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Alshekhli, Omar. "PULSED ELECTRON DEPOSITION AND CHARACTERIZATION OF NANOCRYSTALLINE DIAMOND THIN FILMS." Thesis, Laurentian University of Sudbury, 2013. https://zone.biblio.laurentian.ca/dspace/handle/10219/2078.
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Diamond is widely known for its extraordinary properties, such as high hardness, thermal conductivity, electron mobility, energy bandgap and durability making it a very attractive material for many applications. Synthetic diamonds retain most of the attractive properties of natural diamond. Among the types of synthetic diamonds, nanocrystalline diamond (NCD) is being developed for electrical, tribological, optical, and biomedical applications.
In this research work, NCD films were grown by the pulsed electron beam ablation (PEBA) method at different process conditions such as accelerating voltage, pulse repetition rate, substrate material and temperature. PEBA is a relatively novel deposition technique, which has been developed to provide researchers with a new means of producing films of equal or better quality than more conventional methods such as Pulsed Laser Deposition, Sputtering, and Cathodic Vacuum Arc.
The deposition process parameters have been defined by estimating the temperature and pressure of the plasma particles upon impact with the substrates, and comparing the data with the carbon phase diagram. Film thickness was measured by visible reflectance spectroscopy technique and was in the range of 40 – 230 nm. The nature of chemical bonding, namely, the ratio (sp3/sp3+sp2) and nanocrystallinity percentage were estimated using visible Raman spectroscopy technique. The films prepared from the ablation of a highly ordered pyrolytic graphite (HOPG) target on different substrates consisted mainly of nanocrystalline diamond material in association with a diamond-like carbon phase. The micro-structural properties and surface morphology of the films were studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The mechanical properties of the NCD films were evaluated by nano-indentation.
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Hyde, Robert H. "Hollow-electrode pulsed plasma deposition of titanium and carbon thin films." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001856.
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Jenderka, Marcus. "Pulsed Laser Deposition of Iridate and YBiO3 Thin Films." Doctoral thesis, Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-219334.
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Die vorliegende Arbeit befasst sich mit dem Dünnfilmwachstum der ternären Oxide Na2IrO3, Li2IrO3, Y2Ir2O7 und YBiO3. All diesen oxidischen Materialien ist gemein, dass sie Verwirklichungen sogenannter Topologischer Isolatoren oder Spin-Flüssigkeiten sein könnten. Diese neuartigen Materiezustände versprechen eine zukünftige Anwendung in der Quantencomputation, in magnetischen Speichern und in elektrischen Geräten mit geringer Leistungsaufnahme. Die Herstellung der hier gezeigten Dünnfilme ist daher ein erster Schritt zur Umsetzung dieser Anwendungen in der Zukunft. Alle Dünnfilme werden mittels gepulster Laserplasmaabscheidung auf verschiedenen einkristallinen Substraten hergestellt. Die strukturellen, optischen und elektrischen Eigenschaften der Filme werden mittels etablierter experimenteller Verfahren wie Röntgenbeugung, spektroskopischer Ellipsometrie und elektrischenWiderstandsmessungen untersucht. Die strukturellen Eigenschaften von erstmalig in der Masterarbeit des Authors verwirklichten Na2IrO3-Dünnfilmen können durch Abscheidung einer ZnO-Zwischenschicht deutlich verbessert werden. Einkristalline Li2IrO3-Dünnfilme mit einer definierten Kristallausrichtung werden erstmalig hergestellt. Die Messung der dielektrischen Funktion gibt Einblick in elektronische Anregungen, die gut vergleichbar mit Li2IrO3-Einkristallen und verwandten Iridaten sind. Des Weiteren wird aus den Daten eine optische Energielücke von ungefähr 300 meV bestimmt. In Y2Ir2O7-Dünnfilmen wird eine mögliche (111)-Vorzugsorientierung in Wachstumsrichtung gefunden. Im Vergleich mit der chemischen Lösungsabscheidung zeigen die hier mittels gepulster Laserplasmaabscheidung hergestellten YBiO3-Dünnfilme eine definierte, biaxiale Kristallausrichtung in der Wachstumsebene bei einer deutlich höheren Schichtdicke. Über die gemessene dielektrische Funktion können eine direkte und indirekte Bandlücke bestimmt werden. Deren Größe gibt eine notwendige experimentelle Rückmeldung an theoretische Berechnungen der elektronischen Bandstruktur von YBiO3, welche zur Vorhersage der oben erwähnten, neuartigen Materiezuständen verwendet werden. Nach einer Einleitung und Motivation dieser Arbeit gibt das zweite Kapitel einen Überblick über den gegenwärtigen Forschungsstand der hier untersuchten Materialien. Die folgenden zwei Kapitel beschreiben die Probenherstellung und die verwendeten experimentellen Untersuchungsmethoden. Anschließend werden für jedes Material einzeln die experimentellen Ergebnisse dieser Arbeit diskutiert. Die Arbeit schließt mit einer Zusammenfassung und einem AusblickThe present thesis reports on the thin film growth of ternary oxides Na2IrO3, Li2IrO3, Y2Ir2O7 and YBiO3. All of these oxides are candidate materials for the so-called topological insulator and spin liquid, respectively. These states of matter promise future application in quantum computation, and in magnetic memory and low-power electronic devices. The realization of the thin films presented here, thus represents a first step towards these future device applications. All thin films are prepared by means of pulsed laser deposition on various single-crystalline substrates. Their structural, optical and electronic properties are investigated with established experimental methods such as X-ray diffraction, spectroscopic ellipsometry and resistivity measurements. The structural properties of Na2IrO3 thin films, that were previously realized in the author’s M. Sc. thesis for the first time, are improved significantly by deposition of an intermediate ZnO layer. Single-crystalline Li2IrO3 thin films are grown for the first time and exhibit a defined crystal orientation. Measurement of the dielectric function gives insight into electronic excitations that compare well with single crystal samples and related iridates. From the data, an optical energy gap of about 300 meV is obtained. For Y2Ir2O7 thin films, a possible (111) out-of-plane preferential crystal orientation is obtained. Compared to chemical solution deposition, the pulsed laser-deposited YBiO3 thin films presented here exhibit a biaxial in-plane crystal orientation up to a significantly larger film thickness. From the measured dielectric function, a direct and indirect band gap energy is determined. Their magnitude provides necessary experimental feedback for theoretical calculations of the electronic structure of YBiO3, which are used in the prediction of the novel states of matter mentioned above. After the introduction and motivation of this thesis, the second chapter reviews the current state of the science of the studied thin film materials. The following two chapters introduce the sample preparation and the employed experimental methods, respectively. Subsequently, the experimental results of this thesis are discussed for each material individually. The thesis concludes with a summary and an outlook
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Waller, Gordon Henry. "Template Directed Growth of Nb doped SrTiO3 using Pulsed Laser Deposition." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/32723.
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Oxide materials display a wide range of physical properties. Recently, doped complex
oxides have drawn considerable attention for various applications including thermoelectrics.
