TY - JOUR TI - Resource Letter: FMMLS-1: Friction at macroscopic and microscopic length scales AU - Krim, J. T2 - American Journal of Physics AB - This Resource Letter provides a guide to the literature on the fundamental origins of friction. Books, reviews, and journal articles are cited for the following topics: History of friction and tribology, the adhesion theory of macroscopic friction, first principles’ treatments of frictional energy dissipation at the atomic level, experimental methods for studying friction at the atomic-scale, stick-slip phenomena and lattice commensurability effects. DA - 2002/// PY - 2002/// DO - 10.1119/1.1484153 VL - 70 IS - 9 SP - 890-897 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85024818749&partnerID=MN8TOARS ER - TY - JOUR TI - Double polarized neutron-proton scattering and nucleon-nucleon tensor force: An alternative analysis AU - Tornow, W. AU - Gould, C. R. AU - Haase, D. G. AU - Walston, J. R. AU - Raichle, B. W. T2 - Physical Review C AB - Previous neutron-proton total cross-section difference measurements $\ensuremath{\Delta}{\ensuremath{\sigma}}_{L}$ and $\ensuremath{\Delta}{\ensuremath{\sigma}}_{T}$ between ${E}_{n}=7.43$ and 17.1 MeV have been analyzed in a new way that reduces experimental systematic uncertainties. The results obtained for the ${}^{3}{S}_{1}{\ensuremath{-}}^{3}{D}_{1}$ mixing parameter ${\ensuremath{\epsilon}}_{1}$ are very similar to the published values, substantiating the previous conclusion that the nucleon-nucleon tensor force at low energies is stronger than predicted by the Nijmegen partial-wave analysis and, therefore, by all the recent high-precision nucleon-nucleon potential models as well. DA - 2002/3/21/ PY - 2002/3/21/ DO - 10.1103/physrevc.65.047002 VL - 65 IS - 4 SP - 047002 SN - 0556-2813 1089-490X UR - http://dx.doi.org/10.1103/physrevc.65.047002 ER - TY - CONF TI - N-D Scattering Measurements with the TUNL Dynamically Polarized Deuteron Target AU - Markoff, D. M. AU - Foster, R. D. AU - Gould, C. R. AU - Haase, D. G. AU - Poole, J. O. AU - Raichle, B. W. AU - Tornow, W. T2 - Proceedings of the Ninth International Workshop A2 - Derenchuk, V. A2 - von Przewoski, B. C2 - 2002/5// C3 - Polarized Sources and Targets DA - 2002/5// DO - 10.1142/9789812777683_0054 PB - WORLD SCIENTIFIC UR - http://dx.doi.org/10.1142/9789812777683_0054 ER - TY - BOOK TI - Astrophysics, Symmetries, and Applied Physics at Spallation Neutron Sources A3 - Koehler, P.E. A3 - Gould, C.R. A3 - Haight, R.C. A3 - Valentine, T.E. AB - The Detector for Advanced Neutron Capture Experiments at LANSCE (J L Ullmann et al.) Recent Astrophysics Results from ORELA and Possible Future Experiments at ORELA and SNS (P E Koehler) Applied Nuclear Physics at Spallation Neutron Sources (P Oblozinzky) Aluminum Data Measurements and Evaluation for Criticality Safety Applications (L C Leal et al.) Measurement of Neutron Capture Cross Sections of Long-lived Fission Products (H Harada et al.) Radioactive Target Production at RIA (J C Blackmon) Parity Violation in Epithermal Neutron Resonances (G E Mitchell et al.) Violation of Fundamental Symmetries in Resonance Neutron Induced Fission (A Barabanov et al.) Time Reversal Tests with Epithermal Neutrons (C R Gould) Neutronic Characteristics of the Spallation Neutron Source (P D Ferguson et al.) and other papers. DA - 2002/11/21/ PY - 2002/11/21/ DO - 10.1142/5176 PB - WORLD SCIENTIFIC SN - 9789812382498 9789812776242 UR - http://dx.doi.org/10.1142/5176 ER - TY - ER - TY - ER - TY - JOUR TI - Solid Oxygen as a Source of Ultracold Neutrons AU - Liu, C.-Y. AU - Ito, T. AU - Martin, J. AU - Tipton, B. AU - Hogan, G. AU - Morris, C. AU - Saunders, A. AU - Young, A.R. T2 - Bulletin of the American Physical Society DA - 2002/// PY - 2002/// VL - 47 SP - 129 ER - TY - JOUR TI - Depolarization of Ultracold Neutrons in Diamond Coated Guides AU - Makela, M. AU - Pitt, M. AU - Vogelaar, R.B. AU - Yuan, J. AU - Pichlmaier, A. AU - Teasdale, B. AU - Geltenbort, P. AU - Young, A.R. AU - Lasakov, M. AU - Krasnoshekova, I. AU - Serebrov, A. AU - Vasiliev, A. AU - Liu, C.-Y. AU - Pesavento, U. T2 - Bulletin of the American Physical Society DA - 2002/// PY - 2002/// VL - 47 SP - 98 ER - TY - JOUR TI - Measurement of Neutron Beta-Decay Angular Correlations using Ultracold Neutrons AU - Young, A.R. T2 - Bulletin of the American Physical Society DA - 2002/// PY - 2002/// VL - 46 ER - TY - JOUR TI - Novel Proton Detectors for Measuring Angular Correlations of Ultra-Cold Neutron Decay AU - Hoedl, Seth AU - Young, Albert AU - Adles, Eric AU - Jain, Rakesh AU - Makela, Mark AU - Ito, Takeyasu T2 - Bulletin of the American Physical Society DA - 2002/// PY - 2002/// VL - 47 SP - 84 ER - TY - JOUR TI - An Apparatus to Store, Polarize and Spin-Flip Ultracold Neutrons AU - Liu, C.-Y. AU - Pesavento, U. AU - Yuan, J. AU - Geltenbort, P. AU - Pichlmaier, A. AU - Saunders, A. AU - Teasdale, W. AU - Young, A.R. AU - Lasakov, M. AU - Krasnoshekova, I. AU - Serebrov, A. AU - Vasiliev, A. AU - Makela, M. AU - Pitt, M. AU - Vogelaar, R.B. T2 - Bulletin of the American Physical Society DA - 2002/// PY - 2002/// VL - 47 SP - 98 ER - TY - SOUND TI - Angular Correlations Measurements With Polarized Ultra-Cold Neutrons AU - Young, A.R. DA - 2002/9// PY - 2002/9// ER - TY - JOUR TI - DNA binding properties of the yeast Msh2-Msh6 and Mlh1-Pms1 heterodimers AU - Drotschmann, Karin AU - Hall, Mark C AU - Shcherbakova, Polina V AU - Wang, Hong AU - Erie, Dorothy A AU - Brownewell, Floyd R AU - Kool, Eric T AU - Kunkel, Thomas A T2 - Biological chemistry DA - 2002/// PY - 2002/// VL - 383 IS - 6 SP - 969-975 ER - TY - JOUR TI - A minimal exonuclease domain of WRN forms a hexamer on DNA and possesses both 3'-5'exonuclease and 5'-protruding strand endonuclease activities AU - Xue, Yu AU - Ratcliff, Glenn C AU - Wang, Hong AU - Davis-Searles, Paula R AU - Gray, Matthew D AU - Erie, Dorothy A AU - Redinbo, Matthew R T2 - Biochemistry DA - 2002/// PY - 2002/// VL - 41 IS - 9 SP - 2901-2912 ER - TY - JOUR TI - Relaxation processes in relativistic plasma created from vacuum by a strong field AU - Skokov, V.V. AU - Toneev, V.D. AU - Vinnik, D.V. AU - Smolyansky, S.A. DA - 2002/12// PY - 2002/12// VL - 12 UR - http://inspirehep.net/record/606929 ER - TY - CONF TI - Quark gluon evolution in early stage of ultrarelativistic heavy ion collisions AU - Skokov, V.V. AU - Smolyansky, S.A. AU - Toneev, V.D. C2 - 2002/10// C3 - 16th International Baldin Seminar on High Energy Physics Problems DA - 2002/10// UR - http://inspirehep.net/record/598973 ER - TY - CONF TI - An activity-based curriculum for large introductory physics courses: The SCALE-UP project AU - Saul, J. AU - Beichner, R. T2 - Physics Education Research Conference A2 - Franklin, S.V. A2 - Cummings, K. A2 - Marx, J. C2 - 2002/// C3 - Proceedings of the 2001 Physics Education Research Conference CY - Rochester, NY DA - 2002/// PY - 2001/7/25/ PB - American Institute of Physics ER - TY - CONF TI - Reform in higher education AU - Beichner, R. T2 - Conference on Undergraduate Science and Mathematics Education C2 - 2002/// C3 - Proceedings of the Conference on Undergraduate Science and Mathematics Education CY - University of Tennessee, Knoxville, TN DA - 2002/// PY - 2002/// ER - TY - BOOK TI - Keeping in sync AU - Ditto, William L. AU - Pikovsky, Arkady AU - Rosenblum, Michael AU - Kurths, Jurgen DA - 2002/2/14/ PY - 2002/2/14/ DO - 10.1038/415736b VL - 415 SE - 736–737 ER - TY - CHAP TI - Spatio-temporal nonlinear dynamics: a new beginning AU - Ditto, William T2 - Nonlinear Dynamics and Chaos: Where do we go from here? A2 - Hogan, J. A2 - Krauskopf, A.R. A2 - di Bernado, Mario A2 - Wilson, R. Eddie A2 - Osinga, Hinke M. A2 - Homer, Martin E. A2 - Champneys, Alan R. PY - 2002/8// DO - 10.1201/9781420033830.ch13 PB - CRC Press SN - 9780750308625 9781420033830 ER - TY - CONF TI - CMB (and other) challenges to BBN AU - Steigman, G. AU - Kneller, J.P. AU - Zentner, A. C2 - 2002/// C3 - Revista Mexicana de Astronomia y Astrofisica: Serie de Conferencias DA - 2002/// VL - 12 SP - 265-271 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0347377313&partnerID=MN8TOARS ER - TY - JOUR TI - Reply to “Comment on ‘Monostable array-enhanced stochastic resonance’ ” AU - Lindner, John F. AU - Breen, Barbara J. AU - Bulsara, Adi R. AU - Ditto, William L. T2 - Physical Review E AB - We take this opportunity to clarify issues raised in the preceding Comment by Soskin and McClintock [Phys. Rev. E. 66, 013101 (2002)]. In particular, we provide further details and results to motivate and explicate the methodologies we have employed to investigate stochastic resonance in arrays of monostable elements. DA - 2002/7/16/ PY - 2002/7/16/ DO - 10.1103/physreve.66.013102 VL - 66 IS - 1 J2 - Phys. Rev. E LA - en OP - SN - 1063-651X 1095-3787 UR - http://dx.doi.org/10.1103/physreve.66.013102 DB - Crossref ER - TY - CHAP TI - ATOMIC TRANSFORMATIONS, STRENGTH, PLASTICITY, AND ELECTRON TRANSPORT IN STRAINED CARBON NANOTUBES AU - Bernholc, J. AU - Buongiorno Nardelli, M. AU - Orlikowski, D. AU - Roland, C. AU - Zhao, Q. T2 - Fiber Fracture AB - Nanotubes are hollow cylinders consisting of ‘rolled-up’ graphitic sheets. They form spontaneously in the same apparatus as the famed C60 molecule, and have been predicted and/or observed to have even more spectacular properties than C60, including extremely high strength and flexibility, ability to form nanoscale electronic devices consisting entirely of carbon, strong capillary effects, cold cathode field emission, etc. Carbon nanotubes have also been theoretically predicted to be among the strongest materials known. Their strength, which has already been verified experimentally, may enable unique applications in many critical areas of technology. While very high strain rates must lead to tube breakage, nanotubes with (n,m) indices, where n,m < 14, can display plastic flow under suitable conditions. This occurs through the conversion of four hexagons to a 5–7–7–5 defect, which then splits into two 5–7 pairs. The index of the tube changes between the 5–7 pairs, potentially leading to metal–semiconductor junctions. Furthermore, carbon adatoms-induced transformations in strained nanotubes can lead to the formation of quantum dots. The high-strain conditions can be imposed on the tube via, e.g., AFM tip manipulations, and we show that such procedures can lead to intratube device formation. The defects and the index changes occurring during the mechanical transformations also affect the electrical properties of nanotubes. The computed quantum conductances of strained defective and deformed tubes show that the defect density and the contacts play key roles in reducing the conductance at the Fermi energy. The role of bending in changing the electrical properties was also explored. It was found that mechanical deformations do not significantly affect the conductance of bent armchair nanotubes up to substantial bending angles, while a conductivity gap is induced by the bending of chiral nanotubes. These results are in good agreement with recent experimental data. PY - 2002/// DO - 10.1016/b978-008044104-7/50016-2 SP - 357-376 OP - PB - Elsevier SN - 9780080441047 UR - http://dx.doi.org/10.1016/b978-008044104-7/50016-2 DB - Crossref KW - carbon nanotube KW - molecular dynamics KW - tensile strength KW - plasticity KW - adatoms KW - defects KW - electron transport ER - TY - JOUR TI - Field Emission Properties of BN/C and BN@C Hybrid Nanotubes AU - Meunier, Vincent AU - Buongiorno Nardelli, Marco AU - Shelton, William AU - Roland, Christopher AU - Bernholc, Jerry AU - Zacharia, Thomas T2 - MRS Proceedings DA - 2002/// PY - 2002/// DO - 10.1557/proc-739-h5.7 VL - 739 J2 - MRS Proc. LA - en OP - SN - 0272-9172 1946-4274 UR - http://dx.doi.org/10.1557/proc-739-h5.7 DB - Crossref ER - TY - JOUR TI - Canonical transformations and non-unitary evolution AU - Davis, E D AU - Ghandour, G I T2 - Journal of Physics A: Mathematical and General AB - We test the idea that transformations which, at the classical level, can be interpreted as evolutions are represented within quantum mechanics by unitary operators. To this end, we consider non-trivial canonical transformations which leave invariant the form of the Hamilton function of a system. We demonstrate that infinite families of such transformations exist for a variety of familiar conservative systems of one degree of freedom. We show how the precise form of integral equations for the stationary state wavefunctions implied by the existence of these canonical transformations can be pinned down by exploiting the algebra of the transformations and a symmetry of their generating functions. We recover several integral equations found in the literature on standard special functions of mathematical physics. We find that when one of the classical canonical transformations we consider is non-linear, its quantum implementation is non-unitary. We end with some comments on the implications of our findings for semiclassical studies and a brief discussion relevant to string theory of the generalization to scalar field theories in 1 + 1 dimensions. DA - 2002/7/5/ PY - 2002/7/5/ DO - 10.1088/0305-4470/35/28/307 VL - 35 IS - 28 SP - 5875-5891 J2 - J. Phys. A: Math. Gen. OP - SN - 0305-4470 UR - http://dx.doi.org/10.1088/0305-4470/35/28/307 DB - Crossref ER - TY - JOUR TI - Parallel computing with extended dynamical systems AU - Sinha, S. AU - Munakata, T. AU - Ditto, W.L. T2 - Physical Review E - Statistical, Nonlinear, and Soft Matter Physics AB - We discuss the scope of parallelism based on extended dynamical systems, in particular, arrays of chaotic elements. As a case study we demonstrate the rapid solution of the Deutsch-Jozsa problem, utilizing the collective properties of such systems. DA - 2002/// PY - 2002/// DO - 10.1103/PhysRevE.65.036214 VL - 65 IS - 3 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-37649027841&partnerID=MN8TOARS ER - TY - JOUR TI - Nonlinear antenna technology AU - Meadows, B.K. AU - Heath, T.H. AU - Neff, J.D. AU - Brown, E.A. AU - Fogliatti, D.W. AU - Gabbay, M. AU - In, V. AU - Hasler, P. AU - Deweerth, S.P. AU - Ditto, W.L. T2 - Proceedings of the IEEE AB - Nonlinear antennas combine advances in nonlinear dynamics, active antenna design, and analog microelectronics to generate beam steering and beam forming across an array of nonlinear oscillators. Nonlinear antennas exploit two phenomena typically shunned in traditional designs: nonlinear unit cells and interelement coupling. The design stems from nonlinear coupled differential equation analysis that by virtue of the dynamic control is far less complex than the linear counterparts by eliminating the need for phase shifters and beam forming computers. These advantages arise from incorporating nonlinear dynamics rather than limiting the system to linear quasisteady state operation. A theoretical framework describing beam shaping and beam forming by exploiting the phase, amplitude, and coupling dynamics of nonlinear oscillator arrays is presented. Experimental demonstration of nonlinear beam steering is realized using analog microelectronics. DA - 2002/// PY - 2002/// DO - 10.1109/JPROC.2002.1015012 VL - 90 IS - 5 SP - 882-896 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-33646891329&partnerID=MN8TOARS KW - active antenna KW - analog VLSI KW - beam forming KW - beam steering KW - coupled oscillator array KW - nonidentical oscillators KW - nonlinear dynamics ER - TY - JOUR TI - Flexible parallel implementation of logic gates using chaotic elements AU - Sinha, S. AU - Munakata, T. AU - Ditto, W.L. T2 - Physical Review E - Statistical, Nonlinear, and Soft Matter Physics AB - We demonstrate the basic principles for the direct and flexible implementation of all basic logical operations utilizing low dimensional chaos. Then we generalize the concept to high dimensional chaotic systems, and show the parallelism inherent in such systems. As a case study we implement the proposed parallel computing architecture to obtain parallelized bit-by-bit addition with a two-dimensional chaotic neuronal and a three-dimensional chaotic laser model. DA - 2002/// PY - 2002/// DO - 10.1103/PhysRevE.65.036216 VL - 65 IS - 3 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-37649030639&partnerID=MN8TOARS ER - TY - JOUR TI - Chaos computing: Implementation of fundamental logical gates by chaotic elements AU - Munakata, T. AU - Sinha, S. AU - Ditto, W.L. T2 - IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications AB - Basic principles of implementing the most fundamental computing functions by chaotic elements are described. They provide a theoretical foundation of computer architecture based on a totally new principle other than silicon chips. The fundamental functions are: the logical AND, OR, NOT, XOR, and NAND operations (gates) and bit-by-bit arithmetic operations. Each of the logical operations is realized by employing a single chaotic element. Computer memory can be constructed by combining logical gates. With these fundamental ingredients in hand, it is conceivable to build a simple, fast, yet cost effective, general-purpose computing device. Chaos computing may also lead to dynamic architecture, where the hardware design itself evolves during the course of computation.. The basic ideas are explained by employing a one-dimensional model, specifically the logistic map. DA - 2002/// PY - 2002/// DO - 10.1109/TCSI.2002.804551 VL - 49 IS - 11 SP - 1629-1633 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0036857050&partnerID=MN8TOARS KW - chaos computing KW - new computing paradigm KW - one-dimensional (1-D) chaotic systems ER - TY - JOUR TI - Observation of a Strongly Interacting Degenerate Fermi Gas of Atoms AU - O’Hara, K.M. AU - Hemmer, S.L. AU - Gehm, M.E. AU - Granade, S.R. AU - Thomas, J.E. T2 - Science AB - We report on the observation of a highly degenerate, strongly interacting Fermi gas of atoms. Fermionic lithium-6 atoms in an optical trap are evaporatively cooled to degeneracy using a magnetic field to induce strong, resonant interactions. Upon abruptly releasing the cloud from the trap, the gas is observed to expand rapidly in the transverse direction while remaining nearly stationary in the axial direction. We interpret the expansion dynamics in terms of collisionless superfluid and collisional hydrodynamics. For the data taken at the longest evaporation times, we find that collisional hydrodynamics does not provide a satisfactory explanation, whereas superfluidity is plausible. DA - 2002/11/7/ PY - 2002/11/7/ DO - 10.1126/science.1079107 VL - 298 IS - 5601 SP - 2179-2182 SN - 0036-8075 1095-9203 UR - http://dx.doi.org/10.1126/science.1079107 ER - TY - JOUR TI - Experimental Simulation of Two-Particle Quantum Entanglement using Classical Fields AU - Lee, K. F. AU - Thomas, J. E. T2 - Physical Review Letters AB - We experimentally demonstrate simulation of two entangled quantum bits using classical fields of two frequencies and two polarizations. Multiplication of optical heterodyne beat signals from two spatially separated regions simulates coincidence detection of two particles. The product signal so obtained contains several frequency components, one of which can be selected by bandpass frequency filtering. The bandpassed signal contains two indistinguishable, interfering contributions, permitting simulation of four polarization-entangled Bell-like states. These classical field methods may be useful in small scale simulations of quantum logic operations that require multiparticle entanglement without collapse. DA - 2002/2/12/ PY - 2002/2/12/ DO - 10.1103/physrevlett.88.097902 VL - 88 IS - 9 J2 - Phys. Rev. Lett. LA - en OP - SN - 0031-9007 1079-7114 UR - http://dx.doi.org/10.1103/physrevlett.88.097902 DB - Crossref ER - TY - JOUR TI - All-Optical Production of a Degenerate Fermi Gas AU - Granade, S. R. AU - Gehm, M. E. AU - O'Hara, K. M. AU - Thomas, J. E. T2 - Physical Review Letters AB - We achieve degeneracy in a mixture of the two lowest hyperfine states of 6Li by direct evaporation in a CO2 laser trap, yielding the first all optically produced degenerate Fermi gas. More than 10(5) atoms are confined at temperatures below 4 microK at full trap depth, where the Fermi temperature for each state is 8 microK. This degenerate two-component mixture is ideal for exploring mechanisms of superconductivity ranging from Cooper pairing to Bose-Einstein condensation of strongly bound pairs. DA - 2002/3/8/ PY - 2002/3/8/ DO - 10.1103/physrevlett.88.120405 VL - 88 IS - 12 J2 - Phys. Rev. Lett. LA - en OP - SN - 0031-9007 1079-7114 UR - http://dx.doi.org/10.1103/physrevlett.88.120405 DB - Crossref ER - TY - JOUR TI - Neutrino emission from Goldstone modes in dense quark matter AU - Jaikumar, Prashanth AU - Prakash, Madappa AU - Schäfer, Thomas T2 - Phys.Rev.D AB - We calculate neutrino emissivities from the decay and scattering of Goldstone bosons in the color-flavor-locked (CFL) phase of quarks at high baryon density. Interactions in the CFL phase are described by an effective low-energy theory. For temperatures in the tens of keV range, relevant to the long-term cooling of neutron stars, the emissivities involving Goldstone bosons dominate over those involving quarks, because gaps in the CFL phase are $\ensuremath{\sim}100\mathrm{MeV}$ while the masses of Goldstone modes are on the order of 10 MeV. For the same reason, the specific heat of the CFL phase is also dominated by the Goldstone modes. Notwithstanding this, both the emissivity and the specific heat from the massive modes remain rather small, because of their extremely small number densities. The values of the emissivity and the specific heat imply that the time