Recursos de colección

DSpace at MIT (104.280 recursos)

This site is a university repository providing access to the publication output of the institution. Registered users can set up email alerts to notify them of newly added relevant content. A certain level of encryption and security is embedded in the site which may cause some users accessibility problems.

Materials Science and Engineering - Bachelor's degree

Mostrando recursos 1 - 20 de 266

  1. Cost benefit analysis of process change implementation : alternate wet cleaning technology in the semiconductor manufacturing industry

    Vazirani, Raj A. (Raj Anand)
    Maintaining wafer surfaces free of contamination is an essential requirement for the successful fabrication of semiconductor devices. With the growing trend of increased device complexity and reduction of device feature sizes, the area of wet cleaning of substrate surfaces has gained importance. The existence of organic and metallic contaminant particles and thin films on a wafer surface can drastically reduce line yield. Recent improvements in wet cleaning technology have presented alternate wafer cleaning techniques. The J.T. Baker clean process is a two step replacement for the four step RCA clean which is the current industry standard. The J.T. Baker clean...

  2. Technical choice in pottery production : a west Mexican example

    Meanwell, Jennifer L. (Jennifer Lauren)
    This thesis identifies the pottery engineering techniques of ancient Mexican potters from the site of La Queseria in the Balsas depression of Guerrero. I used data from petrography, geologic maps, clays from the area, x-ray diffraction and mechanical testing to determine whether these potters were using different clays for different functional designs. I determined that the potters used local clay for all pots, that some relation exists between the function of the pot and its material and processing technology, and that hence these potters were engineering their pottery.

  3. Oxygen precipitate studies in silicon for gettering in solar cell applications

    Salomon, Ashley
    Oxygen precipitates in silicon can be used (in a process called internal gettering) as sites of heterogeneous nucleation of precipitates of iron and other transition metal that are harmful to solar cell device operation. Oxygen precipitate densities in p- (10¹⁴ boron atoms/cm³) wafers were quantified using chemical etch techniques. The precipitate densities were then used to estimate times to getter iron based on a diffusion limited precipitation model. Oxygen precipitate densities in p++ (10¹⁹ boron atoms/cm³) wafers were quantified using chemical etch techniques. High levels of boron in p++ wafers make quantifying precipitate densities particularly difficult, via etching, or other...

  4. Optical absorption of bismuth silicon oxide (Bi₁₂SiO₂₀) crystals

    Lee, Grace W. (Grace Wang)
    The purpose of this work is to characterize the optical absorption in bismuth silicon oxide (Bi₁₂SiO₂₀) crystals grown using the Bridgman technique and to identify electronic transitions responsible for absorption. Optical measurements were taken in the range of 0.4 - 11 pm at 300 K and 77 K using a spectrometer. The results show that near the band edge, there is evidence of indirect transitions at 2.3 eV and excition transitions at 1.8 eV. Low temperature measurements revealed peaks of free carrier absorption in the visible light range at 1.7 eV and 2.1 eV. Illuminated samples at low temperature revealed...

  5. Diffuse double-layer interaction for nonspherical colloidal particles

    Jhon, Mark
    The DLVO theory of colloids is used to consider the stability of clay colloid particles. An approach to colloid physics using classical electrostatic methods is presented. Specifically, the electrical double layer is examined using computational methods. To this end, the Poisson-Boltzman equation is solved numerically for geometries corresponding to interacting clay particles. The interaction energies of double layers is calculated for several particle configurations.

  6. Fabrication of In₂(Se, Te)₃ chalcogenide thin films by thermal co-evaporation

    Gupta, Shikha, S.B. Massachusetts Institute of Technology
    In₂(Se, Te)₃ III-VI chalcogenides belong to a unique class of phase change materials that have interesting optical and electrical properties, making them suitable for a wide variety of applications, including absorbers for solar cells and storage materials in memory devices. A greater understanding of how different growth parameters influence the crystallinity and microstructure of such chalcogenide thin films can lead to an enhanced ability to manipulate the materials for desired optoelectrical characteristics. The purpose of the following thesis was threefold. The first was to fabricate homogeneous, single-phase thin films of In2(Se, Te)₃ using thermal co-evaporation of elemental In and (Se,...

