TY - JOUR TI - WIYN Open Cluster Study: UBVRI CCD Photometry of the Hyades-aged Open Cluster NGC 6633 AU - Roederer, I.U. AU - Deliyannis, C.P. AU - Platais, I. T2 - Bulletin of the American Astronomical Society DA - 2003/// PY - 2003/// VL - 203 SP - 1408 ER - TY - CHAP TI - Nuclear Physics AU - Gould, Christopher R. AU - Davis, E.David AU - Wilets, Lawrence AU - Siemens, Philip J. T2 - Encyclopedia of Physical Science and Technology A2 - Meyers, R.A. PY - 2003/// DO - 10.1016/b0-12-227410-5/00494-4 SP - 721-738 PB - Elsevier UR - http://dx.doi.org/10.1016/b0-12-227410-5/00494-4 ER - TY - SOUND TI - Physics with ultracold neutrons -- bottling neutrons for university research AU - Young, A.R. DA - 2003/10// PY - 2003/10// ER - TY - JOUR TI - Assembly of a Multi-Element, Ultralow Background, Germanium Spectrometer for Two Neutrino Double Beta-decay to the Excited State and Materials Assay AU - Sabourov, K. AU - Young, A.R. T2 - Bulletin of the American Physical Society DA - 2003/// PY - 2003/// VL - 48 SP - 97 ER - TY - JOUR TI - Results of UCN Depolarization and Transport Measurements on Quartz Guide Tubes Coated with Pulsed-Laser Deposited Diamond-Like Carbon AU - Pattie, R. AU - Makela, M. AU - Pitt, M. AU - Vogelaar, R.B. AU - Yuan, J. AU - Morris, C. AU - Pichlmaier, A. AU - Saunders, A. AU - Teasdale, B. AU - Geltenbort, P. AU - Adles, E.J. AU - Xu, Y.-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 - 2003/// PY - 2003/// VL - 48 SP - 113 ER - TY - CONF TI - The UCNA Project: a Measurement of the Beta-Asymmetry with UCN AU - Young, A.R. T2 - UCNA Collaboration, Workshop on Neutron Coherence and Confinement C2 - 2003/10// C3 - UCNA Collaboration, Workshop on Neutron Coherence and Confinement CY - Berlin DA - 2003/10// PY - 2003/10// ER - TY - JOUR TI - SEGA: a prototype detector element for Ge double beta-decay experiments AU - Kephart, J.D. AU - Young, A.R. T2 - Bulletin of the American Physical Society DA - 2003/// PY - 2003/// VL - 48 SP - 32 ER - TY - CONF TI - Overview of the UCNA Experiment, The UCNA Solid Deuterium Source at LANSCE & NCSU Plans for UCN Production and NNbar Search AU - Young, A.R. T2 - Fourth International Workshop on Ultracold and Cold Neutrons, Physics and Sources C2 - 2003/6// C3 - Fourth International Workshop on Ultracold and Cold Neutrons, Physics and Sources CY - St. Petersburg DA - 2003/6// PY - 2003/6// ER - TY - CONF TI - The UCNA project: a measurement of the beta-asymmetry of the neutron using ultracold neutrons AU - Young, A.R. AU - Adles, E.J. AU - Anaya, J.M. AU - Bowles, T.J. AU - Brun, T. AU - Carr, R. AU - Filippone, B.W. AU - Fowler, M. AU - Garcia, A. AU - Geltenbort, P. AU - Hill, R.E. AU - Hino, M. AU - Hoedl, S. AU - Hogan, G.E. AU - Ito, T.M. AU - Jones, K.W. AU - Kawai, T. AU - Kharitonov, A. AU - Kirch, K. AU - Kitagaki, T. AU - Krasnoshekova, I. AU - Lamoreaux, S.K. AU - Lasakov, M. AU - Lin, E. AU - Liu, C.-Y. AU - Makela, M. AU - Marek, L.J. AU - Martin, J.W. AU - Mckeown, R. AU - Morris, C.L. AU - Mortensen, R.N. AU - Pattie, R. AU - Pichlmaier, A. AU - Pitt, M. AU - Sabourov, K. AU - Seestrom, S.J. AU - Serebrov, A. AU - Smith, D. AU - Tatar, E. AU - Teasdale, W. AU - Tipton, B. AU - Utsuro, M. AU - Vasiliev, A. AU - Vogelaar, R.B. AU - Walstrom, P. AU - Wilhelmy, J. AU - Yuan, J. AU - Xu, Y.-P. T2 - Sixth Annual LANSCE User's Group Meeting C2 - 2003/10// C3 - Sixth Annual LANSCE User's Group Meeting CY - Los Alamos, New Mexiso DA - 2003/10// PY - 2003/10// ER - TY - JOUR TI - An apparatus to control and monitor the para-D2 concentration in a solid deuterium, superthermal source of ultra-cold neutrons AU - Liu, C.-Y. AU - Lamoreaux, S.K. AU - Saunders, A. AU - Smith, D. AU - Young, A.R. T2 - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment AB - Controlling and measuring the concentration of para-D2 is an essential step toward realizing solid deuterium as an intense ultra-cold neutron source. To this end, we implemented an experimental technique to convert para- to ortho-deuterium molecules by flowing D2 gas through a cryogenic cell filled with paramagnetic hydrous ferric oxide granules. This process efficiently reduced the para-D2 concentration from 33.3% to 1.5%. Rotational Raman spectroscopy was applied to measure the residual para-D2 contamination to better than 2 parts in 103, and the hydrogen contamination to 1 part in 103. We also contrast our optical technique to conventional thermal conductivity measurements of the para-D2 concentration, reporting some of the relevant strengths and weaknesses of our implementation of each technique. DA - 2003/8// PY - 2003/8// DO - 10.1016/s0168-9002(03)01666-8 VL - 508 IS - 3 SP - 257-267 J2 - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment LA - en OP - SN - 0168-9002 UR - http://dx.doi.org/10.1016/s0168-9002(03)01666-8 DB - Crossref ER - TY - JOUR TI - Depolarization of ultracold neutrons during their storage in material bottles AU - Serebrov, A.P. AU - Lasakov, M.S. AU - Vassiljev, A.V. AU - Krasnoschekova, I.A. AU - Rudnev, Yu.P. AU - Fomin, A.K. AU - Varlamov, V.E. AU - Geltenbort, P. AU - Butterworth, J. AU - Young, A.R. AU - Pesavento, U. T2 - Physics Letters A AB - The depolarization of ultracold neutrons (UCN) during their storage in traps has been investigated. The neutron spin-flip probability for the materials studied amounts to ∼(1–2)×10−5 per collision and does not depend on the temperature. The possible connection between the phenomenon of UCN depolarization and that of anomalous losses is discussed. DA - 2003/7// PY - 2003/7// DO - 10.1016/s0375-9601(03)00848-x VL - 313 IS - 5-6 SP - 373-379 J2 - Physics Letters A LA - en OP - SN - 0375-9601 UR - http://dx.doi.org/10.1016/s0375-9601(03)00848-x DB - Crossref ER - TY - JOUR TI - Quantitative characterization of biomolecular assemblies and interactions using atomic force microscopy AU - Yang, Yong AU - Wang, Hong AU - Erie, Dorothy A T2 - Methods DA - 2003/// PY - 2003/// VL - 29 IS - 2 SP - 175-187 ER - TY - JOUR TI - Functional oligomeric state of avian sarcoma virus integrase AU - Bao, Kogan K AU - Wang, Hong AU - Miller, Jamie K AU - Erie, Dorothy A AU - Skalka, Anna Marie AU - Wong, Isaac T2 - Journal of Biological Chemistry DA - 2003/// PY - 2003/// VL - 278 IS - 2 SP - 1323-1327 ER - TY - JOUR TI - DNA bending and unbending by MutS govern mismatch recognition and specificity AU - Wang, Hong AU - Yang, Yong AU - Schofield, Mark J AU - Du, Chunwei AU - Fridman, Yonatan AU - Lee, Susan D AU - Larson, Erik D AU - Drummond, James T AU - Alani, Eric AU - Hsieh, Peggy AU - others T2 - Proceedings of the National Academy of Sciences DA - 2003/// PY - 2003/// VL - 100 IS - 25 SP - 14822-14827 ER - TY - JOUR TI - Foregrounds for 21-cm observations of neutral gas at high redshift AU - Oh, S.P. AU - Mack, K.J. T2 - Monthly Notices of the Royal Astronomical Society AB - We investigate a number of potential foregrounds for an ambitious goal of future radio telescopes such as the Square Kilometer Array (SKA) and the Low Frequency Array (LOFAR): spatial tomography of neutral gas at high redshift in 21-cm emission. While the expected temperature fluctuations due to unresolved radio point sources is highly uncertain, we point out that free–free emission from the ionizing haloes that reionized the Universe should define a minimal bound. This emission is likely to swamp the expected brightness temperature fluctuations, making proposed detections of the angular patchwork of 21-cm emission across the sky unlikely to be viable. Hα observations with JWST could place an upper bound on the contribution of high-redshift sources to the free–free background. An alternative approach is to discern the topology of reionization from spectral features due to 21-cm emission along a pencil-beam slice. This requires tight control of the frequency-dependence of the beam in order to prevent foreground sources from contributing excessive variance. We also investigate potential contamination by galactic and extragalactic radio recombination lines (RRLs). These are unlikely to be show-stoppers, although little is known about the distribution of RRLs away from the Galactic plane. The mini-halo emission signal is always less than that of the intergalactic medium (IGM), making mini-haloes unlikely to be detectable. If they are seen, it will be only in the very earliest stages of structure formation at high redshift, when the spin temperature of the IGM has not yet decoupled from the cosmic microwave background. DA - 2003/// PY - 2003/// DO - 10.1111/j.1365-2966.2003.07133.x VL - 346 IS - 3 SP - 871-877 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0346267362&partnerID=MN8TOARS KW - galaxies : formation KW - cosmology : theory KW - large-scale structure of Universe ER - TY - CHAP TI - Unstable Periodic Orbits (UPOs) and Chaos Control in Neural Systems AU - Spano, M. L. AU - Ditto, W. L. AU - Dolan, K. AU - Moss, F. T2 - Epilepsy as a Dynamic Disease PY - 2003/// DO - 10.1007/978-3-662-05048-4_17 SP - 297-322 OP - PB - Springer Berlin Heidelberg SN - 9783642076657 9783662050484 UR - http://dx.doi.org/10.1007/978-3-662-05048-4_17 DB - Crossref ER - TY - JOUR TI - On the use of angle-action variables in semiclassical mechanics AU - Davis, Edward D. AU - Ghandour, Ghassan I. T2 - Physics Letters A AB - We discuss a novel uniform semiclassical approximation for the bound state wave functions of simple conservative systems (of one degree of freedom) which sheds light on the success of semiclassical transformation theory in dealing with angle-action variables. DA - 2003/3// PY - 2003/3// DO - 10.1016/s0375-9601(03)00174-9 VL - 309 IS - 1-2 SP - 1-4 J2 - Physics Letters A LA - en OP - SN - 0375-9601 UR - http://dx.doi.org/10.1016/s0375-9601(03)00174-9 DB - Crossref KW - uniform semiclassical approximation ER - TY - JOUR TI - Implementation of NOR gate by a chaotic Chua's circuit AU - Murali, K. AU - Sinha, S. AU - Ditto, W.L. T2 - International Journal of Bifurcation and Chaos in Applied Sciences and Engineering AB - We report the experimental implementation of the most fundamental NOR gate with a chaotic Chua's circuit by a simple threshold mechanism. This provides a proof-of-principle experiment to demonstrate the universal computing capability of chaotic circuits in continuous time systems. DA - 2003/// PY - 2003/// DO - 10.1142/S0218127403008053 VL - 13 IS - 9 SP - 2669-2672 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0242508464&partnerID=MN8TOARS KW - chaos KW - computing KW - circuit ER - TY - JOUR TI - Realization of the fundamental NOR gate using a chaotic circuit AU - Murali, K. AU - Sinha, S. AU - Ditto, W.L. T2 - Physical Review E - Statistical, Nonlinear, and Soft Matter Physics DA - 2003/// PY - 2003/// VL - 68 IS - 1 2 SP - 162051-162055 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-17144383290&partnerID=MN8TOARS ER - TY - CONF TI - Chaos in Neural Systems: From Epilepsy to Neurocomputing AU - Ditto, W.L. C2 - 2003/// C3 - Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings DA - 2003/// VL - 4 SP - 3830-3833 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-1542360051&partnerID=MN8TOARS ER - TY - CONF TI - Voltage-sensitive optical mapping for atrial fibrillation ablation treatment AU - Furman, M.D. AU - Simonotto, J.D. AU - Beaver, T.M. AU - Spano, M.L. AU - Ditto, W.L. AU - Liu, G. AU - Kavanagh, K.M. C2 - 2003/// C3 - Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings DA - 2003/// VL - 1 SP - 145-147 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-1542332789&partnerID=MN8TOARS ER - TY - CONF TI - Nonlinear Analysis of Failed Ventricular Defibrillation AU - Simonotto, J.D. AU - Furman, M.D. AU - Ditto, W.L. AU - Spano, M.L. AU - Liu, G. AU - Kavanagh, K.M. C2 - 2003/// C3 - Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings DA - 2003/// VL - 1 SP - 196-199 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-1542362570&partnerID=MN8TOARS ER - TY - JOUR TI - Effective number of neutrinos and baryon asymmetry from BBN and WMAP AU - Barger, V. AU - Kneller, James AU - Lee, H.-S. AU - Marfatia, D. AU - Steigman, G. T2 - Physics Letters B AB - We place constraints on the number of relativistic degrees of freedom and on the baryon asymmetry at the epoch of Big Bang Nucleosynthesis (BBN) and at recombination, using cosmic background radiation (CBR) data from the Wilkinson Microwave Anisotropy Probe (WMAP), complemented by the Hubble Space Telescope (HST) Key Project measurement of the Hubble constant, along with the latest compilation of deuterium abundances and Hii region measurements of the primordial helium abundance. The agreement between the derived values of these key cosmological and particle physics parameters at these widely separated (in time or redshift) epochs is remarkable. From the combination of CBR and BBN data, we find the 2σ ranges for the effective number of neutrinos Nν and for the baryon asymmetry (baryon to photon number ratio η) to be 1.7–3.0 and 5.53–6.76×10−10, respectively. DA - 2003/7// PY - 2003/7// DO - 10.1016/s0370-2693(03)00800-1 VL - 566 IS - 1-2 SP - 8-18 UR - http://dx.doi.org/10.1016/s0370-2693(03)00800-1 ER - TY - JOUR TI - Testing Two Nuclear Physics Approximations Used in the Standard Leaky‐Box Model for the Spallogenic Production of LiBeB AU - Kneller, J.P. AU - Phillips, J.R. AU - Walker, T.P. T2 - The Astrophysical Journal AB - The spallative production rates of lithium, beryllium, and boron (LiBeB) are a necessary component in any calculation of the evolution of these nuclei in the Galaxy. Previous calculations of these rates relied on two assumptions relating to the nuclear physics aspects: the straight-ahead approximation that describes the distribution of fragment energies and the assumption that the major contributor to the production rate arises from single-step reactions between primary cosmic-ray projectiles and interstellar medium targets. We examine both assumptions by using a semiempirical description for the spall's energy distribution and by including the reactions that proceed via intermediary fragments. After relaxing the straight-ahead approximation, we find that the changes in the production rates and emerging fluxes are small and do not warrant rejection of this approximation. In contrast, we discover that two-step reactions can alter the production rate considerably, leading to noticeable increases in the efficiency of producing the LiBeB nuclei. Motivated by this result, we introduce a cascade technique to compute the production rates exactly and find that the results differ only slightly from those of our two-step calculations. We thus conclude that terminating the reaction network at the two-step order is sufficiently accurate for current studies of spallation. DA - 2003/5/20/ PY - 2003/5/20/ DO - 10.1086/374592 VL - 589 IS - 1 I SP - 217-224 UR - http://dx.doi.org/10.1086/374592 KW - cosmic rays KW - nuclear reactions, nucleosynthesis, abundances ER - TY - JOUR TI - Big bang nucleosynthesis and CMB constraints on dark energy AU - Kneller, James AU - Steigman, G. T2 - Physical Review D AB - Current observational data favor cosmological models which differ from the standard model due to the presence of some form of dark energy and, perhaps, by additional contributions to the more familiar dark matter. Primordial nucleosynthesis provides a window on the very early evolution of the universe and constraints from big bang nucleosynthesis (BBN) can bound the parameters of models for dark matter or energy at redshifts of the order of ten billion. The spectrum of temperature fluctuations imprinted on the cosmic microwave background (CMB) radiation opens a completely different window on the universe at epochs from redshifts of the order of ten thousand to nearly the present. The CMB anisotropy spectrum provides constraints on new physics which are independent of and complementary to those from BBN. Here we consider three classes of models for the dark matter or energy: extra particles which were relativistic during the early evolution of the universe $(``X'');$ quintessence models involving a minimally coupled scalar field $(``Q'');$ models with a non-minimally coupled scalar field which modify the strength of gravity during the early evolution of the universe $(``G'').$ We constrain the parameters of these models using data from BBN and the CMB and identify the allowed regions in their parameter spaces consistent with the more demanding joint BBN and CMB constraints. For $``X''$ and $``Q''$ such consistency is relatively easy to find; it is more difficult for the $``G''$ models with an inverse power law potential for the scalar field. DA - 2003/3/10/ PY - 2003/3/10/ DO - 10.1103/physrevd.67.063501 VL - 67 IS - 6 SP - 063501–1 UR - http://dx.doi.org/10.1103/physrevd.67.063501 ER - TY - CONF TI - Reaction Rates and Nuclear Properties Relevant for Nucleosynthesis in Massive Stars and Far from Stability AU - Rauscher, T. AU - Fröhlich, C. AU - Guber, K. H. AB - Explosive nuclear burning in astrophysical environments produces unstable nuclei which again can be targets for subsequent reactions. In addition, it involves a large number of stable nuclides which are not fully explored by experiments, yet. Thus, it is necessary to be able to predict reaction cross sections and thermonuclear rates with the aid of theoretical models. Such predictions are also of interest for investigations at radioactive ion beam facilities. An extended library of theoretical cross sections and reaction rates is presented. The problem of alpha+nucleus potentials is addressed and new parametrizations presented. The problem of properly predicting cross sections at low level densities is illustrated by the 62Ni(n,gamma) reaction. C2 - 2003/6// C3 - Capture Gamma-Ray Spectroscopy and Related Topics DA - 2003/6// DO - 10.1142/9789812795151_0043 ER - TY - CONF TI - Resonance analysis of ^147Sm(n,α ) cross sections: Comparison to statistical model calculations and possible indications of non-statistical effects AU - Koehler, P. E. AU - Gledenov, Yu. M. AU - Rauscher, T. AU - Fröhlich, C. C2 - 2003/10// C3 - APS Division of Nuclear Physics Meeting Abstracts DA - 2003/10// ER - TY - JOUR TI - The RHIC gold rush AU - Schäfer, T. T2 - Phys.World DA - 2003/// PY - 2003/// VL - 16N6 SP - 31-35 UR - http://inspirehep.net/record/625406 ER - TY - CONF TI - Loops and power counting in the high density effective field theory AU - Schäfer, Thomas C2 - 2003/10// C3 - eConf DA - 2003/10// VL - C030614 SP - 038 UR - http://inspirehep.net/record/630629 ER - TY - CONF TI - Effective theory of the color flavor locked phase AU - Schäfer, Thomas AB - We explain how an effective theory of the CFL phase can be used to study the effect of the strange quark mass on the ground state and the excitation spectrum. We also apply the effective theory to the problem of neutrino emission from a CFL quark core inside a neutron star. C2 - 2003/8// C3 - Nucl.Phys.A DA - 2003/8// DO - 10.1016/S0375-9474(02)01532-4 VL - 715 SP - 879-882 UR - http://inspirehep.net/record/594036 ER - TY - JOUR TI - Instanton contribution to scalar charmonium and glueball decays AU - Zetocha, Valeriu AU - Schäfer, Thomas T2 - Phys.Rev.D AB - We study instanton contributions to hadronic decays of the scalar glueball, the pseudoscalar charmonium state ${\ensuremath{\eta}}_{c},$ and the scalar charmonium state ${\ensuremath{\chi}}_{c}.$ Hadronic decays of the ${\ensuremath{\eta}}_{c}$ are of particular interest. The three main decay channels are $K\overline{K}\ensuremath{\pi},\ensuremath{\eta}\ensuremath{\pi}\ensuremath{\pi}$ and ${\ensuremath{\eta}}^{\ensuremath{'}}\ensuremath{\pi}\ensuremath{\pi},$ each with an unusually large branching ratio $\ensuremath{\sim}5%.$ On the quark level, all three decays correspond to an instanton type vertex $(\overline{c}c)(\overline{s}s)(\overline{d}d)(\ifmmode \bar{u}\else \={u}\fi{}u).$ We show that the total decay rate into three pseudoscalar mesons can be reproduced using an instanton size distribution consistent with phenomenology and lattice results. Instantons correctly reproduce the ratio $B(\ensuremath{\pi}\ensuremath{\pi}\ensuremath{\eta})/B(\ensuremath{\pi}\ensuremath{\pi}{\ensuremath{\eta}}^{\ensuremath{'}})$ but overpredict the ratio $B(K\overline{K}\ensuremath{\pi})/B[\ensuremath{\pi}\ensuremath{\pi}\ensuremath{\eta}({\ensuremath{\eta}}^{\ensuremath{'}})].$ We consider the role of scalar resonances and suggest that the decay mechanism can be studied by measuring the angular distribution of decay products. DA - 2003/12// PY - 2003/12// DO - 10.1103/PhysRevD.67.114003 VL - 67 SP - 114003 UR - http://inspirehep.net/record/604223 ER - TY - CONF TI - Superdense matter AU - Schäfer, Thomas AB - We review recent work on the phase structure of QCD at very high baryon density. We introduce the phenomenon of color superconductivity and discuss the use of weak coupling methods. We study the phase structure as a function of the number of flavors and their masses. We also introduce effective theories that describe low energy excitations at high baryon density. Finally, we comment on the possibility of kaon condensation at very large baryon density. C2 - 2003/1// C3 - Pramana DA - 2003/1// DO - 10.1007/BF02705169 VL - 60 SP - 697-710 UR - http://inspirehep.net/record/581739 KW - quantum chromodynamics KW - dense matter ER - TY - JOUR TI - QCD and the eta-prime mass: Instantons or confinement? AU - Schäfer, Thomas T2 - Phys.Rev.D AB - We argue that lattice calculations of the $\eta'$ mass in QCD with $N_c=2$ colors performed at non-zero baryon chemical potential can be used to study the mechanism responsible for the mass of the $\eta'$. QCD with two colors is an ideal laboratory because it exhibits confinement, chiral symmetry breaking and a would-be $U(1)_A$ Goldstone boson at all densities. Since the instanton density and the confinement scale vary with density in a very different way, instantons are clearly distinguishable from other possible mechanisms. There is an instanton prediction for the $\eta'$ mass at large density that can be compared to lattice results. The density dependence of the instanton contribution is a simple consequence of the integer topological charge carried by the instanton. We also argue that $N_c=3$ color QCD at finite isospin density can be used in order to study the origin of OZI-violation in the scalar sector. DA - 2003/11// PY - 2003/11// DO - 10.1103/PhysRevD.67.074502 VL - 67 SP - 074502 UR - http://inspirehep.net/record/602623 ER - TY - CONF TI - Long range fading prediction to enable adaptive transmission at another carrier AU - Yang, Tung-Sheng AU - Duel-Hallen, A. AU - Hallen, H. AB - Adaptive transmission techniques, such as adaptive modulation and coding, adaptive power control, adaptive transmitter antenna diversity, etc., usually require accurate channel estimation and feedback of channel state information (CSI). For fast vehicle speeds, reliable adaptive transmission also requires long range prediction (LRP) of future CSI since the channel conditions are rapidly time-variant. In this paper, we propose to use past channel observations of one carrier to predict future CSI and perform adaptive modulation without feedback for another correlated carrier. We develop the minimum mean-square-error (MMSE) long range channel prediction algorithm that utilizes the time and frequency domain correlation function of the Rayleigh fading channel. An adaptive MMSE prediction method is also proposed. 