scale for the cooling of the CFL core is $\ensuremath{\sim}{10}^{26}\mathrm{y}\mathrm{r},$ which makes the CFL phase invisible as the exterior layers of normal matter surrounding the core will continue to cool through significantly more rapid processes. If the CFL phase appears during the evolution of a protoneutron star, neutrino interactions with Goldstone bosons are expected to be significantly more important since temperatures are high enough $(\ensuremath{\sim}20--40\mathrm{MeV})$ to admit large number densities of Goldstone modes. DA - 2002/3// PY - 2002/3// DO - 10.1103/PhysRevD.66.063003 VL - 66 SP - 063003 UR - http://inspirehep.net/record/583748 ER - TY - CONF TI - Nuclear-matter distributions of halo nuclei from elastic proton scattering in inverse kinematics AU - Egelhof, P. AU - Alkhazov, G.D. AU - Andronenko, M.N. AU - Bauchet, A. AU - Dobrovolsky, A.V. AU - Fritz, S. AU - Gavrilov, G.E. AU - Geissel, H. AU - Gross, C. AU - Khanzadeev, A.V. AU - Korolev, G.a. AU - Kraus, G. AU - Lobodenko, A.A. AU - Munzenberg, G. AU - Mutterer, M. AU - Neumaier, S.R. AU - Schäfer, T. AU - Scheidenberger, C. AU - Seliverstov, D.M. AU - Timofeev, N.A. AU - Vorobyov, A.A. AU - Yatsoura, V.I. C2 - 2002/1// C3 - Eur.Phys.J.A DA - 2002/1// DO - 10.1007/978-3-642-55560-2_20 SP - 61-67 UR - http://inspirehep.net/record/609988 ER - TY - JOUR TI - High density quark matter under stress AU - Bedaque, Paulo F. AU - Schäfer, Thomas T2 - Nucl.Phys.A AB - We study the effect of SU(3)-flavor breaking on high-density quark matter. We discuss, in particular, a nonzero electron chemical potential and a finite strange-quark mass. We argue that these perturbations trigger pion or kaon condensation. The critical chemical potential behaves as μe∼mmsΔ/pF and the critical strange-quark mass as ms∼m1/3Δ2/3, where m is the light-quark mass, Δ is the gap, and pF is the Fermi momentum. We note that parametrically, both the critical μe and ms2/(2pF) are much smaller than the gap. DA - 2002/5// PY - 2002/5// DO - 10.1016/S0375-9474(01)01272-6 VL - 697 SP - 802-822 UR - http://inspirehep.net/record/556611 ER - TY - CONF TI - The ground state of strange quark matter AU - Schäfer, T. A2 - Karsch, F. A2 - Satz, H. C2 - 2002/// C3 - Nucl.Phys.A DA - 2002/// DO - 10.1016/S0375-9474(02)00701-7 VL - 702 SP - 167-176 UR - http://inspirehep.net/record/592770 ER - TY - JOUR TI - Instanton effects in QCD at high baryon density AU - Schäfer, Thomas T2 - Phys.Rev.D AB - We study instanton effects in QCD at very high baryon density. In this regime instantons are suppressed by a large power of $({\ensuremath{\Lambda}}_{\mathrm{QCD}}/\ensuremath{\mu}),$ where ${\ensuremath{\Lambda}}_{\mathrm{QCD}}$ is the QCD scale parameter and \ensuremath{\mu} is the baryon chemical potential. Instantons are nevertheless important because they contribute to several physical observables that vanish to all orders in perturbative QCD. We study, in particular, the chiral condensate and its contribution ${m}_{\mathrm{GB}}^{2}\ensuremath{\sim}m〈\overline{\ensuremath{\psi}}\ensuremath{\psi}〉$ to the masses of Goldstone bosons in the CFL phase of QCD with ${N}_{f}=3$ flavors. We find that at densities $\ensuremath{\rho}\ensuremath{\sim}(5\ensuremath{-}10){\ensuremath{\rho}}_{0},$ where ${\ensuremath{\rho}}_{0}$ is the density of nuclear matter, the result is dominated by large instantons and subject to considerable uncertainties. We suggest that these uncertainties can be addressed using lattice calculations of the instanton density and the pseudoscalar diquark mass in QCD with two colors. We study the topological susceptibility and Witten-Veneziano type mass relations in both ${N}_{c}=2$ and ${N}_{c}=3$ QCD. DA - 2002/1// PY - 2002/1// DO - 10.1103/PhysRevD.65.094033 VL - 65 SP - 094033 UR - http://inspirehep.net/record/581952 ER - TY - CONF TI - Strange goings on in quark matter AU - Schäfer, Thomas AB - We review recent work on how the superfluid state of three flavor quark matter is affected by non-zero quark masses and chemical potentials. C2 - 2002/9// C3 - 6th Workshop on Non-Perturbative Quantum Chromodynamics DA - 2002/9// DO - 10.1142/9789812778352_0034 SP - 250-256 UR - http://inspirehep.net/record/562647 ER - TY - JOUR TI - Mass terms in effective theories of high density quark matter AU - Schäfer, Thomas T2 - Phys.Rev.D AB - We study the structure of mass terms in the effective theory for quasi-particles in QCD at high baryon density. To next-to-leading order in the $1/p_F$ expansion we find two types of mass terms, chirality conserving two-fermion operators and chirality violating four-fermion operators. In the effective chiral theory for Goldstone modes in the color-flavor-locked (CFL) phase the former terms correspond to effective chemical potentials, while the latter lead to Lorentz invariant mass terms. We compute the masses of Goldstone bosons in the CFL phase, confirming earlier results by Son and Stephanov as well as Bedaque and Sch\"afer. We show that to leading order in the coupling constant $g$ there is no anti-particle gap contribution to the mass of Goldstone modes, and that our results are independent of the choice of gauge. DA - 2002/9// PY - 2002/9// DO - 10.1103/PhysRevD.65.074006 VL - 65 SP - 074006 UR - http://inspirehep.net/record/562459 ER - TY - JOUR TI - Squeezed quark matter AU - Schäfer, T. T2 - APCTP Bull. DA - 2002/// PY - 2002/// VL - 5 SP - 10-12 UR - http://inspirehep.net/record/609568 ER - TY - JOUR TI - Instantons in QCD with many colors AU - Schäfer, Thomas T2 - Phys.Rev.D AB - We study instantons in QCD with many colors. We first discuss a number of qualitative arguments concerning the large ${N}_{c}$ scaling behavior of a random instanton ensemble. We show that most hadronic observables are compatible with standard large ${N}_{c}$ counting rules provided the average instanton size is $O(1)$ and the instanton density is ${O(N}_{c})$ in the large ${N}_{c}$ limit. This is not the case for the topological susceptibility and the mass of the ${\ensuremath{\eta}}^{\ensuremath{'}}.$ For these observables consistency with conventional large ${N}_{c}$ counting requires that fluctuations in the instanton liquid are suppressed compared to Poissonian fluctuations. Using mean field estimates and numerical simulations we show that the required scaling behavior of the instanton density is natural in models in which the instanton density is regularized in terms of a classical repulsive core. We also show that in these models fluctuations of the topological charge are suppressed and that ${m}_{{\ensuremath{\eta}}^{\ensuremath{'}}}^{2}{=O(1/N}_{c}).$ We conclude that the instanton liquid model is not necessarily in conflict with the ${1/N}_{c}$ expansion. DA - 2002/6// PY - 2002/6// DO - 10.1103/PhysRevD.66.076009 VL - 66 SP - 076009 UR - http://inspirehep.net/record/587993 ER - TY - JOUR TI - Background charge fluctuations and the transport properties of biopolymer-gold nanoparticle complexes AU - Berven, C. A. AU - Wybourne, M. N. AU - Clarke, L. AU - Longstreth, L. AU - Hutchison, J. E. AU - Mooster, J. L. T2 - Journal of Applied Physics AB - The room temperature electrical characteristics of biopolymer-gold nanoparticle complexes show threshold behavior, periodic conductance features, and current–voltage scaling that together indicate the nonlinear transport is associated with single electron charging. Repeated measurements over a period of up to 80 h showed the characteristics change with time. The current–voltage scaling behavior is found to be time independent, while the position of the conductance features shifted randomly over periods of many hours. We show that the time dependence is consistent with a fluctuating background charge distribution and can be understood within the framework of the orthodox model of single electron transport that is modified to account for the relatively large self-capacitance of the nanoparticles. DA - 2002/10// PY - 2002/10// DO - 10.1063/1.1506399 VL - 92 IS - 8 SP - 4513-4517 ER - TY - CONF TI - Interferometric method to characterize thermal elongation of near-field optics probes AU - La Rosa, A. AU - Biehler, B. AU - Sinharay, A. AU - Hallen, H. AB - This paper presents a new method that exploits the interference and polarization properties of light to monitor, in real time, the rapid thermal elongation of near-field optical probes. The typically flat (nanometer in size) morphology of the probe apex serves as one mirror of a Fabry-Perot type cavity; a flat semitransparent metal coated surface constitutes the other mirror. The optical-interferometry set-up permits distance acquisition with a high frequency bandwidth (compared to other methods based on electronic feedback) while control of the light polarization allows an increase of the signal to noise ratio of the measurements. C2 - 2002/// C3 - Proceedings of SPIE - The International Society for Optical Engineering CY - Seattle, WA, United states DA - 2002/// DO - 10.1117/12.472244 VL - 4777 SP - 420 - 423 UR - http://dx.doi.org/10.1117/12.472244 KW - near-field optics KW - Fabry-Perot cavity KW - thermal characterization ER - TY - JOUR TI - Raman selection rules in the presence of an electric field gradient AU - Jahncke, C. L. AU - Ayars, E. J. AU - Hallen, H. D. T2 - Microscopy and Microanalysis AB - Journal Article Raman selection rules in the presence of an electric field gradient Get access C L Jahncke, C L Jahncke Physics Department, St. Lawrence University, Canton, NY 13617 Search for other works by this author on: Oxford Academic Google Scholar E J Ayars, E J Ayars Physics Department, Walla Walla College, College Place, WA 99324 Search for other works by this author on: Oxford Academic Google Scholar H D Hallen H D Hallen Physics Department, North Carolina State University, Raleigh, NC 27695-8202 Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 8, Issue S02, 1 August 2002, Pages 1518–1519, https://doi.org/10.1017/S1431927602104223 Published: 01 August 2002 DA - 2002/// PY - 2002/// DO - 10.1017/S1431927602104223 VL - 8 IS - S02 SP - 1518-1519 UR - http://dx.doi.org/10.1017/S1431927602104223 ER - TY - CONF TI - Reliable adaptive modulation using long-range prediction at a different carrier frequency AU - Yang, Tung-Sheng AU - Duel-Hallen, A. AU - Hallen, H. AB - For fast vehicle speeds, reliable adaptive transmission requires prediction of future channel state information (CSI) since the channel conditions are rapidly time-variant. We propose to use past channel observations of one carrier to predict future CSI and perform adaptive modulation for another correlated carrier. A statistical model of the prediction error that depends on the frequency and time correlation is developed and is used in the design of reliable adaptive modulation methods. Significant gains relative to nonadaptive techniques are demonstrated for sufficiently correlated channels and realistic prediction range. Both Jakes (1974) fading model and a novel realistic physical model of frequency selective fading are used to validate performance of the proposed method. C2 - 2002/// C3 - Proceedings IEEE International Symposium on Information Theory, DA - 2002/// DO - 10.1109/ISIT.2002.1023631 SP - 359- UR - http://dx.doi.org/10.1109/ISIT.2002.1023631 ER - TY - CONF TI - Tunnel-Electron-Induced Oxygen Movement in YBa2Cu3O7-δ Measured with Near-Field Optical Microscopy AU - Huerth, S. H. AU - Hallen, H.D. C2 - 2002/// C3 - Proc. of the 7th International Conference on Near-field Optics, NFO-7 CY - Rochester, NY DA - 2002/// SP - 208 ER - TY - CONF TI - A physical model for wireless channels to provide insights for long range prediction AU - Hallen, Hans AU - Duel-Hallen, Alexandra AU - Hu, Shengquan AU - Yang, Tung-Shen AU - Lei, Ming AB - Algorithms that predict the wireless channel for up to a few wavelengths cannot be adequately tested with stationary models. Ray-tracing or FDTD methods do not provide insights into the relationship between reflector configurations and the performance of long-range prediction. Therefore, we present a novel model that: (1) creates non-stationary datasets to test our previously proposed adaptive long range prediction algorithm, which enables practical realization of adaptive transmission techniques; (2) classifies the reflector geometries that have typical or most severe parameter variations, so that the reflector configurations for test datasets can be appropriately chosen; (3) provides limits on the speed of adaptation needed for an algorithm to predict the channel significantly into the future, and thereby reveal the timing of future deep fades, etc.; (4) illuminates the origins of the temporal and statistical properties of measured data. The algorithm performs similarly on channels given by the physical model or actual measured data, but differently on a channel simulated by the stationary Jakes model. The insights of the model accurately describe the performance of the algorithm in several scattering environments when prediction is employed with adaptive power control and adaptive modulation. Moreover, we study limits of the long-range prediction at frequencies other than the observed frequency, of importance in correlated uplink and downlink transmission, orthogonal frequency division multiplexing (OFDM) and frequency-hopping systems. C2 - 2002/// C3 - Proceedings - IEEE Military Communications Conference MILCOM CY - Anaheim, CA, United states DA - 2002/// DO - 10.1109/MILCOM.2002.1180517 VL - 1 SP - 627 - 631 UR - http://dx.doi.org/10.1109/MILCOM.2002.1180517 ER - TY - CONF TI - Adaptive modulation for transmitter antenna diversity mobile radio systems AU - Hu, Shengquan AU - Duel-Hallen, A. AU - Hallen, H. AB - Adaptive transmission techniques such as adaptive modulation and transmitter antenna diversity have been proposed for mobile wireless systems to satisfy high data-rate service requirements. In rapidly time variant channels, these methods need the knowledge of future fading conditions and therefore require accurate long range fading prediction. We investigate three combined adaptive modulation and transmitter diversity schemes in conjunction with our previously proposed long-range fading channel prediction (LRP) algorithm. It is demonstrated that the novel combined schemes achieve significantly higher data rates than conventional adaptive modulation methods when aided by the LRP. Performance-complexity trade-off for several combined adaptive methods is examined. In addition to utilizing the Jakes fading model to test the proposed methods, we validate the LRP for antenna diversity systems using a novel realistic fading channel model. C2 - 2002/// C3 - Proceedings IEEE International Symposium on Information Theory, DA - 2002/// DO - 10.1109/ISIT.2002.1023377 SP - 105 UR - http://dx.doi.org/10.1109/ISIT.2002.1023377 ER - TY - CONF TI - Gradient-Field Raman: Selection Rules in the Near Field AU - Jahncke, C.L. AU - Ayars, E.J. AU - Hallen, H.D. C2 - 2002/// C3 - Proc. of the 7th International Conference on Near-field Optics, NFO-7 CY - Rochester, NY DA - 2002/// SP - 142 ER - TY - CONF TI - Bandwidth enhancement for shear-force feedback by exploiting the nonlinear probe-sample interaction AU - Jahncke, C.L. AU - Hallen, H.D. C2 - 2002/// C3 - Proc. of the 7th International Conference on Near-field Optics, NFO-7 CY - Rochester, NY DA - 2002/// SP - 41 ER - TY - JOUR TI - Magnetic trapping of ytterbium and the alkaline-earth metals AU - Loftus, T. AU - Bochinski, J. R. AU - Mossberg, T. W. T2 - Physical Review A AB - Atomic ytterbium (Yb), magnesium (Mg), calcium (Ca), and strontium (Sr) possess a simple yet versatile internal level structure and a diversity of naturally abundant fermionic and bosonic isotopes, making these systems ideal for studies of cold collisions and weakly interacting quantum degenerate gases. Unlike alkali-metal atoms, however, Yb, Mg, Ca, and Sr cannot be magnetically trapped in the ground state. We analyze a solution to this problem involving magnetic trapping in a low-lying metastable excited state and predict that significant magnetic trap populations can be obtained via continuous, in situ loading from Yb and Sr ${}^{1}{S}_{0}{\ensuremath{-}}^{1}{P}_{1}$ magneto-optical traps. DA - 2002/7// PY - 2002/7// DO - 10.1103/physreva.66.013411 VL - 66 IS - 1 ER - TY - JOUR TI - Near-field photoconductivity imaging of a conjugated polymer blend AU - Riehn, R. AU - Stevenson, R. AU - Halls, J.J.M. AU - Richards, D.R. AU - Kang, D.-J. AU - Blamire, M. AU - Cacialli, F. T2 - Materials Research Society Symposium - Proceedings DA - 2002/// PY - 2002/// VL - 708 SP - 71-76 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0036054160&partnerID=MN8TOARS ER - TY - JOUR TI - Coupled fermion and boson production in a strong background mean field AU - Vinnik, D.V. AU - Alkofer, Reinhard AU - Schmidt, S.M. AU - Smolyansky, S.A. AU - Skokov, V.V. AU - Prozorkevitch, A.V. T2 - Few-Body Systems AB - We derive quantum kinetic equations for fermion and boson production starting from a φ4 Lagrangean with minimal coupling to fermions. Decomposing the scalar field into a mean-field part and fluctuations we obtain spontaneous pair creation driven by a self-interacting strong background field. The produced fermion and boson pairs are self-consistently coupled. Consequently back reactions arise from fermion and boson currents determining the time-dependent self-interacting background mean field. We explore the numerical solution with cylindric boundary conditions for the time evolution of the mean field as well as for the number- and energy densities for fermions and bosons. We find that after a characteristic time all energy is converted from the background mean field to particle creation. Applying this general approach to the production of “quarks” and “gluons” a typical time scale for the collapse of the flux tube is 1.5 fm/c. DA - 2002/// PY - 2002/// DO - 10.1007/s00601-002-0110-8 VL - 32 IS - 1-2 SP - 23-39 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0036614309&partnerID=MN8TOARS ER - TY - PAT TI - Thin film optical measurement system and method with calibrating ellipsometer AU - Aspnes, D. E. AU - Opsal, J. AU - Faton, J. T. C2 - 2002/// DA - 2002/// PY - 2002/// ER - TY - PAT TI - Broadband spectroscopic rotating compensator ellipsometer AU - Aspnes, D. E. AU - Opsal, J. C2 - 2002/// DA - 2002/// PY - 2002/// ER - TY - JOUR TI - But are they learning? Getting started in classroom evaluation AU - Dancy, M. AU - Beichner, Robert T2 - Cell Biology Education AB - There are increasing numbers of traditional biologists, untrained in educational research methods, who want to develop and assess new classroom innovations. In this article we argue the necessity of formal research over normal classroom feedback. We also argue that traditionally trained biologists can make significant contributions to biology pedagogy. We then offer some guidance to the biologist with no formal educational research training who wants to get started. Specifically, we suggest ways to find out what others have done, we discuss the difference between qualitative and quantitative research, and we elaborate on the process of gaining insights from student interviews. We end with an example of a project that has used many different research techniques. DA - 2002/// PY - 2002/// DO - 10.1187/cbe.02-04-0010 VL - 1 SP - 87–94 ER - TY - JOUR TI - Defect Turbulence in Inclined Layer Convection AU - Daniels, Karen E. AU - Bodenschatz, Eberhard T2 - Physical Review Letters AB - We report experimental results on the defect turbulent state of undulation chaos in inclined layer convection of a fluid with Prandtl number approximately 1. By measuring defect density and undulation wave number, we find that the onset of undulation chaos coincides with the theoretically predicted onset for stable, stationary undulations. At stronger driving, we observe a competition between ordered undulations and undulation chaos, suggesting bistability between a fixed-point attractor and spatiotemporal chaos. In the defect turbulent regime, we measured the defect creation, annihilation, entering, leaving, and rates. We derive a universal probability distribution function which agrees with the experimental findings. DA - 2002/1/7/ PY - 2002/1/7/ DO - 10.1103/physrevlett.88.034501 VL - 88 IS - 3 SP - 034501 ER - TY - JOUR TI - Ultimate strength of carbon nanotubes: A theoretical study AU - Zhao, QZ AU - Nardelli, MB AU - Bernholc, J T2 - PHYSICAL REVIEW B AB - The ultimate strength of carbon nanotubes is investigated by large-scale quantum calculations. While the formation energy of strain-induced topological defects determines the thermodynamic limits of the elastic response and of mechanical resistance to applied tension, it is found that the activation barriers for the formation of such defects are much larger than estimated previously. The theoretical results indicate a substantially greater resilience and strength, and show that the ultimate strength limit of carbon nanotubes has yet to be reached experimentally. Nanotubes are indeed the strongest material known. DA - 2002/4/1/ PY - 2002/4/1/ DO - 10.1103/physrevb.65.144105 VL - 65 IS - 14 SP - SN - 2469-9969 ER - TY - JOUR TI - X-ray synchrotron-emitting Fe-rich ejecta in supernova remnant RCW 86 AU - Rho, JH AU - Dyer, KK AU - Borkowski, KJ AU - Reynolds, SP T2 - ASTROPHYSICAL JOURNAL AB - Supernova remnants may exhibit both thermal and nonthermal X-ray emission. In a previous study with ASCA data, we found that the middle-aged supernova remnant RCW 86 showed evidence for both processes, and we predicted that observations with much higher spatial resolution would distinguish harder X-rays, which we proposed were primarily synchrotron emission, from