TY - ER - TY - JOUR TI - Ultra-Cold Neutron Production from Solid Deuterium AU - A, D. AU - Anaya, J. M. AU - Mortensen), R. AU - Marek, L. AU - Pasayuk, E. AU - Garcia, A. AU - Fujikawa, B. T2 - Bulletin of the American Physical Society DA - 1999/// PY - 1999/// VL - 44 SP - 989 ER - TY - SOUND TI - Progress Towards a Measurement of the Neutron Beta-Asymmetry Using Ultra-cold Neutrons AU - Young, A.R. DA - 1999/6// PY - 1999/6// ER - TY - SOUND TI - Testing of the Electroweak Standard Model Using Ultra-Cold Neutrons AU - Young, A.R. DA - 1999/// PY - 1999/// ER - TY - JOUR TI - Measurements of Neutron Beta-decay Using Ultra-Cold Neutrons Produced at a Spallation Source AU - Young, A.R. AU - Garcia, A. T2 - Bulletin of the American Physical Society DA - 1999/// PY - 1999/// VL - 44 SP - 17 ER - TY - JOUR TI - A Calibration Device for Low-Energy Electrons AU - Yuan, J. AU - Garcia, A. AU - Miyachi, T. AU - Young, A.R. T2 - Bulletin of the American Physical Society DA - 1999/// PY - 1999/// VL - 44 SP - 41 ER - TY - JOUR TI - Calibration System and Prototypes for Electron Detection for the UCN A Experiment AU - Ito, T. AU - Filippone, B. AU - Jones, C. AU - McKeown, R. AU - Yuan, J. AU - Young, A.R. AU - Hoedl, S. AU - Liu, C.-Y. AU - Smith, D. AU - Soyama, K. AU - Bowles, T. AU - Brun, T. AU - Fowler, M. AU - Hill, R. AU - Hime, A. AU - Hogan, G. AU - Lamoreaux, S. AU - Morris, C. AU - Saunders, A. AU - Seestrom, S. AU - Walstrom, P. AU - Alduschenkov, A. AU - Kharitonov, A. AU - Lassakov, M. AU - Rudnex, Y. AU - Serebrov, A. AU - Vasilev, A. AU - Geltenbort, P. AU - Kitagaki, T. AU - Asahi, K. AU - Hino, M. AU - Kawai, T. AU - Utsuro, M. AU - Garcia, A. AU - Makela, M. AU - Vogelaar, R.B. AU - Miyachi, T. T2 - Bulletin of the American Physical Society DA - 1999/// PY - 1999/// VL - 44 SP - 41 ER - TY - JOUR TI - A Solid Deuterium Source for Ultra-Cold Neutrons AU - Saunders, A. AU - Young, A. T2 - Bulletin of the American Physical Society DA - 1999/// PY - 1999/// VL - 44 SP - 40 ER - TY - JOUR TI - Analysis of Ultra-Cold Neutron Production from a Solid-Deuterium Source AU - Smith, D.A. AU - Young, A.R. AU - Heodl, S. AU - Liu, C.-Y. AU - Bowles, T. AU - Hill, R.E. AU - Hogan, G. AU - Lamoreaux, S. AU - Marek, L. AU - Morris, C.L. AU - Sattelberger, J.A. AU - Saunders, A. AU - Seestrom, S.J. AU - Teasdale, W. AU - Filippone, B. AU - Yuan, J. AU - Ito, T. AU - Geltenbort, P. T2 - Bulletin of the American Physical Society DA - 1999/// PY - 1999/// VL - 44 SP - 41 ER - TY - JOUR TI - Positron-electron pairs produced in heavy-ion collisions AU - Ahmad, I. AU - Austin, S.M. AU - Back, B.B. AU - Betts, R.R. AU - Calaprice, F.P. AU - Chan, K.C. AU - Chishti, A. AU - Conner, C.M. AU - Dunford, R.W. AU - Fox, J.D. AU - Freedman, S.J. AU - Freer, M. AU - Gazes, S.B. AU - Hallin, A.L. AU - Happ, Th. AU - Henderson, D. AU - Kaloskamis, N.I. AU - Kashy, E. AU - Kutschera, W. AU - Last, J. AU - Lister, C.J. AU - Liu, M. AU - Maier, M.R. AU - Mercer, D.M. AU - Mikolas, D. AU - Perera, P..A.A. AU - Rhein, M.D. AU - Roa, D.E. AU - Schiffer, J.P. AU - Trainor, T.A. AU - Wilt, P. AU - Winfield, J.S. AU - Wolanski, M. AU - Wolfs, F.L.H. AU - Wuosmaa, A.H. AU - Young, A.R. AU - Yurkon, J.E. T2 - Physical Review C AB - The production of positron-electron pairs in collisions of 238U+232Th at 5.95 MeV/nucleon, and of 238U+181Ta at 5.95, 6.1, and 6.3 MeV/nucleon, has been studied with the APEX spectrometer at Argonne National Laboratory. Several analyses have been performed to search for sharp structures in sum-energy spectra for positron-electron pairs. Such features have been reported in previous experiments. No statistically convincing evidence for such behavior is observed in the present data.Received 25 November 1998DOI:https://doi.org/10.1103/PhysRevC.60.064601©1999 American Physical Society DA - 1999/12// PY - 1999/12// DO - 10.1103/PhysRevC.60.064601 VL - 60 IS - 6 SP - 064601 ER - TY - JOUR TI - Light narrowing of rubidium magnetic-resonance lines in high-pressure optical-pumping cells AU - Appelt, S. AU - Ben-Amar Baranga, A. AU - Young, A. R. AU - Happer, W. T2 - Physical Review A AB - We report on some unusual magnetic-resonance phenomena of optically pumped Rb vapor in high-pressure gas cells. When Rb-Rb spin exchange is the fastest spin-relaxation rate, we observe a considerable narrowing of the magnetic-resonance linewidths with increasing pump-laser power. The experimentally measured Rb magnetic-resonance linewidths are in excellent agreement with a theoretical model, which includes the processes of Rb-He and Rb-Xe spin destruction, Rb-Rb spin exchange, and Rb optical pumping. DA - 1999/3/1/ PY - 1999/3/1/ DO - 10.1103/physreva.59.2078 VL - 59 IS - 3 SP - 2078-2084 J2 - Phys. Rev. A LA - en OP - SN - 1050-2947 1094-1622 UR - http://dx.doi.org/10.1103/physreva.59.2078 DB - Crossref ER - TY - CHAP TI - Chaos Control in Biological Systems AU - Spano, Mark L. AU - Ditto, William L. T2 - Handbook of Chaos Control A2 - Schuster, H.G. AB - This chapter contains sections titled: Introduction Cardiac Dynamics Introduction to ventricular fibrillation Fibrillation as a dynamical state Detection of deterministic dynamics in canine ventricular fibrillation Imaging of the spatiotemporal evolution of ventricular fibrillation Control of Chaos in Cardiac Systems Control of isolated cardiac tissue Control of atrial fibrillation in humans Control of Chaos in Brain Tissue DC Field Interactions with Mammalian Neuronal Tissue Summary PY - 1999/// DO - 10.1002/3527607455.ch17 PB - Wiley-VCH SN - 9783527607457 ER - TY - JOUR TI - Chaos at 35,000 feet AU - Ditto, William L. T2 - Industrial Physicist DA - 1999/8// PY - 1999/8// VL - 5 IS - 4 SP - 27–29 ER - TY - CONF TI - InP(001)(2x4): A new type of dimer reconstruction AU - Schmidt, W.G. AU - Bernholc, J. AU - Bechstedt, F. T2 - 24th International Conference on the Physics of Semiconductors A2 - Gershoni, D. C2 - 1999/// C3 - 24th International Conference on the Physics of Semiconductors : Jerusalem, Israel, August 2-7,1998 CY - Jerusalem, Israel DA - 1999/// PY - 1998/8/2/ PB - World Scientific ER - TY - JOUR TI - Atomic Transformations and Quantum Transport in Carbon Nanotubes AU - Bernholc, J. AU - Buongiorno Nardelli, M. AU - Fattebert, J.-L. AU - Orlikowski, D. AU - Roland, C. AU - Rose, F. AU - Zhao, Q. T2 - MRS Online Proceedings: Symposium U – Amorphous & Nanostructured Carbon DA - 1999/// PY - 1999/// DO - 10.1557/proc-593-547 VL - 593 ER - TY - JOUR TI - Importance of the hexadecapole-hexadecapole interaction AU - Davis, E. D. AU - Barrett, B. R. AU - Diallo, A. F. T2 - Physical Review C AB - Motivated by the sensitivity of collective $M1$ excitations to the hexadecapole-hexadecapole interaction, we explore the influence of this and other features of sdgIBM on the ground-state band properties of deformed rare-earth nuclei. We adopt microscopically motivated choices of the Hamiltonian parameters and work within the angular-momentum-projected intrinsic state formalism, deriving analytic expressions for observables in which the dependence on wave functions and parameters of the model is explicit. We find that energies of ground-state band excitations are insensitive to the hexadecapole-hexadecapole interaction. On the other hand, its contribution to the deformation energy term in the nuclear binding energy is substantial. Our results indicate that angular momentum projection is important even for well-deformed nuclei and that at least two g bosons should be utilized in the corresponding sdgIBM calculations. DA - 1999/1/1/ PY - 1999/1/1/ DO - 10.1103/physrevc.59.200 VL - 59 IS - 1 SP - 200-209 J2 - Phys. Rev. C LA - en OP - SN - 0556-2813 1089-490X UR - http://dx.doi.org/10.1103/physrevc.59.200 DB - Crossref ER - TY - JOUR TI - Controlling stochastic resonance AU - Gammaitoni, L. AU - Löcher, M. AU - Bulsara, A. AU - Hänggi, P. AU - Neff, J. AU - Wiesenfeld, K. AU - Ditto, W. AU - Inchiosa, M.E. T2 - Physical Review Letters DA - 1999/// PY - 1999/// VL - 82 IS - 23 SP - 4574-4577 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0000617726&partnerID=MN8TOARS ER - TY - JOUR TI - Computing with distributed chaos AU - Sinha, S. AU - Ditto, W.L. T2 - Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics DA - 1999/// PY - 1999/// VL - 60 IS - 1 SP - 363-377 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-18144376447&partnerID=MN8TOARS ER - TY - JOUR TI - Tunneling processes in quantum chromodynamics AU - Schäfer, Thomas T2 - Phys.Bl. DA - 1999/// PY - 1999/// VL - 55N9 SP - 52-55 UR - http://inspirehep.net/record/509672 ER - TY - JOUR TI - Quark description of hadronic phases AU - Schäfer, Thomas AU - Wilczek, Frank T2 - Phys.Rev.D AB - We extend our proposal that major universality classes of hadronic matter can be understood, and in favorable cases calculated, directly in the microscopic quark variables, to allow for a splitting between strange and light quark masses. A surprisingly simple but apparently viable picture emerges, featuring essentially three phases, distinguished by whether strangeness is conserved (standard nuclear matter), conserved modulo 2 (hypernuclear matter), or locked to color (color flavor locking). These are separated by sharp phase transitions. There is also, potentially, a quark phase matching hadronic K condensation. The smallness of the secondary gap in two-flavor color superconductivity corresponds to the disparity between the primary dynamical energy scales of QCD and the much smaller energy scales of nuclear physics. DA - 1999/3// PY - 1999/3// DO - 10.1103/PhysRevD.60.074014 VL - 60 SP - 074014 UR - http://inspirehep.net/record/497415 ER - TY - CONF TI - Color superconductivity: Continuity of quark and hadron matter, the role of the strange quark mass, and perturbative results AU - Schäfer, Thomas AB - We summarize some recent results on the structure of QCD at very high baryon density. C2 - 1999/5// C3 - Nucl.Phys.A DA - 1999/5// DO - 10.1016/S0375-9474(99)85102-1 VL - 661 SP - 621-624 UR - http://inspirehep.net/record/506661 ER - TY - JOUR TI - Superconductivity from perturbative one gluon exchange in high density quark matter AU - Schäfer, Thomas AU - Wilczek, Frank T2 - Phys.Rev.D AB - We study color superconductivity in QCD at an asymptotically large chemical potential. In this limit, pairing is dominated by perturbative one-gluon exchange. We derive the Eliashberg equation for the pairing gap and solve this equation numerically. Taking into account both magnetic and electric gluon exchanges, we find $\ensuremath{\Delta}\ensuremath{\sim}{g}^{\ensuremath{-}5}\mathrm{exp}(\ensuremath{-}c/g)$ with $c=3{\ensuremath{\pi}}^{2}/\sqrt{2},$ verifying a recent result by Son. For chemical potentials that are of physical interest, $\ensuremath{\mu}<1 \mathrm{GeV},$ the calculation ceases to be reliable quantitatively, but our results suggest that the gap can be as large as 100 MeV. DA - 1999/6// PY - 1999/6// DO - 10.1103/PhysRevD.60.114033 VL - 60 SP - 114033 UR - http://inspirehep.net/record/502412 ER - TY - JOUR TI - High density quark matter and the renormalization group in QCD with two and three flavors AU - Schäfer, Thomas AU - Wilczek, Frank T2 - Phys.Lett.B AB - We consider the most general four fermion operators in QCD for two and three massless flavors and study their renormalization in the vicinity of the Fermi surface. We show that, asymptotically, the largest coupling corresponds to scalar diquark condensation. Asymptotically the direct and iterated (molecular) instanton interactions become equal. We provide simple arguments for the form of the operators that diagonalize the evolution equations. Some solutions of the flow equations exhibit instabilities arising out of purely repulsive interactions. DA - 1999/10// PY - 1999/10// DO - 10.1016/S0370-2693(99)00162-8 VL - 450 SP - 325-331 UR - http://inspirehep.net/record/478567 ER - TY - JOUR TI - Continuity of quark and hadron matter AU - Schäfer, Thomas AU - Wilczek, Frank T2 - Phys.Rev.Lett. AB - We review, clarify, and extend the notion of color-flavor locking. We present evidence that for three degenerate flavors the qualitative features of the color-flavor locked state, reliably predicted for high density, match the expected features of hadronic matter at low density. This provides, in particular, a controlled, weak-coupling