  7. Materials characterization and transmission analysis in erbium-doped gallium nitride microresonator structures

    Gibbons, David M
    GaN:Er is an attractive material for room temperature 1.54 pm luminescence enhancement devices for use in telecommunications because it does not experience thermal quenching at room temperature like Si:Er and can be electronically pumped. GaN:Er layers grown by molecular beam epitaxy (MBE) on single crystal substrates have shown excellent room temperature 1.54 [mu]m luminescence, but to integrate GaN:Er into microresonator devices it is necessary to grow a good quality GaN:Er film on an amorphous substrate. This thesis examines the optical properties and morphology of GaN:Er layers grown on Si₃N₄ and SiO₂ substrates, and evaluates two microresonator devices with incorporated GaN:Er...

  8. Finite element modeling of the human eye

    Chan, Venetia (Venetia V.)
    A three-dimensional finite element model was created to analyze the mechanical interactions between the various substructures within the human eye. During certain activities, mechanical interactions may lead to a resultant distribution of stresses within the eye that may in turn produce various retinal diseases. The entire eye was modeled using dynamic finite element analysis to incorporate the mechanical effects of all of the substructures on the retina. A set of mechanical properties for each substructure was determined from previously published studies. Saccadic motion was modeled in the normal human eye to determine the location and magnitude of peak stresses in...

  9. A study of Nb3(Al.75Ge.25) and V3Au superconducting tunnel junctions.

    Gregory, James Allen
    Massachusetts Institute of Technology. Dept. of Metallurgy and Materials Science. Thesis. 1973. B.S.

  10. Analysis of materials properties of thin film structures for thermoelectric and thermophotovoltaic applications

    Baum, Brian K
    Metal-organic chemical vapor deposition (MOCVD) was used to grow InAsP graded layers and AlAs/GaAs superlattices for materials studies related to thermophotovoltaics and thermoelectrics respectively. High resolution x-ray diffraction (HRXRD) was used to determine the As concentration in each of the InAsP layers. Arsenic concentration was found to vary linearly with the percentage of AsH3 in the reactive gas flow up to 60 % deposited, and had an asymptotic relationship for higher incorporated concentrations. Higher growth temperatures reduced As incorporation. Transmission electron microscopy (TEM) images were used to determine layer thicknesses. The growth rate of InAsP layers was found to be...

  11. In search of martensite : titanium-tantalum shape-memory alloy

    Disko, Jeffry
    There is a broad range of life-saving medical implants and devices that rely on the shape-memory (SME) and superelastic properties of various nickel-based alloys [8]. Unfortunately, there is also serious concern about the toxicity of nickel. Titanium based shape-memory alloys have been noted as potentially non-toxic replacements of the more traditional, nickel-based shape memory alloys. In this thesis I present research concerning the potential of SME-capable titanium-tantalum alloys to replace Ni-based alloys in medical implants. A method for heat treatment of Ti -Ta alloys of varying compositions to induce formation of martensite was developed. Heat-treated alloys were then tested for...

  12. Semi-solid redox flow battery

    Duduta, Mihai
    materials used in Li-ion batteries and the design and functioning of a redox flow cell. The use of Li-ion battery materials offers significant increases in energy and power density (200 Wh/kg compared to 25-35 Wh/kg for current commercial vanadium redox batteries). The implementation of a redox flow system allows for energy to be stored outside the cell and for the power and energy of the battery to be decoupled. A proof of concept is achieved by successful cycling of anode and cathode suspensions under intermittent flow conditions. The importance of materials' stability to cell life, energy and power densities is...

  13. Edible photonic crystals tunable within the visible regime

    González, Xavier (Xavier R. González Barrios)
    An experimental study was performed to design and fabricate an edible photonic crystal made of alternating layers of food grade titanium dioxide and agar that is able to selectively reflect wavelengths of light within the visible spectrum and allow for dynamic color changes through the tuning mechanism of swelling its agar layers with the addition of edible solvents. After doing a literature search to discover which materials were available to create this edible photonic structure, a trial and error process was conducted using deposition and film thickness characterization techniques to optimize the physical and optical characteristics of the layers composing...

  14. The natural interface between bone and tendon : SEM observations of the enthesis in an ovine model

    Reese, Willie Mae
    The present study investigates the naturally occurring interface between bone and tendon using scanning electron microscopy. The micrographs revealed a cartilaginous layer, 100 to 400 [mu]m thick apposing bone, that contained cells varying in size and shape as a function of their location in this cartilaginous layer. Further investigation is required to conclude whether these cells are undergoing further differentiation during development of this graded layer. This study found the interface between bone and the cartilaginous layer to be interdigitated, which may explain why injuries at the bone-tendon interface are comparatively rare. Also, the cartilaginous layer was revealed to be...