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. We use a standard stationary fading channel model (Jakes model) and a novel physical channel model to test our algorithm. Significant gains relative to non-adaptive techniques are demonstrated for sufficiently correlated channels and realistic prediction range. C2 - 2003/// C3 - 2003 4th IEEE Workshop on Signal Processing Advances in Wireless Communications - SPAWC 2003 (IEEE Cat. No.03EX689) CY - Piscataway, NJ, USA DA - 2003/// DO - 10.1109/SPAWC.2003.1318949 SP - 195 - 9 UR - https://doi.org/10.1109/SPAWC.2003.1318949 ER - TY - CONF TI - A Split-Tip Proximal Probe for Nanoscale Deposition of Molecules with Controlled In-Plane Orientation AU - Hallen, H.D. AU - Taylor, Michael C2 - 2003/// C3 - Proceedings of the 2003 NSF DMII Grantee's Conference CY - Birmingham, AL DA - 2003/// ER - TY - JOUR TI - Phase Space Manipulation of Cold Free Radical OH Molecules AU - Bochinski, J. R. AU - Hudson, Eric R. AU - Lewandowski, H. J. AU - Meijer, Gerard AU - Ye, Jun T2 - Physical Review Letters AB - We report bunching, slowing, and acceleration of a supersonically cooled beam of diatomic hydroxyl radicals (OH). \textit{In situ} observation of laser-induced fluorescence along the beam propagation path allows for detailed characterization of longitudinal phase-space manipulation of OH molecules through the Stark effect by precisely sequenced inhomogeneous electric fields. DA - 2003/// PY - 2003/// DO - 10.1103/physrevlett.91.243001 VL - 91 IS - 24 ER - TY - JOUR TI - Stark manipulation of the free radical OH AU - Bochinski, J.R. AU - Hudson, E.R. AU - Ye, J. T2 - Postconference Digest Quantum Electronics and Laser Science, 2003. QELS. AB - Our latest work towards utilizing Stark deceleration on a beam of molecular free radicals is presented. Observed signal enhancement using hexapole focusing and the necessary phase space matching conditions are discussed. DA - 2003/// PY - 2003/// DO - 10.1109/qels.2003.238172 ER - TY - JOUR TI - Near-field optical lithography of a conjugated polymer AU - Riehn, R. AU - Charas, A. AU - Morgado, J. AU - Cacialli, F. T2 - Applied Physics Letters AB - We report the fabrication of poly(p-phenylene vinylene) nanostructures by direct scanning near-field lithography of its soluble precursor. The technique is based on the spatially selective inhibition of the precursor solubility by exposure to the ultraviolet optical field present at the apex of scanning near-field fiber probes with aperture diameters between 40 and 80 nm (±5 nm). After development in methanol and thermal conversion under vacuum we obtain features with a minimum dimension of 160 nm. We demonstrate the use of the technique for the direct writing of two-dimensional photonic crystals with intentional defects and a periodicity relevant to applications in the visible range. Using a Bethe–Bouwkamp model, we then discuss the influence of probe size, tip-sample distance, and film thickness on the resolution of the lithographic process. We also discuss limitations to the resolution that can arise from physical properties of the lithographic medium. DA - 2003/// PY - 2003/// DO - 10.1063/1.1539278 VL - 82 IS - 4 SP - 526-528 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0037467971&partnerID=MN8TOARS ER - TY - JOUR TI - Time dependence of liquid-helium fluorescence AU - McKinsey, D.N. AU - Brome, C.R. AU - Dzhosyuk, S.N. AU - Golub, R. AU - Habicht, K. AU - Huffman, P.R. AU - Korobkina, E. AU - Lamoreaux, S.K. AU - Mattoni, C.E.H. AU - Thompson, A.K. AU - Yang, L. AU - Doyle, J.M. T2 - Physical Review A - Atomic, Molecular, and Optical Physics DA - 2003/// PY - 2003/// VL - 67 IS - 6 SP - 627161-6271610 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-5044229331&partnerID=MN8TOARS ER - TY - JOUR TI - Precision neutron interferometric measurements and updated evaluations of the n-p and n-d coherent neutron scattering lengths AU - Schoen, K. AU - Jacobson, D.L. AU - Arif, M. AU - Huffman, P.R. AU - Black, T.C. AU - Snow, W.M. AU - Lamoreaux, S.K. AU - Kaiser, H. AU - Werner, S.A. T2 - Physical Review C - Nuclear Physics DA - 2003/// PY - 2003/// VL - 67 IS - 4 SP - 440051-4400521 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0038131804&partnerID=MN8TOARS ER - TY - JOUR TI - Precision neutron interferometric measurement of the nd coherent neutron scattering length and consequences for models of three-nucleon forces AU - Black, T.C. AU - Huffman, P.R. AU - Jacobson, D.L. AU - Snow, W.M. AU - Schoen, K. AU - Arif, M. AU - Kaiser, H. AU - Lamoreaux, S.K. AU - Werner, S.A. T2 - Physical Review Letters DA - 2003/// PY - 2003/// VL - 90 IS - 19 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0037595594&partnerID=MN8TOARS ER - TY - JOUR TI - Performance of a large-area avalanche photodiode at low temperature for scintillation detection AU - Yang, L. AU - Dzhosyuk, S.N. AU - Gabrielse, J.M. AU - Huffman, P.R. AU - Mattoni, C.E.H. AU - Maxwell, S.E. AU - McKinsey, D.N. AU - Doyle, J.M. T2 - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment AB - We investigate the performance of a large-area (13mm×13mm) avalanche photodiode at temperatures ranging from 4.2 to 77K. We find that the gain, at a given bias voltage, increases with decreasing temperature down to 40K, below which a premature breakdown phenomenon occurs. The quantum efficiency of the device decreases with decreasing temperature until approximately 40K, at which point it drops abruptly to <15% of its room temperature value. The sensitivity of the device above 40K makes it a good candidate for detection of scintillation light in low-temperature systems. DA - 2003/// PY - 2003/// DO - 10.1016/S0168-9002(03)01665-6 VL - 508 IS - 3 SP - 388-393 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0041743957&partnerID=MN8TOARS KW - scintillation detection KW - avalanche photodiode KW - quantum efficiency KW - low temperature KW - carrier freeze-out ER - TY - PAT TI - Diffraction enhanced x-ray imaging of articular cartilage AU - Chapman, L. D. AU - Hasnah, M. O. AU - Oltulu, O. AU - Zhong, Z. AU - Mollenhauer, J. Muehleman AU - C., Kuettner AU - K., Aurich AU - M., Pisano AU - E. D., Johnston AU - R. E., Thomlinson AU - W. C., AU - Sayers, D. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - PAT TI - Broadband spectroscopic rotating compensator ellipsometer AU - Aspnes, D. E. AU - Opsal, J. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - JOUR TI - Statistics of defect motion in spatiotemporal chaos in inclined layer convection AU - Daniels, K. E. AU - Bodenschatz, E. T2 - Chaos: An Interdisciplinary Journal of Nonlinear Science AB - We report experiments on defect-tracking in the state of undulation chaos observed in thermal convection of an inclined fluid layer. We characterize the ensemble of defect trajectories according to their velocities, relative positions, diffusion, and gain and loss rates. In particular, the defects exhibit incidents of rapid transverse motion which result in power law distributions for a number of quantitative measures. We examine connections between this behavior and Levy flights and anomalous diffusion. In addition, we describe time-reversal and system size invariance for defect creation and annihilation rates. DA - 2003/// PY - 2003/// DO - 10.1063/1.1536330 VL - 13 IS - 1 SP - 55 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000181202400004&KeyUID=WOS:000181202400004 ER - TY - JOUR TI - Localized Transverse Bursts in Inclined Layer Convection AU - Daniels, Karen E. AU - Wiener, Richard J. AU - Bodenschatz, Eberhard T2 - Physical Review Letters AB - We investigate a novel bursting state in inclined layer thermal convection in which convection rolls exhibit intermittent, localized, transverse bursts. With increasing temperature difference, the bursts increase in duration and number while exhibiting a characteristic wave number, magnitude, and size. We propose a mechanism which describes the duration of the observed bursting intervals and compare our results to bursting processes in other systems. DA - 2003/9/9/ PY - 2003/9/9/ DO - 10.1103/physrevlett.91.114501 VL - 91 IS - 11 SP - 114501 ER - TY - JOUR TI - Middle-school texts don't make the grade AU - Hubisz, J T2 - PHYSICS TODAY AB - Thousands of teachers are saddled with error-filled physical science textbooks that fail to present what science is all about. Physicists deserve some of the blame. DA - 2003/5// PY - 2003/5// DO - 10.1063/1.1583534 VL - 56 IS - 5 SP - 50-54 SN - 1945-0699 ER - TY - JOUR TI - Massless three-dimensional Qed with explicit fermions AU - Lee, D. AU - Maris, P. T2 - Physical Review. D, Particles and Fields DA - 2003/// PY - 2003/// VL - 67 IS - 7 SP - 076002-1 ER - TY - JOUR TI - Unified many-body approach to mesons, glueballs and hybrids AU - Cotanch, , SR T2 - PROGRESS IN PARTICLE AND NUCLEAR PHYSICS, VOL 50, NO 2 AB - A unified quark and gluon description of mesons, glueballs and exotic hybrids is presented for a relativistic field theoretical Hamiltonian in the Coulomb gauge. The effective QCD Hamiltonian entails a linear confining interaction with slope predetermined by lattice theory and is approximately diagonalized using different many-body techniques: BCS for the vacuum ground state; TDA and RPA for the excited hadron spectrum. Chiral symmetry rigorously emerges and is spontaneously broken by the model BCS vacuum which contains dynamically generated constituent quark and gluon condensates described by respective gap equations. The observed low energy meson spectrum and the quenched lattice glueball measurements are reproduced along with a Regge trajectory consistent with the Pomeron. Using generalized vector meson dominance, glueball decays are predicted and a glueball photoproduction experimental signature is predicted. Finally, a variational relativistic three quasiparticle calculation for hybrid mesons is reported which concurs with alternative model predictions that the lightest hybrid states are near but above 2 GeV. This strongly indicates that the recently observed JPC = 1 −+ exotics at 1.4 and 1.6 GeV are more likely four quark states. DA - 2003/// PY - 2003/// DO - 10.1016/S0146-6410(03)00028-0 VL - 50 IS - 2 SP - 353-362 SN - 0146-6410 ER - TY - JOUR TI - Simplified bond-hyperpolarizability model of second- and fourth-harmonic generation: application to Si-SiO2 interfaces AU - Aspnes, DE AU - Hansen, JK AU - Peng, HJ AU - Powell, GD AU - Wang, JFT T2 - PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS AB - Abstract We recently developed a simplified bond‐hyperpolarizability model (SBHM) to describe the variation of second‐ and fourth‐harmonic‐generation (SHG, FHG) intensities as a function of sample azimuth angle, and applied it to various Si‐dielectric interfaces. The approach provides an efficient representation of these data with fewer parameters than required by Fourier or tensorial representations. In addition, these parameters have a direct physical meaning in microscopic terms. The model is simple enough to allow analytic expressions to be obtained for SHG and FHG intensities for (001) and (111) interfaces. SHG absorption is shown to result in easily recognized features in anisotropy data. Relative amplitudes of FHG intensities of the (001)Si–SiO 2 interface among the three nonvanishing polarization combinations are shown to be consistent to a factor of about 2. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) DA - 2003/12// PY - 2003/12// DO - 10.1002/pssb.200303825 VL - 240 IS - 3 SP - 509-517 SN - 1521-3951 ER - TY - JOUR TI - Measurement of electron backscattering in the energy range of neutron beta decay AU - Martin, JW AU - Yuan, J AU - Hoedl, SA AU - Filippone, BW AU - Fong, D AU - Ito, TM AU - Lin, E AU - Tipton, B AU - Young, AR T2 - PHYSICAL REVIEW C AB - We report on the first detailed measurements of electron backscattering from low $Z$ targets at energies up to $124\phantom{\rule{0.3em}{0ex}}\text{keV}$. Both energy and angular distributions of the backscattered electrons are measured and compared with electron transport simulations based on the Geant4 and Penelope Monte Carlo simulation codes. Comparisons are also made with previous, less extensive, measurements and with measurements at lower energies. DA - 2003/11// PY - 2003/11// DO - 10.1103/physrevc.68.055503 VL - 68 IS - 5 SP - 32 SN - 1089-490X ER - TY - JOUR TI - Wavelength-dependent Raman scattering of hydrogenated amorphous silicon carbon with red, green, and blue light excitation AU - Park, M AU - Sakhrani, V AU - Maria, JP AU - Cuomo, JJ AU - Teng, CW AU - Muth, JF AU - Ware, ME AU - Rodriguez, BJ AU - Nemanich, RJ T2 - JOURNAL OF MATERIALS RESEARCH AB - This study presents results of wavelength-dependent Raman scattering from amorphous silicon carbon (a-Si:C:H). The a-Si:C:H films were produced by radio-frequency plasma-enhanced chemical vapor deposition. Prior results with amorphous carbon indicate that laser excitation selectively probes clusters with differing sizes. Our measurements with a-Si:C:H indicate that when using red (632.8 nm), green (514.5 nm), and blue (488.0 nm) excitation, the Raman D and G peaks shift to higher wave numbers as the excitation energy increases. The higher frequency is associated with smaller clusters that are preferentially excited with higher photon energy. It appears that photoluminescence occurs due to radiative recombination from intracluster transitions in Si-alloyed sp 2 -bonded carbon clusters DA - 2003/4// PY - 2003/4// DO - 10.1557/JMR.2003.0106 VL - 18 IS - 4 SP - 768-771 SN - 2044-5326 ER - TY - JOUR TI - The interface phase and the Schottky barrier for a crystalline dielectric on silicon AU - McKee, RA AU - Walker, FJ AU - Nardelli, MB AU - Shelton, WA AU - Stocks, GM T2 - SCIENCE AB - The barrier height for electron exchange at a dielectric-semiconductor interface has long been interpreted in terms of Schottky's theory with modifications from gap states induced in the semiconductor by the bulk termination. Rather, we show with the structure specifics of heteroepitaxy that the electrostatic boundary conditions can be set in a distinct interface phase that acts as a "Coulomb buffer." This Coulomb buffer is tunable and will functionalize the barrier-height concept itself. DA - 2003/6/13/ PY - 2003/6/13/ DO - 10.1126/science.1083894 VL - 300 IS - 5626 SP - 1726-1730 SN - 0036-8075 ER - TY - JOUR TI - The B-10((p)over-right-arrow, gamma)C-11 reaction at astrophysically relevant energies AU - Tonchev, AP AU - Nelson, SO AU - Sabourov, K AU - Crowley, BT AU - Joshi, K AU - Weller, HR AU - Kelley, JH AU - Prior, RM AU - Spraker, M AU - Kalantar-Nayestanaki, N T2 - PHYSICAL REVIEW C AB - The $^{10}\mathrm{B}(\stackrel{P\vec}{p},\ensuremath{\gamma})^{11}\mathrm{C}$ reaction was studied by detecting the $\ensuremath{\gamma}$-rays produced when 100-, 130-, and $160\text{\ensuremath{-}}\text{keV}$ polarized protons were stopped in a thick $^{10}\mathrm{B}$ target. Polarized and unpolarized incident beams were used to measure the cross section and vector analyzing power as a function of angle and energy for capture to the ground $({J}^{\ensuremath{\pi}}=3∕{2}^{\ensuremath{-}})$, the second $(E=4319\phantom{\rule{0.3em}{0ex}}\mathrm{keV},{J}^{\ensuremath{\pi}}=5∕{2}^{\ensuremath{-}})$, and the fifth $(E=6478\phantom{\rule{0.3em}{0ex}}\text{keV},{J}^{\ensuremath{\pi}}=7∕{2}^{\ensuremath{-}})$ excited states of $^{11}\mathrm{C}$. The data were analyzed to obtain the amplitudes and phases of the contributing transition-matrix elements at each measured energy for all three transitions. Values of the astrophysical $S$ factors were obtained from the cross section data and are compared to previous results. A direct capture plus resonance model calculation was performed in an attempt to account for all measured quantities. It was found that the large $(\ensuremath{\sim}32%)$ value of ${A}_{y}(90\ifmmode^\circ\else\textdegree\fi{})$ observed in the case of capture to the ground state could be accounted for by including the sub-threshold resonance at $8420\phantom{\rule{0.3em}{0ex}}\text{keV}$. DA - 2003/10// PY - 2003/10// DO - 10.1103/physrevc.68.045803 VL - 68 IS - 4 SP - SN - 1089-490X ER - TY - JOUR TI - Status and prospects of neutrino oscillations: terrestrial sources AU - Markoff, DM T2 - JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS AB - By exploring the oscillation mixing angle versus mass difference allowed regions, terrestrial-based experiments have advanced our understanding of the ν oscillation solutions proposed by the measurements of neutrinos produced in the sun and in the atmosphere. This paper reviews the contribution of reactor anti-neutrino experiments and of accelerator neutrino experiments to the development of these theories. Selected experiments are briefly described, the results are presented and the impact on our understanding of neutrino oscillations is discussed. DA - 2003/8// PY - 2003/8// DO - 10.1088/0954-3899/29/8/367 VL - 29 IS - 8 SP - 1885-1892 SN - 1361-6471 ER - TY - JOUR TI - Response to “Comment on ‘Intrinsic electron transport properties of carbon nanotube Y junctions’ ” [Appl. Phys. Lett. 83, 1674 (2003)] AU - Meunier, Vincent AU - Nardelli, Marco Buongiorno AU - Bernholc, J. AU - Zacharia, Thomas AU - Charlier, Jean-Christophe T2 - Applied Physics Letters AB - First Page DA - 2003/8/25/ PY - 2003/8/25/ DO - 10.1063/1.1604949 VL - 83 IS - 8 SP - 1676-1677 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.1604949 DB - Crossref ER - TY - JOUR TI - Radiation damage at the aluminum entrance window of the SINQ Target 3 AU - Lu, W AU - Wechsler, MS AU - Dai, Y T2 - JOURNAL OF NUCLEAR MATERIALS AB - Calculations are underway to determine radiation damage (displacement, helium, and hydrogen production) at the entrance window of the SINQ Target 3 (Mark II Type). Damage production rates were determined in two ways. In Method 1, the displacement, He, and H cross-sections were folded into the proton and neutron fluxes to give the three defect production rates separately for protons and neutrons. In Method 2, MCNPX with a computer model of SINQ was used directly to calculate the three production rates due to the combined effects of protons and neutrons. The production rates at the central tip of the target by Method 1 are 4.1 and 0.47 dpa/yr per mA for protons and neutrons, respectively, giving a total of 4.6 dpa/yr per mA. By Method 2 using several approaches, we obtain a range of production rates from 3.6 to 4.1 dpa/yr per mA. For helium, the production rates are calculated to be about 1000 and a range from 950 to 1580 appmHe/yr per mA, respectively. LAHET calculations indicate that the helium is completely retained in the irradiated aluminum. For hydrogen, the calculations indicate that perhaps only about half of the hydrogen produced is retained. Method 1 gives about 3500 appmH/yr per mA retained and Method 2 gives a range from 3500 to 4400 appmH/yr per mA. DA - 2003/5/15/ PY - 2003/5/15/ DO - 10.1016/S0022-3115(03)00082-5 VL - 318 SP - 176-184 SN - 1873-4820 ER - TY - JOUR TI - Precise coincidence of effective potentials in the integral and fractional quantum Hall effects AU - Lado, Fred T2 - Physics Letters. A DA - 2003/// PY - 2003/// DO - 10.1016/S0375-9601(03)005724-7 VL - 312 IS - 1-2 SP - 101–107 ER - TY - JOUR TI - Optical and structural studies of hydride vapor phase epitaxy grown GaN AU - Chang, YC AU - Cai, AL AU - Muth, JF AU - Kolbas, RM AU - Park, M AU - Cuomo, JJ AU - Hanser, A AU - Bumgarner, J T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - Thick films of hydride vapor phase epitaxy (HVPE) grown GaN were studied by various techniques. Time-integrated and time-resolved photoluminescence (PL) measurements were performed at room temperature and 77 K. The time-integrated PL spectrum has no observed deep-level transitions and a very narrow linewidth, which indicates good material quality. Time-resolved PL spectra are also presented and the temporal evolution of the PL around the band-gap exhibits a biexponential decay with a fast and a slow decay component. Cathodoluminescence, x-ray, and Raman spectroscopy were also used. The full width half maximum of the x-ray rocking curve for our sample is approximately 375 arcsec. The polarized Raman spectra exhibited only the allowed modes. The deposited GaN films were found to be relatively stress free. The x ray and Raman analysis also revealed that the HVPE-grown GaN films are of high crystal quality. The effect of thermal annealing on the sample was also investigated by time-integrated and time-resolved PL and Raman spectroscopy. No significant changes in the material were observed in either time-integrated or Raman spectroscopy. The film was thermally stable upon annealing up to 1000 °C in N2 ambient based on the results of these measurements. In time-resolve photoluminescence measurement, the temporal evolution of the band-edge transitions broadens after each annealing step and is significantly different after the 1000 °C anneal. DA - 2003/// PY - 2003/// DO - 10.1116/1.1568346 VL - 21 IS - 3 SP - 701-705 SN - 0734-2101 ER - TY - JOUR TI - Measurement of the band offsets of SiO2 on clean n- and p-type GaN(0001) AU - Cook, TE AU - Fulton, CC AU - Mecouch, WJ AU - Tracy, KM AU - Davis, RF AU - Hurt, EH AU - Lucovsky, G AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - The band alignment at the SiO2-GaN interface is important for passivation of high voltage devices and for gate insulator applications. X-ray photoelectron spectroscopy and ultraviolet photoemission spectroscopy have been used to observe the interface electronic states as SiO2 was deposited on clean GaN(0001) surfaces. The substrates, grown by metallorganic chemical vapor deposition, were n- (1×1017) and p-type (2×1018) GaN on 6H-SiC(0001) with an AlN(0001) buffer layer. The GaN surfaces were atomically cleaned via an 860 °C anneal in an NH3 atmosphere. For the clean surfaces, n-type GaN showed upward band bending of 0.3±0.1 eV, while p-type GaN showed downward band bending of 1.3±0.1 eV. The electron affinity for n- and p-type GaN was measured to be 2.9±0.1 and 3.2±0.1 eV, respectively. To avoid oxidizing the GaN, layers of Si were deposited on the clean GaN surface via ultrahigh vacuum e-beam deposition, and the Si was oxidized at 300 °C by a remote O2 plasma. The substrates were annealed at 650 °C for densification of the SiO2 films. Surface analysis techniques were performed after each step in the process, and yielded a valence band offset of 2.0±0.2 eV and a conduction band offset of 3.6±0.2 eV for the GaN-SiO2 interface for both p- and n-type samples. Interface