softer, thermal X-rays. Here we describe Chandra observations that amply confirm our predictions. Striking differences in the morphology of X-rays below 1 keV and above 2 keV point to a different physical origin. Hard X-ray emission is correlated fairly well with the edges of regions of radio emission, suggesting that these are the locations of shock waves at which both short-lived X-ray-emitting electrons and longer lived radio-emitting electrons are accelerated. Soft X-rays are spatially well correlated with optical emission from nonradiative shocks, which are almost certainly portions of the outer blast wave. These soft X-rays are well fitted with simple thermal plane-shock models. Harder X-rays show Fe Kα emission and are well described with a similar soft thermal component, but a much stronger synchrotron continuum dominating above 2 keV, and a strong Fe Kα line. Quantitative analysis of this line and the surrounding continuum shows that it cannot be produced by thermal emission from a cosmic-abundance plasma; the ionization time is too short, as shown by both the low centroid energy (6.4 keV) and the absence of oxygen lines below 1 keV. Instead, a model of a plane shock in Fe-rich ejecta, with a synchrotron continuum, provides a natural explanation. This requires that reverse shocks in ejecta be accelerating electrons to energies of order 50 TeV. We show that maximum energies of this order can be produced by radiation-limited diffusive shock acceleration at the reverse shocks. In the Appendix, we demonstrate that an explanation of the continuum as being due to nonthermal bremsstrahlung is unlikely. DA - 2002/12/20/ PY - 2002/12/20/ DO - 10.1086/344248 VL - 581 IS - 2 SP - 1116-1131 SN - 0004-637X KW - ISM : individual (RCW 86) KW - shock waves KW - supernova remnants KW - X-rays : ISM ER - TY - JOUR TI - Voltage- and temperature-dependent gate capacitance and current model: Application to ZrO2 n-channel MOS capacitor AU - Fan, YY AU - Nieh, RE AU - Lee, JC AU - Lucovsky, G AU - Brown, GA AU - Register, LF AU - Banerjee, SK T2 - IEEE TRANSACTIONS ON ELECTRON DEVICES AB - Based on the energy-dispersion relation in each region of the gate-dielectric-silicon system, a tunneling model is developed to understand the gate current as a function of voltage and temperature. The gate capacitance is self-consistently calculated from Schrodinger and Poisson equations subject to the Fermi-Dirac statistics, using the same band structure in the silicon as used for tunneling injection. Franz two-band dispersion is assumed in the dielectric bandgap. Using a Wentzel-Kramer-Brillouin (WKB)-based approach, direct and Fowler-Nordheim (FN) tunneling and thermionic emission are considered simultaneously. The model is implemented for both the silicon conduction and valence bands and both gate- and substrate-injected currents. ZrO/sub 2/ NMOSFETs were studied through temperature-dependent C/sub g/-V/sub g/ and I/sub g/-V, simulations. The extracted band gaps and band offsets of the ZrO/sub 2/- and interfacial-Zr-silicate-layer are found to be comparable with the reported values. The gate currents in ZrO/sub 2/-NMOSCAPs are found to be primarily contributed from the silicon conduction band and tunneling appears to be the most probable primary mechanism through the dielectric. Oscillations of gate currents and kinks of gate capacitance were observed near the flat-band in the experiments. These phenomena might be caused by the interface states. DA - 2002/11// PY - 2002/11// DO - 10.1109/TED.2002.804713 VL - 49 IS - 11 SP - 1969-1978 SN - 1557-9646 KW - high-K gate dielectric KW - leakage currents KW - MIS devices KW - MOSFETs KW - semiconductor device modeling KW - tunneling ER - TY - JOUR TI - Pseudodielectric functions of InGaAs alloy films grown on InP AU - Kim, TJ AU - Ihn, YS AU - Kim, YD AU - Kim, SJ AU - Aspnes, DE AU - Yao, T AU - Shim, K AU - Koo, BH T2 - APPLIED PHYSICS LETTERS AB - We present room-temperature pseudodielectric function spectra 〈ε〉 of InxGa1−xAs films grown on (100) InP by solid-source molecular-beam epitaxy. A wet-chemical etching procedure is used to remove overlayers and obtain the best approximation to the bulk dielectric responses ε of the films. By line shape fitting, we determined the x dependences of the E1 and E1+Δ1 critical-point energies and that of the Δ1 bowing parameter. The results are in good agreement with the predictions of a universal tight-binding model. DA - 2002/9/23/ PY - 2002/9/23/ DO - 10.1063/1.1509093 VL - 81 IS - 13 SP - 2367-2369 SN - 0003-6951 ER - TY - JOUR TI - Production of UCN by downscattering in superfluid He-4 AU - Korobkina, E AU - Golub, R AU - Wehring, BW AU - Young, AR T2 - PHYSICS LETTERS A AB - Ultra-Cold Neutrons (UCN) are neutrons with energies so low they can be stored in material bottles and magnetic traps. They have been used to provide the currently most accurate experiments on the neutron life time and electric dipole moment. UCN can be produced in superfluid Helium at significantly higher densities than by other methods. The predominant production process is usually by one phonon emission which can only occur at a single incident neutron energy because of momentum and energy conservation. However UCN can also be produced by multiphonon processes. It is the purpose of this work to examine this multiphonon production of UCN. We look at several different incident neutron spectra, including cases where the multiphonon production is significant, and see how the relative importance of multiphonon production is influenced by the incident spectrum. DA - 2002/9/2/ PY - 2002/9/2/ DO - 10.1016/S0375-9601(02)01052-6 VL - 301 IS - 5-6 SP - 462–469 SN - 0375-9601 KW - ultra-cold neutrons (UCN) KW - superthermal source KW - superfluid He-4 ER - TY - JOUR TI - Probing proton strangeness with time-like virtual Compton scattering AU - Cotanch, , SR AU - Williams, RA T2 - PHYSICS LETTERS B AB - We document that p(gamma,e+e-)p measurements will yield new, important information about the off-shell time-like nucleon form factors, especially in the phi meson region (q^2 = M^2_{phi}) governing the phi N couplings g^{V,T}_{\phi N N}. Calculations for p(gamma,e+e-)p, utilizing vector meson dominance, predict measurable phi enhancements at high |t| compared to the expected phi background production from pi, eta and Pomeron exchange. The phi form factor contribution generates a novel experimental signature for OZI violation and the proton strangeness content. The phi N couplings are determined independently from a combined analysis of the neutron electric form factor and recent high |t| phi photoproduction. The pi, eta and Pomeron transition form factors are also predicted and the observed pi and eta transition moments are reproduced. DA - 2002/11/28/ PY - 2002/11/28/ DO - 10.1016/S0370-2693(02)02869-1 VL - 549 IS - 1-2 SP - 85-92 SN - 1873-2445 KW - Compton scattering KW - phi photoproduction KW - vector meson dominance KW - nucleon form factors KW - nucleon strangeness KW - phi N coupling ER - TY - JOUR TI - Quantum Monte Carlo methods for electronic structure of nanosystems AU - Mitas, L T2 - ISRAEL JOURNAL OF CHEMISTRY AB - Abstract We provide a brief review of recent applications of quantum Monte Carlo (QMC) methods to the electronic structure of nanosystems. We report on calculations of carbon rings with second‐order Jahn‐Teller effect, energy ordering of silicon clusters, dissociation enthalpies of protonated hydrogen clusters, and other interesting challenges. We point out the QMC accuracy and outline a few ideas that characterize the current position of QMC among the electronic structure methods and its future development. DA - 2002/// PY - 2002/// DO - 10.1560/QRWB-75NV-MEL1-D124 VL - 42 IS - 2-3 SP - 261-268 SN - 0021-2148 ER - TY - JOUR TI - Nanotribology of a vapor-phase lubricant: A quartz crystal microbalance study of tricresylphosphate (TCP) uptake on iron and chromium AU - Abdelmaksoud, M AU - Bender, JW AU - Krim, J T2 - TRIBOLOGY LETTERS DA - 2002/10// PY - 2002/10// DO - 10.1023/A:1020155925183 VL - 13 IS - 3 SP - 179-186 SN - 1573-2711 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-2942624398&partnerID=MN8TOARS KW - tribology KW - nanotribology KW - TCP KW - QCM KW - vapor-phase lubrication ER - TY - JOUR TI - Energy levels of light nuclei A=5, 6, 7 AU - Tilley, DR AU - Cheves, CM AU - Godwin, JL AU - Hale, GM AU - Hofmann, HM AU - Kelley, JH AU - Sheu, CG AU - Weller, HR T2 - NUCLEAR PHYSICS A AB - A review of the evidence on the properties of the nuclei A=5, 6 and 7, with emphasis on material leading to information about the structure of the A=5, 6, 7 systems. (References closed 23 August 2001.) DA - 2002/9/23/ PY - 2002/9/23/ DO - 10.1016/S0375-9474(02)00597-3 VL - 708 IS - 1-2 SP - 3-163 SN - 1873-1554 ER - TY - JOUR TI - Continuity of generalized parton distributions for the pion virtual Compton scattering AU - Choi, H. M. AU - Ji, C. R. AU - Kisslinger, L. S. T2 - Physical Review. D, Particles and Fields DA - 2002/// PY - 2002/// VL - 66 IS - 5 SP - 053011-1 ER - TY - JOUR TI - Comparison of X-ray detectors for a diffraction enhanced imaging system AU - Kiss, MZ AU - Sayers, DE AU - Zhong, Z T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB - Three digital detector systems—a Fuji BAS2500 Image Plate Reader, a prototype charge-coupled device (CCD) from Mar USA and the MicroPhotonics XQUIS 1000 were compared with respect to format, dynamic range, dark noise, and spatial resolution. Experiments were conducted using highly collimated monochromatic X-rays at 20 keV, produced at the National Synchrotron Light Source. This study characterized digital detectors being considered for integration into a synchrotron-based diffraction enhanced imaging (DEI) apparatus used for medical imaging research, particularly mammography. These detectors are also being considered for integration into a proposed clinical prototype for DEI-based mammography. While all three systems had comparable image quality, the CCDs had faster readout time than the image plate system. However, the Fuji system had the largest dynamic range (∼10 5 compared to 10 4 for CCDs) and the largest active area. The MicroPhotonics XQUIS 1000 had the best spatial resolution as characterized by the point spread function. DA - 2002/9/21/ PY - 2002/9/21/ DO - 10.1016/S0168-9002(02)01125-7 VL - 491 IS - 1-2 SP - 280-290 SN - 1872-9576 KW - digital detector KW - image plate KW - CCD KW - point spread function KW - synchrotron KW - modulation transfer function KW - diffraction enhanced imaging ER - TY - JOUR TI - UV detectors and focal plane array imagers based on AlGaN p-i-n photodiodes AU - Long, J. P. AU - Varadaraajan, S. AU - Matthews, J. AU - Schetzina, J. F. T2 - Opto-electronics Review DA - 2002/// PY - 2002/// VL - 10 IS - 4 SP - 251-260 ER - TY - JOUR TI - Structure and energetics of Ga-rich GaAs(001) surfaces AU - Seino, K AU - Schmidt, WG AU - Bechstedt, F AU - Bernholc, J T2 - SURFACE SCIENCE AB - The atomic structures and energies of Ga-rich GaAs(0 0 1) surface reconstructions are examined by means of first-principles total-energy calculations based on a real-space multigrid method. Our calculations confirm the existence of the novel ζ(4×2) structure suggested by Lee et al. [Phys. Rev. Lett. 85 (2000) 3890]. (4×6) surface reconstructions suggested to explain STM experiments are found to be unstable. The calculations indicate that the adsorption of Ga adatoms in the trenches of the ζ(4×2) surface could possibly explain the observed structures. The diffusion of Ga/As adatoms on the Ga-rich GaAs surface is predicted to be anisotropic and should preferably take place parallel to the [1 1 0]/[1 1̄ 0] direction, respectively. DA - 2002/6/1/ PY - 2002/6/1/ DO - 10.1016/S0039-6028(02)01278-5 VL - 507 IS - 2002 Jun 1 SP - 406-410 SN - 0039-6028 KW - gallium arsenide KW - single crystal surfaces KW - density functional calculations KW - surface diffusion ER - TY - JOUR TI - States in Pt-196 observed with the (n,n 'gamma) reaction AU - Tavukcu, E. AU - Bernstein, L. A. AU - Hauschild, K. AU - Becker, J. A. AU - Garrett, P. E. AU - Mcgrath, C. A. AU - McNabb, D. P. AU - Younes, W. AU - Navratil, P. AU - Nelson, R. O. AU - Johns, G. D. AU - Mitchell, G. E. AU - Cizewski, J. A. T2 - Physical Review. C, Nuclear Physics DA - 2002/// PY - 2002/// VL - 65 IS - 6 SP - 064309-1 ER - TY - JOUR TI - QCD based quark description of pi-pi scattering up to the sigma and rho regions AU - Cotanch, , SR AU - Maris, P T2 - PHYSICAL REVIEW D AB - We study forward and backward pi-pi scattering within a QCD model based on the Dyson--Schwinger, Bethe--Salpeter equations truncated to the rainbow-ladder level. Our microscopic relativistic quark formulation preserves chiral symmetry and reproduces the observed scattering lengths for total isospin zero, one and two. At higher energies both scalar and vector meson resonances naturally occur in the scattering amplitudes. We also report a comparative study with phenomenological meson-exchange models and find such approaches are reasonable especially near pi-pi resonances. DA - 2002/12/1/ PY - 2002/12/1/ DO - 10.1103/physrevd.66.116010 VL - 66 IS - 11 SP - SN - 1550-2368 ER - TY - JOUR TI - Ohmic contacts on n-type Al0.59Ga0.41N for solar blind detectors AU - Selvanathan, D AU - Zhou, L AU - Kumar, V AU - Adesida, I AU - Long, JP AU - Johnson, MAL AU - Schetzina, JF T2 - ELECTRONICS LETTERS AB - Low-resistance ohmic contacts on Al0.59Ga0.41N were formed using a Ti/Al/Mo/Au metallisation scheme. A specific contact resistivity as low as 6×10−5 Ω-cm2 was achieved using a pre-metallisation treatment of the surface in an SiCl4 plasma with a self-bias voltage of −300 V in a reactive ion etching system. DA - 2002/7/4/ PY - 2002/7/4/ DO - 10.1049/el:20020500 VL - 38 IS - 14 SP - 755-756 SN - 0013-5194 ER - TY - JOUR TI - Interplay of surface reconstruction and surface electric fields in the optical anisotropy of GaAs(001) AU - Schmidt, W. G. AU - Bechstedt, F. AU - Lu, W. AU - Bernholc, J. T2 - Physical Review. B, Condensed Matter and Materials Physics DA - 2002/// PY - 2002/// VL - 66 IS - 8 SP - 085334-1 ER - TY - JOUR TI - Identification and quantitation of urea precipitates in flexible polyurethane foam formulations by X-ray spectromicroscopy AU - Rightor, EG AU - Urquhart, SG AU - Hitchcock, AP AU - Ade, H AU - Smith, AP AU - Mitchell, GE AU - Priester, RD AU - Aneja, A AU - Appel, G AU - Wilkes, G AU - Lidy, WE T2 - MACROMOLECULES AB - Scanning transmission X-ray microscopy (STXM) and atomic force microscopy have been used to study the morphology and chemical composition of macrophase-segregated block copolymers in plaque formulations based on water-blown flexible polyurethane foams. Although there has been a large body of indirect evidence indicating that the observed macrophase-segregated features in water-rich polyurethane foams are due principally to urea components, this work provides the first direct, spatially resolved spectroscopic proof to support this hypothesis. The STXM results are consistent with a segregation model where urea segments segregate, forming enriched phases with the majority of the polyether−polyol and urethane groups at the chain ends of the urea hard segments. Chemical mapping of the urea, urethane, and polyether distribution about the urea-rich segregated phases showed that the urea concentration changes gradually (across several hundred nanometers) in a butylene oxide-based foam. This mapping also showed the urea-rich segregated phases present as a partial network in an ethylene oxide/propylene oxide sample. DA - 2002/7/16/ PY - 2002/7/16/ DO - 10.1021/ma0122627 VL - 35 IS - 15 SP - 5873-5882 SN - 1520-5835 ER - TY - JOUR TI - Trends in the carbonyl core (C 1s, O 1s) -> pi*c=o transition in the near-edge X-ray absorption fine structure spectra of organic molecules AU - Urquhart, SG AU - Ade, H T2 - JOURNAL OF PHYSICAL CHEMISTRY B AB - Carbonyl core (C 1s, O 1s) → π*CO transitions are distinctive in the near-edge X-ray absorption fine structure (NEXAFS) spectra of species containing carbonyl groups. These features are used for the chemical microanalysis of organic materials using X-ray microscopy. We have explored the chemical sensitivity of these features in C 1s and O 1s NEXAFS spectra for a series of polymers containing the carbonyl group in a range of different bonding environments. Ab initio calculations are used to explain the origin of the observed trends and to explore the effect that orbital interactions have on the energy of these core (C 1s, O 1s) → π*CO features. The differences between the experimental and the calculated carbonyl core (C 1s, O 1s) → π*CO transition energies are systematic and can be used to develop a semiempirical method for predicting the absolute (experimental) transition energies from the calculated transition energies. This relationship is applied to a large body of calculated transition energy data to prepare correlation diagrams for the carbonyl (C 1s, O 1s) → π*CO transitions. These correlation diagrams will be useful for the analytical application of NEXAFS spectroscopy to organic materials. DA - 2002/8/29/ PY - 2002/8/29/ DO - 10.1021/jp0255379 VL - 106 IS - 34 SP - 8531-8538 SN - 1520-6106 ER - TY - JOUR TI - Origins of silicon solar cell passivation by SiNx : H anneal AU - Boehme, C AU - Lucovsky, G T2 - JOURNAL OF NON-CRYSTALLINE SOLIDS AB - The origin of silicon solar cell passivation by the post-deposition anneal of hydrogenated silicon nitride (SiNx:H) anti-reflection (AR) coatings is investigated. The diffusion of hydrogen (H) in SiNx:H is dominated by fast diffusion of molecular hydrogen (H2) and ammonia (NH3) and not by slow atomic diffusion through covalent bonding sites. An anneal of the SiNx:H layers leads therefore to a rapid H loss into the environment and not into the silicon bulk. Instead of bulk passivation by H atoms, the improvement of the electronic properties is due to an Si/SiNx:H-interface passivation caused by the formation of a few monolayers of silicon dioxide, which removes the bonding topology related stress at the interface. Secondary ion mass spectroscopy (SIMS) scans on various Si/SiNx:H stacks with mono- and polycrystalline substrates and remote and direct plasma enhanced chemical vapor deposited nitrides were carried out and showed strong interface accumulation of oxygen. DA - 2002/4/1/ PY - 2002/4/1/ DO - 10.1016/S0022-3093(01)01135-8 VL - 299 SP - 1157-1161 SN - 0022-3093 ER - TY - JOUR TI - Long-term reliability degradation of ultrathin dielectric films due to heavy-ion irradiation AU - Choi, BK AU - Fleetwood, DM AU - Schrimpf, RD AU - Massengill, LW AU - Galloway, KF AU - Shaneyfelt, MR AU - Meisenheimer, TL AU - Dodd, PE AU - Schwank, , JR AU - Lee, YM AU - John, RS AU - Lucovsky, G T2 - IEEE TRANSACTIONS ON NUCLEAR SCIENCE AB - High-energy ion-irradiated 3.3-nm oxynitride film and 2.2-nm SiO/sub 2/-film MOS capacitors show premature breakdown during subsequent electrical stress. This degradation in breakdown increases with increasing ion linear energy transfer (LET), increasing ion fluence, and decreasing oxide thickness. The reliability degradation due to high-energy ion-induced latent defects is explained by a simple percolation model of conduction through SiO/sub 2/ layers with irradiation and/or electrical stress-induced defects. Monitoring the gate-leakage current reveals the presence of latent defects in the dielectric films. These results may be significant to future single-event effects and single-event gate rupture tests for MOS devices and ICs with ultrathin gate oxides. DA - 2002/12// PY - 2002/12// DO - 10.1109/TNS.2002.805389 VL - 49 IS - 6 SP - 3045-3050 SN - 1558-1578 KW - heavy-ion irradiation KW - radiation effect KW - single-event effect KW - ultra-thin gate dielectric films ER - TY - JOUR TI - Intrinsic electron transport properties of carbon nanotube Y-junctions AU - Meunier, V AU - Nardelli, MB AU - Bernholc, J AU - Zacharia, T AU - Charlier, JC T2 - APPLIED PHYSICS LETTERS AB - The electron transport properties of three-terminal carbon-nanotube junctions are investigated within the Landauer theory of quantum conductance. Using a realistic tight-binding Hamiltonian, we demonstrate that the experimentally observed rectifying behavior is not an intrinsic property of the junction, but rather of the contact geometry. When semiconducting nanotubes are connected to metallic leads, nontransmitting states are induced at the nanotube–metal interface, leading to asymmetric transmission curves and potentially rectifying behavior of the nanodevice. DA - 2002/12/30/ PY - 2002/12/30/ DO - 10.1063/1.1533842 VL - 81 IS - 27 SP - 5234-5236 SN - 0003-6951 ER - TY - JOUR TI - Effects of surface termination on the band gap of ultrabright Si-29 nanoparticles: Experiments and computational models AU - Belomoin, G AU - Rogozhina, E AU - Therrien, J AU - Braun, PV AU - Abuhassan, L AU - Nayfeh, MH AU - Wagner, L AU - Mitas, L T2 - PHYSICAL REVIEW B AB - A ${\mathrm{Si}}_{29}{\mathrm{H}}_{24}$ particle, with five atoms constituting a tetrahedral core and 24 atoms constituting a H-terminated reconstructed Si surface was recently proposed as a structural prototype of ultrasmall ultrabright particles prepared by electrochemical dispersion from bulk Si. We replace the H termination with a N linkage (in butylamine) and O linkage (in pentane). The emission band for N-termination downshifts by \ensuremath{\sim}0.25 eV from that of H termination, whereas it blueshift \ensuremath{\sim}0.070 eV for C termination. We use density-functional approaches to calculate the atomic structures and correction from the quantum Monte Carlo method to estimate the highest occupied--lowest unoccupied