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McKinley, Iain Stewart. "Studies in thin film flows." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366911.
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Boff, Arthur. "Electrochemical studies of thin-film diamond." Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496830.
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Inameti, E. E. "Thermal studies of thin film fuses." Thesis, University of Nottingham, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234026.
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Ullah, Hanif. "Simulation studies of photovoltaic thin film devices." Doctoral thesis, Universitat Politècnica de València, 2015. http://hdl.handle.net/10251/48800.
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To cope with energy requirements the utilization of renewable energies, particularly the Sun supplies the biggest and abundant energy source in Earth. Photo-voltaic and solar cell are the well advance and burning technology and a field of hot research. Majority of research centers and universities are working in this field. 1G, 2G, 3G and next generation of photo-voltaic cells have been developed and still to improve its efficiency and to decrease it 0.2 $/W cost.
Our work mainly based on the theoretical and physical analysis of thin-film Photovoltaic devices. We will explore different software used for the analysis of PV cells, and will analyse different simulation related to solar cells like open circuit voltage VOC, Short circuit current JSC, Fill Factor FF (%) and external Quantum efficiency (%) for thin film solar cell including CIGS, CIS, CGS, CdTe, SnS/CdS/ZnO etc. To have different analysis for different combination and different replacement for materials used in the solar cell fabrication. To cope with the PV cost and environmental hazards we have to find alternate solutions.Ullah, H. (2015). Simulation studies of photovoltaic thin film devices [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48800
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Yoshiikawa, Osamu. "Studies on organic thin film solar cells." Kyoto University, 2009. http://hdl.handle.net/2433/123895.
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Kyoto University (京都大学)0048
新制・課程博士
博士(エネルギー科学)
甲第14742号
エネ博第195号
新制||エネ||44(附属図書館)
UT51-2009-D454
京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻
(主査)教授 八尾 健, 教授 石原 慶一, 教授 辻井 敬亘
学位規則第4条第1項該当
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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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Newson, Pamela Lynn. "Studies of diamond film formation." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/30529.
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Barnes, Jean-Paul L. P. Barnes. "TEM studies of thin film oxide/metal nanocomposites." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398136.
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Whyte, Alex. "Thin film studies of planar transition metal complexes." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7966.
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At present the field of molecular electronics - also known as molecular semiconductors, organic semiconductors, plastic electronics or organic electronics - is dominated by organic materials, both polymeric and molecular, with much less attention being focused on transition metal based complexes despite the advantages they can offer. Such advantages include tuneable frontier orbitals through the ligand/metal interaction and the ability to generate stable paramagnetic species. Devices containing radical materials are particularly interesting in order to examine the interplay between conduction and spin - an effect which is not yet properly understood but can give rise to exotic behaviour. A series of homoleptic, bis-ligand Ni(II) and Cu(II) complexes were prepared using three structurally related phenolic oxime ligands, 2-hydroxy-5-t-octylacetophenone oxime (t-OctsaoH), 2-hydroxy-5-n-propylacetophenone oxime (n-PrsaoH) and 2- hydroxyacetophenone oxime (HsaoH). The complexes were characterised by single-crystal X-ray diffraction, cyclic voltammetry, UV/Vis spectroscopy, field-effect-transistor measurements, DFT/TD-DFT calculations and in the case of the paramagnetic species, EPR and magnetic susceptibility. Variation of the substituent on the ligand from t-octyl to n-propyl to H enabled electronic isolation of the complexes in the crystal structures of M(t-OctsaoH)2, which contrasted with π-stacking interactions observed in the crystal packing of M(n-PrsaoH)2 and of M(HsaoH) (M = Ni, Cu). This was further evidenced by comparing the antiferromagnetic interactions observed in samples of Cu(n-PrsaoH)2 and Cu(HsaoH)2 with the ideal paramagnetic behaviour for Cu(t-OctsaoH)2 down to 1.8 K. Despite isostructural single crystal structures for M(n-PrsaoH)2, thin-film X-ray diffraction and SEM revealed different morphologies depending on the metal and the deposition method employed. However, the complexes of M(n-PrsaoH)2 and M(HsaoH) failed to demonstrate significant charge transport in an FET device despite displaying the ability to form π- stacking structures. A series of planar Ni(II), Cu(II) and Co(II) dibenzotetraaza[14]annulenes (dbtaa) and dinapthotetraaza[14]annulenes (dntaa) were synthesised and studied crystallographically, optically, electrochemically and magnetically. Thin films of each of these complexes have been prepared by vacuum deposition to evaluate the field-effect transistor (FET) performance as well as the morphology and crystallinity of the film formed. Single crystal data revealed that Ni(dbtaa) and Cu(dbtaa) are isomorphous to each other, with Co(dbtaa) displaying a different crystallographic packing. The electrochemistry and UV/Vis absorption studies indicate the materials are redox active and highly coloured, with molar extinction coefficients as large as 80,000 M-1cm-1 in the visible region. The paramagnetic Cu(II) and Co(II) complexes display weak 1-dimensional antiferromagnetic interactions and were fit to the Bonner-Fisher chain model. The data revealed that the Co(II) species possesses much stronger magnetic exchange interactions compared with the Cu(II) complex. Each of the materials formed polycrystalline films when vacuum deposited and all showed ptype field-effect transistor behaviour, with modest charge carrier mobilities in the range of 10-5 to 10-9 cm2 V-1 s-1 . SEM imaging of the substrates indicates that the central metal ion, and its sublimation temperature, has a crucial role in defining the morphology of the resulting film. Structurally related Cu(II) and Ni(II) dithiadiazoletetraaza[14]annulene (dttaa) macrocycles were synthesised and studied in the context of their thin film electrochemical, conducting and morphological properties. Both the Ni(II) and Cu(II) complexes were found to be volatile under reduced pressure, which allowed crystals of both materials to be grown and the single crystal structures solved. Interestingly, the crystal packing of these heterocyclic macrocycles varies depending on whether the central metal ion is Cu(II) or Ni(II), which is in contrast to the analogous dibenzotetrazaannulenes complexes. Soluble Ni(II) analogues containing benzoyl groups on the meso- positions of the macrocycle (dttaaBzOR) were also prepared and contrasted with the insoluble Ni(dttaa) complexes in terms of their solution optical and electrochemical properties. Thin film electrochemical studies of Cu(dttaa) and Ni(dttaa) showed chemically reversible oxidative processes but on scanning to reductive potentials the films disintegrated almost immediately as the bulky counter tetrabutylammonium cation entered the thin film. FET studies undertaken on polycrystalline films of both complexes, using various device configurations and surface treatments, failed to realise any gate effect. Thin film XRD measurements indicate that films of both complexes formed by vacuum deposition are crystalline and contain a mixture of molecular alignments, with molecules aligning “edge on” and “face down” to the substrate. SEM imaging failed to effectively resolve the morphology of the films implying the sizes of the crystallites are small, which may help to explain the lack of FET effect. A series of bis-ligand diimine Ni, Cu and Pd complexes have been synthesised from the ligand 4,5-bis(dodecyloxy)benzene-1,2-diamine (dbdaH2). The same ligand was also used to prepare a series of soluble Cu(II) and Ni(II) tetraaza[14]annulene macrocycles. All the bis-ligand diimine complexes were found to suffer from instability in air due to the ease at which the complexes are oxidised. The Ni complex, Ni(dbda)2, was found to display a NIR transition in the region of 971 to 1024 nm depending on the polarity of the solvent that the molecule is dissolved in. Solution electrochemistry studies of Ni(dbda)2 reaffirmed the facile nature of the first oxidative process, with the HOMO energy calculated at -4 eV by hybrid-DFT. This compound failed to yield semiconducting behaviour in an FET device despite the use of surface treatments aimed at promoting suitable molecular alignment across the conducting channel.
