Observation Of Heavy- And Light-Hole Split Direct Bandgap Photoluminescence From Tensile-Strained Gesn (0.03% Sn),
2014
Air Force Institute of Technology
Observation Of Heavy- And Light-Hole Split Direct Bandgap Photoluminescence From Tensile-Strained Gesn (0.03% Sn), Thomas R. Harris, Yung Kee Yeo, Mee-Yi Ryu, Richard T. Beeler, John Kouvetakis
Faculty Publications
Temperature- (T-) and laser power-dependent photoluminescence (PL) measurements have been made for the tensile-strained, undoped GeSn (0.03% Sn) film grown on Si substrate. The PL results show not only clear strain-split direct bandgap transitions to the light-hole (LH) and heavy-hole (HH) bands at energies of 0.827 and 0.851 eV at 10 K, respectively, but also clearly show both strong direct and indirect bandgap related PL emissions at almost all temperatures, which are rarely observed. This split of PL emissions can be directly observed only at low T and moderate laser power, and the two PL peaks merge into one broad …
3d Systems' Technology Overview And New Applications In Manufacturing, Engineering, Science, And Education,
2014
3D Systems Corporation
3d Systems' Technology Overview And New Applications In Manufacturing, Engineering, Science, And Education, Trevor Snyder, Mike Andrews, Mark M. Weislogel, Peter Moeck, Jennifer Stone-Sundberg, Derek Birkes, Madeline Paige Hoffert, Adam Lindeman, Jeff Morrill, Ondrej Fercak, Sasha Friedman, Jeff Gunderson, Anh Ha, Jack Mccollister, Yongkang Chen, John T. Geile, Andrew Paul Wollman, Babek Attari, Nathan Botnen, Vasant Vuppuluri, Jennifer Shim, Werner Kaminsky, Dustin Adams, John Graft
Physics Faculty Publications and Presentations
Since the inception of 3D printing, an evolutionary process has taken place in which specific user and customer needs have crossed paths with the capabilities of a growing number of machines to create value-added businesses. Even today, over 30 years later, the growth of 3D printing and its utilization for the good of society is often limited by the various users' understanding of the technology for their specific needs. This article presents an overview of current 3D printing technologies and shows numerous examples from a multitude of fields from manufacturing to education.
Vibrational Modes In Acoustic Gallery Scanning Probe Microscopy,
2014
Portland State University
Vibrational Modes In Acoustic Gallery Scanning Probe Microscopy, Hsien-Chih Hung, Andres H. La Rosa, Rodolfo Fernandez, Bret Comnes, Richard Nordstrom
Physics Faculty Publications and Presentations
A distinct characteristic in Acoustic Gallery Scanning Probe Microscopy (AG-SPM) constitutes the use of its supporting structural frame as an acoustic resonant cavity for monitoring the nanometer-sized amplitude of its stylus-probe. Although very straightforward in its implementation, its amplitude detection sensitivity could be improved by a more thorough understanding of its working principle mechanism, as well as by a more systematic procedure to attain a closer matching between one of the cavitys acoustic resonances and the probes natural frequency. Herein, a description of the working principle of the AG-SPM is attempted from a vibrationalmode analysis perspective, and a successful specific …
Phase Transitions On Random Lattices: How Random Is Topological Disorder?,
2014
Missouri University of Science and Technology
Phase Transitions On Random Lattices: How Random Is Topological Disorder?, Hatem Barghathi, Thomas Vojta
Physics Faculty Research & Creative Works
We study the effects of topological (connectivity) disorder on phase transitions. We identify a broad class of random lattices whose disorder fluctuations decay much faster with increasing length scale than those of generic random systems, yielding a wandering exponent of ω = (d−1)/(2d) in d dimensions. The stability of clean critical points is thus governed by the criterion (d+1)ν > 2 rather than the usual Harris criterion dν > 2, making topological disorder less relevant than generic randomness. The Imry-Ma criterion is also modified, allowing first-order transitions to survive in all dimensions d > 1. These results explain a host of puzzling violations …
Strong-Disorder Magnetic Quantum Phase Transitions: Status And New Developments,
2014
Missouri University of Science and Technology
Strong-Disorder Magnetic Quantum Phase Transitions: Status And New Developments, Thomas Vojta
Physics Faculty Research & Creative Works
This article reviews the unconventional effects of random disorder on magnetic quantum phase transitions, focusing on a number of new experimental and theoretical developments during the last three years. On the theory side, we address smeared quantum phase transitions tuned by changing the chemical composition, for example in alloys of the type A1-xBx. We also discuss how the interplay of order parameter conservation and overdamped dynamics leads to enhanced quantum Griffiths singularities in disordered metallic ferromagnets. Finally, we discuss a semiclassical theory of transport properties in quantum Griffiths phases. Experimental examples include the ruthenates Sr1-x …