realization of confinement and chiral symmetry breaking in this (slight) idealization of QCD. DA - 1999/11// PY - 1999/11// DO - 10.1103/PhysRevLett.82.3956 VL - 82 SP - 3956-3959 UR - http://inspirehep.net/record/479903 ER - TY - JOUR TI - Room-temperature Coulomb-blockade-dominated transport in gold nanocluster structures AU - Clarke, L AU - Wybourne, M N AU - Brown, L O AU - Hutchison, J E AU - Yan, M AU - Cai, S X AU - Keana, J F W T2 - Semiconductor Science and Technology AB - In this paper we discuss the near-room-temperature electrical transport characteristics of structures made from ligand-stabilized metal clusters. The structures show threshold behaviour, nonlinear current-voltage characteristics and radio-frequency-induced plateaux consistent with Coulomb-blockade-dominated transport in disordered arrays of metal dots. Samples having triphenylphosphine and octadecanethiol ligand shells are found to have a 3 orders of magnitude difference in current above threshold. We discuss a possible explanation for this observation. DA - 1999/1/1/ PY - 1999/1/1/ DO - 10.1088/0268-1242/13/8a/033 VL - 13 IS - 8A SP - A111-A114 ER - TY - JOUR TI - Fabrication and electrical transport characteristics of low-dimensional nanoparticle arrays organized by biomolecular scaffolds AU - Wybourne, M.N. AU - Hutchison, J.E. AU - Clarke, L. AU - Brown, L.O. AU - Mooster, J.L. T2 - Microelectronic Engineering AB - We report the use of a biopolymer scaffold in the nanofabrication of low-dimensional arrays of gold nanoparticles. The room-temperature current-voltage dependence shows threshold behavior characteristic of Coulomb-blockade. Above threshold the current varies linearly with voltage which suggests one-dimensional behavior. Capacitance estimates are consistent with transport through a disordered chain containing a minimum of 200 nanoparticles. DA - 1999/6// PY - 1999/6// DO - 10.1016/s0167-9317(99)00147-1 VL - 47 IS - 1-4 SP - 55-57 ER - TY - CONF TI - Physical channel modeling, adaptive prediction and transmitter diversity for flat fading mobile channel AU - Hu, S. AU - Hallen, H. AU - Duel-Hallen, A. AB - Deterministic modeling of flat fading wireless channels using the method of images is presented. The models identify typical and worst-case channel parameter variation rates and yield datasets of channel strength vs. position, which are used to test a long-range adaptive prediction algorithm previously presented by the authors. Our physical insights and unique long-range prediction capability for the fast fading can be used in conjunction with space diversity-including novel transmitter diversity schemes for a single receiving antenna-or adaptive modulation to significantly reduce or eliminate the effects of deep fades in wireless communications. C2 - 1999/// C3 - 1999 2nd IEEE Workshop on Signal Processing Advances in Wireless Communications (Cat. No.99EX304) CY - Piscataway, NJ, USA DA - 1999/// DO - 10.1109/SPAWC.1999.783099 SP - 387 - 90 UR - http://dx.doi.org/10.1109/SPAWC.1999.783099 ER - TY - CONF TI - Transmitter antenna diversity and adaptive signaling using long range prediction for fast fading DS/CDMA mobile radio channels AU - Hu, Shengquan AU - Eyceoz, Tugay AU - Duel-Hallen, Alexandra AU - Hallen, Hans AB - Previously, the authors introduced a novel algorithm for long range prediction of flat fading channels that can reliably predict future fading coefficients far beyond the coherence time. This prediction capability provides enabling technology for power and bandwidth efficient adaptive modulation and coding methods. In this paper, we extend our results to the direct sequence code division multiple access (DS/CDMA) channels. It is demonstrated that frequency selective channels encountered in CDMA can also be predicted far ahead, and that the proposed prediction methods can be combined with RAKE receivers. In addition, we utilize prediction to improve performance of the selective transmitter diversity system proposed for the third generation CDMA. C2 - 1999/// C3 - IEEE Wireless Communications and Networking Conference, WCNC CY - New Orleans, LA, United states DA - 1999/// DO - 10.1109/WCNC.1999.796779 VL - 2 SP - 824 - 828 UR - http://dx.doi.org/10.1109/WCNC.1999.796779 N1 - – An invited paper RN - – An invited paper ER - TY - CONF TI - Near-Field Scanning Optical Microscopy of Electromigration in YBCO AU - Huerth, Suzanne AU - Taylor, Michael AU - Paesler, Michael AU - Hallen, Hans C2 - 1999/// C3 - Proceedings of the Second Asia-Pacific Workshop on Near-field Optics CY - Beijing, China DA - 1999/// ER - TY - CONF TI - Adaptive prediction, tracking and power adjustment for frequency non-selective fast fading channels AU - Eyceoz, T. AU - Hu, S. AU - Duee-Hallen, A. AU - Hallen, H. AB - Previously, the authors introduced a novel algorithm for long range prediction of fading channels. This algorithm finds the linear minimum mean squared error (MMSE) estimate of the future fading coefficients given a fixed number of previous observations. In this paper, we show that the superior performance of this algorithm is due to its lower sampling rate relative to the conventional (data rate) methods of fading prediction. We also enhance the algorithm by an adaptive prediction and tracking method that increases accuracy and maintains the robustness of long-term prediction as the physical channel parameters vary. Finally, we show that large improvements in the bit error rate (BER) are possible when the proposed prediction method is used. In particular, analysis of the channel inversion with threshold technique is presented to demonstrate that the BER can be reduced to the level of and beyond the additive white Gaussian noise (AWGN) channel. C2 - 1999/// C3 - 1999 IEEE Communications Theory Mini-Conference (Cat. No.99EX352) CY - Piscataway, NJ, USA DA - 1999/// DO - 10.1109/CTMC.1999.790226 SP - 1 - 5 UR - http://dx.doi.org/10.1109/CTMC.1999.790226 ER - TY - CONF TI - Adaptive Power Control Using Long Range Prediction for Realistic Fast Fading Channel Models and Measured Data AU - Hu, S. AU - Hallen, H. AU - Duel-Hallen, A. C2 - 1999/// C3 - 5th International Symposium on Communication Theory and Application ISCTA'99 DA - 1999/// SP - 118-120 UR - https://pdfs.semanticscholar.org/c77a/2149dd49861fd5f3c1c54db7a23fa549f0d6.pdf ER - TY - JOUR TI - Experimental study of photon-echo size in optically thick media AU - Wang, T. AU - Greiner, C. AU - Bochinski, J. R. AU - Mossberg, T. W. T2 - Physical Review A AB - We have studied the effect of generative-pulse amplitude, spatial profile, and temporal character as well as medium optical thickness on the power of photon and stimulated echoes. Working in atomic Yb vapor, photon echoes are observed that, absent material relaxation, are more powerful than the first generative pulse, thereby exceeding typically expected photon-echo powers by approximately two orders of magnitude. Factors crucial to the generation of powerful echoes identified through Maxwell-Bloch simulation are experimentally confirmed. DA - 1999/8/1/ PY - 1999/8/1/ DO - 10.1103/physreva.60.r757 VL - 60 IS - 2 SP - R757-R760 ER - TY - JOUR TI - Radiative decay of the metastable He2(a 3∑u +) molecule in liquid helium AU - McKinsey, D.N. AU - Brome, C.R. AU - Butterworth, J.S. AU - Dzhosyuk, S.N. AU - Huffman, P.R. AU - Mattoni, C.E.H. AU - Doyle, J.M. AU - Golub, R. AU - Habicht, K. T2 - Physical Review A - Atomic, Molecular, and Optical Physics DA - 1999/// PY - 1999/// VL - 59 IS - 1 SP - 200-204 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0003327035&partnerID=MN8TOARS ER - TY - JOUR TI - Video-based labs for introductory physics courses AU - Beichner, R. AU - Abbott, D. T2 - Journal of College Science Teaching DA - 1999/// PY - 1999/// VL - 29 IS - 1 SP - 101-104 ER - TY - PAT TI - Thin film optical measurement system and method with calibrating ellipsometer AU - Aspnes, D. E. AU - Opsal, J. AU - Faton, J. T. C2 - 1999/// DA - 1999/// PY - 1999/// ER - TY - PAT TI - Broadband spectroscopic rotating compensator ellipsometer AU - Aspnes, D. E. AU - Opsal, J. C2 - 1999/// DA - 1999/// PY - 1999/// ER - TY - CHAP TI - Test bank to accompany College physics (5th ed.) AU - Beichner, R. T2 - College physics A2 - Serway, R. A2 - Faughn, J. PY - 1999/// PB - Fort Worth : Saunders College Pub SN - 003023798X ER - TY - BOOK TI - Essentials of educational technology AU - Schwartz, J. E. AU - Beichner, R. J. DA - 1999/// PY - 1999/// PB - Boston: Allyn and Bacon SN - 9780205277001 ER - TY - CONF TI - Quantum confinement of above-band-bap transitions in Ge quantum dots embedded in an Al2O3 or AIN matrix AU - Teng, C. W. AU - Muth, J. F. AU - Kolbas, R. M. AU - Hassan, K. M. AU - Sharma, A. K. AU - Kvit, A. AU - Narayan, J. A2 - J. Piqueras, T. Sekiguchi A2 - Unlu, M. S. C2 - 1999/// C3 - Optical microstructural characterization of semiconductors (Materials Research Society proceedings, vol. 588) CN - QC610.9 .O67 2000 DA - 1999/// PB - Pittsburgh, Pa.: Materials Research Society ER - TY - JOUR TI - Self-energy effects in the optical anisotropy of GaP(001) AU - Schmidt, WG AU - Fattebert, JL AU - Bernholc, J AU - Bechstedt, F T2 - SURFACE REVIEW AND LETTERS AB - We calculate the reflectance anisotropy for GaP(001)(2×4) surfaces using a real-space multigrid method and ab initio pseudopotentials. Our results obtained within DFT-LDA show good qualitative agreement with recent experiments. This holds in particular for the stoichiometric trends. A strong negative anisotropy at low photon energies is linked to the formation of Ga–Ga bonds along the [110] direction. There are discrepancies, however, with respect to the line shape and the energetic positions of characteristic peaks. Substantial improvement is achieved by using a numerically efficient GW approach with approximations for local-field effects and dynamical screening. We find that the spectral features related to transitions between surface perturbed bulk wave functions are more strongly affected by self-energy corrections than anisotropies directly linked to surface electronic states. DA - 1999/12// PY - 1999/12// DO - 10.1142/S0218625X99001281 VL - 6 IS - 6 SP - 1159-1165 SN - 0218-625X ER - TY - JOUR TI - Stability of Si-O-F low-K dielectrics: attack by water molecules as function of near-neighbor Si-F bonding arrangements AU - Yang, H AU - Lucovsky, G T2 - JOURNAL OF NON-CRYSTALLINE SOLIDS AB - Abstract Ab initio configuration interaction calculations have been previously used to account for the relatively large decreases (∼20%) in the static dielectric constant of Si–O–F alloys with for F alloy atom concentrations of ∼10 at.%. This study addresses the stability of these alloy films with respect to attack of Si–F bonds by water molecules. The present calculations show that the reactions of isolated Si–F with water molecules differ from the reactions of nearest-neighbor Si–F groups with water molecules. For example, hydrogen attachment of water to two Si–F groups has a bonding energy of ∼0.5 eV, whereas attachment to an isolated Si–F group has an attachment energy smaller by more than a factor of 6. Combining these calculations for interactions with H 2 O with a statistical model of bonding in the alloy films, an upper limit for chemically stable F-corporation has been determined to be ∼11 at.