We investigate some of the mechanical design factors of wafers and the effect on strength. Thin, solid, pre-stressed films are proposed as a means to improve the bulk mechanical properties of a wafer. Three-point bending was used to evaluate the laser scribe density and chemical processing effect on wafer strength. Drop and strike tests were employed to investigate the edge bevel profile effect on the mechanical properties of the wafer. To characterize the effect of thin films on strength, one-micron ceramic films were deposited on wafers using PECVD. Coated samples were prepared by cleaving and were tested using four-point bending. Film adhesion was characterized by notched four-point bending. RBS and FTIR were used to obtain film chemistry, and nanoindentation was used to investigate thin film mechanical properties. A stress measurement gauge characterized residual film stress. Mechanical properties of the wafers correlated to the residual stress in the film.

京都大学 / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第21884号 / エネ博第385号 / 新制||エネ||75(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻 / (主査)教授 佐川 尚, 教授 萩原 理加, 教授 野平 俊之 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DGAM

Conversion material electrodes such as FeF2 possess the potential to deliver transformative improvements in lithium ion battery performance because they permit a reversible change of more than one Li-ion per 3d metal cation. They outperform current state of the art intercalation cathodes such as LiCoO2, which have volumetric and gravimetric energy densities that are intrinsically limited by single electron transfer. Current studies focus on composite electrodes that are formed by mixing with carbon (FeF2-C), wherein the carbon is expected to act as a binder to support the matrix and facilitate electronic conduction. These binders complicate the understanding of the electrode-electrolyte interface (SEI) passivation layer growth, of Li agglomeration, of ion and electron transport, and of the basic phase transformation processes under electrochemical cycling. This research uses thin-films as a model platform for obtaining basic understanding to the structural and chemical foundations of the phase conversion processes. Thin film cathodes are free of the binders used in nanocomposite structures and may potentially provide direct basic insight to the evolution of the SEI passivation layer, electron and ion transport, and the electrochemical behavior of true complex phases. The present work consisted of three main tasks (1) Development of optimized processes to deposit FeF2 and LiPON thin-films with the required phase purity and microstructure; (2) Understanding their electron and ion transport properties and; (3) Obtaining insight to the correlation between structure and capacity in thin-film microbatteries with FeF2 thin-film cathode and LiPON thin-film solid electrolyte. Optimized pulsed laser deposition (PLD) growth produced polycrystalline FeF2 films with excellent phase purity and P42/mnm crystallographic symmetry. A schematic band diagram was deduced using a combination of UPS, XPS and UV-Vis spectroscopies. Room temperature Hall measurements reveal that as-deposited FeF2 is n-type with an electron mobility of 0.33 cm2/V.s and a resistivity was 0.255 Ω.cm. The LiPON films were deposited by reactive sputtering in nitrogen, and the results indicate that the ionic conductivity is dependent on the amount of nitrogen incorporated into the film during processing. The highest ionic conductivity obtained was 1.431.9E-6 Scm-1 and corresponded to a chemical composition of Li1.9PO3.3N.21. FeF2/LiPON thin films microbatteries were assembled using a 2032 coin cell configuration and subjected to Galvanostatic cycling. HRTEM and EELS spectroscopy where performed across the FeF2/LiPON interface of samples cycled once 15 times in their lithiated and delithiated states to understand the relationship between microstructural evolution and capacity. The EELS measurements provided evidence of a three-phase conversion reaction over the first discharge described by FeF2 +2e-+2Li+↔Fe +LiF, and of incomplete reconversion back to FeF2 after the 1st cycle resulting in new Fe0 and LiF phases in delithiated samples. This incomplete conversion results in (a) a smaller phase fraction of FeF2 participating in the conversion process subsequently and (b) the formation of LiF which is resistive to both electron and ion transport. This results in the observed drastic drop in capacity after the1st cycle. More study to understand the reconversion reaction pathways is required to fully exploit the potential of FeF2 and other conversion materials as cathodes in Li ion batteries.

No description available.

A modified ascending thin layer chromatographic technique has been developed which resolves the major phospholipid and neutral lipid classes of five common fluids and tissues. A one-half milliliter sample is extracted with n-butanol:diisopropylether (40:60 by volume, cholesteryl acetate = 100 ng/ul) for thirty minutes and the organic phase is spotted onto a thin layer chromatography plate and carried through three successive chromatographic developments. The lipids are then visualized either by charring with ammonium bisulfate or staining with phosphomolybdic acid. The use of cholesteryl acetate as an internal standard enables quantitation of the phospholipids and neutral lipid classes. This method may be a very valuable, new technique for research and clinical laboratories.

