Bulletin of the American Physical Society
Graduate Education & Bridge Program Conference
Friday–Sunday, February 10–12, 2017; College Park, Maryland
Session PS2: Poster Session: Graduate Student Research (4:30pm - 6pm) |
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Room: Cheaspeake Foyer |
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PS2.00001: Method to measure the dielectric constant and tangent loss of solids and liquids in the microwave region of the electromagnetic spectrum Gabriel Jurado, Thierry Dubroca, Johannes McKay, Stephen Hill There is a long standing interest in characterizing the dielectric properties of solids and liquids over the full breadth of the microwave spectrum. For example, various solvents are used in solution state Dynamic Nuclear Polarization (DNP) and the time scale of the experiment depends on the physical properties of the solvent, it is therefore relevant to have the properties of the solvents fully characterized. The ratio of transmitted power over incident power yields a relationship between frequency, index of refraction, tangent loss, and dielectric constant. A model was developed to evaluate the dielectric properties, $\epsilon$ and $tan\delta$, of a slab of Rexolite, Polypropylene, and Hexane using literature values for Teflon and Quartz. The ratio of transmitted power over incident power is plotted vs frequency and a differential evolution minimization technique best fits to the FFT of the raw data, and the appropriate values for $\epsilon$ and $tan\delta$ are extracted. The model and technique are demonstrated at (80-110)GHz for practical reasons however they can be used over various frequency ranges and for multiple layers of dielectric material. The model and experiment described reliably reproduced literature results for dielectric properties of solids and liquids. [Preview Abstract] |
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PS2.00002: Enhanced Optical and Electrical Properties of Polymer-Assisted All-Inorganic Perovskites for Light-Emitting Diodes Javon Knox Highly bright light-emitting diodes~based on solution-processed all-inorganic perovskite thin film are demonstrated. The cesium lead bromide (CsPbBr$_{\mathrm{3}})$ created using a new poly(ethylene oxide)-additive spin-coating method exhibits photoluminescence quantum yield up to 60{\%} and excellent uniformity of electrical current distribution. Using the smooth CsPbBr$_{\mathrm{3}}$~films as emitting layers, green perovskite-based light-emitting diodes (PeLEDs) exhibit electroluminescent brightness and efficiency above 53 000 cd m$^{\mathrm{-2}}$~and 4{\%}: a new benchmark of device performance for all-inorganic PeLEDs. [Preview Abstract] |
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PS2.00003: The Impact of Situational Factors on Attitudes about Physics Brian Zamarripa Roman, Jacquelyn Chini Attitudinal assessments in physics have been developed to probe what students believe about physics and learning physics. Both pre-instruction assessment scores and the change in those scores as a result of instruction (gains) been shown to be affected by factors such as student gender, previous experience with physics, and type of math required in the physics course. In this investigation we examine the Colorado Learning Attitudes about Science Survey to determine the effect of situational factors on assessment scores and gains. The effects of situational factors such as income and parent college experience were tested through statistical analysis of scores gathered throughout five semesters of introductory physics courses. [Preview Abstract] |
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PS2.00004: Oxidation Effects on the Magnetic Properties of Iron (II) Phthalocyanine Thin Films Leslie Davis, Thomas Gredig Phthalocyanine is an aromatic organic molecule at the core of a wide range of applications such as gas sensors and pigment dyes. The study of iron (II) phthalocyanine (FePc) morphology, charge transport, optical and magnetic properties improve the quality of these devices. Using thermal evaporation in a high vacuum, 200 nm of FePc are grown on silicon substrates varying the deposition temperature from room temperature to 200$^{\circ}$C. The vibrating sample magnetometer is used in conjunction with the physical property measurement system to measure the magnetic properties of the FePc thin films. Iron is known to oxidize after exposure to atmosphere. This process leads to changes in the magnetic properties, which are tracked over a time span of over five years. In FePc thin films, the coercivity depends on crystal size controlled via the deposition temperature. If the oxidation degradation process is a surface effect, then a reduction of the net magnetization signal is expected, while coercivity remains constant. A decrease in the saturation magnetization in FePc thin films over time is observed and coercivity remains unaffected. From this analysis, we conclude that atmospheric exposure impacts the magnetic properties of the layers closest to the surface. [Preview Abstract] |
