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Full-Text Articles in Engineering
Characteristic Of The Dynamics Of Disorder In Crystalline And Amorphous Materials, Amir Behbahanian
Characteristic Of The Dynamics Of Disorder In Crystalline And Amorphous Materials, Amir Behbahanian
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
This work provides the evidence to apply simulation methods that are applicable to systems with structural randomness to simulate crystalline materials at high temperatures. My work not only open the avenue to expand the simulation capability of materials but also provides insight to the physics of vibrations of atoms under different temperature and for different types of materials. I have also evaluated the reliability of Molecular Dynamics simulations at the frequency level and found that theses types of simulations, despite the previous belief, are reliable at low temperatures but up to a measurable frequency. In addition, the result of my …
Magnesiothermic Combustion Synthesis Of Nanocrystalline Silicon And Oxidation Kinetics Of Magnesium Particles, Sergio Cordova
Magnesiothermic Combustion Synthesis Of Nanocrystalline Silicon And Oxidation Kinetics Of Magnesium Particles, Sergio Cordova
Open Access Theses & Dissertations
Magnesium (Mg) is a well-known reduction agent in metallurgy (more specifically, in metallothermy). Recently, magnesiothermic reduction of oxides has been used in self-propagating high-temperature synThesis (SHS) of advanced materials such as ultrahigh-temperature ceramics (UHTC). The magnesiothermic SHS has also been used for the conversion of silica (SiO2) to silicon-based materials for thermoelectric applications. However, since oxidation of Mg releases a lot of heat, the direct use of it as the reduction agent leads to excessively high temperatures and undesirable sintering of the products. We have proposed to use magnesium silicide (Mg2Si) instead of Mg in the SHS of nanostructured silicon. …
Statistical And Variational Modeling And Analysis Of Passive Integrated Photonic Devices, Norbert Dinyi Agbodo
Statistical And Variational Modeling And Analysis Of Passive Integrated Photonic Devices, Norbert Dinyi Agbodo
Legacy Theses & Dissertations (2009 - 2024)
The success of Si as a platform for photonic devices and the associated availabilityof wafer-scale, ultra-high resolution lithography for Si CMOS has helped lead to the rapid advance of Si-based integrated photonics manufacturing over the past decade. This evolution is nearing the point of integration of Si-based photonics together with Si-CMOS for compact, high speed, high bandwidth, and cost-effective devices. However, due to the sensitive nature of passive and active photonic devices, variations inherent in wafer-based fabrication processes can lead to unacceptable levels of performance variation both within a give die and across a given wafer. Fully understanding the role …
Mechanical Analysis Of A Heterogeneously Integrated Silicon Photonic Interposer, Erica Charlene Graham
Mechanical Analysis Of A Heterogeneously Integrated Silicon Photonic Interposer, Erica Charlene Graham
Legacy Theses & Dissertations (2009 - 2024)
Overcoming the bandwidth bottleneck in conventional interconnects necessitates transitioning to alternative scaling paradigms. Silicon (Si) photonics is considered a disruptive technology, capable of meeting the growing demands for higher bandwidth, low latency, and power efficiency. By leveraging the intrinsic properties of optical signals and manufacturing compatibility of Si, the co-integration of Si photonics and complementary-metal-oxide-semiconductor (CMOS) circuitry leading to terabit data speeds for next generation data communication can be realized. Heterogeneously integrating Si photonic functionality with well-established CMOS technology in an Si photonic interposer architecture simultaneously provides independent optimization as well as close integration of both technologies in one platform. …
Optimization Of Cathode/Anode Electrode Materials For High Performance Lithium-Ion Batteries, Mingwei Shang
Optimization Of Cathode/Anode Electrode Materials For High Performance Lithium-Ion Batteries, Mingwei Shang
Theses and Dissertations
Lithium-ion batteries (LIBs) have been widely used in various devices such as portable devices, communication systems, and electric vehicles (EVs). In this dissertation, towards building LIBs with enhanced energy density and improved performance, Ni-rich cathode and Si-based anode are selected as the electrodes. The performance of LIBs is improved through optimization on both cathode and anode material. Ni-rich layered transition metal oxide with dual gradient on both primary and secondary particles was successfully designed and synthesized through introducing Ni-based metal-organic framework (Ni-MOF) to the coprecipitation of the precursor. During the calcination process, the presence of organic components of Ni-MOFs promotes …
Mechanical Strength Of Germanium Doped Low Oxygen Concentration Czochralski Silicon And The Effect Of Oxygen On Nitrogen Dissociation In Silicon, Junnan Wu
McKelvey School of Engineering Theses & Dissertations
During the Czochralski growth of silicon, it is inevitable for oxygen to be incorporated into the silicon crystal from the quartz crucible. Interstitial oxygen improves the mechanical strength of silicon by pinning and locking dislocations, but also generates thermal donors during device processes, shifting the electrical resistivity. For silicon wafers used in radio frequency (RF) applications, it is important to ensure the high resistivity of the substrates for good RF characteristics. Therefore, the oxygen level in these high resistivity silicon wafers is kept very low (< 2.5 × 1017 atoms/cm3) by carefully controlling the Czochralski growth conditions, in order to reduce the thermal donor concentration to an acceptable level. Silicon on insulator (SOI) substrates made from high resistivity wafers have been widely used for RF applications. SOI manufacturing includes multiple high temperature thermal cycles (1000 – 1100 °C), during which the high resistivity wafers are prone to slip and warpage. Therefore, it is technologically important to recover some of the lost mechanical strength due to the lack of oxygen by introducing electrically inactive impurities to suppress the dislocation generation and mobility in silicon. Germanium (Ge) as an isovalent impurity is 4% larger in size and forms a solid solution with silicon in the entire concentration range. Previous works have shown Ge doping at high concentrations above 6 × 1019 atoms/cm3 increased mechanical strength of silicon with high oxygen concentration (~ 1 × 1018 atoms/cm3). In this work, we explore the effect of Ge doping (7 - 9 × 1019 atoms/cm3) on the mechanical strength of low oxygen concentration (< 2 × 1017 atoms/cm3) silicon, where the oxygen associated dislocation locking and pinning are very low. A mechanical bending test was used to study the average dislocation migration velocity and the critical shear stress of dislocations motion at 600 – 750 °C for Ge doped, nitrogen doped, and undoped low oxygen samples, as well as nitrogen doped float-zone and un-doped high oxygen concentration samples. Next, we fabricated SOI substrates using these high resistivity wafers and compared their slip generation rates and the slip-free epitaxial grow temperature windows after the high temperature thermal cycles (> 1000 °C). Our results indicate at lower temperature Ge doesn’t affect the dislocation mobility …