Ferromagnetic Granular Exchange Interactions Of Nickel And Iron,
2014
SUNY Plattsburgh
Ferromagnetic Granular Exchange Interactions Of Nickel And Iron, Ken Podolak
Dr. Ken Podolak
Micromagnetic grains of nickel and iron were blended to investigate whether the magnetic exchange interaction was significant to produce a bulk result in a measured deflection by a fixed applied magnetic field. The results follow the same trend as Slater-Pauling's magnetization density calculations for nickel iron films, most notably a stronger following with a finer grain. Furthermore, by adding chromium into nickel and iron blends, the Invar minimum shifts toward less iron in nickel. Hysteresis was determined for the same samples through a homemade vibrating sample magnetometer (VSM). Areas of each loop are determined that show a minimum around the …
Tensile Gaas(111) Quantum Dashes With Tunable Luminescence Below The Bulk Bandgap,
2014
Boise State University
Tensile Gaas(111) Quantum Dashes With Tunable Luminescence Below The Bulk Bandgap, Paul J. Simmonds
Paul J. Simmonds
Strain-based band engineering in quantum dots and dashes has been predominantly limited to compressively strained systems. However, tensile strain strongly reduces the bandgaps of nanostructures, enabling nanostructures to emit light at lower energies than they could under compressive strain. We demonstrate the self-assembled growth of dislocation-free GaAs quantum dashes on an InP(111)B substrate, using a 3.8% tensile lattice-mismatch. Due to the high tensile strain, the GaAs quantum dashes luminesce at 110–240 meV below the bandgap of bulk GaAs. The emission energy is readily tuned by adjusting the size of the quantum dashes via deposition thickness. Tensile self-assembly creates new opportunities …
Direct Measurement Of The Pp Solar Neutrino Interaction Rate In Borexino,
2014
University of Massachusetts Amherst
Direct Measurement Of The Pp Solar Neutrino Interaction Rate In Borexino, Keith Otis
Doctoral Dissertations
This dissertation presents the first direct detection of pp solar neutrinos within Borexino, the underground liquid-scintilator detector located at the Gran Sasso National Labratory(LNGS) in Italy, designed to measure the interaction of neutrinos through neutrino-electron elastic scattering. The rate of scattering in Borexino from the pp solar neutrino spectrum is measured to be 155 +/- 16(stat) +/- 13(sys) counts per day per 100 tonnes. With this measurement we are able to rule out the no oscillation hypothesis at the 2-sigma C.L. and the results agree with Standard Solar Model predictions within 1.1-sigma. These neutrinos are from the keystone proton-proton fusion …
Morphology Characterization Of Low Band Gap Polymer-Based Organic Photovoltaics,
2014
University of Massachusetts Amherst
Morphology Characterization Of Low Band Gap Polymer-Based Organic Photovoltaics, Feng Liu
Doctoral Dissertations
In bulk heterojunction (BHJ) thin film organic photovoltaics (OPV), morphology control is critical to obtain good device efficiency. Nanoscale phase separation that creates bicontinuous interpenetrating structure on a size scale commensurate with exciton diffusion length (~10 nm) is thought to be the ideal morphology. Results obtained from this work indicate that morphology can be affected by chemical structure of the polymer, processing conditions, blending ratio and post treatments. Physical properties of the material, such as crystallinity, crystal orientation, material interactions and miscibility, surface energy and particle aggregations are critical for determining the morphology and thus the device performance. Previous investigations …
Creasing Instability Of Hydrogels And Elastomers,
2014
University of Massachusetts Amherst
Creasing Instability Of Hydrogels And Elastomers, Dayong Chen
Doctoral Dissertations
CREASING INSTABILITY OF HYDROGELS AND ELASTOMERS MAY 2014 DAYONG CHEN, B.S., TIANJIN UNIVERISTY M.S., TIANJIN UNIVERSITY M.S., UNIVERSITY OF MASSACHUSETTS AMHERST Ph.D., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Professor Ryan C. Hayward Soft polymers placed under compressive stress can undergo an elastic creasing instability in which sharp folds spontaneously form on the free surfaces. This process may play an important role in contexts as diverse as brain morphogenesis, failure of tires, and electrical breakdown of soft polymer actuators. While the creasing instability has been used for collotype printing since as early as the 1850s, the scientific appreciation of this instability …
Optical And Scanning Probe Studies Of Isolated Poly (3-Hexylthiophene) Nanofibers,
2014
University of Massachusetts Amherst
Optical And Scanning Probe Studies Of Isolated Poly (3-Hexylthiophene) Nanofibers, Mina Baghgarbostanabad
Doctoral Dissertations