Doped complex oxide materials have high Seebeck coefficients (S) and electrical conductivities
(o) comparable to other doped semiconductors but low thermoelectric figure of merit ZT values
due to their poor thermal conductivities. For example, niobium doped strontium titanate
(SrNbxTi1-xO3 or simply Nb:STO) has a power factor comparable to that of bismuth telluride.
Semiconductor nanostructures have demonstrated a decrease in thermal conductivity () resulting in an increase in the thermoelectric figure of merit (ZT). Nanostructures of doped oxides like niobium doped strontium titanate, may also lead to decreased and a corresponding increase in ZT. The major impediment to nanostructured oxide thermoelectric materials is the lack of suitable fabrication techniques for testing and eventual use. Electron Beam Lithography(EBL) was used to pattern poly-methyl-methacrylate (PMMA) resists on undoped single crystalline SrTiO3 (STO) substrates which were then filled with Nb:STO using Pulsed Laser Deposition (PLD) at room temperature. This technique produced nanowires and nanodots with critical dimensions below 100 nm, and a yield of approximately 95%. In addition to scanning electron microscopy and atomic force microscopy morphological studies of the patterned oxide, thin film analogues were used to study composition, crystallinity and electrical conductivity of the material in response to a post deposition heat treatment. Since the thin films were grown under similar experimental parameters as the oxide nanostructres, the patterned oxides are believed to be stoichiometric and highly crystalline. The study found that using a combination of EBL and PLD, it is possible to produce highly crystalline, doped complex oxide nanostructures with excellent control over morphology. Furthermore, the technique is applicable to nearly all materials and provides the capability of patterning doped oxide materials without the requirement of etching or multiple lithography steps makes this approach especially interesting for future fundamental materials research and novel device fabrication.Master of Science
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Nsengiyumva, Schadrack. "Formation and characterization of pulsed laser ablated magnetoresistive material." Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52852.
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Thesis (MSc)--Stellenbosch University, 2002.ENGLISH ABSTRACT: In this investigation the formation of thin film manganites and their electrical characteristics is studied. In order to see the effect of oxidation states on magneto-resistivity, 80% of Mn is replaced by Fe. Pulsed laser deposition (3 J/cm2), carried out in oxygen partial pressures ranging from 0.01 mbar to 1.00 mbar was used to fabricate the thin films from two target compositions, namely La2CaMn2.94Feo.0609 and La2CaMno.6Fe2.409. Films were deposited on Si< 100 >, MgO< 100 >, SrTi03< 100 > and LaAl03< 100 > single crystal substrates. Samples were characterized by RBS, AFM, SEM, and XRD. Electrical measurements were also carried out. One of the main characterization techniques in this investigation is Rutherford Backscattering Spectrometry (RBS). It has been shown that RBS is a very powerful characterization technique when used in conjunction with the RUMP simulation program. The effect of various parameters can be determined beforehand by RUMP simulation of the thin film structures to be investigated. Simulation shows that RBS is an excellent characterization tool for determining film thickness and stoichiometry. The role of oxygen uptake in La2CaMn3_xFexOg was investigated as the oxidation states of elements in manganite materials have a large effect on their magnetoresistive properties. The height of the La signal can be used as a measure of the oxygen content. RBS spectra of films deposited on single crystal silicon substrates at different ambient pressures show that the fit between simulated and measured RBS spectra improves with higher oxygen pressures, thereby indicating better quality manganite material. The RBS spectra also show that the films have good stoichiometry. Atomic force microscopy was used to determine the roughness of the thin films. The annealed film (average roughness 4.5 nm) shows a surface smoother than the non-annealed film (average roughness 5.3 nm). SEM measurements show that in the case of samples having a high Fe content, the crystallite size varies between about 0.04 11m and 0.10 11m, while for samples with high manganese content, the crystallinity varies between 0.03 jJ,m and 0.06jLm. Manganites were analyzed using Bragg-Brentano (28) X-ray diffraction. Measurements show that manganite films cannot be grown epitaxially on Si< 100 > and MgO< 100 > single crystals due to a large lattice mismatch. In the case of SrTi03 and LaAl03 several reflections and sharp peaks from the film can be seen, indicating reasonable epitaxial growth. SEM measurements of the samples however show polycrystallinity. Complete epitaxy has thus not occurred, but many grains have an epitaxial orientation. Resistance versus temperature (the room temperature to about 100 K) in zero magnetic field was measured for a La2CaMno.06Fe2.409 thin film and maximum resistance corresponding to about 108 K was found. At higher temperatures the resistance decreases as temperature increases. The manganite thin film therefore shows semiconductor behaviour. Resistance measurements carried out at different magnetic fields (0 - 1 T) show a small positive magnetoresistance of 0.83 %. Usually the magnetoresistance phenomenon is measured at higher magnetic fields and this could be the reason for our low value as well as the fact that the iron content could be too high.
AFRIKAANSE OPSOMMING: In hierdie ondersoek is die formasie en karakterisering van dunlagie manganiete ondersoek. Om die effek van oksidasie-toestand op magnetoresistiwiteit te bepaal, is 80% van die Mn verplaas deur Fe. Pulseerde laser deposissie(3 J/cm2), is uitgevoer by 'n parsiële suurstof druk tussen 0.10 en 1.00 mbar deur gebruik te maak van La2Ca Mn2.94Feo.o609 en La2CaMno.6Fe2.409 teiken skywe. Dunlagies was gedeponeer op Si
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Zhang, Hong Bo. "Optical and electrical properties of ZnO thin films prepared by pulsed laser deposition." HKBU Institutional Repository, 2000. http://repository.hkbu.edu.hk/etd_ra/225.
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Bowers, Cynthia Thomason. "Transmission Electron Microscopy Analysis of Silicon-Doped Beta-Gallium Oxide Films Grown by Pulsed Laser Deposition." Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1580120635333744.
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Ibrahim, Noor Baa'yah. "Properties of yttrium iron garnet thin films grown by pulsed laser ablation deposition." Thesis, University of Warwick, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343112.
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Wei, Haoming, Jose Luis Barzola-Quiquia, Chang Yang, Christian Patzig, Thomas Höche, Pablo Esquinazi, Marius Grundmann, and Michael Lorenz. "Charge transfer-induced magnetic exchange bias and electron localization in (111)- and (001)-oriented LaNiO3/LaMnO3 superlattices." American Institute of Physics, 2017. https://ul.qucosa.de/id/qucosa%3A23554.
Full textAbstract:
High-quality lattice-matched LaNiO3/LaMnO3 superlattices with monolayer terrace structure have
been grown on both (111)- and (001)-oriented SrTiO3 substrates by pulsed laser deposition. In contrast
to the previously reported experiments, a magnetic exchange bias is observed that reproducibly
occurs in both (111)- and (001)-oriented superlattices with the thin single layers of 5 and 7 unit cells,
respectively. The exchange bias is theoretically explained by charge transfer-induced magnetic
moments at Ni atoms. Furthermore, magnetization data at low temperature suggest two magnetic
phases in the superlattices, with Néel temperature around 10 K. Electrical transport measurements
reveal a metal-insulator transition with strong localization of electrons in the superlattices with the
thin LaNiO3 layers of 4 unit cells, in which the electrical transport is dominated by two-dimensional
variable range hopping.