dipoles of 1.8 and 1.5 eV were deduced for the GaN-SiO2 interface for the n- and p-type surfaces, respectively. DA - 2003/4/1/ PY - 2003/4/1/ DO - 10.1063/1.1559424 VL - 93 IS - 7 SP - 3995-4004 SN - 0021-8979 ER - TY - JOUR TI - Level densities in Fe-56,Fe-57 and Mo-96,Mo-97 AU - Schiller, A AU - Algin, E AU - Bernstein, LA AU - Garrett, PE AU - Guttormsen, M AU - Hjorth-Jensen, M AU - Johnson, CW AU - Mitchell, GE AU - Rekstad, J AU - Siem, S AU - Voinov, A AU - Younes, W T2 - PHYSICAL REVIEW C AB - Level densities up close to the neutron binding energy have been extracted from primary $\ensuremath{\gamma}$ spectra for $^{56,57}\mathrm{Fe}$ and $^{96,97}\mathrm{Mo}$ nuclei using $(^{3}\mathrm{He},\ensuremath{\alpha}\ensuremath{\gamma})$ and $(^{3}\mathrm{He},^{3}\mathrm{He}\ensuremath{'}\ensuremath{\gamma})$ reactions on $^{57}\mathrm{Fe}$ and $^{97}\mathrm{Mo}$ targets. It is shown that statistical spectroscopy provides a useful tool in this mass region. Apparent step structures in the level-density curves are tentatively explained by a schematic microscopic model comprising single-particle level spacings and seniority-conserving and seniority-nonconserving interactions. DA - 2003/11// PY - 2003/11// DO - 10.1103/physrevc.68.054326 VL - 68 IS - 5 SP - SN - 1089-490X ER - TY - JOUR TI - Influence of strain, surface diffusion and Ostwald ripening on the evolution of nanostructures for erbium on Si(001) AU - Fitting, L AU - Zeman, MC AU - Yang, WC AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - This study explores the evolution of nanoscale islands and wire structures during deposition and surface ripening. Ultraviolet photoelectron emission microscopy has been employed to study the real time growth process of individual erbium silicide nanostructures on Si(001) surfaces at temperatures up to 1050 °C. During the initial island formation process compact islands form and some undergo a shape transition to elongated islands oriented along the 〈110〉 directions of the Si substrate. The initial island formation is driven by the surface and interface energies of the silicide/Si structure. The widths of the growing islands remain essentially constant while the lengths increase. The observed elongated islands are ∼150 nm wide, which is larger than the width of prior reported erbium silicide nanowire structures. We propose that the ∼150 nm elongated islands are partially relaxed, possibly through the formation of misfit dislocations. The results indicate a temperature regime where island growth is mainly governed by surface diffusion of the deposited Er adatoms and a higher temperature regime where Ostwald ripening contributes to the island morphology. DA - 2003/4/1/ PY - 2003/4/1/ DO - 10.1063/1.1557787 VL - 93 IS - 7 SP - 4180-4184 SN - 1089-7550 ER - TY - JOUR TI - Fullerene coalescence in nanopeapods: A path to novel tubular carbon AU - Hernandez, E AU - Meunier, V AU - Smith, BW AU - Rurali, R AU - Terrones, H AU - Nardelli, MB AU - Terrones, M AU - Luzzi, DE AU - Charlier, JC T2 - NANO LETTERS AB - A fascinating structural transformation occurring inside single-walled carbon nanotubes (SWNTs) is the fullerene coalescence, which is responsible for forming stable zeppelinlike carbon molecules. We report in situ transmission electron microscope (TEM) observations revealing sequences of fullerene coalescence induced by electron irradiation on pristine nanotube peapods, together with extensive theoretical investigations of the microscopic mechanism underlying this process. TEM images indicate that the merging of fullerenes results in stable but corrugated tubules (5 to 7 Å in diameter) confined within SWNTs. These observations have been confirmed using a combination of theoretical approaches based on molecular dynamics, empirical potentials, tight-binding methods, Monte Carlo techniques, and first principles calculations. We have fully elucidated the coalescence mechanism of fullerenes inside SWNTs under electron irradiation and thermal annealing. The process occurs via the polymerization of C60 molecules followed by surface reconstruction, which can be triggered either by the formation of vacancies (created under electron irradiation) or by surface-energy minimization activated by thermal annealing. These novel tubular forms of carbon contain hexagons, pentagons, heptagons, and octagons. The stability, electronic properties, and electron conductance of the novel tubules are strongly affected by the final geometry of the coalesced fullerene complex. The possibility of forming highly conducting and semiconducting tubular structures suggests new avenues in designing carbon nanowires with specific electronic characteristics. DA - 2003/8// PY - 2003/8// DO - 10.1021/nl034283f VL - 3 IS - 8 SP - 1037-1042 SN - 1530-6992 ER - TY - JOUR TI - Excitation of triply excited Be+ (2lnl ' n ' l '') states in 300 and 500 keV-Be++CH4 collisions AU - Bruch, R AU - Merabet, H AU - Chung, KT T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS AB - We have studied high resolution beryllium Auger electron spectra in the 120–160 eV projectile electron energy range following intermediate energies (1.2 and 1.5 a.u. impact velocities) in Be+ + CH4 ion–molecule single collisions [Comments At. Mol. Phys. D 14 (1984) 117]. The major focus of this study is the double K-shell excitation of the Be+ projectile forming triply excited BeII*** states (hollow atoms) and BeIII** K shell ionization plus excitation of BeII doubly excited states with two inner shell vacancies. In such intermediate velocity ion-molecular collisions, the CH4 target plays an important role in the enhancement of the population of BeII*** triply excited states when compared to a more tightly bound He (1s2) 1S ground state target. Due to the pioneering theoretical work of Gou and Chung [Phys. Rev. A 29 (1996) 6103] most line structures can now be unambiguously identified. The main triply excited states are associated with the 2s22p, 2s2p2 and 2p3 and 2l2l′n′l″ (n=3 and 4) configurations decaying to different final BeIII (1snl) ionic states. The line identification method used here is based on Auger energy levels, decay channels and branching ratios. DA - 2003/5// PY - 2003/5// DO - 10.1016/S0168-583X(02)01937-7 VL - 205 SP - 488-493 SN - 0168-583X KW - triply excited states KW - BeII** KW - BeIII KW - Auger electron level KW - decay channel ER - TY - JOUR TI - Dyson-Schwinger equations: A tool for hadron physics AU - Maris, P AU - Roberts, CD T2 - INTERNATIONAL JOURNAL OF MODERN PHYSICS E AB - Dyson-Schwinger equations furnish a Poincare' covariant framework within which to study hadrons. A particular feature is the existence of a nonperturbative, symmetry preserving truncation that enables the proof of exact results. The gap equation reveals that dynamical chiral symmetry breaking is tied to the long-range behaviour of the strong interaction, which is thereby constrained by observables, and the pion is precisely understood, and seen to exist simultaneously as a Goldstone mode and a bound state of strongly dressed quarks. The systematic error associated with the simplest truncation has been quantified, and it underpins a one-parameter model efficacious in describing an extensive body of mesonic phenomena. Incipient applications to baryons have brought successes and encountered challenges familiar from early studies of mesons, and promise a covariant field theory upon which to base an understanding of contemporary large momentum transfer data. DA - 2003/6// PY - 2003/6// DO - 10.1142/S0218301303001326 VL - 12 IS - 3 SP - 297-365 SN - 1793-6608 KW - Bethe-Salpeter equation KW - confinement KW - dynamical Chiral symmetry breaking KW - Dyson-Schwinger equations KW - electroweak and strong form factors KW - Faddeev equation KW - hadron physics KW - QCD modelling ER - TY - JOUR TI - Chiral symmetry breaking in (2+1) dimensional QED AU - Maris, P. AU - Lee, D. T2 - Nuclear Physics. B, Proceedings, Supplements DA - 2003/// PY - 2003/// DO - 10.1016/S0920-5632(03)01683-9 VL - 119 IS - 2003 May SP - 784-786 ER - TY - JOUR TI - Chandra CCD imagery of the northeast and northwest limbs of SN 1006 AU - Long, KS AU - Reynolds, SP AU - Raymond, JC AU - Winkler, PF AU - Dyer, KK AU - Petre, R T2 - ASTROPHYSICAL JOURNAL AB - We present deep images of the SN 1006 remnant (G327.6+14.6) with the ACIS instrument on the Chandra X-Ray Observatory. Two regions have been observed, the synchrotron-dominated northeast limb and the thermally dominated northwest limb, as well as a substantial portion of the interior of the remnant shell. The brightest features in the X-ray images correspond closely to radio features in the northeast and to Balmer-dominated filaments in the northwest. The spectra of the brighter filaments in the northeast are harder, with less prominent line emission than those in the northwest. In addition to highly elongated filaments, both images show enhanced clumps of emission well inside of the shock front that appear to be dominated by emission from oxygen. These probably arise from shock-heated ejecta, based on analysis of their X-ray spectra. We find no firm evidence for a halo of X-ray emission outside the shock to the northeast, as predicted by the Fermi shock-acceleration picture, in which relativistic electrons should be diffusing ahead of the shock. Our limits on upstream emission are less than 1.5% of the postshock levels in regions where the supernova remnant is brightest. This strongly suggests that the bright rims are flattened sheets nearly perpendicular to the plane of the sky and that the magnetic field strength jumps at the shock by a factor significantly larger than 4, as has been proposed if the shock puts significant energy into accelerating nonthermal ions. The spectra obtained of the northwest rim are all dominated by the helium-like ions of O, Ne, Mg, and Si expected from shocks with ionization (net) parameters of order 100 cm-3 yr and electron temperatures of 0.5-1 keV, far lower than the postshock ion temperature implied by estimates of the shock speed obtained from the shape of the Hα line. DA - 2003/4/1/ PY - 2003/4/1/ DO - 10.1086/367832 VL - 586 IS - 2 SP - 1162-1178 SN - 0004-637X KW - ISM : individual (SN 1006) KW - supernova remnants KW - X-rays : ISM ER - TY - JOUR TI - Application of scanning transmission X-ray microscopy to the rubber industry AU - Winesett, DA AU - Ade, H AU - Smith, AP AU - Urquhart, SG AU - Dias, AJ AU - Stevens, P T2 - RUBBER CHEMISTRY AND TECHNOLOGY AB - Abstract Materials of commercial significance in the rubber industry are usually multi-component systems composed of several elastomers and various fillers. Elucidating the complex morphology that can arise from blending and understanding how this affects the various properties are essential. A technique advantageous to the study of multi-component elastomeric systems is Scanning Transmission X-ray Microscopy (STXM). STXM utilizes the chemical sensitivity of Near Edge X-ray Absorption Fine Structure (NEXAFS) and combines with relatively high spatial resolution and low beam damage to allow the successful characterization of multi-component materials that may be difficult or impossible with other techniques. An overview of the technique and example applications for the rubber industry is presented. DA - 2003/// PY - 2003/// DO - 10.5254/1.3547773 VL - 76 IS - 4 SP - 803-811 SN - 1943-4804 ER - TY - JOUR TI - A free energy model for hysteresis in ferroelectric materials AU - Smith, RC AU - Seelecke, S AU - Ounaies, Z AU - Smith, J T2 - JOURNAL OF INTELLIGENT MATERIAL SYSTEMS AND STRUCTURES AB - This paper provides a theory for quantifying the hysteresis and constitutive nonlinearities inherent to piezoceramic compounds through a combination of free energy analysis and stochastic homogenization techniques. In the first step of the model development, Helmholtz and Gibbs free energy relations are constructed at the lattice or domain level to quantify the relation between the field and polarization in homogeneous, single crystal compounds which exhibit uniform effective fields. The effects of material nonhomogeneities, polycrystallinity, and variable effective fields are subsequently incorporated through the assumption that certain physical parameters, including the local coercive and effective fields, are randomly distributed and hence manifestations of stochastic density functions associated with the material. Stochastic homogenization in this manner provides low-order macroscopic models with effective parameters that can be correlated with physical properties of the data. This facilitates the identification of parameters for model construction, model updating to accommodate changing operating conditions, and control design utilizing model-based inverse compensators. Attributes of the model, including the guaranteed closure of biased minor loops in quasistatic drive regimes, are illustrated through examples. DA - 2003/11// PY - 2003/11// DO - 10.1177/1045389X03038841 VL - 14 IS - 11 SP - 719-739 SN - 1045-389X KW - hysteresis model KW - ferroelectric materials KW - piezoceramic compounds ER - TY - JOUR TI - A new approach for calculating the electronic structure and vibrational properties of non-crystalline solids: Effective charges for infrared-active normal mode vibrations in oxide and chalcogenide materials AU - Lucovsky, G. AU - Sremaniak, L. S. AU - Mowrer, T. AU - Whitten, J. L. T2 - Journal of Non-crystalline Solids DA - 2003/// PY - 2003/// VL - 326 IS - 2003 Oct 1 SP - 14- ER - TY - JOUR TI - Thermal X-ray emission from shocked ejecta in type Ia supernova remnants: Prospects for explosion mechanism identification AU - Badenes, C AU - Bravo, E AU - Borkowski, KJ AU - Dominquez, I T2 - ASTROPHYSICAL JOURNAL AB - The explosion mechanism behind Type Ia supernovae is a matter of continuing debate. The diverse attempts to identify or at least constrain the physical processes involved in the explosion have been only partially successful so far. In this paper we propose to use the thermal X-ray emission from young supernova remnants originated in Type Ia events to extract relevant information concerning the explosions themselves. We have produced a grid of thermonuclear supernova models representative of the paradigms currently under debate: pure deflagrations, delayed detonations, pulsating delayed detonations and sub-Chandrasekhar explosions, using their density and chemical composition profiles to simulate the interaction with the surrounding ambient medium and the ensuing plasma heating, non-equilibrium ionization and thermal X-ray emission of the ejecta. Key observational parameters such as electron temperatures, emission measures and ionization time scales are presented and discussed. We find that not only is it possible to identify the explosion mechanism from the spectra of young Type Ia Supernova Remnants, it is in fact necessary to take the detailed ejecta structure into account if such spectra are to be modeled in a self-consistent way. Neither element line flux ratios nor element emission measures are good estimates of the true ratios of ejected masses, with differences of as much as two or three orders of magnitude for a given model. Comparison with observations of the Tycho SNR suggests a delayed detonation as the most probable explosion mechanism. Line strengths, line ratios, and the centroid of the Fe Kalpha line are reasonably well reproduced by a model of this kind. DA - 2003/8/10/ PY - 2003/8/10/ DO - 10.1086/376448 VL - 593 IS - 1 SP - 358-369 SN - 1538-4357 KW - hydrodynamics KW - ISM : individual (SN 1572) KW - nuclear reactions, nucleosynthesis, abundances KW - supernova remnants KW - supernovae : general KW - X-rays : ISM ER - TY - JOUR TI - The effects of probe boundary conditions and propagation on nano-Raman spectroscopy AU - Hallen, HD AU - Ayars, EJ AU - Jahncke, CL T2 - JOURNAL OF MICROSCOPY-OXFORD AB - Raman spectra obtained in the near-field, with collection of the Raman-shifted light in reflection, show selective enhancement of vibrational modes. We show that the boundary conditions for an electric field near a metal surface affect propagation of the reflected signal and lead to this selection. The enhancement of certain Raman forbidden vibrations is explained by the presence of an electric field gradient near the metal-apertured fibre probe. DA - 2003/6// PY - 2003/6// DO - 10.1046/j.1365-2818.2003.01138.x VL - 210 IS - 3 SP - 252-254 SN - 0022-2720 UR - http://dx.doi.org/10.1046/j.1365-2818.2003.01138.x KW - boundary conditions near a metal KW - electric field enhancement KW - gradient-field Raman KW - KTP KW - light propagation in the near-field KW - nano-Raman KW - near-field Raman spectroscopy KW - near-field scanning optical microscopy KW - resolution ER - TY - JOUR TI - Spectroscopic study of chemical phase separation in zirconium silicate alloys AU - Rayner, G. B. AU - Kang, D. AU - Lucovsky, G. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 2003/// PY - 2003/// VL - 21 IS - 4 SP - 1783-1791 ER - TY - JOUR TI - Soft x-ray photoelectron spectroscopy of (HfO2)(x)(SiO2)(1-x) high-k gate-dielectric structures AU - Ulrich, M. D. AU - Hong, J. G. AU - Rowe, J. E. AU - Lucovsky, G. AU - Chan, A. S. Y. AU - Madey, T. E. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 2003/// PY - 2003/// VL - 21 IS - 4 SP - 1777-1782 ER - TY - JOUR TI - Scanning transmission X-ray microscopy at a bending magnet beamline at the Advanced Light Source AU - Ade, H AU - Kilcoyne, ALD AU - Tyliszczak, T AU - Hitchcock, P AU - Anderson, E AU - Harteneck, B AU - Rightor, EG AU - Mitchell, GE AU - Hitchcock, AP AU - Warwick, T T2 - JOURNAL DE PHYSIQUE IV AB - During the last two decades, scanning transmission x-ray microscopy (STXM) has evolved into a powerful characterization tool. For best performance, STXM's are located at undulator sources at synchrotron facilities. The scarcity and expense of undulator sources and associated heamlines limits the number of available STXMs. We have successfully re-examined the use of bending magnets as a source for a STXM and implemented a interferometer controlled STXM with excellent performance at the beamline 5.3,2, at the Advanced Light Source Near the carbon K-edge, periodic features with 30 nm half-period could be resolved with a zone plate that has a 40 nm outermost zone width with an energy resolution corresponding to 100 meV and an intensity of about 1 MHz The design and perforormance of the microscope are described. DA - 2003/3// PY - 2003/3// DO - 10.1051/jp4:200300017 VL - 104 IS - 2003 Mar SP - 3-8 SN - 1155-4339 ER - TY - JOUR TI - Nonlinear regimes of coherent optical phonon generation in quantum wells under electric current pumping AU - Komirenko, SM AU - Kim, KW AU - Kochelap, VA AU - Koroteev, , VV AU - Stroscio, MA T2 - PHYSICAL REVIEW B AB - We present an analysis of nonlinear regimes of the coherent optical phonon generation under the electron drift in quantum wells. The phonon and electron subsystems are treated self-consistently. This allows us to find the steady-state generation regimes with macroscopic populations of optical phonon modes and the electron transport controlled in part by the generated phonons. The generation regimes demonstrate a pronounced threshold character. At high electric fields above the threshold, practically single-mode generation occurs and the current-voltage characteristic is considerably changed. We demonstrate high efficiency generation of the coherent optical phonons by the electric current. The coherent macroscopic optical displacements and the amplitudes of oscillating electrostatic fields are evaluated. The proposed model based on the electron nonlinearities predicts a range of the pumping electric fields under which the steady state phonon generation is realized. Our results suggest that the phonon avalanche occurs beyond this field range. DA - 2003/10/15/ PY - 2003/10/15/ DO - 10.1103/physrevb.68.155308 VL - 68 IS - 15 SP - SN - 2469-9969 ER - TY - JOUR TI - Micro-Raman study of electronic properties of inversion domains in GaN-based lateral polarity heterostructures AU - Park, M AU - Cuomo, JJ AU - Rodriguez, BJ AU - Yang, WC AU - Nemanich, RJ AU - Ambacher, O T2 - JOURNAL OF APPLIED PHYSICS AB - The electronic properties of inversion domains in a GaN-based lateral polarity heterostructure were investigated using micro-Raman spectroscopy. The piezoelectric polarization of each domain was calculated from strain determined via Raman scattering. The free carrier concentration and electron mobility were deduced from the longitudinal optical phonon–plasmon coupled mode. The electron concentration in the N-face domain was slightly higher than that in the Ga-face domain. It appears that during growth, a larger number of donor impurities may have been incorporated into the N-face domain than into the Ga-face domain. DA - 2003/6/15/ PY - 2003/6/15/ DO - 10.1063/1.1570507 VL - 93 IS - 12 SP - 9542-9547 SN - 1089-7550 ER - TY - JOUR TI - Ladder Dyson-Schwinger calculation of the anomalous gamma-3 pi form factor AU - Cotanch, , SR AU - Maris, P T2 - PHYSICAL REVIEW D AB - The anomalous processes $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}}3\ensuremath{\pi}$ and $\ensuremath{\gamma}\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\pi}}\ensuremath{\pi}\ensuremath{\pi}$ are investigated within the Dyson-Schwinger framework using the rainbow-ladder approximation. Calculations reveal that a complete set of ladder diagrams beyond the impulse approximation are necessary to reproduce the fundamental low-energy theorem for the anomalous form factor. Higher momentum calculations also agree with the limited form factor data and exhibit the same resonance behavior as the phenomenological vector meson dominance model. DA - 2003/8/1/ PY - 2003/8/1/ DO - 10.1103/physrevd.68.036006 VL - 68 IS - 3 SP - SN - 2470-0029 ER - TY - JOUR TI - First results from KamLAND: evidence for reactor antineutrino disappearance AU - Eguchi, K. AU - Enomoto, S. AU - Furuno, K. AU - Goldman, J. AU - Hanada, H. AU - Ikeda, H. AU - Ikeda, K. AU - Inoue, K. AU - Ishihara, K. AU - Itoh, W. AU - Iwamoto, T. AU - Kawaguchi, T. AU - Kawashima, T. AU - Kinoshita, H. AU - Kishimoto, Y. AU - Koga, M. AU - Koseki, Y. AU - Maeda, T. AU - Mitsui, T. AU - Motoki, M. AU - Nakajima, K. AU - Nakajima, M. AU - Nakajima, T. AU - Ogawa, H. AU - Owada, K. AU - Sakabe, T. AU - Shimizu, I. AU - Shirai, J. AU - Suekane, F. AU - Suzuki, A. AU - Tada, K. AU - Tajima, O. AU - Takayama, T. AU - Tamae, K. AU - Watanabe, H. AU - Busenitz, J. AU - Djurcic, Z. AU - McKinny, K. AU - Mei, D.-M. AU - Piepke, A. AU - Yakushev, E. AU - Berger, B.E. AU - Chan, Y.D. AU - Decowski, M.P. AU - Dwyer, D.A. AU - Freedman, S.J. AU - Fu, Y. AU - Fujikawa, B.K. AU - Heeger, K.M. AU - Lesko, K.T. AU - Luk, K.