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Selected Works

1999

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Articles 1 - 18 of 18

Full-Text Articles in Physics

Dynamics Of A Gravitational Billiard With A Hyperbolic Lower Boundary, Matthew L. Ferguson, B. N. Miller, M. A. Thompson Nov 1999

Dynamics Of A Gravitational Billiard With A Hyperbolic Lower Boundary, Matthew L. Ferguson, B. N. Miller, M. A. Thompson

Matthew L. Ferguson

Gravitational billiards provide a simple method for the illustration of the dynamics of Hamiltonian systems. Here we examine a new billiard system with two parameters, which exhibits, in two limiting cases, the behaviors of two previously studied one-parameter systems, namely the wedge and parabolic billiard. The billiard consists of a point mass moving in two dimensions under the influence of a constant gravitational field with a hyperbolic lower boundary. An iterative mapping between successive collisions with the lower boundary is derived analytically. The behavior of the system during transformation from the wedge to the parabola is investigated for a few ...


Phase Imaging: Deep Or Superficial?, Nancy Burnham, O Behrend, L Odoni, J Loubet Oct 1999

Phase Imaging: Deep Or Superficial?, Nancy Burnham, O Behrend, L Odoni, J Loubet

Nancy A. Burnham

Phase images acquired while intermittently contacting a sample surface with the tip of an atomic force microscope cantilever are not easy to relate to material properties. We have simulated dynamic force curves and compared simulated with experimental results. For some cantilever–sample combinations, the interaction remains a surface effect, whereas for others, the tip penetrates the sample significantly. Height artifacts in the “topography” images, and the role of the sample stiffness, work of adhesion, damping, and topography in the cantilever response manifest themselves to different extents depending on the indentation depth.


Transparent Stacked Organic Light Emitting Devices. I. Design Principles And Transparent Compound Electrodes, G. Gu, G. Parthasarathy, P. E. Burrows, Peifang Tian, I. G. Hill, A. Kahn, S. R. Forrest Oct 1999

Transparent Stacked Organic Light Emitting Devices. I. Design Principles And Transparent Compound Electrodes, G. Gu, G. Parthasarathy, P. E. Burrows, Peifang Tian, I. G. Hill, A. Kahn, S. R. Forrest

Peifang Tian

Vertical stacking of organic light emitting devices (OLEDs) that emit the three primary colors is a means for achieving full-color flat panel displays. The physics, performance, and applications of stacked OLEDs (SOLEDs) are discussed in this and the following paper (Papers I and II, respectively). In Paper I, we analyze optical microcavity effects that can distort the emission colors of SOLEDs if not properly controlled, and describe design principles to minimize these parasitic effects. We also describe the fabrication and operating characteristics of transparent contacts that are an integral part of SOLEDs. We demonstrate that both metal-containing and metal-free transparent ...


Transparent Stacked Organic Light Emitting Devices. Ii. Device Performance And Applications To Displays, G. Gu, G. Parthasarathy, Peifang Tian Oct 1999

Transparent Stacked Organic Light Emitting Devices. Ii. Device Performance And Applications To Displays, G. Gu, G. Parthasarathy, Peifang Tian

Peifang Tian

Vertical stacking of organic light emitting devices (OLEDs) that emit the three primary colors is shown to be a means for achieving efficient and bright full-color displays. In Paper I, we addressed stacked OLED (SOLED) design and fabrication principles to optimize emission colors, operating voltage, and efficiency. Here, we present results on two different (metal-containing and metal-free cathode) SOLED structures that exhibit performance suitable for many full-color display applications. The operating voltages at 10 mA/cm2 (corresponding to video display brightnesses) are 6.8, 8.5, and 12.1 V for the red (R), green (G), and blue (B) elements ...


Glueball Production In Peripheral Heavy-Ion Collisions, Alec Schramm Aug 1999

Glueball Production In Peripheral Heavy-Ion Collisions, Alec Schramm

Alec J Schramm

The method of equivalent quanta is applied both to photon-photon and, by analogy, to double pomeron exchange in heavy-ion collisions. This Weizsäcker-Williams approach is used to calculate production cross sections for the glueball candidate fJ(1710) meson via photon-photon and pomeron-pomeron fusion in peripheral heavy-ion collisions at both RHIC and LHC energies. The impact parameter dependence for total and elastic cross sections is presented, and compared with results for proton-proton collisions.