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PS2.00005: Layer Dependent Raman Spectroscopy of FePS$_{\mathrm{3}}$ Juan Macy, Luis Balicas Metal Phosphorous Trichalcogenides are a group of compounds that are intrinsically magnetic, and exhibit wide range band gaps. Out of this family of compounds, we have found that Iron Phosophorous Trichalcogenides (FePS$_{\mathrm{3}})$ have shown environmental stability down to the monolayer limit. It has been shown that exfoliating these compounds down to a few atomic layers leads to emergent properties that differ from the bulk e.g. different band gaps, which have yet to be explored for these materials. However, it remains unclear how its magnetic phase transition is affected by the exfoliation process or if it survives down to the single layer limit. Thus, our goal is to examine the structural and magnetic stability of FePS$_{\mathrm{3}}$ when exfoliated down to a few atomic layers through the evolution of its Raman spectra. [Preview Abstract] |
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PS2.00006: Study of Bulk and Surface Conduction in Alloys of Samarium Hexaboride Juniar Lucien, Yun Suk Eo, Cagliyan Kurdak, Dmitri Mihaliov Recent conjecture of topologically-protected surface state in samarium hexaboride (SmB$_{\mathrm{6}})$ and the verification of robust surface conduction below 4 K have led to a large effort to understand this material. Transport properties of SmB$_{\mathrm{6}}$ can be altered by introducing either vacancies or substitutional atoms. Previous studies indicate the material would still exhibit an activated behavior as well as a robust low temperature resistance plateau in the dilute-doped samples. In some cases, the resistance plateau value is a few orders of magnitude lower than that of pure SmB$_{\mathrm{6}}$. This is very difficult to explain with the topological insulator framework, because the increased disorder would normally result in a lower mobility, and therefore a lower conductivity. In order to resolve this issue, we have studied samples with vacancies and samples with La substitution using a double-sided Corbino geometry, which allowed us to extract temperature dependent surface and bulk conductivities. For a sample with 25{\%} vacancy in the Sm site, we found the bulk to be truly insulating and the surface conductivity to be similar to that of pure SmB$_{\mathrm{6}}$, which is inconsistent with previous reports. [Preview Abstract] |
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PS2.00007: Uniform wafer-scale growth of stencil templated, high-quality monolayer MoS2 Ethel Perez-Hoyos, Justin Young, Michael Chilcote, Matthew Barone, Sara Mueller, Roland Kawakami, Ezekiel Johnston-Halperin With the widespread interest in transition metal dichalcogenides and the recent focus on two-dimensional (2D) vertically stacked heterostructures, a need for an inexpensive and reliable method of producing clean, high-quality, patterned 2D materials has emerged. Here, we report on a templated MoS2 growth technique by metal sulfurization where Mo is deposited through a SiN stencil onto highly-crystalline sapphire substrates. After sulfurization, the resulting MoS2 films are shown to be high-quality with thicknesses that can be tuned layer-by-layer---down to a single layer---through manipulation of the initial Mo deposition time. The quality of these films is confirmed through scanning electron and atomic force microscopies as well as Raman and photoluminescence spectroscopy. This facile growth technique results in templated, high-quality MoS2 films with centimeter-scale uniformity, feature sizes down to 100 nm, and offers both a means to easily probe MoS2 growth dynamics and a route to 2D stacked heterostructures with arbitrary geometry and pristine interfaces. We will discuss potential applications of this novel growth technique for the development of TMD heterostructures and alloys. [Preview Abstract] |
