Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (pages 111-120). / It is no wonder that research in Si photonics (optical components embedded on a silicon platform) has bloomed so rapidly the last few years. Combining low loss, strong refractive index contrast (and, thus, light confinement), with electro-optical and thermo-optical effects, allows for the fabrication of dense and complex electro-optical Si photonics systems. Moreover, because it is based on the well-established platforms of the CMOS industry, Si photonics is expected to rapidly shift from a research field to the production of high volume, low cost, complex, integrated electro-optical systems. One class of systems receiving increasing interest are Nanophotonic Phased Arrays (NPAs), which offer free space emission of a manipulated beam that can be steered, focused, have controlled angular momentum and even create holograms. Still, some substantial challenges remain in applying these NPAs to real systems. Large cell size and spacing between adjacent antennas produce multiple beams and reduce effective steering angle. In addition, small beam angle requirements and large aperture in NPAs receivers demand large phased array size. In order to allow for both steering angle and large aperture, a large array with small cell size is required resulting large number of unit cells in one array. In this work, we first propose two metallic nanoantennas to couple between a waveguide mode to free space radiation. Then, by combining existing Si photonic components like directional couplers and modulators with optical antennas and phase shifters that were designed for this goal we demonstrate, in this work, several NPAs for various applications. Using unique architecture, we then, specifically focus on a, NPA based, lidar. These lidar systems are essential components in any autonomous system maneuvering in an undefined environment. An on chip lidar like this one can serve, for example, in the automotive industry for safety enhancement and to allow autonomous driving functionality at an affordable price. / by Ami Yaacobi. / Ph. D.

Thesis: M. Eng., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 68-72). / The bringing of high efficiency photovoltaics from extraterrestrial applications to terrestrial ones has begun to be realized. The micromorph tandem solar cell shows great promise as it boasts both high efficiency and low cost. The device consists of an amorphous top cell and a microcrystalline bottom cell. Optimization through high-rate silicon deposition, light trapping, and film growth make efficiencies of 15% possible. Current micromorph cells in the market are competitive in performance and cost to other similar technologies. This paper reviews the research progress and market penetration of this young but promising technology. / by David Allen Wong. / M. Eng.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1998. / Includes bibliographical references (leaves 59-61). / by Sarah L. Ransom. / S.M.

Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 47-50). / III-V materials have great potential for integration into future complementary metal-oxide-semiconductor technology due to their outstanding electron transport properties. InGaAs n-channel metal-oxide-semiconductor field-effect transistors have already demonstrated promising characteristics, and the antimonide material system is emerging as a candidate for p-channel devices. As transistor technology scales down to the sub-10-nm regime, only devices with a 3D configuration can deliver the necessary performance. III-V fin field-effect transistors (finFETs) have displayed impressive characteristics but have shown degradation in performance as the fin width is scaled to the sub-10-nm regime. In this work, we use high-resolution transmission electron microscopy (HRTEM) in an effort to understand how interfacial properties between the channel and high-k dielectric affect device performance. At the interface between the channel material, such as InGaSb or InGaAs, and the high-k gate dielectric, properties of interest include defect density, interdiffusion between the semiconductor and dielectric, and roughness of the dielectric - semiconductor interface. Using HRTEM, we can directly study this interface and try to understand how it is affected by different processing conditions and its correlation with device characteristics. In this thesis, we have analyzed both InGaAs and InGaSb finFETs with state-of-the-art fin widths. Analysis of TEM images was combined with electrical data to correlate interfacial properties with device performance. We compared the materials properties of InGaAs and InGaSb and also explored the impact of processing steps on interfacial properties. / by Lisa Kong. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1994. / Includes bibliographical references (leaves 98-100). / by Peter Kofinas. / Ph.D.

