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Okazaki, Nobuharu. "Molecular rectification with identical metal electrodes at low temperatures." Thesis, University of Exeter, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251190.
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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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Gilchrist, James. "Nanoscale analysis of molecular photovoltaic thin film structures and interfaces." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/25023.
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Thin films of organic semiconducting materials, such as copper phthalocyanine (CuPc) and C60, can be used in photovoltaic devices. The interface between these materials is the site of exciton dissociation, and thus a key region of interest in their study. The processes that occur within these films and at interfaces are governed by the local morphology and structure. Studying these films and interfaces at high spatial resolution has previously been challenging given their soft nature and scale. Using electron transparent cross-sections prepared with a focussed ion beam (FIB), high resolution transmission electron microscopy (HRTEM) has been used to probe the local crystallography of three archetypical organic photovoltaic device structures grown on silicon and indium tin oxide (ITO). In HRTEM images lattice fringes of unprecedented clarity are observed, validating the optimised FIB method. HRTEM examination of device structure cross-sections on silicon reveals lattice fringes throughout pure films of CuPc and C60. The structure of the CuPc thin film can be correlated with bulk characterisation methods however, the observation of stacking faults demonstrates film non-uniformity. Lattice fringes in C60 films show an orientation preference with respect to the interface, which allows conclusions to be made about C60 when grown on molecular films. Mixed films show no lattice fringes. Structures grown on ITO are more complex than those on silicon, which is attributed the relatively rougher growth surface. Due to this rougher surface, the morphological changes occurring result in reduced crystallinity, a conclusion supported by bulk characterisation methods. The cross-sectional methodology has been extended to thicker films, revealing the presence of structural deviations that lie parallel to the surface. Scanning transmission electron microscopy, in combination with energy dispersive X-ray spectroscopy, high resolution quantitative compositional mapping reveals the morphology of the interface for the structures studied. This been correlated with the morphology of single CuPc film surfaces, with the conclusion that morphology of the CuPc surface remains unchanged after C60 film growth.
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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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Singh, Rajeev. "Experimental characterization of thin film thermoelectric materials and film deposition via molecular beam epitaxy /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2008. http://uclibs.org/PID/11984.
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Schünemann, Christoph. "Organic Small Molecules: Correlation between Molecular Structure, Thin Film Growth, and Solar Cell Performance." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-105169.
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Das wesentliche Ziel dieser Doktorarbeit ist es, die Zusammenhänge zwischen der Struktur von kleinen organischen Molekülen, deren Anordnung in der Dünnschicht und der Effizienz organischer Solarzellen zu beleuchten. Die Kombination der komplementären Methoden spektroskopischer Ellipsometrie (VASE) und Röntgenstreuung, vor allem der unter streifendem Einfall (GIXRD), hat sich als sehr effiient für die Strukturuntersuchungen organischer Dünnschichten erwiesen. Zusammen geben sie einen detailreichen Einblick in die intermolekulare Anordnung, die Kristallinität, die molekulare Orientierung, die optischen Konstanten n und k und die Phasenseparation von organischen Schichten. Zusätzlich wird die Topografie der organischen Dünnschicht mit Rasterkraftmikroskopie untersucht. Der erste Fokus liegt auf der Analyse des Dünnschichtwachstums von Zink-Phthalocyanin (ZnPc) Einzelschichten. Für alle untersuchten Schichtdicken (5, 10, 25, 50 nm) und Substrattemperaturen (Tsub=30°C, 60°C, 90°C) zeigt ZnPc ein kristallines Schichtwachstum mit aufrecht stehenden ZnPc Molekülen. Um effiziente organische Solarzellen herzustellen, werden Donor- und Akzeptormoleküle üblicherweise koverdampft. Bei der Mischung von Donor- und Akzeptormolekülen bildet sich eine gewisse Phasenseparation aus, deren Form wesentlich für die Ladungsträgerextraktion entlang der Perkolationpfade ist. Der Ursprung dieser Phasenseparation wird innerhalb dieser Arbeit experimentell für ZnPc:C60 Absorber-Mischschichten untersucht. Um die Ausprägung der Phasenseparation zu variieren, werden verschiedene Tsub (30°C, 100°C, 140°C) und Mischverhältnisse (6:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:6) bei der Koverdampfung von ZnPc und C60 angewendet. GIXRD Messungen zeigen, dass hier der bevorzugte Kristallisationsprozess von C60 Molekülen die treibende Kraft für eine effiziente Phasenseparation ist. Solarzellen, die ZnPc:C60 Mischschichten mit verbesserter Phasenseparation enthalten (Tsub=140°C, 1:1), zeigen eine verbesserte Ladungsträgerextraktion und somit eine höhere Effizienz von 3,0% im Vergleich zu 2,5% für die entsprechende Referenzsolarzelle (Tsub=30°C, 1:1). Im zweiten Teil der Arbeit wird der Einfluss der Molekülorientierung auf die Dünnschichtabsorption beispielhaft an ZnPc und Diindenoperylen (DIP) untersucht. DIP und ZnPc Moleküle, die auf schwach wechselwirkenden Substraten wie Glas, SiO2, amorphen organischen Transportschichten oder C60 aufgedampft sind, zeigen eine eher stehende Orientierung innerhalb der Dünnschicht in Bezug zur Substratoberfläche. Im Gegensatz dazu führt die Abscheidung auf stark wechselwirkenden Substraten, wie z.B. einer Gold- oder Silberschicht oder 0.5 nm bis 2 nm dünnen PTCDA (3,4,9,10-Perylentetracarbonsäuredianhydrid) Templatschichten laut GIXRD und VASE Messungen dazu, dass sich die ZnPc und DIP Moleküle eher flach liegend orientieren. Dies führt zu einer wesentlich besseren Dünnschichtabsorption da das molekulare Übergangsdipolmoment jeweils innerhalb der Ebene des ZnPc und des DIP Moleküls liegt. Ein Einbetten von Gold- oder Silberzwischenschichten in organischen Solarzellen führt leider zu keinen klaren Abhängigkeiten, da die verbesserte Absorption durch die flach liegenden Moleküle von Mikrokavitäts- und plasmonischen Effekten überlagert wird. Ebenso wenig führte das Einfügen einer PTCDA-Zwischenschicht in organischen Solarzellen zum Erfolg, da hier Transportbarrieren den Effekt der verbesserten Absorption überlagern. Das letzte Kapitel konzentriert sich auf den Einfluss der Molekülstruktur auf das Dünnschichtwachstum am Beispiel von DIP und dessen Derivaten Ph4-DIP und P4-Ph4-DIP, Isoviolanthron und Bis-nFl-NTCDI (N,N-Bis(fluorene-2-yl)-naphthalenetetra-carboxylic Diimid) Derivaten. GIXRD Messungen belegen deutlich, dass die sterischen Behinderungen, hervorgerufen durch die Phenylringe (für Ph4-DIP und P4-Ph4-DIP) und Seitenketten (für Bis-nFl-NTCDI), ein amorphes Schichtwachstum induzieren. Im Vergleich sind die Dünnschichten von DIP und Bis-HFl-NTCDI kristallin. Bezüglich der Molekülorientierung und folglich der Absorption von DIP und dessen Derivaten kann ein starker Einfluss des Schichtwachstums beobachtet werden. In Solarzellen verhindert die Präsenz der Phenylringe eine effiziente Phasenseparation der Mischschichten aus (P4-)Ph4-DIP:C60, was zu einer verschlechterten Ladungsträgerextraktion und damit zu einem reduzierten Füllfaktor (FF) von 52% im Vergleich zu dem entsprechender DIP:C60 Solarzellen mit FF=62% führt Die Untersuchungen an der Bis-nFl-NTICDI Serie zeigen ein ähnliches Ergebnis: Auch hier zeichnen sich die amorphen Schichten aus Bis-nFl-NTCDI Molekülen mit Seitenketten durch schlechtere Transporteigenschaften aus als nanokristalline Bis-HFl-NTCDI SchichtenThe aim of this thesis is to demonstrate correlations between the molecular structure of small organic molecules, their arrangement in thin films, and the solar cell performance. For structure analysis of the organic thin films, the combination of variable angle spectroscopic ellipsometry (VASE) and grazing incidence X-ray diffraction (GIXRD) as complementary methods turned out to be a powerful combination. Using both methods, it is possible to obtain information about the crystallinity, crystallite size, intermolecular arrangement, mean molecular orientation, optical constants n and k, and phase separation within thin films. In addition, the topography of thin films is analyzed by atomic force microscopy. First, the thin film morphology of pristine zinc-phthalocyanine (ZnPc) films deposited at different substrate temperatures (Tsub=30°C, 60°C, 90°C) and for varying film thicknesses (5, 10, 25, 50 nm) is investigated. The ZnPc films grow highly crystalline with an upright standing molecular orientation with respect to the substrate surface for all investigated Tsub and all film thicknesses. In effcient organic solar cells, donor and acceptor molecules are commonly co-deposited to form a blend absorber film. This is usually accompanied by a certain phase separation between donor and acceptor molecules leads to a formation of percolation paths necessary to extract electrons and holes towards the electrodes. For ZnPc:C60 blends the origin of this phase separation process is analyzed by investigating different degrees of phase separation induced by film deposition at different Tsub (30°C, 100°C, 140°C) and for different blend ratios (6:1, ... , 1:6 (vol%)). GIXRD measurements indicate that the preferred crystallization of C60 is the driving force for good phase separation. Solar cells with improved phase separation of ZnPc:C60 blends (Tsub=140°C, 1:1) reveal a better charge carrier extraction and thus enhanced effciencies of 3.0% in comparison to 2.5% for the reference device (Tsub=30°C, 1:1). In the second part, the impact of molecular orientation within the absorber thin films on light harvesting is examined for pristine ZnPc and diindenoperylene (DIP) films. For film deposition on weakly interacting substrates like glass, SiO2, amorphous organic transport films, or C60, the orientation of DIP and ZnPc molecules is found to be upright standing. In contrast, GIXRD and VASE measurements show that films deposited onto strongly interacting substrates like Au and Ag, as well as on thin PTCDA templating layers lead to nearly flat-lying ZnPc and DIP molecules. Since the molecular transition dipole moment is oriented in the plane of the DIP and ZnPc molecules, the light absorption in films with flat-lying molecules is strongly improved. Unfortunately, an implementation of Au or Ag sublayers in organic solar cells does not result in reliable dependencies since the enhanced absorption by an improved molecular orientation is superimposed by different effects like microcavity and plasmonic effects. The implementation of PTCDA interlayers leads to transport barriers making the solar cell data interpretation difficult. In the last part, the influence of molecular structure on thin film growth is studied for DIP and its derivatives Ph4-DIP and P4-Ph4-DIP, isoviolanthrone, and Bis-nFl-NTCDI derivatives. GIXRD measurements reveal that steric hindrance is induced by the addition of side chains (for Bis-nFl-NTCDI) and phenyl rings (for Ph4-DIP and P4-Ph4-DIP) (N,N-Bis(fluorene-2-yl)-naphthalenetetra-carboxylic diimide) leading to an amorphous thin film growth. In contrast, DIP films and Bis-HFl-NTCDI films are found to be crystalline. The mean molecular orientation and hence the absorption is strongly affected by the different growth modes of DIP and its derivatives. In OSC, the presence of the phenyl rings prevents an effcient phase separation for (P4-)Ph4-DIP:C60 blends which causes diminished charge extraction in comparison to the crystalline DIP:C60 blends. For the Bis-nFl-NTCDI series, the transport properties are significantly worse in the amorphous films composed of Bis-nFl-NTCDI derivatives with alkyl chains in comparison to the nanocrystalline films made of the bare Bis-HFl-NTCDI
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Yu, Shun. "Molecular Interaction of Thin Film Photosensitive Organic Dyes on TiO2 Surfaces." Doctoral thesis, KTH, Materialfysik, MF, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-47354.
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The photosensitive molecule adsorption on titanium dioxide (TiO2) forms the so-called “dye sensitized TiO2” system, a typical organic/oxide heterojunction, which is of great interest in catalysis and energy applications, e.g. dye-sensitized solar cell (DSSC). Traditionally, the transition metal complex dyes are the focus of the study. However, as the fast development of the organic semiconductors and invention of new pure organic dyes, it is necessary to expand the research horizon to cover these molecules and concrete the fundamental understanding of their basic properties, especially during sensitization.In this work, we focus on two different photosensitive molecules: phthalocyanines and triphenylamine-based dyes. Phthalocyanines are organic semiconductors with symmetric macro aromatic molecular structures. They possess good photoelectrical properties and good thermal and chemical stability, which make them widely used in the organic electronic industries. Triphenylamine-based dyes are new types of pure organic dyes which deliver high efficiency and reduce the cost of DSSC. They can be nominated as one of the strong candidates to substitute the ruthenium complex dyes in DSSC. The researches were carried out using classic surface science techniques on single crystal substrates and under ultrahigh vacuum condition. The photosensitive molecules were deposited by organic molecular beam deposition. The substrate reconstruction and ordering were checked by low energy electron diffraction. The molecular electronic, geometric structures and charge transfer properties were characterized by photoelectron spectroscopy, near edge X-ray absorption fine structure spectroscopy and resonant photoelectron spectroscopy (RPES). Scanning tunneling microscopy is used to directly image the molecular adsorption.For phthalocyanines, we select MgPc, ZnPc, FePc and TiOPc, which showed a general charge transfer from molecule to the substrate when adsorbed on rutile TiO2(110) surface with 1×1 and 1×2 reconstructions. This charge transfer can be prevented by modifying the TiO2 surface with pyridine derivatives (4-tert-butyl pyridine (4TBP), 2,2’-bipyridine and 4,4’-bipyridine), and furthermore the energy level alignment at the interface is modified by the surface dipole established by the pyridine molecules. Annealing also plays an important role to control the molecular structure and change the electronic structure together with the charge transfer properties, shown by TiOPc film. Special discussions were done for 4TBP for its ability to shift the substrate band bending by healing the oxygen vacancies, which makes it an important additive in the DSSC electrolyte. For the triphenylamine-based dye (TPAC), the systematic deposition enables the characterization of the coverage dependent changes of molecular electronic and geometric structures. The light polarization dependent charge transfer was revealed by RPES. Furthermore, the iodine doped TPAC on TiO2 were investigated to mimic the electrolyte/dye/TiO2 interface in the real DSSC.The whole work of this thesis aims to provide fundamental understanding of the interaction between photosensitive molecules on TiO2 surfaces at molecular level in the monolayer region, e.g. the formation of interfacial states and the coverage dependent atomic and electronic structures, etc. We explored the potential of the application of new dyes and modified of the existing system by identifying their advantage and disadvantage. The results may benefit the fields of dye syntheses, catalysis researches and designs of organic photovoltaic devices.QC 20111114
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Kim, Younggu. "Novel organic polymeric and molecular thin-film devices for photonic applications." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/4164.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Thesis research directed by: Department of Electrical and Computer Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Wu, Yu. "Control of pentacene thin film growth by supersonic molecular beam deposition." [S.l. : [Groningen : s.n.] ; University Library Groningen] [Host], 2008. http://irs.ub.rug.nl/ppn/.
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Nakamura, Tomoya. "Molecular Orientation Control of Organic Semiconducting Materials for Thin Film Electronics." Kyoto University, 2019. http://hdl.handle.net/2433/242523.
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Zugic, Richard. "Modelling the tribology of thin film interfaces." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365788.
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Singh, Lovejeet. "The influence of film thickness and molecular weight on the thermal properties of ultrathin polymer films." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/11043.
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Kadhim, N. J. "Morphological imperfections associated with molecular beam epitaxial growth of GaAs layers." Thesis, University of Hertfordshire, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377702.
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Lloyd, Adam L. "Modelling silver thin film growth on zinc oxide." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/24860.