molecular-orbital band gap. We find a downshift of 0.25 eV for N termination and very little for C termination. These features are discussed in terms of exciton penetration in the capping material. DA - 2002/5/15/ PY - 2002/5/15/ DO - 10.1103/physrevb.65.193406 VL - 65 IS - 19 SP - SN - 1098-0121 ER - TY - JOUR TI - Correlations between electronic structure of transition metal atoms and performance of high-k gate dielectrics in advanced Si devices AU - Lucovsky, G T2 - JOURNAL OF NON-CRYSTALLINE SOLIDS AB - This paper develops a classification scheme for non-crystalline dielectrics that separates them into three groups with different amorphous morphologies, and identifies a linear scaling relationship between average bond ionicity and oxygen atom coordination. The classification scheme is applied to transition metal silicate and aluminate alloys and provides a structural model for molecular orbital, MO, calculations that are based on the coordination and symmetry of transition metal atoms and the orbital energies of their oxygen neighbors. The MO calculations show that conduction band offset energies with respect to Si scale inversely with the energy difference between transition metal atomic n+1 s- and n d-states providing an important insight into the choice of alternative gate dielectrics for advanced Si devices. DA - 2002/5/1/ PY - 2002/5/1/ DO - 10.1016/S0022-3093(02)00962-6 VL - 303 IS - 1 SP - 40-49 SN - 1873-4812 ER - TY - JOUR TI - Characterization of charge-carrier dynamics in thin oxide layers on silicon by second harmonic generation AU - Glinka, Y. D. AU - Wang, W. AU - Singh, S. K. AU - Marka, Z. AU - Rashkeev, S. N. AU - Shirokaya, Y. AU - Albridge, R. AU - Pantelides, S. T. AU - Tolk, N. H. AU - Lucovsky, G. T2 - Physical Review. B, Condensed Matter and Materials Physics DA - 2002/// PY - 2002/// VL - 65 IS - 19 SP - 193103-1 ER - TY - JOUR TI - Amorphous morphology, thermal stability and electronic structure of non-crystalline transition-metal elemental and binary oxides, and chalcogenides AU - Lucovsky, G T2 - JOURNAL OF NON-CRYSTALLINE SOLIDS AB - The primary motivation for this research is to identify alternative high-k gate dielectrics for advanced crystalline Si complementary metal oxide semiconductor (CMOS) devices. A novel and systematic approach to the classification of candidate elemental and binary non-crystalline oxides that is based on relative bond ionicity separates these dielectrics into three groups with different amorphous morphologies: continuous random networks, modified continuous random networks in which metal atoms disrupt and modify the covalently bonded network structure, and random close packed ionic structures. This approach identifies the importance of the oxygen atom co-ordination, providing useful insights into the bonding in chalcogenide alloys as well. DA - 2002/4/1/ PY - 2002/4/1/ DO - 10.1016/S0022-3093(01)01162-0 VL - 299 SP - 231-237 SN - 1873-4812 ER - TY - JOUR TI - Vertically scaled MOSFET gate stacks and junctions: How far are we likely to go? AU - Osburn, CM AU - Kim, I AU - Han, SK AU - De, I AU - Yee, KF AU - Gannavaram, S AU - Lee, SJ AU - Lee, CH AU - Luo, ZJ AU - Zhu, W AU - Hauser, , JR AU - Kwong, DL AU - Lucovsky, G AU - Ma, TP AU - Ozturk, MC T2 - IBM JOURNAL OF RESEARCH AND DEVELOPMENT AB - The vertical scaling requirements for gate stacks and for shallow extension junctions are reviewed. For gate stacks, considerable progress has been made in optimizing oxide/nitride and oxynitride dielectrics to reduce boron penetration and dielectric leakage compared to pure SiO 2 in order to allow sub-2-nm dielectrics. Several promising alternative material candidates exist for 1-nm equivalent oxide thickness (EOT)—for example, HfO 2 , ZrO 2 , and their silicates. Nevertheless, considerable challenges lie ahead if we are to achieve an EOT of less than 0.5 nm. If only a single molecular interface layer of oxide is needed to preserve high channel mobility, it seems likely that an EOT of 0.4–0.5 nm would represent the physical limit of dielectric scaling, but even then with a very high leakage (∼10 5 A/cm 2 ). For junctions, the main challenge lies in providing low parasitic series resistance as depths are scaled in order to reduce short-channel effects. Because contacts are ultimately expected to dominate the parasitic resistance, low-barrier-height contacts and/or very heavily doped junctions will be required. While ion implantation and annealing processes can certainly be extended to meet the junction-depth and series-resistance requirements for additional generations, alternative low-temperature deposition processes that produce either metastably or extraordinarily activated, abruptly doped regions seem better suited to solve the contact resistance problem. DA - 2002/// PY - 2002/// DO - 10.1147/rd.462.0299 VL - 46 IS - 2-3 SP - 299-315 SN - 2151-8556 ER - TY - JOUR TI - Total-dose radiation response of hafnium-silicate capacitors AU - Felix, JA AU - Fleetwood, DM AU - Schrimpf, RD AU - Hong, JG AU - Lucovsky, G AU - Schwank, , JR AU - Shaneyfelt, MR T2 - IEEE TRANSACTIONS ON NUCLEAR SCIENCE AB - Hafnium-silicate capacitors with 4.5-nm equivalent oxide thickness gate insulators were irradiated with 10-keV X-rays. The midgap and flatband voltage shifts in these devices increase linearly with dose and are significantly larger than the shifts seen in high quality, thermal SiO/sub 2/ gate oxides of similar electrical thickness. The standard trapping efficiency equation is adapted for calculating effective trapping efficiencies in alternative dielectrics and used to compare the radiation response of hafnium silicate to SiO/sub 2/ from several manufacturers. The effects of common reliability screens such as "burn-in" and bias stress tests are also discussed. It is shown that baking these devices can degrade their capacitance-voltage characteristics, and large applied voltages inject excess charge into the dielectric, which can lead to a misinterpretation of the radiation results. However, the radiation responses of these devices, coupled with the demonstrated resistance of these films to heavy-ion induced gate rupture in previous studies, suggest that alternative dielectrics to SiO/sub 2/ potentially could be integrated into future electronics technologies for many low-power space applications. DA - 2002/12// PY - 2002/12// DO - 10.1109/TNS.2002.805392 VL - 49 IS - 6 SP - 3191-3196 SN - 1558-1578 KW - alternative dielectric film KW - burn-in effects KW - MOS capacitor KW - oxide trapped KW - radiation effects ER - TY - JOUR TI - Testing the utility of vertebrate remains in recognizing patterns in fluvial deposits: An example from the lower Horseshoe Canyon Formation, Alberta AU - Straight, WH AU - Eberth, DA T2 - PALAIOS AB - Other| October 01, 2002 Testing the Utility of Vertebrate Remains in Recognizing Patterns in Fluvial Deposits: An Example from the Lower Horseshoe Canyon Formation, Alberta WILLIAM H. STRAIGHT; WILLIAM H. STRAIGHT 1Marine, Earth, and Atmospheric Sciences Department, Box 8208, North Carolina State University, Raleigh, NC 27695 Search for other works by this author on: GSW Google Scholar DAVID A. EBERTH DAVID A. EBERTH 2Royal Tyrrell Museum of Palaeontology, Box 7500, Drumheller AB T0J 0Y0, Canada Search for other works by this author on: GSW Google Scholar Author and Article Information WILLIAM H. STRAIGHT 1Marine, Earth, and Atmospheric Sciences Department, Box 8208, North Carolina State University, Raleigh, NC 27695 DAVID A. EBERTH 2Royal Tyrrell Museum of Palaeontology, Box 7500, Drumheller AB T0J 0Y0, Canada Publisher: SEPM Society for Sedimentary Geology Accepted: 10 Mar 2002 First Online: 03 Mar 2017 Online ISSN: 1938-5323 Print ISSN: 0883-1351 Society for Sedimentary Geology PALAIOS (2002) 17 (5): 472–490. https://doi.org/10.1669/0883-1351(2002)017<0472:TTUOVR>2.0.CO;2 Article history Accepted: 10 Mar 2002 First Online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation WILLIAM H. STRAIGHT, DAVID A. EBERTH; Testing the Utility of Vertebrate Remains in Recognizing Patterns in Fluvial Deposits: An Example from the Lower Horseshoe Canyon Formation, Alberta. PALAIOS 2002;; 17 (5): 472–490. doi: https://doi.org/10.1669/0883-1351(2002)017<0472:TTUOVR>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyPALAIOS Search Advanced Search Abstract Depositional cycles in fluvial successions are described here as chronostratigraphic packages of strata founded on a laterally extensive, scour-based, amalgamated channel-sand body, overlain by mudrocks, isolated channel fills, avulsion and splay complexes, and paleosols. Ten packages are described from the lower Horseshoe Canyon Formation (Campanian-Maastrichtian), one of a succession of clastic wedges filling the Alberta foreland basin in south-central Alberta. The structure of these packages is consistent with the fall-rise-fall cycle of base-level described in other studies, but the package-bounding scours and internal surfaces are discontinuous and difficult to trace in the mudrock-dominated strata. Terrestrial vertebrate fossils are preserved in relatively fossiliferous, facies-independent horizons 1 to 3 m thick that statistically correlate with the stratigraphic position of package scours and surfaces. Fossiliferous horizons formed as a result of attritional accumulation under an optimum, relatively low, regional deposition rate. Not only do these horizons aid in locating package surfaces, but they also provide insight to the interaction of the package-scale, base-level oscillation with the larger-scale fluctuation in accommodation associated with the formation of the clastic wedge. As such, fossiliferous horizons in the Horseshoe Canyon Formation make better boundary markers than do paleosols, splays, coal seams, or even the surfaces associated with package structure. Therefore, the vertebrate fossil record may supply a means of stratigraphically evaluating sections in other locations in which typical sedimentological and architectural cues for surfaces are absent. You do not have access to this content, please speak to your institutional administrator if you feel you should have access. DA - 2002/10// PY - 2002/10// DO - 10.1669/0883-1351(2002)017<0472:TTUOVR>2.0.CO;2 VL - 17 IS - 5 SP - 472-490 SN - 0883-1351 ER - TY - JOUR TI - Piezoresponse force microscopy for piezoelectric measurements of III-nitride materials AU - Rodriguez, BJ AU - Gruverman, A AU - Kingon, AI AU - Nemanich, RJ T2 - JOURNAL OF CRYSTAL GROWTH AB - Piezoelectric constants and polarity distributions of epitaxial AlN and GaN thin films are investigated by piezoresponse force microscopy (PFM). The magnitude of the effective longitudinal piezoelectric constant d33 is determined to be 3±1 and 2±1 pm/V for wurtzite AlN and GaN/AlN layers grown by organo-metallic vapor phase epitaxy on SiC substrates, respectively. Simultaneous imaging of surface morphology as well as the phase and magnitude of the piezoelectric response is performed by PFM on a GaN film with patterned polarities on a c-Al2O3 substrate. We demonstrate that the polarity distribution of GaN based lateral polarity heterostructures can be deduced from the phase image of the piezoresponse with nanometer scale spatial resolution. We also present images of AlN/Si samples with regions of opposite piezoresponse phase, which indicate the presence of antiphase domains. We discuss the potential application of this technique for determination of the orientation of bulk crystals. DA - 2002/12// PY - 2002/12// DO - 10.1016/S0022-0248(02)01749-9 VL - 246 IS - 3-4 SP - 252-258 SN - 0022-0248 KW - Al. atomic force microscopy KW - B2. piezoelectric materials KW - B2. semiconducting III-V materials ER - TY - JOUR TI - Pd growth and subsequent Schottky barrier formation on chemical vapor cleaned p-type GaN surfaces AU - Hartlieb, PJ AU - Roskowski, A AU - Davis, RF AU - Platow, W AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - Characterization of chemical vapor cleaned, Mg-doped, p-type GaN(0001) surfaces and Pd contacts sequentially deposited on these surfaces has been conducted using x-ray and ultraviolet photoelectron spectroscopies and low-energy electron diffraction. The band bending and the electron affinity at the cleaned p-GaN surface were 1.4±0.1 eV and 3.1±0.1 eV, respectively. A previously unidentified band of surface states was observed at ∼1.0 eV below the Fermi level on this surface. The Pd grew epitaxially on the cleaned surface in a layer-by-layer mode and formed an abrupt, unreacted metal–semiconductor interface. The induced Fermi level movement with Pd deposition has been attributed to a complex interaction between extrinsic and intrinsic surface states as well as metal induced gap states. The final Schottky barrier height at the Pd/p-GaN interface was 1.3±0.1 eV; the interface dipole contribution was 0.4±0.1 eV. DA - 2002/1/15/ PY - 2002/1/15/ DO - 10.1063/1.1424060 VL - 91 IS - 2 SP - 732-738 SN - 1089-7550 ER - TY - JOUR TI - Nonlinear particle acceleration in relativistic shocks AU - Ellison, DC AU - Double, GP T2 - ASTROPARTICLE PHYSICS AB - Monte Carlo techniques are used to model nonlinear particle acceleration in parallel collisionless shocks of various speeds, including mildly relativistic ones. When the acceleration is efficient, the backreaction of accelerated particles modifies the shock structure and causes the compression ratio, r, to increase above test-particle values. Modified shocks with Lorentz factors, γ0≲3, can have compression ratios considerably >3 and the momentum distribution of energetic particles no longer follows a power law relation. These results may be important for the interpretation of gamma-ray bursts if mildly relativistic internal and/or afterglow shocks play an important role accelerating particles that produce the observed radiation. For γ0≳10, r approaches 3 and the so-called ‘universal’ test-particle result of N(E)∝E−2.3 is obtained for sufficiently energetic particles. In all cases, the absolute normalization of the particle distribution follows directly from our model assumptions and is explicitly determined. DA - 2002/12// PY - 2002/12// DO - 10.1016/S0927-6505(02)00142-1 VL - 18 IS - 3 SP - 213-228 SN - 0927-6505 KW - cosmic rays KW - acceleration of particles KW - relativistic shock waves KW - gamma-ray bursts ER - TY - JOUR TI - Measurements of ultracold-neutron lifetimes in solid deuterium AU - Morris, CL AU - Anaya, JM AU - Bowles, TJ AU - Filippone, BW AU - Geltenbort, P AU - Hill, RE AU - Hino, M AU - Hoedl, S AU - Hogan, GE AU - Ito, TM AU - Kawai, T AU - Kirch, K AU - Lamoreaux, SK AU - Liu, CY AU - Makela, M AU - Marek, LJ AU - Martin, JW AU - Mortensen, RN AU - Pichlmaier, A AU - Saunders, A AU - Seestrom, SJ AU - Smith, D AU - Teasdale, W AU - Tipton, B AU - Utsuro, M AU - Young, AR AU - Yuan, J T2 - PHYSICAL REVIEW LETTERS AB - We present the first measurements of the survival time of ultracold neutrons (UCNs) in solid deuterium (SD2). This critical parameter provides a fundamental limitation to the effectiveness of superthermal UCN sources that utilize solid ortho-deuterium as the source material. These measurements are performed utilizing a SD2 source coupled to a spallation source of neutrons, providing a demonstration of UCN production in this geometry and permitting systematic studies of the influence of thermal up-scatter and contamination with para-deuterium on the UCN survival time. DA - 2002/12/30/ PY - 2002/12/30/ DO - 10.1103/physrevlett.89.272501 VL - 89 IS - 27 SN - 0031-9007 ER - TY - JOUR TI - Er-doped AlGaAs native oxides: Photoluminescence characterization and process optimization AU - Kou, LG AU - Hall, DC AU - Strohhofer, C AU - Polman, A AU - Zhang, T AU - Kolbas, RM AU - Heller, RD AU - Dupuis, RD T2 - IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS AB - We present 300 K photoluminescence (PL) characterization data for wet thermal native oxides of Al/sub 0.58/Ga/sub 0.42/As films grown by metal organic chemical vapor deposition and doped with Er via multiple high-energy ion implants (for 0.0675, 0.135, and 0.27 atomic percent (at.%) peak Er concentrations), and Al/sub 0.5/Ga/sub 0.5/As and Al/sub 0.8/In/sub 0.2/As films doped with Er (0.03-0.26 at.%) during molecular beam epitaxy crystal growth. Broad spectra with a /spl sim/50-nm full-width at half-maximum and a PL peak at 1.534 /spl mu/m are observed, characteristic of Al/sub 2/O/sub 3/:Er films. The dependencies of PL intensity, spectra, and lifetime on annealing temperature (675/spl deg/C-900/spl deg/C), time (2-60 min) and As overpressure (0-0.82 atm) are studied to optimize the annealing process, with As considered as a possible quenching mechanism. Wet and dry-oxidized films are compared to explore the role of hydroxyl (OH) groups identified by Fourier transform infrared (FTIR) spectroscopy. FTIR experiments employing heavy water (D/sub 2/O) suggest that OH groups in wet oxidized AlGaAs come mainly from post-oxidation adsorption of atmospheric moisture. AlGaAs:Er films wet oxidized with 0.1% O/sub 2/ added to the N/sub 2/ carrier gas show a fourfold PL intensity increase, doubled PL lifetime to /spl tau//spl sim/5.0 ms (0.27 at.% implanted sample), and the lowest degree of concentration quenching. DA - 2002/// PY - 2002/// DO - 10.1109/JSTQE.2002.801689 VL - 8 IS - 4 SP - 880-890 SN - 1077-260X KW - aluminum alloys KW - erbium KW - integrated optoelectronics KW - materials processing KW - optical amplifiers KW - oxidation KW - photoluminescence KW - semiconductor films ER - TY - JOUR TI - Electron trapping in non-crystalline Ta- and Hf-aluminates for gate dielectric applications in aggressively scaled silicon devices AU - Johnson, RS AU - Hong, JG AU - Hinkle, C AU - Lucovsky, G T2 - SOLID-STATE ELECTRONICS AB - Abstract The physical and electrical properties of non-crystalline Ta- and Hf-alumiunates, (Ta 2 O 5 ) x (Al 2 O 3 ) 1− x and (HfO 2 ) x (Al 2 O 3 ) 1− x , respectively, were studied. As-deposited films were homogeneous and pseudo-binary in character with increased thermal stability with respect to the respective end-member oxides. Capacitance–voltage and current density–voltage data as a function of temperature demonstrate that the Ta and Hf d-states of the alloys act as localized electron traps, and are at an energy approximately equal to the conduction band offset of Ta 2 O 5 and HfO 2 with respect to Si. This work correlates the studies of Ta- and Hf-aluminates to develop a qualitative conduction band energy level scheme for the two alloys where the interfacial electrical properties are dominated by electron traps of the respective transition metal atoms, and/or or network defects associated with the alloy. DA - 2002/11// PY - 2002/11// DO - 10.1016/S0038-1101(02)00152-1 VL - 46 IS - 11 SP - 1799-1805 SN - 1879-2405 ER - TY - JOUR TI - Effect of methyl methacrylate/polyhedral oligomeric silsesquioxane random copolymers in compatibilization of polystyrene and poly(methyl methacrylate) blends AU - Zhang, WH AU - Fu, BX AU - Seo, Y AU - Schrag, E AU - Hsiao, B AU - Mather, PT AU - Yang, NL AU - Xu, DY AU - Ade, H AU - Rafailovich, M AU - Sokolov, J T2 - MACROMOLECULES AB - Random copolymers of methyl methacrylate with polyhedral oligomeric silsesquioxane (POSS) were synthesized and blended with PS and PMMA homopolymer thin films. The effects of the POSS on phase segregation were studied using a variety of complementary techniques. The results showed that these copolymers were efficient at compatibilizing immiscible polymer blends. Compatibilization occurred when the POSS was grafted onto the backbone and a favorable interaction existed between the POSS functional groups and the PS homopolymers. The consequences of this compatibilization were studied using a comprehensive array of characterization methods and found to be as follows: reduced domain size, increased interfacial width, and greatly improved fracture toughness. This compatibilization is due to the increased site functionality provided by the POSS molecule without the entropic penalty associated with introducing functionalities via grafting directly onto the polymer chains. DA - 2002/10/8/ PY - 2002/10/8/ DO - 10.1021/ma020725i VL - 35 IS - 21 SP - 8029-8038 SN - 0024-9297 ER - TY - JOUR TI - Dynamics of the tip-sample interaction in near-field scanning optical microscopy and the implications for shear force as an accurate distance measure AU - Jahncke, CL AU - Huerth, SH AU - Clark, B AU - Hallen, HD T2 - APPLIED PHYSICS LETTERS AB - Near-field scanning optical microscopy uses shear-force feedback as the primary method to control the probe–sample distance. We describe the nonlinear interaction between the tip and sample with a simple truncated driven harmonic oscillator model. The model accurately describes the measured dynamics of this system. Insights are gained into the mechanism behind this interaction, and we give strong evidence that the probe taps on sample surface adlayers in normal operation, but will tap the underlying sample surface when the oscillation is nearly quenched. DA - 2002/11/18/ PY - 2002/11/18/ DO - 10.1063/1.1520711 VL - 81 IS - 21 SP - 4055-4057 SN - 1077-3118 UR - http://dx.doi.org/10.1063/1.1520711 N1 - Also appeared in the Virtual Journal of Nanoscience and Technology 6 (22), (2002). RN - Also appeared in the Virtual Journal of Nanoscience and Technology 6 (22), (2002). ER - TY - JOUR TI - Diffraction enhanced imaging contrast mechanisms in breast cancer specimens AU - Hasnah, MO AU - Zhong, Z AU - Oltulu, O AU - Pisano, E AU - Johnston, RE AU - Sayers, D AU - Thomlinson, W AU - Chapman, D T2 - MEDICAL PHYSICS AB - We have investigated the contrast mechanisms of the refraction angle, and the apparent absorption images