-B. AU - Murayama, H. AU - Nygren, D.R. AU - Okada, C.E. AU - Poon, A.W.P. AU - Steiner, H.M. AU - Winslow, L.A. AU - Horton-Smith, G.A. AU - McKeown, R.D. AU - Ritter, J. AU - Tipton, B. AU - Vogel, P. AU - Lane, C.E. AU - Miletic, T. AU - Gorham, P.W. AU - Guillian, G. AU - Learned, J.G. AU - Maricic, J. AU - Matsuno, S. AU - Pakvasa, S. AU - Dazeley, S. AU - Hatakeyama, S. AU - Murakami, M. AU - Svoboda, R.C. AU - Dieterle, B.D. AU - DiMauro, M. AU - Detwiler, J. AU - Gratta, G. AU - Ishii, K. AU - Tolich, N. AU - Uchida, Y. AU - Batygov, M. AU - Bugg, W. AU - Cohn, H. AU - Efremenko, Y. AU - Kamyshkov, Y. AU - Kozlov, A. AU - Nakamura, Y. AU - De Braeckeleer, L AU - Gould, C.R. AU - Karwowski, H.J. AU - Markoff, D.M. AU - Messimore, J.A. AU - Nakamura, K. AU - Rohm, R.M. AU - Tonow, W. AU - Young, A.R. AU - Wang, Y.-F. T2 - Physical Review Letters AB - KamLAND has measured the flux of nu;(e)'s from distant nuclear reactors. We find fewer nu;(e) events than expected from standard assumptions about nu;(e) propagation at the 99.95% C.L. In a 162 ton.yr exposure the ratio of the observed inverse beta-decay events to the expected number without nu;(e) disappearance is 0.611+/-0.085(stat)+/-0.041(syst) for nu;(e) energies >3.4 MeV. In the context of two-flavor neutrino oscillations with CPT invariance, all solutions to the solar neutrino problem except for the "large mixing angle" region are excluded. DA - 2003/// PY - 2003/// DO - 10.1103/PhysRevLett.90.021802 VL - 90 IS - 2 SP - 021802 ER - TY - JOUR TI - Electronic structure and ground states of transition metals encapsulated in a Si-12 hexagonal prism cage AU - Sen, P AU - Mitas, L T2 - PHYSICAL REVIEW B AB - We report on a computational study of the electronic structure of recently discovered clusters with an encapsulated transition metal (TM) atom in a ${\mathrm{Si}}_{12}$ hexagonal prism cage. The cage geometry is remarkably stable regardless of the type of doping TM atom from $3d,4d,$ and $5d$ series. We predict and quantify the stability for several other TM dopings besides the experimentally observed ones. The multiplicity of the ground states can be ``tuned'' between singlets and triplets by varying the type of TM atom (even number of electrons), while they are doublets for odd number of electrons. We also explore the possibility of forming solids with hexagonal structure from selected clusters. DA - 2003/10/15/ PY - 2003/10/15/ DO - 10.1103/physrevb.68.155404 VL - 68 IS - 15 SP - SN - 2469-9969 ER - TY - JOUR TI - Ejecta detection in middle-aged large magellanic cloud supernova remnants 0548-70.4 and 0534-69.9 AU - Hendrick, SP AU - Borkowski, KJ AU - Reynolds, SP T2 - ASTROPHYSICAL JOURNAL AB - We have observed supernova remnants 0548-70.4 and 0534-69.9 in the Large Magellanic Cloud (LMC) with the Chandra X-Ray Observatory and report on the X-ray spectral analysis. Our images of 0548-70.4 and 0534-69.9 show bright central regions as well as brightened limbs. The X-ray spectra from the central regions exhibit enhanced metal abundances, in significant contrast to limb spectra, which show abundances consistent with the LMC interstellar medium (ISM). Considering the relatively old ages (~10,000 yr), these supernova remnants might be assumed to be in the Sedov phase, in which the X-ray spectra would be dominated by swept-up ISM material. The detection of high abundances in these old remnants is therefore surprising. Spectra from the limb regions were analyzed with Sedov models. The results were then used to account for blast wave emission seen in projection toward the central region and were added to a plane-parallel shock model for the reverse shock in the ejecta. We find elevated levels of iron, oxygen, magnesium, silicon, and sulfur in the bright central regions of each remnant. We introduce a new X-ray spectral shock model appropriate for heavy-element-dominated plasmas, in which electrons liberated by successive ionizations dominate the electron pool and modify the electron temperature profile. With this model, we find reverse-shock speeds of 420 km s-1 for 0548-70.4, 500 km s-1 for the northeast central region of 0534-69.9, and 360 km s-1 for its south central region. The elemental abundances favor a Type Ia supernova origin for both 0548-70.4 and 0534-69.9. DA - 2003/8/10/ PY - 2003/8/10/ DO - 10.1086/376356 VL - 593 IS - 1 SP - 370-376 SN - 0004-637X KW - ISM : individual (SNR 0534-69.9 KW - SNR 0548-70.4) KW - Magellanic Clouds KW - shock waves KW - supernova remnants KW - X-rays : general ER - TY - JOUR TI - Bonding and structure of ultrathin yttrium oxide films for Si field effect transistor gate dielectric applications AU - Ulrich, MD AU - Rowe, JE AU - Niu, D AU - Parsons, GN T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - Soft x-ray photoelectron spectroscopy using synchrotron radiation has been employed to study the interface between Y2O3 films and Si(100). Y2O3 films of ∼8, ∼15, and 65 Å were formed by plasma assisted chemical vapor deposition on HF-last Si(100). With this deposition technique, SiO2 forms at the interface and a kinetically limited silicate layer forms between the resulting SiO2 deposited Y2O3. For 65 Å films, the Y 3d5/2 binding energy was between 158.8 and 159.0 eV, 2.2–2.4 eV higher than the reported value of 156.6 eV for Y2O3. For 8 and 15 Å films, the Y 3d5/2 binding energies were 159.6 and 158.9 eV, respectively. The relatively high binding energies are attributed to hydroxide incorporation in the film. For the ultrathin films, ∼10 Å of SiO2 was formed at the interface during or after the deposition. For the 8 Å film, no silicate is detectable whereas for the 15 Å film, an estimated 4 Å of silicate is present between the interfacial SiO2 and Y2O3 overlayer. Because this transition layer does not form in the 8 Å film, it is concluded that the mixing is kinetically limited. For the 8 Å film, the Si 2p3/2 [SiO2] binding energy was 3.65 eV relative to the substrate peak. For the 15 Å deposition, the Si 2p3/2 [SiO2] binding energy was 3.44 eV and the Si 2p3/2 [silicate] binding energy was 2.65 eV relative to the substrate peak. DA - 2003/// PY - 2003/// DO - 10.1116/1.1593647 VL - 21 IS - 4 SP - 1792-1797 SN - 1071-1023 ER - TY - PAT TI - Binary non-crystalline oxide analogs of silicon dioxide for use in gate dielectrics AU - Lucovsky, G. C2 - 2003/// DA - 2003/// PY - 2003/// ER - TY - JOUR TI - Application of the simplified bond-hyperpolarizability model to fourth-harmonic generation AU - Hansen, JK AU - Peng, HJ AU - Aspnes, DE T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - We show that the simplified bond-hyperpolarizability model (SBHM), previously used to accurately describe anisotropies observed in second-harmonic generation from Si–dielectric interfaces, also describes anisotropies observed in fourth-harmonic generation (FHG). FHG data from (001)Si–SiO2 interfaces show two contributions: one from the intrinsic response of the interface bonds and the second from roughness. SBHM calculations yield excellent agreement with scaled ps and ss polarization data and the phases of the pp and sp equivalents with no adjustable parameters. The SHBM also precisely reproduces the anisotropy data for samples with systematic variations of interface roughness, and predicts relative amplitudes consistent with measured fields to factors of about 2. DA - 2003/// PY - 2003/// DO - 10.1116/1.1593057 VL - 21 IS - 4 SP - 1798-1803 SN - 1071-1023 ER - TY - JOUR TI - Strong decays of light vector mesons AU - Jarecke, D. AU - Maris, P. AU - Tandy, P. C. T2 - Physical Review. C, Nuclear Physics DA - 2003/// PY - 2003/// VL - 67 IS - 3 SP - 035202-1 ER - TY - JOUR TI - Photoelectron emission microscopy observation of inversion domain boundaries of GaN-based lateral polarity heterostructures AU - Yang, W. C. AU - Rodriguez, B. J. AU - Park, M. AU - Nemanich, R. J. AU - Ambacher, O. AU - Cimalla, V. T2 - Journal of Applied Physics AB - An intentionally grown GaN film with laterally patterned Ga- and N-face polarities is studied using in situ UV-photoelectron emission microscopy (PEEM). Before chemical vapor cleaning of the surface, the emission contrast between the Ga- and N-face polarities regions was not significant. However, after cleaning the emission contrast between the different polarity regions was enhanced such that the N-face regions exhibited increased emission over the Ga-face regions. The results indicate that the emission threshold of the N-face region is lower than that of the Ga face. Moreover, bright emission was detected from regions around the inversion domain boundaries of the lateral polarity heterostructure. The PEEM polarity contrast and intense emission from the inversion domain boundary regions are discussed in terms of the built-in lateral field and the surface band bending induced by the polarization bound surface charges. DA - 2003/// PY - 2003/// DO - 10.1063/1.1618355 VL - 94 IS - 9 SP - 5720-5725 ER - TY - JOUR TI - Low-energy photodisintegration of the deuteron and Big-Bang nucleosynthesis AU - Tornow, W. AU - Czakon, N. G. AU - Howell, C. R. AU - Hutcheson, A. AU - Kelley, J. H. AU - Litvinenko, V. N. AU - Mikhailov, S. F. AU - Pinayev, I. V. AU - Weisel, G. J. AU - Witala, H. T2 - Physics Letters. B DA - 2003/// PY - 2003/// VL - 574 IS - 02-Jan SP - 13- ER - TY - JOUR TI - Heteroepitaxial copper phthalocyanine on Au(001) studied by high-resolution X-ray photoelectron spectroscopy AU - Park, KT AU - Miller, A AU - Klier, K AU - Opila, RL AU - Rowe, JE T2 - SURFACE SCIENCE AB - We report the formation of heteroepitaxial copper phthalocyanine (CuPc) thin film grown on a reconstructed Au(0 0 1) surface and the high-resolution X-ray photoelectron spectroscopy study thereof. The deposition of CuPc onto the “5 × 20” reconstructed Au(0 0 1) surface at room temperature results in a well-ordered CuPc overlayer. The angle-resolved XPS data reveal that adsorbed CuPc is molecular and stoichiometric. The low energy electron diffraction (LEED) further shows that the overlayer is incommensurate to the substrate with its square unit mesh measured approximately 12.7 Å by 12.7 Å along 〈110〉 and 〈11̄0〉 of the substrate. From the combined XPS and LEED data, a model of one flat-lying CuPc molecule per unit cell, which is different from the structures of the well-known α- and β-polymorphs, is proposed. DA - 2003/4/10/ PY - 2003/4/10/ DO - 10.1016/S0039-6028(03)00274-7 VL - 529 IS - 3 SP - L285-L292 SN - 1879-2758 KW - X-ray photoelectron spectroscopy KW - angle resolved photoemission KW - molecular beam epitaxy KW - low energy electron diffraction (LEED) KW - gold KW - aromatics KW - single crystal epitaxy KW - semiconducting films ER - TY - JOUR TI - Attractive migration and coalescence: A significant process in the coarsening of TiSi2 islands on the Si(111) surface AU - Yang, WC AU - Zeman, M AU - Ade, H AU - Nemanich, RJ T2 - PHYSICAL REVIEW LETTERS AB - The dynamics and coarsening of TiSi2 islands on Si(111) surfaces are studied in real time with photoelectron emission microscopy. A significant fraction of events are observed in which nearby islands move attractively toward each other and subsequently coalesce. It is proposed that attractive island migration is due to the growth-decay flow of the island edges driven by a nonuniform surface concentration around the islands. The local surface concentration is induced by the neighboring islands. This coarsening mechanism should significantly affect the evolution of the island distribution. DA - 2003/4/4/ PY - 2003/4/4/ DO - 10.1103/physrevlett.90.136102 VL - 90 IS - 13 SP - SN - 0031-9007 ER - TY - JOUR TI - An efficient method to compute partial atomic charges of large molecules using reassociation of fragments AU - Lee, J. G. AU - Jeong, H. Y. AU - Lee, H. T2 - Bulletin of the Korean Chemical Society DA - 2003/// PY - 2003/// VL - 24 IS - 3 SP - 369-376 ER - TY - JOUR TI - Ultrathin PD and PT films on W(211) AU - Block, J. AU - Kolodziej, J. J. AU - Rowe, J. E. AU - Madey, T. E. AU - Schroder, E. T2 - Thin Solid Films DA - 2003/// PY - 2003/// DO - 10.1016/S0040-690(02)01260-9 VL - 440 IS - 02-Jan SP - 293 ER - TY - JOUR TI - Transition form factors between pseudoscalar and vector mesons 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 - 2003/// PY - 2003/// VL - 67 IS - 11 SP - 113007-1 ER - TY - JOUR TI - Spontaneous polarization and piezoelectricity in boron nitride nanotubes AU - Nakhmanson, SM AU - Calzolari, A AU - Meunier, V AU - Bernholc, J AU - Nardelli, MB T2 - PHYSICAL REVIEW B AB - Ab initio calculations of the spontaneous polarization and piezoelectric properties of boron nitride nanotubes show that they are excellent piezoelectric systems with response values larger than those of piezoelectric polymers. The intrinsic chiral symmetry of the nanotubes induces an exact cancellation of the total spontaneous polarization in ideal, isolated nanotubes of arbitrary indices. Breaking of this symmetry by inter-tube interaction or elastic deformations induces spontaneous polarization comparable to those of wurtzite semiconductors. DA - 2003/6/15/ PY - 2003/6/15/ DO - 10.1103/physrevb.67.235406 VL - 67 IS - 23 SP - SN - 1098-0121 ER - TY - JOUR TI - Quantitative method of image analysis when drift is present in a scanning probe microscope AU - Huerth, S.H. AU - Hallen, Hans T2 - Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures AB - We present a quantitative method of image analysis that automatically corrects for system drift in comparisons of images before and after an event under study. The method utilizes two-dimensional correlations followed by automatic z scaling, shifting, and the calculation of a difference image from the before and after images. Optical reflectance near-field scanning optical microscope (NSOM) images that show the effects of oxygen electromigration are used as an example system. The tunnel current that induces the atomic motion is provided by the metallic NSOM aperture in a scanning tunneling microscope mode. The analyzed (difference) image clearly shows the effects that are otherwise obscured by native oxygen concentration variations, demonstrating the utility of the method. The related issues of false positive/negative probabilities for given noise levels and thresholds are also discussed. DA - 2003/// PY - 2003/// DO - 10.1116/1.1553972 VL - 21 IS - 2 SP - 714 - 718 UR - http://dx.doi.org/10.1116/1.1553972 ER - TY - JOUR TI - Preparation and characterization of atomically clean, stoichiometric surfaces of n- and p-type GaN(0001) AU - Tracy, KM AU - Mecouch, WJ AU - Davis, RF AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - It is demonstrated that in situ exposure of the (0001) surface of n- and p-type GaN thin films to flowing ammonia at 860 °C and 10−4 Torr removes hydrocarbon and oxygen/hydroxide species below the detectable limits of x-ray and ultraviolet photoelectron spectroscopies (UPS) and decreases the Ga/N ratio from 1.3 to 1.0. Additional indications of the efficacy of this ammonia-based chemical vapor cleaning (CVC) process were the shifts in the Ga 3d and the N 1s core level positions from the as-loaded to the CVC surfaces of the n-type samples from 21.0±0.1 to 20.6±0.1 eV and from 398.3±0.1 to 398.0±0.1 eV, respectively, and the change in the UPS measured low energy spectrum turn on from 3.9±0.1 (as-loaded samples) to 3.0±0.1 eV (cleaned samples) below the Fermi level. Analogous changes in the p-type samples were from 19.6±0.1 to 18.9±0.1 eV and from 397.1±0.1 to 396.3±0.1 eV for the Ga 3d and the N 1s core levels, and from 3.0±0.1 to 1.1±0.1 eV for the UPS valence band maximum (VBM). The VBM values of the CVC samples indicate band bending of ∼0.3 eV upward on n type and ∼0.8 eV downward on p type. Electron affinities of 2.8±0.1 and 2.6±0.1 eV were determined for the clean n-type and p-type surfaces, respectively. Irrespective of doping, the CVC process left unchanged the (1×1) low energy diffraction pattern, the terraced microstructure, and the root mean square roughness observed for the surfaces of the as-loaded samples, i.e., the surface microstructure was not damaged during the high temperature exposure to ammonia at low pressure. DA - 2003/9/1/ PY - 2003/9/1/ DO - 10.1063/1.1596369 VL - 94 IS - 5 SP - 3163-3172 SN - 1089-7550 ER - TY - JOUR TI - Numerical study of anharmonic vibrational decay in amorphous and paracrystalline silicon AU - Fabian, J. AU - Feldman, J. L. AU - Hellberg, C. S. AU - Nakhmanson, S. M. T2 - Physical Review. B, Condensed Matter and Materials Physics DA - 2003/// PY - 2003/// VL - 67 IS - 22 SP - 224302-1 ER - TY - JOUR TI - Electron emission from diamond nanoparticles on metal tips AU - Tyler, T AU - Zhirnov, , VV AU - Kvit, AV AU - Kang, D AU - Hren, JJ T2 - APPLIED PHYSICS LETTERS AB - Single-crystalline diamond nanoparticles (∼5 nm in scale) have been deposited onto molybdenum needles (with radii &lt;100 nm), and their effects on field emission behavior were measured. Combined transmission electron microscopy observations, field emission measurements, and diamond depositions allowed for direct comparison of the effects of various amounts of nanodiamond coating on the field emission properties of a coated metal field emitter. In the limit, field emission from a single isolated diamond nanoparticle is compared here with that from an uncoated metal emitter and from a coating comprised of several layers of nanoparticles. DA - 2003/4/28/ PY - 2003/4/28/ DO - 10.1063/1.1570498 VL - 82 IS - 17 SP - 2904-2906 SN - 0003-6951 ER - TY - JOUR TI - Effective number of neutrinos and baryon asymmetry from BBN and WMAP AU - Barger, V. AU - Kneller, J. P. AU - Lee, H. S. AU - Marfatia, D. AU - Steigman, G. T2 - Physics Letters. B DA - 2003/// PY - 2003/// VL - 566 IS - 02-Jan SP - 18- ER - TY - JOUR TI - Band offset measurements of the GaN (0001)/HfO2 interface AU - Cook, T. E. AU - Fulton, C. C. AU - Mecouch, W. J. AU - Davis, R. F. AU - Lucovsky, G. AU - Nemanich, R. J. T2 - Journal of Applied Physics DA - 2003/// PY - 2003/// DO - 10.1063/1.1618374 VL - 94 IS - 11 SP - 7155-7158 ER - TY - JOUR TI - Angular conditions, relations between the Breit and light-front frames, and subleading power corrections AU - Carlson, C. E. AU - Ji, C. R. T2 - Physical Review. D, Particles and Fields DA - 2003/// PY - 2003/// VL - 67 IS - 11 SP - 116002-1 ER - TY - JOUR TI - Towards a detailed understanding of the NEXAFS spectra of bulk polyethylene copolymers and related alkanes AU - Scholl, A AU - Fink, R AU - Umbach, E AU - Mitchell, GE AU - Urquhart, SG AU - Ade, H T2 - CHEMICAL PHYSICS LETTERS AB - High energy resolution C 1s near-edge X-ray absorption fine structure (NEXAFS) spectra of ethylene-1-alkene copolymers with systematic variations in comonomer content and thus systematic changes in branch length, branching ratio, and degree of crystallinity are presented. Spectral changes of the σ*C–H/Rydberg and σ*C–C features in these ideal model systems provide unambiguous experimental evidence for intermolecular interactions with profound effects on the spectral intensity, but only very small energy shifts. Ab initio calculations reproduce the experimental results in detail. The intermolecular interaction observed suggests that interpretation of NEXAFS spectra based on calculations of isolated molecules can be insufficient even in relatively weakly interacting macromolecules. DA - 2003/3/21/ PY - 2003/3/21/ DO - 10.1016/S0009-2614(03)00215-X VL - 370 IS - 5-6 SP - 834-841 SN - 0009-2614 ER - TY - JOUR TI - Surface morphology of annealed polystyrene and poly(methyl methacrylate) thin film blends and bilayers AU - Harris, M AU - Appel, G AU - Ade, H T2 - MACROMOLECULES AB - Thin films of polystyrene (PS) and poly(methyl methacrylate) (PMMA) were spun-cast onto silicon substrates, annealed, and analyzed by atomic force microscopy (AFM), total electron yield (TEY), and partial electron yield (PEY) near-edge X-ray absorption fine structure (NEXAFS) spectroscopy in order to resolve conflicting prior literature regarding the tendency of PS to form a wetting layer or overlayer on top of PMMA. From the comparison of the three methods of analysis and on the basis of the extraordinary surface sensitivity of PEY NEXAFS, we conclude that PS does not form an overlayer in samples with morphologies near thermodynamic equilibrium. The PS forms droplets of a large size range on top of a PMMA layer that wets the hydrophilic SiOx substrate. From our results, the maximum thickness of a continuous PS wetting layer would be about 0.25 nm. This is in contrast to recent experiments that imply an equivalent PS wetting layer of about 5−10 nm is forming during annealing. DA - 2003/5/6/ PY - 2003/5/6/ DO - 10.1021/ma0257043 VL - 36 IS - 9 SP - 3307-3314 SN - 0024-9297 ER - TY - JOUR TI - Spatial inhomogeneity of imprint and switching behavior in ferroelectric capacitors AU - Gruverman, A AU - Rodriguez, BJ AU - Kingon, AI AU - Nemanich, RJ AU - Cross, JS AU - Tsukada, M T2 - APPLIED PHYSICS LETTERS AB - Piezoresponse force microscopy has been used to perform nanoscale characterization of the spatial variations in the imprint and switching behavior of (111)-oriented Pb(Zr,Ti)O3-based capacitors on Pt electrodes. Mapping of polarization distribution in the poled capacitors as well as local d33–V loop measurements revealed a significant difference in imprint and switching behavior between the peripheral and inner parts of the capacitors. It has been found that the inner regions of the capacitors are negatively imprinted (with the preferential direction of the normal component of polarization upward) and tend to switch back after application of the positive poling voltage. On the other hand, switchable regions at the edge of the integrated capacitors generally exhibit more symmetric hysteresis behavior. Application of an ac switching voltage, contrary to what was expected, resulted in an increase of the negatively imprinted regions. The observed effect has been explained by incomplete or asymmetric switching due to the mechanical stress conditions existing in the central parts of the capacitors. DA - 2003/5/5/ PY - 2003/5/5/ DO - 10.1063/1.1570942 VL - 82 IS - 18 SP - 3071-3073 SN - 0003-6951 ER - TY - JOUR TI - Spatial distribution of electron emission sites for sulfur doped and intrinsic nanocrystalline diamond films AU - Kock, FAM AU - Garguilo, JM AU - Nemanich, RJ AU - Gupta, S AU - Weiner, BR AU - Morell, G T2 - DIAMOND AND RELATED MATERIALS AB - We have investigated high sp2 content intrinsic and sulfur doped nanocrystalline diamond films to study field emission properties by electron emission microscopy operated in different modes. Electron emission microscopy enables real time imaging of the electron emission from a surface with a lateral resolution of ∼15 nm. The nanocrystalline intrinsic diamond films exhibit electron emission at room temperature from localized emission sites with weak temperature dependence, and a density of ∼103–104/cm2. In contrast, sulfur doped diamond films show similar emission characteristics at room temperature, but at elevated temperatures the emission significantly increases from the localized regions and a thermionic component is identified in the I/V dependence. We discuss the role of S-donor states to explain the enhanced