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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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Sainju, Deepak. "Spectroscopic Ellipsometry Studies of Ag and ZnO Thin Films and Their Interfaces for Thin Film Photovoltaics." University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1430326934.
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Sugimoto, Yoshiharu. "Studies of CdTe electrodeposition." Thesis, University of Southampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241263.
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Tetali, Bhaskar Reddy. "Stability studies of CdTe/CdS thin film solar cells." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001135.
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Pinitsoontorn, Supree. "3D atom probe studies of thin film magnetic materials." Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492054.
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A combination of TEM and 3D atom probe has been used to study thin film magnetic materials for read head applications. Three different types of magnetic thin films have been investigated: (1) Co-based films for bias magnets, (2) magnetic tunnel junction (MTJ) with . AIOx barrier and (3) MTJ with MgO barrier. Unlike in longitudinal recording media, the Co-based films showed no Cr segregation to grain boundaries. This difference is likely to be due to the addition of Pt, which reduces the miscibility gap of the Co-Cr system, and film deposition at room temperature which reduces . the kinetics of segregation. However, some compositional variations were observed within grains. Increasing the angle of film deposition resulted in lower stress in the film, presumably due to better lattice matching between the magnetic layer and the seed layer. The observed coercivity enhancement with the larger deposition angle is attributed to changes in the resultant microstructure, specifically a smaller average grain size and more in-plane orientation of the magnetic easy axis. In the as-deposited MTJ. with an AIOx barrier, the barrier was found to be a discontinuous layer which was wavy and non-uniform in thickness. The AIOx layer was seen to form an interconnecting network of oxide islands, consistent with the islands forming at the grain boundaries of the underlayer. After annealing, the AIOx layer had become thicker, smoother, more uniform in thickness and contained fewer pinholes. The AI:O ratio changed from approximately 4:3 before annealing to close to the stoichiometry of 2:3 after annealing. Three energy contributions were considered as possible driving force for the transformation of the separated islands into a continuous layer: pinhole geometry, metal/oxide interface energy and strain energy. The improved TMR with annealing was mainly attributed to the improvement in the quality of the barrier. For the MTJ with an MgO barrier, the MgO deposited on a flat amorphous surface showed a [001] texture. The amorphous CoFeB partially crystallised after annealing and formed the (001)[110]CoFeB II (001)[100]MgO II (001)[110]CoFeB orientation relationship in some areas. Variations were observed in the chemistry of the barrier, but this was not as extreme as in the case of AIOx• The Mg:O ratio within the oxide was measured to be approximately 1:1 and was not changed after annealing. B was found to diffuse from the CoFeB layers: this must have occurred during deposition, as its distribution was the same before and after annealing. In the region of high MgO concentration, B was found mostly at the CoFeB/MgO interface and the CoFeB/Ru interface whereas in the region of low MgO concentration, B was found throughout layers. Mn in the AF layer was seen to have intermixed with the CoFe synthetic AF layer. The MgO layer topography was anti-correlated to the Ru layer but the effect decreased during annealing.
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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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Marcham, Max Ken. "Phase-resolved ferromagnetic resonance studies of thin film ferromagnets." Thesis, University of Exeter, 2012. http://hdl.handle.net/10036/3882.
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Precessional dynamics are exploited in the operation of high frequency magnetic devices such as magnetic disk drives, non reciprocal microwave devices and spin transfer oscillators. The trajectory of the precession and its damping are of crucial importance. This thesis presents the characterisation of a variety of magnetic thin film structures performed with a range of phase sensitive techniques. It is possible to obtain new insight by utilising the chemical and site specificity of X-ray Magnetic Circular Dichroism (XMCD) to isolate the precession in different chemical species or at distinct sites in the crystal structure of a chosen material. X-ray Ferromagnetic Resonance (XFMR) combines XMCD and Ferromagnetic Resonance (FMR) phenomena in a technique capable of measuring the FMR response of an alloy or multilayer with both chemical and site specificity. To complement the XFMR technique a low temperature Time-Resolved Magneto Optical Kerr Effect (TR-MOKE) setup has been developed. This allowed for the characterisation of samples at temperatures in the range 4 K to room temperature. A frequency swept Vector Network Analyser FMR (VNA-FMR) setup was developed to allow for a fast method for determining the resonance condition and damping of a range of ferromagnetic thin film samples. In addition a TR-X-ray Photoemission Electron Microscopy (TR-XPEEM) setup has been established which allows images to be obtained with magnetic contrast. The combination of the above techniques has lead to studies on rare earth capped spin valve free layers and the measurement of spin pumping in industrially relevant spin valves.
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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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Chang, Shang-wen. "Cu₂S/ZnCdS thin film heterojunction solar cell studies." Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/54740.
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Cu₂S/CdS solar cells have been studied extensively for the past two decades due to their potentially high efficiencies per unit cost. The operation and characteristics of Cu₂S/CdS solar cells are fairly well understood. However, the properties of the newer Cu₂S/ZnCdS cell type are not well understood.
The main goals of this thesis were to compare Cu₂S/CdS and Cu₂S/ZnCdS cells using Cu₂S/CdS cells as a reference, and to understand the operation and properties of Cu₂S/ZnCdS cells in order to improve cell performance. Four different measurements were used in this research to achieve these goals. They were; electrical, spectral, capacitance and deep trap measurements.
I-V measurements give important electrical parameters of the cells; cell efficiency, fill factor, short circuit current, open circuit voltage, shunt resistance and series resistance are reported. From a In(ISC) versus VOC measurement, the diode factor, A, was found to be about 1 for Cu₂S/CdS, Cu₂S/Zn0.11Cd0.89S, and about 1.2 for Cu₂S/Zn0.25Cd0.75S cells. The relation between In(Joo) (current density) and ϕ (potential barrier height) is linear for both types of cells. The slope of this linear relationship increases as the content of Zn increases in ZnxCd1-xS. Under air mass 1 (100 mW/cm²) illumination, it was found that VOC decays and capacitance increases for Cu₂S/ZnCdS cells. This is attributed to electron relaxation from deep traps near the junction.
Spectral response with and without bias light were measured for both Cu₂S/CdS and Cu₂S/ZnCdS cells. White and blue bias light enhance the spectral response, while red bias light quenches the response. This is attributed to ionization and filling of deep traps near the junction.
Capacitance measurements on both cell types show that 1/C² versus voltage is quite flat, which indicates the existence of an i-layer (insulation layer) in the CdS or ZnCdS near the junction.