obtained from the diffraction enhanced imaging technique (DEI) and have correlated them with the absorption contrast of conventional radiography. The contrast of both the DEI refraction angle image and the radiograph have the same dependence on density differences of the tissues in the visualization of cancer; in radiography these differences directly relate to the contrast while in the DEI refraction angle image it is the density difference and thickness gradient that gives the refraction angle. We show that the density difference of fibrils in breast cancer as measured by absorption images correlate well with the density difference derived from refraction angle images of DEI. In addition we find that the DEI apparent absorption image and the image obtained with the DEI system at the top of the reflectivity curve have much greater contrast than that of the normal radiograph (x8 to 33-fold higher). This is due to the rejection of small angle scattering (extinction) from the fibrils enhancing the contrast. DA - 2002/10// PY - 2002/10// DO - 10.1118/1.1507782 VL - 29 IS - 10 SP - 2216-2221 SN - 0094-2405 KW - radiography KW - diffraction enhanced imaging KW - breast cancer KW - x-ray KW - contrast mechanisms ER - TY - JOUR TI - Characterization of the effects of soft X-ray irradiation on polymers AU - Coffey, T AU - Urquhart, SG AU - Ade, H T2 - JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA AB - The physical and chemical effects of the soft X-ray irradiation of polymers have been systematically evaluated for photon energies just above the C 1s binding energy. This exposure causes radiation damage in the form of the loss of mass and changes to the chemical structure of the polymers. These effects are evident in the Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra of the exposed polymers, posing a fundamental limit to the sensitivity of NEXAFS spectroscopy for chemical microanalysis. Quantitative understanding of the chemistry and kinetics of radiation damage in polymers is necessary for the successful and validated application of NEXAFS microscopy. This paper outlines a method for quantifying this radiation damage as a function of X-ray dose, and applies these methods to characterize the loss of mass and loss of carbonyl group functionality from a diverse series of polymers. A series of simple correlations are proposed to rationalize the observed radiation damage propensities on the basis of the polymer chemical structure. In addition, NEXAFS spectra of irradiated and virgin polymers are used to provide a first-order identification of the radiation chemistry. DA - 2002/1// PY - 2002/1// DO - 10.1016/S0368-2048(01)00342-5 VL - 122 IS - 1 SP - 65-78 SN - 1873-2526 KW - NEXAFS spectroscopy KW - polymers KW - damage KW - quantitative KW - analysis KW - radiation chemistry ER - TY - JOUR TI - Auger width and branching ratios for berylliumlike 1s2s(2)np P-1(0) and 1s2p(3 1)P(0) resonances and photoionization of beryllium from 1s(2)2s2 S-1 AU - Lin, H AU - Hsue, CS AU - Chung, KT T2 - PHYSICAL REVIEW A AB - The photoionization cross section (PICS) of Be from the ground state is studied with the saddle-point complex-rotation method for photon energies from 25 to 122 eV. A full-core plus correlation wave function is used for the ground state. For the resonances in the continuum, the energy and width for the singly core-excited Be-like ${1s2s}^{2}2p{}^{1}{P}^{o},$ ${1s2p}^{3}{}^{1}{P}^{o},$ and ${1s2s}^{2}3p{}^{1}{P}^{o}$ are calculated to high precision. The PICS are studied with a single open-channel approximation as well as fully coupled open channels. The Auger decay branching ratios of these states are studied to check the spin-alignment theory recently proposed by Chung. These results are compared with the existing theoretical and experimental data in the literature. For beryllium, our energy and width of ${1s2s}^{2}2p$ are 115.513 eV and 36.6 meV and those of ${1s2s}^{2}3p$ are 121.420 eV and 50.4 meV, which agree with the experiment of Caldwell et al., [Phys. Rev. A 51, 542 (1990)]. DA - 2002/3// PY - 2002/3// DO - 10.1103/physreva.65.032706 VL - 65 IS - 3 SP - SN - 1094-1622 ER - TY - JOUR TI - A molecular orbital model for the electronic structure of transition metal atoms in silicate and aluminate alloys AU - Lucovsky, G AU - Whitten, JL AU - Zhang, Y T2 - SOLID-STATE ELECTRONICS AB - A classification scheme that separates non-crystalline dielectrics into three groups with different amorphous morphologies reveals an approximately linear relationship between oxygen atom coordination and average bond ionicity. When applied to transition metal (TM) and rare earth (RE) lanthanide oxides, and their silicate and aluminate alloys, this approach demonstrates a correlation between stability against crystallization and oxygen atom coordination. It also provides a local bonding model for local molecular orbital calculations that are based on the coordination and symmetry of TM and RE atoms and the orbital energies of their oxygen neighbors. These calculations provide important insights into the electronic structure of TM and RE dielectrics, and in particular the role of atomic d-state energies in providing a scaling parameter for conduction band offset energies between gate dielectrics and the Si substrate. DA - 2002/11// PY - 2002/11// DO - 10.1016/S0038-1101(02)00160-0 VL - 46 IS - 11 SP - 1687-1697 SN - 1879-2405 KW - transition metal oxides KW - silicates and aluminates KW - high-k dielectrics KW - electronic structure KW - local molecular orbital model ER - TY - JOUR TI - X-ray and Raman analyses of GaN produced by ultrahigh-rate magnetron sputter epitaxy AU - Park, M AU - Maria, JP AU - Cuomo, JJ AU - Chang, YC AU - Muth, JF AU - Kolbas, RM AU - Nemanich, RJ AU - Carlson, E AU - Bumgarner, J T2 - APPLIED PHYSICS LETTERS AB - Thick films of GaN were studied by x-ray diffraction and Raman spectroscopy. The GaN thick films were deposited on (0001) sapphire using ultrahigh-rate magnetron sputter epitaxy with typical growth rates as high as 10–60 μm/min. The width of the x-ray rocking curve from the (0002) reflection for the sample produced by this technique is ∼300 arcsec, which is unprecedented for GaN produced by a sputtering-type process. Our recent sample shows an x-ray rocking curve width of 240 arcsec. Only allowed modes were observed in the polarized Raman spectra. The background free carrier concentration is lower than 3×1016 cm−3. The phonon lifetime of the Raman E2(2) mode of the sputtered GaN was comparable to that of bulk single crystal GaN grown by sublimation. The quality of the film was uniform across the wafer. The film was thermally stable upon annealing in N2 ambient. The x-ray and Raman analyses revealed that the sputtered GaN films are of high crystalline quality. DA - 2002/9/2/ PY - 2002/9/2/ DO - 10.1063/1.1506781 VL - 81 IS - 10 SP - 1797-1799 SN - 0003-6951 ER - TY - JOUR TI - Surface science and the atomic-scale origins of friction: what once was old is new again AU - Krim, J T2 - SURFACE SCIENCE AB - Long neglected by physicists, the study of friction's atomic-level origins, or nanotribology, indicates that sliding friction stems from various unexpected sources, including sound energy, and static friction may arise from physisorbed molecules. Progress in this field will be discussed, with an emphasis on how the field of surface science has influenced our understanding of friction. DA - 2002/3/10/ PY - 2002/3/10/ DO - 10.1016/S0039-6028(01)01529-1 VL - 500 IS - 1-3 SP - 741-758 SN - 1879-2758 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0037051006&partnerID=MN8TOARS KW - friction KW - physical adsorption KW - phonons KW - energy dissipation ER - TY - JOUR TI - Simplified bond-hyperpolarizability model of second harmonic generation: Application to Si-dielectric interfaces AU - Wang, JFT AU - Powell, GD AU - Johnson, RS AU - Lucovsky, G AU - Aspnes, DE T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - We show that the anisotropies of second-harmonic-generation (SHG) intensities of singular and vicinal (111) and (001)Si–dielectric interfaces can be described accurately as dipole radiation originating from the anharmonic motion of bond charges parallel to the bond directions. This simplified bond-hyperpolarizability model not only provides a simpler and mathematically more efficient representation of SHG, but also allows a direct physical interpretation at the bond level, which was lacking in previous approaches. Application to oxidized and nitrided Si–SiO2 interfaces provides new insight into bonding that occurs at these interfaces as well as the origin of SHG. DA - 2002/// PY - 2002/// DO - 10.1116/1.1493783 VL - 20 IS - 4 SP - 1699-1705 SN - 2166-2746 ER - TY - JOUR TI - Pion form factor and quark mass evolution in a light-front quark model AU - Choi, HM AU - Kisslinger, LS AU - Ji, CR T2 - NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS AB - We discuss the soft contribution to the elastic pion form factor with the mass evolution from current to constituent quark being taken into account in a light-front quark model(LFQM). DA - 2002/4// PY - 2002/4// DO - 10.1016/S0920-5632(02)01351-8 VL - 108 IS - 2002 Apr SP - 310-312 SN - 1873-3832 ER - TY - JOUR TI - Observation of a magic discrete family of ultrabright Si nanoparticles AU - Belomoin, G AU - Therrien, J AU - Smith, A AU - Rao, S AU - Twesten, R AU - Chaieb, S AU - Nayfeh, MH AU - Wagner, L AU - Mitas, L T2 - APPLIED PHYSICS LETTERS AB - We demonstrate that electrochemically etched, hydrogen capped SinHx clusters with n larger than 20 are obtained within a family of discrete sizes. These sizes are 1.0 (Si29), 1.67 (Si123), 2.15, 2.9, and 3.7 nm in diameter. We characterize the particles via direct electron imaging, excitation and emission optical spectroscopy, and colloidal crystallization. The band gaps and emission bands are measured. The smallest four are ultrabright blue, green, yellow and red luminescent particles. The availability of discrete sizes and distinct emission in the red, green and blue (RGB) range is useful for biomedical tagging, RGB displays, and flash memories. DA - 2002/2/4/ PY - 2002/2/4/ DO - 10.1063/1.1435802 VL - 80 IS - 5 SP - 841-843 SN - 0003-6951 ER - TY - JOUR TI - Nanoscale observation of photoinduced domain pinning and investigation of imprint behavior in ferroelectric thin films AU - Gruverman, A AU - Rodriguez, BJ AU - Nemanich, RJ AU - Kingon, AI T2 - JOURNAL OF APPLIED PHYSICS AB - Piezoresponse force microscopy has been used to investigate the nanoscale mechanism of imprint behavior of ferroelectric PbTiO3 thin films by studying the photoinduced changes in the hysteresis loops of individual grains. Illumination of the film with UV light resulted in a voltage shift opposite to that observed in ferroelectric thin film capacitors. This effect is attributed to the generation of an electric field within the surface dielectric layer as a result of the interaction between photoinduced charges and polarization charges. Application of a small nonswitching bias to the film with simultaneous UV illumination resulted in domain pinning in the grains where the polarization direction coincided with the direction of the applied field, in agreement with the proposed model. Domain pinning was also observed in grains with polydomain structure suggesting that charge entrapment at the existing domain boundaries in the bulk of the film contributes to the suppression of switchable polarization. However, a symmetric character of hysteresis loops observed in such grains implies that charge entrapment in the bulk of the film does not cause the voltage shift. It has been suggested that a thin high-dielectric interfacial layer can improve the imprint behavior of ferroelectric capacitors. DA - 2002/9/1/ PY - 2002/9/1/ DO - 10.1063/1.1497698 VL - 92 IS - 5 SP - 2734-2739 SN - 1089-7550 ER - TY - JOUR TI - Local structure of dilute gallium ions in LiNi0.908Co0.085Ga0.003O2 cathode material - In situ X-ray absorption study AU - Balasubramanian, M AU - McBreen, J AU - Pandya, K AU - Amine, K T2 - JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB - We have utilized "in situ" X-ray absorption spectroscopy (XAS) to study the local atomic structure of dilute Ga dopants in cathode material. We find that in the as-prepared material ions occupy Ni-type sites in the host lattice, as expected. On delithiation (charging), Ga migrates from octahedral Ni-type sites to interstitial tetrahedral sites. The high site preference of ions for tetrahedral sites leads to the stabilization of the Ga ions in these sites. We speculate that this migration of the ions suppresses the transfer of Ni to Li-type sites and also helps to maintain a single hexagonal phase by acting as pillaring ions during high states of charge. We suggest that the high stability of Ga in tetrahedral sites is at the origin of the significant improvement of the cycling and structural properties of Ga-doped cathode materials reported earlier by others. © 2002 The Electrochemical Society. All rights reserved. DA - 2002/9// PY - 2002/9// DO - 10.1149/1.1501096 VL - 149 IS - 9 SP - A1246-A1249 SN - 0013-4651 ER - TY - JOUR TI - Light-front QCD Hamiltonian dynamics and constituent quark picture in exclusive processes AU - Ji, CR AU - Choi, HM T2 - NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS AB - After reviewing a connection between quantum chromodynamics and contituent quark model pictures in the light-front quantization with some comparison and contrast to the ordinary equal-time bridge a la Bogoliubov-Valatin transformation, we discuss some newer development of the light-front quark model phenomenology in exclusive processes including the embedded state. The skewed parton distribution appears to be a good testing ground for our new effective treatment of the light-front nonvalence contributions in timelike exclusive processes. DA - 2002/4// PY - 2002/4// DO - 10.1016/S0920-5632(02)01346-4 VL - 108 IS - 2002 Apr SP - 288-292 SN - 1873-3832 ER - TY - JOUR TI - Interface electronic structure of Ta2O5-Al2O3 alloys for Si- field-effect transistor gate dielectric applications AU - Ulrich, M. D. AU - Johnson, R. S. AU - Hong, J. G. AU - Rowe, J. E. AU - Lucovsky, G. AU - Quinton, J. S. AU - Madey, T. E. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 2002/// PY - 2002/// VL - 20 IS - 4 SP - 1732-1738 ER - TY - JOUR TI - Ground-state reconstruction of the Si(001) surface: symmetric versus buckled dimers AU - Bokes, P AU - Stich, I AU - Mitas, L T2 - CHEMICAL PHYSICS LETTERS AB - An extensive computational study is presented with the quest to investigate the nature of the ground-state geometry of the Si(0 0 1) surface, a subject of recent experimental controversy. We analyze for the first time in detail the possible sources of errors which would arise in any correlated calculation for a system size of interest here. For this purpose, we present a detailed analysis of the cluster model of the surface at the DFT and MCSCF level of theory. Estimates of errors arising from the use of pseudopotential, finite cluster size, and biased (method dependent) choice of ground-state geometry are given. The resulting error is estimated to be comparable to the energy scale of interest. On the other hand, the energy variation due to negative thermal expansion at low temperature is found to be qualitatively consistent with dimer symmetrization. DA - 2002/8/26/ PY - 2002/8/26/ DO - 10.1016/S0009-2614(02)01081-3 VL - 362 IS - 5-6 SP - 559-566 SN - 1873-4448 ER - TY - JOUR TI - Fundamental device design considerations in the development of disruptive nanoelectronics AU - Singh, R AU - Poole, JO AU - Poole, KF AU - Vaidya, SD T2 - JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY AB - In the last quarter of a century silicon-based integrated circuits (ICs) have played a major role in the growth of the economy throughout the world. A number of new technologies, such as quantum computing, molecular computing, DNA molecules for computing, etc., are currently being explored to create a product to replace semiconductor transistor technology. We have examined all of the currently explored options and found that none of these options are suitable as silicon IC's replacements. In this paper we provide fundamental device criteria that must be satisfied for the successful operation of a manufacturable, not yet invented, device. The two fundamental limits are the removal of heat and reliability. The switching speed of any practical man-made computing device will be in the range of 10(-15) to 10(-3) s. Heisenberg's uncertainty principle and the computer architecture set the heat generation limit. The thermal conductivity of the materials used in the fabrication of a nanodimensional device sets the heat removal limit. In current electronic products, redundancy plays a significant part in improving the reliability of parts with macroscopic defects. In the future, microscopic and even nanoscopic defects will play a critical role in the reliability of disruptive nanoelectronics. The lattice vibrations will set the intrinsic reliability of future computing systems. The two critical limits discussed in this paper provide criteria for the selection of materials used in the fabrication of future devices. Our work shows that diamond contains the clue to providing computing devices that will surpass the performance of silicon-based nanoelectronics. DA - 2002/// PY - 2002/// DO - 10.1166/jnn.2002.117 VL - 2 IS - 3-4 SP - 363-368 SN - 1533-4899 KW - disruptive nanoelectronics KW - nanodevices KW - diamond KW - molecular computing KW - quantum computers ER - TY - JOUR TI - Electronic structure of high-k transition metal oxides and their silicate and aluminate alloys AU - Lucovsky, G. AU - Zhang, Y. AU - Rayner, G. B. AU - Appel, G. AU - Ade, H. AU - Whitten, J. L. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 2002/// PY - 2002/// VL - 20 IS - 4 SP - 1739-1747 ER - TY - JOUR TI - Electronic structure of SiO2: Charge redistribution contributions to the dynamic dipoles/effective charges of the infrared active normal modes AU - Whitten, J. L. AU - Zhang, Y. AU - Menon, M. AU - Lucovsky, G. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 2002/// PY - 2002/// VL - 20 IS - 4 SP - 1710-1719 ER - TY - JOUR TI - Electrical, structural and microstructural characteristics of as-deposited and annealed Pt and Au contacts on chemical-vapor-cleaned GaN thin films AU - Preble, EA AU - Tracy, KM AU - Kiesel, S AU - McLean, H AU - Miraglia, PQ AU - Nemanich, RJ AU - Davis, RF AU - Albrecht, M AU - Smith, DJ T2 - JOURNAL OF APPLIED PHYSICS AB - Schottky contacts of Pt(111) and Au(111) were deposited on chemical-vapor-cleaned, n-type GaN(0001) thin films. The growth mode of the deposition, as determined by x-ray photoelectron spectroscopy analysis, followed the two-dimensional Frank–van der Merwe growth model. The resulting as-deposited metal films were monocrystalline and epitaxial with a (111)//(0002) relationship with the GaN. Selected samples were annealed for three minutes at 400 °C, 600 °C or 800 °C. The rectifying behavior of both contacts degraded at 400 °C; they became ohmic after annealing at 600 °C (Au) or 800 °C (Pt). High-resolution transmission electron micrographs revealed reactions at the metal/GaN interfaces for the higher temperature samples. X-ray diffraction results revealed an unidentified phase in the Pt sample annealed at 800 °C. A decrease in the room temperature in-plane (111) lattice constant for both metals, ranging from −0.1% to −0.5%, was observed as the annealing temperature was increased from 400 to 800 °C. This plastic deformation was caused by tensile stresses along the [111] direction that exceeded the yield strength as a result of the large differences in the coefficients of thermal expansion between the metal contacts and the GaN film. DA - 2002/2/15/ PY - 2002/2/15/ DO - 10.1063/1.1432127 VL - 91 IS - 4 SP - 2133-2137 SN - 0021-8979 ER - TY - JOUR TI - Efficient cosmic-ray production in supernova remnant G347.3-0.5 AU - Ellison, DC T2 - NEW ASTRONOMY REVIEWS AB - Broad-band models of the bright NW limb of G347.3–0.5 give convincing evidence that the forward shock of this supernova remnant is accelerating cosmic rays efficiently, placing >25% of the shock kinetic energy flux into relativistic ions. Despite this high efficiency, the maximum electron and proton energies are well below the observed ‘knee’ at ∼1015 eV in the Galactic cosmic-ray spectrum. DA - 2002/7// PY - 2002/7// DO - 10.1016/S1387-6473(02)00191-4 VL - 46 IS - 8-10 SP - 503-506 SN - 1387-6473 KW - supernova remnants KW - cosmic rays ER - TY - JOUR TI - Direct measurement of the neutron-neutron scattering cross section at the reactor YAGUAR AU - Furman, WI AU - Lychagin, EV AU - Muzichka, AY AU - Nekhaev, GV AU - Safronov, YV AU - Strelkov, AV AU - Sharapov, EI AU - Shvetsov, VN AU - Levakov, BG AU - Litvin, , VI AU - Lyzhin, AE AU - Magda, EP AU - Howell, CR AU - Mitchell, GE AU - Tornow, W AU - Crawford, BE AU - Stephenson, SL AU - Bowman, CD T2 - JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS AB - We propose to perform the first measurement of the neutron–neutron scattering cross section in the through-channel of the pulsed aperiodic reactor YAGUAR (Snezhinsk, Russia). Such a measurement directly determines the neutron–neutron scattering length, and by comparison with the proton–proton scattering length bears upon the issue of charge symmetry of the nuclear force. The proposed experimental set-up, as well as modelling of the neutron density and of the frequency of neutron–neutron collisions is described. Experimental results are reported on the formation and optimization of the