emission of the S-doped nanocrystalline diamond. DA - 2003/// PY - 2003/// DO - 10.1016/S0925-9635(02)00365-5 VL - 12 IS - 3-7 SP - 474-480 SN - 1879-0062 KW - nanocrystalline KW - plasma CVD KW - field emission ER - TY - JOUR TI - Orientation studies of Si-phthalocyanine sulfonic acids cast on SiOx substrates AU - Appel, G AU - Ade, H AU - Guerek, AG AU - Stadler, S AU - Mikalo, RP AU - Schmeisser, D T2 - APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING DA - 2003/2// PY - 2003/2// DO - 10.1007/s003390201320 VL - 76 IS - 2 SP - 177-182 SN - 1432-0630 ER - TY - JOUR TI - Interferometer-controlled scanning transmission X-ray microscopes at the Advanced Light Source AU - Kilcoyne, ALD AU - Tyliszczak, T AU - Steele, WF AU - Fakra, S AU - Hitchcock, P AU - Franck, K AU - Anderson, E AU - Harteneck, B AU - Rightor, EG AU - Mitchell, GE AU - Hitchcock, AP AU - Yang, L AU - Warwick, T AU - Ade, H T2 - JOURNAL OF SYNCHROTRON RADIATION AB - Two new soft X-ray scanning transmission microscopes located at the Advanced Light Source (ALS) have been designed, built and commissioned. Interferometer control implemented in both microscopes allows the precise measurement of the transverse position of the zone plate relative to the sample. Long-term positional stability and compensation for transverse displacement during translations of the zone plate have been achieved. The interferometer also provides low-distortion orthogonal x, y imaging. Two different control systems have been developed: a digital control system using standard VXI components at beamline 7.0, and a custom feedback system based on PC AT boards at beamline 5.3.2. Both microscopes are diffraction limited with the resolution set by the quality of the zone plates. Periodic features with 30 nm half period can be resolved with a zone plate that has a 40 nm outermost zone width. One microscope is operating at an undulator beamline (7.0), while the other is operating at a novel dedicated bending-magnet beamline (5.3.2), which is designed specifically to illuminate the microscope. The undulator beamline provides count rates of the order of tens of MHz at high-energy resolution with photon energies of up to about 1000 eV. Although the brightness of a bending-magnet source is about four orders of magnitude smaller than that of an undulator source, photon statistics limited operation with intensities in excess of 3 MHz has been achieved at high energy resolution and high spatial resolution. The design and performance of these microscopes are described. DA - 2003/3// PY - 2003/3// DO - 10.1107/S0909049502017739 VL - 10 IS - 2003 Mar SP - 125-136 SN - 1600-5775 KW - X-rays KW - zone plates KW - scanning microscopy KW - NEXAFS ER - TY - JOUR TI - High-pressure phase transformation of silicon nitride AU - Patten, J AU - Fesperman, R AU - Kumar, S AU - McSpadden, S AU - Qu, J AU - Lance, M AU - Nemanich, R AU - Huening, J T2 - APPLIED PHYSICS LETTERS AB - We provide evidence for a high-pressure phase transformation (HPPT) in the ceramic material silicon nitride. This HPPT is inferred by a high-pressure diamond anvil cell, Raman spectroscopy, scanning/transmission electron microscopy, and optical and acoustic microscope inspection. In the case of silicon nitride, the HPPT involves a ductile or metallike behavior that is observed in severe deformation processes, such as nanoindentation and micromachining. This pressure-induced plasticity is believed to be similar to that found in silicon and germanium with its origin in the high-pressure metallic β-Sn phase formation. DA - 2003/12/8/ PY - 2003/12/8/ DO - 10.1063/1.1632031 VL - 83 IS - 23 SP - 4740-4742 SN - 0003-6951 ER - TY - JOUR TI - High resolution photoemission study of growth, alloying, and intermixing of ultrathin ruthenium films on W(111) and W(211) AU - Gladys, MJ AU - Jackson, G AU - Rowe, JE AU - Madey, TE T2 - SURFACE SCIENCE AB - The alloying, intermixing, growth and faceting of ruthenium overlayers on tungsten single crystals have been studied with high resolution soft X-ray photoelectron spectroscopy, SXPS, (using synchrotron radiation) and low energy electron diffraction (LEED). W4f core-level photoemission spectra and W valence band spectra have been measured at various photon energies, and at normal and grazing emission angles, for W(1 1 1) and W(2 1 1). These two surfaces were chosen for this study because it has been shown previously that W(1 1 1) covered with monolayer films of several different 4d and 5d transition metals develop nanoscale pyramidal facets with (2 1 1) faces, upon annealing. The present work extends the measurement to another catalytically active overlayer metal, Ru. The growth and evolution for dosing and annealing on both W surfaces are investigated for coverages from 0 to greater than 3 monolayers of Ru (1 ML=1.7 × 1015 atoms/cm2). Incremental dosing of Ru causes intermixing of the Ru and W atoms at the interface, even at fractional monolayer coverages. Annealing of surfaces with Ru coverages > 1 ML produces a complex set of SXPS results that indicate the formation of surface Ru/W alloys. Faceting of Ru/W(1 1 1) is observed by LEED for Ru coverages > 1 ML, after annealing at temperatures between 700 and 1000 K. Upon annealing to temperatures higher than 1000 K, the SXPS data indicate that clustering of the Ru–W surface alloys may occur. DA - 2003/10/20/ PY - 2003/10/20/ DO - 10.1016/j.susc.2003.06.001 VL - 544 IS - 2-3 SP - 193-208 SN - 1879-2758 KW - X-ray photoelectron spectroscopy KW - low energy electron diffraction (LEED) KW - growth KW - ruthenium KW - tungsten KW - single crystal surfaces KW - faceting alloys ER - TY - JOUR TI - Facets of confinement and dynamical chiral symmetry breaking AU - Maris, P. AU - Raya, A. AU - Roberts, C. D. AU - Schmidt, S. M. T2 - European Physical Journal. A, Hadrons and Nuclei DA - 2003/// PY - 2003/// VL - 18 IS - 2-3 SP - 231-235 ER - TY - JOUR TI - Dielectric functions of Cd1-xMgxTe alloy films by uusing spectroscopic ellipsometry AU - Ihn, Y. S. AU - Kim, T. J. AU - Kim, Y. D. AU - Aspnes, D. E. AU - Kossut, J. T2 - Journal of the Korean Physical Society DA - 2003/// PY - 2003/// VL - 43 IS - 4 SP - 634-637 ER - TY - JOUR TI - Cycloaddition reaction versus dimer cleavage at the Si(001): C5H8 interface AU - Lu, WC AU - Schmidt, WG AU - Bernholc, J T2 - PHYSICAL REVIEW B AB - The interface formed between an ordered monolayer of cyclopentene and silicon is studied by first-principles density-functional calculations. Several different structural models of the interface are considered and their reflectance anisotropy spectra are calculated. The spectra turn out to be highly structure dependent and can therefore be used to monitor the interface formation. We also find that coadsorption of hydrogen, which leads to dimer cleavage, can stabilize the interface by saturating the dangling bonds and releasing the high strain energy. DA - 2003/9/15/ PY - 2003/9/15/ DO - 10.1103/physrevb.68.115327 VL - 68 IS - 11 SP - SN - 2469-9969 ER - TY - JOUR TI - Characterization of hydrogen etched 6H-SiC(0001) substrates and subsequently grown AlN films AU - Hartman, JD AU - Roskowski, AM AU - Reitmeier, ZJ AU - Tracy, KM AU - Davis, RF AU - Nemanich, RJ T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - Wafers of n-type, 6H–SiC(0001) with (ND–NA)=(5.1–7.5)×1017 and 2.5×1018 were etched in a flowing 25%H2/75%He mixture within the range of 1500–1640 °C at 1 atm. Equilibrium thermodynamic calculations indicated that the presence of atomic hydrogen is necessary to achieve etching of SiC. Atomic force microscopy, optical microscopy, and low energy electron diffraction of the etched surface revealed a faceted surface morphology with unit cell and half unit cell high steps and a 1×1 reconstruction. The latter sample also exhibited a much larger number of hexagonal pits on the surface. Annealing the etched samples under ultrahigh vacuum (UHV) at 1030 °C for 15 min resulted in (1) a reduction of the surface oxygen and adventitious hydrocarbons below the detection limit of Auger electron spectroscopy, (2) a (√3×√3)R30° reconstructed surface and (3) a Si-to-C peak-to-peak height ratio of 1.2. By contrast, using a chemical vapor cleaning (CVC) process consisting of an exposure to 3000 Langmuir (L) of silane at 1030 °C for 10 min under UHV conditions resulted in a (3×3) surface reconstruction, a Si-to-C ratio of 3.9, and islands of excess silicon. Continued annealing of the latter material for an additional 10 min at 1030 °C resulted in a (1×1) LEED pattern with a diffuse ring. Films of AlN grown via MOCVD at a sample platter temperature of 1274 °C for 15 min on hydrogen etched wafers having a doping concentration of 8.7×1017 cm−3 and cleaned via annealing had a rms roughness value of ≈0.4 nm. DA - 2003/// PY - 2003/// DO - 10.1116/1.1539080 VL - 21 IS - 2 SP - 394-400 SN - 0734-2101 ER - TY - JOUR TI - Tuning substrate surface energies for blends of polystyrene and poly(methyl methacrylate) AU - Winesett, DA AU - Story, S AU - Luning, J AU - Ade, H T2 - LANGMUIR AB - We compare the efficacies of three preparation methods intended to create in an easy and inexpensive way a nonpreferential surface for a two-component homopolymer blend of polystyrene and poly(methyl methacrylate). The first method is to physically absorb two different high molecular weight copolymers of styrene and methyl methacrylate onto hydroxylated silicon oxide. The second method consists of covalently bonding octyltrichlorosilane onto hydroxylated silicon oxide with gradient coverage to create a region with a neutral surface. The third method utilizes hydroxyl terminated, miscible, low molecular weight homopolymers of polystyrene and poly(methyl methacrylate) covalently attached to the substrate. We characterize the relative effectiveness of all three methods and their temporal stability using optical microscopy, atomic force microscopy, contact angle measurements, as well as near edge X-ray absorption fine structure (NEXAFS) microscopy and spectroscopy. The preparation methods explored should be extendable to a number of polymer systems. DA - 2003/9/30/ PY - 2003/9/30/ DO - 10.1021/la030129x VL - 19 IS - 20 SP - 8526-8535 SN - 0743-7463 ER - TY - JOUR TI - The electric field at the apex of a near-field probe: implications for nano-Raman spectroscopy AU - Hallen, HD AU - Jahncke, CL T2 - JOURNAL OF RAMAN SPECTROSCOPY AB - Abstract Near‐field or nano‐Raman spectroscopy is different from its far‐field counterpart in several important respects. We present a unified view of nano‐Raman spectroscopy that accounts for these differences, which include surface enhancement, propagation differences, the presence of z ‐polarized light, and electric field gradients that give rise to new spectroscopic selection rules. We also discuss some of the recent advances in near‐field scanning optical microscopy (NSOM) and their positive impact on nano‐Raman spectroscopy. In particular, progress has been made in fabricating better probes, both apertured and apertureless, for NSOM, resulting in larger signal levels important for Raman spectroscopy. Larger signals result in shorter imaging times, the ability to achieve higher resolution and broader applicability of the technique. Copyright © 2003 John Wiley & Sons, Ltd. DA - 2003/9// PY - 2003/9// DO - 10.1002/jrs.1048 VL - 34 IS - 9 SP - 655-662 SN - 0377-0486 UR - http://dx.doi.org/10.1002/jrs.1048 N1 - – An invited paper RN - – An invited paper KW - NSOM KW - SNOM KW - Raman near-field ER - TY - JOUR TI - Radiative scalar meson decay in the light-front quark model AU - DeWitt, MA AU - Choi, HM AU - Ji, CR T2 - PHYSICAL REVIEW D AB - We construct a relativistic ${}^{3}{P}_{0}$ wave function for scalar mesons within the framework of the light-front quark model (LFQM). This scalar wave function is used to perform relativistic calculations of absolute widths for the radiative decay processes ${(0}^{++})\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma},$ ${(0}^{++})\ensuremath{\rightarrow}\ensuremath{\varphi}\ensuremath{\gamma},$ and ${(0}^{++})\ensuremath{\rightarrow}\ensuremath{\rho}\ensuremath{\gamma}$ which incorporate the effects of glueball-$q\overline{q}$ mixing. The mixed physical states are assumed to be ${f}_{0}(1370),$ ${f}_{0}(1500),$ and ${f}_{0}(1710)$ for which the flavor-glue content is taken from the mixing calculations of other works. Since experimental data for these processes are poor, our results are compared with those of a recent non-relativistic model calculation. We find that while the relativistic corrections introduced by the LFQM reduce the magnitudes of the decay widths by 50--70 %, the relative strengths between different decay processes are fairly well preserved. We also calculate decay widths for the processes $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\varphi}}{(0}^{++})\ensuremath{\gamma}$ and ${(0}^{++})\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$ involving the light scalars ${f}_{0}(980)$ and ${a}_{0}(980)$ to test the simple $q\overline{q}$ model of these mesons. Our results of the $q\overline{q}$ model for these processes are not consistent with well-established data, further supporting the idea that ${f}_{0}(980)$ and ${a}_{0}(980)$ are not conventional $q\overline{q}$ states. DA - 2003/9/1/ PY - 2003/9/1/ DO - 10.1103/physrevd.68.054026 VL - 68 IS - 5 SP - SN - 2470-0029 ER - TY - JOUR TI - R&D of diamond films in the Frontier Carbon Technology Project and related topics AU - Kobashi, K AU - Nishibayashi, Y AU - Yokota, Y AU - Ando, Y AU - Tachibana, T AU - Kawakami, N AU - Hayashi, K AU - Inoue, K AU - Meguro, K AU - Imai, H AU - Furata, H AU - Hirao, T AU - Oura, K AU - Gotoh, Y AU - Nakahara, H AU - Tsuji, H AU - Ishikawa, J AU - Koeck, FA AU - Nernanich, RJ AU - Sakai, T AU - Sakuma, N AU - Yoshida, H T2 - DIAMOND AND RELATED MATERIALS AB - R&D activities on diamond chemical vapor deposition (CVD) and field emission in the Frontier Carbon Technology Project are presented. The topics are (1) morphology control of diamond films grown by a 60-kW, 915-MHz microwave plasma CVD reactor, (2) growth technology of large single crystal diamond with a low density of defects, (3) heteroepitaxial growth technology of diamond films on Pt, (4) fabrication of sharp emitter tips on single crystal diamond, (5) field emission study from diamond particles, and (6) intense field emission from ion implanted homoepitaxial diamond layer. Research results of field emission obtained by Kyoto University and North Carolina State University are also described. DA - 2003/// PY - 2003/// DO - 10.1016/S0925-9635(02)00298-4 VL - 12 IS - 3-7 SP - 233-240 SN - 1879-0062 KW - diamond films KW - chemical vapor deposition KW - etching KW - field emission ER - TY - JOUR TI - Nanowire-induced optical anisotropy of the Si(111)-In surface AU - Wang, SC AU - Lu, WC AU - Schmidt, WG AU - Bernholc, J T2 - PHYSICAL REVIEW B AB - Ab initio calculations of the reflectance anisotropy of Si(111)-In surfaces are presented. A very pronounced optical anisotropy around 2 eV is predicted for the structural model proposed by Bunk et al. [Phys. Rev. B 59, 12 228 (1999)] for the $(4\ifmmode\times\else\texttimes\fi{}1)$ reconstructed surface. The $(4\ifmmode\times\else\texttimes\fi{}2)/(8\ifmmode\times\else\texttimes\fi{}2)$ reconstructed surface, induced by a slight distortion of the indium chains, is shown to result in a splitting of the 2 eV peak. The calculated results are in excellent agreement with recent polarized reflectance data acquired during the $(4\ifmmode\times\else\texttimes\fi{}1)\ensuremath{\rightarrow}(4\ifmmode\times\else\texttimes\fi{}2)/(8\ifmmode\times\else\texttimes\fi{}2)$ phase transition. DA - 2003/7/15/ PY - 2003/7/15/ DO - 10.1103/physrevb.68.035329 VL - 68 IS - 3 SP - SN - 2469-9969 ER - TY - JOUR TI - Molar mass estimate of dark matter from the dark mass distribution measurements AU - Mishchenko, Y AU - Ji, CR T2 - PHYSICAL REVIEW D AB - We study the distribution of dark matter versus visible matter using a set of data obtained from strong gravitational lensing in the galaxy cluster $\mathrm{CL}0024+1654$ and another set of data inferred from the universal rotation curves in spiral galaxies. The important feature of these two dramatically different observations is that the mass density profile of both visible and dark components can be estimated. From these measurements we deduce the mass of the dark matter particle and our estimate of the mass for the dark matter particle is ${\ensuremath{\mu}}_{d}\ensuremath{\approx}200--700\mathrm{MeV}.$ We contrast our estimates from $\mathrm{CL}0024+1654$ data and the universal rotation curves of the spiral galaxies and discuss their consistency. DA - 2003/9/15/ PY - 2003/9/15/ DO - 10.1103/physrevd.68.063503 VL - 68 IS - 6 SP - SN - 2470-0029 ER - TY - JOUR TI - Hiding relativistic degrees of freedom in the early universe AU - Barger, V AU - Kneller, JP AU - Langacker, P AU - Marfatia, D AU - Steigman, G T2 - PHYSICS LETTERS B AB - We quantify the extent to which extra relativistic energy density can be concealed by a neutrino asymmetry without conflicting with the baryon asymmetry measured by the Wilkinson Microwave Anisotropy Probe (WMAP). In the presence of a large electron neutrino asymmetry, slightly more than seven effective neutrinos are allowed by Big Bang Nucleosynthesis (BBN) and WMAP at 2\sigma. The same electron neutrino degeneracy that reconciles the BBN prediction for the primordial helium abundance with the observationally inferred value also reconciles the LSND neutrino with BBN by suppressing its thermalization prior to BBN. DA - 2003/9/11/ PY - 2003/9/11/ DO - 10.1016/j.physletb.2003.07.039 VL - 569 IS - 3-4 SP - 123-128 SN - 1873-2445 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0041693919&partnerID=MN8TOARS ER - TY - CONF TI - HST measurements of the angular expansion, kinematics and distance of the planetary nebula BD+30 degrees 3639 AU - Harrington, J. P. AU - Li, J. Y. AU - Borkowski, K. J. A2 - S. Kwok, M. A. Dopita A2 - Sutherland, R. S. AB - The HST WFPC2 camera was used to obtain images of the planetary nebula BD+30°3639 at two epochs separated by 5.66 years. The expansion of the nebula in Hα and [N II] 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 south-west quadrant. HST STIS echelle spectra obtained in the C II] λ2326 multiplet provide well-resolved expansion velocities at two position angles. We find that the central velocity split is ±36.3 km s -1 at a position angle of 99°. To determine the distance of BD+30°3639 by comparison of the angular expansion and the 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 (2″.47 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. Our model has an axial ratio of 1.56, is inclined to the line of sight by 9°.7, and exhibits an expansion in the plane of the sky which is 2/3 that in the radial direction, leading to a distance of 1.2 kpc. Based on a recent model atmosphere (Crowther et al., these proceedings), this distance implies a stellar luminosity of 4250 L ⊙ . C2 - 2003/// C3 - Planetary nebulae: Their evolution and role in the universe: Proceedings of the 209th symposium of the International Astronomical Union held at Canberra, Australia, 19-23 November 2001 (1st. ed.) (IAU Symposia ; 209). DA - 2003/// DO - 10.1017/s007418090020939x SP - 480 M1 - 209 PB - Published on behalf of IAU by the Astronomical Society of the Pacific ER - TY - JOUR TI - Electrical and chemical characterization of the Schottky barrier formed between clean n-GaN(0001) surfaces and Pt, Au, and Ag AU - Tracy, KM AU - Hartlieb, PJ AU - Einfeldt, S AU - Davis, RF AU - Hurt, EH AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - Platinum, gold, and silver formed abrupt, unreacted, smooth, and epitaxial metal–semiconductor interfaces when deposited from the vapor onto clean, n-type GaN(0001) films. The Schottky barrier heights, determined from data acquired using x-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, capacitance–voltage, and current–voltage measurements agreed to within the experimental error for each contact metal and had the values of 1.2±0.1, 0.9±0.1, and 0.6±0.1 eV for Pt, Au, and Ag, respectively. The band bending and the electron affinity at the clean n-GaN surface were 0.3±0.1 and 3.1±0.1 eV, respectively. The barrier height is proportional to the metal work function, indicating that the Fermi level is not pinned at the GaN surface. However, discrepancies to the Schottky–Mott model were found as evidenced by a proportionality factor of 0.44 between the work function of the metal and the resulting Schottky barrier height. The sum of these discrepancies constitute the interface dipole contributions to the Schottky barrier height which were measured to be ∼1.4, 1.3, and 0.7 eV for Pt, Au, and Ag, respectively. DA - 2003/9/15/ PY - 2003/9/15/ DO - 10.1063/1.1598630 VL - 94 IS - 6 SP - 3939-3948 SN - 0021-8979 ER - TY - JOUR TI - Discovery of a new pulsar wind nebula in the Large Magellanic Cloud AU - Gaensler, BM AU - Hendrick, SP AU - Reynolds, SP AU - Borkowski, KJ T2 - ASTROPHYSICAL JOURNAL AB - We present new high-resolution radio and X-ray observations of the supernova remnant (SNR) B0453-685 in the Large Magellanic Cloud, carried out with the Australia Telescope Compact Array and the Chandra X-Ray Observatory, respectively. Embedded in the SNR shell is a compact central nebula producing both flat-spectrum polarized radio emission and nonthermal X-rays; we identify this source as a pulsar wind nebula (PWN) powered by an unseen central neutron star. We present a new approach by which the properties of a SNR and PWN can be used to infer upper limits on the initial spin period and surface magnetic field of the unseen pulsar, and we conclude that this star was an initial rapid rotator with current properties similar to those of the Vela pulsar. As is the case for other similarly aged sources, there is currently an interaction taking place between the PWN and the SNR's reverse shock. DA - 2003/9/10/ PY - 2003/9/10/ DO - 10.1086/378687 VL - 594 IS - 2 SP - L111-L114 SN - 0004-637X KW - ISM : individual (B0453-685) KW - Magellanic Clouds KW - radio continuum : ISM KW - stars : neutron KW - supernova remnants KW - X-rays : ISM ER - TY - JOUR TI - Dielectric functions of InxGa1-xAs alloys AU - Kim, TJ AU - Ghong, TH AU - Kim, YD AU - Kim, SJ AU - Aspnes, DE AU - Mori, T AU - Yao, T AU - Koo, BH T2 - PHYSICAL REVIEW B AB - We present room-temperature pseudodielectric function spectra $〈\ensuremath{\varepsilon}〉=〈{\ensuremath{\varepsilon}}_{1}〉+i〈{\ensuremath{\varepsilon}}_{2}〉$ of ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ films grown on (100) InP by solid-source molecular-beam epitaxy. A wet-chemical etching procedure was used to remove overlayers and obtain the best approximation to the bulk dielectric responses $\ensuremath{\varepsilon}={\ensuremath{\varepsilon}}_{1}+i{\ensuremath{\varepsilon}}_{2}$ of the films. By lineshape fitting we determined the dependences of the ${E}_{1}{,E}_{1}+{\ensuremath{\Delta}}_{1}{,E}_{0}^{\ensuremath{'}}{,E}_{0}^{\ensuremath{'}}+{\ensuremath{\Delta}}_{0}^{\ensuremath{'}},$ and ${E}_{2}$ critical-point energies on x. Using a parametric semiconductor model we represent these spectra analytically to allow $〈\ensuremath{\varepsilon}〉$ to be calculated as a continuous function of x. These results are expected to be useful for design purposes, for example of nanostructures and multilayer systems involving ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}.