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Ag thin film growth on ZnO substrates has been investigated theoretically using multi-timescale simulation methods. The models are based on an atomistic approach where the interactions between atoms are treated classically using a mixture of fixed and variable charge potential energy functions. After some preliminary tests it was found that existing fixed charge potential functions were unreliable for surface growth simulations. This resulted in the development of a ReaxFF variable charge potential fitted to Ag/ZnO surface interactions. Ab initio models of simple crystal structures and surface configurations were used for potential fitting and testing. The dynamic interaction of the Ag atoms with the ZnO surface was first investigated using single point depositions, via molecular dynamics, whereby the Ag impacted various points on an irreducible symmetry zone of the ZnO surface at a range of energies. This enabled the determination of the relative numbers of atoms that could penetrate, reflect or bond to the surface as a function of incident energy. The results showed that at an energy of up to 10 eV, most atoms deposited adsorbed on top of the surface layer. The second part of the dynamic interaction involved a multi-timescale technique whereby molecular dynamics (MD) was used in the initial stages followed by an adaptive kinetic Monte Carlo (AKMC) approach to model the diffusion over the surface between impacts. An impact energy of 3 eV was chosen for this investigation. Ag was grown on various ZnO surfaces including perfect polar, O-deficient and surfaces with step edges. Initial growth suggests that Ag prefers to be spread out across a perfect surface until large clusters are forced to form. After further first layer growth, subsequent Ag atoms begin to deposit on the existing Ag clusters and are unlikely to join the first layer. Ag island formation (as mentioned within the literature) can then occur via this growth mechanism. O-deficient regions of ZnO surfaces result in unfavourable Ag adsorption sites and cause cluster formation to occur away from O-vacancies. In contrast, ZnO step edges attract deposited Ag atoms and result in the migration of surface Ag atoms to under-coordinated O atoms in the step edge. Various improvements have been made to the existing methodology in which transitions are determined. A new method for determining defects within a system, by considering the coordination number of atoms, is shown to increase the number of transitions found during single ended search methods such as the relaxation and translation (RAT) algorithm. A super-basin approach based on the mean rate method is also introduced as a method of accelerating a simulation when small energy barriers dominate. This method effectively combines states connected by small energy barriers into a single large basin and calculates the mean time to escape such basin. To accelerate growth simulations further and allow larger systems to be considered, a lattice based adaptive kinetic Monte Carlo (LatAKMC) method is developed. As off-lattice AKMC and MD results suggest Ag resides in highly symmetric adsorption sites and that low energy deposition events lead to no penetrating Ag atoms or surface deformation, the on-lattice based approach is used to grow Ag on larger perfect polar ZnO surfaces. Results from the LatAKMC approach agree with off-lattice AKMC findings and predict Ag island formation. Critical island sizes of Ag on ZnO are also approximated using a mean rate approach. Single Ag atoms are placed above an existing Ag cluster and all transition states are treated as belonging to a single large super-basin . Results indicate that small Ag clusters on the perfect ZnO surface grow in the surface plane until a critical island size of around 500 atoms is reached. Once a critical island size is reached, multiple Ag ad-atoms will deposit on the island before existing Ag atoms join the cluster layer and hence islands will grow upwards. A marked difference is seen for second layer critical island sizes; second layer Ag islands are predicted to be two orders of magnitude smaller (< 7 atoms). This analysis suggests that Ag on ZnO (0001) may exhibit Stranski-Krastanov (layer plus island) growth.
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Effertz, Christian [Verfasser]. "Organic molecular crystals: from thin-films to devices : investigation of thin-film formation and electronic transport properties of polycrystalline perylene films / Christian Effertz." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2011. http://d-nb.info/1018191550/34.
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Shioya, Nobutaka. "Development of Analytical Technique of Molecular Orientation in a Thin Film and Its Application to Low-Crystallinity Organic Thin Films Having a Surface Roughness." Kyoto University, 2018. http://hdl.handle.net/2433/232268.
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Savoy, Steven Michael. "Molecular thin film/high temperature superconductor heterostructures : deposition, characterization and energy transfer /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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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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Hsu, Chih-Hao. "Hierarchical Supramolecular Structures based on Molecular Nanoparticles from Bulk to Thin Film State." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1406630381.
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Abdullah, Isam. "Nanoscale properties of molecular and oxide based thin film devices measured by SPM." Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/94080/.
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Organic and inorganic-metal oxide thin film transistors can be solution-processed, providing large area, low cost and low processing temperature leading to strong industrial and research interest. The nanoscale properties of each material system have been investigated using scanning probe techniques. Pentacene is a model small molecule organic semiconductor but it is an air sensitive material and insoluble. However, its derivative 6,13-bis(triisopropyl-silylethynyl) pentacene (TIPS-PEN) is amenable to solution processing. The motivation to study TIPSPEN is not to chase performance figures only but to investigate how the solution deposited film topography can be controlled by varying the solvent composition and the insulating polymer binder concentration. We report the effect of anisole / decane binary solvent mixture and the subsequent addition of low percentage weight of (atactic amorphous polystyrene) aPS on the surface morphology of TIPS-PEN thin films. It was found that addition of up to 20 wt% decane has little impact on micro-scale crystal morphology but has a significant influence on the growth mode, mean grain size and terrace roughness. The effect of the TIPS-PEN / aPS blend ratio up to 20 wt% of aPS in drop-cast thin film was similarly investigated on untreated SiO2 and on poly(4-vinylphenol) ( PVP) interlayers. It is found that addition of aPS has a vital effect on macroscopic crystal properties such as surface coverage, unity of orientation, long range order, and average field effect mobility. It also changes the surface morphology and layer ordering on the nano-scale. Mobility values obtained from PVP treated surface were higher than those from SiO2 surface by five times, which was consistent with preferred TIPS-PEN crystal growth on hydrophobic surface PVP of low surface energy. Indium oxide (In2O3) is an n-type (electron transport), optical transparent with wide bandgap values between 3.5 and 4 eV, and high performance semiconductor. Spin coating was used to prepare indium oxide thin film transistors (TFT) of two different thicknesses of the device channel. As the thickness of the In2O3 active layer is increased, the device mobility increases, the threshold voltage is shifted in the negative direction, off-drain current is increased, and on-drain current is less pronounced. A systematic study was carried out to investigate the transistor stability under bias stress. Applying a positive gate bias stress to indium oxide transparent TFTs was found to induce a parallel shifts of threshold voltage in positive direction without changing the device mobility or the subthreshold gate voltage swing. Scanning Kelvin Probe Microscopy (SKPM) was used to study the surface potential distribution of operating devices under a range of drain and gate biases. The potential profiles showed evidence of metal contact diffusion into the channel region which appeared as a flatting of the profile close to the drain electrode. The experimental data was confirmed and complemented with simulation results for contact material diffusion into the In2O3 channel. A new method of performing Electrostatic Force Microscopy (EFM) was developed and applied to the In2O3 TFT. The tip bias was modulated and the resulting phase difference between the cantilever response and the applied bias was recorded. The measurements were affected by a time delay, likely to be caused by capacitive charging of the semiconductor beneath the tip. The effects of the time delay were corrected by the use of an inverse filter in the analysis software developed. This new version of the EFM-phase method was applied to the operating biased In2O3 TFTs and the results compared with those obtained with SKPM.
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Borovikov, Valery V. "Multi-scale Simulations of Thin-Film Metal Epitaxial Growth." University of Toledo / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1216928358.
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Oguz, Cihan. "Control-oriented modeling of discrete configuration molecular scale processes applications in polymer synthesis and thin film growth /." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19867.
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Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2008.Committee Chair: Gallivan, Martha A.; Committee Member: Hess, Dennis; Committee Member: Lee, Jay H.; Committee Member: Li, Mo; Committee Member: Ludovice, Pete.
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Alleman, Coleman. "Molecular Dynamics Investigations of Polystyrene-Based Binary Thin Film Systems: Interfacial Properties and Mechanical Behavior." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306909005.
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Goktepe, Canan. "Water Soluble Monomer Grafting On Thin Films Of Ultra High Molecular Weight Polyethylene." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/4/1081546/index.pdf.