Three methods–photocapacitance, space-charge-limited current, and thermally stimulated. current techniques–were used for deep trap measurements. Photocapacitance measurements indicate one deep donor energy and two deep acceptor energy levels. These trap energies become larger as the content of Zn in ZnCdS increases. Space-charge-limited current measurements give a trap density of the order of 10¹⁶ cm³ for both cell types. The shallow energy trap is found to be 0.26 eV below the conduction band edge of CdS. The occurrence of a current-saturated region for Cu₂S/ZnCdS is attributed to the filling of the interface traps near the junction. Thermally stimulated current measurements give two energy levels below the conduction band of CdS; 0.05 eV and 0.26 eV.
From the above results, several differences between the Cu₂S/CdS and the Cu₂S/ZnCdS cells can be seen. The Cu₂S/ZnCdS cells show stronger red quenching, smaller electron lifetime at the interface near the junction, and deeper traps than the Cu₂S/CdS cells. These differences can account for the decline of ISC and the VOC decay. The smaller ISC for the Cu₂S/ZnCdS cells can also possibly result from smaller electron lifetime at the interface, larger interface recombination velocity, different deep trap levels, and enhanced Zn concentration near the junction. The VOC decay for the Cu₂S/ZnCdS cells is mostly due to long decay of charge. Longer decay could be attributed to deeper traps.Ph. D.
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Giri, Dipak. "Single-molecule spectroscopic studies of thin-film chemical gradients." Diss., Kansas State University, 2016. http://hdl.handle.net/2097/35225.
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Doctor of PhilosophyDepartment of Chemistry
Daniel A. Higgins
This dissertation describes the application of single molecule spectroscopy and tracking to investigations of the nanoscale properties of thin-film chemical gradients and the transport dynamics of molecules dispersed within and upon these gradients. Chemical gradients are surface bound materials that incorporate gradually changing chemical and/or physical properties. A continuous and gradual change in the properties of gradients are expected and often required for their intended applications, which range from directed growth of cell colonies to combinatorial materials science. In reality, such conditions are almost never met due to spontaneous demixing and dewetting processes that can lead to properties variations on microscopic length scales. A better understanding on the properties of chemical gradients on microscopic length scales will aid in the production of better engineered materials. Single molecule spectroscopy (SMS) allows for gradient properties to be probed on nanometer-to-micrometer length scales. In this dissertation, quantitative measurements of gradient polarity (i.e., dielectric properties) are made along a sol-gel derived thin film that incorporates a macroscopic polarity gradient. These measurements report on the microscopic heterogeneity of the gradient film, and point to the occurrence of phase separation of the polar and nonpolar components along the gradient. Single molecule tracking (SMT) provides an important means to examine the dynamics of molecular mass transport in thin films and on surfaces. In this dissertation, SMT is employed to study mass transport in thin water films condensed over monolayer wettability gradients under ambient environments. The results show that the rate and the mechanism of molecular transport depend on the surface wettability, and on the ambient relative humidity. Finally, wettability gradients have been broadly used to drive the transport of liquid droplets. In this dissertation, these applications are extended to achieve spontaneous stretching of DNA by the propulsion of liquid droplets along the gradient. Single molecule fluorescence imaging of DNA stretched along these gradients demonstrates that hydrophobic surfaces play an important role in DNA stretching. The study also shows the surface tension force acting at the gradient-droplet contact line (interface) to be responsible for DNA elongation and alignment. Overall, single molecule methods have been shown to be highly useful for better understanding the properties of chemical gradients as described in this dissertation.
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Morris, I. D. "Radiofrequency studies at low and intermediate temperatures." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236305.
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Hatton, Hilary J. "Magnetic and structural studies of nanoscale multilayer and granular alloy systems of Ag and FeCo." Thesis, University of Sheffield, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286916.
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Li, Zuoli. "Studies of Thin Liquid Films Confined between Hydrophobic Surfaces." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/49557.
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Surface force measurements previously conducted with thiolated gold surfaces showed a decrease in excess film entropy (£GSf), suggesting that hydrophobic force originates from changes in the structure of the medium (water) confined between hydrophobic surfaces. As a follow-up to the previous study, surface force measurements have been conducted using an atomic force microscope (AFM) with hydrophobic silica surfaces at temperatures in the range of 10 to 40¢XC. The silica sphere and silica plate were treated by both chemisorption of octadecyltrichlorosilane (OTS) and physical adsorption of octadecyltrimethylammonium chloride (C18TACl). A thermodynamic analysis of the results show similar results for both of the samples, that both ""Sf and excess film enthalpy ("Hf) become more negative with decreasing thickness of the water layer between the hydrophobic surfaces and decreasing temperature. |"Hf | > |T"Sf| represents a necessary condition for the excess free energy change ("Gf ) to be negative and the hydrophobic interaction to be attractive. Thus, the results obtained with both the silylated and C18TACl-adosrbed silica surfaces in the present work and the thiolated gold suefaces reported before show hydrophobic forces originate from structural changes in the medium. Thermodynamic analysis of SFA force measurements obtained at various temperatures revealed that "Sf were much more negative in the shorter hydrophobic force ranges than in the longer ranges, indicating a more significant degree of structuring in the water film when the two hydrophobic surfaces are closer together. It is believed that the water molecules in the thin liquid films (TLFs) of water form clusters as a means to reduce their free energy when they cannot form H-bonds to neighboring hydrophobic surfaces. Dissolved gas molecules should enhance the stability of structured cluster due to the van der Waals force between the entrapped gas molecules and the surrounding water molecules1, which may enhance the strength of the hydrophobic force. Weaker long-range attractive forces detected in degassed water than in air-equilibrated water was found in the present work by means of AFM force measurements, supporting the effect of dissolved gas on the structuring of water. At last, temperature effects on hydrophobic interactions measured in ethanol and the thermodynamic analysis revealed similar results as those found in water, indicating that the hydrophobic force originates from H-bond propagated structuring in the mediums. •
Ph. D.
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Kowarik, Stefan M. "Real-time studies of thin film growth of organic semiconductors." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437357.
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Cole, Alexander Alan. "Studies of spin dependent transport in magnetic thin film heterostructures." Thesis, University of Leeds, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414159.
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Rocha, Luciana Sarabando da. "Thin mercury film electrodes in dynamic speciation studies of metals." Doctoral thesis, Universidade de Aveiro, 2009. http://hdl.handle.net/10773/3083.