% F, which corresponds to the static dielectric constant of ∼3.3. DA - 1999/9/1/ PY - 1999/9/1/ DO - 10.1016/S0022-3093(99)00387-7 VL - 254 SP - 128-133 SN - 0022-3093 ER - TY - JOUR TI - Reduction of the transition temperature of C54TiSi(2) through a Ta interlayer AU - Jung, B. AU - Kim, Y. D. AU - Jeon, H. AU - Yang, W. AU - Nemanich, R. J. T2 - Journal of the Korean Physical Society DA - 1999/// PY - 1999/// VL - 35 IS - 1999 Dec. SP - S769-773 ER - TY - JOUR TI - Raman scattering of tetrahedrally-bonded amorphous carbon deposited at oblique angles AU - Park, M AU - Camphausen, SM AU - Myers, AF AU - Barletta, PT AU - Sakhrani, V AU - Bergman, L AU - Nemanich, RJ AU - Cuomo, JJ T2 - MATERIALS LETTERS AB - Amorphous carbon (txa-C1−x) films were prepared by filtered cathodic arc deposition (FCAD). The films were deposited on p-type Si (111). The angle of beam incidence was varied from 0° to 75° with respect to the substrate normal. Micro-Raman spectroscopy, electron energy loss spectroscopy (EELS), and transmission electron microscopy (TEM) were carried out for sample analysis. It was found that the position of the G peak shifts to a higher wave number region as the angle of incidence increases. This means that the sp2/sp3 ratio increases with increasing angle. This conclusion is supported by EELS. The film deposited at an angle of 75° exhibits a columnar structure with alternating high and low carbon density regions. DA - 1999/12// PY - 1999/12// DO - 10.1016/S0167-577X(99)00135-4 VL - 41 IS - 5 SP - 229-233 SN - 1873-4979 KW - amorphous carbon KW - filtered arc depositors KW - Raman scattering KW - electron energy loss spectroscopy ER - TY - JOUR TI - Parity nonconservation in Pd-106 and Pd-108 neutron AU - Crawford, BE AU - Bowman, JD AU - Delheij, PPJ AU - Haseyama, T AU - Knudson, JN AU - Lowie, LY AU - Masaike, A AU - Matsuda, Y AU - Mitchell, GE AU - Penttila, SI AU - Postma, H AU - Roberson, NR AU - Seestrom, SJ AU - Sharapov, EI AU - Stephenson, SL AU - Yuan, VW T2 - PHYSICAL REVIEW C AB - Parity nonconservation (PNC) has been studied in the neutron p-wave resonances of ${}^{106}\mathrm{Pd}$ and ${}^{108}\mathrm{Pd}$ in the energy range of 20 to 2000 eV. Longitudinal asymmetries in p-wave capture cross sections are measured using longitudinally polarized neutrons incident on $\ensuremath{\sim}20\ensuremath{-}\mathrm{g}$ metal-powder targets at LANSCE. A CsI $\ensuremath{\gamma}$-ray detector array measures capture cross section asymmetries as a function of neutron energy which is determined by the neutron time-of-flight method. A total of 21 p-wave resonances in ${}^{106}\mathrm{Pd}$ and 21 p-wave resonances in ${}^{108}\mathrm{Pd}$ were studied. One statistically significant PNC effect was observed in ${}^{106}\mathrm{Pd},$ and no effects were observed in ${}^{108}\mathrm{Pd}.$ For ${}^{106}\mathrm{Pd}$ a weak spreading width of ${\ensuremath{\Gamma}}_{w}{=34}_{\ensuremath{-}28}^{+47}\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7} \mathrm{eV}$ was obtained. For ${}^{108}\mathrm{Pd}$ an upper limit on the weak spreading width of ${\ensuremath{\Gamma}}_{w}<12\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7} \mathrm{eV}$ was determined at the 68% confidence level. DA - 1999/11// PY - 1999/11// DO - 10.1103/physrevc.60.055503 VL - 60 IS - 5 SP - SN - 2469-9993 ER - TY - JOUR TI - Multifrequency studies of bright radio supernova remnants. III. X-ray and radio AU - Dyer, KK AU - Reynolds, SP T2 - ASTROPHYSICAL JOURNAL AB - Radio-bright, presumably young supernova remnants offer the opportunity of studying strong-shock physics and the nature of the interaction of ejected material with the surrounding medium. The relation between radio and X-ray morphology varies considerably among supernova remnants, with important implications for the physics of the emission processes at different wavelengths. We use Very Large Array (VLA) and Roentgen Satellite (ROSAT) images of the radio-bright supernova remnant 3C 397 (G41.1-0.3) to examine the shock structure in both thermal X-ray emission and nonthermal radio emission. The unusual rectangular morphology can be seen in VLA maps at 20 and 6 cm wavelength at a resolution of 6'' and in ROSAT HRI images. The X-ray images resemble the radio strongly, except for a small, possibly unresolved X-ray hot spot near the center. There is no variation in the X-ray hardness ratio from ROSAT Position Sensitive Proportional Counter data across the remnant, suggesting that at least between 0.4 and 2 keV the interior emission is not different in character from that in the bright shell regions. The remnant is unpolarized at 20 cm and has a mean fractional polarization of 1.5% ± 0.1% at 6 cm. The polarized flux, and polarized fraction, peak inside the remnant at a location not coincident with either an internal maximum in total-intensity radio emission or with the X-ray hot spot. Spectral index maps between 6 and 20 cm do not show any systematic differences associated with interior emission; there appears to be no "plerionic" or pulsar-driven component in 3C 397, at least as normally characterized by high polarization and a flat radio spectrum. Spectral index values spread about the mean by about Δα ~ 0.2, a result consistent with previous work. The steep total-intensity profile off the southwest edge of 3C 397 allows an inference of the upstream electron diffusion coefficient and implies a mean free path for electron scattering shorter than in the general interstellar medium but longer than that similarly inferred for Tycho and SN 1006. A simple analysis based on the observed X-ray flux gives an estimate of the mean density in 3C 397 of about 4 cm-3, which would also be enough to depolarize the 20 cm emission completely, as observed. The remnant age is then of order 103 yr, and the current shock velocity is about 1600 km s-1. Finally, we speculate on possible mechanisms producing the X-ray hot spot. DA - 1999/11/20/ PY - 1999/11/20/ DO - 10.1086/307985 VL - 526 IS - 1 SP - 365-384 SN - 0004-637X KW - polarization KW - radiation mechanisms : nonthermal KW - radio continuum : general KW - shock waves KW - supernova remnants KW - X-rays : general ER - TY - JOUR TI - Iron regulatory element and internal loop/bulge structure for ferritin mRNA studied by cobalt(III) hexammine binding, molecular modeling, and NMR spectroscopy (vol 37, pg 1505, 1998) AU - Gdaniec, Z AU - Sierzputowska-Gracz, H AU - Theil, EC T2 - BIOCHEMISTRY AB - ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionORIGINAL ARTICLEThis notice is a correctionIron Regulatory Element and Internal Loop/Bulge Structure for Ferritin mRNA Studied by Cobalt(III) Hexammine Binding, Molecular Modeling, and NMR SpectroscopyZofia Gdaniec, Hanna Sierzputowska-Gracz, and Elizabeth C. TheilCite this: Biochemistry 1999, 38, 17, 5676Publication Date (Web):April 8, 1999Publication History Published online8 April 1999Published inissue 1 April 1999https://doi.org/10.1021/bi9950746Copyright © 1999 American Chemical SocietyRequest reuse permissions This publication is free to access through this site. Learn MoreArticle Views286Altmetric-Citations5LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (5 KB) Get e-Alertsclose Get e-Alerts DA - 1999/4/27/ PY - 1999/4/27/ DO - 10.1021/bi9950746 VL - 38 IS - 17 SP - 5676-5676 SN - 0006-2960 ER - TY - CHAP TI - Inhomogeneous fluids in an external field AU - Lado, Fred AU - Lomba, E. T2 - New approaches to problems in liquid state theory: Inhomogeneities and phase separation in simple, complex, and quantum fluids (NATO Science Series; Series C, Vol. 529) A2 - Caccamo, J. P. Hansen C. A2 - Stell, G. AB - The Gibbsian N-body density function of a Hamiltonian H N that is rotationally and translationally invariant must itself be rotationally and translationally invariant, as must then also be all reduced n-body density functions of this Hamiltonian. In particular, the one-body density is a constant and the two-body density depends only on relative coordinates. An external field destroys this homogeneity, producing anisotropy or nonuniformity [1, 2], and so makes necessary the joint calculation of the coupled one-body and two-body density functions. A striking if familiar example of the response of a bulk system to an external field is ferromagnetism. We shall use this particular case here to present a general procedure to compute the coupled one-body and two-body density functions of an inhomogeneous classical fluid in an external field. Remarkably, the procedure is no more difficult to carry through than similar calculations for ordinary homogeneous systems. CN - QC138 .N48 1999 PY - 1999/// DO - 10.1007/978-94-011-4564-0_14 SP - 279–291 PB - Dordrecht: Kluwer SN - 0792356705 ER - TY - CHAP TI - Fluids with internal degrees of freedom AU - Lado, Fred T2 - New approaches to problems in liquid state theory: Inhomogeneities and phase separation in simple, complex, and quantum fluids (NATO Science Series; Series C, Vol. 529) A2 - Caccamo, J. P. Hansen C. A2 - Stell, G. AB - The essential core of the modern integral equation approach to liquid state theory was arrived at nearly simultaneously in 1960 by a remarkable number of authors working independently [1], They found that the density expansion of the pair distribution function g(r) of a simple fluid with interatomic potential ϕ(r) could be grouped into infinite subsets of diagrams such that (1) $$ g(r){e^{{\beta \phi (r)}}} = 1 + S(r) + P(r) + B(r) $$ where, in the pictorial electrical language of M. S. Green [2], the diagrams of the series set S(r) resemble series circuits and those of the parallel set P(r) resemble parallel circuits; the remaining bridge set B(r) begins with a diagram that looks like a Wheatstone bridge. Further, the diagrams of P(r) could be summed in direct space to give P(r) = g(r) exp(βϕ(r)) - 1 - ln[g(r) exp(βϕ(r))], while those of S(r) could be summed in Fourier space to yield S(k) = č2(k)/[l-pc(k)], which is the Ornstein-Zernike (OZ) equation in Fourier transform representation. Here, c(r) = h(r) - S(r) is the sum of non-nodal graphs, or direct correlation function, while h(r) = g(r) - 1 is the total correlation function. CN - QC138 .N48 1999 PY - 1999/// DO - 10.1007/978-94-011-4564-0_7 SP - 91–105 PB - Dordrecht: Kluwer SN - 0792356705 ER - TY - JOUR TI - Double polarized neutron-proton scattering and meson-exchange nucleon-nucleon potential models AU - Raichle, BW AU - Gould, CR AU - Haase, DG AU - Seely, ML AU - Walston, , JR AU - Tornow, W AU - Wilburn, WS AU - Penttila, SI AU - Hoffmann, GW T2 - PHYSICAL REVIEW LETTERS AB - We report on polarized beam--polarized target measurements of the spin-dependent neutron-proton total cross-section differences in longitudinal and transverse geometries ( $\ensuremath{\Delta}{\ensuremath{\sigma}}_{L}$ and $\ensuremath{\Delta}{\ensuremath{\sigma}}_{T}$, respectively) between ${E}_{n}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}5$ and 20 MeV. Single-parameter phase-shift analyses were performed to extract the phase-shift mixing parameter ${\ensuremath{\varepsilon}}_{1}$, which characterizes the strength of the nucleon-nucleon tensor interaction at low energies. Consistent with the trend of previous determinations at ${E}_{n}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}25$ and 50 MeV, our values for ${\ensuremath{\varepsilon}}_{1}$ imply a stronger tensor force than predicted by meson-exchange nucleon-nucleon potential models and nucleon-nucleon phase-shift analyses. DA - 1999/10/4/ PY - 1999/10/4/ DO - 10.1103/physrevlett.83.2711 VL - 83 IS - 14 SP - 2711-2714 SN - 0031-9007 ER - TY - JOUR TI - Charge redistribution at GaN-Ga2O3 interfaces: A microscopic mechanism for low defect density interfaces in remote plasma processed MOS devices prepared on polar GaN faces AU - Therrien, R AU - Lucovsky, G AU - Davis, RF T2 - PHYSICA STATUS SOLIDI A-APPLIED RESEARCH AB - Interfacial defect densities, typically two orders of magnitude lower than those usually obtained at [III–V]-dielectric interfaces, have been demonstrated for GaN capacitors and field effect transistors (FETs). Separate and independently controlled interface formation and film deposition by remote plasma-assisted processing steps performed at 300 °C were employed. The interfacial oxide is Ga2O3, and the deposited gate dielectric is SiO2. Models for the chemical bonding at the GaN–Ga2O3 interface and at the internal dielectric Ga2O3–SiO2 are presented. The most important aspect of the interface formation involves a redistribution of electrons in the surface atom dangling bonds of the GaN polar face that promotes formation of two-electron bonds with the interfacial dielectric. DA - 1999/11/16/ PY - 1999/11/16/ DO - 10.1002/(sici)1521-396x(199911)176:1<793::aid-pssa793>3.0.co;2-v VL - 176 IS - 1 SP - 793-796 SN - 0031-8965 ER - TY - JOUR TI - A simple model of nonlinear diffusive shock acceleration AU - Berezhko, EG AU - Ellison, DC T2 - ASTROPHYSICAL JOURNAL AB - We present a simple model of nonlinear diffusive shock acceleration (also called first-order Fermi shock acceleration) that determines the shock modification, spectrum, and efficiency of the process in the plane-wave, steady state approximation as a function of an arbitrary injection parameter, η. The model, which uses a three-power-law form for the accelerated particle