Global ETD Search

11	Determination of the Fe-Cr-Ni and Fe-Cr-Mo Phase Diagramsat Intermediate Temperatures using a NovelDual-Anneal Diffusion-Multiple Approach Cao, Siwei January 2013 (has links) No description available. Materials Science Fe-Cr-Ni Fe-Cr-Mo Dual-Anneal Diffusion Multiple ternary phase diagram
12	NOVEL SELF-ASSEMBLY OF CRYSTALLINE MgAl2O4 NANOSTRUCTURES PROMOTED BY ANNEALING A GOLD OVERLAYER ON A (111) MgAl2O4 SUBSTRATE Majdi, Tahereh 15 January 2015 (has links) <p>The solid state dewetting characteristics of thin gold films sputtered onto (111) MgAl<sub>2</sub>O<sub>4</sub> substrates were investigated. Prior research done on this system reported discovering the self-assembly of intricately shaped nanostructures, consisting of a faceted sphere lying above a truncated triangular pyramid, formed by applying a specific two stage heating profile. The current work was done to provide deeper insight on the odd self-assembly observed in this system. The results indicate that the intricate structures are not purely gold self-assemblies, but in fact consist of three distinct materials: a single crystal or polycrystalline gold faceted sphere, separated by an interfacial boundary layer, from above a crystalline MgAl<sub>2</sub>O<sub>4</sub> necking structure that spontaneously developed from the initially flat substrate. The boundary separating these two assemblies is confined within a thin, sharp region of a third material consisting of Au and O elements. The composition and crystalline nature of the individual nanostructures were studied using high angle annular dark-field imaging, energy dispersive X-ray spectroscopy, and electron energy loss spectroscopy employed by a high resolution transmission electron microscope. Two-dimensional X-ray diffraction texture analysis revealed that the gold nanoparticles are crystalline, with majority of the maximum intensity signal corresponding to the epitaxial alignment of the gold nanoparticles with the substrate. The MgAl<sub>2</sub>O<sub>4</sub> necking structures were found to be sensitive to both the annealing profile, and the thickness of the gold film, which influenced the distinguishable presence, size, and footprint of the MgAl<sub>2</sub>O<sub>4</sub> nanostructures. Atomic force microscopy and scanning electron microscopy results were consistent with the gold overlayer playing an essential role in the self-assembly of MgAl<sub>2</sub>O<sub>4</sub> nanostructures. While the fundamental mechanisms that govern this phenomenon are not entirely clear, the presented results do provide insight into the role of interfaces in heteroepitaxial systems, especially the self-assembly of crystalline nanostructures from a previously stable substrate.</p> / Master of Applied Science (MASc) gold MgAl2O4 spinel nano novel anneal self-assembly Nanoscience and Nanotechnology Nanoscience and Nanotechnology
13	The Effect of Processing Conditions on the Energetic Diagram of CdTe Thin Films Studied by Photoluminescence Collins, Shamara P. 02 July 2018 (has links) The photovoltaic properties of CdTe-based thin films depend on recombination levels formed in the CdTe layer and at the heterojunction. The localized states are resultant of structural defects (metal sublattice, chalcogen sublattice, interstitial), controlled doping, deposition process, and/or post-deposition annealing. The photoluminescence study of CdTe thin films, from both the bulk and heterojunction, can reveal radiative states due to different defects or impurities. Identification of defects allows for potential explanation of their roles and influence on solar cell performance. A thorough understanding of the material properties responsible for solar cell performance is critical in further advancing the efficiency of devices. The presented work is a systematic investigation using photoluminescence to study CdTe thin films with varying deposition processes. The thin (polycrystalline) films explored in this study were deposited by either the elemental vapor transport technique (EVT) or close spaced sublimation (CSS). Two device architectures were investigated, the typical CdTe/CdS device and the CdSeXTe1-X (CST) alloy device. Post-deposition annealing processes were either laser or thermal. The study of the CdTe thin films is grouped in three general categories: (a) EVT films: Intrinsic and Extrinsic (Group V: Sb and P), (b) CST alloys, and (c) Post-deposition Laser Annealed (LA) films. The main goal of this dissertation is to understand the influence of fabrication procedures (deposition conditions, post deposition thermal and chemical treatments, added impurities, and device architecture) on the defect structure of the CdTe thin films. The behavior of the photoluminescence (PL), studied as a function of the measurement temperature and excitation intensity, provides insight to the mechanism causing the radiative recombination levels. Analysis of the PL spectra for CdTe films with intrinsic doping demonstrated stoichiometric