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Doutoramento em QuímicaNo presente trabalho, foi avaliado o desempenho e a aplicabilidade do eléctrodo de filme fino de mercúrio, em estudos de especiação dinâmica de metais vestigiais. Para tal, foram utilizadas duas técnicas electroanalíticas de redissolução: a clássica Voltametria de Redissolução Anódica (ASV) e a recentemente desenvolvida, Cronopotenciometria de Redissolução com varrimento do potencial de deposição (SSCP). As propriedades de troca-iónica e de transporte de massa de películas mistas preparadas a partir de dois polímeros com características distintas, o Nafion (NA) e o 4-Poliestireno sulfonato de sódio (PSS), foram avaliadas, antes da sua aplicação no âmbito da especiação de metais. Estas películas de NA-PSS demonstraram uma elevada sensibilidade, reprodutibilidade, estabilidade mecânica, bem como, propriedades de anti-bloqueio adequadas na modificação química do eléctrodo de filme fino de mercúrio (TMFE) e, na sua aplicação na determinação de catiões metálicos vestigiais em amostras complexas, por ASV. Para além disso, o desempenho de membranas do polielectrólito PSS em estudos de voltametria de troca-iónica (IEV) foi estudado. O objectivo desta investigação foi reunir as condições ideais na preparação de películas de PSS estáveis e com uma densidade de carga negativa elevada, de modo a aumentar a acumulação electrostática de catiões metálicos no filme polimérico e por conseguinte, conseguir incrementos no sinal voltamétrico. O desempenho e aplicabilidade do TMFE em estudos de especiação de metais vestigiais foram extendidos à SSCP como técnica analítica. Dada a elevada sensibilidade e resolução evidenciada pelo TMFE, este revelou ser uma alternativa adequada aos eléctrodos de mercúrio convencionais, podendo ser utilizado durante um dia de trabalho, sem degradação aparente do sinal analítico de SCP. As curvas de SSCP obtidas experimentalmente utilizando o TMFE estavam em concordância com aquelas previstas pela teoria. Para além disso, a constante de estabilidade (K) calculada a partir do desvio do potencial de meia-onda, para dois sistemas metal-complexo lábeis, aproxima-se não só do valor teórico, como também daquele obtido utilizando o eléctrodo de mercúrio de gota suspensa (HMDE). Adicionalmente, o critério experimental de labilidade inerente a esta técnica foi validado e o grau de labilidade para um dado sistema metal-complexo foi determinado, utilizando o filme fino de mercúrio depositado sob um eléctrodo rotativo (TMF-RDE). Este eléctrodo é muito útil na determinação de parâmetros cinéticos, como é o caso da constante de velocidade de associação (ka), uma vez que as condições hidrodinâmicas, durante a etapa de deposição, se encontram bem definidas.
In the present work the performance and applicability of the thin mercury film electrode (TMFE) in the dynamic speciation of trace metals was investigated. Two different electroanalytical stripping techniques were used: the classical anodic stripping voltammetry (ASV) and a recent developed technique, scanning stripping chronopotentiometry (SSCP). The ion-exchange and the mass transport features of novel mixed coatings of two sulfonated cation-exchange polymers with dissimilar characteristics, Nafion (NA) and poly(sodium 4-styrenesulfonate) (PSS) were evaluated, prior to its application in the field of trace metal analysis. Suitable NA-PSS polymer coatings could be used in the modification of TMFE, presenting a high sensitivity, reproducibility, mechanical stability and adequate antifouling properties in the ASV determination of trace metal cations in complex media. Also the features of the PSS polyelectrolyte layers for ion-exchange voltammetry (IEV) were evaluated. The goal was to search for the best conditions to obtain stable PSS coated electrodes, which could present high negative charge densities in order to enhance the electrostatic accumulation of cations within the film, thus enlarging the ASV signal. The applicability and performance of the TMFE in the trace metal speciation studies, by SSCP, were for the first time exploited. The optimized TMFE presented a high sensitivity and resolution, being an excellent complement to the conventional mercury electrodes and could be use for 1-day term with no significant variation in the SCP analytical signal and no apparent degradation. The calculated SSCP curves were in excellent agreement with experimental data at the TMFE and the stability constant (K), calculated from the shift in the SSCP half-wave potential, of two labile metal-complex systems were in good agreement with the ones obtained using the conventional Hanging mercury drop electrode (HMDE) and those predicted by theory . Additionally, the experimental lability diagnosis inherent to the SSCP technique was validated and a rigorous quantification of the lability degree was made. Due to the well defined hydrodynamic conditions at the thin mercury film rotating disk electrode (TMF-RDE), during the deposition step, this electrode is quite valuable in the determination of kinetic parameters, like the association rate constants (ka).
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Hu, Yanhong. "Molecular dynamics studies of thin film nucleation and substrate modification." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0000955.
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Hudson, John Matthew. "Specular and diffuse X-ray scattering studies of surfaces and interfaces." Thesis, Durham University, 1994. http://etheses.dur.ac.uk/5516/.
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The behaviour of thin film semiconducting and magnetic devices depends upon the chemical and physical status of the as-grown structure. Since the dimensions of many devices can be in the Angstrom and nanometre region, characterisation techniques capable of measuring chemical and physical parameters in this regime are necessary if an understanding of the effect of specimen structure on observed properties is to be achieved. This thesis uses high resolution x-ray scattering techniques to characterise sub-micron layered structures of semiconducting and magnetic materials. Double crystal diffraction is routinely employed in the semiconductor industry for the on line inspection of sample quality. While material parameters such as sample perfection and layer composition may be rapidly deduced, the non-destructive measurement of layer thickness is more difficult (particularly for multilayered samples) and lengthy simulation procedures are often necessary to extract the thickness information from a double crystal diffraction profile. However, for semiconductor structures which act as Bragg case interferometers, oscillations (known as thickness fringes) appear in the diffracted profile. The period of these fringes can be directly related to layer thickness. Attempts to Fourier transform diffraction data, in order to automatically extract the frequency" of thickness fringes, have previously been only partially successful. It is shown that the relatively weak intensity of the thickness fringes and the presence of the substrate peak in the analysed diffraction data, drastically reduce the quality of the subsequent Fourier transform. A procedure for the manipulation of diffraction data is suggested, where an "average” envelope is fitted to the thickness fringes and used to normalise the data. The application of an auto-correlation is shown to further increase the quality of the Fourier transform of the normalised data. The application of Fourier transform techniques to the routine analysis of double crystal diffraction data is discussedA novel technique for the measurement of absolute lattice parameters of single crystals is presented, which is capable of determining lattice constants with an absolute accuracy of around 2 parts in 10(^5). The technique requires only the use of a conventional triple crystal diffractometer with motorised 20 circle movement and the provision for a fine, precise rocking motion of the analyser. To demonstrate the technique, exemplary measurements on GaAs and InAs crystals are presented. Triple crystal diffi-action analysis has been performed on three material systems of current technological interest; the Hg(_1-x)Mn(_x)Te on GaAs, the Cd(_1-x)Hg(_x)Te on CdTe/Cd(_1-x)Zn(_x)Te and the low temperature grown GaAs systems. Studies on the Hg(_1-x)Mn(_x)Te on GaAs system reveal that the principal contribution to the rocking curve widths of layers grown using the direct alloy growth (DAG) method, arise from the tilt (i.e., mosaicity) of layer sub-grains. This finding is confirmed by double crystal topography which shows that the layers are highly mosaic with a typical grain size of (130±5)µm. Topographic studies of Hg(_1-x)Mn(_x)Te on GaAs, grown using the interdiffused multilayer process (IMP), show that sample quality is significantly improved with single crystal material being produced using this growth method. Triple crystal diffraction studies of the Cd(_1-x)Hg(_x)Te on CdTe/Cd(_0.96)Zn(_0.04)Te systems reveal several findings. These are that the main contribution to rocking curve widths is from lattice tilts and that the tilt distribution increases as the layer thickness decreases. Further, the quality of the Cd(_0.96)Zn(_0.04)Te substrate analysed is superior to that of the CdTe and that Cd(_1-x)Hg(_x)Te layers grown on Cd(_0.96)Zn(_0.04)Te substrates are generally of a higher quality than those grown on CdTe. Triple crystal analysis of MBE and ALE grown GaAs films, deposited at low growth temperatures, show that, at equivalent temperatures, superior quality films are grown by the ALE technique. Narrow lattice dilation and tilt distributions are reported for GaAs films grown at temperatures as low as 300ºC by the ALE method. While diffraction techniques are highly suitable for the study of relatively perfect crystalline material, they are not appropriate to the analysis of heavily dislocated or even amorphous specimens. This is not the case for the Grazing Incidence X-Ray Reflectivity (GIXR) technique, whose sensitivity is not dependent upon sample structure. The GIXR technique is currently attracting increasing interest following the development of commercial instruments. In this thesis, GIXR has been used to probe the layer thickness and interfacial roughness of a series of magnetic multilayer samples and Si/Si(_x)Ge(_1-x) superlattices. The technique is shown to be capable of measuring layer thickness to an accuracy of one monolayer. Modelling of specular GIXR data for the Si/Si(_x)Ge(_1-x) superlattices has shown that the magnitude of interfacial roughness is different for the two types of interface within the high Ge content superlattice samples, the Si(_x)Ge(_1-x)→Si interface possessing a long range sinusoidal roughness of (0.9±0.3)nm, in addition to die short range roughness of (0.5±0.2)nm present at all interfaces. By collecting the diffuse scatter from a GIXR experiment, conformal, or correlated, roughness has been observed in both the multilayer and superlattice samples.