spectrum and contains only simple algebraic equations, includes the essential elements of the full nonlinear model and has been tested against Monte Carlo and numerical kinetic shock models. We include both adiabatic and Alfvén wave heating of the upstream precursor. The simplicity and ease of calculation make this model useful for studying the basic properties of nonlinear shock acceleration, as well as providing results accurate enough for many astrophysical applications. It is shown that the shock properties depend upon the shock speed u0 with respect to a critical value u ∝ ηp, which is a function of the injection rate η and maximum accelerated particle momentum pmax. For u0 < u, acceleration is efficient and the shock is strongly modified by the back pressure of the energetic particles. In this case, the overall compression ratio is given by rtot ≈ 1.3M if M > MA0, or by rtot ≈ 1.5M in the opposite case (MS0 is the sonic Mach number and MA0 is the Alfvén Mach number). If u0 > u, the shock, although still strong, becomes almost unmodified and accelerated particle production decreases inversely proportional to u0. DA - 1999/11/20/ PY - 1999/11/20/ DO - 10.1086/307993 VL - 526 IS - 1 SP - 385-399 SN - 1538-4357 KW - acceleration of particles KW - cosmic rays KW - shock waves ER - TY - JOUR TI - Visible-blind UV digital camera based on a 32 x 32 array of GaN/AlGaN p-i-n photodiodes AU - Brown, J. D. AU - Yu, Z. H. AU - Matthews, J. AU - Harney, S. AU - Boney, J. AU - Schetzina, J. F. AU - Benson, J. D. AU - Dang, K. W. AU - Terrill, C. AU - Nohava, T. AU - Yang, W. AU - Krishnankutty, S. T2 - MRS Internet Journal of Nitride Semiconductor Research AB - A visible-blind UV camera based on a 32 × 32 array of backside-illuminated GaN/AlGaN p-i-n photodiodes has been successfully demonstrated. Each of the 1024 photodiodes in the array consists of a base n-type layer of AlGaN (~20%) onto which an undoped GaN layer followed by a p-type GaN layer is deposited by metallorganic vapor phase epitaxy. Double-side polished sapphire wafers are used as transparent substrates. Standard photolithographic, etching, and metallization procedures were employed to obtain fully-processed devices. The photodiode array was hybridized to a silicon readout integrated circuit using In bump bonds. Output from the UV camera was recorded at room temperature at a frame rate of 30 Hz. This new type of visible-blind digital camera is sensitive to radiation from 320 nm to 365 nm in the UV spectral region. DA - 1999/// PY - 1999/// DO - 10.1557/s109257830000065x VL - 4 IS - 9 SP - 1-10 ER - TY - JOUR TI - Theoretical aspects of the optical response of semiconductor surfaces AU - Bechstedt, F AU - Pulci, O AU - Schmidt, WG T2 - PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE AB - We discuss the progress in realistic calculations of the optical response of semiconductor surfaces. It concerns numerical developments as well as the better inclusion of many-body effects. We show that the starting point of such calculations, the atomic structure and the surface equilibrium phase, can be now derived with high accuracy. The different steps are described in detail for the computation of the reflectance anisotropy and the exploration of the In-rich InP(001)2×4 surfaces. DA - 1999/9/16/ PY - 1999/9/16/ DO - 10.1002/(sici)1521-396x(199909)175:1<5::aid-pssa5>3.0.co;2-9 VL - 175 IS - 1 SP - 5-16 SN - 1862-6319 ER - TY - JOUR TI - Structure of ultrathin SiO2/Si(111) interfaces studied by photoelectron spectroscopy AU - Keister, JW AU - Rowe, JE AU - Kolodziej, JJ AU - Niimi, H AU - Tao, HS AU - Madey, TE AU - Lucovsky, G T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - Device-grade ultrathin (9–22 Å) films of silicon dioxide, prepared from crystalline silicon by remote-plasma oxidation, are studied by soft x-ray photoelectron spectroscopy (SXPS). The 2p core-level spectra for silicon show evidence of five distinct states of Si, attributable to the five oxidation states of silicon between Si0 (the Si substrate) and Si4+ (the thin SiO2 film). The relative binding energy shifts for peaks Si1+ through Si4+ (with respect to Si0) are in agreement with earlier work. The relatively weaker signals found for the three intermediate states (I1, I2, and I3) are attributed to silicon atoms at the abrupt interface between the thin SiO2 film and substrate. Estimates of the interface state density from these interface signals agree with the values reported earlier of ∼2 monolayers (ML). The position and intensity of the five peaks are measured as a function of post-growth annealing temperature, crystal orientation, and exposure to He/N2 plasma. We find that annealing produces more abrupt interfaces (by reducing the suboxide interface state density), but never more abrupt than ∼1.5 monolayers. We observe a 15%–20% drop in the interface thickness (in particular the “Si2+” peak intensity) with increasing annealing temperature. Somewhat different behavior is observed with small amounts of nitrogen in the SiO2 film where an apparent increase in interface state density is seen. A quantitative analysis is presented which explores the effects of these sample preparation parameters in terms of relative interface state density and modeling of the SXPS data. DA - 1999/// PY - 1999/// DO - 10.1116/1.581805 VL - 17 IS - 4 SP - 1250-1257 SN - 1520-8559 ER - TY - JOUR TI - Silicon oxide/silicon nitride dual-layer films: a stacked gate dielectric for the 21st century AU - Lucovsky, G T2 - JOURNAL OF NON-CRYSTALLINE SOLIDS AB - Incorporation of nitrogen atoms into ultra thin (<0.3 nm) gate dielectrics (i) reduces defect generation at the Si–SiO2 interface, (ii) allows use of physically thicker dielectrics when incorporated into oxide–nitride stacked gate dielectrics, and (iii) prevents boron atom transport out of heavily doped p+ polycrystalline silicon gate electrodes when nitrided layers are incorporated at the polycrystalline Si-dielectric interface. I demonstrate that nitrogen atoms can be selectively and independently incorporated into different parts of the gate dielectric structure by low-temperature (∼300°C) remote plasma assisted processing followed by low-thermal budget rapid thermal annealing (RTA) yielding state of the art field effect transistors with oxide equivalent thicknesses less than 2 nm. DA - 1999/9/1/ PY - 1999/9/1/ DO - 10.1016/S0022-3093(99)00432-9 VL - 254 SP - 26-37 SN - 1873-4812 ER - TY - JOUR TI - Selective area metalorganic molecular-beam epitaxy of GaN and the growth of luminescent microcolumns on Si/SiO2 AU - Guha, S AU - Bojarczuk, NA AU - Johnson, MAL AU - Schetzina, JF T2 - APPLIED PHYSICS LETTERS AB - We demonstrate the selective area growth of gallium nitride on patterned Si(111)/GaN/SiO2 wafers by metalorganic molecular beam epitaxy using triethyl gallium as a Ga source. We show that such selective area deposition may be used to grow isolated microcolumns of GaN with lateral dimensions of tens of nanometers on Si/SiO2 wafers. Via high resolution cathodoluminescence imaging we show that such microcolumn structures are highly luminescent inspite of a large surface to volume ratio, indicating that nonradiative recombination at free surfaces is not a significant issue in this system. DA - 1999/7/26/ PY - 1999/7/26/ DO - 10.1063/1.124409 VL - 75 IS - 4 SP - 463-465 SN - 0003-6951 ER - TY - JOUR TI - Real-time optical control of Ga1-xInxP film growth by p-polarized reflectance AU - Dietz, N AU - Woods, V AU - Ito, K AU - Lauko, I T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - The engineering of advanced optoelectronic integrated circuits implies the stringent control of thickness and composition. These demands led to the development of surface-sensitive real-time optical sensors that are able to move the control point close to the point where the growth occurs, which in a chemical beam epitaxy process is the surface reaction layer, built up of physisorbed and chemisorbed precursor fragments between the ambient and film interface. In this context, we explored the application of p-polarized reflectance spectroscopy (PRS) for real-time monitoring and control of pulsed chemical beam epitaxy during low-temperature growth of epitaxial Ga1−xInxP heterostructures on Si(001) substrates. A reduced order surface kinetics model has been developed to describe the decomposition and growth kinetics of the involved organometallic precursors and their incorporation in the film deposition. We demonstrate the linkage of the PRS response towards the surface reaction chemistry, composition, film growth rate, and film properties. Mathematical control algorithms are applied that link the PR signals to the growth process control parameters to control the composition and growth rate of epitaxial Ga1−xInxP heterostructures. DA - 1999/// PY - 1999/// DO - 10.1116/1.581811 VL - 17 IS - 4 SP - 1300-1306 SN - 1520-8559 ER - TY - JOUR TI - Reaction/annealing pathways for forming ultrathin silicon nitride films for composite oxide-nitride gate dielectrics with nitrided crystalline silicon-dielectric interfaces for application in advanced complementary metal-oxide-semiconductor devices AU - Lucovsky, G T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - Aggressive scaling of complementary metal–oxide–semiconductor (CMOS) devices requires gate dielectrics with an oxide equivalent thickness, tox,eq∼1 nm or less by the product introduction year 2012. Direct tunneling presents a significant performance limitation in field-effect transistors (FETs) with homogeneous oxide gate dielectrics &lt;1.7 nm. Boron diffusion from p+ poly-Si gate electrodes in p-channel FETs leads to additional electrical problems for oxide thicknesses &lt;3 nm. Interfacial nitridation improves reliability in n-channel FETs; however, by itself, it is not effective in p-type metal–oxide–semiconductor FETs due to boron pileup at the Si–dielectric interface. Proposed solutions include top-oxide surface nitridation and the integration of composite oxide–nitride dielectrics into CMOS devices. This review discusses the integration of hydrogenated silicon nitride films, prepared by remote plasma-enhanced chemical-vapor deposition, into electrical devices with composite oxide–nitride (ON) gate dielectrics. FET devices with ON dielectrics having the same oxide-equivalent thickness, tox-eq and gate dielectric capacitance as devices with homogeneous oxide gate dielectrics display improved performance and reliability. However, reductions in direct tunneling current due to increased physical thickness are below expectations based on tunneling calculations which assume the tunneling mass of electrons in nitride films is approximately the same as in SiO2. The combination of a lower electron tunneling mass and a reduced conduction-band offset energy (i) places important limitations on the extent to which devices with ON gate dielectrics can meet the aggressive scaling needed in advanced CMOS devices, and (ii) raises important questions that have to be addressed when evaluating alternative high-K dielectrics such as Ta2O5, TiO2, and Al2O3. However, tunneling can be reduced by combining monolayer interface nitridation with ON stacks. DA - 1999/// PY - 1999/// DO - 10.1116/1.581818 VL - 17 IS - 4 SP - 1340-1351 SN - 1520-8559 ER - TY - JOUR TI - Parity violation in neutron resonances of Rh-103 AU - Smith, DA AU - Bowman, JD AU - Crawford, BE AU - Grossmann, CA AU - Haseyama, T AU - Masaike, A AU - Matsuda, Y AU - Mitchell, GE AU - Penttila, SI AU - Roberson, NR AU - Seestrom, SJ AU - Sharapov, EI AU - Stephenson, SL AU - Yuan, VW T2 - PHYSICAL REVIEW C AB - Parity nonconservation (PNC) was studied in $p$-wave neutron resonances of ${}^{103}\mathrm{Rh}$ in the neutron energy range 30 to 490 eV. The helicity dependence of the neutron total cross section of rhodium was determined by capture measurements with the time-of-flight method at the Manuel Lujan Neutron Scattering Center at the Los Alamos National Laboratory. A total of 32 $p$-wave resonances were studied and statistically significant longitudinal asymmetries were observed for resonances at ${E}_{n}=44.5,$ 110.8, 321.6, and 432.9 eV. A statistical analysis treating the PNC matrix elements as random variables yields a weak spreading width ${\ensuremath{\Gamma}}_{w}{=(1.42}_{\ensuremath{-}0.59}^{+1.21})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}\mathrm{eV}.