thermal neutron field inside the through-channel of the reactor YAGUAR. The instantaneous value of 1.1 × 1018 cm−2 s−1 obtained for the thermal neutron flux density is large enough to perform the first direct neutron–neutron scattering length measurement. DA - 2002/10// PY - 2002/10// DO - 10.1088/0954-3899/28/10/308 VL - 28 IS - 10 SP - 2627-2641 SN - 0954-3899 ER - TY - JOUR TI - Current-voltage and imaging of TiSi2 islands on Si(001) surfaces using conductive-tip atomic force microscopy AU - Oh, J AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - Using conducting tip atomic force microscopy (c-AFM), we have measured the current–voltage (I–V) characteristics of individual submicron islands of TiSi2 on Si(100) surfaces, and we have developed an imaging approach that distinguishes the electrical properties of the islands. The Schottky barrier height (SBH) of the submicron TiSi2 islands was deduced from the I–V measurements. The results indicate that there is a significant variation of SBH among the islands on the same surface. The measurements employ a conventional AFM with a heavily B-doped diamond tip to obtain the current–voltage relations. In contact mode AFM, electrical signals are extracted independently from the topographic image. In addition, we have modified the imaging method to probe the local electrical properties of a surface with regions of different conductivity. Using a lock-in technique both phase and amplitude images were obtained, and the resultant image is essentially a map of the differential surface conductivity. Using this method, TiSi2 islands on a Si(100) surface were imaged. This approach can be readily extended to other materials systems. DA - 2002/9/15/ PY - 2002/9/15/ DO - 10.1063/1.1499545 VL - 92 IS - 6 SP - 3326-3331 SN - 1089-7550 ER - TY - JOUR TI - Crystallization study of model tetrahedral semiconductors AU - Nakhmanson, SM AU - Mousseau, N T2 - JOURNAL OF PHYSICS-CONDENSED MATTER AB - The microscopic mechanisms leading to crystallization are not yet fully understood. This is due, in part, to the lack of atomistic as well as interatomic interaction models for a wide range of materials that can lead to crystallization on a computer-simulation timescale, i.e. < 100 ns. While the nucleation in close-packed systems has been extensively studied, there are almost no numerical results for covalent tetrahedral semiconductors. We present here the simulation results of crystallization from the liquid and amorphous states of a 1000-atom model of silicon, described with a modified Stillinger–Weber potential. With this potential, it is possible to crystallize the model in as little as a few nanoseconds, which opens a door to detailed studies of the nucleation processes in covalent systems. Using topological analysis, we also present a first characterization of the structural fluctuations of the nucleation centres in this system and give a rough estimate for the critical size of these centres. DA - 2002/7/8/ PY - 2002/7/8/ DO - 10.1088/0953-8984/14/26/303 VL - 14 IS - 26 SP - 6627-6638 SN - 0953-8984 ER - TY - JOUR TI - Chemical, electrical, and structural properties of Ni/Au contacts on chemical vapor cleaned p-type GaN AU - Hartlieb, PJ AU - Roskowski, A AU - Davis, RF AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - Chemical vapor cleaned, Mg-doped, p-type GaN(0001) surfaces and Ni/Au contacts deposited on these surfaces have been studied using several characterization techniques. Stoichiometric surfaces without detectable carbon and an 87% reduction in the surface oxygen to 2±1 at. % were achieved. The binding energies of the Ga 3d and N 1s core level photoelectron peaks were reduced by 0.5±0.1 eV following the chemical vapor clean. The band bending at the clean surface was measured to be 0.8±0.1 eV. As-deposited Ni/Au contacts on chemical vapor cleaned surfaces exhibited significantly less rectification in the low voltage region (&lt;2 V) compared to identical contact structures on conventional HCl treated surfaces. The specific contact resistance of these contacts deposited on chemical vapor cleaned surfaces and subsequently annealed at 450 °C for 30 seconds was 3±2 Ω cm2. Improved ohmic behavior and a specific contact resistance of 4±2 Ω cm2 was obtained for contacts deposited on HCl treated surfaces and annealed using the same schedule. The formation of Au:Ga and Au:Ni solid solutions was observed for contacts on HCl treated surfaces following the 450 °C anneal. There were significantly less interfacial reactions for annealed contacts on chemical vapor cleaned surfaces. The values of specific contact resistance, sheet resistance, and transfer length of the annealed contacts deposited on both chemical vapor cleaned and HCl treated surfaces and measured from room temperature to 140 °C did not change during three successive thermal cycles within this range. DA - 2002/6/1/ PY - 2002/6/1/ DO - 10.1063/1.1471578 VL - 91 IS - 11 SP - 9151-9160 SN - 1089-7550 ER - TY - JOUR TI - Charge transport through small silicon clusters AU - Roland, C AU - Meunier, V AU - Larade, B AU - Guo, H T2 - PHYSICAL REVIEW B AB - With a recently developed ab initio nonequilibrium Green's-function formalism, we have investigated the transport behavior of small ${\mathrm{Si}}_{n},$ $n=1--10,$ 13, and 20 nanoclusters between atomistic Al and Au leads. All of the clusters display metallic $I\ensuremath{-}V$ characteristics, with typical conductances ranging between two and three (units of ${G}_{o}{=2e}^{2}/h).$ The transport properties of these cluster junctions may be understood in terms of both the band structure of the electrodes, and the molecular electronic states of the clusters as modified by the lead environment. In addition, the quantum transport properties of Si nanoclusters doped with a Na atom are also analyzed. DA - 2002/7/15/ PY - 2002/7/15/ DO - 10.1103/physrevb.66.035332 VL - 66 IS - 3 SP - SN - 2469-9969 ER - TY - JOUR TI - Analysis of Ti-silicide formation with a thin Ta interlayer on Si (100) AU - Jeon, H. AU - Won, H. AU - Kim, Y. AU - Lee, J. AU - Nemanich, R. J. T2 - Journal of the Korean Physical Society DA - 2002/// PY - 2002/// VL - 40 IS - 5 SP - 903-907 ER - TY - JOUR TI - Nonlinear composition dependence of x-ray photoelectron spectroscopy and Auger electron spectroscopy features in plasma-deposited zirconium silicate alloy thin films AU - Rayner, GB AU - Kang, D AU - Zhang, Y AU - Lucovsky, G T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - The local bonding of Zr, Si, and O atoms in plasma-deposited, and post-deposition annealed Zr silicate pseudobinary alloys [(ZrO2)x(SiO2)1−x] was studied by x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Systematic decreases in XPS binding energies, and increases in AES kinetic energies with alloy composition x are consistent with an empirical chemical bonding model based on electronegativity equalization; however, there are significant departures from the predicted linear composition dependencies of that model. Deviations from linearity in the XPS compositional dependencies are correlated with dipolar network atom fields as determined from ab initio calculations. The nonlinearities in the x dependence of ZrMVV and OKVV AES spectral features are determined primarily by oxygen–atom coordination dependent shifts in valence band offset energies. The energy spread in the compositional dependence of binding energies (∼1.85 eV) for the XPS Zr 3d5/2 and Si 2p features combined with x-ray absorption spectroscopy data indicates that the conduction band offset energies between the Si substrate and Zr silicate dielectrics are alloy composition independent. Changes in O 1s XPS features in alloys with x∼0.3 to 0.6 as function of annealing temperature are consistent with a previously identified chemical phase separation that occurs after 60 s anneals at 900 °C in a nonoxidizing ambient, Ar. DA - 2002/// PY - 2002/// DO - 10.1116/1.1493788 VL - 20 IS - 4 SP - 1748-1758 SN - 2166-2746 ER - TY - JOUR TI - Mechanical and electrical properties of nanotubes AU - Bernholc, J AU - Brenner, D AU - Nardelli, MB AU - Meunier, V AU - Roland, C T2 - ANNUAL REVIEW OF MATERIALS RESEARCH AB - ▪ Abstract We review the recent progress in our understanding of the mechanical and electrical properties of carbon nanotubes, emphasizing the theoretical aspects. Nanotubes are the strongest materials known, but the ultimate limits of their strength have yet to be reached experimentally. Modeling of nanotube-reinforced composites indicates that the addition of small numbers of nanotubes may lead to a dramatic increase in the modulus, with only minimal crosslinking. Deformations in nanotube structures lead to novel structural transformations, some of which have clear electrical signatures that can be utilized in nanoscale sensors and devices. Chemical reactivity of nanotube walls is facilitated by strain, which can be used in processing and functionalization. Scanning tunneling microscopy and spectroscopy have provided a wealth of information about the structure and electronic properties of nanotubes, especially when coupled with appropriate theoretical models. Nanotubes are exceptional ballistic conductors, which can be used in a variety of nanodevices that can operate at room temperature. The quantum transport through nanotube structures is reviewed at some depth, and the critical roles played by band structure, one-dimensional confinement, and coupling to nanoscale contacts are emphasized. Because disorder or point defect–induced scattering is effectively averaged over the circumference of the nanotube, electrons can propagate ballistically over hundreds of nanometers. However, severe deformations or highly resistive contacts isolate nanotube segments and lead to the formation of quantum dots, which exhibit Coulomb blockade effects, even at room temperature. Metal-nanotube and nanotube-nanotube contacts range from highly transmissive to very resistive, depending on the symmetry of two structures, the charge transfer, and the detailed rehybridization of the wave functions. The progress in terms of nanotube applications has been extraordinarily rapid, as evidenced by the development of several nanotube-based prototypical devices, including memory and logic circuits, chemical sensors, electron emitters and electromechanical actuators. DA - 2002/// PY - 2002/// DO - 10.1146/annurev.matsci.32.112601.134925 VL - 32 IS - 2002 SP - 347-+ SN - 1531-7331 KW - composites KW - deformation KW - STM images KW - STS spectra ER - TY - JOUR TI - Photoelectron spectroscopy studies of growth, thermal stability, and alloying for transition metal-tungsten (111) bimetallic systems AU - Kolodziej, J. J. AU - Madey, T. E. AU - Keister, J. W. AU - Rowe, J. E. T2 - Physical Review. B, Condensed Matter and Materials Physics DA - 2002/// PY - 2002/// VL - 65 IS - 7 SP - 075413-1 ER - TY - JOUR TI - Fixed charge and interface traps at heterovalent interfaces between Si(100) and non-crystalline Al2O3-Ta2O5 alloys AU - Johnson, RS AU - Lucovsky, G AU - Hong, JG T2 - APPLIED SURFACE SCIENCE AB - Characterization by Auger electron spectroscopy (AES) and Fourier transformation infrared spectroscopy (FTIR) confirms (Ta2O5)x(Al2O3)1−x alloys are homogeneous pseudo-binary alloys with increased thermal stability with respect to end member oxides, Ta2O5 and Al2O3. Capacitance–voltage (C–V) and current density–voltage (J–V) data as a function of temperate show that the Ta d-states of the alloys act as localized electron traps, and are at an energy approximately equal to the conduction band offset of Ta2O5 with respect to Si. DA - 2002/5/8/ PY - 2002/5/8/ DO - 10.1016/S0169-4332(01)00889-3 VL - 190 IS - 1-4 SP - 43-47 SN - 1873-5584 KW - heterovalent interface KW - interface traps KW - fixed charge KW - trapped limited transport KW - Poole-Frenkel transport ER - TY - JOUR TI - Electronic and field emission properties of boron nitride/carbon nanotube superlattices AU - Meunier, V AU - Roland, C AU - Bernholc, J AU - Nardelli, MB T2 - APPLIED PHYSICS LETTERS AB - BN/C nanotube superlattices are quasi one-dimensional heterostructures that show unique physical properties derived from their peculiar geometry. Using state-of-the-art ab initio calculations, we show that BN/C systems can be used for effective band-offset nanodevice engineering, polarization-based devices, and robust field emitters with an efficiency enhanced by up to two orders of magnitude over carbon nanotube systems. DA - 2002/7/1/ PY - 2002/7/1/ DO - 10.1063/1.1491013 VL - 81 IS - 1 SP - 46-48 SN - 1077-3118 ER - TY - JOUR TI - Effect of contact resistance in solid-state thermionic refrigeration AU - Ulrich, MD AU - Barnes, PA AU - Vining, CB T2 - JOURNAL OF APPLIED PHYSICS AB - An analytical model of thermionic emission cooling that includes contact resistance is presented. The electrical current density necessary for peak operation of thermionic emission coolers is such that even the slightest resistance in the contacts to the devices will significantly reduce the cooling and coefficient of the performance. The effect of contact resistance is analyzed numerically using a model of thermionic emission cooling based on Fermi–Dirac statistics. The cooling and coefficient of performance are shown to be reduced dramatically by even the slightest contact resistance. DA - 2002/7/1/ PY - 2002/7/1/ DO - 10.1063/1.1481777 VL - 92 IS - 1 SP - 245-247 SN - 1089-7550 ER - TY - JOUR TI - TiC nanoisland formation on 6H-SiC(0001)(Si) AU - Platow, W AU - Oh, J AU - Nemanich, RJ AU - Sayers, DE AU - Hartman, JD AU - Davis, RF T2 - JOURNAL OF APPLIED PHYSICS AB - Spontaneous formation of titanium carbide nanoislands on silicon carbide substrates has been studied with scanning tunneling microscopy and x-ray absorption near-edge spectroscopy. Scratch-free and atomically flat 6H–SiC(0001)Si substrates were prepared by high temperature hydrogen etching. The surfaces were subsequently cleaned by in situ ultrahigh vacuum annealing. Titanium carbide nanoislands were formed by titanium deposition and annealing at 950 °C. The average width (10–50 nm) and separation of the Ti islands was controlled by varying the titanium coverage (0.1–0.3 nm) and the annealing time (1–20 min). At the lowest coverage, the islands were uniformly distributed over the surface, while at higher coverage the islands tended to collect at the substrate step edges. DA - 2002/5/1/ PY - 2002/5/1/ DO - 10.1063/1.1465121 VL - 91 IS - 9 SP - 6081-6084 SN - 0021-8979 ER - TY - JOUR TI - The angular expansion and distance of the planetary nebula BD+30 degrees 3639 AU - Li, JY AU - Harrington, JP AU - Borkowski, KJ T2 - ASTRONOMICAL JOURNAL AB - The WFPC2 camera aboard the Hubble Space Telescope was used to obtain images of the planetary nebula BD +30°3639 at two epochs separated by 5.663 yr. The expansion of the nebula in the Hα and [N II] bands has been measured using several methods. Detailed expansion maps for both emission lines were constructed from nearly 200 almost independent features. There is good agreement between the (independent) Hα and [N II] proper motions. There are clear deviations from uniform radial expansion, with higher expansion rates in regions where the shell is faintest, such as the southwest quadrant. The Space Telescope Imaging Spectrograph was used to obtain echelle spectra in the C II] λ2326 multiplet and the [O II] λ2470 doublet, providing well-resolved expansion velocities at two position angles. From the C II] lines we find that the central velocity split is ±36.3 km s-1 at a position angle (P.A.) of 99° and ±33.5 km s-1 at P.A. 25°. The fainter [O II] doublet does not appear to differ from the C II] multiplet. To determine the distance of BD +30°3639 by comparison of the angular expansion and the spectroscopically determined radial expansion, we must address the problem of the three-dimensional shape of the nebula. We measured the angular expansion along the position of the 99° echelle slit, finding displacements of 4.25 mas yr-1 at the shell edge (247 from the center). If the nebula were spherical, this would imply a distance of 1.80 kpc. But there is evidence that the nebula is elongated along the line of sight, which suggests that the actual distance is less. Radio continuum images from 5 and 15 GHz VLA observations provide information on the extent of the radial elongation. We fit the radio brightness variation and the echelle data by approximating the nebula as an ellipsoid, also making use of the ground-based echelle spectra reported by Bryce & Mellema. Our model has an axial ratio of 1.56, is inclined to the line of sight by 97, and exhibits an expansion in the plane of the sky which is that in the radial direction, leading to a distance of 1.2 kpc. Not all the kinematic data fit this simple model, so the distance must still be regarded as uncertain. Based on the recent model atmosphere of Crowther et al., a distance of 1.2 kpc implies a stellar luminosity of 4250 L⊙. The kinematic age of the nebula, θ/, varies somewhat from region to region. A good average value is 800 yr, while the expansion along the position of the 99° echelle slit gives about 600 yr. DA - 2002/5// PY - 2002/5// DO - 10.1086/340078 VL - 123 IS - 5 SP - 2676-2688 SN - 1538-3881 KW - planetary nebulae : individual (BD+30 degrees 3639) KW - stars : distances ER - TY - JOUR TI - Simplified bond-hyperpolarizability model of second harmonic generation AU - Powell, GD AU - Wang, JF AU - Aspnes, DE T2 - PHYSICAL REVIEW B AB - We show that the anisotropies of second-harmonic-generation (SHG) intensities of vicinal (111) and $(001){\mathrm{S}\mathrm{i}\ensuremath{-}\mathrm{S}\mathrm{i}\mathrm{O}}_{2}$ interfaces can be described accurately as dipole radiation originating from the anharmonic motion of bond charges strictly along bond directions. This simplified bond-hyperpolarizability model not only substantially simplifies the description of SHG, but also provides a microscopically physical and mathematically more efficient picture of the process than those found in standard phenomenological treatments employing tensor or Fourier coefficients. Using this approach we obtain an analytic solution for the expected response of (111) terraces, and by comparing to data show that the effective angles of incidence and observation for the $(111){\mathrm{S}\mathrm{i}\ensuremath{-}\mathrm{S}\mathrm{i}\mathrm{O}}_{2}$ interface are not those measured in the laboratory but correspond to those refracted at the air-${\mathrm{SiO}}_{2}$ interface. For (111) vicinal interfaces at 765 nm SHG absorption is found to occur mainly for the step bond. The success of this formulation indicates that in many, if not most, cases the description of SHG may be simpler than that of the linear-optical response. DA - 2002/5/15/ PY - 2002/5/15/ DO - 10.1103/physrevb.65.205320 VL - 65 IS - 20 SP - SN - 2469-9969 ER - TY - JOUR TI - GaAs(001) surface reconstructions: geometries, chemical bonding and optical properties AU - Schmidt, WG AU - Bechstedt, F AU - Bernholc, J T2 - APPLIED SURFACE SCIENCE AB - We re-examine the GaAs(0 0 1) surface by means of first-principles calculations based on a real-space multigrid method. The c(4×4),(2×4)and(4×2) surface reconstructions minimize the surface energy for anion-rich, stoichiometric and cation-rich surfaces, respectively. Structural models proposed in the literature to explain the Ga-rich GaAs(0 0 1) (4×6) surface are dismissed on energetic grounds. The electronic properties of the novel ζ(4×2) structure are discussed in detail. We calculate the reflectance anisotropy of the energetically most favoured surfaces. A strong influence of the surface geometry on the optical anisotropy is found. DA - 2002/5/8/ PY - 2002/5/8/ DO - 10.1016/S0169-4332(01)00862-5 VL - 190 IS - 1-4 SP - 264-268 SN - 0169-4332 KW - gallium arsenide KW - (001) surfaces KW - reflection spectroscopy KW - density functional calculations KW - excitation spectra calculations ER - TY - JOUR TI - Enhanced low-temperature thermionic field emission from surface-treated N-doped diamond films AU - Kock, FAM AU - Garguilo, JM AU - Brown, B AU - Nemanich, RJ T2 - DIAMOND AND RELATED MATERIALS AB - Nitrogen-doped diamond films have been synthesized for application as a low-temperature thermionic field-emission cathode. The critical result of this study is the observation of uniform electron emission from UV photo-excitation and from thermionic field emission for films terminated with hydrogen or a 0.3-nm Ti layer. The samples were imaged with photoelectron emission microscopy (PEEM) and thermionic field-emission electron microscopy (T-FEEM) at temperatures up to 900 °C, and the electron emission current was recorded vs. the applied voltage. Hydrogen-passivated films show enhanced electron emission, but become unstable at elevated temperatures, while Ti-terminated films showed similar enhanced emission at temperatures up to 950 °C. Temperature-dependent I/V measurements show strongly increased electron emission at higher temperatures, suggesting that electron emission originates from the conduction band. These results indicate a promising new material for the production of low-temperature, high-brightness electron sources. DA - 2002/// PY - 2002/// DO - 10.1016/S0925-9635(02)00006-7 VL - 11 IS - 3-6 SP - 774-779 SN - 1879-0062 KW - chemical vapor deposition (CVD) KW - diamond KW - field emission ER - TY - JOUR TI - Electron trapping in noncrystalline remote plasma deposited Hf- aluminate alloys for gate dielectric applications AU - Johnson, R. S. AU - Hong, J. G. AU - Hinkle, C. AU - Lucovsky, G. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 2002/// PY - 2002/// VL - 20 IS - 3 SP - 1126-1131 ER - TY - JOUR TI - Dielectric functions and optical bandgaps of high-K dielectrics for metal-oxide-semiconductor field-effect transistors by far ultraviolet spectroscopic ellipsometry AU - Lim, SG AU - Kriventsov, S AU - Jackson, TN AU - Haeni, JH AU - Schlom, DG AU - Balbashov, AM AU - Uecker, R AU - Reiche, P AU - Freeouf, JL AU - Lucovsky, G T2 - JOURNAL OF APPLIED PHYSICS AB - A far ultraviolet (UV) spectroscopic ellipsometer system working up to 9 eV has been developed, and applied to characterize high-K-dielectric materials. These materials have been gaining greater attention as possible substitutes for SiO2 as gate dielectrics in aggressively scaled silicon devices. The optical properties of four representative high-K bulk crystalline dielectrics, LaAlO3, Y2O3-stabilized HfO2 (Y2O3)0.15–(HfO2)0.85, GdScO3, and SmScO3, were investigated with far UV spectroscopic ellipsometry and visible-near UV optical transmission measurements. Optical dielectric functions and optical band gap energies for these materials are obtained from these studies. The spectroscopic data have been interpreted in terms of a universal electronic structure energy scheme developed form ab initio quantum chemical calculations. The spectroscopic data and results provide information that is needed to select viable alternative dielectric candidate materials with adequate band gaps, and conduction and valence band offset energies for this application, and additionally to provide an optical metrology for gate dielectric films on silicon substrates. DA - 2002/4/1/ PY - 2002/4/1/ DO - 10.1063/1.1456246 VL - 91 IS - 7 SP - 4500-4505 SN - 1089-7550 ER - TY - JOUR TI - A new bend-magnet beamline for scanning transmission X-ray microscopy at the Advanced Light Source AU - Warwick, T AU - Ade, H AU - Kilcoyne, D AU - Kritscher, M AU - Tylisczcak, T AU - Fakra, S AU - Hitchcock, A AU - Hitchcock, P AU - Padmore, H T2 - JOURNAL OF SYNCHROTRON RADIATION AB - The high brightness of the bend magnets at the Advanced Light Source has been exploited to illuminate a scanning transmission X-ray microscope (STXM). This is the first diffraction-limited scanning X-ray microscope to operate with a useful count rate on a synchrotron bend-magnet source. A simple dedicated beamline has been built covering the range of photon energy from 250 eV to 600 eV. The beamline is always available and needs little adjustment. Use of this facility is much easier than that of installations that share undulator beams. This facility provides radiation for C 1s, N 1s and O 1s near-edge X-ray absorption spectromicroscopy with STXM count rates in excess of 1 MHz and with spectral resolution typically 1:2000, limited to about 1:5000. DA - 2002/7// PY - 2002/7// DO - 10.1107/S0909049502005502 VL - 9 IS - 2002 Jul SP - 254-257 SN - 0909-0495 KW - bend magnets KW - diffraction limit KW - zone plates KW - scanning KW - microscopy KW - NEXAFS ER - TY - JOUR TI - A molecular orbital model for the electronic structure of transition metal atoms in silcate and aluminate alloys AU - Lucovsky, G AU - Whitten, JL AU - Zhang, Y T2 - APPLIED SURFACE SCIENCE AB - Applied to transition metal oxides and silicate and aluminate alloys, a classification scheme that separates non-crystalline dielectrics into three groups with different amorphous morphologies, demonstrates a direct correlation between stability against crystallization and oxygen atom coordination. It also provides a local bonding model for molecular orbital (MO), calculations that are based on the coordination and symmetry of transition metal atoms and the orbital energies of their oxygen neighbors. These calculations provide important insights into the electronic structure of transition metal dielectrics, e.g. the role of anti-bonding d-states in determining conduction band offset energies with respect to Si. DA - 2002/5/8/ PY - 2002/5/8/ DO - 10.1016/S0169-4332(01)00835-2 VL - 190 IS - 1-4 SP - 48-55 SN - 1873-5584 KW - morphological classification of non-crystalline dielectrics KW - transition metal silicates and aluminates KW - molecular orbital calculations KW - electronic structure KW - band offset energies ER - TY - JOUR TI - Superhard phase composed of single-wall carbon nanotubes AU - Popov, M AU - Kyotani, M AU - Nemanich, RJ AU - Koga, Y T2 - PHYSICAL REVIEW B AB - Single-wall carbon nanotubes (SWNT's) have been studied under pressure up to 55 GPa. We report experimental data on irreversible changes of mechanical and structure properties of SWNT under pressure. The new superhard phase (SP-SWNT) composed of single-wall carbon nanotubes has been studied which exhibits a bulk modulus exceeding or comparable with diamond and hardness belongs to the range between cubic BN and diamond. The SP-SWNT were synthesized by applying a shear deformation under load in a diamond-anvil cell; the procedure of stress tensor variation. After intermediate phase transitions, single-wall carbon nanotubes are transformed to SP-SWNT at pressure of 24 GPa. The transformation is accompanied by irreversible changes in the Raman spectra. The nanotubes do not collapse at least up to pressure 55 GPa (maximum pressure of the study). Bulk modulus of 462 to 546 GPa was found out for SP-SWNT from the comparative study of pressure dependence of the Raman modes of SP-SWNT (high-energy mode \ensuremath{\sim}1590 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$) and diamond (1333 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$). This value exceeds the bulk modulus of diamond (420 GPa for single diamond crystal). Hardness measurements were performed using nanoindentation technique. Hardness of SP-SWNT (62 to 150 GPa) was found out from comparative study of SP-SWNT, diamond and cubic BN. DA - 2002/1/15/ PY - 2002/1/15/ DO - 10.1103/physrevb.65.033408 VL - 65 IS - 3 SP - SN - 2469-9969 ER - TY - JOUR TI - Sub-Doppler magneto-optical trap for calcium AU - Grunert, J AU - Hemmerich, A T2 - PHYSICAL REVIEW A AB - We have calculated the $I\ensuremath{-}V$ characteristics of short chains of ${\mathrm{C}}_{20}$ molecular cages between $\mathrm{Al}$ and $\mathrm{Au}$ leads with an ab initio formalism. The results indicate that a linear chain of such molecules acts primarily as metallic nanowires. The transmission, however, depends sensitively both on the orientation and distance between the individual ${\mathrm{C}}_{20}$ molecules. Transport through the molecular chains is accompanied by a significant amount of charge transfer, which remains localized at the electrode/molecular interface. DA - 2002/4// PY - 2002/4// DO - 10.1103/physrevb.65.041401 VL - 65 IS - 4 SP - SN - 1094-1622 ER - TY - JOUR TI - Stacking faults and twins in gallium phosphide layers grown on silicon AU - Narayanan, V AU - Mahajan, S AU - Bachmann, KJ AU - Woods, V AU - Dietz, N T2 - PHILOSOPHICAL MAGAZINE A-PHYSICS OF CONDENSED MATTER STRUCTURE DEFECTS AND MECHANICAL PROPERTIES AB - Abstract The coalescence of GaP islands, grown on Si(001), Si(111), Si(110) and Si(113) surfaces by chemical beam epitaxy, has been investigated by high-resolution transmission electron microscopy. Stacking faults and first-order twins are observed within islands before coalescence and result from stacking errors during growth on the smaller P-terminated {111} facets of GaP islands. Upon island coalescence, complex moire fringes are observed contiguous to highly faulted {111} planes within epitaxial layers grown on all four Si substrate orientations and are attributed to multiple twinning. Second-and third-order twins are also observed within (111) and (110) layers and their formation is attributed to successive twinning on differently inclined {111} facets. Amongst the four orientations, coalesced growths on the Si(111) surface are the most defective and this may be caused by a higher density of P-terminated {111} facets on islands grown on the Si(111) surface. DA - 2002/3// PY - 2002/3// DO - 10.1080/01418610110082034 VL - 82 IS - 4 SP - 685-698 SN - 0141-8610 ER - TY - JOUR TI - Quantitative characterization of microscopic variations in the cross-link density of gels AU - Mitchell, GE AU - Wilson, LR AU - Dineen, MT AU - Urquhart, SG AU - Hayes, F AU - Rightor, EG AU - Hitchcock, AP AU - Ade, H T2 - MACROMOLECULES AB - We report the visualization and quantitative analysis of the cross-link structure in model core/shell hydrogel polymers on the microscopic scale, in a fully swollen state, using soft X-ray microscopy. The cross-link density in these materials and their microscopic or even nanoscopic variation critically influence materials characteristics, yet the cross-link density is difficult to characterize by conventional methods. By the use of soft X-ray microscopy, one can investigate these materials in a fully swollen state and thus directly visualize and quantitatively determine the cross-link structure on a microscopic scale. Materials that were cross-linked by different methods were shown to give rise to differently shaped profiles. Abrupt and gradient cross-link density profiles have been investigated, and the spatial variation in their cross-link density has been determined quantitatively. DA - 2002/2/12/ PY - 2002/2/12/ DO - 10.1021/ma010840d VL - 35 IS - 4 SP - 1336-1341 SN - 1520-5835 ER - TY - JOUR TI - Parity violation in neutron resonances of palladium AU - Smith, DA AU - Bowman, JD AU - Crawford, BE AU - Grossmann, CA AU - Haseyama, T AU - Masaike, A AU - Matsuda, Y AU - Mitchell, GW AU - Penttila, SI AU - Roberson, NR AU - Seestrom, SJ AU - Sharapov, EI AU - Stephenson, SL AU - Yuan, VW T2 - PHYSICAL REVIEW C AB - Parity violation in p-wave neutron resonances of the palladium isotopes 104, 105, 106, and 108 has been measured by transmission of a longitudinally polarized neutron beam through a natural palladium target. The measurements were performed at the pulsed spallation neutron source of Los Alamos Neutron Science Center. The rms weak interaction matrix elements and the corresponding spreading widths were determined for ${}^{104}\mathrm{Pd},$ ${}^{105}\mathrm{Pd},$ and ${}^{106}\mathrm{Pd}.$ DA - 2002/3// PY - 2002/3// DO - 10.1103/physrevc.65.035503 VL - 65 IS - 3 SP - SN - 2469-9993 ER - TY - JOUR TI - Light-front quark model analysis of rare B -> Kl(+)l(-) decays AU - Choi, H. M. AU - Ji, C. R. AU - Kisslinger, L. S. T2 - Physical Review. D, Particles and Fields DA - 2002/// PY - 2002/// VL - 65 IS - 7 SP - 074032-1 ER - TY - JOUR TI - Frame dependence of spin-one angular conditions in light front dynamics AU - Bakker, B. L. G. AU - Ji, C. R. T2 - Physical Review. D, Particles and Fields DA - 2002/// PY - 2002/// VL - 65 IS - 7 SP - 073002-1 ER - TY - JOUR TI - Electron-beam-induced optical memory effects in GaN AU - Chang, YC AU - Cai, AL AU - Johnson, MAL AU - Muth, JF AU - Kolbas, RM AU - Reitmeier, ZJ AU - Einfeldt, S AU - Davis, RF T2 - APPLIED PHYSICS LETTERS AB - Metastable effects in unintentionally doped GaN films grown on SiC substrates have been investigated using cathodoluminescence (CL). Memory effect patterns produced optically are observed in CL images. An electron beam can also produce memory effect patterns and the resulting changes in the luminescence spectra are quite similar for either optical or electron-beam-induced patterns. CL spectra reveal that the yellow luminescence at 2.2 eV increases significantly with little change in the band-edge emission in both cases. Samples that do not exhibit optically induced memory effects are also investigated and do not exhibit electron-beam-induced patterns, either. Monochromatic CL images at 540 and 365 nm confirm the similarity of optically and electron-beam-induced memory effects based on changes in luminescence spectra. DA - 2002/4/15/ PY - 2002/4/15/ DO - 10.1063/1.1469222 VL - 80 IS - 15 SP - 2675-2677 SN - 0003-6951 ER - TY - JOUR TI - Electric field outside a parallel plate capacitor AU - Parker, GW T2 - AMERICAN JOURNAL OF PHYSICS AB - The problem of determining the electrostatic potential and field outside a parallel plate capacitor is reduced, using symmetry, to a standard boundary value problem in the half space z⩾0. In the limit that the gap d between plates approaches zero, the potential outside the plates is given as an integral over the surface of one plate. This integral is evaluated for several special cases. The magnitude of the field just outside and near the center of a two-dimensional strip capacitor of width W is shown to agree with finite difference calculations when W/d&gt;4. The shapes of field lines outside a strip capacitor are determined, and circular lines are shown to occur near the edges. The determination of the electric field just outside and near the center of a parallel plate capacitor complements the recently published result for the magnetic field just outside and near the center of a long solenoid [J. A. Farley and R. H. Price, Am. J. Phys. 69, 751–754 (2001)]. DA - 2002/5// PY - 2002/5// DO - 10.1119/1.1463738 VL - 70 IS - 5 SP - 502-507 SN - 0002-9505 ER - TY - JOUR TI - Chirally symmetric quark description of low energy pi-pi scattering AU - Bicudo, P AU - Cotanch, S AU - Llanes-Estrada, F AU - Maris, P AU - Ribeiro, E AU - Szczepaniak, A T2 - PHYSICAL REVIEW D AB - Weinberg's theorem for $\ensuremath{\pi}\ensuremath{-}\ensuremath{\pi}$ scattering, including the Adler zero at threshold in the chiral limit, is analytically proved for microscopic quark models that preserve chiral symmetry. Implementing Ward-Takahashi identities, the isospin $0$ and $2$ scattering lengths are derived in exact agreement with Weinberg's low energy results. Our proof applies to alternative quark formulations including the Hamiltonian and Euclidean space Dyson-Schwinger approaches. Finally, the threshold $\ensuremath{\pi}\ensuremath{-}\ensuremath{\pi}$ scattering amplitudes are calculated using the Dyson-Schwinger equations in the rainbow-ladder truncation, confirming the formal derivation. DA - 2002/4/1/ PY - 2002/4/1/ DO - 10.1103/physrevd.65.076008 VL - 65 IS - 7 SP - SN - 0556-2821 ER - TY - JOUR TI - STM study of a grain boundary in graphite AU - Simonis, P AU - Goffaux, C AU - Thiry, PA AU - Biro, LP AU - Lambin, P AU - Meunier, V T2 - SURFACE SCIENCE AB - A grain boundary in highly oriented pyrolitic graphite has been investigated by scanning tunneling microscopy (STM). Along the boundary, a periodic structure has been observed. Crystallographic models have been constructed in order to explain the bonding between the two grains and STM theoretical simulations have been carried out. They conclude to the probable presence of pentagon–heptagon chains at the boundary. DA - 2002/6/10/ PY - 2002/6/10/ DO - 10.1016/S0039-6028(02)01511-X VL - 511 IS - 1-3 SP - 319-322 SN - 0039-6028 KW - scanning tunneling microscopy KW - surface structure, morphology, roughness, and topography KW - graphite KW - grain boundaries KW - computer simulations ER - TY - JOUR TI - Reliability degradation of ultra-thin oxynitride and Al2O3 gate dielectric films owing to heavy-ion irradiation AU - Choi, B. K. AU - Fleetwood, D. M. AU - Massengill, L. W. AU - Schrimpf, R. D. AU - Galloway, K. F. AU - Shaneyfelt, M. R. AU - Meisenheimer, T. L. AU - Dodd, P. E. AU - Schwank, J. R. AU - Lee, Y. M. AU - Johnson, R. S. AU - Lucovsky, G. T2 - Electronics Letters AB - The charge-to-breakdown of 3.3 nm oxynitride films shows significant degradation after irradiation with 342 MeV Au ions. In contrast, 5.4 nm Al2O3 films exhibit much less degradation for similar heavy-ion stress. DA - 2002/// PY - 2002/// DO - 10.1049/el:20020119 VL - 38 IS - 4 SP - 157-158 ER - TY - JOUR TI - Relativistic many-body Hamiltonian approach to mesons AU - Llanes-Estrada, FJ AU - Cotanch, , SR T2 - NUCLEAR PHYSICS A AB - We represent QCD at the hadronic scale by means of an effective Hamiltonian, H, formulated in the Coulomb gauge. As in the Nambu–Jona-Lasinio model, chiral symmetry is explicitly broken, however our approach is renormalizable and also includes confinement through a linear potential with slope specified by lattice gauge theory. This interaction generates an infrared integrable singularity and we detail the computationally intensive procedure necessary for numerical solution. We focus upon applications for the u,d,s and c quark flavors and compute the mass spectrum for the pseudoscalar, scalar and vector mesons. We also perform a comparative study of alternative many-body techniques for approximately diagonalizing H: BCS for the vacuum ground state; TDA and RPA for the excited hadron states. The Dirac structure of the field theoretical Hamiltonian naturally generates spin-dependent interactions, including tensor, spin–orbit and hyperfine, and we clarify the degree of level splitting due to both spin and chiral symmetry effects. Significantly, we find that roughly two-thirds of the π–ρ mass difference is due to chiral symmetry and that only the RPA preserves chiral symmetry. We also document how hadronic mass scales are generated by chiral symmetry breaking in the model vacuum. In addition to the vacuum condensates, we compute meson decay constants and detail the Nambu–Goldstone realization of chiral symmetry by numerically verifying the Gell-Mann–Oakes–Renner relation. DA - 2002/1/14/ PY - 2002/1/14/ DO - 10.1016/S0375-9474(01)01237-4 VL - 697 IS - 1-2 SP - 303-337 SN - 1873-1554 KW - many-body techniques KW - meson spectrum KW - effective QCD Hamiltonian ER - TY - PCOMM TI - Physics intentions and the GRE AU - Memory, JD AB - In the early 1980s, three coauthors and I published a letter ( Physics Today, Physics Today 0031-9228 37 4 1984 15 https://doi.org/10.1063/1.2916188. April 1984, page 15 ) stating that the Graduate Record Examination (GRE) aptitude tests showed that those students taking the tests and indicating physics as their intended area of study had the highest combined quantitative and verbal scores of the 98 disciplines listed. In view of evolving trends in graduate education, it seemed of interest to reexamine the quality of students planning to go to graduate school in physics, as measured by the GRE aptitude tests.The data given here appear in the GRE Guide to the Use of Scores, available online at ftp://ftp.ets.org/pub/gre/992362.pdf, and are based on exams taken between 1 October 1997 and 30 September 2000. Test takers were grouped into 50 broad fields by intended graduate major, and mean scores are reported for each of the three aptitude tests, verbal, quantitative, and analytical.For the physics and astronomy category, the mean score ranked first in quantitative aptitude, first in analytical, and tied for sixth in verbal (students who listed philosophy as their intended course of study ranked first in verbal aptitude). When the means are aggregated, students intending to study physics and astronomy easily rank first among the 50 categories. Physics graduate programs are still getting good students—so good, in fact, that the aptitude tests are of limited value in predicting first-year grades in graduate school, the one outcome for which complete data are published. The correlation of first-year graduate grades with the aggregate aptitude score is only 0.20. Moreover, the best correlation is with the verbal score, which is a little surprising until one notices that the standard deviation is largest for this test. Overall, the scores are so uniformly high that they provide little discrimination.The situation is somewhat different with the subject matter test: The correlation with first-year graduate grades is 0.27, about the same as for undergraduate grades, where the correlation is 0.28.