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This study covers grafting of Acrylic Acid (AA) and Methacrylic Acid (MAA) on Ultrahigh Molecular Weight Polyethylene (UHMWPE) thin films by surface grafting and xylene-swollen grafting methods with Co-60 γ
-ray in air. Also characterizations of pure, irradiated and grafted films were made by applying gravimetric, spectroscopic, thermal and mechanic tests. The thin films of UHMWPE were prepared by using compression molding. AA and MAA grafting on thin UHMWPE films were carried out by surface grafting and xylene-swollen grafting methods. During grafting processes, homopolymerization of monomers was avoided by using Fe2+ and Cu2+ ions. Grafting degree of AA and MAA were calculated for the samples irradiated at different doses. To verify grafting of AA and MAA on UHMWPE films, FTIR spectra of grafted films were used. Metal-uptake capacity is important property of grafted polyethylene for environmental applications. Thus, we examined metal-uptake capacities of AA and MAA grafted films for Fe(III) and Ni (II) and it was found that AA and MAA grafted UHMWPE films showed good affinity towards Fe(III) and Ni(II) metals. Thermal behavior of films were examined by DSC analysis. First run and second run DSC thermograms showed the thermal stability of films under heat. Mechanical properties of UHMWPE decrease with irradiation and grafting. However stress at break values of xylene-swollen grafted samples tend to increase with irradiation dose. In conclusion, water soluble monomers were successfully grafted on UHMWPE and these AA and MAA grafted UHMWPE films can be used in biomedical, environmental applications and other related areas.
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Mandru, Andrada Oana. "Ferromagnetic Thin and Ultra-Thin Film Alloys of Manganese and Iron with Gallium and Their Structural, Electronic, and Magnetic Properties." Ohio University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1458572741.
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Bradley, Christopher Simon. "The synthesis and characterisation of Langmuir-Blodgett film forming TCNQ adducts." Thesis, Sheffield Hallam University, 1999. http://shura.shu.ac.uk/19388/.
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Substitution reactions of TCNQ (7,7,8,8-tetracyanoquinodimethane) with suitable electron donor moieties extended the range of gamma-bridged adducts R(4)Q3CNQ and R(4)P3CNQ of which the short chain Z-beta-(l-butyl-4'-quinolinium)-alpha-cyano-4-styryldicyanomethanide (C[4]H[9](4)Q3CNQ) is a typical example. These zwitterionic D-pi-A materials (where D and A are electron donors and acceptors respectively) exhibit properties such as solvatochromism, molecular rectification and second harmonic generation. Further synthetic work concentrated on modifying the donor, the acceptor and the substitution position within these zwitterions to create a series of diverse materials for non-linear optic research. Modification of the picolinium and quinolinium systems where the TCNQ substitution is in the alpha-position, has created the extensive analogous series-R(2)Q3CNQ and R(2)P3CNQ, their properties being compared and contrasted to the original gamma-bridged adducts. The behaviour of the materials on the subphase and their resultant Langmuir-Blodgett (LB) film fabrication was studied. The abrupt change in molecular orientation in LB films of the gamma-bridged adducts occurring at R= C[15]H[31] and above was not seen in the more flatly orientated alpha-bridged adducts. Further characterisation of the LB films was performed using reflectance-absorption infrared spectroscopy (RAIRS) and surface plasmon resonance (SPR).A number of N-alkylpyridinium benzimidazolate betaine derivatives and the related betaine-TCNQ adducts were prepared and their LB film forming properties were studied.
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Wu, Zhenghao. "Investigating the Effects of Grafting and Chain Stiffness on Nanoconfined Polymers from Molecular Dynamics Simulation." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1525861929889197.
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Yu, Samuel Shing Chi. "Covalent Attachment of Nanoscale Organic Films to Carbon Surfaces." Thesis, University of Canterbury. Chemistry, 2008. http://hdl.handle.net/10092/4083.
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Modification of planar graphitic carbon surfaces by the attachment of molecular films has been investigated in this work. Molecular layers have been grafted to glassy carbon (GC) and pyrolyzed photoresist film (PPF) by employing a range of techniques, which involved electrochemically and photochemically assisted procedures. Modification methods involve the electrochemical reduction of aryldiazonium salt, electrochemical oxidation of arylcarboxylate and photolysis of alkene, alkyne and azide on carbon surfaces. For these methods, it is proposed that reactive species are generated by the procedures, which leads to the grafting of modifiers to the carbon surfaces. A selection of molecular species was grafted to GC and PPF by these method containing different terminal R-functional groups that include —COOH, -NO₂, -NH₂, and —NCS. The grafted R-functional groups permit for further chemical reactions on the surface. Electrochemically and photochemically grafted films were examined with a combination of water contact angle measurements, cyclic voltammetry, X-ray electron spectroscopy XPS, optical microscopy, scanning electron microscopy SEM and atomic force microscopy AFM. Film properties such as surface concentration, film thickness, wettability, chemical composition and reactivity were characterized by the above mentioned techniques. Films electrochemically prepared from aryldiazonium salts and arylcarboxylates, under the conditions applied in this work, formed loosely packed multilayers with typical film thicknesses of les than 5 nm. Photochemically grafted films prepared from alkenes and azides, in general, formed loosely packed monolayers with film thicknesses of less than 2 nm. Loosely packed multilayers were also prepared from alkene and alkyne by photochemical procedures. ii Chemical reactions on grafted films were demonstrated and analyzed by a combination of the above mentioned characterization techniques. In particular, the reduction of nitrophenyl (NP)films, amine-coupling reactions, photoactivation of grafted films with oxalyl chloride and electrostatic assembly of anionic gold nanoparticles were investigated. Selected chemical reactions permitted identification and evaluation of the grafted layers, and demonstrated the ability to control the immobilization of chemical species. Microscale chemical patterning of two different types of modifiers on carbon surfaces was demonstrated using photolithographical techniques that utilized photochemical reactions with azides. Patterns of line-arrays with line widths of hundreds of micrometers to 10 µm were formed.
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Heidarian, Alireza. "Study of the Static and Dynamic Magnetization across the First Order Phase Transition in FeRh Thin Films." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-198693.
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The equiatomic FeRh alloy undergoes a first-order phase transition from an antiferromagnetic (AFM) to a ferromagnetic (FM) state at about 370 K with a small thermal hysteresis of about 10 K around the phase transition. The transition is accompanied by a unit cell volume expansion about 1% in the c lattice parameter. During the transition the new phase nucleates in the matrix of the original phase by reaching the critical temperature followed by a growth in size upon increasing temperature further. Therefore, to understand the transition process with more details, it is desirable to investigate the nucleation and growth of both phases within the first order phase transition.
In the present thesis the main focus is on the growth of FeRh thin films by means of Molecular Beam Epitaxy (MBE) technique and characterization of the magnetic and structural properties. To develop an understanding of the phase transformation in FeRh thin films the ways in which one can tune it were investigated.
The following aspects concerning the FeRh system have been examined here:
1) influence of annealing temperature on the magnetic and structural response,
2) effect of film thickness on the first-order phase transition temperature as well as the saturation magnetization,
3) influence of chemical composition on the magnetic properties and
4) magnetic field-induced phase transition.
To get insight to details of the transition process the magnetization dynamic has been addressed by performing Ferromagnetic resonance (FMR) experiment across the phase transition. FMR measurements determined the existence of two areas with different magnetic properties inside the film. A huge temperature difference for the beginning of the phase transition in comparison with the static magnetization measurement was observed for the equiatomic FeRh thin film prepared by MBE.
Tuning of the AFM to FM phase transition in the FeRh thin film by means of low-energy/low fluence Ne+ ion irradiation was studied. Ion irradiation technique offers a quantitative control of the degree of chemical disorder by adjusting the ion fluence applied, while the penetration depth of the disordered phase can be adjusted by the ion-energy. The main results of ion irradiation are the shifting of the phase transition temperature to lower temperature and irradiation with 3×1014 ion/cm2 leads to the disappearance the AFM phase completely.
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Doherty, Walter John. "POLYMER-MEDIATED ELECTROCHEMISTRY IN SOL-GEL THIN FILMS AND SPECTROELECTROCHEMICAL CHARACTERIZATION OF MOLECULAR ADLAYERS ON INDIUM-TIN OXIDE ELECTRODE SURFACES." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1233%5F1%5Fm.pdf&type=application/pdf.
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Mares, Jeremy. "EPITAXIAL GROWTH, CHARACTERIZATION AND APPLICATION OF NOVEL WIDE BANDGAP OXIDE SEMICONDUCTORS." Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3002.