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Souri, Maryam. "ELECTRONIC AND OPTICAL PROPERTIES OF METASTABLE EPITAXIAL THIN FILMS OF LAYERED IRIDATES." UKnowledge, 2018. https://uknowledge.uky.edu/physastron_etds/60.
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The layered iridates such as Sr2IrO4 and Sr3Ir2O7, have attracted substantial attention due to their novel electronic states originating from strong spin-orbit coupling and electron-correlation. Recent studies have revealed the possibilities of novel phases such as topological insulators, Weyl semimetals, and even a potential high-Tc superconducting state with a d-wave gap. However, there are still controversial issues regarding the fundamental electronic structure of these systems: the origin of the insulating gap is disputed as arising either from an antiferromagnetic ordering, i.e. Slater scheme or electron-correlation, i.e. Mott scheme. Moreover, it is a formidable task to unveil the physics of layered iridates due to the limited number of available materials for experimental characterizations.
One way to overcome this limit and extend our investigation of the layered iridates is using metastable materials. These materials which are far from their equilibrium state, often have mechanical, electronic, and magnetic properties that different from their thermodynamically stable phases. However, these materials cannot be synthesized using thermodynamic equilibrium processes. One way to synthesize these materials is by using pulsed laser deposition (PLD). PLD is able to generate nonequilibrium material phases through the use of substrate strain and deposition conditions. Using this method, we have synthesized several thermodynamically metastable iridate thin-films and have investigated their electronic and optical properties. Synthesizing and investigating metastable iridates opens a path to expand the tunability further than the ability of the bulk methods.
This thesis consists of four studies on metastable layered iridate thin film systems. In the first study, three-dimensional Mott variable-range hopping transport with decreased characteristic temperatures under lattice strain or isovalent doping has been observed in Sr2IrO4 thin films. Application of lattice strain or isovalent doping exerts metastable chemical pressure in the compounds, which changes both the bandwidth and electronic hopping. The variation of the characteristic temperature under lattice strain or isovalent doping implies that the density of states near the Fermi energy is reconstructed. The increased density of states in the Sr2IrO4 thin films with strain and isovalent doping could facilitate a condition to induce unprecedented electronic properties, opening a way for electronic device applications. In the second study, the effects of tuning the bandwidth via chemical pressure (i.e., Ca and Ba doping) on the optical properties of Sr2IrO4 epitaxial thin films has been investigated. Substitution of Sr by Ca and Ba ions exerts metastable chemical pressure in the system, which changes both the bandwidth and electronic hopping. The optical conductivity results of these thin films suggest that the two-peak-like optical conductivity spectra of the layered iridates originates from the overlap between the optically-forbidden spin-orbit exciton and the inter-site optical transitions within the Jeff = ½ band, which is consistent with the results obtained from a multi-orbital Hubbard model calculation. In the third study, thermodynamically metastable Ca2IrO4 thin- films have been synthesized. Since the perovskite structure of Ca2IrO4 is not thermodynamically stable, its bulk crystals do not exist in nature. We have synthesized the layered perovskite phase Ca2IrO4 thin- films from a polycrystalline hexagonal bulk crystal using an epitaxial stabilization technique. The smaller A-site in this compound compared to Sr2IrO4 and Ba2IrO4, increases the octahedral rotation and tilting, which enhance electron-correlation. The enhanced electron-correlation is consistent with the observation of increased gap energy in this compound. This study suggest that the epitaxial stabilization of metastable-phase thin-films can be used effectively for investigating complex-oxide systems. Finally, structural, transport, and optical properties of tensile strained (Sr1-xLax)3Ir2O7 (x = 0, 0.025, 0.05) thin-films have been investigated. While high-Tc superconductivity is predicted in the system, all of the samples are insulating. The insulating behavior of the La-doped Sr3Ir2O7 thin-films is presumably due to disorder-induced localization and ineffective electron-doping of La, which brings to light the intriguing difference between epitaxial thin films and bulk single crystals of the iridates. These studies thoroughly investigate a wide array of novel electronic and optical phenomena via tuning the relative strengths of electron correlation, electronic bandwidth, and spin-orbit coupling using perturbations such as chemical doping, and the stabilization of metastable phases in the layered iridates.
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Ghaffari, Nastaran. "Electrochemical deposition of Graphene Oxide- metal nano-composite on Pencil-Graphite Electrode for the high sensitivity detection of Bisphenol A by Adsorptive Stripping Differential Pulse Voltammetry." University of the Western Cape, 2018. http://hdl.handle.net/11394/6336.
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Magister Scientiae - MSc (Chemistry)Electrochemical platforms were developed based on pencil graphite electrodes (PGEs) modified electrochemically with reduced graphene oxide metal nanoparticles (ERGO–metalNPs) composite and used for the high-sensitivity determination of Bisphenol A (BPA) in water samples. Synergistic effects of both reduced Graphene Oxide sheets and metal nanoparticles on the performance of the pencil graphite electrode (PGE) were demonstrated in the oxidation of BPA by differential pulse voltammetry (DPV). A solution of graphene oxide (GO) 1 mg mL-1 and 15 ppm of metal stock solutions (1,000 mg L-1, atomic absorption standard solution) (Antimony or Gold) was prepared and after sonication deposited onto pencil graphite electrodes by cyclic voltammetry reduction. Different characterization techniques such as FT-IR, HR-SEM, XRD and Raman spectroscopy were used to characterize the GO and ERGO–metalNPs. Parameters that influence the electroanalytical response of the ERGO–SbNPs and ERGO–AuNPs such as, pH, deposition time, deposition potential, purging time were investigated and optimized. Well-defined, reproducible peaks with detection limits of 0.0125 μM and 0.062 μM were obtained for BPA using ERGO–SbNPs and ERGO–AuNPs respectively. The rGO-metalNPs–PGE was used for the quantification of BPA in tap water sample and proved to be suitable for the detection of BPA below USEPA prescribed drinking water standards of 0.087 μM.
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Klemm, Robert. "Zyklische Plastizität von mikro- und submikrokristallinem Nickel." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2004. http://nbn-resolving.de/urn:nbn:de:swb:14-1085403884093-17423.