  15. TCAQ-based polymer for electrochemically mediated separations

    Thai, Emily (Emily Sue)
    Redox-mediated separation systems offer the potential to efficiently desalinate water and to purify contaminated waste streams, among other health and environmental applications. A TCAQ-based polymer, unique for its two-electron redox reaction, was synthesized for use in redox-mediated separation systems, and its performance was quantified in low-concentration aqueous salt solutions. The polyvinyl ferrocene (PVF)//PTCAQ system displayed an ion adsorption capacity much higher than previously reported literature values for capacitive or redox deionization systems.

  16. TCAQ-based polymer for electrochemically mediated separations

    Thai, Emily (Emily Sue)
    Redox-mediated separation systems offer the potential to efficiently desalinate water and to purify contaminated waste streams, among other health and environmental applications. A TCAQ-based polymer, unique for its two-electron redox reaction, was synthesized for use in redox-mediated separation systems, and its performance was quantified in low-concentration aqueous salt solutions. The polyvinyl ferrocene (PVF)//PTCAQ system displayed an ion adsorption capacity much higher than previously reported literature values for capacitive or redox deionization systems.

  17. Assessing the criticality of germanium as a by-product

    Tadjfar, Nagisa
    Although germanium production is currently nowhere near its supply potential, many sources cite germanium, a by-product material produced primarily from zinc and coal, as a critical metal. Current methods for assessing criticality include frameworks that rely on geopolitical risk metrics, geological reserves, substitutability, and processing limitations during extraction among others but there is a gap in understanding the complex supply and demand dynamics that are involved in the market for by-products. This thesis addressed this gap by assessing the supply risk of germanium using an econometric framework to generate estimates of price elasticities. Annual world production and price data of...

  18. Assessing the criticality of germanium as a by-product

    Tadjfar, Nagisa
    Although germanium production is currently nowhere near its supply potential, many sources cite germanium, a by-product material produced primarily from zinc and coal, as a critical metal. Current methods for assessing criticality include frameworks that rely on geopolitical risk metrics, geological reserves, substitutability, and processing limitations during extraction among others but there is a gap in understanding the complex supply and demand dynamics that are involved in the market for by-products. This thesis addressed this gap by assessing the supply risk of germanium using an econometric framework to generate estimates of price elasticities. Annual world production and price data of...

  19. Selective solar absorber materials : nanostructured surfaces via scalable synthesis

    Rubin, Julia G. (Julia Grace)
    Current solar to thermal energy conversion technologies, including concentrated solar power (CSP) and solar water heaters (SWH) utilize absorber surfaces that collect incident solar radiation. However, these absorber surfaces emit thermal energy (at their temperature) in the infrared (IR) spectrum, resulting in decreased overall efficiency for solar-to-thermal conversion. Selective absorber surfaces are highly absorptive in the solar spectrum, yet highly reflective in the infrared spectrum and therefore have the potential to minimize thermal energy loss. Copper Oxide (CuO) nanostructures are a candidate selective absorber material due to high absorptivity in the solar spectrum (about 95%), relatively high reflectance in the...

  20. Selective solar absorber materials : nanostructured surfaces via scalable synthesis

    Rubin, Julia G. (Julia Grace)
    Current solar to thermal energy conversion technologies, including concentrated solar power (CSP) and solar water heaters (SWH) utilize absorber surfaces that collect incident solar radiation. However, these absorber surfaces emit thermal energy (at their temperature) in the infrared (IR) spectrum, resulting in decreased overall efficiency for solar-to-thermal conversion. Selective absorber surfaces are highly absorptive in the solar spectrum, yet highly reflective in the infrared spectrum and therefore have the potential to minimize thermal energy loss. Copper Oxide (CuO) nanostructures are a candidate selective absorber material due to high absorptivity in the solar spectrum (about 95%), relatively high reflectance in the...

Aviso de cookies: Usamos cookies propias y de terceros para mejorar nuestros servicios, para análisis estadístico y para mostrarle publicidad. Si continua navegando consideramos que acepta su uso en los términos establecidos en la Política de cookies.