Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2013. / 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 (p. 177-189). / With the number of alternative lithographic techniques for high resolution and 3D patterning rapidly increasing, there is a need to identify a set of scalable techniques which balances the ability to arbitrarily control every detail of a target pattern and to produce these complex patterns at a high rate. It is in this way that metamaterial devices put forward on a lab scale for applications such as phononics, photonics, and plasmonics can be realized in the industrial scale. This thesis, in approaching this challenge, utilizes combinations of patterning techniques, leveraging the ability for "large" scale alternative lithographic techniques, such as interference lithography or self-assembly, to create the same nanostructured morphology over a large area combined with laser direct write. The process of drawing a single line or isolated voxel can result in a hierarchical pattern defined by the latent motif of the larger-scale technique. The net result is to shift the burden of high resolution patterning from the direct write to the large scale technique, effectively decoupling the correlation between the level of detail and the patterning speed and control. More specifically, the following combinations with laser direct writing were investigated: (1) proximity field nanopatterning for the predefinition of diffraction-order-defined 3D resonators which were applied as "stand-up" plasmonic microresonators, (2) dewetting to conduct development-free 2D patterning of isolated sub-micron lines, and, via overlap effects, nanoscale (<100 nm) gratings, (3) block copolymer self-assembly to initiate the simultaneous annealing and alignment of near-equilibrium microdomains from a metastable starting morphology, and (4) interference lithography to fabricate 3D sub-micron periodic and quasiperiodic hierarchical structures with controllable positioning and tunable fill fraction that has potential for applications to microphotonics. In conjunction with the experimental components of technique development, multiphysics finite element method simulations are used to investigate the structuring mechanism, expected device behavior, and even inverse solutions to the complex problem of arriving at specific target structures. Each of these techniques, along with coupled simulations, represent highly promising first steps towards methods of rapidly generating on-demand hierarchical 2D and 3D structures. / by Jonathan P. Singer. / 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 165-177). / Amyloid and amyloid-like proteins are a broad class of misfolded protein structures known for their their roles in a variety of neurodegenerative diseases, but also for their impressive mechanical properties and their propensity to self-assemble at diverse length scales. These properties make amyloid and amyloid-like proteins excellent candidate materials for the design of engineered functional biomaterials. However, many of the fundamental structure-property relationships which could guide the design of amyloid-based functional materials for various applications are not well understood. In this thesis, a multiscale modeling and simulation approach is used to investigate these structure-property relationships at multiple length scales. Full atomistic simulations are used to study the tensile and bending response of single fibrils, as well as the inter-fibril interaction strength. It is found that in tension, the specific geometry of the fibrils does not significantly influence the deformation behavior, but the mechanical properties, most notably the tensile strength, depends strongly on the areal density of hydrogen bonds in the fibril cross-section. The mechanical response at the molecular scale is used to guide the development of a coarse-grained description of amyloid and amyloid-like fibrils. Next, the adhesive behavior of amorphous polymers is studied to identify design principles which enhance adhesive performance and could be applied to aid in the design of amyloid-based adhesives, an exciting potential functional role for amyloid-based biomaterials. Finally, mesoscale structures are investigated including a nanowire-like geometry and adhesive films. These studies demonstrate that the mechanics of larger scale amyloid based structures are largely determined by the inter-fibril interactions; the specific intra-fibril properties become less significant at larger scales. The results presented in this thesis form the foundation for the development of basic materials selection criteria to aid in the design of functional amyloid-based biomaterials for diverse applications. / by Max Isaac Solar. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009. / Includes bibliographical references (p. 229-235). / The copper (Cu) interconnect has become the bottleneck for bandwidth scaling due to its increasing RC time constant with the decreasing gate line width. Currently, silicon based optical interconnect is widely pursued as the most promising technology to replace Cu in microprocessor chips. Silicon optical interconnect is based on integrated silicon nanophotonic technologies. It can leverage the large scale and low cost of CMOS technology and deliver higher bandwidth with no EMI and low heat dissipation. Passive photonic component, such as waveguides, couplers, filters, splitters, are the backbone of integrated photonic circuit. This thesis is dedicated to the development of low loss, high performance, high index contrast optical waveguides and couplers via materials, processes engineering, development, and device designs. We primarily focus on SOI single crystalline silicon (c-Si or SOI), PECVD amorphous silicon (a-Si:H, or simplified as a-Si), and PECVD silicon nitride (SiNxHy) based single mode channel waveguides.We have previously identified that sidewall roughness scattering is the dominant loss mechanism for the TE mode in high index