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Im Rahmen der vorliegenden Arbeit wurde der Einfluss der Korngröße und der Gefügestabilität auf die zyklische Plastizität von mikro- und submikrokristallinem Nickel, hergestellt durch ECAP und PED, untersucht. Zur Gefügecharakterisierung kamen verschiedene elektronenmikroskopische und röntgenographische Methoden zum Einsatz. Die Untersuchungen zur Gefügestabilität zeigten, dass (i) die Stabilität der Korn- und Substruktur bei der zyklischen Verformung empfindlich vom Gefüge im Ausgangszustand abhängt, (ii) generell die Tendenz zur Umwandlung der vorhandenen Substruktur in eine universelle ermüdungstypische Substruktur besteht, diese Transformation jedoch durch die lokale Gefügebeschaffenheit be- bzw. verhindert sein kann und (iii) zur Erklärung des Entfestigungsverhaltens der ECAP-Materialien sowohl die Transformation der Substruktur als auch die Vergröberung der Kornstruktur berücksichtigt werden müssen. Auf der Basis der Ergebnisse der vorliegenden Arbeit und unter Hinzunahme von Resultaten aus der Literatur lassen sich Schlussfolgerungen zum Einfluss der Korngröße auf die zyklische Plastizität in einem vier Größenordnungen umfassenden Korngrößenbereich ziehen. In grob- und feinkörnigem Nickel bilden sich bei der zyklischen Verformung ermüdungstypische Versetzungsstrukturen, deren Abmessungen kaum von der Korngröße abhängen. Der Versetzungslaufweg in diesen Materialien ist wesentlich kleiner als die Kornabmessungen. Dementsprechend besteht höchstens ein schwacher Einfluss der Korngröße auf das sich bei der Wechselverformung einstellende Spannungsniveau. Bei mikro- und submikrokristallinem Nickel, wo der Versetzungslaufweg in der Größenordung der Kornabmessungen liegt, wird ein deutlicher Umschlag bei der Versetzungsmusterbildung und dem zyklischen Verformungsverhalten beobachtet. In diesem Korngrößenbereich entstehen entweder qualitativ andere (D<DS1=5µm) oder keine Versetzungsstrukturen (D<DS2=1µm) und das Spannungsniveau steigt mit sinkender Korngröße entsprechend einer HALL-PETCH-Beziehung.
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Klemm, Robert. "Zyklische Plastizität von mikro- und submikrokristallinem Nickel." Doctoral thesis, Technische Universität Dresden, 2003. https://tud.qucosa.de/id/qucosa%3A23831.
Full textAbstract:
Im Rahmen der vorliegenden Arbeit wurde der Einfluss der Korngröße und der Gefügestabilität auf die zyklische Plastizität von mikro- und submikrokristallinem Nickel, hergestellt durch ECAP und PED, untersucht. Zur Gefügecharakterisierung kamen verschiedene elektronenmikroskopische und röntgenographische Methoden zum Einsatz. Die Untersuchungen zur Gefügestabilität zeigten, dass (i) die Stabilität der Korn- und Substruktur bei der zyklischen Verformung empfindlich vom Gefüge im Ausgangszustand abhängt, (ii) generell die Tendenz zur Umwandlung der vorhandenen Substruktur in eine universelle ermüdungstypische Substruktur besteht, diese Transformation jedoch durch die lokale Gefügebeschaffenheit be- bzw. verhindert sein kann und (iii) zur Erklärung des Entfestigungsverhaltens der ECAP-Materialien sowohl die Transformation der Substruktur als auch die Vergröberung der Kornstruktur berücksichtigt werden müssen. Auf der Basis der Ergebnisse der vorliegenden Arbeit und unter Hinzunahme von Resultaten aus der Literatur lassen sich Schlussfolgerungen zum Einfluss der Korngröße auf die zyklische Plastizität in einem vier Größenordnungen umfassenden Korngrößenbereich ziehen. In grob- und feinkörnigem Nickel bilden sich bei der zyklischen Verformung ermüdungstypische Versetzungsstrukturen, deren Abmessungen kaum von der Korngröße abhängen. Der Versetzungslaufweg in diesen Materialien ist wesentlich kleiner als die Kornabmessungen. Dementsprechend besteht höchstens ein schwacher Einfluss der Korngröße auf das sich bei der Wechselverformung einstellende Spannungsniveau. Bei mikro- und submikrokristallinem Nickel, wo der Versetzungslaufweg in der Größenordung der Kornabmessungen liegt, wird ein deutlicher Umschlag bei der Versetzungsmusterbildung und dem zyklischen Verformungsverhalten beobachtet. In diesem Korngrößenbereich entstehen entweder qualitativ andere (D<DS1=5µm) oder keine Versetzungsstrukturen (D<DS2=1µm) und das Spannungsniveau steigt mit sinkender Korngröße entsprechend einer HALL-PETCH-Beziehung.
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Akrobetu, Richard K. "The Interplay of Surface Adsorbates and Cationic Intermixing in the 2D Electron Gas Properties of LAO-STO Heterointerfaces." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1491575404930072.
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Kottman, Michael Andrew. "Additive Manufacturing of Maraging 250 Steels for the Rejuvenation and Repurposing of Die Casting Tooling." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1416854466.
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Lu, Chi-Yuan, and 盧啟原. "Investigation of Electro-Optical Semiconductor GaSe on Different Substrates by Pulsed Laser Deposition." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/77303292707226405197.
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碩士國立交通大學
光電工程所
91
We have successfully fabricated GaSe thin films on different substrates. From (004) peak position and FWHM of XRD, we observe that quality of GaSe/Si(111) series is the best compared to GaSe/GaN and GaSe/Sapphire at the same thickness due to small lattice mismatch. We also find that c-axis length of GaSe thin films were stretched larger at initial stage of deposition and the increasing amount (c) are GaSe/Sapphire, GaSe/GaN and GaSe/Si(111) in order. The crystalline of GaSe thin films can also be evaluated by Raman Al’ mode which vibrates along c-axis and E’(LO) mode which vibrates perpendicular to the c-axis of GaSe. From the analysis of FWHM of A1’mode, the tendency is identical compared with XRD result. In addition, we also find that the A1’mode shift to lower frequency due to the c-axis length stretched larger which were presumed in accordance with ref[23]. From AFM analysis, the growth mode might be SK mode. The result is different from GaSe deposited by MBE system (layer by layer mode) which belong to VdWE. After the analysis of XRD, Raman spectra and AFM, we find that the behavior is unlike VdWE or quai-VdWE. Hence the lattice mismatch is an important parameter we must consider when we deposit GaSe thin films by pulsed laser deposition.
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"Laser pulse duration and electric field effects in the pulsed laser deposition of titanium and silicon carbides." Tulane University, 2007.