© 2002 American Institute of Physics. DA - 2002/7// PY - 2002/7// DO - 10.1063/1.1506766 SP - 83-83 ER - TY - JOUR TI - Neutron resonance spectroscopy of Pd-104, Pd-105, and Pd-110 AU - Smith, DA AU - Bowman, JD AU - Crawford, BE AU - Grossmann, CA AU - Haseyama, T AU - Masaike, A AU - Matsuda, Y AU - Mitchell, GE AU - Penttila, SI AU - Roberson, NR AU - Seestrom, SJ AU - Sharapov, EI AU - Stephenson, SL AU - Sukhovoj, AM AU - Yuan, VW T2 - PHYSICAL REVIEW C AB - We have measured neutron resonances in the palladium isotopes 104, 105, and 110 for neutron energies from 1 to 2100 eV. Many new p-wave resonances have been observed. Their neutron widths and, in several cases, the radiative widths were measured. The average level spacings and the s-wave and p-wave neutron strength functions were determined. The time-of-flight method was used for both neutron total cross section measurements and total $(n,\ensuremath{\gamma})$ reaction yield measurements at the pulsed spallation neutron source of Los Alamos Neutron Science Center. Well established resonance spectroscopy for these isotopes is essential for the analysis of parity violation data that were recently measured in palladium. DA - 2002/2// PY - 2002/2// DO - 10.1103/physrevc.65.024607 VL - 65 IS - 2 SP - SN - 1089-490X ER - TY - JOUR TI - H-3((p)over-right-arrow,gamma)He-4 reaction below E-p=80 keV AU - Canon, R. S. AU - Nelson, S. O. AU - Sabourov, K. AU - Wulf, E. AU - Weller, H. R. AU - Prior, R. M. AU - Spraker, M. AU - Kelley, J. H. AU - Tilley, D. R. T2 - Physical Review. C, Nuclear Physics DA - 2002/// PY - 2002/// VL - 65 IS - 4 SP - 044008-1 ER - TY - JOUR TI - Ab initio investigations of lithium diffusion in carbon nanotube systems AU - Meunier, V AU - Kephart, J AU - Roland, C AU - Bernholc, J T2 - PHYSICAL REVIEW LETTERS AB - Li-nanotube systems can substantially improve the capacity of Li-ion batteries by utilizing both nanotube exteriors and interiors. Our ab initio simulations show that while Li motion through the sidewalls is forbidden, Li ions can enter tubes through topological defects containing at least nine-sided rings, or through the ends of open-ended nanotubes. Once inside, their motion is not diffusion limited. These results suggest that "damaging" nanotube ropes by either chemical or mechanical means will yield superior material for electrochemical storage. DA - 2002/2/18/ PY - 2002/2/18/ DO - 10.1103/physrevlett.88.075506 VL - 88 IS - 7 SP - SN - 1079-7114 ER - TY - BOOK TI - Matter & interactions AU - Chabay, R. W. AU - Sherwood, B. A. CN - QC23.2 .C43 2002 DA - 2002/// PY - 2002/// PB - New York: Wiley SN - 0471354910 ER - TY - JOUR TI - Low-temperature Ar/N-2 remote plasma nitridation of SiO2 thin films AU - Khandelwal, A AU - Niimi, H AU - Lucovsky, G AU - Lamb, HH T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS AB - Low-temperature nitridation of SiO2 thin films by Ar/N2 remote plasma processing was investigated using on-line Auger electron spectroscopy, angle-resolved x-ray photoelectron spectroscopy (ARXPS), and optical emission spectroscopy (OES). Nitridation experiments were performed at 300 °C using 30 W Ar/N2 remote plasmas at 0.1 and 0.3 Torr. Ar/N2 remote plasma exposure of 5 nm SiO2 films for 30 min results in nitrogen incorporation throughout the films, independent of process pressure and plasma reactor configuration (i.e., upstream versus downstream N2 injection). ARXPS indicates a N–Si3 local bonding configuration with second nearest neighbor oxygen atoms. Ar/N2 remote plasma exposure at 0.1 Torr results in higher nitrogen concentrations (8–10 at. %). Reactor configuration has a negligible effect at 0.1 Torr; conversely, downstream N2 injection results in higher nitrogen concentrations (5–6 at. %) than upstream injection (3–4 at. %) at 0.3 Torr. OES indicates that the Ar/N2 remote plasmas contain N2 triplet excited states and ground-state N atoms. The Ar emission intensities and the saturation N concentrations in the resultant films follow similar trends with processing pressure and reactor configuration; the N2 first positive emission intensities run counter to these trends. We infer that low-temperature SiO2 nitridation by Ar/N2 remote plasmas is a two-step process: O removal by Ar+ ion bombardment and N insertion by plasma-generated active N species. Moreover, the first step appears to be rate limiting under the conditions employed in this study. Annealing the oxynitride films in N2 at 900 °C decreases the N concentration and results in a more uniform nitrogen distribution. DA - 2002/// PY - 2002/// DO - 10.1116/1.1513635 VL - 20 IS - 6 SP - 1989-1996 SN - 0734-2101 ER - TY - JOUR TI - General theory of quantum field mixing AU - Ji, C. R. AU - Mishchenko, Y. T2 - Physical Review. D, Particles and Fields DA - 2002/// PY - 2002/// VL - 65 IS - 9 SP - 096015-1 ER - TY - JOUR TI - Effective masses of diquarks AU - Maris, P T2 - FEW-BODY SYSTEMS AB - We study meson and diquark bound states using the rainbow-ladder truncation of QCD’s Dyson-Schwinger equations. The infrared strength of the rainbow-ladder kernel is described by two parameters. The ultraviolet behavior is fixed by the one-loop renormalization group behavior of QCD, which ensures the correct asymptotic behavior of the Bethe-Salpeter amplitudes and brings important qualitative benefits. The diquark with the lowest mass is the scalar, followed by the axialvector and pseudoscalar diquark. This ordering can be anticipated from the meson sector. DA - 2002/// PY - 2002/// DO - 10.1007/s00601-002-0111-7 VL - 32 IS - 1-2 SP - 41-52 SN - 1432-5411 ER - TY - JOUR TI - Delayed nickel decay in gamma-ray bursts AU - McLaughlin, GC AU - Wijers, RAMJ T2 - ASTROPHYSICAL JOURNAL AB - Recently observed emission lines in the X-ray afterglow of γ-ray bursts suggest that iron-group elements are either produced in the γ-ray burst or are present nearby. If this material is the product of a thermonuclear burn, then such material would be expected to be rich in nickel-56. If the nickel remains partially ionized, this prevents the electron capture reaction normally associated with the decay of nickel-56, dramatically increasing the decay timescale. Here we examine the consequences of rapid ejection of a fraction of a solar mass of iron-group material from the center of a collapsar/hypernova. The exact rate of decay then depends on the details of the ionization and, therefore, the ejection process. Future observations of iron, nickel, and cobalt lines can be used to diagnose the origin of these elements and to better understand the astrophysical site of γ-ray bursts. In this model, the X-ray lines of these iron-group elements could be detected in suspected hypernovae that did not produce an observable γ-ray burst due to beaming. DA - 2002/12/1/ PY - 2002/12/1/ DO - 10.1086/343858 VL - 580 IS - 2 SP - 1017-1023 SN - 1538-4357 KW - gamma rays : bursts KW - line : profiles KW - nuclear reactions, nucleosynthesis, abundances supernovae : general ER - TY - JOUR TI - Action and energy of the gravitational field AU - Brown, JD AU - Lau, , SR AU - York, JW T2 - ANNALS OF PHYSICS AB - We present a detailed examination of the variational principle for metric general relativity as applied to a quasilocal spacetime region M (that is, a region that is both spatially and temporally bounded). Our analysis relies on the Hamiltonian formulation of general relativity and thereby assumes a foliation of M into spacelike hypersurfaces Σ. We allow for near complete generality in the choice of foliation. Using a field-theoretic generalization of Hamilton–Jacobi theory, we define the quasilocal stress-energy momentum of the gravitational field by varying the action with respect to the metric on the boundary ∂M. The gravitational stress-energy momentum is defined for a two-surface B spanned by a spacelike hypersurface in spacetime. We examine the behavior of the gravitational stress-energy momentum under boosts of the spanning hypersurface. The boost relations are derived from the geometrical and invariance properties of the gravitational action and Hamiltonian. Finally, we present several new examples of quasilocal energy momentum, including a novel discussion of quasilocal energy momentum in the large-sphere limit toward spatial infinity. DA - 2002/5/1/ PY - 2002/5/1/ DO - 10.1006/aphy.2002.6250 VL - 297 IS - 2 SP - 175-218 SN - 0003-4916 ER - TY - JOUR TI - A new class of matrix models arising from the W1+infinity algebra AU - Herce, HD AU - Zemba, GR T2 - PHYSICS LETTERS B AB - We present a new class of hermitian one-matrix models originated in the W-infinity algebra: more precisely, the polynomials defining the W-infinity generators in their fermionic bilinear form are shown to expand the orthogonal basis of a class of random hermitian matrix models. The corresponding potentials are given, and the thermodynamic limit interpreted in terms of a simple plasma picture. The new matrix models can be successfully applied to the full bosonization of interesting one-dimensional systems, including all the perturbative orders in the inverse size of the system. As a simple application, we present the all-order bosonization of the free fermionic field on the one-dimensional lattice. DA - 2002/6/13/ PY - 2002/6/13/ DO - 10.1016/S0370-2693(02)01879-8 VL - 537 IS - 1-2 SP - 141-146 SN - 1873-2445 ER - TY - JOUR TI - The vector meson form factor analysis in light-front dynamics AU - Bakker, B. L. G. AU - Choi, H. M. AU - Ji, C. R. T2 - Physical Review. D, Particles and Fields DA - 2002/// PY - 2002/// VL - 65 IS - 11 SP - 116001-1 ER - TY - JOUR TI - Single electron tunneling of nanoscale TiSi2 islands on Si AU - Oh, J AU - Meunier, V AU - Ham, H AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - Nanoscale TiSi2 islands are formed by electron beam deposition of a few monolayers of titanium on an atomically clean silicon surface followed by in situ annealing at high temperatures (800–1000 °C). The lateral diameter of typical islands are ∼5 nm, and they form a nanoscale metal–semiconductor interface. Direct probing of the electrical characteristics of these islands on both p- and n-type Si substrates was performed using ultrahigh vacuum scanning tunneling microscopy and scanning tunneling spectroscopy. With the vacuum between the tip and the island as a second tunnel junction, we thus form a double-junction system for observation of single electron tunneling (SET) effects. Moreover, the small dimensions of the system allow room temperature observation. The results showed features in the I–V spectra attributed to single electron tunneling. Features were more evident when the island–Si junction was in reverse bias. For substrates with a thin epitaxial layer of intrinsic Si, the tunneling related features were enhanced for both doping types. The experimental results are compared with the standard theory and numerical values from the fitting are in agreement with the experimental structures. The results indicate that the nanoscale Schottky barrier of the island–substrate interface can be employed as a tunnel barrier in SET structures. DA - 2002/9/15/ PY - 2002/9/15/ DO - 10.1063/1.1499531 VL - 92 IS - 6 SP - 3332-3337 SN - 0021-8979 ER - TY - JOUR TI - Reaction pathways in remote plasma nitridation of ultrathin SiO2 films AU - Niimi, H AU - Khandelwal, A AU - Lamb, HH AU - Lucovsky, G T2 - JOURNAL OF APPLIED PHYSICS AB - Low-temperature nitridation of 3 nm SiO2 films using He/N2 and N2 remote radio frequency (rf) plasmas was investigated. On-line Auger electron spectroscopy and angle-resolved x-ray photoelectron spectroscopy (ARXPS) were employed to determine the concentration, spatial distribution, and local chemical bonding of nitrogen in the resultant films. Experiments were performed using a substrate temperature of 300 °C and 30 W rf power. Nitridation using an upstream He/N2 remote plasma at 0.1 Torr incorporates nitrogen at the top surface of the SiO2 film. In contrast, a lower concentration of nitrogen distributed throughout the film is obtained when the process pressure is increased to 0.3 Torr. ARXPS indicates a N–Si3 local bonding configuration, irrespective of the spatial distribution of N atoms. Slightly more nitrogen is incorporated using a downstream He/N2 plasma at each process pressure. By comparison, nitridation of SiO2 films using a N2 remote plasma at 0.1 Torr is very slow. Optical emission spectroscopy indicates that He dilution enhances the generation of N2+(B 2Σu+) species by altering the plasma electron energy distribution and by providing an additional kinetic pathway (Penning ionization). Changing the He/N2 remote plasma configuration from upstream to downstream (at 0.1 and 0.3 Torr) also enhances N2+(B 2Σu+) generation. For upstream He/N2 remote plasmas, the intensity of N2 first positive emission from N2(B 3Πg) states increases with pressure, whereas the N2+ first negative emission from N2+(B 2Σu+) states decreases. We infer from these observations that N2+ species are primarily responsible for top surface nitridation at 0.1 Torr, and that neutral species [N2(A 3Σu+) metastables and N atoms] are associated with sub-surface nitrogen incorporation. DA - 2002/1/1/ PY - 2002/1/1/ DO - 10.1063/1.1419208 VL - 91 IS - 1 SP - 48-55 SN - 1089-7550 ER - TY - JOUR TI - ROSAT/ASCA observations of the mixed-morphology supernova remnant W28 AU - Rho, J AU - Borkowski, KJ T2 - ASTROPHYSICAL JOURNAL AB - We present ROSAT PSPC and ASCA observations of the supernova remnant (SNR) W28. The overall shape of X-ray emission in W28 is elliptical, dominated by a centrally-concentrated interior emission, sharply peaked at the center. The ASCA spectra reveal emission lines of Ne, Mg, Si, and Fe K$\alpha$ and continuum extending at least up to 7 keV, showing thermal origin with a hot thermal component. We found that spectral variations are present in W28. The southwestern shell can be fit well by a plane-shock model with a temperature of 1.5 keV, and the northeastern shell, with a lower temperature of 0.56 keV. Unlike for the southwestern and northeastern shells, the central emission requires a two-temperature components with 0.6 keV and 1.8 keV. The low temperature component is similar to those seen in other Mixed-morphology SNRs. The X-ray luminosity of W28 is 6x 10^34 ergs/s, and the estimated X-ray mass is only ~20 - 25 solar mass. A comparison of W28 with other typical Mixed-morphology SNRs reveals significant differences in its X-ray properties; W28 has a significantly higher temperature and noticeable spectral variations. W28 belongs to a class of SNRs considered by Chevalier (1999), with a radiative shell interacting with clumpy molecular clouds. X-ray emission at its center is a ``fossil'' radiation from gas which was shocked early in the evolution of the remnant, and its centrally-peaked morphology could have been caused by processes such as evaporation, electron thermal conduction, and mixing induced by various hydrodynamical instabilities. But W28 poses a challenge for existing models of X-ray emission, because the evaporation model of White & Long (1991) is in conflict with observations, while the presence of temperature variations seems inconsistent with SNR models with efficient thermal conduction. DA - 2002/8/10/ PY - 2002/8/10/ DO - 10.1086/341192 VL - 575 IS - 1 SP - 201-216 SN - 1538-4357 KW - ISM : individual (W28) KW - supernova remnants KW - X-rays : ISM ER - TY - JOUR TI - QCD glueball Regge trajectory and the pomeron AU - Llanes-Estrada, FJ AU - Cotanch, , SR AU - Bicudo, PJD AU - Ribeiro, JEFT AU - Szczepaniak, A T2 - NUCLEAR PHYSICS A AB - Implementing many-body techniques successful in other fields, we report a glueball Regge trajectory emerging from diagonalizing a confining Coulomb gauge Hamiltonian for constituent gluons. Through a BCS vacuum ansatz and gap equation, the dressed gluons acquire a dynamic mass, of order 0.8 GeV, providing the quasiparticle degrees of freedom for a TDA glueball formulation. The TDA eigenstates for two constituent gluons have orbital, L, excitations with a characteristic energy of 0.4 GeV revealing a clear Regge trajectory. In particular, the JPC=2++ glueball coincides with the pomeron given by αP(t)=1.08+(0.25GeV−2)t. We also ascertain that lattice data supports our result. Finally, we conjecture on the odderon puzzle. DA - 2002/11/4/ PY - 2002/11/4/ DO - 10.1016/S0375-9474(02)01090-4 VL - 710 IS - 1-2 SP - 45-54 SN - 1873-1554 KW - glueball Regge trajectories KW - pomeron KW - odderon KW - QCD KW - Coulomb gauge Hamiltonian KW - TDA ER - TY - JOUR TI - Pseudodielectric function of ZnGeP2 from 1.5 to 6 eV AU - Blickle, V AU - Flock, K AU - Dietz, N AU - Aspnes, DE T2 - APPLIED PHYSICS LETTERS AB - We report pseudodielectric function data 〈ε〉=〈εa1〉+i〈εa2〉 and 〈ε〉=〈εc1〉+i〈εc2〉 for the optically uniaxial material ZnGeP2, critical point energies of structures in these data, and dielectric function data for the natural oxide. Annealing reduces the values of the peaks of 〈εa2〉. DA - 2002/7/22/ PY - 2002/7/22/ DO - 10.1063/1.1492022 VL - 81 IS - 4 SP - 628-630 SN - 0003-6951 ER - TY - JOUR TI - Piezoresponse force microscopy for polarity imaging of GaN AU - Rodriguez, BJ AU - Gruverman, A AU - Kingon, AI AU - Nemanich, RJ AU - Ambacher, O T2 - APPLIED PHYSICS LETTERS AB - The polarity distribution of GaN based lateral polarity heterostructures is investigated by piezoresponse force microscopy (PFM). Simultaneous imaging of surface morphology, as well as the phase and magnitude of the piezoelectric response, is performed by PFM on a GaN film with patterned polarities on a c-Al2O3 substrate. We demonstrate that the polarity distribution of GaN based lateral polarity heterostructures can be deduced from the phase image of the piezoresponse with nanometer scale spatial resolution. DA - 2002/6/3/ PY - 2002/6/3/ DO - 10.1063/1.1483117 VL - 80 IS - 22 SP - 4166-4168 SN - 1077-3118 ER - TY - JOUR TI - Issues in high-kappa gate stack interfaces AU - Misra, V AU - Lucovsky, G AU - Parsons, GN T2 - MRS BULLETIN DA - 2002/3// PY - 2002/3// DO - 10.1557/mrs2002.73 VL - 27 IS - 3 SP - 212-216 SN - 1938-1425 KW - gate stacks KW - high-dielectric-constant materials KW - high-kappa dielectrics KW - interface reactions KW - metal gates ER - TY - JOUR TI - Exploring timelike exclusive processes in the light-front approach AU - Ji, Chueng-Ryong AU - Choi, H. M. T2 - Nuclear Physics. A AB - We discuss a necessary nonvalence contribution in timelike exclusive processes. Utilizing a Schwinger-Dyson type of approach, we relate the nonvalence contribution to an ordinary light-front wave function that has been extensively tested in the spacelike exclusive processes. An application to $K_{\ell3}$ decays provides encouraging results. DA - 2002/// PY - 2002/// DO - 10.1016/s0375-9474(01)01517-2 VL - 699 IS - 1-2 SP - 344C–347 ER - TY - JOUR TI - Electronic states at the interface of Ti-Si oxide on Si(100) AU - Fulton, CC AU - Lucovsky, G AU - Nemanich, RJ T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - The requirement for high K dielectrics for Si devices includes both a low interface state density and a band alignment that blocks both electrons and holes. Titanium dioxide materials are known to exhibit dielectric constants of 80 or higher depending on the crystal structure and, as such, are prime candidates for gate dielectrics. We employ an ultrathin layer of SiO2 prior to the formation of a Ti oxide to limit the density of defect states. The electronic structure is observed during the stepwise growth of the oxide using x-ray and ultraviolet photoemission spectroscopy. Measurements indicate Ti oxide states at approximately 2 eV below the Si valence band maximum suggesting that the TiO2 conduction band aligns with the Si conduction band. The results indicate nearly flat bands in the silicon consistent with a low interface state density. DA - 2002/// PY - 2002/// DO - 10.1116/1.1493785 VL - 20 IS - 4 SP - 1726-1731 SN - 1071-1023 ER - TY - JOUR TI - Dynamical fermions in Hamiltonian lattice gauge theory AU - Lee, D T2 - NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS AB - We describe a first attempt to understand dynamical fermions within a Hamiltonian framework. As a testing ground we study compact QED3, which shares some important features of QCD4 such as confinement, glueballs, mesons, and chiral symmetry breaking. We discuss the methods used and show data for the chiral condensate. DA - 2002/3// PY - 2002/3// DO - 10.1016/S0920-5632(01)01924-7 VL - 106 SP - 1049-1051 SN - 1873-3832 ER - TY - JOUR TI - Comment on 'Boson peak in amorphous silicon: A numerical study' AU - Nakhmanson, S. M. AU - Drabold, D. A. AU - Mousseau, N. T2 - Physical Review. B, Condensed Matter and Materials Physics DA - 2002/// PY - 2002/// VL - 66 IS - 8 SP - 087201-1 ER - TY - JOUR TI - Surface segregation of Ge at SiGe(001) by concerted exchange pathways AU - Boguslawski, P AU - Bernholc, J T2 - PHYSICAL REVIEW LETTERS AB - The segregation of Ge during growth on SiGe(001) surfaces was investigated by ab initio calculations. Four processes involving adatoms rather than ad-dimers were considered. The two most efficient channels proceed by the concerted exchange mechanism and involve a swap between an incorporated Ge and a Si adatom, or between Si and Ge in the first and the second surface layers, respectively. The calculated activation energies of approximately 1.5 eV explain well the high-temperature experimental data. Segregation mechanisms involving step edges are much less efficient. DA - 2002/4/22/ PY - 2002/4/22/ DO - 10.1103/physrevlett.88.166101 VL - 88 IS - 16 SP - SN - 0031-9007 ER - TY - JOUR TI - Electromagnetic transition form factors of light mesons AU - Maris, P. AU - Tandy, P. C. T2 - Physical Review. C, Nuclear Physics DA - 2002/// PY - 2002/// VL - 65 IS - 4 SP - 045211-1 ER - TY - JOUR TI - Compact method for optical induction of proximal probe heating and elongation AU - Rosa, A.H. La AU - Hallen, Hans T2 - Appl. Opt. AB - A tapered, metal-coated, optical fiber probe will elongate when heated by light input through a fiber. The induced motion can be used for data storage or nanostructuring of a surface. The elongation produced by this alignment-free system is measured with force feedback in a near-field scanning optical microscope (NSOM). The input light intensity controls the elongation magnitude, which ranges from a few nanometers to more than 100 nm. A 0.5-mW input energy yields ∼20 nm of probe elongation. The elongation quantified here can create artifacts in any experiment using pulsed laser light with a NSOM or an atomic force microscope. DA - 2002/4// PY - 2002/4// DO - 10.1364/AO.41.002015 VL - 41 IS - 10 SP - 2015 - 19 UR - http://dx.doi.org/10.1364/AO.41.002015 ER - TY - JOUR TI - Antiphase boundaries in GaP layers grown on (001) Si by chemical beam epitaxy AU - Narayanan, V AU - Mahajan, S AU - Bachmann, KJ AU - Woods, V AU - Dietz, N T2 - ACTA MATERIALIA AB - We have investigated the origin of contrast features observed in coalesced GaP islands, deposited by chemical beam epitaxy on (001) Si, by high resolution transmission electron microscopy and conventional dark field electron microscopy. Our results indicate that these features are antiphase boundaries (APBs) lying on {110} planes. Image simulations have been performed to show that APBs can only be seen under specific defocus conditions in high resolution lattice images. The observed contrast is attributed to the presence of Ga–Ga and P–P wrong bonds at APBs. A model is proposed to show that the coalescence of GaP islands on the same Si terrace may not produce APBs, and the formation of such boundaries may require the presence of monoatomic steps, separating the coalescing islands. DA - 2002/4/2/ PY - 2002/4/2/ DO - 10.1016/S1359-6454(01)00408-6 VL - 50 IS - 6 SP - 1275-1287 SN - 1359-6454 KW - transmission electron microscopy (TEM) KW - epitaxy KW - GaP KW - islands KW - antiphase domains ER -