contrast single mode channel waveguides. In this thesis, we provide a comprehensive understanding of the roughness scattering and its positive correlations with (1) sidewall optical intensity; (2) sidewall RMS roughness; and (3) sidewall index contrast. Novel processes and designs, such as hard mask and chemical oxidation, are developed based on the above understanding. In single mode, 500 x 200 nm2 c-Si channel waveguides, we have achieved world-record 2.7 dB/cm and 0.7 dB/cm transmission loss coefficients for the TE mode and the TM mode, respectively.For deposited waveguides, bulk absorption loss is also important for both TE and TM modes.For PECVD a-Si, we adapt hydrogen passivation to reduce dangling bond density. / (cont.) We also use a thin silicon nitride as the over cladding layer to help preserve H passivation and to reduce sidewall index contrast, acting as the graded index layer for a-Si waveguide core. We have accomplished the lowest reported loss coefficients in directly etched, single mode, 700 x 100 nm2 a-Si channel waveguides of 2.7 dB/cm for the TE mode, comparable to c-Si waveguide with similar dimensions. For the first time, damascene process has also been demonstrated as a promising process for a-Si waveguide fabrication. We have achieved a record-low loss of 2.5 dB/cm in 600 x 100 cm2 a-Si channel waveguides. Chemical-mechanical polishing (CMP) is the most critical step.For PECVD SiNxHy, we have previously identified that the absorption loss is due to the resonant absorption caused by N-H vibration. In this thesis, three different low temperature approaches have been developed and optimized to reduce NH concentration in as-deposited SiNxHY via (1) deposition chemistry; (2) post-deposition Ultraviolet light (UV) treatment; and (3) post-deposition, in-situ N2/Ar plasma treatment. All three processes are compatible with CMOS back-end processes, such as a-Si process. While changing deposition chemistry is the simplest method to obtain low NH containing SiNxHy, it comes with high SiH concentration and may have undesirable properties. Experimentally, for UV treatment, the highest H removal percentage is 60%; for plasma treatment, - 90%. UV treatment shows strong compositional dependence. The underlying mechanism of such dependence is identified and confirmed by Monte-Carlo modeling. Low loss and spectrally broadband optical couplers are indispensable optical components in an integrated photonic circuit. A high performance coupler should be capable of overcoming the mode-size mismatch, mode-shape mismatch, mode-position mismatch, and polarization mismatch, bridging different optical devices with minimal coupling loss. In this thesis, we have demonstrated a fiber-to-waveguide coupler based on asymmetric graded index taper and monolithically integrated cylindrical lens. / (cont.) It is capable of transforming single mode light between single mode fiber and waveguides with minimal coupling loss of 0.45 dB between 1520 nm and 1630 nm. We have also demonstrated a vertical waveguide-to-waveguide coupler that is based on complementary inverse tapers. This design is tolerant of large refractive index mismatch between the two waveguides and also of any fabrication variation that would affect the effective indices of the two waveguides. We have achieved a minimal coupling loss of 0.25 dB per coupler and excellent broadband behavior is also demonstrated. Slot waveguides are a newly developed class of waveguides with unique optical properties. Slot waveguides can achieve exceptional high optical field in nanometer sized low index regions. In this thesis, we have demonstrated low loss transmission of 6 dB/cm for the fundamental slot mode in horizontal slot waveguides at 1550 nm. The horizontal slot configuration removes the constraints of thin slot definition by lithography and allows an arbitrarily thin slot to be fabricated via deposition or oxidation. Because the resulting interface is much smoother than the etched interface, the transmission loss in horizontal slot waveguides is much lower than in vertical slot waveguides. We also demonstrated that multiple slot configurations result in higher optical confinement compared to single slot configurations with the same slot thickness. The low loss and high optical confinement in the low index slot region realized in horizontal slot waveguides promises many useful applications, such as Er-doped silicon-based light emitters. For integration of slot waveguides with conventional channel waveguides, we have designed and simulated mode couplers and polarization rotators for slot-slot, slot-channel waveguide mode transformations.Athermal operation is important for realizing stable passive, WDM optical network on silicon. Athermal design of silicon waveguide systems uses advanced polymer cladding of large negative TO coefficient to provide compensation for the large positive TO coefficient in silicon. The reduced thermo-optic (TO) effect is experimentally demonstrated by reducing TO coefficient from 85 pm/K to 11 pm/K using polymer films. / by Rong Sun. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 173-195). / A new method is developed for direct real-time visualization of shock generation, propagation, and convergence in a sample. The approach opens up new possibilities for controlling the shock parameters and allows one to access pressures in the multiple gigapascal range. Optical generation of shock waves is followed by optical measurement of sample response during and after shock propagation. In this approach, a shock wave is generated that propagates laterally in the plane of the sample (perpendicular to the direction of the optical beam) rather than through the sample plane as in a more conventional approach. The optical configuration and sample geometry make shock wave formation and propagation directly accessible to optical imaging and spectroscopic probes with wavelengths ranging from UV to far-IR. With proper shaping of the optical shock generation pulse, focusing of the shock