$ DA - 1999/10// PY - 1999/10// DO - 10.1103/physrevc.60.045503 VL - 60 IS - 4 SP - SN - 1089-490X ER - TY - JOUR TI - Neutron resonance spectroscopy of Rh-103 from 30 eV to 2 keV AU - Smith, DA AU - Bowman, JD AU - Crawford, BE AU - Grossmann, CA AU - Haseyama, T AU - Masaike, A AU - Matsuda, Y AU - Mitchell, GE AU - Penttila, SI AU - Roberson, NR AU - Seestrom, SJ AU - Sharapov, EI AU - Stephenson, SL AU - Yuan, V T2 - PHYSICAL REVIEW C AB - Neutron resonances in ${}^{103}\mathrm{Rh}$ have been measured for neutron energies from 30 to 2000 eV using the time-of-flight method and the $(n,\ensuremath{\gamma})$ reaction. The rhodium resonance spectroscopy is essential for the analysis of parity violation measurements recently performed on neutron resonances in ${}^{103}\mathrm{Rh}.$ Neutron scattering and radiative widths were determined, and orbital angular momentum assignments made with a Bayesian analysis. The $s$-wave and $p$-wave strength functions and average level spacings were determined. DA - 1999/10// PY - 1999/10// DO - 10.1103/physrevc.60.045502 VL - 60 IS - 4 SP - SN - 1089-490X ER - TY - JOUR TI - Defect energetics and impurity incorporation mechanisms at the arsenic-passivated Si(100) surface AU - Ramamoorthy, M AU - Briggs, EL AU - Bernholc, J T2 - PHYSICAL REVIEW B AB - Theoretical calculations show that defect properties of the Si(100) and Si(100):As surfaces are completely different. Large atomic relaxations around vacancies near the Si(100) surface cause chemical rebonding and defect healing that greatly lowers their formation energies. However, passivation of the surface by a monolayer of As induces substantial structural rigidity in the near-surface region. This reduces atomic relaxations and raises vacancy formation energies to high values, inhibiting vacancy mediated processes near the surface. The formation energies of silicon interstitials near the As-passivated surface are significantly lower than those of vacancies, which favors an interstitial mode of arsenic incorporation into the bulk during in diffusion. These results explain the observed uniformity of the Si(100):As surface and the high level of electrical activation of in-diffused As. DA - 1999/9/15/ PY - 1999/9/15/ DO - 10.1103/physrevb.60.8178 VL - 60 IS - 11 SP - 8178-8184 SN - 2469-9969 ER - TY - JOUR TI - Crystal structure of bullfrog M ferritin at 2.8 angstrom resolution: analysis of subunit interactions and the binuclear metal center AU - Ha, Y AU - Shi, DS AU - Small, GW AU - Theil, EC AU - Allewell, NM T2 - JOURNAL OF BIOLOGICAL INORGANIC CHEMISTRY DA - 1999/6// PY - 1999/6// DO - 10.1007/s007750050310 VL - 4 IS - 3 SP - 243-256 SN - 1432-1327 KW - crystallography KW - iron oxidation KW - iron storage KW - multisubunit proteins ER - TY - JOUR TI - Chemical vapor cleaning of 6H-SiC surfaces AU - King, SW AU - Kern, RS AU - Benjamin, MC AU - Barnak, JP AU - Nemanich, RJ AU - Davis, RF T2 - JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB - The techniques (temperature range of study) of in situ thermal desorption (500‐1100°C) and chemical vapor cleaning (CVC) via exposure to and/or (750‐1100°C) have been investigated for preparing surfaces suitable for epitaxial growth of SiC and III‐nitride films, and are compared with regard to surface purity, stoichiometry, and structural order. Oxide removal below the detection limits of Auger electron spectroscopy was achieved for all orientations via annealing in at 850‐900°C or ≈200° lower than necessary by thermal desorption. No non‐SiC carbon was detected on the surface by X‐ray photoelectron spectroscopy. An approximately one‐tenth of a monolayer of oxygen coverage and significant quantities of non‐SiC carbon were detected for all 6H‐SiC surfaces prepared by thermal desorption. In contrast to the predominantly non‐SiC carbon‐rich surfaces prepared by thermal desorption, the stoichiometry of the SiC surfaces prepared by CVC could be manipulated from Si‐rich to C‐rich without non‐SiC carbon formation by either extending the exposures or by following with exposure. The latter surfaces also had lower concentrations of both oxygen and non‐SiC carbon and increased surface order. © 1999 The Electrochemical Society. All rights reserved. DA - 1999/9// PY - 1999/9// DO - 10.1149/1.1392494 VL - 146 IS - 9 SP - 3448-3454 SN - 0013-4651 ER - TY - JOUR TI - Cathodoluminescence spectroscopy of nitrided SiO2-Si interfaces AU - Young, AP AU - Bandhu, R AU - Schafer, J AU - Niimi, H AU - Lucovsky, G T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS AB - We use cathodoluminescence spectroscopy (CLS) to investigate the electronic states of ultrathin gate dielectrics with nitrided SiO2–Si interfaces, known to improve reliability in advanced complementary metal–oxide–semiconductor devices. The 5 nm thick films investigated were: (i) as-deposited (at 300 °C) structures, (ii) 400 °C hydrogen anneal, (iii) 900 °C rapid thermal anneal (RTA), and (iv) a combination of both anneals. CLS emission energies and intensities versus excitation energy were essentially unchanged for the as-deposited interface compared to non-nitrided plasma-processed interfaces. In the near-infrared, features appear at 0.8 and 1.0 eV, with the 1.0 eV peak Si substrate intensity increasing with increasing depth. From depth variation measurements at higher photon energy, a 3.4 eV peak is also shown to arise from the Si substrate, and a 2.7 eV feature is shown to come from the interface region. After hydrogenation, the CLS is essentially the same as for non-nitrided interfaces, except for an increase in the relative intensity of a broad background luminescence ranging from 1.5 to 2.5 eV. However, the RTA and the combination of the RTA and hydrogenation do not completely suppress emission near 2.0 eV feature as for non-nitrided interfaces. From the behavior of the CLS features, we are able to clearly distinguish between interfacial defects and substrate features, which are significantly reduced by the combined RTA/hydrogen anneal, and features that are not reduced by the annealing procedures. DA - 1999/// PY - 1999/// DO - 10.1116/1.581806 VL - 17 IS - 4 SP - 1258-1262 SN - 0734-2101 ER - TY - JOUR TI - Calculational approach for the structure of electron and hole levels in quantum dots of varying shape AU - Kiselev, AA AU - Kim, KW AU - Stroscio, MA T2 - PHYSICAL REVIEW B AB - Another approach to the calculation of electron and hole states in quantum dots is proposed. It benefits from the particular choice of products of powers of Cartesian coordinates as a basis, since it is possible to evaluate all required matrix elements analytically for these systems. A variety of dot shapes in the presence of external electric fields can be analyzed conveniently. This approach provides a way to calculate quantum dot ensemble averages quickly and effectively. DA - 1999/9/15/ PY - 1999/9/15/ DO - 10.1103/physrevb.60.7748 VL - 60 IS - 11 SP - 7748-7751 SN - 1550-235X ER - TY - JOUR TI - BB intermeson potentials in the quark model - art. no. 045202 AU - Barnes, T. AU - Black, N. AU - Dean, D. J. AU - Swanson, E. S. T2 - Physical Review. C, Nuclear Physics DA - 1999/// PY - 1999/// VL - 6004 IS - 4 SP - 5202- ER - TY - JOUR TI - Analysis of high-index Si(001) surfaces by reflectance difference spectroscopy AU - Mantese, L AU - Xue, QK AU - Sakurai, T AU - Aspnes, DE T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - We report surface-induced optical anisotropy spectra of high-index Si(115), (114), and (113) surfaces obtained using reflectance difference spectroscopy. Air-oxidized surfaces show sharp derivative-type features that are step-induced and located near the critical point energies of bulk Si, consistent with those of lower-index Si(001) surfaces. Clean reconstructed surfaces are characterized by a broad feature near 3 eV that tends to decrease in amplitude upon H exposure and a step-induced structure near the (E0′,E1) transition of bulk Si. In contrast, H exposure of Ge-covered surfaces tends to sharpen and enhance lower-energy structures. The derivative-type features located near the bulk critical point energies of Si can be described in terms of electronic states localized by the finite penetration depth of light. DA - 1999/// PY - 1999/// DO - 10.1116/1.581867 VL - 17 IS - 4 SP - 1652-1656 SN - 1520-8559 ER - TY - JOUR TI - X-ray photoelectron spectroscopy analysis of GaN/(0001)AlN and AlN/(0001)GaN growth mechanisms AU - King, SW AU - Carlson, EP AU - Therrien, RJ AU - Christman, JA AU - Nemanich, RJ AU - Davis, RF T2 - JOURNAL OF APPLIED PHYSICS AB - The mechanisms of growth of GaN on AlN and AlN on GaN via gas source-molecular beam epitaxy with NH3 as the nitrogen source have been investigated using x-ray photoelectron spectroscopy, low energy electron diffraction, and Auger electron spectroscopy. The growth of GaN on AlN at low temperatures (650–750 °C) occurs via a Stranski–Krastanov 2D→3D type mechanism with the transition to 3D growth occurring at ≈10–15 Å. The mechanism changes to Frank van der Merwe (FM)/layer-by-layer growth above 800 °C. The growth of AlN on GaN occurred via a FM layer-by-layer mechanism within the 750–900 °C temperature range investigated. We propose a model based on the interaction of ammonia and atomic hydrogen with the GaN/AlN surfaces which indicates that the surface kinetics of hydrogen desorption and ammonia decomposition are the factors that determine the GaN growth mechanism. DA - 1999/11/15/ PY - 1999/11/15/ DO - 10.1063/1.371564 VL - 86 IS - 10 SP - 5584-5593 SN - 0021-8979 ER - TY - JOUR TI - Valence band discontinuity of the (0001) 2H-GaN/(111) 3C-SiC interface AU - King, SW AU - Davis, RF AU - Ronning, C AU - Nemanich, RJ T2 - JOURNAL OF ELECTRONIC MATERIALS DA - 1999/12// PY - 1999/12// DO - 10.1007/s11664-999-0145-4 VL - 28 IS - 12 SP - L34-L37 SN - 0361-5235 KW - GaN KW - SiC KW - valence band KW - discontinuity KW - gallium nitride KW - silicon carbide KW - x-ray photoelectron spectroscopy KW - ultra-violet photoelectron spectroscopy ER - TY - JOUR TI - Quartz microbalance studies of superconductivity-dependent sliding friction - Reply AU - Krim, J T2 - PHYSICAL REVIEW LETTERS AB - A Reply to the Comment by R. L. Renner, J. E. Rutledge, and P. Taborek.Received 19 March 1999DOI:https://doi.org/10.1103/PhysRevLett.83.1262©1999 American Physical Society DA - 1999/8/9/ PY - 1999/8/9/ DO - 10.1103/PhysRevLett.83.1262 VL - 83 IS - 6 SP - 1262-1262 SN - 1079-7114 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-4244148930&partnerID=MN8TOARS ER - TY - JOUR TI - NEXAFS spectromicroscopy of polymers: overview and quantitative analysis of polyurethane polymers AU - Urquhart, SG AU - Hitchcock, AP AU - Smith, AP AU - Ade, HW AU - Lidy, W AU - Rightor, EG AU - Mitchell, GE T2 - JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA AB - The successful application of X-ray spectromicroscopy to chemical analysis of polymers is reviewed and a detailed application to quantitative analysis of polyurethanes is presented. Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy is the basis of chemical sensitive X-ray imaging, as well as qualitative and quantitative micro-spectroscopy. These capabilities are demonstrated by a review of recent work, and by presentation of new results outlining a methodology for quantitative speciation of polyurethane polymers. C 1s inner-shell excitation spectra of a series of molecular and polymeric model compounds, recorded by gas phase inelastic electron scattering (ISEELS) and solid phase NEXAFS techniques, are used to understand the spectroscopic basis for chemical analysis of polyurethanes. These model species contain the aromatic urea, aromatic urethane (carbamate) and aliphatic ether functionalities that are the main constituents of polyurethane polymers. Ab initio calculations of several of the model molecular compounds are used to support spectral assignments and give insight into the origin and relative intensities of characteristic spectral features. The model polymer spectra provide reference standards for qualitative identification and quantitative analysis of polyurethane polymers. The chemical compositions of three polyurethane test polymers with systematic variation in urea/urethane content are measured using the spectra of model toluene diisocyanate (TDI) urea, TDI-carbamate, and poly(propylene oxide) polymers as reference standards. DA - 1999/10// PY - 1999/10// DO - 10.1016/S0368-2048(99)00043-2 VL - 100 IS - 1999 Oct. SP - 119-135 SN - 1873-2526 KW - NEXAFS microscopy KW - polyurethanes KW - molecular models KW - polymer quantitative analysis ER - TY - JOUR TI - Monolayer-level controlled incorporation of nitrogen at Si-SiO(2) interfaces using remote plasma processing AU - Niimi, H AU - Lucovsky, G T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A AB - We demonstrate three different ways to incorporate nitrogen at Si–SiO2 interfaces: (i) an O2/He plasma oxidation of the Si surface followed by an N2/He plasma nitridation, (ii) an N2/He plasma nitridation of the Si surface, and (iii) a Si3N4 film deposition on to the Si surface. The two-step interface formation, the O2/He plasma oxidation followed by the N2/He plasma nitridation, is shown to yield significantly better interface device properties than the other two approaches. These differences in interface properties are explained by an application of constraint theory based on comparisons of the average bonding coordination of the dielectric layer at the interface with the Si substrate. DA - 1999/// PY - 1999/// DO - 10.1116/1.582041 VL - 17 IS - 6 SP - 3185-3196 SN - 0734-2101 ER - TY - JOUR TI - Measurement and calculation of PZT thin film longitudinal piezoelectric coefficients AU - Maiwa, H AU - Maria, JP AU - Christman, JA AU - Kim, SH AU - Streiffer, K AU - Kingon, AI T2 - INTEGRATED FERROELECTRICS AB - Abstract The ferroelectric and piezoelectric properties of 2000 Ä thick chemical solution deposited Pb(ZrxTi1−x)O3 (PZT) thin films were investigated. Several Zr/Ti ratios were studied: 30/70, 50/50 and 65/35, which correspond to tetragonal, near-morphotropic, and rhombohedral symmetries. In all samples, a {111}-texture is predominant. Longitudinal piezoelectric coefficients and their dc field dependence were measured using the contact AFM method. The expected trend of a maximum piezoelectric coefficient at or near to the MPB was not observed. The composition dependence was small, with the maximum d33 occurring in the tetragonal material. To explain the results, crystallographic texture and film thickness effects are suggested. Using a modified phenomenological approach, derived electrostrictive coefficients, and experimental data, d33 values were calculated. Qualitative agreement was observed between the measured and calculated coefficients. Justifications of modifications to the calculations are discussed. Key Words: PiezoelectricAFMPZTcompositioncalculationelectrostriction DA - 1999/// PY - 1999/// DO - 10.1080/10584589908215586 VL - 24 IS - 1-4 SP - 139-146 SN - 1058-4587 KW - piezoelectric KW - AFM KW - PZT KW - composition KW - calculation KW - electrostriction ER - TY - JOUR TI - Maximum energies of shock-accelerated electrons in young shell supernova remnants AU - Reynolds, SP AU - Keohane, JW T2 - ASTROPHYSICAL JOURNAL AB - Young supernova remnants (SNRs) are often assumed to be the source of cosmic rays up to energies approaching the slight steepening in the cosmic-ray spectrum at around 1000 TeV, known as the "knee." We show that the observed X-ray emission of 14 radio-bright shell remnants, including all five historical shells, can be used to put limits on Emax, the energy at which the electron energy distribution must steepen from its slope at radio-emitting energies. Most of the remnants show thermal spectra, so any synchrotron component must fall below the observed X-ray fluxes. We obtain upper limits on Emax by considering the most rapid physically plausible cutoff in the relativistic electron distribution, an exponential, which is as sharp or sharper than found in any more elaborate models. This maximally curved model then gives us the highest possible Emax consistent with not exceeding observed X-rays. Our results are thus independent of particular models for the electron spectrum in SNRs. Assuming homogeneous emitting volumes with a constant magnetic field strength of 10 μG, no object could reach 1000 TeV, and only one, Kes 73, has an upper limit on Emax above 100 TeV. All the other remnants have limits at or below 80 TeV. Emax is probably set by the finite remnant lifetime rather than by synchrotron losses for remnants younger than a few thousand years, so that an observed electron steepening should be accompanied by steepening at the same energy for protons. More complicated, inhomogeneous models could allow higher values of Emax in parts of the remnant, but the emission-weighted average value, that characteristic of typical electrons, should obey these limits. The young remnants are not expected to improve much over their remaining lives at producing the highest energy Galactic cosmic rays; if they cannot, this picture of cosmic-ray origin may need major alteration. DA - 1999/11/1/ PY - 1999/11/1/ DO - 10.1086/307880 VL - 525 IS - 1 SP - 368-374 SN - 0004-637X KW - acceleration of particles KW - shock waves KW - supernova remnants KW - supernovae : general KW - X-rays : ISM ER - TY - JOUR TI - Light-cone quark model analysis of radially excited pseudoscalar and vector mesons - art. no. 094020 AU - Arndt, D. AU - Ji, C. R. T2 - Physical Review. D, Particles and Fields DA - 1999/// PY - 1999/// VL - 6009 IS - 9 SP - 4020 ER - TY - JOUR TI - DA 530: A supernova remnant in a stellar wind bubble AU - Landecker, TL AU - Routledge, D AU - Reynolds, SP AU - Smegal, RJ AU - Borkowski, KJ AU - Seward, FD T2 - ASTROPHYSICAL JOURNAL AB - The high-latitude supernova remnant (SNR) DA 530 (G93.3+6.9), apparently a typical shell remnant, has highly polarized radio continuum emission and a very uniform circumferential magnetic field. We present new radio continuum (408 and 1420 MHz) and H I line observations, made with the Dominion Radio Astrophysical Observatory Synthesis Telescope, and we have made the first detection of X-ray emission from the SNR, using the ROSAT Position-Sensitive Proportional Counter. The SNR lies within a shell of H I, possibly created by an earlier stellar wind, whose kinematic distance is nominally 2.5 kpc but whose actual distance may be larger. The X-ray emission is extremely faint. A Raymond-Smith ionization-equilibrium model fits the data and suggests a very low density, ~0.05 cm-3, consistent with the occurrence of the supernova in a stellar wind cavity, but this model yields an explosion energy 100 times lower than the accepted value. A nonequilibrium shock model, incorporating a range of ionization timescales, is able to give more realistic physical parameters for the supernova remnant. On the balance of the evidence, we place DA 530 at a distance of 3.5 kpc, the largest distance permitted by the H I observations, where it lies 420 pc above the Galactic plane. The explosion, probably a Type Ia supernova, in a low-density cavity has resulted in weak X-ray emission and slow evolution. The explosion energy was 3.9 × 1050 ergs and the age is ~5000 years. The remnant, having swept up 3.9 M☉ in an ambient density of ~0.01 cm-3, is only now in the adiabatic phase, and this explains the absence of detected optical emission. Despite the low ambient density the efficiency of generation of synchrotron radio emission is ~0.4%, higher than in some historical SNRs. The ratio of radio to X-ray flux is about 100 times that for the remnant of SN 1006, which has comparable radio continuum properties. The very uniform magnetic field is not explained. DA 530 joins a small group of remnants at high Galactic latitude with unusual features, perhaps resulting from low ambient densities. Inhomogeneous nonequilibrium ionization models may be required for the interpretation of the X-ray emission from many other older SNRs. DA - 1999/12/20/ PY - 1999/12/20/ DO - 10.1086/308100 VL - 527 IS - 2 SP - 866-878 SN - 0004-637X KW - ISM : bubbles KW - ISM : individual (DA 530) KW - radio continuum : ISM KW - supernova remnants KW - X-rays : ISM ER - TY - JOUR TI - (2x4) GaP(001) surface: Atomic structure and optical anisotropy AU - Frisch, AM AU - Schmidt, WG AU - Bernholc, J AU - Pristovsek, M AU - Esser, N AU - Richter, W T2 - PHYSICAL REVIEW B AB - We have investigated the microscopic structure and optical anisotropy of $(2\ifmmode\times\else\texttimes\fi{}4)$ reconstructed GaP(001) surfaces. Optical and electron spectroscopy from GaP(001) surfaces prepared in ultrahigh-vacuum conditions were combined with first-principles calculations of the energetics and reflectance anisotropy. Symmetry, composition and surface optical anisotropy were characterized by low-energy electron diffraction, Auger electron spectroscopy, photoemission spectroscopy and reflectance anisotropy spectroscopy. In contrast to most earlier reports, we find that the stable Ga-rich surface corresponds to a $(2\ifmmode\times\else\texttimes\fi{}4)$ reconstruction. No $(4\ifmmode\times\else\texttimes\fi{}2)$ reconstruction could be observed, independent of the preparation method. Depending on the Ga coverage, however, two distinct line shapes in the reflection anisotropy spectra occur, indicating the existence of at least two different surface phases with $(2\ifmmode\times\else\texttimes\fi{}4)$ periodicity. This agrees with our total-energy calculations: Four $(2\ifmmode\times\else\texttimes\fi{}4)$ structural models may be stable depending on the chemical potentials of the surface constituents. All considered $(4\ifmmode\times\else\texttimes\fi{}2)$ structures, however, are unstable. Based on the comparison between calculated reflectance anisotropy spectra and measured data we suggest mixed Ga-P dimers on top of the Ga-terminated substrate as ground-state geometry for the cation-rich phase of GaP(001)$(2\ifmmode\times\else\texttimes\fi{}4)$. Our results indicate the formation of P dimers at the surface for the more anion-rich phase of GaP(001)$(2\ifmmode\times\else\texttimes\fi{}4)$. DA - 1999/7/15/ PY - 1999/7/15/ DO - 10.1103/physrevb.60.2488 VL - 60 IS - 4 SP - 2488-2494 SN - 2469-9969 ER - TY - JOUR TI - Wet chemical processing of (0001)(Si) 6H-SiC hydrophobic and hydrophilic surfaces AU - King, SW AU - Nemanich, RJ AU - Davis, RF T2 - JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB - The wetting characteristics of polished or polished and thermally oxidized, on‐ and off‐axis (0001)Si 6H‐SiC [the silicon‐terminated surface of SiC] surfaces in selected acids and bases have been determined and compared with that of (111)Si. Auger electron and X‐ray photoelectron spectroscopies and low energy electron diffraction were used to characterize the chemical state and order of these surfaces. The oxidized SiC surfaces were hydrophilic after oxide removal with a 10:1 HF solution and were terminated with approximately a monolayer containing OH, CO, CH, and F species. The same effects were observed for the similarly treated [the carbon‐terminated surface of SiC], , and surfaces. The as‐polished SiC surfaces were hydrophobic and covered with a thin (5–10 Å) contamination layer composed primarily of C‐C, C‐F, and Si‐F bonded species. Removal of this layer using an RCA SCl etch or Piranha clean resulted in a disordered hydrophilic SiC surface. A 20 Å amorphous Si capping layer both passivated the SiC surfaces and provided a better alternative to the aforementioned contamination layer for producing hydrophobic surfaces on this material. © 1999 The Electrochemical Society. All rights reserved. DA - 1999/5// PY - 1999/5// DO - 10.1149/1.1391864 VL - 146 IS - 5 SP - 1910-1917 SN - 0013-4651 ER - TY - JOUR TI - Valence band discontinuity, surface reconstruction, and chemistry of (0001), (000(1)over-bar), and (1(1)over-bar-00) 2H-AlN/6H-SiC interfaces AU - King, SW AU - Davis, RF AU - Ronning, C AU - Benjamin, MC AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - A detailed examination of the valence band discontinuity (ΔEv) formed at the (0001), (0001̄), and (11̄00) interfaces between 2H–AlN and 6H–SiC has been conducted using x-ray and UV photoelectron spectroscopies. The ΔEv was observed to range from 0.6–2.0 eV depending on the growth direction (i.e., AlN on SiC vs SiC on AlN), as well as the crystallographic orientation, cut of the SiC substrate (i.e., on versus off axis), and SiC surface reconstruction