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In this work, a body of knowledge is presented which pertains to the growth, characterization and exploitation of high quality, novel II-IV oxide epitaxial films and structures grown by plasma-assisted molecular beam epitaxy. The two compounds of primary interest within this research are the ternary films NixMg1-xO and ZnxMg1-xO and the investigation focuses predominantly on the realization, assessment and implementation of these two oxides as optoelectronic materials. The functioning hypothesis for this largely experimental effort has been that these cubic ternary oxides can be exploited - and possibly even juxtaposed - to realize novel wide band gap optoelectronic technologies. The results of the research conducted presented herein overwhelmingly support this hypothesis in that they confirm the possibility to grow these films with sufficient quality by this technique, as conjectured. NixMg1-xO films with varying Nickel concentrations ranging from x = 0 to x = 1 have been grown on lattice matched MgO substrates (lattice mismatch ε < 0.01) and characterized structurally, morphologically, optically and electrically. Similarly, cubic ZnxMg1-xO films with Zinc concentrations ranging from x = 0 to x ≈ 0.53, as limited by phase segregation, have also been grown and characterized. Photoconductive devices have been designed and fabricated from these films and characterized. Successfully engineered films in both categories exhibit the desired deep ultraviolet photoresponse and therefore verify the hypothesis. While the culminating work of interest here focuses on the two compounds discussed above, the investigation has also involved the characterization or exploitation of related films including hexagonal phase ZnxMg1-xO, ZnO, CdxZn1-xO and hybrid structures based on these compounds used in conjunction with GaN. These works were critical precursors to the growth of cubic oxides, however, and are closely relevant. Viewed in its entirety, this document can therefore be considered a multifaceted interrogation of several novel oxide compounds and structures, both cubic and wurtzite in structure. The conclusions of the research can be stated succinctly as a quantifiably successful effort to validate the use of these compounds and structures for wide bandgap optoelectronic technologies.Ph.D.
Optics and Photonics
Optics and Photonics
Optics PhD
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Lawrence, A. J. "Modeling the Optical Response to a Near-Field Probe Tip from a Generalized Multilayer Thin Film." PDXScholar, 2015. https://pdxscholar.library.pdx.edu/open_access_etds/2328.
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The contrast mechanism in Kerr imaging is the apparent angle through which the plane of polarization is rotated upon reflection from a magnetic surface. This can be calculated for a well characterized surface given the polarization state of the incident light. As in traditional optical microscopy, the spatial resolution is limited by diffraction to roughly half the wavelength of the illumination light.
The diffraction limit can be circumvented through the use of near-field scanning optical microscopy, in which the illumination source is an evanescent field at the tip of a tapered optical fiber. A novel probe design for near-field optical imaging in reflection mode will be proposed, and experimental work on the development of a near-field Kerr microscope performed up to this point will be presented.
The complication in merging these two techniques arises from the complex polarization profile of the evanescent field. This profile can be characterized for a given probe geometry with the use of electromagnetic field modeling software, allowing for subsequent modeling of the polarization profile of the optical response. An algorithm for predicting the optical response to a near-field probe tip from a generalized multilayer thin-film is presented.
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Merchan, Alvarez Lina Paola. "Alkane fluids confined and compressed by two smooth gold crystalline surfaces: pure liquids and mixtures." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/47551.
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With the use of grand canonical molecular dynamics, we studied the slow ompression(0.01m/s) of very thin liquid films made of equimolar mixtures of short and long alkane chains (hexane and hexadecane), and branched and unbranched alkanes (phytane and hexadecane). Besides comparing how these mixtures behave under constant speed compression, we will compare their properties with the behavior and structure of
the pure systems undergoing the same type of slow compression. To understand the arrangement of the molecules inside the confinement, we present segmental and molecular density profiles, average length and orientation of the molecules inside well layered gaps. To observe the effects of the compression on the fluids, we present the number of confined molecules, the inlayer orientation, the solvation force and the inlayer diffusion coefficient, versus the thickness of the gap. We
observe that pure hexadecane, although liquid at this temperature, starts presenting strong solid-like behavior when it is compressed to thicknesses under 3nm, while pure hexane and pure phytane continue to behave liquid-like except at 1.3nm when they show some weak solid-like features. When hexadecane is mixed with the short straight hexane, it remains liquid down to 2.8nm at which point this mixture behaves solid-like with an enhanced alignment of the long molecules not seen in its pure form; but when hexadecane is mixed with the branched phytane the system does not present the solid-like features seen when hexadecane is compressed pure.
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Belova, Valentina Verfasser], and Frank [Akademischer Betreuer] [Schreiber. "Correlation between Structural Properties and Intermolecular Coupling in Molecular Donor/Acceptor Thin Film Heterostructures / Valentina Belova ; Betreuer: Frank Schreiber." Tübingen : Universitätsbibliothek Tübingen, 2018. http://d-nb.info/117067237X/34.
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Belova, Valentina [Verfasser], and Frank [Akademischer Betreuer] Schreiber. "Correlation between Structural Properties and Intermolecular Coupling in Molecular Donor/Acceptor Thin Film Heterostructures / Valentina Belova ; Betreuer: Frank Schreiber." Tübingen : Universitätsbibliothek Tübingen, 2018. http://d-nb.info/117067237X/34.
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Zykov, Anton. "On the understanding of organic thin film growth and the changes in structure formation induced by molecular chemical tuning." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2017. http://dx.doi.org/10.18452/17710.
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Funktionale organische Moleküle bergen ein hohes Potential für den Einsatz in zukunftsprägenden Technologien wie organischen Leuchtdioden (OLED), Solarzellen, Transistoren und Bio-Sensoren. Eines der Herstellungsverfahren beruht auf der Gasphasenabscheidung der Moleküle, die auf dem Substrat mittels Selbstorganisation zu dünnen Schichten wachsen. Auf Grund der komplexen Wechselwirkungen und des Einflusses der Schichtmorphologie auf die Funktionalität der dünnen Schichten stellt der Wachstumsprozess sowohl für die anwendungsorientierte als auch für die Grundlagenforschung eine hochinteressante und wichtige wissenschaftliche Herausforderung dar, mit der sich die vorliegende Arbeit auseinandersetzt. Die experimentellen Resultate und Konzepte, die in dieser Arbeit vorgestellt werden, leisten neue Beiträge für das Verständnis von organischem Wachstum. Der demonstrierte Einfluss von chemischer Modifikation auf verschiedene Aspekte des Strukturwachstums, wie z.B. auf die Filmrauigkeit, Kristallphasenreinheit und molekulare Diffusivität, zeigt zudem das hohe Potential dieser Methode zur Steuerung des organischen Wachstums. Aus den genannten Gründen kann diese Arbeit neue Impulse für die Erforschung und spätere Anwendung von funktionalen organischen Dünnschichtsystemen setzen.Functional organic molecules are promising for the application in future relevant technologies such as organic light emitting diodes (OLEDs), solar cells, transistors and bio-sensors. One of the processing methods to fabricate organic devices is organic molecular beam deposition. In this process, the complexly interacting molecules grow via self-assembly as thin films on a substrate. Due to the close structure-property relationship, the growth process constitutes a highly interesting and important scientific challenge for both application oriented as well as fundamental research and is the topic of the present thesis. The experimental results and conceptual methods presented in this thesis contribute new stimuli to the understanding of the molecular self-assembly. The demonstrated influence of chemical tuning on various facets of structure formation, such as film roughness, crystal phase purity and molecular diffusivities, uncovers the strong potential of this approach for steering organic growth. Therefore, the present work has implications for future research and application of functional organic thin films.
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Schünemann, Christoph Verfasser], Karl [Akademischer Betreuer] [Leo, and Manfred [Akademischer Betreuer] Stamm. "Organic Small Molecules: Correlation between Molecular Structure, Thin Film Growth, and Solar Cell Performance / Christoph Schünemann. Gutachter: Karl Leo ; Manfred Stamm. Betreuer: Karl Leo." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://d-nb.info/1068443944/34.
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Schünemann, Christoph [Verfasser], Karl [Akademischer Betreuer] Leo, and Manfred [Akademischer Betreuer] Stamm. "Organic Small Molecules: Correlation between Molecular Structure, Thin Film Growth, and Solar Cell Performance / Christoph Schünemann. Gutachter: Karl Leo ; Manfred Stamm. Betreuer: Karl Leo." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-105169.
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Adamovic, Dragan. "Molecular Dynamics Studies of Low-Energy Atom Impact Phenomena on Metal Surfaces during Crystal Growth." Doctoral thesis, Linköpings universitet, Teoretisk Fysik, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-7165.