Plastic electronics have an essential role in the future technologies owing to their compelling characteristics such as light weight, biocompatibity, low cost fabrication, and tunable optoelectronic properties. However, the performance of polymer-based devices strongly depends on the efficiency of exciton formation and dynamics that are themselves strongly sensitive to polymer molecular packing and structural order. Therefore, the current challenge in achieving high efficiency is establishing a correlation between molecular packing and exciton coupling. P3HT nanofibers represent an attractive platform for studying optical and electronic properties of exciton coupling because their nominal (highly crystalline) internal chain packing structure is known. A …
Beam Energy Dependence Of Moments Of The Net-Charge Multiplicity Distributions In Au+Au Collisions At Rhic,
2014
University of Kentucky
Beam Energy Dependence Of Moments Of The Net-Charge Multiplicity Distributions In Au+Au Collisions At Rhic, J. Kevin Adkins, Renee Fatemi, Wolfgang Korsch, Suvarna Ramachandran, G. Webb, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, C. D. Anson, A. Aparin, D. Arkhipkin, E. C. Aschenauer
Physics and Astronomy Faculty Publications
We report the first measurements of the moments—mean (M), variance (σ2), skewness (S), and kurtosis (κ)—of the net-charge multiplicity distributions at midrapidity in Au+Au collisions at seven energies, ranging from √SNN=7.7 to 200 GeV, as a part of the Beam Energy Scan program at RHIC. The moments are related to the thermodynamic susceptibilities of net charge, and are sensitive to the location of the QCD critical point. We compare the products of the moments, σ2/M, Sσ, and κσ2, with the expectations …
Sliding Rocks On Racetrack Playa, Death Valley National Park: First Observation Of Rocks In Motion,
2014
Scripps Institution of Oceanography
Sliding Rocks On Racetrack Playa, Death Valley National Park: First Observation Of Rocks In Motion, Richard D. Norris, James M. Norris, Ralph D. Lorenz, Jib Ray, Brian Jackson
Physics Faculty Publications and Presentations
The engraved trails of rocks on the nearly flat, dry mud surface of Racetrack Playa, Death Valley National Park, have excited speculation about the movement mechanism since the 1940s. Rock movement has been variously attributed to high winds, liquid water, ice, or ice flotation, but has not been previously observed in action. We recorded the first direct scientific observation of rock movements using GPS-instrumented rocks and photography, in conjunction with a weather station and time-lapse cameras. The largest observed rock movement involved >60 rocks on December 20, 2013 and some instrumented rocks moved up to 224 m between December 2013 …
Small Satellite Space Environments Effects Test Facility,
2014
Utah State Univesity
Small Satellite Space Environments Effects Test Facility, Jr Dennison, Kent Hartley, Lisa Montierth Phillipps, Justin Dekany, James S. Dyer, Robert Johnson
Presentations
No abstract provided.
Heterogeneous Rotational Diffusion Of A Fluorescent Probe In Lipid Monolayers,
2014
Wesleyan University
Heterogeneous Rotational Diffusion Of A Fluorescent Probe In Lipid Monolayers, Christina M. Othon
Christina M Othon
The rotational correlation time of the lipid probe 1-palmitoyl-2-{6-[(7-nitro-2-1,3-benzoxadiazol-4-yl)amino]hexanoyl}-sn-glycero-3-phosphocholine (NBD-PC) is measured using fluorescence anisotropy for two lipid species. We measure the rotational diffusion in a monolayer of 1,2-Didecanoyl-sn-glycero-3-phosphocholine (DPPC) which displays a phase transition at room temperature from the liquid expanded to the liquid-condensed phase. The constant rotational diffusion of the probe throughout the phase transition reflects the measurement of dynamics in only the liquid-expanded phase. We contrast the dynamic changes during this phase coexistence to the continuous density increase observed in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) at room temperature. We observe a non-exponential decay of the probe diffusion consistent with heterogeneity …
Intensities, Broadening And Narrowing Parameters In The Ν3 Band Of Methane,
2014
KAUST
Intensities, Broadening And Narrowing Parameters In The Ν3 Band Of Methane, Et-Touhami Es-Sebbar, Aamir Farooq
Dr. Et-touhami Es-sebbar
The P-branch of methane׳s ν3 band is probed to carry out an extensive study of the 2905–2908 cm−1 infrared spectral region. Absolute line intensities as well as N2-, O2-, H2-, He-, Ar- and CO2-broadening coefficients are determined for nine transitions at room temperature. Narrowing parameters due to the Dicke effect have also been investigated. A narrow emission line-width (~0.0001 cm−1) difference-frequency-generation (DFG) laser system is used as the tunable light source. To retrieve the CH4 spectroscopic parameters, Voigt and Galatry profiles were used to simulate the measured line shape of the individual transitions.