Silicon phthalocyanines (R₂-SiPcs) are an emerging class of high-performance n-type or ambipolar organic semiconductors which have found application in organic electronic devices, including organic thin-film transistors (OTFTs), organic photovoltaics (OPVs) and organic light-emitting diodes (OLEDs). Owing to their tetravalent silicon metal centre, R₂-SiPcs can be substituted with a range of axial ligands including phenols, carboxylic acids, and silanes to tune their intermolecular interactions, optical properties, electronic properties and solubility. While early reports of R₂-SiPcs have demonstrated promising results, the relationship between their structure and performance in OTFTs is poorly understood. Additionally, many OTFTs with R₂-SiPcs as semiconductor only demonstrate n-type behaviour under inert atmospheres due to their shallow lowest unoccupied orbital level below -4.1 eV making them susceptible to electron trapping by moisture and oxygen. This thesis presents developments in both the understanding of how R₂-SiPc structure influences performance, device engineering and exploration of these materials in ammonia sensors. First, I develop of structure-property relationships for a catalogue of fifteen R₂-SiPcs integrated into OTFTs including eleven materials used in OTFTs for the first time. I then explore the influence of dielectric surface chemistry on the texture of R₂-SiPc films and their resulting performance in OTFTs using silane self-assembled monolayers and para-sexiphenyl to understand the weak epitaxial growth behaviour of this class of materials. Next, I report eight novel peripherally fluorinated and axially substituted silicon phthalocyanines (R₂-FₓSiPcs) to investigate the influence of peripheral and axial fluorination on air-stable electron transport and determine the threshold for achieving air-stable n-type OTFTs. Finally, I integrate R₂-FₓSiPcs into organic heterojunction ammonia gas sensors to understand the influence of peripheral fluorination on the majority charge carrier in this device architecture.

No description available.

<p dir="ltr">Multiferroics, which exhibit multiple ferroic orderings within a single material system, have substantial potential for applications in sensors, transducers, memory devices, and energy harvesters. However, the development of single-phase multiferroics that demonstrate roomtemperature properties remains limited by inherent contradictions in d-orbital occupancy between magnetic and ferroelectric materials. This dissertation focuses on addressing this challenge through the exploration of a novel bismuth-based, single-phase multiferroic thin film that features an exotic layered supercell (LSC) structure and displays multiferroic properties at room temperature. The primary aim is to deepen the understanding of LSC materials and advance their applications in practical devices. The dissertation is structured as follows: It begins with an introduction to the fundamental concepts of multiferroics, including their classifications and applications, the specific characteristics and growth mechanism of LSC materials, and other relevant background knowledge. This is followed by a detailed description of the experimental techniques employed. The core of this dissertation comprises four chapters that present a comprehensive study of LSC materials. The first chapter discusses a nanocomposite system combining an LSC material, Bi1.25AlMnO3.25, with Au nanoparticles (NPs), highlighting its tunable microstructure and multifunctional properties influenced by growth temperature. The second chapter explores the integration of Bi2NiMnO6 on a flexible mica substrate, demonstrating the potential of LSC materials for use in flexible electronics, with performance maintained across various bending conditions. The third chapter details the development of freestanding LSC thin films by utilizing a water-soluble sacrificial layer, which are shown to preserve their microstructure and properties after being transferred onto a silicon substrate. Building on this, the fourth chapter investigates the reuse of recycled SrTiO3 substrates for subsequent thin film growth, examining changes in surface strain states and chemistry to guide sustainable practices in complex oxide thin film processing. In summary, this dissertation presents an extensive examination of LSC multiferroics, revealing their significant promise for multifunctional applications and integration into flexible and silicon-based electronics. Additionally, the work explores sustainable methods for substrate reuse, contributing further to the field of material sciences.<br></p>

In this dissertation M02C and diamond films deposited by electrophoresis on flat Mo foils and tips have been studied to determine their suitability as field emission tips.

Surface force measurements previously conducted with thiolated gold surfaces showed a decrease in excess film entropy (£GSf), suggesting that hydrophobic force originates from changes in the structure of the medium (water) confined between hydrophobic surfaces. As a follow-up to the previous study, surface force measurements have been conducted using an atomic force microscope (AFM) with hydrophobic silica surfaces at temperatures in the range of 10 to 40¢XC. The silica sphere and silica plate were treated by both chemisorption of octadecyltrichlorosilane (OTS) and physical adsorption of octadecyltrimethylammonium chloride (C18TACl). A thermodynamic analysis of the results show similar results for both of the samples, that both ""Sf and excess film enthalpy ("Hf) become more negative with decreasing thickness of the water layer between the hydrophobic surfaces and decreasing temperature. |"Hf | > |T"Sf| represents a necessary condition for the excess free energy change ("Gf ) to be negative and the hydrophobic interaction to be attractive. Thus, the results obtained with both the silylated and C18TACl-adosrbed silica surfaces in the present work and the thiolated gold suefaces reported before show hydrophobic forces originate from structural changes in the medium. Thermodynamic analysis of SFA force measurements obtained at various temperatures revealed that "Sf were much more negative in the shorter hydrophobic force ranges than in the longer ranges, indicating a more significant degree of structuring in the water film when the two hydrophobic surfaces are closer together. It is believed that the water molecules in the thin liquid films (TLFs) of water form clusters as a means to reduce their free energy when they cannot form H-bonds to neighboring hydrophobic surfaces. Dissolved gas molecules should enhance the stability of structured cluster due to the van der Waals force between the entrapped gas molecules and the surrounding water molecules1, which may enhance the strength of the hydrophobic force. Weaker long-range attractive forces detected in degassed water than in air-equilibrated water was found in the present work by means of AFM force measurements, supporting the effect of dissolved gas on the structuring of water. At last, temperature effects on hydrophobic interactions measured in ethanol and the thermodynamic analysis revealed similar results as those found in water, indicating that the hydrophobic force originates from H-bond propagated structuring in the mediums. / Ph. D.