$ DA - 2003/9/15/ PY - 2003/9/15/ DO - 10.1103/physrevb.68.115323 VL - 68 IS - 11 SP - SN - 1098-0121 ER - TY - JOUR TI - Big bang nucleosynthesis and Lambda(QCD) AU - Kneller, JP AU - McLaughlin, GC T2 - PHYSICAL REVIEW D AB - Big bang nucleosynthesis (BBN) has increasingly become the tool of choice for investigating the permitted variation of fundamental constants during the earliest epochs of the Universe. Here we present a BBN calculation that has been modified to permit changes in the QCD scale, ${\ensuremath{\Lambda}}_{\mathrm{QCD}}.$ The primary effects of changing the QCD scale upon BBN are through the deuteron binding energy ${B}_{\mathrm{D}}$ and the neutron-proton mass difference $\ensuremath{\delta}{m}_{\mathrm{np}},$ which both play crucial roles in determining the primordial abundances. In this paper we show how a simplified BBN calculation allows us to restrict the nuclear data we need to just ${B}_{\mathrm{D}}$ and $\ensuremath{\delta}{m}_{\mathrm{np}}$ yet still gives useful results so that any variation in ${\ensuremath{\Lambda}}_{\mathrm{QCD}}$ may be constrained via the corresponding shifts in ${B}_{\mathrm{D}}$ and $\ensuremath{\delta}{m}_{\mathrm{np}}$ by using the current estimates of the primordial deuterium abundance and helium mass fraction. The simplification predicts the helium-4 and deuterium abundances to within 1% and 50%, respectively, when compared with the results of a standard BBN code. But ${\ensuremath{\Lambda}}_{\mathrm{QCD}}$ also affects much of the remaining required nuclear input so this method introduces a systematic error into the calculation and we find a degeneracy between ${B}_{\mathrm{D}}$ and $\ensuremath{\delta}{m}_{\mathrm{np}}.$ We show how increased understanding of the relationship of the pion mass and/or ${B}_{\mathrm{D}}$ to other nuclear parameters, such as the binding energy of tritium and the cross section of $\mathrm{T}+{\stackrel{\ensuremath{\rightarrow}}{\mathrm{D}}}^{4}\mathrm{He}+n,$ would yield constraints upon any change in ${B}_{\mathrm{D}}$ and $\ensuremath{\delta}{m}_{\mathrm{np}}$ at the 10% level. DA - 2003/11// PY - 2003/11// DO - 10.1103/physrevd.68.103508 VL - 68 IS - 10 SP - SN - 2470-0029 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85038990077&partnerID=MN8TOARS ER - TY - JOUR TI - American Vacuum Society leadership in electronic materials processing: Past, present, and future AU - Lucovsky, G AU - Rubloff, G T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - This article traces the evolution of electronics materials processing in the American Vacuum Society (AVS) up to the present time, and projects the trajectory of this activity into the future. The format and style of this article benefits from perspective of one of the authors (G.L.), who has been editor-in-chief of the Journal of Vacuum Science and Technology (JVST) for more than 20 years, and who has additionally contributed personally to materials processing research through interactions involving AVS symposia, divisions, and publications in the JVST. Major areas of contributions are identified, and then are correlated with the evolution of the AVS and JVST. As we move into the 21st century, the foundation laid by a strong presence in electronic materials processing is proving to be the basis for emerging cross-disciplinary AVS activities in the nanoscience and technology advances that will continue to evolve in unanticipated ways in 21st century and beyond. DA - 2003/// PY - 2003/// DO - 10.1116/1.1599866 VL - 21 IS - 5 SP - S175-S181 SN - 1520-8559 ER - TY - JOUR TI - The Majorana Ge-76 double-beta decay project AU - Aalseth, CE AU - Adles, E AU - Anderson, D AU - Avignone, FT AU - Barabash, A AU - Bowyer, TW AU - Brodzinski, RL AU - Brudanin, V AU - Champangne, A AU - Collar, JI AU - Doe, PJ AU - Egorov, S AU - Elliott AU - Farach, HA AU - Gaitskell, R AU - Jordan, D AU - Jain, RK AU - Kazkaz, K AU - King, G AU - Kochetov, O AU - Konovalov, S AU - Kouzes, R AU - Miley, HS AU - Palms, JM AU - Pitts, WK AU - Reeves, JH AU - Robertson, RGH AU - Rohm, R AU - Sandukovsky, S AU - Smith, LE AU - Stekhanov, V AU - Thompson, RC AU - Tornow, W AU - Umatov, V AU - Warner, R AU - Webb, J AU - Wilkerson, JF AU - Young, A T2 - NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS AB - The interest and relevance of next-generation 0v ββ-decay experiments is increasing. Even with nonzero neutrino mass strongly suggested by solar and atmospheric neutrino experiments sensitive to δm2, 0v ββ-decay experiments are still the only way to establish the Dirac or Majorana nature of neutrinos by measuring the effective electron neutrino mass, 〈mv〉. In addition, the atmospheric neutrino oscillation experiments imply that at least one neutrino has a mass greater than about 50 meV. The Majorana Experiment expects to probe an effective neutrino mass near this critical value. Majorana is a next-generation 76Ge double-beta decay search. It will employ 500 kg of Ge, isotopically enriched to 86% in 76Ge, in the form of ∼ 200 detectors in a close-packed array. Each crystal will be electronically segmented and each segment fitted with pulse-shape analysis electronics. This combination of segmentation and pulse-shape analysis significantly improves our ability to discriminate neutrinoless double beta-decay from internal cosmogenic 68Ge and 60Co. The half-life sensitivity is estimated to be 4.2 × 1027 y corresponding to a 〈mv〉 range of ≤ 20 − 70 meV, depending on the nuclear matrix elements used to interpret the data. DA - 2003/7// PY - 2003/7// DO - 10.1016/S0920-5632(03)02116-9 VL - 124 SP - 247–252 SN - 0920-5632 ER - TY - JOUR TI - Systems of C-60 molecules inside (10,10) and (15,15) nanotube: A Monte Carlo study AU - Hodak, M AU - Girifalco, LA T2 - PHYSICAL REVIEW B AB - We use Monte Carlo simulations to investigate properties of systems of ${\mathrm{C}}_{60}$ molecules inside (10,10) and (15,15) nanotubes. In the case of the (10,10) nanotube, ${\mathrm{C}}_{60}$ molecules form a quasi-one-dimensional system. The thermodynamical properties of this system such as energy and heat capacity are found to be very close to the properties of a one-dimensional system to which interaction with a nanotube is added. The structural properties are found to be insensitive to the quasi-one-dimensional nature of the system and are the same as those calculated for a one-dimensional system of ${\mathrm{C}}_{60}$ molecules. The transformation from a periodic to a nonperiodic state (``melting'') is a gradual one and cannot be detected through the heat capacity. Inside the (15,15) nanotube, a system of ${\mathrm{C}}_{60}$ molecules behaves differently. Most notably, the heat-capacity curve shows an extra peak when compared to the result for the (10,10) case. We show that this is due to the ``melting,'' i.e., transformation of a zigzag structure existing at low temperatures to a disordered one. We also show that systems with very high density $(>95%)$ do not show this peak and ``melt'' differently. DA - 2003/8/15/ PY - 2003/8/15/ DO - 10.1103/physrevb.68.085405 VL - 68 IS - 8 SP - SN - 2469-9969 ER - TY - JOUR TI - Spherically symmetric relativistic MHD simulations of pulsar wind nebulae in supernova remnants AU - Bucciantini, N AU - Blondin, JM AU - Del Zanna, L AU - Amato, E T2 - ASTRONOMY & ASTROPHYSICS AB - Pulsars, formed during supernova explosions, are known to be sources of relativistic magnetized winds whose interaction with the expanding supernova remnants (SNRs) gives rise to a pulsar wind nebula (PWN). We present spherically symmetric relativistic magnetohydrodynamics (RMHD) simulations of the interaction of a pulsar wind with the surrounding SNR, both in particle and magnetically dominated regimes. As shown by previous simulations, the evolution can be divided into three phases: free expansion, a transient phase characterized by the compression and reverberation of the reverse shock, and a final Sedov expansion. The evolution of the contact discontinuity between the PWN and the SNR (and consequently of the SNR itself) is almost independent of the magnetization of the nebula as long as the total (magnetic plus particle) energy is the same. However, a different behaviour of the PWN internal structure is observable during the compression-reverberation phase, depending on the degree of magnetization. The simulations were performed using the third order conservative scheme by Del Zanna et al. (2003). DA - 2003/7// PY - 2003/7// DO - 10.1051/0004-6361:20030624 VL - 405 IS - 2 SP - 617-626 SN - 1432-0746 KW - ISM : supernova remnants KW - stars : pulsars : general KW - stars : winds, outflows KW - magnetohydrodynamics KW - shock waves KW - relativity ER - TY - JOUR TI - Speciation of phosphorus in phosphorus-enriched agricultural soils using X-ray absorption near-edge structure spectroscopy and chemical fractionation AU - Beauchemin, S AU - Hesterberg, D AU - Chou, J AU - Beauchemin, M AU - Simard, RR AU - Sayers, DE T2 - JOURNAL OF ENVIRONMENTAL QUALITY AB - Knowledge of phosphorus (P) species in P-rich soils is useful for assessing P mobility and potential transfer to ground water and surface waters. Soil P was studied using synchrotron X-ray absorption near-edge structure (XANES) spectroscopy (a nondestructive chemical-speciation technique) and sequential chemical fractionation. The objective was to determine the chemical speciation of P in long-term-fertilized, P-rich soils differing in pH, clay, and organic matter contents. Samples of three slightly acidic (pH 5.5-6.2) and two slightly alkaline (pH 7.4-7.6) soils were collected from A or B horizons in two distinct agrosystems in the province of Québec, Canada. The soils contained between 800 and 2100 mg total P kg(-1). Distinct XANES features for Ca-phosphate mineral standards and for standards of adsorbed phosphate made it possible to differentiate these forms of P in the soil samples. The XANES results indicated that phosphate adsorbed on Fe- or Al-oxide minerals was present in all soils, with a higher proportion in acidic than in slightly alkaline samples. Calcium phosphate also occurred in all soils, regardless of pH. In agreement with chemical fractionation results, XANES data showed that Ca-phosphates were the dominant P forms in one acidic (pH 5.5) and in the two slightly alkaline (pH 7.4-7.6) soil samples. X-ray absorption near-edge structure spectroscopy directly identified certain forms of soil P, while chemical fractionation provided indirect supporting data and gave insights on additional forms of P such as organic pools that were not accounted for by the XANES analyses. DA - 2003/// PY - 2003/// DO - 10.2134/jeq2003.1809 VL - 32 IS - 5 SP - 1809-1819 SN - 0047-2425 ER - TY - JOUR TI - Remote plasma-assisted nitridation (RPN): applications to Zr and Hf silicate alloys and Al2O3 AU - Hinkle, C AU - Lucovsky, G T2 - APPLIED SURFACE SCIENCE AB - Remote plasma-assisted nitridation or RPN is demonstrated to be a processing pathway for nitridation of Zr and Hf silicate alloys, and for Al2O3, as well. The dependence of nitrogen incorporation on the process pressure is qualitatively similar to what has been reported for the plasma-assisted nitridation of SiO2, the lower the process pressure the greater the nitrogen incorporation in the film. The increased incorporation of nitrogen has been correlated with the penetration of the plasma-glow into the process chamber, and the accompanying increase in the concentration of N2+ ions that participate in the reactions leading to bulk incorporation. The nitrogen incorporation as been studied by Auger electron spectroscopy (AES), secondary ion mass spectrometry (SIMS) and X-ray absorption spectroscopy (XAS). DA - 2003/6/30/ PY - 2003/6/30/ DO - 10.1016/S0169-4332(03)00499-9 VL - 216 IS - 1-4 SP - 124-132 SN - 0169-4332 KW - remote plasma nitridation KW - Auger electron spectroscopy KW - X-ray photoelectron spectroscopy KW - X-ray absorption spectroscopy KW - zirconium and hafnium silicate alloys KW - Al2O3 ER - TY - JOUR TI - Parity dependence of nuclear level densities AU - Agvaanluvsan, U AU - Mitchell, GE AU - Shriner, JF AU - Pato, M T2 - PHYSICAL REVIEW C AB - High resolution proton resonance data have been examined for a possible parity dependence of nuclear level densities. Five spin-parity ${\mathrm{combinations}\mathrm{---}1/2}^{+},$ ${1/2}^{\ensuremath{-}},$ ${3/2}^{\ensuremath{-}},$ ${3/2}^{+},$ and ${5/2}^{+}$---have been analyzed for three ${\mathrm{datasets}\mathrm{---}}^{44}\mathrm{Ca}(p,p),$ ${}^{48}\mathrm{Ti}(p,p),$ and ${}^{56}\mathrm{Fe}(p,p).$ Much of the uncertainty in the level density arises from the determination of the fraction of levels that are not observed. The missing fraction of levels was determined by (a) the standard width analysis method that assumes a Porter-Thomas distribution for the reduced widths and (b) a recently developed method that analyzes the spacing distribution and assumes the Wigner distribution for the nearest-neighbor spacings. There are indications of parity dependence of the level densities for several of the spin-parity combinations. DA - 2003/6// PY - 2003/6// DO - 10.1103/physrevc.67.064608 VL - 67 IS - 6 SP - SN - 1089-490X ER - TY - JOUR TI - Oxide formation and passivation for micro- and nano-electronic devices AU - Bae, C AU - Lucovsky, G T2 - APPLIED SURFACE SCIENCE AB - A low-temperature remote plasma-assisted oxidation process for interface formation and passivation has been extended from Si and SiC to GaN. The process, which can be applied to nano-scale structures including quantum dots and wires, provides excellent control of ultra-thin interfacial layers which passivate the GaN substrate, preventing a parasitic or subcutaneous oxidation of the substrate during plasma deposition of SiO2. The remote plasma processing for GaN–SiO2 heterostructures includes: (i) an in situ nitrogen plasma surface clean; (ii) a remote plasma-assisted oxidation for formation of an interfacial GaOx (x=1.5) transition region between the GaN and deposited dielectric; and (iii) a remote plasma-enhanced chemical vapor deposition of an SiO2 dielectric. DA - 2003/5/15/ PY - 2003/5/15/ DO - 10.1016/S0169-4332(03)00139-9 VL - 212 SP - 644-648 SN - 0169-4332 KW - plasma processing KW - Auger electron spectroscopy KW - semiconductor-insulator interfaces KW - interface states ER - TY - JOUR TI - Near-infrared synchrotron emission from Cassiopeia A AU - Rho, JH AU - Reynolds, SP AU - Reach, WT AU - Jarrett, TH AU - Allen, GE T2 - ASTROPHYSICAL JOURNAL AB - Recent high-energy observations of Cassiopeia A suggest the presence of synchrotron radiation, implying acceleration of cosmic rays by young supernova remnants. We detect synchrotron emission from Cas A in the near-infrared using Two Micron All-Sky Survey (2MASS) and Palomar 200 inch (5.1 m) PFIRCAM observations. The remnant is detected in the J, H, and Ks bands using 2MASS: the Ks band is the brightest, H is moderate, and J is faint. In the J and H bands, bright [Fe II] lines (1.24 and 1.64 μm) are detected spectroscopically. The Palomar observations include Ks-continuum, narrowband 1.64 μm (centered on [Fe II]) and 2.12 μm [centered on H2 (1-0)] images. While the narrowband 1.64 μm image shows filamentary and knotty structures, similar to the optical image, the Ks image shows a relatively smooth, diffuse shell, remarkably similar to the radio image. The H2 image is identical to the Ks-continuum image, with surface brightness reduced as expected for the ratio of filter bandwidths, showing no contribution of H2 lines to the Ks-band image. The broadband near-infrared fluxes of Cas A are generally consistent with, but a few tens of percent higher than, an extrapolation of the radio fluxes. The hardening to higher frequencies is possibly due to nonlinear shock acceleration and/or spectral index variation across the remnant. We show evidence of spectral index variation across Cas A using the "spectral tomography" technique. The presence of near-infrared synchrotron radiation requires the rolloff frequency to be higher than 1.5 × 1014 Hz, implying that electrons are accelerated to energies of at least E = 0.3B ergs, or 0.2 TeV. The morphological similarity in diffuse emission between the radio and Ks-band images implies that synchrotron losses are not dominant, or we would expect to see a greater concentration in knots. We also show that dust continuum is not significant in the near-infrared emission of Cas A. Our observations show unambiguous evidence that the near-infrared Ks-band emission of Cas A is from synchrotron emission by accelerated cosmic-ray electrons. DA - 2003/7/20/ PY - 2003/7/20/ DO - 10.1086/375564 VL - 592 IS - 1 SP - 299-310 SN - 0004-637X KW - acceleration of particles KW - ISM : individual (Cassiopeia A) KW - supernova remnants ER - TY - JOUR TI - Mechanical stress effect on imprint behavior of integrated ferroelectric capacitors AU - Gruverman, A AU - Rodriguez, BJ AU - Kingon, AI AU - Nemanich, RJ AU - Tagantsev, AK AU - Cross, JS AU - Tsukada, M T2 - APPLIED PHYSICS LETTERS AB - Stress-induced changes in the imprint and switching behavior of (111)-oriented Pb(Zr,Ti)O3 (PZT)-based capacitors have been studied using piezoresponse force microscopy. Visualization of polarization distribution and d33-loop measurements in individual 1×1.5-μm2 capacitors before and after stress application, generated by substrate bending, provided direct experimental evidence of stress-induced switching. Mechanical stress caused elastic switching in capacitors with the direction of the resulting polarization determined by the sign of the applied stress. In addition, stress application turned capacitors into a heavily imprinted state characterized by strongly shifted hysteresis loops and almost complete backswitching after application of the poling voltage. It is suggested that substrate bending generated a strain gradient in the PZT layer, which produced asymmetric lattice distortion with preferential polarization direction and triggered polarization switching due to the flexoelectric effect. DA - 2003/7/28/ PY - 2003/7/28/ DO - 10.1063/1.1593830 VL - 83 IS - 4 SP - 728-730 SN - 0003-6951 ER - TY - JOUR TI - First-principles investigation of carbon nanotube capacitance AU - Pomorski, P AU - Roland, C AU - Guo, H AU - Wang, J T2 - PHYSICAL REVIEW B AB - With ab initio simulations based on a real-space nonequilibrium Green's function formalism, we have investigated the charging of carbon nanotube systems. The charging effects are described by capacitance coefficients, for which we provide a first-principles estimate. Specifically, the capacitance matrix of nested armchair nanotubes, the insertion of one nanotube into another, and a junction of two metallic nanotubes with a large conductance gap were calculated with a focus on investigating the bias-induced charges. For the case of the nanotube junction, the numerical value of the capacitance is sufficiently high, as to be useful for future device applications. DA - 2003/4/15/ PY - 2003/4/15/ DO - 10.1103/physrevb.67.161404 VL - 67 IS - 16 SP - SN - 1098-0121 ER - TY - JOUR TI - Electronic structure of transition metal/rare earth alternative high-K gate dielectrics: interfacial band alignments and intrinsic defects AU - Lucovsky, G T2 - MICROELECTRONICS RELIABILITY AB - Hybrid inorganic–organic solar cells typically combine a transition metal oxide and organic absorber to form the donor–acceptor pair. Here, we explore the use of a rare earth oxide to function as the inorganic component of a hybrid solar cell. Oxidized neodymium (Nd2O3) particles are combined with [6,6]-phenyl C61 butyric acid methyl ester (PCBM) to form the solar cell active layer. The short circuit current and open circuit voltage are both enhanced compared to pure PCBM. In addition, the photoinduced absorption decay rate increases, and photobleaching is observed. This provides evidence for charge transfer between the organic and rare earth inorganic components. DA - 2003/// PY - 2003/// DO - 10.1016/S0026-2714(03)00253-1 VL - 43 IS - 9-11 SP - 1417-1426 SN - 0026-2714 ER - TY - JOUR TI - Electronic structure of transition metal high-k dielectrics: interfacial band offset energies for microelectronic devices AU - Lucovsky, G AU - Raynor, GB AU - Zhang, Y AU - Fulton, CC AU - Nemanich, RJ AU - Appel, G AU - Ade, H AU - Whitten, JL T2 - APPLIED SURFACE SCIENCE AB - Transition metal silicates, (ZrO2)x(SiO2)1� x, have dielectric constants k > 10 that make them attractive for advanced Si devices. Band offset energies relative to Si are an important factor in determining tunneling leakage current, and internal photoemission. Studies by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and X-ray absorption spectroscopy (XAS) are combined with ab initio calculations to identify the compositional variation of the band-gap, and valence and conduction band offset energies of Zr silicate alloys with respect to Si. The minimum conduction band offset, due to DA - 2003/5/15/ PY - 2003/5/15/ DO - 10.1016/S0169-4332(03)00055-2 VL - 212 IS - 2003 May 15 SP - 563-569 SN - 0169-4332 KW - ab initio quantum chemical calculations KW - plasma processing KW - Auger electron spectroscopy KW - X-ray photoelectron spectroscopy KW - X-ray absorption spectroscopy KW - zirconium silicate alloys KW - semiconductor-insulator interfaces ER - TY - JOUR TI - Distribution functions for a two-dimensional non-interacting quantum electron gas in an external magnetic field AU - Lado, F T2 - MOLECULAR PHYSICS AB - The exact n-body distribution functions are calculated for a two-dimensional, non-interacting quantum electron gas in an external magnetic field for any temperature and density. At low tempertures and filled lowest Landau level (LLL), these functions are identical to the exact distribution functions obtained by Jancovici [1981, Phys. Rev. Lett., 46, 386] for the classical two-dimensional one-component plasma (2DOCP) at the special plasma parameter Γ = 2, thus establishing that the 2DOCP provides an exact classical Boltzmann factor which describes the ideal LLL quantum state associated with the integral quantum Hall effect. DA - 2003/6/10/ PY - 2003/6/10/ DO - 10.1080/00268970310000755642 VL - 101 IS - 11 SP - 1635-1639 SN - 0026-8976 ER - TY - JOUR TI - Device-quality GaN-dielectric interfaces by 300 degrees C remote plasma processing AU - Bae, C AU - Rayner, GB AU - Lucovsky, G T2 - APPLIED SURFACE SCIENCE AB - In previous studies, device-quality Si–SiO2 interfaces and dielectric bulk films (SiO2) were prepared using a two-step process; (i) remote