Effects Of Brownian Motion On The Millikan Oil Drop Experiment,
2014
Minnesota State University, Mankato
Effects Of Brownian Motion On The Millikan Oil Drop Experiment, Eric Ehler, Aaron Hanson
Journal of Undergraduate Research at Minnesota State University, Mankato
Brownian motion has a significant effect on small particles suspended in a fluid. Since the Millikan oil drop experiment involves measuring the rise and fall velocities of very small oil drops suspended in air, it stands to reason that the motion of these drops will be affected by collisions with particles of air. The result of this is that the measured rise and fall velocities of each drop will not be the same as if these drops were suspended in vacuum. The size of the effect of Brownian motion is related to the mass and the radius of the oil …
Thermal Diffusivities Of Functionalized Pentacene Semiconductors,
2014
University of Kentucky
Thermal Diffusivities Of Functionalized Pentacene Semiconductors, Hao Zhang, Yulong Yao, Marcia M. Payne, John E. Anthony, Joseph W. Brill
Physics and Astronomy Faculty Publications
We have measured the interlayer and in-plane (needle axis) thermal diffusivity of 6,13-bis(triisopropylsilylethynyl) pentacene. The needle axis value is comparable to the phonon thermal diffusivities of quasi-one dimensional organic metals with excellent π-orbital overlap, and its value suggests that a significant fraction of heat is carried by optical phonons. Furthermore, the interlayer (c-axis) thermal diffusivity is at least an order of magnitude larger, and this unusual anisotropy implies very strong dispersion of optical modes in the interlayer direction, presumably due to interactions between the silyl-containing side groups. Similar values for both in-plane and interlayer diffusivities have been observed for several …
Implementation Of An F-Statistic All-Sky Search For Continuous Gravitational Waves In Virgo Vsr1 Data,
2014
LIGO - California Institute of Technology
Implementation Of An F-Statistic All-Sky Search For Continuous Gravitational Waves In Virgo Vsr1 Data, J. Aasi, B. P. Abbott, R. Abbott, T. Abbott, M. R. Abernathy, T. Accadia, F. Acernese, Marc Favata, Shaon Ghosh, Rodica Martin
Department of Physics and Astronomy Faculty Scholarship and Creative Works
We present an implementation of the F-statistic to carry out the first search in data from the Virgo laser interferometric gravitational wave detector for periodic gravitational waves from a priori unknown, isolated rotating neutron stars. We searched a frequency f0 range from 100 Hz to 1 kHz and the frequency dependent spindown f1 range from -1.6(f0/100 Hz) ×10-9 Hz s?1 to zero. A large part of this frequencyspindown space was unexplored by any of the all-sky searches published so far. Our method consisted of a coherent search over two-day periods using the F-statistic, followed by a search for coincidences among …
The Meaning Of Wise Colours – I. The Galaxy And Its Satellites,
2014
University of Kentucky
The Meaning Of Wise Colours – I. The Galaxy And Its Satellites, Robert Nikutta, Nicholas Hunt-Walker, Maia M. Nenkova, Željko Ivezić, Moshe Elitzur
Physics and Astronomy Faculty Publications
Through matches with the Sloan Digital Sky Survey (SDSS) catalogue we identify the location of various families of astronomical objects in WISE colour space. We identify reliable indicators that separate Galactic/local from extragalactic sources and concentrate here on the objects in our Galaxy and its closest satellites. We develop colour and magnitude criteria that are based only on WISE data to select asymptotic giant branch (AGB) stars with circumstellar dust shells, and separate them into O-rich and C-rich classes. With these criteria we produce an all-sky map for the count ratio of the two populations. The map reveals differences between …