Precise, Scalable Shadow Mask Patterning Of Vacuum-Deposited Organic Light Emitting Devices, Peifang Tian, V. Bulovic, P. Burrows, G. Gu, S. Forrest, T. Zhou Aug 1999

Precise, Scalable Shadow Mask Patterning Of Vacuum-Deposited Organic Light Emitting Devices, Peifang Tian, V. Bulovic, P. Burrows, G. Gu, S. Forrest, T. Zhou

Peifang Tian

We demonstrate a scheme to pattern vacuum-deposited, small molecular weight organic light emitting diodes 􏰉OLEDs􏰀. Both the organic thin films and the metallic electrodes are patterned by shifting the position of a single shadow mask which accompanies the substrate throughout the deposition process. A full color, stacked OLED 􏰉SOLED􏰀 has been fabricated using this technique. The substrate movement relative to the mask was manually controlled to a root mean square accuracy of 􏰑8 􏰇m using a mask translating fixture. The performance of the patterned SOLED is comparable with that of devices fabricated by conventional, low tolerance methods. The limits to ...


Unexpected Symmetries In Classical Moduli Spaces, Tonnis Ter Veldhuis Jun 1999

Unexpected Symmetries In Classical Moduli Spaces, Tonnis Ter Veldhuis

Tonnis ter Veldhuis

No abstract provided.


The Spectral Function Of Composites: The Inverse Problem, Anthony Day, M. Thorpe Mar 1999

The Spectral Function Of Composites: The Inverse Problem, Anthony Day, M. Thorpe

Anthony Roy Day

No abstract provided.


Mil-Std-188-125-2, High-Altitude Emp Protection For Transportable Systems Mar 1999

Mil-Std-188-125-2, High-Altitude Emp Protection For Transportable Systems

George H Baker

This standard establishes minimum requirements and design objectives for high-altitude electromagnetic pulse (HEMP) hardening of transportable1 ground-based systems that perform critical, time-urgent command, control, communications, computer, and intelligence (C4I) missions. Systems required to fully comply with the provisions of the standard will be designated by the Joint Chiefs of Staff, a Military Department Headquarters, or a Major Command.

The standard prescribes minimum performance requirements for low-risk protection from mission-aborting damage or upset due to HEMP threat environments. The standard also addresses minimum testing requirements for demonstrating that prescribed performance has been achieved and for verifying that the installed protection measures ...


Elastic And Shear Moduli Of Single-Walled Carbon Nanotube Ropes, Nancy Burnham, Jean-Paul Salvetat, G Andrew D Briggs, Jean-Marc Bonard, Revathi Bacsa, Andrzej Kulik, Thomas Stöckli, László Forró Jan 1999

Elastic And Shear Moduli Of Single-Walled Carbon Nanotube Ropes, Nancy Burnham, Jean-Paul Salvetat, G Andrew D Briggs, Jean-Marc Bonard, Revathi Bacsa, Andrzej Kulik, Thomas Stöckli, László Forró

Nancy A. Burnham

Carbon nanotubes are believed to be the ultimate low-density high-modulus fibers, which makes their characterization at nanometer scale vital for applications. By using an atomic force microscope and a special substrate, the elastic and shear moduli of individual single-walled nanotube (SWNT) ropes were measured to be of the order of 1 TPa and 1 GPa, respectively. In contrast to multiwalled nanotubes, an unexpectedly low intertube shear stiffness dominated the flexural behavior of the SWNT ropes. This suggests that intertube cohesion should be improved for applications of SWNT ropes in high-performance composite materials.


Synthesis Of Bulk Polycrystalline Indium Nitride At Subatmospheric Pressures., Jeffrey Dyck, K. Kash, C. Hayman, A. Argoitia, M. Grossner, J. Angus, W.-L. Zhou Dec 1998

Synthesis Of Bulk Polycrystalline Indium Nitride At Subatmospheric Pressures., Jeffrey Dyck, K. Kash, C. Hayman, A. Argoitia, M. Grossner, J. Angus, W.-L. Zhou

Jeffrey Dyck

Polycrystalline, wurtzitic indium nitride was synthesized by saturating indium with nitrogen from microwave plasma sources. The structure was confirmed by x-ray diffraction, electron diffraction, and elemental analysis. Two types of growth were observed: (i) dendritic crystals on the original melt surface, and (ii) hexagonal platelets adjacent to the In metal source on the upper edge of the crucible. The method does not involve a foreign substrate to initiate growth and is a potential alternative to the high-pressure techniques normally associated with bulk growth of indium nitride. The lattice parameters were a = 3.5366 ± 0.0005 angstrom and c = 5 ...


Effects Of Surface Topography On Oxide Deposition Rates Using Teos/O2 Chemistry, James Doyle, G. Feng Dec 1998

Effects Of Surface Topography On Oxide Deposition Rates Using Teos/O2 Chemistry, James Doyle, G. Feng

James R. Doyle

No abstract provided.