plasma-assisted oxidation (RPAO) to form a superficially interfacial oxide (∼0.6 nm) and (ii) remote plasma enhanced chemical vapor deposition (RPECVD) to deposit the oxide film. The same approach has been applied to GaN–SiO2 system. Low-temperature (300 °C) remote N2/He plasma cleaning of the GaN surface, and the kinetics of GaN oxidation using RPAO process and subcutaneous oxidation during the SiO2 deposition using an RPECVD process have been investigated from analysis of on-line Auger electron spectroscopy (AES) features associated N and O. Compared to single-step SiO2 deposition, significantly reduced defect state densities are obtained at the GaN–dielectric interfaces by independent control of GaN–GaOx (x∼1.5) interface formation by RPAO, and SiO2 deposition by RPECVD. DA - 2003/6/30/ PY - 2003/6/30/ DO - 10.1016/S0169-4332(03)00497-5 VL - 216 IS - 1-4 SP - 119-123 SN - 1873-5584 KW - GaN-dielectric interfaces KW - surface leaning KW - subcutaneous oxidation KW - Ga2O3 KW - SiO2 KW - MOSd devices ER - TY - JOUR TI - Contributions to the infrared effective charges of oxides and chalcogenides from equilibrium charge and dynamic charge redistribution during normal mode motions AU - Sremaniak, LS AU - Whitten, JL AU - Menon, M AU - Lucovsky, G T2 - APPLIED SURFACE SCIENCE AB - Empirical force constant models for infrared (IR) and Raman scattering have emphasized differences between non-crystalline oxides and chalcogenides, attributing them to different bond angles at the two-fold coordinated O- and S(Se)-atoms in spite of the fact that both classes of materials form continuous random networks (CRNs) with equivalent 8N rule bonding coordination. This article applies ab initio electronic structure calculations to determine (i) equilibrium bonding geometries, and (ii) infrared effective charges for normal mode motions of O- and S-atoms in SiO2, and GeS2 and As2S3, respectively. Differences in equilibrium bond angles and normal mode effective charges are shown to result from quantitative differences in SiO, and GeS and GeSe bond ionicities that optimize the SiO2, and GeS2 and As2S3 total energies at markedly different bond angles. DA - 2003/5/15/ PY - 2003/5/15/ DO - 10.1016/S0169-4332(03)00087-4 VL - 212 SP - 839-843 SN - 0169-4332 KW - non-crystalline oxides and chalcogenides KW - continuous random networks KW - infrared active vibrations KW - infrared effective charges KW - Ab initio quantum chemistry calculations KW - normal mode motions ER - TY - JOUR TI - Calculation of ionic charging free energies in simulation systems with atomic charges, dipoles, and quadrupoles AU - Herce, H. D. AU - Darden, T. AU - Sagui, C. T2 - Journal of Chemical Physics AB - The ionic charging free energy is a very sensitive probe for the treatment of electrostatics in any given simulation setting. In this work, we present methods to compute the ionic charging free energy in systems characterized by atomic charges and higher-order multipoles, mainly dipoles and quadrupoles. The results of these methods for periodic boundary conditions and for spherical clusters are then compared. For the treatment of spherical clusters, we introduce a generalization of Gauss’ law that links the microscopic variables to the measurable macroscopic electrostatics via a work function. DA - 2003/// PY - 2003/// DO - 10.1063/1.1609191 VL - 119 IS - 15 SP - 7621-7632 ER - TY - JOUR TI - Band offset energies in zirconium silicate Si alloys AU - Lucovsky, G AU - Rayner, B AU - Zhang, Y AU - Appel, G AU - Whitten, J T2 - APPLIED SURFACE SCIENCE AB - Transition metal silicates, (ZrO2)x(SiO2)1−x, with dielectric constants, k>10 have been proposed as alternative dielectrics for advanced Si devices. Studies by X-ray absorption, X-ray photoelectron and Auger electron spectroscopy are combined to identify the compositional variation of the valence and conduction band offset energies with respect to Si in Zr silicate alloys. The minimum conduction band offset energy, associated with localized Zr 4d∗-states, is ∼1.4 eV, and is independent of alloy composition, while valence band offsets decrease monotonically with increasing ZrO2 content. Differences between the coupling of tunneling electrons to localized Zr 4d∗ and extended Si 3s∗ states, characterized by respective tunneling masses of ∼0.5mo and ∼0.2mo, combine to contribute to a minimum in the direct tunneling current in the mid-silicate-alloy composition range, x∼0.4–0.6. DA - 2003/6/30/ PY - 2003/6/30/ DO - 10.1016/S0169-4332(03)00429-X VL - 216 IS - 1-4 SP - 215-222 SN - 0169-4332 KW - plasma processing and deposition KW - Auger electron spectroscopy KW - X-ray photoelectron spectroscopy KW - X-ray absorption spectroscopy KW - zirconium silicate alloys KW - semiconductor-dielectric band offset energies ER - TY - JOUR TI - Active-sterile neutrino conversion: consequences for the r-process and supernova neutrino detection AU - Fetter, J AU - McLaughlin, GC AU - Balantekin, AB AU - Fuller, GM T2 - ASTROPARTICLE PHYSICS AB - We examine active–sterile neutrino conversion in the late time post-core-bounce supernova environment. By including the effect of feedback on the Mikheyev–Smirnov–Wolfenstein (MSW) conversion potential, we obtain a large range of neutrino mixing parameters which produce a favorable environment for the r-process. We look at the signature of this effect in the current generation of neutrino detectors now coming on line. We also investigate the impact of the neutrino–neutrino forward-scattering-induced potential on the MSW conversion. DA - 2003/2// PY - 2003/2// DO - 10.1016/S0927-6505(02)00156-1 VL - 18 IS - 5 SP - 433-448 SN - 1873-2852 ER - TY - JOUR TI - A new twist to the long-standing three-nucleon analyzing power puzzle AU - Neidel, EM AU - Tornow, W AU - Trotter, DEG AU - Howell, CR AU - Crowell, AS AU - Macri, RA AU - Walter, RL AU - Weisel, GJ AU - Esterline, J AU - Witala, H AU - Crowe, BJ AU - Pedroni, RS AU - Markoff, DM T2 - PHYSICS LETTERS B AB - New results for the neutron–deuteron analyzing power Ay(θ) at En=1.2 and 1.9 MeV and their comparison to proton–deuteron data reveal a sizeable and unexpected difference which increases with decreasing center-of-mass energy. This finding calls for the theoretical treatment of a subtle electromagnetic effect presently not incorporated in rigorous three-nucleon scattering calculations, before it is justified to invoke charge-dependent three-nucleon forces and/or other new physics. DA - 2003/1/16/ PY - 2003/1/16/ DO - 10.1016/S0370-2693(02)03106-4 VL - 552 IS - 1-2 SP - 29-34 SN - 0370-2693 ER - TY - JOUR TI - Use of functionalized WS2 nanotubes to produce new polystyrene/polymethylmethacrylate nanocomposites AU - Zhang, W AU - Ge, S AU - Wang, Y AU - Rafailovich, MH AU - Dhez, O AU - Winesett, DA AU - Ade, H AU - Shafi, KVPM AU - Ulman, A AU - Popovitz-Biro, R AU - Tenne, R AU - Sokolov, J T2 - POLYMER AB - Multiwall WS2 nanotubes of 40–50 nm diameter were functionalized with n-octadecyl phosphonic acid by sonication in toluene and blended with mixtures of polystyrene (PS) and polymethylmethacrylate (PMMA) to form new nanocomposite (NC) materials. The surface and domain structures were studied by atomic force microscopy (AFM), scanning transmission X-ray microscopy (STXM) and transmission electron microscopy (TEM) for various levels of loading of nanotubes up to 20 wt%. Phase-separated domain size and surface roughness of the nanocomposite films were found to be dramatically reduced relative to the pure homopolymer blend and good dispersal of the nanotubes in the blend matrix was attained. DA - 2003/3// PY - 2003/3// DO - 10.1016/S0032-3861(03)00053-3 VL - 44 IS - 7 SP - 2109-2115 SN - 0032-3861 KW - polymer composite materials KW - polymer physics KW - pure homopolymer blend ER - TY - JOUR TI - Study of the dielectric function of ZnS by spectroscopic ellipsometry AU - Ghong, T. H. AU - Kim, T. J. AU - Kim, Y. D. AU - Kim, S. J. AU - Aspnes, D. E. AU - Choi, Y. D. AU - Yu, Y. M. T2 - Journal of the Korean Physical Society DA - 2003/// PY - 2003/// VL - 42 IS - 2003 Feb SP - S238-241 ER - TY - JOUR TI - Structural dependence of breakdown characteristics and electrical degradation in ultrathin RPECVD oxide/nitride gate dielectrics under constant voltage stress AU - Lee, YM AU - Wu, YD AU - Bae, C AU - Hong, JG AU - Lucovsky, G T2 - SOLID-STATE ELECTRONICS AB - Abstract The structural dependence of breakdown characteristics and electrical degradation in ultrathin oxide/nitride (O/N) dielectrics, prepared by remote plasma enhanced chemical vapor deposition, is investigated under constant voltage stress. In the early stage of oxide wearout, soft breakdown is a local phenomenon dominated by the tunneling current. After a given period of stress, a strong channel-length dependence of dielectric breakdown and the corresponding stress-induced leakage current from the evolution of increased tunneling current have been found. Stacked O/N dielectrics with interface nitridation demonstrate improved device performance on subthreshold swing and threshold voltage shifts after stress, indicating the suppression of stress-induced traps at the oxide/Si and oxide/drain interfaces compared to thermal oxides. Experimental evidence shows more severe breakdown and device degradation in the threshold voltage, drain current and transconductance for shorter channel PMOSFETs with O/N dielectrics. These degradations result from the enhancement of hole trapping in the gate–drain overlap region as evidenced by a positive off-state leakage current, which leads to hard breakdown, and the complete failure of device functionality. DA - 2003/1// PY - 2003/1// DO - 10.1016/S0038-1101(02)00257-5 VL - 47 IS - 1 SP - 71-76 SN - 1879-2405 KW - dielectric degradation KW - soft breakdown KW - RPECVD oxide/nitride dielectric KW - stress-induced leakage current KW - constant voltage stress KW - hard breakdown ER - TY - JOUR TI - Stability of standing accretion shocks, with an eye toward core-collapse supernovae AU - Blondin, JM AU - Mezzacappa, A AU - DeMarino, C T2 - ASTROPHYSICAL JOURNAL AB - We examine the stability of standing, spherical accretion shocks. Accretion shocks arise in core-collapse supernovae (the focus of this paper), star formation, and accreting white dwarfs and neutron stars. We present a simple analytic model and use time-dependent hydrodynamics simulations to show that this solution is stable to radial perturbations. In two dimensions we show that small perturbations to a spherical shock front can lead to rapid growth of turbulence behind the shock, driven by the injection of vorticity from the now nonspherical shock. We discuss the ramifications this instability may have for the supernova mechanism. DA - 2003/2/20/ PY - 2003/2/20/ DO - 10.1086/345812 VL - 584 IS - 2 SP - 971-980 SN - 0004-637X KW - accretion, accretion disks KW - hydrodynamics KW - shock waves KW - supernovae : general KW - turbulence ER - TY - JOUR TI - Optical properties of InGaAs alloy films in the E-2 region by spectroscopic ellipsometry AU - Ihn, Y. S. AU - Ghong, T. H. AU - Kim, Y. D. AU - Kim, S. J. AU - Aspnes, D. E. AU - Yao, T. AU - Koo, B. H. T2 - Journal of the Korean Physical Society DA - 2003/// PY - 2003/// VL - 42 IS - 2003 Feb SP - S242-245 ER - TY - JOUR TI - Electromagnetic effects and the long-standing three-nucleon analyzing power puzzle AU - Tornow, W AU - Neidel, EM AU - Trotter, DEG AU - Howell, CR AU - Crowell, AS AU - Macri, RA AU - Walter, RL AU - Weisel, GJ AU - Esterline, J AU - Witala, H AU - Crowe, BJ AU - Pedroni, RS AU - Markoff, DM T2 - MODERN PHYSICS LETTERS A AB - New results for the neutron-deuteron analyzing power A y (θ) at E n = 1.2 and 1.9 MeV and their comparison to proton-deuteron data reveal a sizeable and unexpected difference which increases with decreasing center-of-mass energy. This finding calls for the theoretical treatment of a subtle electromagnetic effect presently not incorporated in rigorous three-nucleon scattering calculations, before it is justified to invoke charge-dependent three-nucleon forces and/or other new physics. DA - 2003/2/28/ PY - 2003/2/28/ DO - 10.1142/S0217732303010314 VL - 18 IS - 2-6 SP - 258-261 SN - 0217-7323 ER - TY - JOUR TI - Combined atomic force microscopy and scanning tunneling microscopy imaging of cross-sectioned GaN light-emitting diodes AU - Bender, J. W. AU - Salmon, M. E. AU - Russell, P. E. T2 - Scanning DA - 2003/// PY - 2003/// VL - 25 IS - 1 SP - 45-51 ER - TY - JOUR TI - Analyzing power for the photodisintegration of the deuteron between E-gamma=2.4 and 4.0 MeV AU - Tornow, W AU - Czakon, NG AU - Howell, CR AU - Hutcheson, A AU - Kelley, JH AU - Litvinenko, VN AU - Mikhailov, S AU - Pinayev, , IV AU - Weisel, GJ AU - Witala, H T2 - MODERN PHYSICS LETTERS A AB - The photon analyzing power for the photodisintegration of the deuteron was measured for seven gamma-ray energies between 2.39 and 4.05 MeV using the linearly polarized gamma-ray beam of the High-Intensity Gamma-ray Source at the Duke Free-Electron Laser Laboratory. The data provide a stringent test of theoretical calculations for the inverse reaction, the neutron-proton radiative capture reaction at energies important for Big-Bang nucleosynthesis. Our data are in excellent agreement with potential model and effective field theory calculations. DA - 2003/2/28/ PY - 2003/2/28/ DO - 10.1142/S021773230301034X VL - 18 IS - 2-6 SP - 282-285 SN - 0217-7323 ER - TY - JOUR TI - A quantum Monte Carlo study of electron correlation in transition metal oxygen molecules AU - Wagner, L AU - Mitas, L T2 - CHEMICAL PHYSICS LETTERS AB - We carry out calculations of selected transition metal–oxygen molecules within density functional theory, post-Hartree–Fock, and quantum Monte Carlo (QMC) methods. Transition metal–oxygen systems have competing electron correlation and exchange effects and require accurate treatment of both of these effects. We analyze the biases of the mentioned methods and their impacts on the electronic structure. We evaluate binding energies and compare the accuracy of various approaches including single and multi-reference trial wave functions in QMC. DA - 2003/3/14/ PY - 2003/3/14/ DO - 10.1016/S0009-2614(03)00128-3 VL - 370 IS - 3-4 SP - 412-417 SN - 1873-4448 ER - TY - JOUR TI - A quantum Monte Carlo and density functional theory study of the electronic structure of peroxynitrite anion AU - Harkless, JAW AU - Rodriguez, JH AU - Mitas, L AU - Lester, WA T2 - JOURNAL OF CHEMICAL PHYSICS AB - Single point calculations of the ground state electronic structure of peroxynitrite anion have been performed at the optimized cis geometry using the restricted Hartree–Fock (RHF), Møller Plesset second order perturbation theory (MP2), generalized gradient approximation density functional theory (GGA DFT) in the B3LYP form and two quantum Monte Carlo (QMC) methods, variational Monte Carlo (VMC) and diffusion Monte Carlo (DMC). These calculations reveal differences in atomization energies estimated by B3LYP (287.03 kcal/mol), MP2 (290.84 kcal/mol), and DMC, 307.4(1.9) kcal/mol, as compared to experiment, 313(1) kcal/mol. The error associated with MP2 and B3LYP methods is attributed largely to differential recovery of correlation energies for neutral nitrogen and oxygen atoms relative to the oxygen and peroxynitrite anions. In addition, basis set studies were carried out to determine potential sources of error in MP2 and B3LYP valence energy values. Our studies indicate that MP2 and B3LYP valence energies are strongly dependent on the presence of diffuse functions for the negative ions O− and ONOO−. DA - 2003/3/15/ PY - 2003/3/15/ DO - 10.1063/1.1544732 VL - 118 IS - 11 SP - 4987-4992 SN - 0021-9606 ER - TY - JOUR TI - Stabilizing wide bandwidth, tuning fork detected force feedback with nonlinear interactions AU - Jahncke, CL AU - Hallen, HD T2 - JOURNAL OF APPLIED PHYSICS AB - Near-field scanning optical microscope force feedback can be destabilized by the anisotropy in response times engendered by nonlinear tip sample interactions. This nonlinear interaction, the tapping of the tip on layers adsorbed on the sample, is important when the intrinsic damping of the system is low. We present strong evidence of tapping on adlayers rather than the sample surface at operational distances, and numerically solve a model to find the dynamics of tip motion. These results illuminate the origins of feedback problems when using tuning fork detection of oscillation amplitude, and show an optimal technique that uses the rapid response of the tip-adlayer nonlinearity to circumvent the slow damping response and enable wide bandwidth, stable distance regulation for these systems. DA - 2003/1/15/ PY - 2003/1/15/ DO - 10.1063/1.1528307 VL - 93 IS - 2 SP - 1274-1282 SN - 1089-7550 UR - http://dx.doi.org/10.1063/1.1528307 ER - TY - JOUR TI - What can be learned with a lead-based supernova-neutrino detector? AU - Engel, J AU - McLaughlin, GC AU - Volpe, C T2 - PHYSICAL REVIEW D AB - We examine the prospects for using lead as a supernova-neutrino detector by considering the spectrum of electrons produced, and the number of one- and two-neutron events. We show that the electron energy spectrum from charged-current reactions can be used to extract information about the high-temperature component of the neutrino spectrum. Some degree of electron neutrino oscillation is expected in the supernova envelope. We examine the prospects for untangling the signatures of various oscillation scenarios, including, e.g. normal or inverted hierarchies, and different values for the small mixing angle, theta_13. DA - 2003/1/1/ PY - 2003/1/1/ DO - 10.1103/physrevd.67.013005 VL - 67 IS - 1 SP - SN - 1550-2368 ER - TY - JOUR TI - Response to "Comment on 'Pd growth and subsequent Schottky barrier formation on chemical vapor cleaned p-type GaN surfaces' [J. Appl. Phys. 91, 732 (2002)]" AU - Hartlieb, PJ AU - Roskowski, A AU - Davis, RF AU - Platow, W AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS DA - 2003/3/15/ PY - 2003/3/15/ DO - 10.1063/1.1542911 VL - 93 IS - 6 SP - 3679-3679 SN - 0021-8979 ER - TY - JOUR TI - Measurement of image contrast using diffraction enhanced imaging AU - Kiss, M. Z. AU - Sayers, D. E. AU - Zhong, Z. T2 - Physics in Medicine & Biology DA - 2003/// PY - 2003/// VL - 48 IS - 3 SP - 325-340 ER - TY - JOUR TI - First-principle study of molecular springs under shear deformation AU - Kang, HS AU - Bernholc, J T2 - JOURNAL OF PHYSICAL CHEMISTRY A AB - Recently synthesized tunable molecular springs are investigated theoretically using massively parallel density functional simulations with the generalized gradient approximation. The springs are salts of organosilver complexes that crystallize in structures with monoclinic symmetry. For springs with NO3- (N-spring) and ClO4- (Cl-spring) ions as negative balancers, we are able to refine their X-ray structures. Our calculations of total energies as functions of the nonorthogonal lattice angle β correctly reproduce the experimental equilibrium values of the angle for both the N- and Cl-springs. For the N-spring, our calculations reveal that the nitrate ions undergo concerted propeller rotations in the clockwise direction as the angle increases by 10° around the experimental value. For the Cl-spring, the rotations of chlorate ions are more enhanced in a limited range of the β angle, but they move in the counterclockwise direction. For the N-spring, the potential energy curve is symmetric and the shear modulus is about 0.01TPa. Calculations of the electronic density of states show that both springs are semiconductors. DA - 2003/3/6/ PY - 2003/3/6/ DO - 10.1021/jp0267353 VL - 107 IS - 9 SP - 1377-1383 SN - 1089-5639 ER - TY - JOUR TI - Fibrous structures on diamond and carbon surfaces formed by hydrogen plasma under direct current bias and field electron-emission properties AU - Kobashi, K AU - Tachibana, T AU - Yokota, Y AU - Kawakami, N AU - Hayashi, K AU - Yamamoto, K AU - Koga, Y AU - Fujiwara, S AU - Gotoh, Y AU - Nakahara, H AU - Tsuji, H AU - Ishikawa, J AU - Kock, FA AU - Nemanich, RJ T2 - JOURNAL OF MATERIALS RESEARCH DA - 2003/2// PY - 2003/2// DO - 10.1557/JMR.2003.0042 VL - 18 IS - 2 SP - 305-326 SN - 2044-5326 ER - TY - JOUR TI - Zone determinant expansions for nuclear lattice simulations AU - Lee, DJ AU - Ipsen, ICF T2 - PHYSICAL REVIEW C AB - We discuss simulations of finite temperature nuclear matter on the lattice. We introduce a new approximation to nucleon matrix determinants that is physically motivated by chiral effective theory. The method involves breaking the lattice into spatial zones and expanding the determinant in powers of the boundary hopping parameter. DA - 2003/12// PY - 2003/12// DO - 10.1103/physrevc.68.064003 VL - 68 IS - 6 SP - SN - 1089-490X ER - TY - PCOMM TI - More than texts need reform in middle schools - Reply AU - Hubisz, J AB - Hubisz replies: I am quite pleased with the response to my article on middle-school texts. The large number of letters both supports my message and makes it clear that many others are concerned about the problem and are attempting to do something about it.Martha Schwartz asks if I have looked for signs of change in the textbook selection process. Admittedly I am most concerned about the end product—the adopted texts. But because of the publicity that my work on the textbook problem has received through print, radio, and television, I have responded to hundreds of requests (from a governor, several state senators, and a host of science curriculum supervisors and teachers) for my suggestions on a procedure for selecting science textbooks. Their replies suggest that changes are being attempted. After a radio interview in California, I received a blizzard of horror stories about the selection process. Schwartz’s description of the process is similar to my proposal, except that many excellent texts never get to the first stage. My article at http://www.johnlocke.org/policy_reports/2003012933.html describes why many publishers do not even bother to submit their texts. Richard Feynman once served in California on a textbook selection committee that graded a blank mathematics book higher than the two other books in the series. 