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PS2.00008: NIF laboratory astrophysics simulations investigating the effects of a radiative shock on hydrodynamic instabilities Adrianna Angulo This poster will describe simulations based on results from ongoing laboratory astrophysics experiments at the National Ignition Facility (NIF) relevant to the effects of radiative shock on hydrodynamically unstable surfaces. The experiments performed on NIF uniquely provide the necessary conditions required to emulate radiative shock that occurs in astrophysical systems. The core-collapse explosions of red supergiant stars is such an example wherein the interaction between the supernova ejecta and the circumstellar medium creates a region susceptible to Rayleigh-Taylor (R-T) instabilities. Radiative and nonradiative experiments were performed to show that R-T growth should be reduced by the effects of the radiative shocks that occur during this core-collapse. Simulations were performed using the radiation hydrodynamics code Hyades using the experimental conditions to find the mean interface acceleration of the instability and then further analyzed in the buoyancy drag model to observe how the material expansion contributes to the mix-layer growth. [Preview Abstract] |
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PS2.00009: Compound Array for Transfer Reactions in Nuclear Astrophysics (CATRiNA) J.F. Perello, S. Almraz-Calderon, B.W. Asher, K. Hanselman, P. Barber Deuterated-benzene scintillators have shown promising capabilities for neutron spectroscopy studies without time-of-flight (ToF). At Florida State University (FSU), we are working on the development of the Compound Array for Transfer Reactions in Nuclear Astrophysics (CATRiNA) using an array of 16 deuterated liquid scintillator detectors. The pulse-shape discrimination capabilities of the detectors allow us to distinguish between n/$\gamma$ interactions. Moreover, the backward-peaked n–d scattering result in a strong correlation between the incident neutron energy and the measured pulse height of the events. CATRiNA is envisioned to measure several reactions relevant for nuclear structure and nuclear astrophysics studies. In this work, we provide preliminary results on the characterization of the detectors using neutrons coming from a 252-Cf source and from a series of in-beam experiments using the 7Li(p,n) reaction. [Preview Abstract] |
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PS2.00010: Computational study of ideal electrolyte/anode interfaces for Na3SbS4/Na Larry E. Rush Jr., N.A.W. Holzwarth As part of an effort to develop energy storage technology based on Na-ion batteries, recent papers in the literature\footnote{Wang {\em{et al.}}, {\bf{Angew. Chem. Int. Ed. 55}}, 8551–8555 (2016), Zhang {\em{et al.}}, {\bf{Adv. Sci. 2016}}, 1600089 (2016)} demonstrate the electrochemical stability of the solid electrolyte Na$_3$SbS$_4$ interfaced with a metallic Na anode. The integrity of this electrolyte/anode interface, which is essential to the success of these battery components, is attributed to the formation of a stable solid-electrolyte interphase (SSEI). We report the results of a computational study of this system, using first-principles methods to model ideal interfaces of Na$_3$SbS$_4$ with Na metal. The ideal interfaces were constructed from (110), (100), and (001) surfaces of tetragonal crystals of Na$_3$SbS$_4$ and Na metal in various configurations. The results show several likely components of the SSEI including a few broken Sb$-$S bonds and Na$_2$S groups stabilized at the outer layer of the interface. [Preview Abstract] |
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PS2.00011: Landau Level Mixing Effects in the Graphene Fractional Quantum Hall Effect Yonas Getachew, Michael Peterson A two-dimensional electron system exposed to a strong perpendicular magnetic field at low temperatures forms a new state of matter that exhibits the fractional quantum Hall effect (FQHE). This phenomenon has been observed in graphene, a naturally occurring two-dimensional electron system. The nature of the FQHE state has remained ambiguous primarily because electrons in graphene have spin as well as valley degrees of freedom. As a result, the different single-particle energy levels (Landau levels) of the electrons can mix with each other. This Landau level mixing (LLM) is intrinsic to graphene and must be considered in any realistic theoretical treatment. Recently, an effective model Hamiltonian which includes LLM has been formulated in terms of Haldane pseudopotentials: this model includes emergent three-body interactions in addition to renormalizing the two-body interactions. We construct a real-space two-body interaction potential using a closed form expression found in the literature. We then use this case to benchmark our results with the pseudopotential method and extend it to include three-body interactions. [Preview Abstract] |
