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Effect of Growth Conditions on the Performance of Vertically Conducting Beta-GA2O3 Diodes on 4H-SIC Substrate by MOCVD
No full textThis thesis highlights the critical influence of doping strategies, specifically co-delta doping with silicon (Si) and indium (In), on improving the structural quality and device performance of β-Ga₂O₃-based Schottky barrier diodes (SBDs). To achieve better thermal management, β-Ga₂O₃ thin film was grown on bulk 4H-SiC substrates using the Metal-Organic Chemical Vapor Deposition (MOCVD) technique, renowned for its precise control over composition, thickness and doping profile. The ultra-wide bandgap (UWBG), high critical breakdown field and low turn-on resistance of β-Ga₂O₃ make it a strong candidate for next-generation power electronics and short-wavelength detection in extreme environments. However, the presence of structural defects can severely degrade key device parameters such as breakdown voltage, carrier transport and thermal stability, prioritizing the importance of high crystalline quality in film growth.
In this study, a vertically conducting β-Ga₂O₃ SBD structure was realized by first depositing a Si-doped layer (5 × 10¹⁷ cm⁻³) and then a 0.25μm undoped buffer layer with a total epitaxial thickness of approximately 0.5μm. Three distinct doping approaches were systematically studied: co-delta doping with Si and In, Si delta doping alone, and continuous Si doping; each implemented under identical growth conditions to determine the effect of doping configuration on material and device characteristics. Structural and chemical characterizations were carried out using X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Among these, the co-delta doping approach resulted in the narrowest full width at half maximum (FWHM) of the (-402) XRD peak (0.44°), indicating superior crystallinity. This was further supported by Raman analysis of the Ag(3) vibrational mode near 204 cm⁻¹, which showed a sharper and more intense peak under co-delta doping. XPS analysis confirmed the uniform incorporation of Si dopants and less than 1% Indium as surfactant in the co-delta doped films which is crucial for achieving stable and efficient device operation. All three devices fabricated with a 100μm contact diameter and characterized through I–V measurements exhibited high turn-on voltages due to the undoped layer. However, the co-delta-doped structure demonstrated significantly lower on-resistance and an enhanced forward current compared to its delta-doped and continuously doped counterparts. These results clearly illustrate the effectiveness of co-delta doping in optimizing UWBG semiconductor growth for high-efficiency power electronic applications
Episode 89: The Legacy of Slavery at South Carolina College with Dr. Jill Found
No full textPh.D. graduate Jill Found wrote a dissertation on the history of enslaved people at South Carolina College, which helped tell the story of some of the university\u27s overshadowed people from the past
“Being Natural is Simply a Pose”: The Concept of Foucault’s Panopticon in The Picture of Dorian Gray and Orlando
No full textEpisode 91: Digging in the Dirt: Kelly Goldberg
No full textWhen USC\u27s historic Horseshoe underwent major renovations in the 1970s, a series of archaeological digs uncovered 19th century water wells and other artifacts from a bygone era. Now Kelly Goldberg, an Honors College instructor of archaeology, is leading a series of excavations with students on the Horseshoe to find more artifacts that help tell the story of USC\u27s past.https://scholarcommons.sc.edu/rememberingthedays/1092/thumbnail.jp
Social Support and Gratitude in Adolescents: An Exploratory Study
No full textDispositional gratitude is a construct associated with numerous benefits in youth. However, existing research has primarily focused on the outcomes of gratitude, with limited exploration of the underlying factors that may contribute to individual differences in its development. Because gratitude is considered malleable, identifying key factors associated with its growth in youth is essential. The present study aims to address this gap by exploring perceived social support as a presumed antecedent of dispositional gratitude in older adolescents. Cross-sectional, self-report data and structural equation modeling were used to assess the relationship of perceived social support with gratitude levels among high school students. Recognizing the multidimensional nature of social support, the study investigated specific sources (i.e., caregivers, teachers, and classmates), specific types (i.e., emotional, informational, appraisal, and instrumental), and their intersections. Findings revealed that all sources and types of social support contributed significantly to individual differences in gratitude, with emotional support from caregivers emerging as the form of support that explained the most variance in adolescents’ grateful dispositions. Additionally, sex moderated these relationships, highlighting distinct patterns in how males and females perceive and benefit from social support in relation to gratitude. These findings emphasize the significant link of social support to the grateful dispositions of older adolescents. Future longitudinal research should investigate additional antecedents of gratitude to refine theoretical models and inform targeted interventions to effectively cultivate and enhance gratitude in youth
Choice Overload in the Digital Age: A Cognitive Neuroscience Approach