Find full textAbstract:
Experimental results of the pulsed laser ablation and thin film deposition of titanium carbide and silicon carbide by pulsed laser deposition (PLD) are presented. PLD takes place by evaporation of a target sample composed of the desired film material, ejection and transfer in the gas phase, and deposition onto a substrate. Films thus grown benefit from the kinetics of the laser generated plume as well as from the high ion flux at the substrate. A major impediment to the PLD process is the contamination of films by molten and/or solid material ejected during ablation. Experimental parameters determine which contaminant is produced. This work presents two methods designed for film improvement by incorporating an electric field to the process. The first technique diverted a portion of the ionic plume component away from the trajectories of large particulates also generated during the laser-target interaction. The second technique involved the generation of an electric discharge across the laser generated plasma prior to deposition. The current across the plasma/plume initiates collisions in the plume that effectively break down the solid contaminants. Three laser pulse durations were used for material evaporation, employing long nanosecond pulses (Nd:YLF, 10 mJ, 250 ns), short nanosecond pulses (Nd:YAG, ∼3.5 ns) and femtosecond pulses (Ti:Sapphire, ∼150 fs). Included are gas phase studies using mass spectrometry, Langmuir ion probes, and deposition monitors that allowed the relative ion yields as well as their kinetics to be measured. The deposits were examined topographically by scanning electron and atomic force microscopies (SEM and AFM, respectively), and chemically by X-ray photoelectron spectroscopy (XPS)acase@tulane.edu
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ALLEN and 許志宇. "The Study of CuInSe2 thin film by the pulse electro deposition." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/98115690491463341324.
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碩士吳鳳技術學院
光機電暨材料研究所
96
Abstract This study will use electro-depositing technique to add (Ethylene Diamine Tetraacetic Acid，EDTA) in chloride solution to electrodeposit CuInSe2 thin film on ITO electrode. This major study will to use on the current density, pH value and ion concentration effect on CuInSe2 thin film generation during the deposition. By the design of experiment to control and analysis each factor. Using electro-chemical method to analysis electro-deposition CuInSe2 thin films mechanism and thin film Stoichiometry; crystal grain size and crystal structure. In the CuInSe2 thin film composition analysis one could find the effect of the difference current density on thin film composition. The experimental result shows in addition, deposit current density influence to CIS thin film surface morphological very huge; At the same time the adding amount of EDTA makes up CIS compositions, the size of crystalline grain and surface shape looks also play an important role. This experiment using current density 0.125ASD get a better composition (Cu: In: Se=0.9:1.2:1.9).
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Jenderka, Marcus. "Pulsed Laser Deposition of Iridate and YBiO3 Thin Films." Doctoral thesis, 2016. https://ul.qucosa.de/id/qucosa%3A15345.
Full textAbstract:
Die vorliegende Arbeit befasst sich mit dem Dünnfilmwachstum der ternären Oxide Na2IrO3, Li2IrO3, Y2Ir2O7 und YBiO3. All diesen oxidischen Materialien ist gemein, dass sie Verwirklichungen sogenannter Topologischer Isolatoren oder Spin-Flüssigkeiten sein könnten. Diese neuartigen Materiezustände versprechen eine zukünftige Anwendung in der Quantencomputation, in magnetischen Speichern und in elektrischen Geräten mit geringer Leistungsaufnahme. Die Herstellung der hier gezeigten Dünnfilme ist daher ein erster Schritt zur Umsetzung dieser Anwendungen in der Zukunft. Alle Dünnfilme werden mittels gepulster Laserplasmaabscheidung auf verschiedenen einkristallinen Substraten hergestellt. Die strukturellen, optischen und elektrischen Eigenschaften der Filme werden mittels etablierter experimenteller Verfahren wie Röntgenbeugung, spektroskopischer Ellipsometrie und elektrischenWiderstandsmessungen untersucht.
Die strukturellen Eigenschaften von erstmalig in der Masterarbeit des Authors verwirklichten Na2IrO3-Dünnfilmen können durch Abscheidung einer ZnO-Zwischenschicht deutlich verbessert werden. Einkristalline Li2IrO3-Dünnfilme mit einer definierten Kristallausrichtung werden erstmalig hergestellt. Die Messung der dielektrischen Funktion gibt Einblick in elektronische Anregungen, die gut vergleichbar mit Li2IrO3-Einkristallen und verwandten Iridaten sind. Des Weiteren wird aus den Daten eine optische Energielücke von ungefähr 300 meV bestimmt. In Y2Ir2O7-Dünnfilmen wird eine mögliche (111)-Vorzugsorientierung in Wachstumsrichtung gefunden. Im Vergleich mit der chemischen Lösungsabscheidung zeigen die hier mittels gepulster Laserplasmaabscheidung hergestellten YBiO3-Dünnfilme eine definierte, biaxiale Kristallausrichtung in der Wachstumsebene bei einer deutlich höheren Schichtdicke. Über die gemessene dielektrische Funktion können eine direkte und indirekte Bandlücke bestimmt werden. Deren Größe gibt eine notwendige experimentelle Rückmeldung an theoretische Berechnungen der elektronischen Bandstruktur von YBiO3, welche zur Vorhersage der oben erwähnten, neuartigen Materiezuständen verwendet werden.
Nach einer Einleitung und Motivation dieser Arbeit gibt das zweite Kapitel einen Überblick über den gegenwärtigen Forschungsstand der hier untersuchten Materialien. Die folgenden zwei Kapitel beschreiben die Probenherstellung und die verwendeten experimentellen Untersuchungsmethoden. Anschließend werden für jedes Material einzeln die experimentellen Ergebnisse dieser Arbeit diskutiert. Die Arbeit schließt mit einer Zusammenfassung und einem Ausblick.The present thesis reports on the thin film growth of ternary oxides Na2IrO3, Li2IrO3, Y2Ir2O7 and YBiO3. All of these oxides are candidate materials for the so-called topological insulator and spin liquid, respectively. These states of matter promise future application in quantum computation, and in magnetic memory and low-power electronic devices. The realization of the thin films presented here, thus represents a first step towards these future device applications. All thin films are prepared by means of pulsed laser deposition on various single-crystalline substrates. Their structural, optical and electronic properties are investigated with established experimental methods such as X-ray diffraction, spectroscopic ellipsometry and resistivity measurements. The structural properties of Na2IrO3 thin films, that were previously realized in the author’s M. Sc. thesis for the first time, are improved significantly by deposition of an intermediate ZnO layer. Single-crystalline Li2IrO3 thin films are grown for the first time and exhibit a defined crystal orientation. Measurement of the dielectric function gives insight into electronic excitations that compare well with single crystal samples and related iridates. From the data, an optical energy gap of about 300 meV is obtained. For Y2Ir2O7 thin films, a possible (111) out-of-plane preferential crystal orientation is obtained. Compared to chemical solution deposition, the pulsed laser-deposited YBiO3 thin films presented here exhibit a biaxial in-plane crystal orientation up to a significantly larger film thickness. From the measured dielectric function, a direct and indirect band gap energy is determined. Their magnitude provides necessary experimental feedback for theoretical calculations of the electronic structure of YBiO3, which are used in the prediction of the novel states of matter mentioned above. After the introduction and motivation of this thesis, the second chapter reviews the current state of the science of the studied thin film materials. The following two chapters introduce the sample preparation and the employed experimental methods, respectively. Subsequently, the experimental results of this thesis are discussed for each material individually. The thesis concludes with a summary and an outlook.
