Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2002. / Includes bibliographical references (p. 45-47). / Magnetic Random Access Memory (MRAM) is considered to be the most viable option for nonvolatile memory in the computer industry. This need for nonvolatile computer memory has resulted in the dramatic evolution of MRAM technology in the past ten years. Currently in the latter stages of development, emphasis is being put on experiments concerning optimization of density and reduction of the switching fields of the magnetic elements. Applications of MRAM technology are currently being explored by companies who seek to obtain relevant intellectual property in those areas. Once research is completed, companies must create a business plan that recognizes the initial, breakthrough markets and implement technology integration accordingly. / by Allison Hernandez. / M.Eng.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (pages 123-139). / Developing new cathode materials is key to improving the energy density of rechargeable batteries and enabling new applications of energy storage. In this thesis, two families of materials were explored as candidate cathode materials: the dirutile and rutile polymorphs of LiMnF4, and layered lithium-excess . . . Dirutile LiMnF4 was identified from high-throughput computation as a promising conversion cathode. The dirutile polymorph was synthesized through a new low temperature route, and the rutile polymorph was discovered upon mechanical milling. With simple synthesis and electrode preparation methods, both dirutile and rutile polymorphs of LiMnF4 showed electrochemical activity. Electron diffraction confirmed both polymorphs to convert upon lithiation along different reaction paths. As with other fluorides, specific capacity was strongly linked with processing conditions. The layered lithium-excess . . . compounds were designed from recent understanding of diffusion channels in lithium-excess materials. Increasing lithium content was found to improve both discharge capacity and capacity retention. Structural studies revealed a complex nanostructure pattern of Li-Sb and Ni-Sb ordering where the interface between these domains formed the correct local configuration for good lithium mobility. The < 1nm Li-Sb stripe domains enable percolation of the low barrier lithium diffusion channels at lower lithium excess levels. The redox mechanisms of the lithium-excess . . . materials were then studied as a function of lithium content and rate. . . . surprisingly exhibited higher discharge capacities at faster rates, and traversed distinct voltage curves at different rates. Characterization of redox processes confirmed nickel redox and oxygen loss, with oxygen redox proposed to account for the balance of the capacity. Finally, irreversible nickel migration is suggested as an explanation for the rate-dependent voltage curve features. / by Nancy Twu. / Ph. D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 99-106). / The primary objective of this work is to establish an innovative and broad platform to engineer living materials and assemble them into functional devices. First, we assemble bacterial sensor communities into core-shell hydrogel structures to address the major challenge of biocontainment. Biosafety has become a major challenge for synthetic biology tools to transition from laboratory experiments to real applications and prevent potential negative impacts. Genetic and chemical containment strategies have been implemented to restrict the growth and replication of genetically modified organisms while no robust physical containment has been proposed. We developed a hydrogel-based encapsulation technique by leveraging a tough biocompatible shell and genetically recoded organisms to achieve unprecedented containment performance. Then, we implemented biocontainment into wearable hydrogel devices. We use stretchable, robust, and biocompatible hydrogel-elastomer hybrids to host genetically programed bacteria, thus creating a set of stretchable and wearable living materials and devices that possess unprecedented functions and capabilities. Lastly, we genetically encode the formation of biological polymers in E.coli to achieve the self-assembly of bacterial devices. Generating complex biomaterials often requires the coordinated and precise expression of several genes and light induction of biological material formation and patterning offer a powerful toolkit to achieve the necessary degree of precision and control. We leveraged a multichromatic optogenetic control in the bacterium Escherichia coli to express the principal structural component biological nanowires. / by Eleonore Tham. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1988. / Includes bibliographical references. / by James Spiros Nakos. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (pages 185-192). / Thin films are the fundamental building blocks of many micro- and nano-scale devices. However, their high surface-area-to-volume ratio makes them unstable due to excess surface free energy. Capillarity drives a process known as dewetting, during which holes form, the film edges retract, and a thickened rim of material accumulates at the edges. Various shape instabilities can occur on the film edge, resulting in complicated morphologies and break-up of the film into isolated particles. Dewetting occurs in the solid state by surface self-diffusion. In this work, a variety of models are presented to gain insights into the mechanisms that control the shape evolution of thin films. A combination of thermodynamic study, stability analyses, analytical models, explicit interface-tracking simulations, and phase-field simulations reveal the underlying driving forces and mass flows, explain observed morphologies and instabilities, and offer insights into how to manipulate the final structure. These pathways to control dewetting are applicable in two areas: to design micro- and nano-scale devices that are resistant to thermal degradation, and to use dewetting as a new patterning method to generate stable, complex, small-scale geometries. / by Rachel Victoria Zucker. / Ph. D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2000. / Includes bibliographical references (p. 183-190). / by Scott A. Uhland. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2003. / Includes bibliographical references (p. 289-301). / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Field emission arrays (FEAs) have been studied extensively as potential electron sources for a number of vacuum microelectronic device applications. For most applications, temporal current stability and spatial current uniformity are major concerns. Using the kinetic model of electron emission, field emission can be described as two sequential processes- the flux of electrons to the tip surface followed by the transmission of the electrons through the surface barrier. Either of these processes could be the determinant of the emission current. Unstable emission current is usually due to absorption/desorption of gas molecules on the tip surface (barrier height variation) and non-uniform emission is usually due to tip radius variation (barrier width change). These problems could be solved if the emission current is determined by the electron supply to the surface instead of the electron transmission through the surface barrier. In this thesis, we used the inversion layer of a MOSFET to control the electron supply. It results in additional benefits of low turn-on voltage and low voltage swing to turn the device on and off. A novel CMP-based process for fabricating integrated LD-MOSFET/FEA is presented. We obtained FEA devices with an extraction gate aperture of 1.3 [mu]m and emitter height of 1 [mu]m. We present a comprehensive study of field emitter arrays with or without MOSFET. The silicon field emitter shows turn-on voltage of [approximately]24 V with field enhancement factor (b[sub]FN) of [approximately]370. We demonstrated that the LD-MOSFET provides excellent control of emission current. The threshold voltage of the LD-MOSFET is [approximately]0.5V. The integrated device can be switched ON and OFF using a MOSFET gate voltage swing of 0.5V. This results in an ON/OFF current ratio of 1000:1. The current fluctuation is significantly reduced when the MOSFET is integrated with the FEA device and the device is operated in the MOSFET control regime. The emission current of the integrated LD-MOSFET/FEA remains stable regardless the gas and vacuum condition. The saturation current level of the integrated devices in the MOSFET controlled region is also the same regardless the emitter array size or the FEA's position on the wafer. We also present a comprehensive study of three-dimensional oxidation in silicon emitter tip / (cont.) formation. Stress plays an important role in the oxidation mechanism. A new sharp emitter tip formation mechanism is proposed: rather than a continuous oxidation process, an emitter neck breaking stage occurs before the sharp emitter tip is formed. Stress from volume difference of silicon and silicon dioxide is the main cause for the emitter neck breaking. Initial formation of microcracks around the neck occurs at high temperature due to volume difference stress, oxide grows into the cracks right after crack formation, and a sharp emitter tip is then formed by further oxidation. / by Ching-yin Hong. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007. / Includes bibliographical references (leaves 145-156). / In this thesis, we discuss the motivation for integrated magneto-optical isolators and explain why the orthoferrite is such an attractive materials class for this purpose. We then derive from first physical principles the dependence of Faraday rotation, absorption, and certain figures of merit on the material's dielectric tensor elements. Next, we use pulsed laser deposition to grow thin films of BiFeO3 on MgO (001) and SrTiO3 (001) substrates. After optimizing growth conditions to obtain high quality films, we characterize the films' crystal structure with two-dimensional x-ray diffraction. We then examine the magnetic, optical, and magneto-optical properties of these films. We find that the highly textured films grown on SrTiO3 are monoclinic with an out-of-plane c-axis aligned with the (001) direction of the substrate and approximate pseudocubic lattice parameters of a = b = 4.04 A, c = 3.95 A, and 90° - [beta] = -0.88°. These films are weakly magnetic, with a magnetization of 1.2 emu/cm3 at an applied field of 10 kOe; highly absorptive, with an average absorption coefficient of 910 cm-1; and possess a low specific Faraday rotation of 320/cm at 1.8 kOe of applied field. As expected, we find that the magneto-optical figure of merit is negligible for this material due to its high absorption, which we attribute to a thin surface layer of phase separated bismuth and iron oxides caused by bismuth segregation during growth. We offer additional explanations for these values and show the first results of newer, more promising work with mixed cation perovskite. / by Alexander R. Taussig. / S.M.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 68-69). / Nanocrystalline nickel-tungsten is a new metallic coating technology developed at MIT in the laboratory of Professor Christopher Schuh in 2005. The new coating technology utilizes a special electrodeposition process to achieve precise control of synthesized nanocrystalline coating structure and resulting properties. This method can produce coatings with enhanced properties including excellent corrosion, wear, and heat resistance in addition to being health and environmentally friendly. At a competitive price along with an efficient coating process, it is anticipated that this coating technology will have high impact on the functional coating industry. This will hopefully lead to future development of other nanocrystalline coating systems. This project focuses on the technology technical and marketing analysis with particular emphasis on the oil and gas industry. The evaluation involves assessing the technology value, highlighting potential applications, comparing with competing technologies and developing commercialization strategies. A comprehensive technical evaluation plan was outlined in order to insure coating suitability for the intended market applications and provide assurance to future clients. This thesis also analyzes several business model strategies to penetrate the oil and gas coating market and proposes what is believed to be the most efficient strategy. Based on the proposed strategy, a detailed cost model is presented to estimate the cost of production and determine pricing options. Finally, several economic outcome scenarios are presented based on the estimated market size and future demands. / by Waleed L. Alotaibi. / M.Eng.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 185-192). / Self-assembly of block copolymer thin-films may provide an inexpensive alternative to patterning lithographic features below the resolution limits of traditional optical methods. Block copolymers (BCPs) are polymers made of two or more distinct monomer/block units that are covalently bonded. Due to their differences in surface energy, the different blocks tend to phase segregate like oil and water; but because of the covalent linkage, this segregation is practically limited to size scales ranging from only a few nm to ~ 100 nm. A thin film of a BCP can be used in much the same way as a photoresist in the lithographic process, whereas a desired pattern morphology can be obtained by etching one block away and leaving behind a self-assembled hard mask for the underlying substrate. After a thin film of BCP is coated onto a given substrate, the BCP must be given an annealing step, where the disordered entangled polymer networks can be allowed to diffuse and equilibrate into lower free energy configurations which result in periodic patterns of micelles with different morphologies such as spheres, in/out of plane cylinders, etc. This work explored the technique of solvent vapor annealing, where organic solvents were allowed to interact with BCP thin films to facilitate annealing and act as surrogates for the different BCP polymer blocks. This allowed for a wide range of control over the BCP self-assembly (morphology, periodicity, etc.) for a given molecular weight BCP. Additionally, by adding heat at critical times during the self-assembly, time scales for solvent vapor enhanced self-assembly could be reduced from hours to seconds making the prospects for this technology to become industrially applicable more promising. / by Kevin Willy Gotrik. / Ph.D.