College of Science and Engineering
Permanent URI for this collectionhttps://hdl.handle.net/10877/17053
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Browsing College of Science and Engineering by Department "Physics"
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Item Abe Lincoln and the Leonids(Sky Publishing Corp., 1999-11) Jasinski, Laurie E.; Olson, Donald W.No abstract prepared.Item An Ansel Adams Encore(Sky Publishing Corp., 2006-01) Sinnott, Roger W.; Olson, Donald W.; Doescher, Russell L.Scores of camera enthusiasts show up at Glacier Point for a celestial scene captured 57 years earlier.Item An IRTF-iSHELL Survey of 4.52–5.25 μm CO Spectra in Protoplanetary Disks of Intermediate-mass Stars: Preliminary Sample and Analysis(American Astronomical Society, 2021-04) Abernathy, Kirsten M.; Banzatti, Andrea; Jensen, Stanley; Brittain, Sean; Boogert, Adwin; Rayner, John; Bruderer, SimonWe are conducting a survey of high-resolution near-infrared CO rovibrational spectra in protoplanetary disks around young intermediate-mass stars. We use IRTF-iSHELL with the 0.″375 and 0.″75 slits, providing 4 km s−1 and 6 km s−1 resolution and covering 4.52–5.25 μm in one single exposure. This includes part of the rovibrational R branch and most of the P branch of the CO fundamental band (Δv = 1), one of the best tracers of warm/hot gas in disks. The high quality of the spectra and the large sample covered in this survey will support multiple investigations to study the structure, kinematics, composition, and evolution of the inner 10 au in disks for years to come. The survey currently includes ∼30 stars mostly within 200 pc, complementing extensive imaging campaigns that are observing their disks at optical, infrared, and millimeter wavelengths and revealing structures and planets.Item Ansel Adams "An Autumn Moon"(Sky Publishing Corp., 2005-10) Olson, Donald W.; Doescher, Russell L.No abstract prepared.Item Athermal Annealing of Low-energy Boron Implants in Silicon(American Institute of Physics, 2001-04-02) Donnelly, David W.; Covington, Billy C.; Grun, J.; Fischer, R.P.; Peckerar, M.; Felix, C. L.Silicon samples that have been ion implanted with boron at energies below 3 keV have been athermally annealed. The annealing process has been characterized using secondary ion mass spectrometry and infrared absorption spectroscopy. The athermally annealed samples show activation comparable to that for thermally annealed samples, but with much less boron diffusion. The activation is the athermally annealed samples is shown to be much higher than would be achieved by recrystallization of the amorphous layer.Item Athermal Annealing of Phosphorus-Ion-Implanted Silicon(American Institute of Physics, 2000-09-25) Grun, J.; Fischer, R. P.; Peckerar, M.; Felix, C. L.; Covington, Billy C.; DeSisto, W. J.; Donnelly, David W.; Ting, A.; Manka, C. K.A 1 cm2 area in phosphorus-implanted silicon samples in annealed by irradiation of a much smaller 0.002 cm2 area with a single laser pulse. Resistivity of the annealed region is uniform and similar to that measured after thermal annealing. Electrically activated donors did not diffuse into the sample and only slightly towards the sample surface. The process is 100% reproducible. We present evidence that the annealing is not caused by heat.Item Athermal Annealing of Silicon(American Physical Society, 1997-02-24) Grun, J.; Manka, C. K.; Hoffman, Carl A.; Meyer, J. R.; Glembocki, O. J.; Kaplan, R.; Qadri, S. B.; Skelton, E F.; Donnelly, David W.; Covington, Billy C.We demonstrate a new mechanism for annealing silicon that does not involve the direct application of heat as in conventional thermal annealing or pulsed laser annealing. A laser pulse focused to high power on a small surface spot of a neutron-transmutation-doped silicon slab is shown to anneal regions far outside the illuminated spot where no heat was directly deposited. Electrical activation of donors throughout the slab was uniform and comparable to that of thermally annealed control samples. We conjecture that the annealing was caused by mechanical energy introduced by the laser pulse. This new method may provide a viable alternative for annealing semiconductors or other materials.Item Becoming Physics People: Development of Integrated Physics Identity through the Learning Assistant Experience(American Physical Society, 2016-02-22) Close, Eleanor; Conn, Jessica; Close, Hunter G.