experiment. As an extension to this, a method has been devised for the analysis of ‘full interferograms' involving multiple internal reflections that inevitably arise for normal transmission through thin parallel specimens. A program has been written which constrcts a theoretical complex insertion loss for the system understudy and then performs an iteration on estimated values for absorption coefficient and refractive index. Results are presented for several liquids analysed using this technique. The bandshapes of pure acetonitrile and benzene have been studied in the far infrared region of the spectrum. This was as a consequence of claims in the literature [83,84] that discernable structure in such bandshapes indicated the presence of long-ranged order in molecular liquids. Bandshapes have been produced using both non-dispersive and dispersive transmission, and spectra from both experiments have been averaged. These are presented together with the standard deviation on the mean. It is concluded that there is no evidence for real structure above the level of the noise in the spectra. The collision-induced spectrum of iodine in benzene has been studied in the far infrared region. Subsequent analysis has been done in both the frequency domain and the time domain in order to examine the nature of the intermolecular interactions and the time evolution of the relaxation processes. Experimental intensity and second moment data have been found to agree well with those predicted by a theory based only on classical electrostatic forces of attraction. Spectra have been modelled using two approaches for solving the generalised Langevin equation. The fits were found to be reasonable and the fitted parameters have been used to study the interactions involved in the system. A mid infrared study of Langmuir-Blodgett films has been undertaken, involving layers of w-tricosenoic acid on a silicon substrate. Anomalies in the carbonyl intensities for the first few layers have been attributed to the partially polarised nature of the incident radiation, and have been used to study the orientation of the fatty acid molecules relative to the substrate surface. A variable temperature cryostat with sample-holder has been interfaced with a Beckmann FS720 interferometer. This has been used to measure the optical constants of several solids over a limited frequency range in the far infrared.

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