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It is a well-known fact in the materials science community that the use of low-energy atom impacts during thin film deposition is an effective tool for altering the growth behavior and for increasing the crystallinity of the films. However, the manner in which the incident atoms affect the growth kinetics and surface morphology is quite complicated and still not fully understood. This provides a strong incentive for further investigations of the interaction among incident atoms and surface atoms on the atomic scale. These impact-induced energetic events are non-equilibrium, transient processes which complete in picoseconds. The only accessible technique today which permits direct observation of these events is molecular dynamics (MD) simulations. This thesis deals with MD simulations of low-energy atom impact phenomena on metal surfaces during crystal growth. Platinum is chosen as a model system given that it has seen extended use as a model surface over the past few decades, both in experiments and simulations. In MD, the classical equations of motion are solved numerically for a set of interacting atoms. The atomic interactions are calculated using the embedded atom method (EAM). The EAM is a semi-empirical, pair-functional interatomic potential based on density functional theory. This potential provides a physical picture that includes many-atom effects while retaining computational efficiency needed for larger systems. Single adatoms residing on a surface constitute the smallest possible clusters and are the fundamental components controlling nucleation kinetics. Small two-dimensional clusters on a surface are the result of nucleation and are present during the early stages of growth. These surface structures are chosen as targets in the simulations (papers I and II) to provide further knowledge of the atomistic processes which occur during deposition, to investigate at which impact energies the different kinetic pathways open up, and how they may affect growth behavior. Some of the events observed are adatom scattering, dimer formation, cluster disruption, formation of three-dimensional clusters, and residual vacancy formation. Given the knowledge obtained, papers III and IV deal with growth of several layers with the aim to study the underlying mechanisms responsible for altering growth behavior and how the overall intra- and interlayer atomic migration can be controlled by low-energy atom impacts.On the day of the defence date the status of article II was Accepted.
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Isaacs, Steven Ray. "Molecular Assembly of Monolayer-Protected Gold Nanoparticles and their Chemical, Thermal, and Ultrasonic Stabilities." TopSCHOLAR®, 2018. https://digitalcommons.wku.edu/theses/3048.
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Gold monolayer-protected nanoclusters (MPCs) with average diameters of 1-5 nm protected by alkane- and arenethiolates were synthesized. Mixed-monolayer protected nanoparticles (MMPCs) were prepared by functionalizing hexanethiolate-protected MPCs with either 11-mercaptoundecanoic acid (MUA-MMPC), 11-mercaptoundecanol (MUO-MMPC), or 4-aminothiophenol (ATP-MMPC) using ligand place exchange. Presentation of various chemical reagents such as nucleophile, acid, or base and change in physical environment through ultrasonic and thermal irradiation resulted in changes to particles and their physical properties. Thermogravimetric analysis (TGA) was used to measure maximum temperature of the derivated thermogravimetric peaks (Tmax,DTG) as a means of comparing temperature dependence of mass loss. The absorption spectrum within the surface plasmon resonance (SPR) band was monitored over time throughout chemical and ultrasonic treatments to assess stability of these particles in solution.
MUA-MMPCs and ATP-MMPCs were self-assembled with Cu2+, poly(sodium 4- styrenesufonate), poly(allylamine hydrochloride), generation 2 polyamidoamine dendrimer, and C60 fullerene as linking molecules on functionalized glass substrates using a layer-by-layer approach resulting in nanoparticle multi-layer films. The thin films were characterized using UV-vis spectroscopy during deposition, and then before and after chemical treatment, and thermal and ultrasonic irradiation to assess stability of nanocomposites.
Finally, an in-situ cross-linking approach was used to deposit gold MPC-C60 thin film nanocomposite on functionalized glass substrate. UV-vis spectroscopy was used to monitor deposition rates of the resulting film in comparison with the MPC-C60 multilayer film assembled layer-by-layer. These MPC-C60 nanocomposites were also characterized using conductive atomic force microscopy (C-AFM).
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Pippenger, Phillip McKinney. "Photoluminescence of crystalline thin film buckminsterfullerene." Thesis, 1995. http://hdl.handle.net/1911/13983.
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A method is described for the growth of high purity crystalline thin film C$\sb{60}$. Films grown by this method are analyzed by means of x-ray diffraction, low energy electron diffraction, and photoluminescence. An excimeric model of the processes leading to the observed photoluminescence spectrum is proposed. This model is supported by the locations of spectral features in the photoluminescence spectrum as well as by agreement with the cooling dependence, temperature dependence, and the lack of film thickness dependence of the photoluminescence spectrum. The model is used to explain the observed photoluminescence spectrum of polycrystalline C$\sb{60}$.
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Su, Che-Wei, and 蘇哲暐. "Molecular Dynamics Simulation of thin film growth." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/51951036289647608448.
Full textAbstract:
碩士國立中央大學
光電科學研究所
91
Optical coating is a process in which a theoretical design is put into practice. The key to a successful production of high-quality thin film faithful to its original design is the choice and precise control of environment parameters during the deposition process. However, the relation between those parameters and the characteristics of thin film is not completely understood yet. Moreover, experiments have not been able to provide enough information with regard to the dynamic behavior and mechanism of thin film in the formation process and its microstructure and characteristics. Therefore this study takes a different approach and makes use of molecular dynamics simulation to construct a two-dimensional simulation system. Substrate temperature, incident kinetic energy, deposition rate, and incident angle are variables. The simulation results are then discussed to investigate the effects of the various environment parameters on thin film.
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Wu, Jin-Yin, and 鄔經英. "Study of Self-Assembled Multilayer Molecular Thin Film." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/93996314903398104084.
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碩士國立中正大學
化學研究所
85
Self-organized molecular thin films with well-defined structure and orienation are gaining wide attention for their potential application such as opto-electronic device and biomembranes. The purpose of this research is prepare multilayer film with C60 molecule as the bridge between layers. Based on the fact that C60 forms charge-transfer complex with amine moiety at low temperature, a facile process is designed to achieve the multilayer. Quartz, silicon wafer were used as the substrate for film build-up. The film structure was characterized by reflection-absorption IR, ellipsometry, contact angle measurement and UV spectroscopy.
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Lee, Tsung-Han, and 李宗翰. "Molecular Dynamics Simulation for Au-Pt Thin Film Deposition." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/31810642453366729178.
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"Elastic Properties of Molecular Glass Thin Films." Doctoral diss., 2011. http://hdl.handle.net/2286/R.I.9351.
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abstract: This dissertation provides a fundamental understanding of the impact of bulk polymer properties on the nanometer length scale modulus. The elastic modulus of amorphous organic thin films is examined using a surface wrinkling technique. Potential correlations between thin film behavior and intrinsic properties such as flexibility and chain length are explored. Thermal properties, glass transition temperature (Tg) and the coefficient of thermal expansion, are examined along with the moduli of these thin films. It is found that the nanometer length scale behavior of flexible polymers correlates to its bulk Tg and not the polymers intrinsic size. It is also found that decreases in the modulus of ultrathin flexible films is not correlated with the observed Tg decrease in films of the same thickness. Techniques to circumvent reductions from bulk modulus were also demonstrated. However, as chain flexibility is reduced the modulus becomes thickness independent down to 10 nm. Similarly for this series minor reductions in Tg were obtained. To further understand the impact of the intrinsic size and processing conditions; this wrinkling instability was also utilized to determine the modulus of small organic electronic materials at various deposition conditions. Lastly, this wrinkling instability is exploited for development of poly furfuryl alcohol wrinkles. A two-step wrinkling process is developed via an acid catalyzed polymerization of a drop cast solution of furfuryl alcohol and photo acid generator. The ability to control the surface topology and tune the wrinkle wavelength with processing parameters such as substrate temperature and photo acid generator concentration is also demonstrated. Well-ordered linear, circular, and curvilinear patterns are also obtained by selective ultraviolet exposure and polymerization of the furfuryl alcohol film. As a carbon precursor a thorough understanding of this wrinkling instability can have applications in a wide variety of technologies.Dissertation/Thesis
Ph.D. Chemical Engineering 2011
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Hung, Jun-Xian, and 黃俊憲. "Study on the Molecular Beam Deposition of CuInSe2 Thin Film." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/07051813663172868817.