[This paper is part of the Focused Collection on Preparing and Supporting University Physics Educators.] In this study, we analyze the experience of students in the Physics Learning Assistant (LA) program at Texas State University in terms of the existing theoretical frameworks of community of practice and physics identity, and explore the implications suggested by these theories for LA program adoption and adaptation. Regression models from physics identity studies show that the physics identity construct strongly predicts intended choice of a career in physics. The goal of our current project is to understand the details of the impacts of participation in the LA experience on participants’ practice and self-concept, in order to identify critical elements of LA program structure that positively influence physics identity and physics career intentions for students. Our analysis suggests that participation in the LA program impacts LAs in ways that support both stronger “physics student” identity and stronger “physics instructor” identity, and that these identities are reconciled into a coherent integrated physics identity. Increased comfort in interactions with peers, near peers, and faculty seems to be an important component of this identity development and reconciliation, suggesting that a focus on supporting community membership is useful for effective program design.Item Blue-Moon Mystery Solved?(Sky Publishing Corp., 1999-03) Olson, Donald W.; Sinnott, Roger W.No abstract prepared.Item Caesar's Invasion of Britain(Sky Publishing Corp., 2008-08) Olson, Donald W.; Doescher, Russell L.No abstract prepared.Item California Surprise: A California Observation of the 1833 Leonid Meteor Storm(Griffith Observatory, 1999-11) Olson, Donald W.; Doescher, Russell L.The most recent reassessments of last year's Leonid meteor activity have persuaded pilgrims seeking the legendary Leonid storm to expect a true meteoric spectacle on its usual 33-year beat sometime between 16 and 18 November. Serious money is on the eastern Atlantic Ocean and western Europe for the most intense celestial pyrotechnics, but these projections still depend on a lot of guesswork. No Leonids are as legendary as the 1833 firefall, which was seen and documented over much of the territory east of the Mississippi. Because reports from the Far West are not well known, most modern accounts conclude the event was geographically restricted. Here, however, a pair of professors at Southwest Texas State University demonstrate the fallacy of common knowledge and provide a previously unrecognized account of California fireworks.Item Challenges of Contact Module Integration for GaN-based Devices in a Si-CMOS Environment(AIP Publishing, 2014-05-23) Johnson, Derek W.; Ravikirthi, Pradhyumna; Suh, Jae Woo; Lee, Rinus T. P.; Hill, Richard J. W.; Wong, Man Hoi; Piner, Edwin L.; Harris, Harlan RustyThe authors report on the integration of an Au-free contact module intended for AlGaN/GaN high-electron-mobility transistors fabricated in a 200 mm Si complementary metal–oxide–semiconductor facility. Contacts are characterized via transfer line method structures, tunneling electron microscopy, and energy-dispersive x-ray spectroscopy. Factors leading to incorrect extraction of contact resistance are discussed. The authors find that reoptimization of chemical vapor deposited silicon nitride on AlGaN/GaN substrates is required to ensure reliable determination of contact resistance, gate-to-source spacing, and gate-to-drain spacing. Additional process development is required to enable parallel processing of Si and GaN devices.Item Constraining the Nuclear Equation of State via Gravitational-wave Radiation of Short Gamma-Ray Burst Remnants(The American Astronomical Society, 2020-02) Lan, Lin; Lu, Hou-Jun; Rice, Jared; Liang, En-WeiThe observed internal plateau of X-ray emission in some short gamma-ray bursts (GRBs) suggests the formation of a remnant supramassive magnetar following a double neutron star (NS) merger. In this paper, we assume that the rotational energy is lost mainly via gravitational-wave (GW) radiation instead of magnetic dipole (MD) radiation, and present further constraints on the NS nuclear equation of state (EoS) via mass quadrupole deformation and r -mode fluid oscillations of the magnetar. We present two short GRBs with measured redshifts, 101219A and 160821B, whose X-ray light curves exhibit an internal plateau. This suggests that a supramassive NS may survive as the central engine. By considering 12 NS EoSs, within the mass quadrupole deformation scenario we find that the GM1, DD2, and DDME2 models give an Mp band falling within the 2σ region of the proto-magnetar mass distribution for ε = 0.01. This is consistent with the constraints from the MD radiation dominated model of rotational energy loss. However, for an r -mode fluid oscillation model with α = 0.1 the data suggest that the NS EOS is close to the Shen and APR models, which is obviously different from the MD radiation dominated and mass quadrupole deformation cases.Item Continuous Tuning of W-doped VO2 Optical Properties for Terahertz Analog Applications(American Institute of Physics, 2014-11-17) Karaoglan-Bebek, Gulten; Hoque, M. N. F.; Holtz, Mark; Fan, Zhaoyang; Bernussi, AyrtonVanadium dioxide (VO2), with its characteristic metal-insulator phase transition, is a prospective active candidate to realize tunable optical devices operating at terahertz (THz) frequencies. However, the abrupt phase transition restricts its practical use in analog-like continuous applications. Incorporation of tungsten is a feasible approach to alter the phase transition properties of thin VO2 films. We show that amplitude THz modulation depth of ~65%, characteristic phase