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Description
The standard theory of indirect gap optical absorption in semiconductors predicts an unphysical divergence when the photon energy reaches the direct band gap. Current theoretical efforts to eliminate this divergence require experimental validation with measurements covering a spectral region that exceeds the direct band gap. For transmittance and reflectance measurements needed in examining the absorption in a material like Ge, the needed film thicknesses are too small for the samples to be mechanically stable. On the other hand, very thin films can be grown epitaxially on silicon.
This thesis focuses on testing a novel technique for examining absorption in these thin films. Spectrophotometry was used to measure the reflection and transmission over a spectral range of 0.54 eV to 1.38 eV for various epitaxial thin film Ge on Si samples. The resultant data was then renormalized and used in a custom spline fitting procedure to extract the dielectric/optical constants over the established spectral range.
Analysis of the extracted dielectric function spectra indicates an apparent bias towards thinner films (less than 1000 nm) in producing spectra having good agreement with new theoretical models. Dielectric function spectra from thick samples (over 2000 nm) show well matched general behavior but fail to accurately predict regions of absorption around the band gap.
ContributorsBoone, David (Author) / Menéndez, Jose (Thesis director) / Kouvetakis, John (Committee member) / Barrett, The Honors College (Contributor) / Materials Science and Engineering Program (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Department of Physics (Contributor) / School of Sustainability (Contributor)
Created2025-05
Description
In this project, a anatomically similar lung model was built in order to test a inhaler prototype. The model needed to generate a specific level of peak inspiratory airflow (PIF), a clinically relevant measure of how a patient breathes to actuate an inhaler. Three lung models were built throughout the design process, and the final two were analyzed using a Design of Experimentation varying two factors: chest cavity volume and airway tubing diameter. Results found significant relationships between the chest cavity volume and PIF, as well as the interaction between the two factors and PIF. Future work could improve the model with more data collection capabilities, a more consistent actuation mechanism, and different physiological parameters to reflect other populations.
ContributorsWada, Alexander (Author) / Sugar, Thomas (Thesis director) / Arquiza, J.M.R. Apollo (Committee member) / Rank, Matthew (Committee member) / Barrett, The Honors College (Contributor) / School of Biological & Health Systems Engineering (Contributor) / Materials Science and Engineering Program (Contributor)
Created2025-05
Description
Brew Games offers a portable solution to the lack of compact tabletop games. By packaging games like Card Classics inside screw-top aluminum cans, the product provides a convenient and travel-friendly option for social settings such as bars and breweries. With essentials like poker chips, cards, and dice, users can enjoy games like poker or euchre without bulky boxes. Targeting social, non-sports fans, Brew Games aims to offer an engaging alternative to watching TV or sports at slower venues. The company plans to expand its lineup with additional games, making tabletop gaming a regular, enjoyable activity in casual settings.
ContributorsCagno, Connor (Author) / Belknap, Austin (Co-author) / Kamdar, Mitali (Thesis director) / Byrne, Jared (Committee member) / Barrett, The Honors College (Contributor) / Materials Science and Engineering Program (Contributor) / School of Technology,Innovation & Entrepreneurship (Contributor)
Created2025-05
Description
Cadmium Telluride (CdTe) is a promising II–VI photovoltaic material, offering a detailed-balance efficiency limit around 30%. However, achieving this potential in practice requires minimizing non-radiative losses. This thesis examines the effects of black-body radiation of a CdTe/InSb solar cell absorber layer. Here, both experimental and theoretical approaches are used to understand how black-body emission and recombination losses influence solar cell device performance. Key topics include black-body radiation fundamentals, calibration of a black-body source, optical absorption in monocrystalline vs. polycrystalline CdTe absorbers, the Shockley–Queisser limit under radiative recombination, and photoluminescence quantum efficiency (PLQE) measurements. The goal was to understand how intrinsic thermal radiation and device design limit open-circuit voltage and efficiency, and how advanced structural engineering such as heterostructure barrier layers can mitigate these limits. In fact, the PLQE of the measured sample appeared to be extremely low: 6×10^(-7)%, which indicated a very large non-radiative recombination. Transmission Electron Microscopy and Solar Cell Modelling were utilized to explain this result. By using modified Shockley–Queisser approach to account for large non-radiative recombination, a more realistic maximum efficiency of 9.28% was calculated.