control of native defects for both the Cd- and Te-rich conditions. PL spectra of CdTe:Sb films showed unique Sb-related bands. Also, impurity-related defects were identified in the CdTe:P spectra. Spectral analysis support the need for optimization of dopant concentration. The effects of selenium (Se) thickness and post-deposition processing on the formation of CST alloy were demonstrated in the changing PL spectra. The native defects (and complexes) identified in films with thermal anneal processing were the same as those identified in films with laser anneal post-deposition processing. The PL data were collected and other characterization techniques were used to support the defect assignments. A repository of material properties, which include the recombination levels along with structural defect assignment for each of the CdTe deposition processes, is provided. This project will lend the solar cell community information on CdTe defects for different processing conditions, ultimately influencing the fabrication of improved solar cells. Defects Doping Elemental Vapor Transport (EVT) Laser anneal Se profiles Materials Science and Engineering Oil, Gas, and Energy Other Physics
14	Assembly of colloidal nanocrystals into phospholipid structures and photothermal materials Rasch, Michael 12 November 2013 (has links) There has been growing interest in developing colloidal metal and semiconductor nanocrystals as biomedical imaging contrast agents and therapeutics, since light excitation can cause the nanocrystals to fluoresce or heat up. Recent advances in synthetic chemistry produced fluorescent 2-4 nm diameter silicon and 1-2 nm diaemeter CuInSSe nanocrystals, as well as 16 nm diameter copper selenide (Cu₂₋[subscript x]Se) nanocrystals exhibiting strong absorbance of near infrared light suitable for biomedical applications. However, the syntheses yield nanocrystals that are stabilized by an adsorbed layer of hydrocarbons, making the nanocrystals hydrophobic and non-dispersible in aqueous solution. Encapsulating these nanocrystals in amphiphilic polymer micelles enables the nanocrystals to disperse in water. Subsequently, the Si nanocrystals were injected into tissue to demonstrate fluorescence imaging, the photothermal transduction efficiency of copper selenide nanocrystals was characterized in water, and the copper selenide nanocrystals were used enhance the photothermal destruction of cancer cells in vitro. The polymer-encapsulated copper selenide nanocrystals were found to have higher photothermal transduction efficiency than 140 nm diameter Au nanoshells, which have been widely investigated for photothermal therapy. Combining the optical properties of metal and semiconductor nanocrystals with the drug-carrying capability of lipid vesicles has received attention lately since it may create a nanomaterial capable of performing simultaneous drug delivery, optical contrast enhancement, and photo-induced therapy. Hydrophobic, dodecanethiol-coated Au nanocrystals were dispersed in water with phosphatidylcholine lipids and characterized using cryo transmission electron microscopy. 1.8 nm diameter Au nanocrystals completely load the bilayer of unsaturated lipid vesicles when the vesicles contain residual chloroform, and without chloroform the nanocrystals do not incorporate into the vesicle bilayer. 1.8 nm Au nanocrystals dispersed in water with saturated lipids to form lipid-coated nanocrystal agglomerates, which sometimes adhered to vesicles, and the shape of the agglomerates varied from linear nanocrystal chains, to flat sheets, to spherical clusters as the lipid fatty acid length was increased from 12 to 18 carbons. Including squalene formed lipid-stabilized emulsion droplets which were fully loaded with the Au nanocrystals. Results with 4.1 nm Au and 2-3 nm diameter Si nanocrystals were similar, but these nanocrystals could not completely load the bilayers of unsaturated lipids. / text Nanocrystal Liposome Vesicle Phosphatidylcholine Lipid Self-assembly Chloroform Anneal Squalene Photothermal Cryo TEM Gold Silicon Nanoshell Emulsion Copper Indium Selenium Octyl-glucopyranoside Detergent dialysis Fluorescence imaging
15	Efficient computational strategies enabling insights into the glass transition Hung, Jui-Hsiang 24 May 2018 (has links) No description available. Polymers Physics the glass transition supercooled dynamics segmental relaxation molecular dynamics simulation quench-anneal Debye-Waller factor particle localization localization-relaxation relationship polymer normal-mode decoupling dynamic heterogeneity
16	Nanoscale Characterization and Control of Native Point Defects in Metal Oxide Semiconductors and Device Structures Gao, Hantian 07 October 2021 (has links) No description available. Condensed Matter Physics Materials Science Physics Solid State Physics Electrical Engineering Nanoscience Zinc Oxide Strontium Titanate Gallium Oixde Cathodoluminescence Dielectric Breakdown MBE SPS Native Point Defects Remote Plasma Neutron Irradiation Thermal Anneal Flash Sintering Surfaces and Interfaces