Growth Of Oriented Thick Films Of Gallium Nitride From The Melt., Jeffrey Dyck, K. Kash, M. Grossner, C. Hayman, A. Argoitia, N. Yang, M.-H. Hong, M. Kordesch, J. Angus Dec 1998

Growth Of Oriented Thick Films Of Gallium Nitride From The Melt., Jeffrey Dyck, K. Kash, M. Grossner, C. Hayman, A. Argoitia, N. Yang, M.-H. Hong, M. Kordesch, J. Angus

Jeffrey Dyck

While significant strides have been made in the optimization of GaN-based devices on foreign substrates, a more attractive alternative would be homoepitaxy on GaN substrates. The primary motivation of this work is to explore the growth of thick films of GaN from the melt for the ultimate use as substrate material. We have previously demonstrated the synthesis of polycrystalline, wurtzitic gallium nitride and indium nitride by saturating gallium metal and indium metal with atomic nitrogen from a microwave plasma source. Plasma synthesis avoids the high equilibrium pressures required when molecular nitrogen is used as the nitrogen source. Here we report ...


Changes In The Fermi Surface At The Magnetization Reorientation Transition In Fe/Cu(100), Reginaldt H. Madjoe, Alexey N. Koveshnikov, Christopher Harwell, Randall W. Hall, Roger L. Stockbauer, Richard L. Lutz Dec 1998

Changes In The Fermi Surface At The Magnetization Reorientation Transition In Fe/Cu(100), Reginaldt H. Madjoe, Alexey N. Koveshnikov, Christopher Harwell, Randall W. Hall, Roger L. Stockbauer, Richard L. Lutz

Randall W. Hall

We present a study of the evolution of the valence bandstructure of Fe/Cu(100) as a function of Fe coverage in the 0–12 monolayer range. Angle-resolved photoelectron spectroscopy was used to probe the valence electronic structure and to extract Fermi surface contours as a function of increasing Fe coverage. The first few monolayers show Fe-induced densities of states that are significantly different from those in thicker films. At 5 ML, distinct changes occur in the Fermi surface, where a magnetization reorientation transition has been observed previously.


Dynamics Of Simulated Water Under Pressure, Francis W. Starr, F. Sciortino, H. E. Stanley Dec 1998

Dynamics Of Simulated Water Under Pressure, Francis W. Starr, F. Sciortino, H. E. Stanley

Francis Starr

No abstract provided.


The He-Lih Potential Energy Surface Revisited. I. An Interpolated Rigid Rotor Surface, Robert Hinde Dec 1998

The He-Lih Potential Energy Surface Revisited. I. An Interpolated Rigid Rotor Surface, Robert Hinde

Robert Hinde

We reconsider the potential energy surface of the He–LiH system recently examined by Gianturco and co-workers [F. A. Gianturco et al., Chem. Phys. 215, 227 (1997)]. We compute the He–LiH interaction energy at the CCSD(T) level using large correlation consistent atomic basis sets supplemented with bond functions. To capture the severe anisotropy of the He–LiH potential, we interpolate our ab initio points in the angular direction with cubic splines, then expand the splines in terms of Legendre polynomials. The resulting smooth potential surface differs substantially from that of Gianturco et al.; in particular, our attractive He ...


Semi-Insulating Semiconductor Heterostructures: Optoelectronic Properties And Applications, David D. Nolte Dec 1998

Semi-Insulating Semiconductor Heterostructures: Optoelectronic Properties And Applications, David D. Nolte

David D Nolte

This review covers a spectrum of optoelectronic properties of and uses for semi-insulating semiconductor heterostructures and thin films, including epilayers and quantum wells. Compensation by doping, implantation, and nonstoichiometric growth are described in terms of the properties of point defects and Fermi level stabilization and pinning. The principal optical and optoelectronic properties of semi-insulating epilayers and heterostructures, such as excitonic electroabsorption of quantum-confined excitons, are described, in addition to optical absorption by metallic or semimetallic precipitates in these layers. Low-temperature grown quantum wells that have an arsenic-rich nonstoichiometry and a supersaturated concentration of grown-in vacancies are discussed. These heterostructures experience ...


Solid–Liquid Phase Equilibrium For Binary Lennard-Jones Mixtures, Monica H. Lamm, Carol K. Hall Dec 1998

Solid–Liquid Phase Equilibrium For Binary Lennard-Jones Mixtures, Monica H. Lamm, Carol K. Hall

Monica H. Lamm

Solid–liquid phase diagrams are calculated for binary mixtures of Lennard-Jones spheres using Monte Carlo simulation and the Gibbs–Duhem integration technique of Kofke. We calculate solid–liquid phase diagrams for the model Lennard-Jones mixtures: argon–methane, krypton–methane, and argon–krypton, and compare our simulation results with experimental data and with Cottin and Monson’s recent cell theory predictions. The Lennard-Jones model simulation results and the cell theory predictions show qualitative agreement with the experimental phase diagrams. One of the mixtures, argon–krypton, has a different phase diagram than its hard-sphere counterpart, suggesting that attractive interactions are an important ...