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Chen, Kuang-Tze, and 陳光澤. "Electrochemical Study of Sodium Cobalt Oxide Electrode Prepared by Pulsed Laser Deposition." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/44333460642576426168.
Full textAbstract:
碩士國立暨南國際大學
應用化學系
99
In this research, layered sodium cobalt oxide thin film has deposited on two conducting substrates by Pulsed Laser Deposition (PLD). The grown Na0.62CoO2 thin film typically has hexagonal structure with R-3m space group. Problems of lattice mismatch between growth layer and conducting substrate have successfully solved. Crystalline thin film electrode can be produced by adjusting power of laser, substrate temperature and deposition time. The grown thin film electrode exhibits good quality and repeatability for electrochemical experiment. Variations of sodium content and redox reaction on the Na0.62CoO2 have been studied by changing the applied potential on thin film electrode. Ion exchanged of Ag+(aq) for Na+(aq) forms the silver cobalt oxide (AgxCoO2) thin film electrode. The potential dependence of AgxCoO2 stoichiometry is found and demonstrated in this work.
21
陳世銘. "Preparation and electric characterization of AZO:N/p-Si heterostructure by pulse laser deposition." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/56997482774795463897.
Full text
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Hsu, Wen-Chang, and 許文昌. "A study of gas diffusion layers of Proton Exchange Membrane Fuel Cells modify by pulse electro-deposition." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/72953168921091063754.
Full textAbstract:
碩士逢甲大學
材料科學所
97
In the proton exchange membrane fuel cell (PEMFC), the catalyst layer is the most expensive in all key materials. In order to decrease the cost of fuel cell, it is necessary to use a new electrochemical deposition method to prepare nanoparticle on gas diffusion layers. This experiment was conducted by using pulse electrochemistry deposition method to prepare nano size of pt particle on carbon black of gas diffusion layer for proton exchange membrane fuel cell. The catalyst layer was prepared in 1M H2SO4 +0.002M H2PtCl6 by controlling varying charge time of pulse electro-deposition. After inserting Nafion 117 membrane between two gas diffusion layers and hot pressing the electrodes at 140℃for 90s, the membrane electrode assembly were made for PEMFC testing The Pt loading was between 0.0024 mg/cm2 and 0.0116 mg/cm2 while characterizing the shape and size of the Pt nanoparticles by field-emission scanning electron microscopy and analyzing the amounts of platinum loading by inductively coupled plasma optima optical emission spectrometer. In addition, the platinum crystallization was determined by X-ray powder diffraction analyses. Moreover, the adsorption and desorption reactions of hydrogen with platinum catalysts were analyzed via cyclic voltammograms. A peak current density of 0.0249 A/cm2 could be reached at pulse electro-deposition charge time of 3200s.
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Myers, Michelle Anne. "Processing and Characterization of P-Type Doped Zinc Oxide Thin Films." Thesis, 2013. http://hdl.handle.net/1969.1/149354.
Full textAbstract:
Applications of zinc oxide (ZnO) for optoelectronic devices, including light emitting diodes, semiconductor lasers, and solar cells have not yet been realized due to the lack of high-quality p-type ZnO. In the research presented herein, pulsed laser deposition is employed to grow Ag-doped ZnO thin films, which are characterized in an attempt to understand the ability of Ag to act as a p-type dopant. By correlating the effects of the substrate temperature, oxygen pressure, and laser energy on the electrical and microstructural properties of Ag-doped ZnO films grown on c-cut sapphire substrates, p-type conductivity is achieved under elevated substrate temperatures. Characteristic stacking fault features have been continuously observed by transmission electron microscopy in all of the p-type films. Photoluminescence studies on n-type and p-type Ag-doped ZnO thin films demonstrate the role of stacking faults in determining the conductivity of the films. Exciton emission attributed to basal plane stacking faults suggests that the acceptor impurities are localized nearby the stacking faults in the n-type films. The photoluminescence investigation provides a correlation between microstructural characteristics and electrical properties of Ag- doped ZnO thin films; a link that enables further understanding of the doping nature of Ag impurities in ZnO. Under optimized deposition conditions, various substrates are investigated as potential candidates for ZnO thin film growth, including r -cut sapphire, quartz, and amorphous glass. Electrical results indicated that despite narrow conditions for obtaining p-type conductivity at a given substrate temperature, flexibility in substrate choice enables improved electrical properties.
In parallel, N+-ion implantation at elevated temperatures is explored as an alternative approach to achieve p-type ZnO. The ion implantation fluence and temperature have been optimized to achieve p-type conductivity. Transmission electron microscopy reveals that characteristic stacking fault features are present throughout the p-type films, however in n-type N-doped films high-density defect clusters are observed. These results suggest that the temperature under which ion implantation is performed plays a critical role in determining the amount of dynamic defect re- combination that can take place, as well as defect cluster formation processes. Ion implantation at elevated temperatures is shown to be an effective method to introduce increased concentrations of p-type N dopants while reducing the amount of stable post-implantation disorder.
Finally, the fabrication and properties of p-type Ag-doped ZnO/n-type ZnO and p-type N-doped ZnO/n-type ZnO thin film junctions were reported. For the N-doped sample, a rectifying behavior was observed in the I-V curve, consistent with N-doped ZnO being p-type and forming a p-n junction. The turn-on voltage of the device was ∼2.3 V under forward bias. The Ag-doped samples did not result in rectifying behavior as a result of conversion of the p-type layer to n-type behavior under the n- type layer deposition conditions. The systematic studies in this dissertation provide possible routes to grow p-type Ag-doped ZnO films and in-situ thermal activation of N-implanted dopant ions, to overcome the growth temperature limits, and to push one step closer to the future integration of ZnO-based devices.
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Araujo, Roy A. "Metal Nitride Diffusion Barriers for Copper Interconnects." 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2008-12-159.
Full textAbstract:
Advancements in the semiconductor industry require new materials with
improved performance. With the introduction of copper as the interconnect material for
integrated circuits, efficient diffusion barriers are required to prevent the diffusion of
copper into silicon, which is primarily through grain boundaries. This dissertation
reports the processing of high quality stoichiometric thin films of TiN, TaN and HfN,
and studies their Cu diffusion barrier properties.
Epitaxial metastable cubic TaN (B1-NaCl) thin films were grown on Si(001)
using an ultra-thin TiN (B1-NaCl) seed layer which was as thin as 1 nm. The TiN/TaN
stacks were deposited by Pulsed Laser Deposition (PLD), with the TiN thickness
systematically reduced from 15 to 1 nm. Microstructural studies included X-ray
diffraction (XRD), transmission electron microscopy (TEM) and high resolution TEM
(HRTEM). Preliminary Cu diffusion experiments showed that the TiN seed layer
thickness had little or no obvious effect on the overall microstructure and the diffusion
barrier properties of the TaN/TiN stacks. Epitaxial and highly textured cubic HfN (B1-NaCl) thin films (~100 nm) were
deposited on MgO(001) and Si(001) using PLD. Low resistivities (~40 mu omega-cm) were
measured with a four point probe (FPP). Microstructural characterizations included
XRD, TEM, and HRTEM. Preliminary Cu diffusion tests demonstrated good diffusion
barrier properties, suggesting that HfN is a promising candidate for Cu diffusion
barriers.