1 1. R. Leighton, in Surely You’re Joking, Mr. Feynman! Adventures of a Curious Character, E. Hutchings, ed., W. W. Norton, New York, 1989. That incident suggests that time and manpower can overwhelm even the most conscientious and expert reviewers. Schwartz’s reference 2 contains a discussion of how that can happen.Kimball Milton is correct to point out that we have to be precise, but we are not likely to change the historically sanctioned language. I have suggested that texts clarify the vocabulary and now suggest that when referring to such words used inappropriately, we include them in quotes as our grammar dictates.Richard Factor’s letter reminded me of the first time I heard “antipode” spoken aloud. I was glad that I had never needed to use it in conversation. Pronunciation guides for specialized vocabulary are generally a good idea, but box 1 of my article referred to standard English/American words. But, then, how do you pronounce “laboratory” and “apparatus”?I thank Norman R. Dotti and Borut Gogala for two practical examples of the importance of precision to add to my collection. I have just finished reading an informative forensic science book (they are great for demonstrating the scientific approach to solving problems). The book informed me that “7,000 volts of electricity jumped into the body of Theodore ‘Ted’ Bundy,” that one could “send 50,000 volts of electricity for 8 seconds into the wearer [of a shock belt used to control difficult prisoners],” and that “the current generated… could be detected and measured in millivolts.” Middle-school texts frequently confuse current and voltage.Jay Pasachoff and I have discussed these problems in e-mail exchanges. He would admit that what a writer produces for textbook publishers is out of the author’s hands once submitted, and the manuscripts do get edited to “simplify the science” and “adjust” the readability, as one editor told me. The original report did speak of some excellent material in one of the reviewed texts, but only because it was removed in the next edition. I am concerned that “emphasizing the good parts” as Pasachoff suggests may give readers the idea that the whole book is being recommended. There certainly are good parts, but the large number of people involved in developing these books militates against such a conclusion. Although my Web site http://www.science-house.org/ middle-school reports errors in textbooks, its main purpose is to point out good resources for the middle-school classroom and for teacher enrichment.Many years ago, I visited one of my son’s classes. After the students successfully identified biologists and chemists and were asked which scientists studied the stars, they answered in unison, “astrologers.” After class, I pointed out that they were astronomers and the teacher asked, “Aren’t they the same?” Perhaps now her next 20 years of students will not be led astray. We need more physicists to visit more classrooms and to attend more school board meetings and to volunteer to review new text offerings. Together we can accomplish much.REFERENCESection:ChooseTop of pageREFERENCE <<1. R. Leighton, in Surely You’re Joking, Mr. Feynman! Adventures of a Curious Character, E. Hutchings, ed., W. W. Norton, New York, 1989. Google Scholar© 2003 American Institute of Physics. DA - 2003/9// PY - 2003/9// DO - 10.1063/1.4797146 SP - 15-16 ER - TY - JOUR TI - Inverse power law quintessence with nontracking initial conditions AU - Kneller, JP AU - Strigari, LE T2 - PHYSICAL REVIEW D AB - A common property of popular models of quintessence dark energy is the convergence to a common solution from a large range of the initial conditions. We reexamine the popular inverse power-law model of quintessence (where the common solution is dubbed as the ``tracker'') with particular attention to the initial conditions for the field and their influence on the evolution. We find that previously derived limits on the parameters of the potential in this model are valid only in a range of initial conditions. A reasonably sharp boundary lies where the initial energy density of the scalar field is equal to that of the background radiation component. An initial quintessence energy density above this equipartition value leads to a solution that will not have joined the tracker solution by the present epoch. These nontracker solutions possess the property that their present equation of state is very compatible with the observed bounds and independent of the exponent of the potential. DA - 2003/10/15/ PY - 2003/10/15/ DO - 10.1103/physrevd.68.083517 VL - 68 IS - 8 SP - SN - 1550-2368 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0344875158&partnerID=MN8TOARS ER - TY - JOUR TI - Hard loops, soft loops, and high density effective field theory AU - Schafer, T T2 - NUCLEAR PHYSICS A AB - We study several issues related to the use of effective field theories in QCD at large baryon density. We show that the power counting is complicated by the appearance of two scales inside loop integrals. Hard dense loops involve the large scale $\mu^2$ and lead to phenomena such as screening and damping at the scale $g\mu$. Soft loops only involve small scales and lead to superfluidity and non-Fermi liquid behavior at exponentially small scales. Four-fermion operators in the effective theory are suppressed by powers of $1/\mu$, but they get enhanced by hard loops. As a consequence their contribution to the pairing gap is only suppressed by powers of the coupling constant, and not powers of $1/\mu$. We determine the coefficients of four-fermion operators in the effective theory by matching quark-quark scattering amplitudes. Finally, we introduce a perturbative scheme for computing corrections to the gap parameter in the superfluid phase DA - 2003/12/1/ PY - 2003/12/1/ DO - 10.1016/j.nuclphysa.2003.08.028 VL - 728 IS - 1-2 SP - 251-271 SN - 1873-1554 UR - http://inspirehep.net/record/622886 ER - TY - JOUR TI - Gallium-rich reconstructions on GaAs(001) AU - Pristovsek, M AU - Tsukamoto, S AU - Ohtake, A AU - Koguchi, N AU - Orr, BG AU - Schmidt, WG AU - Bernholc, J T2 - PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS AB - Abstract Ga‐rich reconstructions on GaAs(001) surfaces were prepared by annealing and Ga dosing of Molecular Beam Epitaxy grown samples and analyzed in‐situ by Reflectance Anisotropy Spectroscopy and Reflection High‐Energy Electron Diffraction. Annealing or dosing gallium above about 800 K invariably results in a (4 × 2)/ c (8 × 2) reconstruction. Lowering the temperature or annealing below 800 K results in a (2 × 6)/(3 × 6) reconstruction. By dosing the (2 × 6)/(3 × 6) reconstruction with more than 0.2 monolayer of gallium, it transforms into a (4 × 6) reconstruction. The observed translational symmetries and measured RAS spectra are compared with results of first‐principles calculations. None of the (2 × 6) structures proposed in the literature is energetically stable. The RAS spectrum calculated for the ζ (4 × 2) model resembles reasonably the data measured for the (4 × 2) surface. The RAS spectra calculated for (2 × 6) symmetries indicate that mixed Ga‐As dimers likely are a structural element of the corresponding surface reconstructions. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) DA - 2003/11// PY - 2003/11// DO - 10.1002/pssb.200301885 VL - 240 IS - 1 SP - 91-98 SN - 1521-3951 ER - TY - JOUR TI - Environments of Mid-Cretaceous Saharan dinosaurs AU - Russell, DA AU - Paesler, MA T2 - CRETACEOUS RESEARCH AB - Recent studies of the oceanic record suggest that the Earth was a global greenhouse during middle Cretaceous time. A review of topographic, sedimentary and biologic data pertaining to terrestrial mid-Cretaceous equatorial environments broadly supports the climatic inferences of marine studies. In particular, analyses of widely-occurring low latitude Saharan sediments support the Cretaceous greenhouse hypothesis. In comparison to marine ecosystems, terrestrial ecosystems respond more sensitively to atmospherically transported heat and nutrients because of the more tenuous presence of the hydrosphere on land. Indeed, the morphologies of terrestrial biota suggest that: (1) equatorial mid-Cretaceous climates were episodic rather than seasonal; (2) convective storms although infrequent were violent; and (3) a moist intertropical convergence zone was absent. Cretaceous atmospheric dynamics apparently differed importantly from those of the present. Circumstantial evidence suggests that (1) higher atmospheric carbon dioxide levels probably stimulated the emission of other greenhouse gases; and (2) higher humidity levels reduced diurnal temperature variations but impaired evaporative thermoregulatory mechanisms. That terrestrial ecosystems withstood greenhouse conditions in low latitudes as well as they did underscores the adaptability of terrestrial life. Analogies for future environmental stresses and responses, whether anthropogenic or resulting from other causes, might be found in the terrestrial record of the Cretaceous equatorial zone. DA - 2003/10// PY - 2003/10// DO - 10.1016/S0195-6671(03)00072-7 VL - 24 IS - 5 SP - 569-588 SN - 1095-998X KW - Cretaceous KW - Sahara KW - greenhouse climates KW - tropical terrestrial ecosystems KW - oceanic influences KW - dinosaurs ER - TY - JOUR TI - Band offset measurements of the Si3N4/GaN (0001) interface AU - Cook, TE AU - Fulton, CC AU - Mecouch, WJ AU - Davis, RF AU - Lucovsky, G AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy were used to measure electronic states as Si3N4 was deposited on clean GaN (0001) surfaces. The n-type (2×1018) and p-type (1×1017) GaN surfaces were atomically cleaned in NH3 at 860 °C, and the n-and p-type surfaces showed upward band bending of ∼0.2±0.1 eV and downward band bending of 1.1±0.1 eV, respectively, both with an electron affinity of 3.1±0.1 eV. Layers of Si (∼0.2 nm) were deposited on the clean GaN and nitrided using an electron cyclotron resonance N2 plasma at 300 °C and subsequently annealed at 650 °C for densification into a Si3N4 film. Surface analysis was performed after each step in the process, and yielded a valence band offset of 0.5±0.1 eV. Both interfaces exhibited type II band alignment where the valence band maximum of GaN lies below that of the Si3N4 valence band. The conduction band offset was deduced to be 2.4±0.1 eV, and a change of the interface dipole of 1.1±0.1 eV was observed for Si3N4/GaN interface formation. DA - 2003/9/15/ PY - 2003/9/15/ DO - 10.1063/1.1601314 VL - 94 IS - 6 SP - 3949-3954 SN - 0021-8979 ER - TY - JOUR TI - An overview of the KamLAND experiment AU - Markoff, D. M. T2 - Journal of Physics. G, Nuclear and Particle Physics DA - 2003/// PY - 2003/// VL - 29 IS - 8 SP - 1481-1484 ER - TY - JOUR TI - Zone methods and the fermion sign problem AU - Lee, D T2 - NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS AB - We review a recently proposed approach to the problem of alternating signs for fermionic many body Monte Carlo simulations in finite temperature simulations. We derive an estimate for fermion wandering lengths and introduce the notion of permutation zones, special regions of the lattice where identical fermions may interchange and outside of which they may not. Using successively larger permutation zones, one can extrapolate to obtain thermodynamic observables in regimes where direct simulation is impossible. DA - 2003/5// PY - 2003/5// DO - 10.1016/S0920-5632(03)01736-5 VL - 119 SP - 979-981 SN - 0920-5632 ER - TY - JOUR TI - The RHIC gold rush AU - Schaefer, Thomas T2 - Physics World AB - What happens to ordinary matter as you heat it to higher and higher temperatures, or compress it to greater and greater densities? This simple question underpins a major effort to create extreme conditions in the lab, which has recently taken the shape of the Relativistic Heavy Ion Collider (RHIC). This machine has been colliding gold nuclei since 2000, and has produced tantalizing hints that a new state of matter – the quark–gluon plasma – is created in the reactions. But it has also sparked surprises that are sending researchers back to the drawing board. DA - 2003/// PY - 2003/// DO - 10.1088/2058-7058/16/6/35 VL - 16 IS - 6 SP - 31–35 ER - TY - JOUR TI - Spectroscopy of voltage dependence of oxygen movement in YBa2Cu3O7-δ AU - Huerth, S.H. AU - Hallen, Hans AU - Moeckly, B. T2 - Phys. Rev., B, Condens, Matter Mater. Phys. AB - Injection of few-volt electrons at room temperature can displace oxygen atoms in the lattice of yttrium barium cuprate (YBCO). The metal cladding of a near-field scanning optical microscope (NSOM) probe tip is used as a tunnel electrode for locally injecting the electrons with controlled energies. The NSOM optical signal is used to detect changes in the local oxygen concentration. The data support bond breaking in a Franck-Condon-like effect causing enhanced diffusion of oxygen atoms in the lattice. The voltage dependence is consistent with the band structure of YBCO. DA - 2003/5// PY - 2003/5// DO - 10.1103/PhysRevB.67.180506 VL - 67 IS - 18 SP - 180506 - 1 UR - http://dx.doi.org/10.1103/PhysRevB.67.180506 ER - TY - JOUR TI - Science from detection of neutrinos from supernovae AU - Boyd, RN AU - McLaughlin, GC AU - Murphy, AS AU - Smith, PF T2 - JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS AB - The neutrinos emitted from supernovae contain information about the physics of stellar collapse and of the nature of the neutrinos themselves. Several large detectors exist that will be capable of observing some subset of those neutrinos. In addition, we have designed OMNIS, the Observatory for Multiflavour NeutrInos from Supernovae. OMNIS will detect the neutrinos from (a) neutral-current interactions from νe, νμ, , ντ and , and (b) charged-current interactions from high-momentum νe, with lead nuclei. It will utilize two types of detectors: (1) lead slabs alternating with vertical planes of neutron detectors, in which neutrons produced by neutrino–lead interactions will be detected, and (2) lead perchlorate, in which both the resulting neutrons and Cerenkov light will be detected. OMNIS will measure neutrino masses below 100 eV, provide new information on MSW or vacuum oscillations from νμ/ντ to νe, especially to Θ13, and possibly diagnose the process of collapse to a black hole. It will observe the late-time evolution of the neutrino distributions, and possibly see predicted late-time effects, e.g. a phase transition from neutron-star matter to kaon-condensed matter or quark matter. OMNIS is also sensitive to some modes of nucleon decay that should make it possible to improve significantly on present limits for those modes. Of crucial importance to OMNIS is an experiment, using neutrinos from a stopped pion beam, to determine the flavour and energy-dependent response of lead to neutrinos. This will provide important input into cross section calculations for which few data currently exist. We plan to perform this experiment using one of the lead perchlorate detector modules from OMNIS. DA - 2003/11// PY - 2003/11// DO - 10.1088/0954-3899/29/11/009 VL - 29 IS - 11 SP - 2543-2567 SN - 1361-6471 ER - TY - JOUR TI - Missing level corrections in nuclear resonances AU - Agvaanluvsan, U AU - Mitchell, GE AU - Shriner, JF AU - Pato, MP T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB - Neutron and proton resonances provide detailed level density information. Due to experimental limitations some fraction of the resonances are not observed, and this missing fraction must be determined. The standard correction for missing levels uses the experimental widths and the Porter–Thomas distribution. Analysis of the spacing distribution should yield equivalent information. A general expression for an imperfect spacing distribution (with a fraction of levels randomly missing) was obtained with the maximum entropy principle. This formulation was tested extensively with numerical data and then applied to proton and neutron resonance data sets. Since in Random Matrix Theory the widths and spacings are not correlated, this method complements the conventional approach that considers only the widths. The two analysis methods are compared. DA - 2003/2/11/ PY - 2003/2/11/ DO - 10.1016/S0168-9002(02)02144-7 VL - 498 IS - 1-3 SP - 459-469 SN - 1872-9576 KW - nuclear level densities KW - random matrices KW - neutron resonances KW - proton resonances ER - TY - JOUR TI - Low temperature semiconductor surface passivation for nanoelectronic device applications AU - Bae, C AU - Lucovsky, G T2 - SURFACE SCIENCE AB - Abstract A low temperature remote plasma assisted oxidation (RPAO) process for interface formation and passivation has been extended from Si and SiC to GaN. The process, which can be applied to nanoscale structures including quantum dots and wires, provides excellent control of ultra-thin interfacial layers which passivate the GaN substrate, preventing a parasitic or subcutaneous oxidation of the substrate during plasma deposition of SiO 2 . This remote plasma processing for GaN-dielectric heterostructures includes: (i) an in situ nitrogen plasma surface clean, (ii) RPAO for formation of an interfacial GaO x transition region between the GaN and deposited dielectric, and (iii) a remote plasma enhanced chemical vapor deposition of an SiO 2 dielectric. DA - 2003/6/10/ PY - 2003/6/10/ DO - 10.1016/S0039-6028(03)00181-X VL - 532 SP - 759-763 SN - 0039-6028 KW - plasma processing KW - Auger electron spectroscopy KW - semiconductor-insulator interfaces KW - interface states ER - TY - JOUR TI - Instantons and scalar multiquark states: From small to large N-c AU - Schafer, T T2 - PHYSICAL REVIEW D AB - We study scalar $(\overline{q}q)$ and $(\overline{q}{q)}^{2}$ correlation functions in the instanton liquid model. We show that the instanton liquid supports a light scalar-isoscalar (sigma) meson, and that this state is strongly coupled to both $(\overline{q}q)$ and $(\overline{q}{q)}^{2}.$ The scalar-isovector ${a}_{0}$ meson, on the other hand, is heavy. We also show that these properties are specific to QCD with three colors. In the large ${N}_{c}$ limit the scalar-isoscalar meson is not light, and it is mainly coupled to $(\overline{q}q).$ DA - 2003/12// PY - 2003/12// DO - 10.1103/physrevd.68.114017 VL - 68 IS - 11 SP - SN - 2470-0029 UR - http://inspirehep.net/record/628192 ER - TY - JOUR TI - Gold Schottky contacts on oxygen plasma-treated, n-type ZnO(000(1)over-bar) AU - Coppa, BJ AU - Davis, RF AU - Nemanich, RJ T2 - APPLIED PHYSICS LETTERS AB - Reverse bias current–voltage measurements of ∼100-μm-diameter gold Schottky contacts deposited on as-received, n-type ZnO(0001̄) wafers and those exposed for 30 min to a remote 20% O2/80% He plasma at 525±20 °C and cooled either in vacuum from 425 °C or the unignited plasma gas have been determined. Plasma cleaning resulted in highly ordered, stoichiometric, and smooth surfaces. Contacts on as-received material showed μA leakage currents and ideality factors &gt;2. Contacts on plasma-cleaned wafers cooled in vacuum showed ∼36±1 nA leakage current to −4 V, a barrier height of 0.67±0.05 eV, and an ideality factor of 1.86±0.05. Cooling in the unignited plasma gas coupled with a 30 s exposure to the plasma at room temperature resulted in decreases in these parameters to ∼20 pA to −7 V, 0.60±0.05 eV, and 1.03±0.05, respectively. Differences in the measured and theoretical barrier heights indicate interface states. (0001) and (0001̄) are used in this letter to designate the polar zinc- and oxygen-terminated surfaces, respectively. DA - 2003/1/20/ PY - 2003/1/20/ DO - 10.1063/1.1536264 VL - 82 IS - 3 SP - 400-402 SN - 0003-6951 ER - TY - JOUR TI - Effective potentials in the integral quantum Hall effect AU - Lado, F. T2 - Physical Review. B, Condensed Matter and Materials Physics DA - 2003/// PY - 2003/// VL - 67 IS - 24 SP - 245322-1 ER - TY - JOUR TI - Comparison of student performance using web and paper-based homework in college-level physics AU - Bonham, SW AU - Deardorff, DL AU - Beichner, RJ T2 - JOURNAL OF RESEARCH IN SCIENCE TEACHING AB - Abstract Homework gives students an opportunity to practice important college‐level physics skills. A switch to Web‐based homework alters the nature of feedback received, potentially changing the pedagogical benefit. Calculus‐ and algebra‐based introductory physics students enrolled in large paired lecture sections at a public university completed homework of standard end‐of‐the‐chapter exercises using either the Web or paper. Comparison of their performances on regular exams, conceptual exams, quizzes, laboratory, and homework showed no significant differences between groups; other measures were found to be strong predictors of performance. This indicates that the change in medium itself has limited effect on student learning. Ways in which Web‐based homework could enable exercises with greater pedagogical value are discussed. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 1050–1071, 2003 DA - 2003/12// PY - 2003/12// DO - 10.1002/tea.10120 VL - 40 IS - 10 SP - 1050-1071 SN - 0022-4308 ER - TY - JOUR TI - Chandra detection of a pulsar wind nebula associated with supernova remnant 3C 396 AU - Olbert, CM AU - Keohane, JW AU - Arnaud, KA AU - Dyer, KK AU - Reynolds, SP AU - Safi-Harb, S T2 - ASTROPHYSICAL JOURNAL AB - We present a 100 ks observation of the Galactic supernova remnant 3C 396 (G39.2-0.3) with the Chandra X-Ray Observatory that we compare with a 20 cm map of the remnant from the Very Large Array. In the Chandra images, a nonthermal nebula containing an embedded pointlike source is apparent near the center of the remnant that we interpret as a synchrotron pulsar wind nebula surrounding a yet undetected pulsar. From the 2-10 keV spectrum for the nebula [NH = (5.3 ± 0.9) × 1022 cm-2, Γ = 1.5 ± 0.3] we derive an unabsorbed X-ray flux of SX = 1.62 × 10-12 ergs cm-2 s-1, and from this we estimate the spin-down power of the neutron star to be = 7.2 × 1036 ergs s-1. The central nebula is morphologically complex, showing bent, extended structure. The radio and X-ray shells of the remnant correlate poorly on large scales, particularly on the eastern half of the remnant, which appears very faint in X-ray images. At both radio and X-ray wavelengths, the western half of the remnant is substantially brighter than the eastern half. DA - 2003/7/20/ PY - 2003/7/20/ DO - 10.1086/377348 VL - 592 IS - 1 SP - L45-L48 SN - 0004-637X KW - ISM : individual (G39.2-0.3) KW - pulsars : general KW - stars : neutron KW - supernova remnants ER - TY - JOUR TI - Calibrated NEXAFS spectra of some common polymers AU - Dhez, O AU - Ade, H AU - Urquhart, SG T2 - JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA AB - Near edge X-ray absorption fine structure (NEXAFS) microscopy has evolved into a powerful characterization tool for polymeric materials. The foundation of this utility depends crucially on the sensitivity of NEXAFS to the specific chemical structure of the polymer. Furthermore, for quantitative compositional analysis, reliable reference spectra with known energy resolution and calibrated energy scale are required. We report a set of NEXAFS spectra from 24 common polymers that represent a range of chemical functionalities in order to create a database of calibrated polymer NEXAFS spectra to be used for compositional analysis. These spectra illustrate the sensitivity of NEXAFS spectroscopy to the polymer composition, illustrating the potential of NEXAFS for chemical analysis. DA - 2003/1// PY - 2003/1// DO - 10.1016/S0368-2048(02)00237-2 VL - 128 IS - 1 SP - 85-96 SN - 0368-2048 KW - NEXAFS KW - polymers KW - energy calibration KW - reference spectra ER - TY - JOUR TI - Big bang nucleosynthesis and CMB constraints on dark energy AU - Kneller, J. P. AU - Steigman, G. T2 - Physical Review. D, Particles and Fields DA - 2003/// PY - 2003/// VL - 67 IS - 6 SP - 063501-1 ER -