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Harwood, N. M. "A neutron reflectivity study of thin films." Thesis, University of Reading, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378329.
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Gold, Jeffrey Stephen. "Characterization of a novel methyl radical source and related thin film growth studies." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1787.
Full textAbstract:
Thesis (Ph. D.)--West Virginia University, 2000.Title from document title page. Document formatted into pages; contains xi, 108 p. : ill. (some col.) + appendix; 37 p. : ill. Includes abstract. Includes bibliographical references (p. 103-108; p. A-37).
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Jarlöv, Asker. "Corrosion studies on multicomponent TiZrNbTa thin films." Thesis, Uppsala universitet, Strukturkemi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-427555.
Full textAbstract:
The goal of this work was to evaluate the electrochemical properties of TiZrNbTa thin films deposited by magnetron sputtering using an industrial physical vapor deposition system. Samples were deposited on both Si(001) and 316L stainless steel. The samples deposited on Si(001) were either crystalline (bcc reflections) or amorphous, depending on the sputtering parameters. The crystalline films were composed of thin films with two different layers. The upper layer was nanocolumnar composed of elongated nanocolumns, while the lower was dense. The amorphous films had only one nanocolumnar layer and higher porosity. Polarization curves revealed that all samples had low corrosion current densities, in the order of 10-8 A/cm2. The samples showed an extended passive region up to 3.0 V vs Ag/AgCl due to the growth of a passivating oxide. The surface of the samples consisted of Nb2O5, ZrO2, TiO2 and Ta2O5. The chronoamperometry tests showed current oscillations, related to a break-down and reformation of the passive film. Electrochemical impedance spectroscopy revealed that all samples behaved similarly in all three electrolytes, and the simulated electrical circuits were indicating no corrosion reactions. A decrease in capacitance values after polarization was observed and was related to the formed surface oxide. Samples deposited on 316L stainless steel showed a passive regime for a shorter potential window, probably related to surface defects of the films. Heat treatments at 400 and 800 Celsius for 20 hours could not trigger the phase transformation from single bcc to hcp or dual bcc, as predicted by the Thermo-Calc software.
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Natsume, Yutaka. "Studies on Structures and Electronic Properties of Organic Thin Film Transistors." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/85402.
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Sinha, Nipun. "Design, fabrication, packaging and testing of thin film thermocouples for boiling studies." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1824.
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Min, Byoung Koun. "Scanning tunneling microscopic studies of SiO2 thin film supported metal nano-clusters." Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/2737.
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This dissertation is focused on understanding heterogeneous metal catalysts supported on oxides using a model catalyst system of SiO2 thin film supported metal nano-clusters. The primary technique applied to this study is scanning tunneling microscopy (STM). The most important constituent of this model catalyst system is the SiO2 thin film, as it must be thin and homogeneous enough to apply electron or ion based surface science techniques as well as STM. Ultra-thin SiO2 films were successfully synthesized on a Mo(112) single crystal. The electronic and geometric structure of the SiO2 thin film was investigated by STM combined with LEED, Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS). The relationship between defects on the SiO2 thin film and the nucleation and growth of metal nano-clusters was also investigated. By monitoring morphology changes during thermal annealing, it was found that the metal-support interaction is strongly dependent on the type of metal as well as on the defect density of the SiO2 thin film. Especially, it was found that oxygen vacancies and Si impurities play an important role in the formation of Pd-silicide. By substituting Ti atoms into the SiO2 thin film network, an atomically mixed TiO2-SiO2 thin film was synthesized. Furthermore, these Ti atoms play a role as heterogeneous defects, resulting in the creation of nucleation sites for Au nano-clusters. A marked increase in Au cluster density due to Ti defects was observed in STM. A TiO2-SiO2 thin film consisting of atomic Ti as well as TiOx islands was also synthesized by using higher amounts of Ti (17 %). More importantly, this oxide surface was found to have sinter resistant properties for Au nano-clusters, which are desirable in order to make highly active Au nano-clusters more stable under reaction conditions.
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Banks, Daniel John. "Modelling studies on peripheral nerve neural signal transduction using thin-film microelectrodes." Thesis, University of Surrey, 1994. http://epubs.surrey.ac.uk/842690/.
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Functional electrical stimulation (FES) techniques may be used to restore motor function lost or impaired through spinal cord injury. In order to use these techniques to restore complex tasks such as walking, it is necessary to provide sensory feedback to regulate the output of the FES controller. It has been suggested that multi-microelectrode probes (microprobes) implanted into the peripheral nervous system can be used to detect signals originating from the body's own sensors. These signals could be decoded and used to regulate the output of the FES controller. Prior to the present work, however, microprobes had primary been used to study neural activity in the brain, not peripheral nerves. In the present work, locust peripheral nerve has been used as an animal model for experimental and computer modelling work. The experimental work was directed at discerning the detail of information that can be obtained using microprobes to record from peripheral nerves (ie, the selectivity of the probes). In the computer modelling work, the effects of filtering the recorded signal were studied using an electrical circuit simulator programme (SPICE). Finite element analysis software (ANSYS) was used to model the electrical potential distribution in the nerve trunk, and to determine the effects of the probe substrate on the recorded signal. The results of the experimental work indicated that it may be possible to achieve higher selectivity in recording with microprobes than predicted by some models. It is concluded that future models need to represent the situation in greater detail in order to make more realistic predictions regarding the practical work. This will require further data on the electrical properties of the structures modelled within the nerve trunk. The SPICE modelling work successfully predicted the shape of the neural signals that would be recorded in the practical work. The partial differentiating effect of high pass filtering neural signals was also demonstrated. The results of the finite element modelling work demonstrated that the probe substrate would be expected to amplify signals from fibres directly in front of it, and attenuate signals from fibres behind it. This was shown to be significant for probe substrates with dimensions much smaller than the longitudinal spread of the action potential along the fibre. It was also found that these effects can be influenced by the position of the microprobe substrate relative to other structures within the nerve trunk; not just relative to the fibre. The significance of these results as they relate to mammalian nerve is discussed. Improved experimentation techniques and models are outlined, based on the results of this work. These include the requirement for improved facilities to determine the limits of selectivity in recording from peripheral nerves, and also the inclusion of inhomogeneities in models of the nerve trunk to make more realistic predictions regarding practical work. Finally, the development of active probes is discussed, including requirements for particularly novel circuitry, and the integration of many devices into a system to control FES.