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PS2.00012: General Relativistic Non-radial Oscillations of Compact Stars Zack Hall, II, Prashanth Jaikumar Currently, we lack a means of identifying the type of matter at the core of compact stars, but in the future, we may be able to use gravitational wave signals produced by fluid oscillations inside compact stars to discover new phases of dense matter. To this end, we study the fluid perturbations inside compact stars such as Neutron Stars and Strange Quark Stars, focusing on modes that couple to gravitational waves. Using a modern equation of state for quark matter that incorporates interactions at moderately high densities, we implement an efficient computational scheme to solve the oscillation equations in the framework of General Relativity, and determine the complex eigenfrequencies that describe the oscillation and damping of the non-radial fluid modes. We discuss the significance of our results for future detection of these modes through gravitational waves. [Preview Abstract] |
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PS2.00013: Biocompatible gold/silver nanostars for surface-enhanced Raman scattering Andre Childs, Ekaterina Vinogradova, Francisco Ruiz-Zepeda, J. Jesus Velazquez-Salazar, Miguel Jose-Yacaman Surface-Enhanced Raman Spectroscopy (SERS) is a tool used to explore the vibrational properties of the molecules with many impending applications in the bioscience field. In this experiment SERS was used to study of the surface adsorption and detection of a dye Rhodamine 6G (R6G), a biomolecule Bovine Serum Albumin (BSA), and a human pathogen Chlamydia trachomatis (CPAF). The goal is to evaluate the Raman enhancing properties of star-shaped gold/silver nanostars (Au/Ag Nps). We choose this particular morphology because it has been experimentally observed that nanostars display stronger SERS activity than nanoparticles with different shapes due to their anisotropic distribution. The nanoparticles were synthesized through a solution-based growth method mediated by silver seeds that are used as the nucleating agent for anisotropic growth of gold colloids. The characterization of the Au/Ag NPs was done by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and UV-visible spectroscopy. Finally we will present the SERS spectra obtained for R6G, BSA, and CPAF in presence of Au/AgNPs. We will also discuss the potential of chitosan-coated SERS-active nanostars for biomedical imaging tools. [Preview Abstract] |
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PS2.00014: Unphysical phases in staggered chiral perturbation theory George Davila Lattice QCD is the field of study in which spacetime is discretized onto a lattice of dimension a in order to obtain theoretical and numerical results. Staggered chiral perturbation theory is a method of placing fermions on a spacetime lattice. We examine various phases of this theory for staggered quarks. In beyond-the-standard-model simulations using a large number (\textgreater 8) of staggered fermions, unphysical phases appear for coarse enough lattice spacing. At least one of these phases can be explained in the context of staggered chiral perturbation theory. For lattice spacings in the regime a\textasciicircum 2$\ll (\Lambda $QCD)\textasciicircum 2, we show that only three broken phases for staggered fermions exist. [Preview Abstract] |
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PS2.00015: Exploring the mechanisms of image formation in nanoscale subsurface imaging with Atomic Force Microscopy Fernand Torres Davila, Mikhael Soliman, Yvon Lacroute, Laurene Tetard Multi-frequency Atomic Force Microscopy (AFM) is emerging as a powerful platform for non-destructive subsurface imaging with nanoscale spatial resolution -- lateral and depth resolution. A combination of AFM and acoustic imaging has been explored to probe the volume of heterogeneous samples but the approach lacks quantitative interpretation of the depth at which structures are buried. Here we designed a set of samples composed of a 80 nm layer of Ni embedded between layers of Au of different thicknesses. These layers are in the range from 50 nm to 200 nm. These samples were prepared to determine the effect of depth on acoustic wave propagation in the sample, and on the resonance frequencies of the AFM cantilever used for imaging. The frequency and amplitude spectra acquired indicate that the position of the Ni layer in the volume (or depth) of the sample greatly impacts the signals measured by acoustic AFM. Significant frequency shifts could be observed, with great impact on the image formation previously reported in the literature. Our results pave the way to a deeper understanding of the processes of image formation for nanoscale subsurface imaging. [Preview Abstract] |