transition temperature of ~40 0C, and tuning range larger than 35 0C can be achieved with W-doped VO2 films grown on sapphire substrates. W-doped VO2 films can also be used to suppress Fabry-Perot resonances at THz frequencies but at temperatures much lower than that observed for undoped VO2 films. The gradual phase transition temperature window allows for precise control of the W-doped VO2 optical properties for future analog based THz devices.Item Control of InGaAs and InAs Facets Using Metal Modulation Epitaxy(American Vacuum Society, 2015-01-06) Wistey, Mark A.; Baraskar, Ashish K.; Singisetti, Uttam; Burek, Greg J.; Shin, Byungha; Kim, Eunji; McIntyre, Paul C.; Gossard, Arthur C.; Rodwell, Mark J. W.Control of faceting during epitaxy is critical for nanoscale devices. This work identifies the origins of gaps and different facets during regrowth of InGaAs and InAs adjacent to patterned features. Molecular beam epitaxy near SiO2 or SiNx led to gaps, roughness, or polycrystalline growth, but low-arsenic metal modulated epitaxy produced smooth and gap-free (001) planar growth up to the gate. The resulting self-aligned field effect transistors (FETs) were dominated by FET channel resistance rather than source–drain access resistance. Higher As2 fluxes led first to conformal growth, then pronounced {111} facets sloping up away from the mask.Item D-Day: June 6, 1944(Sky Publishing Corp., 1994-06) Olson, Donald W.; Doescher, Russell L.In this article Donald Olson and Russell Doescher explain why the advancing tide on D-day in 1944, rising as swiftly as a foot every 10 minutes, drove many Allied demolition teams toward the sea wall before they were able to clear gaps through German obstacles in Omaha Beach. As a result, the early assault waves had to slog forward through mined stakes, ramps, and "hedgehogs," as portrayed in this still photograph from 'The Longest Day,' the classic 1962 film about the Normandy invasion.Item Dating Ansel Adams's "Moon and Half Dome"(Sky Publishing Corp., 1994-12) Olson, Donald W.; Doescher, Russell L.; Burke, Amanda K.; Delgado, Mario E.; Douglas, Marillyn A.; Fields, Kevin L.; Fischer, Robert B.; Gardiner, Patricia D.; Huntley, Thomas W.; McCarthy, Kellie E.; Messenger, Amber G.ON A COLD and clear winter afternoon some three decades ago, Ansel Adams set up his tripod in Yosemite Valley and focused a Hasselblad camera on the distinctive profile of the mountain known as Half Dome. He waited as the Sun sank closer to the horizon and the long afternoon shadows extended across the granite cliffs. Adams had photographed Half Dome hundreds of times over the years, but on this day he captured an especially remarkable image that included a waxing gibbous Moon rising just north of the monolith. He discussed this photograph in his Autobiography.Item Dating Van Gogh's "Moonrise"(Sky Publishing Corp., 2003-07) Olson, Donald W.; Doescher, Russell L.; Olson, Marilynn S.Art historians have long agreed that Vincent van Gogh painted his spectacular Starry Night between June 16 and 18, 1889, in the town of Saint-Rémy-de-Provence in southern France. Evidence for pinning down the when and where of van Gogh's works comes largely from his own correspondence with his relatives and colleagues. Sometimes there are other clues within the works of art themselves. As astronomers, we have a keen interest when the paintings' subjects include objects in the sky.Previously, we identified Venus as the heavenly object in van Gogh's White House at Night, painted in northern France (S&T: April 2001, page 34). During our research for that project, we became interested in another astronomical painting from Saint-Rémy that had an uncertain date. This painting, known as F735, shows wheat stacks in a field enclosed by a stone wall and, in the twilight sky, a prominent orange disk partly hidden behind a mountain range. Once again, astronomical calculations helped eliminate the ambiguity.
Item Density Functional Theory + U Modeling of Polarons in Organohalide Lead Perovskites(AIP Publishing, 2016-12) Welch, Eric; Scolfaro, Luisa M.; Zakhidov, AlexWe investigate the possible formation of polarons in four organic perovskites (CH3NH3PbI3, CH3NH3PbBr3, CH3NH3PbCl3, and CH3NH3PbI2Cl1) using a density functional theory (DFT) calculations with local potentials and hybrid functionals. We show that DFT+U method with U = 8 eV predicts a correct band-gap and matches the forces on ions from hybrid calculations. We then use the DFT + U approach to study the effect of polarons, i.e. to search the configuration space and locate the lowest energy localized band gap state self-trapped hole (STH). STH configurations were found for three pure halides and one mixed halide system. Spin orbit coupling (SOC) was also taken into account and the results may be found in the supplementary material. This study focuses on the +U method; however, SOC corrections added to the DFT+U calculations also resulted in STH states in all four systems.Item Early Astronomy in Texas(Texas State Historical Association, 1990-01) Evans, David S.; Olson, Donald W.No abstract prepared.