Full textAbstract:
碩士國立中山大學
電機工程學系研究所
91
The objective of this proposed study is to develop the new material CuInSe2 for large area, low cost and high efficiency commercial CuInSe2 based solar cell for the solar resource in Taiwan. The compositions of CuInSe2 films are modulated precisely to obtain an ideal electrical and optical characteristics resulting in high conversion efficiency for commercial solar cell applications. Numerous experimental investigations have shown the electrical properties of undoped CuInSe2 are dominated by various types of electrically active intrinsic defects caused by the deviations from the ideal stoichiometry. Without any intentional doping CuInSe2 can be made n-type and p-type conducting with carrier concentrations varying over many orders of magnitude either by slightly changing the composition of the material during growth or by appropriate post-growth annealing procedures. Several attempts have been made successfully by the crucial construction and application of intrinsic defect chemistry model to investigate the trend in the conductivity of CuInSe2, however, there investigation still remain no clear evidence to directly correlate composition and electrical properties reported by several authors, and the results of experimental data shows in contradiction to the intrinsic defect model. According to the point defect model, that samples with DX＜0 and larger values of |DY| are always n-type conducting, and sample with DX>0 and DY>0 are always p-type conducting. In addition, as DX<0 and DY<0, the dominant defect pair calculated from the point defect model is VCu and InCu, their concentrations varies as a function of DY. Once DY is relatively more negative, [VCu] increase and that forms [VCu]＞[InCu]. Therefore, the electrical conductivity of CuInSe2 changed from n-type to p-type. The Growth model of MBE is considered to investigate the reactive mechanism of epitaxial growth. At 500℃, the BEP of In and Cu molecular beam fluxes supplied were 5×10-8~5×10-7 torr for the MBE growth of CuInSe2 films. The change of Se molecular beam flux not only affect the composition of CuInSe2 films, but also the deviation from molecularity DX and the deviation from valence stoichiometry. As Se molecular beam flux increase to 10-6 torr, the concentrations of dominant defects show to decrease about three orders. Thus, the increase of Se BEP results in increasing the mobility as well as the conductivity. On the whole, this study is based on the simulation to investigate the mechanism of MBE. It could be used to control precisely the composition of CuInSe2 films leading to obtain the electrical characteristics for solar cell design.
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Folinsky, Anna Barr. "Investigating Molecular Size Variations in Thin Film Chemical Vapor Sensors." Thesis, 2010. https://thesis.library.caltech.edu/5834/3/ABF-Ch1.pdf.
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Vapor sensing arrays composed of broadly responsive, chemically sensitive detectors have been explored for many years. They have been used in fields ranging from good quality control, to environmental monitoring and explosives detection, to disease diagnostics. All of these tasks require high sensitivity and fine discrimination ability. As new challenges arise, the ability to understand the performance and improve the availability of array components becomes paramount.
This work details progress in gaining greater understanding of certain chemical substrates used in sensor arrays. Specifically, arrays using insulator/carbon black composite sensors have been prepared using either polymer or non-volatile small organic molecules as the insulating, chemically sensitive component. The crystallinity of the small molecules as compared to the polymers was determined to cause the differing formulation requirements between the polymers and the small molecules.
Additionally, arrays of sensors composed of varying molecular weights of a given polymer were examined. Very low molecular weights of polystyrene, a high glass transition temperature polymer, exhibited improved behavior and response times compared to higher molecular weights. Finally, arrays composed of varied length carboxylic and dicarboxylic acids were studied. Of these two homologous series, the arrays composed of carboxylic acids provided better discrimination than did those composed of dicarboxylic acids, suggesting the utility of sensor materials containing multiple accessible functional groups.
These studies, taken together, suggest several new ways to increase the number of compounds and chemical functionalities available to use in chemical vapor sensors. Increased sensor choice allows construction of more broadly responsive and finely discriminating sensor arrays, thereby increasing the general utility of composite vapor sensor arrays.
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Schünemann, Christoph. "Organic Small Molecules: Correlation between Molecular Structure, Thin Film Growth, and Solar Cell Performance." Doctoral thesis, 2012. https://tud.qucosa.de/id/qucosa%3A26570.
Full textAbstract:
Das wesentliche Ziel dieser Doktorarbeit ist es, die Zusammenhänge zwischen der Struktur von kleinen organischen Molekülen, deren Anordnung in der Dünnschicht und der Effizienz organischer Solarzellen zu beleuchten. Die Kombination der komplementären Methoden spektroskopischer Ellipsometrie (VASE) und Röntgenstreuung, vor allem der unter streifendem Einfall (GIXRD), hat sich als sehr effiient für die Strukturuntersuchungen organischer Dünnschichten erwiesen. Zusammen geben sie einen detailreichen Einblick in die intermolekulare Anordnung, die Kristallinität, die molekulare Orientierung, die optischen Konstanten n und k und die Phasenseparation von organischen Schichten. Zusätzlich wird die Topografie der organischen Dünnschicht mit Rasterkraftmikroskopie untersucht.
Der erste Fokus liegt auf der Analyse des Dünnschichtwachstums von Zink-Phthalocyanin (ZnPc) Einzelschichten. Für alle untersuchten Schichtdicken (5, 10, 25, 50 nm) und Substrattemperaturen (Tsub=30°C, 60°C, 90°C) zeigt ZnPc ein kristallines Schichtwachstum mit aufrecht stehenden ZnPc Molekülen. Um effiziente organische Solarzellen herzustellen, werden Donor- und Akzeptormoleküle üblicherweise koverdampft. Bei der Mischung von Donor- und Akzeptormolekülen bildet sich eine gewisse Phasenseparation aus, deren Form wesentlich für die Ladungsträgerextraktion entlang der Perkolationpfade ist. Der Ursprung dieser Phasenseparation wird innerhalb dieser Arbeit experimentell für ZnPc:C60 Absorber-Mischschichten untersucht. Um die Ausprägung der Phasenseparation zu variieren, werden verschiedene Tsub (30°C, 100°C, 140°C) und Mischverhältnisse (6:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:6) bei der Koverdampfung von ZnPc und C60 angewendet. GIXRD Messungen zeigen, dass hier der bevorzugte Kristallisationsprozess von C60 Molekülen die treibende Kraft für eine effiziente Phasenseparation ist. Solarzellen, die ZnPc:C60 Mischschichten mit verbesserter Phasenseparation enthalten (Tsub=140°C, 1:1), zeigen eine verbesserte Ladungsträgerextraktion und somit eine höhere Effizienz von 3,0% im Vergleich zu 2,5% für die entsprechende Referenzsolarzelle (Tsub=30°C, 1:1).
Im zweiten Teil der Arbeit wird der Einfluss der Molekülorientierung auf die Dünnschichtabsorption beispielhaft an ZnPc und Diindenoperylen (DIP) untersucht. DIP und ZnPc Moleküle, die auf schwach wechselwirkenden Substraten wie Glas, SiO2, amorphen organischen Transportschichten oder C60 aufgedampft sind, zeigen eine eher stehende Orientierung innerhalb der Dünnschicht in Bezug zur Substratoberfläche. Im Gegensatz dazu führt die Abscheidung auf stark wechselwirkenden Substraten, wie z.B. einer Gold- oder Silberschicht oder 0.5 nm bis 2 nm dünnen PTCDA (3,4,9,10-Perylentetracarbonsäuredianhydrid) Templatschichten laut GIXRD und VASE Messungen dazu, dass sich die ZnPc und DIP Moleküle eher flach liegend orientieren. Dies führt zu einer wesentlich besseren Dünnschichtabsorption da das molekulare Übergangsdipolmoment jeweils innerhalb der Ebene des ZnPc und des DIP Moleküls liegt. Ein Einbetten von Gold- oder Silberzwischenschichten in organischen Solarzellen führt leider zu keinen klaren Abhängigkeiten, da die verbesserte Absorption durch die flach liegenden Moleküle von Mikrokavitäts- und plasmonischen Effekten überlagert wird. Ebenso wenig führte das Einfügen einer PTCDA-Zwischenschicht in organischen Solarzellen zum Erfolg, da hier Transportbarrieren den Effekt der verbesserten Absorption überlagern.