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Simchi, Hamed. "Back surface studies of Cu(In,Ga)Se2 thin film solar cells." Thesis, University of Delaware, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3642359.
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Cu(In,Ga)Se2 thin film solar cells have attracted a lot of interest because they have shown the highest achieved efficiency (21%) among thin film photovoltaic materials, long-term stability, and straightforward optical bandgap engineering by changing relative amounts of present elements in the alloy. Still, there are several opportunities to further improve the performance of the Cu(In,Ga)Se2 devices. The interfaces between layers significantly affect the device performance, and knowledge of their chemical and electronic structures is essential in identifying performance limiting factors. The main goal of this research is to understand the characteristics of the Cu(In,Ga)Se2-back contact interface in order to design ohmic back contacts for Cu(In,Ga)Se2-based solar cells with a range of band gaps and device configurations. The focus is on developing either an opaque or transparent ohmic back contact via surface modification or introduction of buffer layers in the back surface.
In this project, candidate back contact materials have been identified based on modeling of band alignments and surface chemical properties of the absorber layer and back contact. For the first time, MoO3 and WO 3 transparent back contacts were successfully developed for Cu(In,Ga)Se 2 solar cells. The structural, optical, and surface properties of MoO 3 and WO3 were optimized by controlling the oxygen partial pressure during reactive sputtering and post-deposition annealing. Valence band edge energies were also obtained by analysis of the XPS spectra and used to characterize the interface band offsets.
As a result, it became possible to illuminate of the device from the back, resulting in a recently developed "backwall superstrate" device structure that outperforms conventional substrate Cu(In,Ga)Se2 devices in the absorber thickness range 0.1-0.5 µm. Further enhancements were achieved by introducing moderate amounts of Ag into the Cu(In,Ga)Se2 lattice during the co-evaporation method resulting in a 9.7% cell (with 0.3 µm thickness) which has the highest efficiency reported for ultrathin CIGS solar cells to date.
In addition, sulfized back contacts including ITO-S and MoS 2 are compared. Interface properties of different contact layers with (Ag,Cu)(In,Ga)Se2 absorber layers with various Ga/(Ga+In) and Ag/(Ag+Cu) ratios are discussed based on the XPS analysis and thermodynamics of reactions.
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Dufton, Jesse T. R. "Computational studies of sulphide-based semiconductor materials for inorganic thin-film photovoltaics." Thesis, University of Bath, 2013. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607142.
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New thin-film solar cell materials and a greater understanding of their properties are needed to meet the urgent demand for sustainable, lower-cost and scalable photovoltaics. Computational techniques have been used to investigate Cu2ZnSnS4, CuSbS2 and CuBiS2 , which are potential absorber layer materials in thin-film photovoltaics. Their low cost, low toxicity and their constituent’s relative abundance make them suitable replacements for current thin-film absorbers, which are CdTe or Cu(In, Ga)(S, Se)2 based systems. Firstly, we have used hybrid Density Functional Theory (DFT) calculations to study CuSbS2 and CuBiS2. We calculate band gaps of 1.69 eV and 1.55 eV respectively, placing CuBiS2 within the optimal range for a viable absorber material. The density of states for both these materials indicate that formation of electron hole charge carriers will occur in the Cu d10 band. Consequently, photoexcitation leads to the oxidation of Cu(I). Secondly, we have derived interatomic potentials which describe the complex structure of Cu2ZnSnS4 accurately. We find that the Cu/Zn antisite defect represents the lowest energy form of intrinsic defect disorder. For these antisite defects, we find a preference for small neutral defect clusters, which suggests a degree of self-passivation exists. Investigations of Cu-ion transport find VCu migration is possible via a vacancy hopping mechanism. There are pathways which can be connected to give 3D long-range diffusion. Investigations of the Cu/Zn site disorder in Cu2ZnSnS4 find that configurations which are kesterite-like will dominate synthetic samples. However, perfectly ordered kesterite will not be formed due to entropic effects. The simulations indicate the stannite and stannite-like polymorphs are less favourable, and can only account for ≈2.5% of a sample. Investigations of the surfaces of Cu2ZnSnS4, suggest that the vast majority of the low index surfaces are dipolar and that only the (1 1 2), (0 1 0) and (1 0 1) surfaces have low surface energies.
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Bediako, Daniel Kwabena. "Structural and mechanistic studies of nickel-borate thin-film oxygen evolving electrocatalysts." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79266.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references.
Increases in global energy demand and rising levels of atmospheric carbon dioxide demand renewable alternatives to fossil fuels as the primary energy sources of the 21st century. Solar energy is by far the most abundant renewable energy resource, yet its widespread use has been hampered by a lack of suitable methods to store energy from sunlight in a cheap and efficient manner. Solar driven water splitting is a promising method of storing solar energy, but a critical bottleneck in developing efficient photoelectrochemical (PEC) water splitting systems lies in the kinetic sluggishness of the water splitting reactions, particularly the oxygen evolution reaction (OER). In this thesis the structural and mechanistic underpinnings for the activity of a promising nickel-based oxygen evolving catalyst (OEC) are discussed. The catalyst is particularly attractive as a result of the simplicity of its preparation as a thin film from aqueous borate-buffered solutions of Ni₂ . Electrochemical and in situ X-ray absorption near-edge structure (XANES) studies of this nickel-borate (Ni-Bi) catalyst indicate that upon initial electrodeposition, Ni centers in the film exist predominantly in the +3 oxidation state and the as-deposited material is largely inactive towards the OER. Catalytic activation is achieved by anodization of the as-deposited material in concentrated borate buffer, pH 9.2, a process which serves to oxidize the nickel centers to a mixed-valence Ni(II/IV) state. Extended X-ray absorption fine structure (EXAFS) spectroscopy studies indicate that Ni-Bi is comprised of nanometer-sized clusters of edge sharing NiO₆ octahedra. A structural transformation is observed during anodization that is akin to that observed in the [beta]-NiOOH-[gamma]-NiOOH transformation, challenging the long-held view that the phase that is the most catalytically active towards the OER is the all-Ni(III) [rho]-NiOOH. Electrokinetic studies indicate that the as-deposited Ni-Bi exhibits a Tafel slope close to 2.3 x 2RT/F, consistent with a turnover-limiting electron transfer (ET) from the geometrically distorted low-spin d⁷ Ni(III) state. Upon anodization to the mixed valence Ni(III/IV) state and elimination of geometric distortion, ET from the resting state becomes more facile resulting in a low Tafel slope of 2.3 x RT/2F, indicative of a rapid two-electron pre-equilibrium followed by a rate limiting chemical step, likely O₂ formation. Anodized Ni-Bi also exhibits an inverse third order dependence in proton activity and inverse first order dependence in borate anion. This kinetically-relevant two-electron, three-proton proton-coupled electron transfer (PCET) equilibrium prior to rate limiting O₂ formation forms the mechanistic basis for the pHdependent difference in activity between Ni-Bi and its cobalt-based analog, which contrarily mediates oxygen evolution via a kinetically-relevant one-electron, one-proton PCET transformation. The difference in catalytic O₂ evolution mechanism is a principal factor in the determination of the overall solar-to-fuels efficiency of PEC water splitting systems.
by Daniel Kwabena Bediako.