ContributorsVoinkov, Ky (Author) / Zhang, Yong-Hang (Thesis director) / Smith, David (Committee member) / Ju, Zheng (Committee member) / Barrett, The Honors College (Contributor) / Materials Science and Engineering Program (Contributor) / Department of Physics (Contributor) / School of Mathematical and Statistical Sciences (Contributor)
Created2025-05
Description
Structural color is the phenomenon where features of the material’s structure interact with light, causing it to interfere with itself, producing color. Examples of structural color are seen everywhere from the rainbow pattern on the back of CDs to the color of a butterfly's wings. Optical thin films that make use of structural color are used in a massive range of industries however, a typical thin film stack is limited to the configuration it is set in upon fabrication, thus tunable devices able to change their configuration would have huge potential for use in multi-functional devices to fill the gap of tunable optical thin film technology. A Floating Solid-State Thin Film (FSTF), where an applied voltage moves a metal film through a dielectric one, producing structure changes which change the device’s color, is one such device and Polymer-assisted Photochemical Deposition is a technique able to 3D print metal thin films of the same element used in prior FSTF research in a desired pattern without vacuum or heating. PPD could greatly improve the efficiency of micro- and opto-electronics manufacturing and the author’s group has previously done work comparing optical thin film structures made with PPD films to those made with conventionally deposited metals and they have shown promising results in this space. The purpose of this project then was to investigate whether a PPD metal film was capable of the migration demonstrated by a conventional film to function in a FSTF device. Devices of several architectures with SiO or PMMA dielectric layers and thermally evaporated or PPD silver metal layers were fabricated using a variety of techniques. The devices were tested by being connected to a 1 V and 4.5 V battery with the voltage applied being measured during testing and the device behaviors were observed. Blindspots and possible points of weakness in the experimental plan were identified post testing in both device testing and device design. These included unaccountability of the testing set-up for voltage drops creating uncertainty in the actual voltage needed and the actual voltage applied to the film as well as metal thin film thickness preventing device function in some cases by reflecting light away from the device cavity. Improvements which address these issues were identified and a new device design as well as improvements to the testing set-up were described which could be used in future work.
ContributorsBorea, Dante (Author) / Wang, Chao (Thesis director) / Yao, Yu (Committee member) / Barrett, The Honors College (Contributor) / Materials Science and Engineering Program (Contributor) / School for Engineering of Matter,Transport & Enrgy (Contributor)
Created2025-05
Description
Due to the natural abundance of sodium in the Earth’s crust and its low specific cost, new research has shown that Sodium Ion Batteries (SIBs) are an increasingly viable solution for sustainable energy storage. SIBs have the potential to be a more cost-effective alternative to Li-Ion batteries. However, there are several performance issues that hinder their charge capacity and capacity retention, largely attributed to electrode-electrolyte side reactions. In order to be effectively commercialized, these issues must be investigated, understood, and improved upon. It has been observed that the electrode-electrolyte interface (EEI) has a large impact on the overall cell performance in SIBs. While EEI layers are still trying to be fully understood, there is evidence that suggests electrolyte additives may assist the formation of synergistic EEI layers that can improve these major capacity issues in SIBs. Here, the use of three electrolyte additives (FEC, TMSB, and VC) with the MuNC cathode material is reported. From electrochemical cycling data, it was found that these additives greatly extend the lifetime of the MuNC cathode material. Further analysis is performed to understand the effectiveness of electrolyte additives as a solution to stability issues in Na-ion batteries.
ContributorsJacobs, Matthew (Author) / Mu, Linqin (Thesis director) / Chan, Candace (Committee member) / Barrett, The Honors College (Contributor) / Materials Science and Engineering Program (Contributor)
Created2025-05