Das letzte Kapitel konzentriert sich auf den Einfluss der Molekülstruktur auf das Dünnschichtwachstum am Beispiel von DIP und dessen Derivaten Ph4-DIP und P4-Ph4-DIP, Isoviolanthron und Bis-nFl-NTCDI (N,N-Bis(fluorene-2-yl)-naphthalenetetra-carboxylic Diimid) Derivaten. GIXRD Messungen belegen deutlich, dass die sterischen Behinderungen, hervorgerufen durch die Phenylringe (für Ph4-DIP und P4-Ph4-DIP) und Seitenketten (für Bis-nFl-NTCDI), ein amorphes Schichtwachstum induzieren. Im Vergleich sind die Dünnschichten von DIP und Bis-HFl-NTCDI kristallin. Bezüglich der Molekülorientierung und folglich der Absorption von DIP und dessen Derivaten kann ein starker Einfluss des Schichtwachstums beobachtet werden. In Solarzellen verhindert die Präsenz der Phenylringe eine effiziente Phasenseparation der Mischschichten aus (P4-)Ph4-DIP:C60, was zu einer verschlechterten Ladungsträgerextraktion und damit zu einem reduzierten Füllfaktor (FF) von 52% im Vergleich zu dem entsprechender DIP:C60 Solarzellen mit FF=62% führt Die Untersuchungen an der Bis-nFl-NTICDI Serie zeigen ein ähnliches Ergebnis: Auch hier zeichnen sich die amorphen Schichten aus Bis-nFl-NTCDI Molekülen mit Seitenketten durch schlechtere Transporteigenschaften aus als nanokristalline Bis-HFl-NTCDI Schichten.The aim of this thesis is to demonstrate correlations between the molecular structure of small organic molecules, their arrangement in thin films, and the solar cell performance. For structure analysis of the organic thin films, the combination of variable angle spectroscopic ellipsometry (VASE) and grazing incidence X-ray diffraction (GIXRD) as complementary methods turned out to be a powerful combination. Using both methods, it is possible to obtain information about the crystallinity, crystallite size, intermolecular arrangement, mean molecular orientation, optical constants n and k, and phase separation within thin films. In addition, the topography of thin films is analyzed by atomic force microscopy. First, the thin film morphology of pristine zinc-phthalocyanine (ZnPc) films deposited at different substrate temperatures (Tsub=30°C, 60°C, 90°C) and for varying film thicknesses (5, 10, 25, 50 nm) is investigated. The ZnPc films grow highly crystalline with an upright standing molecular orientation with respect to the substrate surface for all investigated Tsub and all film thicknesses. In effcient organic solar cells, donor and acceptor molecules are commonly co-deposited to form a blend absorber film. This is usually accompanied by a certain phase separation between donor and acceptor molecules leads to a formation of percolation paths necessary to extract electrons and holes towards the electrodes. For ZnPc:C60 blends the origin of this phase separation process is analyzed by investigating different degrees of phase separation induced by film deposition at different Tsub (30°C, 100°C, 140°C) and for different blend ratios (6:1, ... , 1:6 (vol%)). GIXRD measurements indicate that the preferred crystallization of C60 is the driving force for good phase separation. Solar cells with improved phase separation of ZnPc:C60 blends (Tsub=140°C, 1:1) reveal a better charge carrier extraction and thus enhanced effciencies of 3.0% in comparison to 2.5% for the reference device (Tsub=30°C, 1:1). In the second part, the impact of molecular orientation within the absorber thin films on light harvesting is examined for pristine ZnPc and diindenoperylene (DIP) films. For film deposition on weakly interacting substrates like glass, SiO2, amorphous organic transport films, or C60, the orientation of DIP and ZnPc molecules is found to be upright standing. In contrast, GIXRD and VASE measurements show that films deposited onto strongly interacting substrates like Au and Ag, as well as on thin PTCDA templating layers lead to nearly flat-lying ZnPc and DIP molecules. Since the molecular transition dipole moment is oriented in the plane of the DIP and ZnPc molecules, the light absorption in films with flat-lying molecules is strongly improved. Unfortunately, an implementation of Au or Ag sublayers in organic solar cells does not result in reliable dependencies since the enhanced absorption by an improved molecular orientation is superimposed by different effects like microcavity and plasmonic effects. The implementation of PTCDA interlayers leads to transport barriers making the solar cell data interpretation difficult. In the last part, the influence of molecular structure on thin film growth is studied for DIP and its derivatives Ph4-DIP and P4-Ph4-DIP, isoviolanthrone, and Bis-nFl-NTCDI derivatives. GIXRD measurements reveal that steric hindrance is induced by the addition of side chains (for Bis-nFl-NTCDI) and phenyl rings (for Ph4-DIP and P4-Ph4-DIP) (N,N-Bis(fluorene-2-yl)-naphthalenetetra-carboxylic diimide) leading to an amorphous thin film growth. In contrast, DIP films and Bis-HFl-NTCDI films are found to be crystalline. The mean molecular orientation and hence the absorption is strongly affected by the different growth modes of DIP and its derivatives. In OSC, the presence of the phenyl rings prevents an effcient phase separation for (P4-)Ph4-DIP:C60 blends which causes diminished charge extraction in comparison to the crystalline DIP:C60 blends. For the Bis-nFl-NTCDI series, the transport properties are significantly worse in the amorphous films composed of Bis-nFl-NTCDI derivatives with alkyl chains in comparison to the nanocrystalline films made of the bare Bis-HFl-NTCDI.
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Chia-Lin, Chang, and 張家林. "Molecular dynamics simulation of thin film growth on GMR corrugated structure." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/86066480526561484853.
Full textAbstract:
碩士國立成功大學
機械工程學系
89
This paper presents the use of molecular dynamics in simulating thin film growth on GMR corrugated structures. The simulation model mainly concerns the deposition of Co atoms on a V-shape Cu substrate. The many-body, tight-binding potential model is utilized in the MD simulation to represent the inter-atomic force which exists between the atoms. The interface width is used to quantify the variation of surface roughness at the transient and steady states. The paper investigates the influence of incident energy on the deposited film surface property and on the growing mechanism, for both vertical and oblique deposition. The results demonstrate how the growing characteristics are influenced by different incident energies and by different deposition directions. It is found that at relatively low incident energies the film growth tends to be in a 3-D cluster mode and that a void track is formed, whose growing direction is almost equal to the surface normal to the two inclined surfaces. The uneven thickness found along the base of the V-shape is mainly due to the deposited atoms which accumulate at the bottom of the V-groove when the incident energy is at a relatively high level. It is found that there exists an optimal incident energy which produces the best film surface property. The film surface property can be improved by changing the incident direction relative to two inclined directions of . Smaller deviation angles yield better film surface properties for low incident energy. Conversely, higher levels of incident energy result in worse film surface properties.
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Chen, Wei-Ru, and 陳瑋如. "A Micro Fabricated Vapor Preconcentrator Employing Carbon Molecular Sieve Thin Film." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/72824459597299263307.
Full textAbstract:
碩士國立臺灣師範大學
化學系
100
In this study, the adsorption of volatile organic compounds (VOCs) by the synthesized porous carbon based film was investigated. For developing a VOC micro preconcentrator chips, we directly synthesized carbon based adsorbent film inside a pre-sealed and anodic bonded micro device. The precursor material was mixed with a solvent and injected into the chip channel to form a thin layer then pyrolyzed at high temperature and under the oxygen free atmosphere to form a microporous film. The physical properties including surface morphology, microstructure image, and BET surface area were inspected by FE-SEM and specific surface area & pore size distribution analyzer. When using cellulose as the starting material, it was slowly heated at a rate of 10 ℃/min from room temperature to 600 ℃ and maintained for two hours under high purity nitrogen atmosphere. While for saran, it was heated to a higher temperature 700 ℃ and maintained for only one hour. The BET surface area obtained was 308 m2/g and 899 m2/g, respectively, which was sufficiently comparable to many commercial adsorbents. The adsorption /desorption experiment was performed using toluene as the target VOC. It revealed that the carbon film obtained possesses very good performance where the preconcentration factor can achieve 103 to 104. Finally, we applied Wheeler model to assess the thermodynamic capacity of our synthesized adsorbent film. The carbon films in this study show good durability, reproducibility that can be applied in various designs of VOC micro preconcentrator chips.