S.M.
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Yang, Neng-Jye, and 楊能傑. "Studies on polymer thin film transistor." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/73628553819444921085.
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Gokhale, Nikhil Suresh. "Studies On The Development Of Piezoelectric Thin Flm Based Impact Sensor." Thesis, 2008. http://hdl.handle.net/2005/770.
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Sensors is one of the major areas of current research. Thin film micro/nano sensors are gaining attention worldwide, as there is necessity of miniaturization. There are varieties of sensors available by utilizing different materials in bulk and thin film form for measuring parameters like temperature, pressure, flow, humidity etc. Apart from these, there are various sensors available to measure impact force.
Impact sensor offers potential application possibilities in robotics, aerospace, structural & mechanical engineering and related areas. Many physical principles have been explored for the realization of impact sensor. The present thesis reports the efforts made in developing impact sensor using piezoelectric thin film. The necessary brief background information on impact sensors is presented in Chapter 1. This includes the description of available literature on impact sensors and their probable applications. In Chapter 2, a review of the various techniques such as thin film deposition techniques, film thickness measurement techniques, thin film characterization techniques, used in our work are explained in detail. Chapter 3 explains the direct and indirect methods of characterization used for confirming the piezoelectric property of zinc oxide thin films. The detailed experimental work carried out in realizing the impact sensor using piezoelectric thin films is presented in chapter 4. This includes design of the sensor, calibration setup used & the procedure followed and results obtained.
Finally, we present the summary of the work carried out in the thesis, conclusions arrived at and the scope for carrying out further work in the direction of making the sensor more efficient.
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Lin, Jyu-Wun, and 林鉅文. "Studies of thin-film structural and electrical properties of F16CuPc-based thin-film transistors." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/17261671400125234664.
Full textAbstract:
碩士國立成功大學
光電科學與工程研究所
96
In this study, the structural and electrical transport properties of n-type copper hexadecafluorophthalocyanine (F16CuPc) thin-films as an active layer were investigated using organic thin films transistors (OTFTs). In part 1, we studied the influence of substrate temperature during thin-film growth of F16CuPc on the electrical characteristics and hysteresis effects in OTFTs using indium-tin-oxide (ITO) bottom contact and bottom gate device configuration. In part 2, we studied the effects of polymeric modification layers on the F16CuPc film growth and structural properties. In part 1, we have fabricated OTFTs using the F16CuPc films which were thermally evaporated on different temperature SiO2 surfaces ranging from 30 to 180 ℃. The device characteristics were analyzed using the standard charge-sheet MOSFET model equation. These F16CuPc films were characterized by X-ray diffraction (XRD), absorption spectroscopy, and Raman spectroscopy. When the substrate temperature was set to 120 ℃, the corresponding F16CuPc-based OTFTs exhibit the highest field-effect mobility, the largest modulated on/off current ratio, the lowest subthreshold swing, and the smaller hysteresis loops. XRD and absorption spectra results could not give a reasonable explanation of the devices’ performance of F16CuPc-based OTFTs. In contrast, Raman analysis results indicated F16CuPc grown on 120 ℃ substrate has a more homogeneous molecular structure and microstructure associated with lower reorganization, thus device performance. In part 2, the structural properties of F16CuPc films grown on various polymeric modification layers were investigated using contact angle meter, XRD, absorption spectroscopy, and Raman spectroscopy. Upon analyzing the surface free energy and interfacial adhesive force between F16CuPc and polymeric surfaces, we suggest that polymethylmethacrylate (PMMA) and polystyrene (PS) are the effective modification layers for the growth of F16CuPc film. The thin film structures of F16CuPc on polymeric modification layers, e.g. PMMA, PS, and poly(vinyl alcohol) are better than that on native SiO2 surfaces.
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Yang, Chao-Shun, and 楊朝舜. "Studies of Indium Oxide Thin Film Transistors." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/03240568000849623861.
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碩士國立臺灣大學
電子工程學研究所
96
Recently, oxide semiconductors have gained much attention in the academia and the industry. Oxide semiconductors usually are of transparency owing to their wide band-gap characteristics and can be used in transparent electronics. Applications concerned have been developed in the market gradually. In addition, oxidesemiconductor-based thin film transistors can be fabricated on flexible substrates. Its flexibility can be used in a lot of novel consumer electronics and displays like LC displays、OLED displays and e-Paper etc. Oxide semiconductors have special electronic configuration of (n-1)d10ns0 (n≧4).Because of the symmetric s orbital, oxide semiconductor can attain high mobility in both crystalline and amorphous structures. Actually, oxide semiconductor thin films can be grown with good quality on a wide variety of substrates at low temperatures. In this thesis, the oxide semiconductor material studied is indium oxide. Indium oxide is used as the active material of TFTs in this thesis. In general, indium oxide thin films are very conductive, and thus many laboratories over the world have much difficulty in making indium oxide TFTs with low enough off currents and proper on/off current ratios. In the thesis, unique method is introduced to reduce the off currents dramatically. By using the unique method, the on/off ratios of our indium oxide TFTs are over 1000 times higher than results of other groups.
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Yeh, Barry B. L., and 葉柏良. "Studies of ZnO Transparent Thin Film Transistors." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/49118233620143268790.
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碩士國立暨南國際大學
電機工程學系
95
In this thesis, the transparent thin-film-transistor with ZnO thin films was fabricated. To deposit ZnO film, RF-magnetron sputtering was used with the different Ar:O2 gas flow, power, and working pressure. Then, the sample was annealing with different temperature. The material and electrical characterizations were performed by four-point-probe measurement, Hall-effect measurement, XRD analysis, spectrophotometer, and HP4156 semiconductor parameter analysis. The ZnO thin film depositied with the O2(0.5%) flow ratio exhibits the optimum (0002) orientation. The resistivity of ZnO thin film is around ~10-3 Ω-cm and the Hall measurements indicates that the carrier concentration of ZnO film was between 1020~1021cm-3, and the corresponding electron mobility was about 1.0~1.5 cm2/Vs, respectively. The device shows an average transmission (λ=400~700nm) of 81.3%, the saturation mobility μsat=1.0~1.5cm2/Vs, on-off ratio ~106, and the leakage current around 10-10A. The transparent thin film transistors can be suitable for the future flat panel display applications.
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Liang, Xin-Wei, and 梁信偉. "Studies of surface morphology and thin-film polymorphs in pentacene film." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/34460032672636841401.