Includes bibliographical references (p. 107-119). / Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008. / We present a gel route to process highly oriented conjugated polymer films and fibers. The incorporation of hexafluoroisopropanol, a strong and stable dipolar group, to the polythiophene backbone enhances the solubility and especially, the hydrogen bond forming capabilities of the polymer. This functionalization enables the polymer to build up an isotropic self-supporting network structure based on a combination of polymer-polymer chain interactions and interchain hydrogenbondings. These thermally reversible physical crosslinks incorporate plasticity in the conjugated polymer gel. The gel network can be melted and then transformed via mechanical deformation to form an anisotropic gel with the chains highly aligned along the tensile direction. The oriented gel morphology comprises a distribution of crystalline clusters in an overall swollen network. In these ordered regions, conjugated backbones are [pi]-stacked with respect to each other neighbors. The mechanically induced structural rearrangement from an isotropic to an anisotropic conjugated polymer gel occurs when transitioning from the molten state to the gel state. This study highlights the versatility of incorporating plasticity in the design of conjugated polymer materials via a gel processing technology and its potential for applications. / by Daniel Alcazar Jorba. / M.Eng.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1998. / Includes bibliographical references (leaves 149-154). / The increase in demand for faster and more powerful microprocessors in recent years has been the driving force to introduce new materials and processes into semiconductor fabrication facilities. As each fabrication facility tries to maximize its yield, it is mandatory that there exist metrology techniques to characterize both materials and processes. This mandate is the motivation behind this thesis. In this thesis, the metrology of two different systems used in VLSI technology are investigated. The first system is the material, Separation by IMplanted OXygen (SIMOX) buried oxide. SIMOX technology has been studied extensively as a viable alternative to bulk silicon technology in radiation-hard and low-power applications. However, there is still a lack of knowledge on the nature of the defects present in the SIMOX buried oxide and their impact on basic BOX electrical characteristics, such as BOX high-field conduction. In this thesis, greater understanding about the excess-silicon related defects in the buried oxide has been obtained concerning their nature, origin, and impact on the conduction characteristics. Further understanding about the silicon islands in the buried oxide has also been obtained concerning their formation and impact on the high-field conduction characteristics. Finally, a metrological application of the BOX high-field conduction model is demonstrated. The second system is the process, Nitride/Shallow Trench Isolation (STI) Chemical Mechanical Polishing (CMP). CMP processes have been heralded as a way to planarize films and structures on wafers to a degree which has not been possible before. However, recent studies have shown that the uniformity of CMP processes depends on the layout-pattern density. To address this issue, an oxide CMP model has been developed to show the relationship between layout-pattern density and the polish rate. However, there is an uncertainty as to how this single-material system model can be extended to other material systems and dual-materials systems. In this thesis, the metrology and modeling techniques for oxide CMP are extended to nitride CMP in order to understand the pattern-density and materials dependence for this particular CMP process. In addition, the planarization and uniformity of the two-material system for STI structures is investigated. A model explaining the relationship between a particular STI layout-pattern density and the resulting planarization is developed. / by Jung Uk Yoon. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1999. / Includes bibliographical references (leaves 149-152). / by Rajan Vaidyanathan. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008. / Vita. / Includes bibliographical references (leaves 241-251). / The subject of this thesis lies at the interface of microfabrication technology and advanced biomaterials synthesis and processing for use in designing and fabricating novel tissue engineered constructs. The unifying theme is to use micron and sub-micron fabrication strategies to form advanced tissue engineering scaffolds which are able to precisely control the microenvironment of cells. These efforts are organized into two thrusts; (1) materials synthesis and process development for microfluidic scaffold fabrication and (2) micro- and nanofabricated synthetic substratum for controlling cell function. In the first thrust, materials-specific processes for the fabrication of poly(glycerol-co-sebacate), a synthetic elastomeric biodegradable polyester, into three-dimensional, hepatocyte-seeded microfluidic constructs is discussed. Material advantages of natural proteins motivated the fabrication of next-generation microfluidic scaffolds using silk fibroin from the Bombyx mori as a bulk material. The need to combine the advantages of both natural proteins and synthetic polyesters motivated the synthesis and characterization of a new class of biodegradable elastomers termed poly(1,3-diamino-2-hydroxypropane-co-polyol sebacate) (APS). APS polymers are tunable and possess the advantages of both natural and synthetic polymers. APS polymers induce a favorable biomaterial-tissue response including reduced fibrous capsule formation and macrophage recruitment compared to PLGA. In vivo degradation half lives could be controlled to between approximately 6 and 100 wks by adjusting polymer composition and processing. The second thrust focuses on the interaction with cells and synthetically fabricated nanotopographic substrates for potential in vascularized tissue engineering applications. / (cont.) The contact guidance response of human embryonic stem cells to poly(dimethylsiloxane) (PDMS) substrates with 600 nm ridge-groove geometry and 600 ± 150 nm feature height was characterized. This motivated the study of endothelial progenitor cell function and morphology on nanofabricated PDMS substrates. Endothelial progenitor cells (EPCs) were found to exhibit increased doubling time from 16.2 ± 0.8 to 20.9 ± 1.9 h for cells grown on flat and nanotopographic substrates, respectively. EPCs cultured on nanotopographic substrates had a faster velocity and enhanced directed migration. The average velocity of EPCs on nanotopographic and flat substrates was 0.80 ± 0.45 and 0.54 ± 0.27 pm-min-1, respectively, while the effective displacement due to migration was 23.6 + 12.1 and 15.6 ± 10.1 Pm. Lastly, an in vitro capillary tube formation assay induced the formation of larger, more organized vascular structures in EPCs cultured on nanotopographic (411 ± 209 pm) versus flat substrates (140 + 35.6 [mu]m). This work has validated the potential impact of microfabricated scaffolds in tissue engineering by modulating cell function and controlling microenvironmental parameters. / by Christopher John Bettinger. / Ph.D.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009. / 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. 47-48). / The proposed light trapping technology of Distributed Bragg Reflector (DBR) with Diffraction Grating (DG) and Anti-Reflection Coating (ARC) for thin film Si solar cell was analyzed from the technology, market, and implementation perspectives. Two applications were investigated. For monocrystalline thin film Si solar cell, layer transfer technology is too expensive, while sliver Si technology is more applicable, but impossible to add DBR and DG structure on sliver Si that still attached on native wafer. For amorphous thin film Si solar cell, the cost model was created. Even though best-case assumptions were used, the cost/performance ratio of amorphous thin film Si equipped with proposed light trapping technology was still higher (worse) than incumbent amorphous thin film Si solar cell. / by Rahmat Agung Susantyoko. / M.Eng.