No full textThis dissertation examines the neural mechanisms of value-based multiattribute decision making through the lens of choice overload during consumer choice. Two behavioral experiments established that choice sets of a moderate size with nine options were perceived as most optimal compared to choice sets with three and 24 options, and options chosen from the largest set size were judged to be the least satisfying. A functional MRI study then examined how the brain responds to choice sets varying in size and complexity by manipulating the number of options presented as well as the presence of asymmetrically dominated decoy alternatives during a simulated online shopping task. Results showed that the dorsolateral prefrontal cortex (DLPFC) activity followed an inverse U-shape as a function of choice set size, peaking for moderately sized choice sets. The anterior cingulate cortex (ACC) exhibited a linear trend with choice set size. Trials containing decoy options elicited greater activation of the anterior insula (AIns) and DLPFC. Computational modeling of choice behavior revealed a greater tendency to utilize a simplifying lexicographic decision strategy as decision difficulty increased, and individual differences in decision strategies were reflected in activity of the ACC and AIns. These findings advance understanding of how the brain integrates effort, control, and strategy during complex value-based decisions
Tennyson & Contemporary Science: Herschel’s Preliminary Discourse, A Book That Got Away
No full textDiscusses the rediscovery, provenance, and authenticity of the copy of John Herschel\u27s Preliminary Discourse on the Study of Natural Philosophy (1831), with an ownership inscription by Tennyson dated 1843, and marginal markings on multiple pages, that was previously only known from a brief catalogue description for a 1924 auction
Flux-Assisted Boron Chalcogen Mixture (BCM) Method for Synthesizing Mixed Chalcogenide Semiconductors (AkRE\u3csub\u3e2\u3c/sub\u3e Si\u3csub\u3e2\u3c/sub\u3e Se\u3csub\u3ex\u3c/sub\u3eS\u3csub\u3e8–x\u3c/sub\u3e and CaRE\u3csub\u3e2\u3c/sub\u3e Si\u3csub\u3e2\u3c/sub\u3e Se\u3csub\u3e8\u3c/sub\u3e) (\u3ci\u3e Ak\u3c/i\u3e = Ca and Sr; \u3ci\u3e RE\u3c/i\u3e = La, Ce, Pr, Nd, and Sm): Investigation of Their Magnetic and Optical Properties
No full textWe report a detailed structural analysis of a series of ten quaternary rare earth-containing seleno-thiosilicates AkRE2Si2SexS8–xand selenosilicates, CaRE2Si2Se8(Ak = Ca and Sr; RE = La, Ce, Pr, Nd, and Sm). Single crystals were obtained by using the flux-assisted boron chalcogen mixture (BCM) method, and single-crystal X-ray diffraction was used to determine their structures. All members of the AkRE2Si2SexS8–xand CaRE2Si2Se8series crystallize in the space group R3̅c (space group number 167) of the trigonal crystal system. The single-crystal X-ray diffraction analysis revealed a strong preference for Se/S atoms to occupy one vs the other of the two available sites. Polycrystalline samples were used for the magnetic susceptibility and UV–visible diffuse reflectance measurements. Magnetic measurements show that CaCe2Si2Se1.73S6.27and CaNd2Si2Se2.5S5.5are paramagnetic with negative Weiss constants (θ = −60.1 and −26.2). Diffuse reflectance analysis gives optical band gaps of 2.7(1) eV (CaLa2Si2Se2.38S5.62), 2.2(1) eV (CaCe2Si2Se1.73S6.27), 2.5(1) eV (CaNd2Si2Se2.5S5.5), and 2.0(1) eV (CaCe2Si2Se8), consistent with density functional theory calculations. By partially or fully replacing S sites with Se, it was possible to achieve band gap tuning. Photoluminescence behavior was also investigated for CaCe2Si2Se1.73S6.27via irradiation with 375 nm ultraviolet light
Online Cyber-Physical Neural Network Model for Real-Time Hybrid Simulation
No full textReal-time hybrid simulation (RTHS) is an experimental testing methodology that divides a structural system into an analyticaland an experimental substructure. The analytical substructure is modeled numerically, and the experimental substructure ismodeled physically in the laboratory. The two substructures are kinematically linked together at their interface degrees of freedom,and the coupled equations of motion are solved in real-time to obtain the response of the complete system. A key challenge inapplying RTHS to large or complex structures is the limited availability of physical devices, which makes it difficult to representall required experimental components simultaneously. The present study addresses this challenge by introducing Online Cyber-Physical Neural Network (OCP-NN) models–neural network-based models of physical devices that are integrated in real-timewith the experimental substructure during an RTHS. The OCP-NN framework leverages real-time data from a single physicaldevice (i.e., the experimental substructure) to replicate its behavior at other locations in the system, thereby significantly reducingthe need for multiple physical devices. The proposed method is demonstrated through RTHS of a two-story reinforced concreteframe subjected to seismic excitation and equipped with Banded Rotary Friction Dampers (BRFDs) in each story. BRFDs arechallenging to model numerically due to their complex behavior which includes backlash, stick-slip phenomena, and inherentdevice dynamics. Consequently, BRFDs were selected to demonstrate the proposed framework. In the RTHS, one BRFD is modeledphysically by the experimental substructure, while the other is represented by the OCP-NN model. The results indicate thatthe OCP-NN model can accurately capture the behavior of the device in real-time. This approach offers a practical solution forimproving RTHS of complex structural systems with limited experimental resources
Augmented, Not Replaced: The Impact of AI on Equity Research Analysts
Get PDFThe adoption of AI tools into professional workflows has the chance to revolutionize major industries such as the financial services industry. Because equity research is a space that is heavily dependent on data aggregation, forecasting, and report generation, there is a threat of AI replacing human analysts in the next five years. The goal of this study is to determine how the adoption of AI tools will affect the equity research career field. To achieve this goal, a mixed-method approach is employed through a quantitative and qualitative survey. Results from the survey indicate that most finance professionals are already using AI tools in their workflows which leads to increased job satisfaction and time savings. Although many professionals believe AI will eventually perform certain research analyst tasks such as data aggregation and report generation, few see these careers fully being replaced in the next five years. To help augment and improve the career field in the short term, firms can increase investment in AI training for their employees which would increase analyst productivity, job satisfaction, and please investors all without replacing human analysts