Cubic HfN (B1-NaCl) thin films were grown epitaxially on Si(001) substrates by
using a TiN (B1-NaCl) buffer layer as thin as ~10 nm. The HfN/TiN stacks were
deposited by PLD with an overall thickness less than 60 nm. Detailed microstructural
characterizations included XRD, TEM, and HRTEM. The electrical resistivity measured
by FPP was as low as 70 mu omega-cm. Preliminary copper diffusion tests showed good
diffusion barrier properties with a diffusion depth of 2~3 nm after vacuum annealing at
500 degrees C for 30 minutes.
Additional samples with Cu deposited on top of the cubic HfN/TiN/Si(001) were
vacuum annealed at 500 degrees C, 600 degrees C and 650 degrees C for 30 minutes. The diffusivity of copper
in the epitaxial stack was investigated using HRTEM. The measured diffusion depths,
2 Dt , were 3, 4 and 5 nm at 500 degrees C, 600 degrees C and 650 degrees C respectively. Finally, the
diffusivity of Cu into epitaxial HfN was determined to be D=D0 exp(-Q/kT)cm2s-1 with D0=2.3x10-14cm2s-1 and Q=0.52eV.
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Ku, Chun-Wei, and 古竣偉. "Fabricating Gallium Nitride Epilayer on Zinc Oxide Buffer Layer via Pulsed Laser Deposition System and Opto-electric Properties Analysis." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/h2y3hz.
Full textAbstract:
碩士國立臺灣大學
光電工程學研究所
101
The study of this thesis is to investigate the hydrothermal method for growing high-quality zinc oxide thin film and the homemade pulsed laser deposition system for fabricating high-quality gallium nitride thin film on zinc oxide buffer layer. First, we introduce to obtain high-quality ZnO thin film via hydrothermal method. After that, we use homemade PLD to fabricate high-quality GaN thin film on ZnO buffer layer, and then the effect of nitrogen pressure on properties of GaN thin film is also investigated. In the study of growing high-quality ZnO thin film, the ZnO thin film was successfully fabricated on the p-type GaN epilayer via the hydrothermal method. We successfully used chemical kinetics to simulate the relationship of the growth concentration and the growth time, thus determining the optimal conditions to fabricate the ZnO thin film on a p-type GaN epilayer. Subsequently, we used AFM, EDS, XRD, and Hall measurements to analyze the characteristics of the ZnO thin film. The roughness of the ZnO thin film is determined by AFM to be about 5.46 nm, where there is no other impurity detected in the EDS spectrum. Besides, under the growth temperature of 90°C and the growth concentration of 100mM for 6 hours, the XRD FWHM of ZnO (0001) shows =0.1682°, which is neck and neck with that fabricated by PLD. This means that it is possible to fabricate good quality ZnO thin film via a low cost hydrothermal method and it can be applied in many fields. We have further fabricated n-ZnO layer onto p-GaN layer to fabricate hetero-junction LEDs and successfully achieved a rectifying I-V curve and light emission from current injection. The EL emission of the LED is dominated in the ZnO layer. All results show that the ZnO thin film fabricated by the low-cost hydrothermal method has good potential for possible applications in the industry of light-emitting diodes and take the place of GaN for the material of emitting layer. Next, we use homemade pulsed laser deposition system to epitaxy high-quality gallium nitride thin film on zinc oxide buffer layer. During the deposition process, the high energy plume collides or scatters with nitrogen in atmosphere. This phenomenon greatly affected the crystalline of GaN thin film. The experimental data shows that the properties of GaN thin film fabricate under deposition condition substrate heating temperature 900 oC, laser energy 600mJ/pulsed, 7 Hz laser repetition frequency, and operating nitrogen pressure at 1x10-2 torr are very good. The UV-visible spectrum shows that average transmittance in the visible range is 87 % , and the EDS spectrum reveals that the element ratio of Ga and N is approach to 1:1. The XRD FWHM of the GaN (0002) thin film shows =0.293°, which is neck and neck with that deposited by MOCVD. Furthermore, the surface roughness of the GaN thin film is only 1.6312 nm. It means that this high-quality GaN thin film is also fairly flat.
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"Study of indium tin oxide (ITO) thin films prepared by pulsed DC facing-target Sputtering (FTS)." 2000. http://library.cuhk.edu.hk/record=b5890427.
Full textAbstract:
by Fung Chi Keung = 採用脈衝直流電源對靶濺射技術製備銦錫氧化物薄膜的硏究 / 馮志強.Thesis (M.Phil.)--Chinese University of Hong Kong, 2000.
Includes bibliographical references.
Text in English; abstracts in English and Chinese.
by Fung Chi Keung = Cai yong mai chong zhi liu dian yuan dui ba jian she ji shu zhi bei yin xi yang hua wu bo mo de yan jiu / Feng Zhiqiang.