response can be initiated to provide increased shock pressure. The method has been validated through measurements of shock propagation in liquid water that illustrate some of the possibilities for shock generation, control, and measurement, and demonstrate the utility and potential of the new technique. The charge-coupled device (CCD) and streak camera images recorded provide for the first time a direct dynamic picture of cylindrical shock convergence within the nanosecond time window. This unique technique enables rapid and direct measurement of the dynamic shock responses of advanced materials and structures to diagnose and subsequently optimize their readiness in mitigating blast threats. / by Gagan Saini. / Ph. D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 32-34). / Current work within Strano Research Group shows that single-walled carbon nanotubes (SWNT) wrapped with methacrylic acid-styrene heteropolymer (MA-ST) can be used for specific corona phase molecular recognition (CoPhMoRe) of Vardenafil, a small molecule drug. This project is a follow-up study on viability of related polymers for CoPhMoRe sensing of five small molecule drugs: Fluticasone, Sumatriptan, Valacyclovir, Vardenafil, and Bupropion. Methacrylic acid-vinylphenylboronic acid (MA-VBA) heteropolymer and acrylic acid-styrene (AA-ST) heteropolymer were synthesized at different monomer ratios and chain lengths. These polymers were suspended with the carbon nanotubes and screened against the five drugs. The (12,1) chirality of MA-VBA-4 and (7,5) chirality of AA-ST-2 were found to be potential candidates for sensing of Fluticasone and Vardenafil respectively. However, MA-ST 8 remains as the superior choice for the specific sensing of Vardenafil. / by Jessica H. Sun. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1991. / Includes bibliographical references (leaves 271-275). / by David Edward Dombrowski. / Ph.D.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008. / Includes bibliographical references (p. 54-55). / Inspired by the importance of having a favourable sheathing material for superconducting wires, a high-strength, low thermal coefficient (CTE) super-alloy has been developed. Known as Incoloy 908, this super-alloy's material properties have been extensively studied, and various mechanical, thermal, magnetic, and elastic properties of it have been researched for many years. In the pursuit of broader applications for this superior alloy, this project seeks to identify the most profitable and realistic applications where the fundamental advantages of this technology, due to its unique combination of properties relative to competitors, can create value and be commercialised. This work seeks to quantify the potential value of Incoloy-908 to the market, and on this basis, explore business strategies in which the value of the technology could be realised. The quantitative values assigned to the selected application as a saw blade in saw mills is optimistic in the perspective of the saw mill owner. However, business strategies to realise the potential value through start-up companies are challenging with long investment horizons. Recommendations for future work include developing a more refined estimate of the production costs, and exploring alternative business plans in the context of adopting the technology as an existing manufacturer. / by Heng Lee Henry Liew. / M.Eng.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1991. / Includes bibliographical references (leaves 238-246). / by Ming-Jinn Tsai. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1996. / Includes bibliographical references (leaves 158-162). / by Tony Ping-chen Chiang. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 117-122). / Integration of III-V compound semiconductors with silicon is an area that has generated a lot of interest because III-V materials and Si are best suited for different types of devices. Monolithic integration enables the best material to be chosen for each application, enabling new functionalities with the potential of additional miniaturization on a system level. Integration of GaAsP alloys on Si substrates would enable the creation of high efficiency dual-junction solar cells on low cost and light weight Si wafers and would also enable a path for yellow and green light emission devices on a Si platform. Our work focused on the materials integration problems for multiple pathways to integrate GaAsP alloys on Si substrates. We first addressed the direct integration of GaAsP alloys on Si substrates. Our results showed that despite the low lattice-mismatch conditions at the P-rich end of the GaAsP alloy spectrum, it was difficult to achieve thin films low defect density. We proceeded to focus on the integration of GaAsP alloys on Si via the use of SiGe compositionally graded layers. Through a combination of methods we addressed problems related to antiphase disorder and lattice mismatch between GaAsP and SiGe materials system. We demonstrated the epitaxial growth lattice-matched GaAsP on Si₀.₈₈Ge₀.₁₂, Si₀.₅Ge₀.₅, Si₀.₄Ge₀.₆ and Si₀.₃Ge₀.₇ virtual substrates with excellent interface properties. Our studies showed the effects of initiation conditions and intentional strain at the GaAsP/SiGe heterovalent interface. We have established strain-engineering methods at the GaAsP/SiGe heterovalent interface to prevent dislocation loop nucleation and expansion. We were able to attain GaAsP films on Si with a threading dislocation density as low as 1.2x10⁶/cm² . Our GaAsP/SiGe heterovalent interface research advanced the understanding of such structures. We developed methods to fabricate optimized GaAsP tunnel junction film, which would be necessary for any current-matched dual junction solar cell design. Prototype dual-junction GaAsP/Si solar cell test devices showed good preliminary performance characteristics and offer great promise for future devices integrated with the newly developed high quality GaAsP/Si virtual substrates. / by Prithu Sharma. / Ph. D.