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PS2.00016: Lifetime measurements to constrain the $^{30}$P($p,\gamma$)$^{31}$S rate at classical nova temperatures Cathleen Fry Classical novae occur in binary star systems, where a white dwarf accretes hydrogen rich material from its companion star until it ignites in thermonuclear runaway. In this explosive scenario, the $^{30}$P($p,\gamma$)$^{31}$S reaction potentially acts as a bottleneck in nucleosynthesis flow to higher masses. Knowledge of this reaction rate is necessary for the modeling of elemental and isotopic ratios in classical novae, which affect proposed nova thermometers and presolar grain identification, respectively. This reaction rate is dominated by resonant capture, and while most of the resonance energies are known experimentally, the corresponding resonance strengths are not yet known. A measurement of the lifetimes of these states would provide the total widths of these resonances, and can be used along with the spins and proton branching ratios to determine resonance strengths. As a step towards determining experimental resonance strengths, we recently ran an experiment to measure the lifetimes of these resonances, using the Doppler Shift Lifetime (DSL) setup at TRIUMF. Challenges from this preliminary measurement and future plans will be discussed. [Preview Abstract] |
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PS2.00017: Probing MeV Scale Physics in LArTPCs with Radioactive Calibration Sources Jonathan Echevers The Liquid Argon Time Projection chamber (LArTPC) is a unique technology well suited for large scale neutrino detectors. They allow for millimeter scale 3D precision particle tracking and calorimetry with good $\frac{dE}{dx} $ resolution, which provides excellent efficiency of particle identification and background rejection. While studies of detector response to high energy events have begun, there has been little to no direct demonstration of LArTPCs’ capabilities in producing ground breaking physics with solar and supernovae low-energy neutrinos. We aim to facilitate the development of low-energy LArTPC capabilities by developing the first 1-10 MeV calibration subsystems for large LArTPCs. In this talk, I will introduce the properties of supernova neutrinos, discuss how they can be detected in LArTPCs, and overview the low-energy LArTPC calibration source conceptual designs we are developing at IIT. [Preview Abstract] |
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PS2.00018: Polymer–inorganic nano-composite thin film upconversion light emitters prepared by double-beam matrix assisted pulsed laser evaporation (DB-MAPLE) method Ashley blackwell The objective of the work is to demonstrate feasibility of producing functional polymer nano-composite films for light emitting applications using the new double beam pulsed laser deposition (DPLD) technique. The existing pulsed laser deposition vacuum chamber has been modified to accommodate two laser beams of different wavelengths for the in-situ ablation of two targets: a polymer host and a rare earth based highly efficient upconversion emitting inorganic dopant. Special provisions were made for cooling the target to control the ablation of the polymer without interrupting the process. Nano-composite films of acrylic polymer and nano-particles of the compounds of the rare earth elements were fabricated by the proposed method with near-infra-red laser radiation (1064-nm wavelength) ablating the polymer targets and visible radiation (532 nm) ablating the inorganic targets. The fabricated nano-composite films were characterized using atomic force microscopy, X-ray diffraction, optical fluorescence spectroscopy, and visual observation of the fluorescence. It was discovered that the produced polymer nano-composite films retained the crystalline structure and the upconversion fluorescence properties of the initial rare earth compounds mainly due to the better control of the depositi [Preview Abstract] |
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