Acknowledgements --- p.i
Abstract --- p.ii
論文摘要 --- p.iii
Table of contents --- p.iv
List of figures --- p.viii
List of tables --- p.xii
Chapter Chapter 1 --- Introduction --- p.1-1
Chapter 1.1 --- Genesis --- p.1-1
Chapter 1.2 --- Aims and Objectives --- p.1-1
Chapter 1.3 --- Layout of Thesis --- p.1-3
References --- p.1-4
Chapter Chapter 2 --- Literature Review --- p.2-1
Chapter 2.1 --- Introduction to transparent conducting oxides (TCOs) --- p.2-1
Chapter 2.2 --- Indium tin oxide (ITO) --- p.2-2
Chapter 2.2.1 --- Use of ITO --- p.2-2
Chapter 2.2.2 --- Structure and properties of ITO --- p.2-3
Chapter 2.3 --- Properties of ITO films deposited by different growth techniques --- p.2-8
Chapter 2.3.1 --- Sputtering --- p.2-9
Chapter 2.3.2 --- Vacuum evaporation --- p.2-11
Chapter 2.3.3 --- Spray pyrolysis --- p.2-11
Chapter 2.3.4 --- Chemical vapor deposition (CVD) --- p.2-12
Chapter 2.3.5 --- Reactive ion plating --- p.2-12
Chapter 2.4 --- Contradictions in existing literature --- p.2-13
References --- p.2-15
Chapter Chapter 3 --- Thin Film Fabrication and Process --- p.3-1
Chapter 3.1 --- Facing-target sputtering (FTS) --- p.3-1
Chapter 3.2 --- Asymmetric bipolar pulsed DC power source --- p.3-3
Chapter 3.2.1 --- Target poisoning --- p.3-3
Chapter 3.2.2 --- Preferential sputtering --- p.3-4
Chapter 3.2.3 --- Discussion --- p.3-4
Chapter 3.3 --- Substrates --- p.3-6
Chapter 3.3.1 --- Microscopic glass --- p.3-7
Chapter 3.3.2 --- Corning 7059 glass --- p.3-8
Chapter 3.3.3 --- Epitaxial growth --- p.3-8
Chapter 3.3.3.1 --- Epitaxial lattice matching --- p.3-8
Chapter 3.3.3.2 --- Yttrium stabilized zirconia (YSZ) --- p.3-9
Chapter 3.3.3.3 --- Sapphire --- p.3-9
Chapter 3.3.3.4 --- Silicon wafer --- p.3-11
Chapter 3.3.4 --- Substrate cleaning --- p.3-11
Chapter 3.4 --- Targets for the reactive sputtering of ITO films --- p.3-13
Chapter 3.4.1 --- Indium Tin Oxide target (90wt% ln203 : 10wt% Sn04) --- p.3-14
Chapter 3.4.2 --- Indium Tin alloy target (90wt% In : 10wt% Sn) --- p.3-14
Chapter 3.5 --- Deposition conditions --- p.3-16
Chapter 3.5.1 --- Sputter atmosphere --- p.3-16
Chapter 3.5.2 --- Deposition pressure --- p.3-16
Chapter 3.5.3 --- Deposition power --- p.3-17
Chapter 3.5.4 --- Target to substrate distance --- p.3-17
Chapter 3.5.5 --- Pulse frequency and pulse width --- p.3-17
Chapter 3.6 --- Deposition --- p.3-17
References --- p.3-19
Chapter Chapter 4 --- Measurement and Analysis Techniques --- p.4-1
Chapter 4.1 --- Resistivity measurement --- p.4-1
Chapter 4.2 --- "Transmittance, reflectivity and absorption measurements" --- p.4-3
Chapter 4.3 --- Thickness measurement --- p.4-4
Chapter 4.4 --- "Crystal structure, surface morphology and roughness measurements" --- p.4-4
Chapter 4.5 --- Photolithography --- p.4-7
Chapter 4.6 --- Hall effect measurements --- p.4-8
References --- p.4-10
Chapter Chapter 5 --- Experimental results and discussions --- p.5-1
Chapter 5.1 --- Effect of O2 partial pressure --- p.5-1
Chapter 5.1.1 --- Deposition rate --- p.5-2
Chapter 5.1.2 --- Electrical and optical properties --- p.5-4
Chapter 5.1.3 --- Structure and orientation --- p.5-16
Chapter 5.1.4 --- Surface morphology and roughness --- p.5-22
Chapter 5.1.5 --- Conclusion --- p.5-29
Chapter 5.2 --- Effect of substrate temperature --- p.5-29
Chapter 5.2.1 --- Electrical and optical properties --- p.5-29
Chapter 5.2.2 --- Structure and orientation --- p.5-44
Chapter 5.2.3 --- Surface morphology and roughness --- p.5-49
Chapter 5.2.4 --- Conclusion --- p.5-54
Chapter 5.3 --- Effect of vacuum annealing --- p.5-54
Chapter 5.3.1 --- Electrical and optical properties --- p.5-54
Chapter 5.3.2 --- Conclusion --- p.5-59
Chapter 5.4 --- Effect of different substrates --- p.5-59
Chapter 5.4.1 --- Comparison of heteroepitaxial and polycrystalline ITO films --- p.5-60
Chapter 5.4.2 --- Conclusion --- p.5-63
Chapter 5.5 --- Effect of film thickness --- p.5-64
Chapter 5.5.1 --- Film thickness calibration --- p.5-64
Chapter 5.5.2 --- Electrical properties --- p.5-64
Chapter 5.5.3 --- Conclusion --- p.5-67
Chapter 5.6 --- Effect of deposition pressure --- p.5-68
Chapter 5.6.1 --- Deposition rate --- p.5-68
Chapter 5.6.2 --- Electrical properties --- p.5-70
Chapter 5.6.3 --- Conclusion --- p.5-70
Chapter 5.7 --- Effect of target pre-conditioning --- p.5-72
Chapter 5.8 --- Conclusion --- p.5-72
References --- p.5-74
Chapter Chapter 6 --- Further works --- p.6-1
Appendix I
27
Wu, Bo-Hua, and 吳柏樺. "Study of the dye-sensitized solar cells using ZnO/TiO2 core-shelled electrode fabricated by pulse electrochemical deposition of TiO2 on ZnO." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/c57eb8.
Full textAbstract:
碩士國立東華大學
材料科學與工程學系
102
In this study, we coated titanium oxide on the surface of the ZnO particles to form a composite core-shelled structure as an anode for the dye-sensitized solar cells. The solar cell efficiency is successfully enhanced from 1.19% to 1.48% after titanium coating. The efficiency enhancement is accomplished, using titanium di-sulfate solution (Ti(SO4)2) as electrolyte, through the pulsed electrochemical deposition method, which provide appropriate control of thickness of the titanium oxide film that can be coated on the entire interior surface of a mesoporous ZnO film. We found the applied voltage has significant effect on titanium oxide film coated on the ZnO surface by XPS analysis. Under negative bias, the titanium coating rate increases, and the Ti3+ increases relative to Ti4+, with the amount of the applied voltage. Under positive bias, the Jsc increases with the amount of voltage, either due to the modification on the mesoporous surface by acid ligands or by the positive bias itself that turns Ti3+ into Ti4+. We found two most important factors that controls the solar cell efficiency through titanium oxide coating, which are oxygen vacancy (Vo) and film thickness of titanium oxide. The oxygen vacancy is further distinguished into the oxygen vacancy at the ZnO/TiO2 interface, and the oxygen vacancy on the surface of the coated titanium oxide film. We confirmed that the presence of oxygen vacancy at the ZnO/TiO2 interface helps the electronic conduction of the electrode and that the presence of the oxygen vacancy on the surface of the coated titanium oxide film promotes the electron recombination on the titanium oxide surface. As a consequence, the enhancement of the solar cell efficiency should be achieved through, on one hand, the preservation of oxygen vacancy at the ZnO/TiO2 interface and, on the other hand, suppression of the oxygen vacancy on the surface of the coated titanium oxide film. The increase of film thickness of titanium oxide suppresses the electron recombination at the titanium oxide surface, however, at the expense of compromising electronic conduction of the electrode. As a consequence, the thickness should be optimized to achieve highest efficiency of the solar cells. Considering both Vo and thickness factors, we are able to find a titanium oxide coating recipe that promotes the solar cell efficiency. We first coat a titanium oxide film with parameters that contains adequate amount of Ti3+, to assure the conduction of the electron at the ZnO/TiO2 interface. Next we proceed the coating using the same parameters until the targeted thickness is achieved. Finally we coat a thin layer of titanium oxide using parameters denoted as 1d5r to suppress the surface electron recombination as a result of reduced amount of Ti3+ in this coating layer using coating parameters of 1d5r. The reported efficiency enhancement to 1.48% is thus achieved.