17	A comprehensive study of 3D nano structures characteristics and novel devices Zaman, Rownak Jyoti 10 April 2012 (has links) Silicon based 3D fin structure is believed to be the potential future of current semiconductor technology. However, there are significant challenges still exist in realizing a manufacturable fin based process. In this work, we have studied the effects of hydrogen anneal on the structural and electrical characteristics of silicon fin based devices: tri-gate, finFET to name a few. H₂ anneal is shown to play a major role in structural integrity and manufacturability of 3D fin structure which is the most critical feature for these types of devices. Both the temperature and the pressure of H₂ anneal can result in significant alteration of fin height and shape as well as electrical characteristics. Optimum H₂ anneal is required in order to improve carrier mobility and device reliability as shown in this work. A new hard-mask based process was developed to retain H₂ anneal related benefit while eliminating detrimental effects such as reduction of device drive current due to fin height reduction. We have also demonstrated a novel 1T-1C pseudo Static Random Access Memory (1T-1C pseudo SRAM) memory cell using low cost conventional tri-gate process by utilizing selective H₂ anneal and other clever process techniques. TCAD-based simulation was also provided to show its competitive advantage over other types of static and dynamic memories in 45nm and beyond technologies. A high gain bipolar based on silicon fin process flow was proposed for the first time that can be used in BiCMOS technology suitable for low cost mixed signal and RF products. TCAD-based simulation results proved the concept with gain as high 100 for a NPN device using single additional mask. Overall, this work has shown that several novel process techniques and selective use of optimum H₂ anneal can lead to various high performance and low cost devices and memory cells those are much better than the devices using current conventional 3D fin based process techniques. / text 3D fin structure 3D nanostructures 3D nano structures Semiconductors Hydrogen anneal Silicon 1T-1C pseudo Static Random Access Memory Memory cells finFET structures Tri-gate FET devices Complementary metal oxide semiconductors CMOS Semiconductors Silicon--Industrial applications Nanostructures
18	Nanolithography on thin films using heated atomic force microscope cantilevers Saxena, Shubham 01 November 2006 (has links) Nanotechnology is expected to play a major role in many technology areas including electronics, materials, and defense. One of the most popular tools for nanoscale surface analysis is the atomic force microscope (AFM). AFM can be used for surface manipulation along with surface imaging. The primary motivation for this research is to demonstrate AFM-based lithography on thin films using cantilevers with integrated heaters. These thermal cantilevers can control the temperature at the end of the tip, and hence they can be used for local in-situ thermal analysis. This research directly addresses applications like nanoscale electrical circuit fabrication/repair and thermal analysis of thin-films. In this study, an investigation was performed on two thin-film materials. One of them is co-polycarbonate, a variant of a polymer named polycarbonate, and the other is an energetic material called pentaerythritol tetranitrate (PETN). Experimental methods involved in the lithography process are discussed, and the results of lithographic experiments performed on co-polycarbonate and PETN are reported. Effects of dominant parameters during lithography experiments like time, temperature, and force are investigated. Results of simulation of the interface temperature between thermal cantilever tip and thin film surface, at the beginning of the lithography process, are also reported. Characterization Deflection Setpoint Grain rearrangement Array Precise positioning Metrology Explosion Explosives Data storage Material Image processing Slow scan disabled Temperature Tip Local In-situ Nanoscale Electrical circuit fabrication Repair Co-polycarbonate Polymers Polycarbonates Energetic materials PETN Simulation Interface Nano-manufacturing Experiment Calibration Raman Frequency Deflagration Decomposition Detonation Build up Pile-up End capped End capping Cross linked Cross-linked Conductivity Microscale MEMS Microcantilever NEMS DPN tDPN Silicon Glass Peak InVOLS Manipulation AFM Atomic force microscope Defense Nanoscale Surface Stiffness Force Scan size Thermal cantilevers Imaging Lithography Nanolithography Thin films Cantilevers Heaters Technology Nanotechnology Scan velocity Scan rate Bake Anneal Pentaerythritol tetranitrate Thin films Thermal properties Atomic force microscopy Microlithography Nanotechnology Surfaces (Technology) Analysis

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