and stoichiometry. A ΔEv of 1.4–1.5 eV was observed for AlN grown on (3×3) (0001)Si6H–SiC on-axis substrates; a ΔEv of 0.9–1.0 eV was observed for off-axis substrates with the same surface reconstruction. The values of ΔEv for AlN grown on (√3×√3)R30°(0001) 6H–SiC on-and-off-axis substrates were 1.1–1.2 eV. A larger valence band discontinuity of 1.9–2.0 eV was determined for 3C–SiC grown on (0001) 2H–AlN. Smaller values of ΔEv of 0.6–0.7 and 0.8–0.9 eV were observed for AlN grown on on-axis (0001̄)C and (11̄00)6H–SiC substrates, respectively. DA - 1999/10/15/ PY - 1999/10/15/ DO - 10.1063/1.371391 VL - 86 IS - 8 SP - 4483-4490 SN - 0021-8979 ER - TY - JOUR TI - Ultrathin nitrided gate dielectrics: Plasma processing, chemical characterization, performance, and reliability AU - Lucovsky, G T2 - IBM JOURNAL OF RESEARCH AND DEVELOPMENT AB - The incorporation of nitrogen (N) atoms into ultrathin gate dielectrics 1) at monolayer levels at Si-SiO 2 interfaces reduces tunneling current and defect generation; 2) in bulk nitrides, as in oxide-nitride-oxide (ONO) or oxide-nitride (ON) composite structures, allows the use of physically thicker films without reduced capacitance compared to single-layer oxides; and 3) in nitrided layers at the polycrystalline Si-dielectric interface or in ON dielectrics reduces boron (B) atom out-diffusion from heavily doped p + polycrystalline silicon gate electrodes into oxide gate dielectrics. The results presented in this review demonstrate that N atoms can be selectively and independently incorporated into different parts of the gate dielectric by low-temperatureremote-plasma-assisted processing. When combined with low-thermal-budget rapid thermal annealing, this yields ultrathin gate dielectrics with performance and reliability which generally exceeds that of single-layer thermally grown oxides. The devices addressed in this paper include n-MOS and p-mos field-effect transistors (FETs) with oxide-equivalent thicknesses of less than 2 nm. DA - 1999/5// PY - 1999/5// DO - 10.1147/rd.433.0301 VL - 43 IS - 3 SP - 301-326 SN - 2151-8556 ER - TY - JOUR TI - Tuning friction with noise and disorder AU - Braiman, Y AU - Hentschel, HGE AU - Family, F AU - Mak, C AU - Krim, J T2 - PHYSICAL REVIEW E AB - We present numerical and experimental evidence which demonstrates that under certain conditions friction can be reduced by spatial disorder and/or thermal noise. We discuss possible mechanisms for this behavior. DA - 1999/5// PY - 1999/5// DO - 10.1103/physreve.59.r4737 VL - 59 IS - 5 SP - R4737-R4740 SN - 1063-651X UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0001044961&partnerID=MN8TOARS ER - TY - JOUR TI - The reliability and stability of the Turner and Engle working memory task AU - Klein, K AU - Fiss, WH T2 - BEHAVIOR RESEARCH METHODS INSTRUMENTS & COMPUTERS AB - The present study explored the psychometric properties of Turner and Engle’s (1989) operation span task, a widely used measure of working memory capacity. We administered the task three times to 33 college students, using equivalent test materials. The interval between the first and second administrations was 3 weeks, with 6–7 weeks between the second and third administrations. Alpha coefficients were all .75 or more. Recall accuracy decreased as operation set size increased. Raw test-retest correlations ranged from .67 to .81, the corrected reliability was .88, and stability scores ranged from .76 to .92. Performance improved from the first to the second test. Relative to reported reliabilities of other tasks used to assess individual differences in working memory capacity, the operation span task appears to have several statistical advantages. DA - 1999/8// PY - 1999/8// DO - 10.3758/BF03200722 VL - 31 IS - 3 SP - 429-432 SN - 0743-3808 ER - TY - JOUR TI - Strength distribution of gamma-transitions deexciting superdeformed rotational bands AU - Lopez-Martens, AP AU - Dossing, T AU - Khoo, TL AU - Korichi, A AU - Hannachi, F AU - Calderin, IJ AU - Lauritsen, T AU - Ahmad, I AU - Carpenter, MP AU - Fischer, SM AU - Hackman, G AU - Janssens, RVF AU - Nisius, D AU - Rieter, P AU - Amro, H AU - Moore, EF T2 - NUCLEAR PHYSICS A AB - The strength distribution of the γ rays in the decay-out from superdeformed (SD) states is investigated by applying the maximum likelihood method, with special emphasis on the influence of the lower threshold given by experimental conditions. Clear graphical solutions are found, and a careful estimation of the dispersion in the values of the number of degrees of freedom and of the average strength of the most likely χ2 distribution is carried out. For the 194Hg nucleus, 41 primary transitions from the decay-out of SD states are identified above 2600 keV. It is concluded that they represent the strongest 10% of the transitions selected stochastically from a Porter-Thomas distribution. This would support the scenario of a statistical decay of SD states via coupling to a compound state at normal deformation. However, the occurrence of several very strong direct one-step transitions as previously observed in 194Hg has a very small probability of the order of 10−4. This may indicate special selection rules governing the decay. However, based on the absence of strong primary transitions from SD states in adjacent nuclei, the situation in 194Hg is viewed as a very lucky incidence. DA - 1999/3/8/ PY - 1999/3/8/ DO - 10.1016/S0375-9474(99)00012-3 VL - 647 IS - 3-4 SP - 217-245 SN - 0375-9474 KW - superdeformation KW - decay-out KW - tunneling KW - compound state KW - chaos KW - strength distribution KW - maximum likelihood ER - TY - JOUR TI - Role of the substrate strain in the sheet resistance stability of NiSi deposited on Si (100) AU - Maillard-Schaller, E AU - Boyanov, BI AU - English, S AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - In order to study the influence of strain on the formation and stability of NiSi, Ni has been deposited on strained and relaxed Si(100) n-type substrates. Strained Si substrates have been produced by depositing a pseudomorphic silicon film onto a 3000 Å thick relaxed Si0.8Ge0.2 film. Raman spectroscopy has established that the silicon film is strained. The presence of a characteristic cross-hatch pattern has been identified by atomic force microscopy. Measurements show that the sheet resistance (Rs) of the silicide formed on strained silicon remains stable up to 700 °C while the Rs of the silicide formed on bulk silicon (100) shows a significant increase at 600 °C . X-ray photoelectron spectroscopy shows that the NiSi–NiSi2 phase transition occurs at a higher temperature and is, therefore, not responsible for the Rs instability. Scanning electron microscopy measurements indicate that islanding occurs in the temperature region of the resistivity increase. Photoelectron emission microscopy has been employed to observe the surface morphology during annealing, and islanding is not observed until a higher annealing temperature for the NiSi on strained Si. The increase in Rs is apparently correlated to the islanding of NiSi which appears at lower temperature on the bulk silicon substrate than on the strained silicon substrate. The stability of the NiSi film on the strained Si substrate is related to the strain induced by thermal expansion and the increased lattice constant of the strained Si. DA - 1999/4/1/ PY - 1999/4/1/ DO - 10.1063/1.369774 VL - 85 IS - 7 SP - 3614-3618 SN - 1089-7550 ER - TY - JOUR TI - Raman analysis of the E1 and A1 quasi-longitudinal optical and quasi-transverse optical modes in wurtzite AlN AU - Bergman, L AU - Dutta, M AU - Balkas, C AU - Davis, RF AU - Christman, JA AU - Alexson, D AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - This article presents a study of the quasi-longitudinal optical and quasi-transverse optical modes in wurtzite AlN which originate from the interaction of phonons belonging to the A1 and E1 symmetry groups. In order to analyze the allowed quasi as well as pure Raman modes, the modes were observed in a rotating crystallographic coordinate system, and the Raman tensors of the wurtzite crystal structure were calculated as a function of the crystallographic rotation. The frequencies of the quasimodes of wurtzite AlN were also analyzed in terms of the interaction of the polar phonons with the long range electrostatic field model. The experimental values of the Raman frequencies of the quasiphonons concur with these expected from the model, implying that the long range electrostatic field dominates the short range forces for polar phonons in AlN. DA - 1999/4/1/ PY - 1999/4/1/ DO - 10.1063/1.369712 VL - 85 IS - 7 SP - 3535-3539 SN - 0021-8979 ER - TY - JOUR TI - Photon-induced localization in optically absorbing materials AU - Mantese, L AU - Bell, KA AU - Aspnes, DE AU - Rossow, U T2 - PHYSICS LETTERS A AB - We show that components of surface- and interface-related optical spectra that are related to derivatives of their bulk dielectric functions are due to a dynamic photon-induced localization of the initial and final states. Localization is described by correlation effects that arise from the finite penetration depth of light in optically absorbing materials, and lead to a substantially different perspective of optical absorption than that given by conventional theory. DA - 1999/3/15/ PY - 1999/3/15/ DO - 10.1016/S0375-9601(98)00953-0 VL - 253 IS - 1-2 SP - 93-97 SN - 0375-9601 KW - localization KW - surface optical absorption ER - TY - JOUR TI - Parity nonconservation in neutron resonances in Cs-133 AU - Sharapov, EI AU - Bowman, JD AU - Crawford, BE AU - Delheij, PPJ AU - Haseyama, T AU - Knudson, JN AU - Lowie, LY AU - Masaike, A AU - Masuda, Y AU - Matsuda, Y AU - Mitchell, GE AU - Penttila, SI AU - Postma, H AU - Roberson, NR AU - Seestrom, SJ AU - Stephenson, SL AU - Yen, YF AU - Yuan, VW T2 - PHYSICAL REVIEW C AB - Spatial parity nonconservation (PNC) has been studied in the compound-nuclear states of ${}^{134}\mathrm{Cs}$ by measuring the helicity dependence of the neutron total cross section. Transmission measurements on a thick ${}^{133}\mathrm{Cs}$ target were performed by the time-of-flight method at the Manuel Lujan Neutron Scattering Center with a longitudinally polarized neutron beam in the energy range from 5 to 400 eV. A total of 28 new p-wave resonances were found, their neutron widths determined, and the PNC longitudinal asymmetries of the resonance cross sections measured. The value obtained for the root-mean-square PNC element ${M=(0.06}_{\ensuremath{-}0.02}^{+0.25})$ meV in ${}^{133}\mathrm{Cs}$ is the smallest among all targets studied. This value corresponds to a weak spreading width ${\ensuremath{\Gamma}}_{w}{=(0.006}_{\ensuremath{-}0.003}^{+0.154})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$ eV. DA - 1999/3// PY - 1999/3// DO - 10.1103/physrevc.59.1772 VL - 59 IS - 3 SP - 1772-1779 SN - 1089-490X ER - TY - PAT TI - Optical information storage systems and methods using heterostructures comprising ternary group III-V nitride semiconductor materials AU - Shmagin, I. K. AU - Muth, J. F. AU - Kolbas, R. M. C2 - 1999/// DA - 1999/// PY - 1999/// ER - TY - JOUR TI - Optical and structural properties of epitaxial MgxZn1-xO alloys AU - Sharma, AK AU - Narayan, J AU - Muth, JF AU - Teng, CW AU - Jin, C AU - Kvit, A AU - Kolbas, RM AU - Holland, OW T2 - APPLIED PHYSICS LETTERS AB - The optical and structural properties of high-quality single-crystal epitaxial MgZnO films deposited by pulsed-laser deposition were studied. In films with up to ∼36 at. % Mg incorporation, we have observed intense ultraviolet band edge photoluminescence at room temperature and 77 K. The highly efficient photoluminescence is indicative of the excitonic nature of the material. Transmission spectroscopy was used to show that the excitonic structure of the alloys was clearly visible at room temperature. High-resolution transmission electron microscopy, x-ray diffraction, and Rutherford backscattering spectroscopy/ion channeling were used to verify the epitaxial single-crystal quality of the films and characterize the defect content. Post-deposition annealing in oxygen was found to reduce the number of defects and to improve the optical properties of the films. These results indicate that MgZnO alloys have potential applications in a variety of