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碩士國立成功大學
光電科學與工程研究所
95
In this study, device characteristics of polycrystalline pentacene-based organic thin-film transistors (OTFTs) were investigated. In part 1, we studied the traps and fixed charges at the interface between gate dielectric and pentacene by using an external magnetic field during device operations. In the second part, we studied the correlation between surface morphology and molecular vibrational characterizations of polycrystalline pentacene thin-films. Part 1: External magnetic field effects in pentacene-based organic thin-film transistors (OTFTs) during device operations were studied. Herein, we showed that the output drain current (IDS), field-effect mobility, and threshold voltage (Vth) of pentacene devices were affected by the presence of a magnetic field. The upward magnetic force made the holes drift away from the pentacene/dielectric interface and/or detrapping from the immobile states, contributing to a larger IDS and a positive shift in Vth and thus, carrier mobility. The magnetic field-induced variations in electrical characteristics of pentacene-based OTFTs were different from that of gate-induced and light-induced bias-stress effects, suggesting that extra carriers from unintentional doping may play an important role in organic TFTs’ electrical characteristics. Part 2: We studied the molecular vibrational characterizations of pentacene molecules in polycrystalline films with grain morphology using atomic force microscopy and Raman mapping measurements. We applied the micro-Raman spectroscopy to identify the molecular microstructures within the polycrystalline pentacene films, including C-H in-plane bending and C-C aromatic stretching modes in the energy range of 1140-1200 and 1300-1400 cm-1, respectively. We observed that the grain had stronger Raman intensities for all bands in the grain boundaries. At the same time, the relative intensity of 1155 (v1) and 1158 (v0) cm-1 bands was higher in those associated with a larger v0-v1 splitting in the grains than those in the grain boundaries. For polycrystalline films, the microstructures were more ordered (crystalline) in the grain and more disordered (amorphous) in the grain boundary. Consequently, we deduced that the relative intensity of v1 band and the v0-v1 splitting was proportional to the fraction of the ordered area or density of the well-defined crystal unit cell.
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陳宏裕. "Studies on the electrodeposition of CuInSe2 thin film." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/90071975872783476109.
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碩士國立高雄師範大學
化學系
90
CuInSe2 is one of the emerging materials for solar cell applications,and has received considerable attention in recent years.CIS-based solar cells showing conversion efficiencies of the order of 15% had been reported.They exhibit lone term stability without any signs of degradation.Of the techniques that have been used to fabricated thin films of material including,for example,spray, prolysis, sputtering , vacumn evaporation, selenization of metallic films and electrodeposition. Electrodeposition is of particular interest in offering the greatest potential in terms of low costs and inexpensive deposition system. In our experiment,CIS films were analyzed from chloride electrolyte by cyclic voltammetry.We focus on different stoichiometry of one ion and two different ions in deposition process.In addition,we study pH value, triethanolamine addition and different deposition potentials related to reduction current and oxidation current.Cyclic Voltammograms have been obtained to understand the structure of CIS film. The stoichiometric composition of deposited material is characterized by energy dispersive spectrometer studies.
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Yeh, G.-J., and 葉光兆. "Studies of the coercivity spin valve thin film." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/12312531141982483705.
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Huang, Wung-Ui, and 黃文鈺. "Studies of Fabricating a-Si:H Thin-Film Transistors." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/91171639480293114701.
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碩士國立中央大學
電機工程學系
86
In this study, the matrix of a-Si:H (thin-film transistors) were fabricatedon a 5 cm x 5 cm Corning 7059 glass substrate. The TFT matrix had 120 x 60 pixels and was made by using four levels of mask. To study the fabrication processes of TFTs, three topics were focused :(1) the light-penetrable TFT, (2)the light-reflective TFT, and (3) the Al-alloy gate materials in TFT. Since thedesigned mask defined source and drain pattern of TFT at the same level, so, the source and drain electrodes had the same conductive material. The light-penetrable TFT﹁ould have a transparent electrode material on source and drain regions. The transparent conductive ITO (indium-tin-oxide) waschosen as the electrode material. But, it had a poor ohmic contact to n+-a:Si:Hsource and drain layer. A thin Mo metal film added between the ITO and n+-aSi:H layers was emplyed to improve the ohmic contact, and hence the electrical characteristics of a TFT. The light-reflective TFT had light-reflective source and drain metal electrodes and the Al metal film was adopted in this work. Since, in the employed 4-masks TFT fabrication processes, an over-etching or under-etching ofn+-a-Si:H layer. The performances of this employed TFT were compared with thoseof a conventional TFT. Finally, several Al-alloies, such as Al-1 Nd, Al-2Nd, Al-Mo-B, Al-Cu-Ti-B, were used as the gate electrodes of TFTs and the characteristics of the obtained TFTs were compared with that of a TFT having Al gate electrode.
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Chen, Bor Yir, and 陳伯宜. "STUDIES ON HYDROGENATED AMORPHOUS SILICON THIN-FILM TRANSISTORS." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/37871854788960845465.
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呂俊億. "Optical studies of n-type InN thin film." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/m98582.
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Chen, He-Sheng, and 陳和聲. "Property Studies of TiO2-CuxOy Thin Film Diodes." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/30917657470777404203.
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碩士明志科技大學
材料工程研究所
99
Titanium dioxide in high-power process has a wide process window and better structural properties. The low-power process will not be able to get titanium dioxide structured. If the structural propertied of titanium dioxide was not good, then in this case will have a greater leakage current with this devise. The bandgap of Cu2O and Cu4O3 is about 2.25 eV and 1.7 eV in this experiment. Copper oxide and titanium dioxide will be produced diodes in a variety of conditions, the results show high-power process of titanium dioxide with Cu4O3 have best rectifying characteristics and photovoltaic effect. High-power process titanium dioxide film with Cu4O3 diode for the different test, the test results of photovoltaic efficiency show this result is about 0.15%, the conversion efficiency loss is because the low parallel resistance, and also because the relationship between the parallel resistance is too low lead sin-wave testing can’t be negative half-wave-type filter for full-wave rectifier test. At ESD test, the devise can live at 8kV electrostatic bombardment, but cause leak current lead the trigger voltage and clamping voltage properties not well.
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Kuo, Dong-Lin, and 郭東霖. "Studies of ZnO-Based Transparent Thin-Film Transistor." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/42233240051946527537.
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碩士國立成功大學
電機工程學系碩博士班
97
Abstract In this thesis, we demonstrate an all sputtering, all lithography technology process to fabricate low voltage operational, enhancement mode N-Type ZnO-TFT by using high-k material (Y2O3) as the gate oxide. The effects of different processing parameters of ZnO layer and device geometric structures to the electrical performance of device will be discussed in Chapter 4. We also did some applications of saving device area、driving OLED and fabricating TTFT array on glass substrate. Finally by improve the series resistance of TFT device, we fabricated devices had characters as field effect mobility (μFE) 6.5(cm2/V.s), ION/OFF~105, and Vth<5V. There are two parts in this thesis. In the first part, we discuss the ZnO-TFT characters when we use different sputtering parameters and structures. The thin film and devices were analyzed by XRD、AFM、SEM/EDS、C-V and I-V measurements. In the second part, by reducing the series resistance we can fabricate good performance TFT devices; finally, we fabricate a TTFT array of ZnO-TFT on glass substrate.