optoelectronic devices. DA - 1999/11/22/ PY - 1999/11/22/ DO - 10.1063/1.125340 VL - 75 IS - 21 SP - 3327-3329 SN - 1077-3118 ER - TY - JOUR TI - Octupole correlations in the Pu isotopes: From vibration to static deformation? AU - Wiedenhover, I AU - Janssens, RVF AU - Hackman, G AU - Ahmad, I AU - Greene, JP AU - Amro, H AU - Bhattacharyya, PK AU - Carpenter, MP AU - Chowdhury, P AU - Cizewski, J AU - Cline, D AU - Khoo, TL AU - Lauritsen, T AU - Lister, CJ AU - Macchiavelli, AO AU - Nisius, DT AU - Reiter, P AU - Seabury, EH AU - Seweryniak, D AU - Siem, S AU - Sonzogni, A AU - Uusitalo, J AU - Wu, CY T2 - PHYSICAL REVIEW LETTERS AB - In a series of measurements with Gammasphere, striking differences were found between the yrast and negative parity bands in ${}^{238--240}\mathrm{Pu}$ and those in ${}^{241--244}\mathrm{Pu}$. These differences can be linked to variations with mass of the strength of octupole correlations. At the highest spins, ${}^{238--240}\mathrm{Pu}$ are found to exhibit properties associated with stable octupole deformation, suggesting that a transition with spin from a vibration to stable deformation may have occurred. DA - 1999/9/13/ PY - 1999/9/13/ DO - 10.1103/PhysRevLett.83.2143 VL - 83 IS - 11 SP - 2143-2146 SN - 0031-9007 ER - TY - JOUR TI - Mechanical deformations and coherent transport in carbon nanotubes AU - Nardelli, MB AU - Bernholc, J T2 - PHYSICAL REVIEW B AB - We have investigated the conductance of carbon nanotubes under mechanical distortions likely to occur when forming nanoscale electronic devices. Using a realistic tight-binding Hamiltonian, several structure-dependent classes of electrical behavior in deformed nanotubes have been discovered. Bending, defects, and tube-tube contacts are shown to strongly modify transport in individual nanotubes, and to induce, in some cases, metal-semiconductor transitions. These results provide a clear interpretation of recent experimental findings and suggest avenues for their use in devices. DA - 1999/12/15/ PY - 1999/12/15/ DO - 10.1103/physrevb.60.r16338 VL - 60 IS - 24 SP - R16338-R16341 SN - 2469-9969 ER - TY - JOUR TI - Linear optical properties of Si surfaces and nanostructures AU - Rossow, U. AU - Mantese, L. AU - Aspnes, D. E. AU - Bell, K. A. AU - Ebert, M. T2 - Physica Status Solidi. B, Basic Solid State Physics DA - 1999/// PY - 1999/// VL - 215 IS - 1 SP - 725-729 ER - TY - JOUR TI - Influence of microstructure size on the plastic deformation kinetics, fatigue crack growth rate, and low-cycle fatigue of solder joints AU - Conrad, H AU - Guo, Z AU - Fahmy, Y AU - Yang, D T2 - JOURNAL OF ELECTRONIC MATERIALS DA - 1999/9// PY - 1999/9// DO - 10.1007/s11664-999-0184-x VL - 28 IS - 9 SP - 1062-1070 SN - 0361-5235 KW - solder joints KW - low cycle fatigue KW - microstructure KW - deformation kinetics ER - TY - JOUR TI - High-resolution spectroscopy with reciprocal-space analysis AU - Aspnes, DE AU - Yoo, SD T2 - PHYSICA STATUS SOLIDI B-BASIC RESEARCH AB - Optical spectra can be analyzed more accurately for critical point energies and other parameters in reciprocal space than in direct space because baseline effects, information, and noise are effectively isolated in the low-, medium-, and high-index Fourier coefficients, respectively. However, the requirement that the spectral segment being analyzed is periodic usually gives rise to large contributions to the coefficients from the value and slope discontinuities at the wrapped ends of the segment. Previously, the effect of these discontinuities was reduced with false data in direct space. Here, we show that these artifacts can be removed more effectively in reciprocal space, and that the process is optimized when the number of data points in the segment equals the number of points in the transformation, i.e., when no false data are required. Our approach reduces reciprocal-space analysis of optical spectra to a routine process, as demonstrated by application to crystalline Si. DA - 1999/9// PY - 1999/9// DO - 10.1002/(sici)1521-3951(199909)215:1<715::aid-pssb715>3.0.co;2-g VL - 215 IS - 1 SP - 715-723 SN - 0370-1972 ER - TY - JOUR TI - High-energy cryogenic blending and compatibilizing of immiscible polymers AU - Smith, AP AU - Spontak, RJ AU - Ade, H AU - Smith, SD AU - Koch, CC T2 - ADVANCED MATERIALS AB - Low-temperature mechanical alloying of immiscible polymers is investigated as a viable solid-state alternative to blending using melt or solution processes. The Figure is a schematic diagram of the alloying—or high-energy ball-milling—process, indicating that reactive chain coupling may occur in the event of free-radical generation due to chain scission. DA - 1999/10/20/ PY - 1999/10/20/ DO - 10.1002/(SICI)1521-4095(199910)11:15<1277::AID-ADMA1277>3.0.CO;2-9 VL - 11 IS - 15 SP - 1277-+ SN - 1521-4095 ER - TY - PAT TI - Halo-zeo-type materials AU - Martin, J. D. AU - Greenwood, K. C2 - 1999/// DA - 1999/// PY - 1999/// ER - TY - JOUR TI - Germanium segregation in the Co/SiGe/Si(001) thin film system AU - Goeller, PT AU - Boyanov, BI AU - Sayers, DE AU - Nemanich, RJ AU - Myers, AF AU - Steel, EB T2 - JOURNAL OF MATERIALS RESEARCH DA - 1999/11// PY - 1999/11// DO - 10.1557/JMR.1999.0592 VL - 14 IS - 11 SP - 4372-4384 SN - 0884-2914 ER - TY - JOUR TI - Field emission properties of nitrogen-doped diamond films AU - Sowers, AT AU - Ward, BL AU - English, SL AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - This study explores the field emission properties of nitrogen-doped diamond grown by microwave plasma chemical vapor deposition. Over 70 nitrogen-doped diamond samples were grown on silicon and molybdenum under varying process conditions. Under certain conditions, films can be grown which exhibit photoluminescence bands at 1.945 and 2.154 eV that are attributed to single substitutional nitrogen. Photoelectron emission microscopy with UV free electron laser excitation indicated a 0 or negative electron affinity. Field emission characteristics were measured in an ultrahigh vacuum with a variable distance anode technique. For samples grown with gas phase [N]/[C] ratios less than 10, damage from microarcs occurred during the field emission measurements. Samples grown at higher [N]/[C] content could be measured prior to an arcing event. Contrary to other reports on nitrogen-doped diamond, these measurements indicate relatively high threshold fields (&gt;100 V/μm) for electron emission. We suggest that the nitrogen in these films is compensated by defects. A defect-enhanced electron emission model from these films is discussed. DA - 1999/10/1/ PY - 1999/10/1/ DO - 10.1063/1.371316 VL - 86 IS - 7 SP - 3973-3982 SN - 1089-7550 ER - TY - JOUR TI - Direct acceleration of pickup ions at the solar wind termination shock: The production of anomalous cosmic rays AU - Ellison, DC AU - Jones, FC AU - Baring, MG T2 - ASTROPHYSICAL JOURNAL AB - We have modeled the injection and acceleration of pickup ions at the solar wind termination shock and investigated the parameters needed to produce the observed anomalous cosmic-ray (ACR) fluxes. A nonlinear Monte Carlo technique was employed that in effect solves the Boltzmann equation and is not restricted to near-isotropic particle distribution functions. This technique models the injection of thermal and pickup ions, the acceleration of these ions, and the determination of the shock structure under the influence of the accelerated ions. The essential effects of injection are treated in a mostly self-consistent manner, including effects from shock obliquity, cross-field diffusion, and pitch-angle scattering. Using recent determinations of pickup ion densities, we are able to match the absolute flux of hydrogen in the ACRs by assuming that pickup ion scattering mean free paths, at the termination shock, are much less than an AU and that modestly strong cross-field diffusion occurs. Simultaneously, we match the flux ratios He+/H+ or O+/H+ to within a factor ~5. If the conditions of strong scattering apply, no pre-termination-shock injection phase is required and the injection and acceleration of pickup ions at the termination shock are totally analogous to the injection and acceleration of ions at highly oblique interplanetary shocks recently observed by the Ulysses spacecraft. The fact that ACR fluxes can be modeled with standard shock assumptions suggests that the much discussed "injection problem" for highly oblique shocks stems from incomplete (either mathematical or computer) modeling of these shocks rather than from any actual difficulty shocks may have in injecting and accelerating thermal or quasi-thermal particles. DA - 1999/2/10/ PY - 1999/2/10/ DO - 10.1086/306739 VL - 512 IS - 1 SP - 403-416 SN - 0004-637X KW - cosmic rays KW - methods : numerical KW - shock waves KW - solar wind ER - TY - JOUR TI - Core excitation spectroscopy of stable cyclic diaminocarbenes, -silylenes, and -germylenes AU - Lehmann, JF AU - Urquhart, SG AU - Ennis, LE AU - Hitchcock, AP AU - Hatano, K AU - Gupta, S AU - Denk, MK T2 - ORGANOMETALLICS AB - A number of tert-butyl-substituted, cyclic, saturated and unsaturated diaminocarbene, diaminosilylene, and diaminogermylene compounds were investigated using inner shell electron energy loss spectroscopy (ISEELS) and ab initio calculations. These compounds, each of which contains a divalent group 14 element (C, Si, Ge), are of particular interest since they are stable indefinitely, and thus, they are readily accessible for detailed spectroscopic analysis. The C 1s and N 1s spectra of the hydrogenated tetravalent analogues of the saturated carbene, of di-tert-butyldiazabutadiene, and of di-tert-butyldiazabutane were also obtained to assist with spectral interpretation. Our analysis shows that there is significant π-allyl delocalization over the N−EII−N fragment in all three species. Further, in the unsaturated species there is additional aromatic delocalization. Both theory and experiment indicate that the divalent center of the carbene is qualitatively different from that in the germylenes or silylenes. DA - 1999/5/10/ PY - 1999/5/10/ DO - 10.1021/om980882z VL - 18 IS - 10 SP - 1862-1872 SN - 0276-7333 ER - TY - JOUR TI - Comment on "Ab initio calculation of excitonic effects in the optical spectra of semiconductors" AU - Cardona, M AU - Lastras-Martinez, LF AU - Aspnes, DE T2 - PHYSICAL REVIEW LETTERS AB - A Comment on the Letter by Stefan Albrecht, Lucia Reining, Rodolfo Del Sole, and Giovanni Onida, Phys. Rev. Lett. 80, 4510 (1998). The authors of the Letter offer a Reply.Received 30 April 1999DOI:https://doi.org/10.1103/PhysRevLett.83.3970©1999 American Physical Society DA - 1999/11/8/ PY - 1999/11/8/ DO - 10.1103/PhysRevLett.83.3970 VL - 83 IS - 19 SP - 3970-3970 SN - 1079-7114 ER - TY - JOUR TI - Chloride uptake by oxide covered aluminum as determined by X-ray photoelectron and X-ray absorption spectroscopy AU - Natishan, PM AU - WE O'Grady, AU - McCafferty, E AU - Ramaker, DE AU - Pandya, K AU - Russell, A T2 - JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB - The uptake of chloride by aluminum polarized at potentials below (less positive than) the pitting potential in 0.1 M NaCl solutions was studied using X‐ray photoelectron spectroscopy (XPS) and X‐ray absorption spectroscopy (XAS). The XPS chloride spectra showed that two distinct sets of doublets are present. One doublet is related to chloride on the surface and the second is related to chloride incorporated in the oxide film. In the case of XAS, deconvolution of the spectrum obtained for samples polarized below the pitting potential also showed the presence of chloride in the near surface region and in the oxide film. The important point of this work is that the observed chloride was present in two different chemical environments as determined with both XAS and XPS. © 1999 The Electrochemical Society. All rights reserved. DA - 1999/5// PY - 1999/5// DO - 10.1149/1.1391835 VL - 146 IS - 5 SP - 1737-1740 SN - 0013-4651 ER - TY - JOUR TI - Canonical quasilocal energy and small spheres AU - Brown, JD AU - Lau, , SR AU - York, JW T2 - PHYSICAL REVIEW D AB - Consider the definition E of quasilocal energy stemming from the Hamilton-Jacobi method as applied to the canonical form of the gravitational action. We examine E in the standard "small-sphere limit," first considered by Horowitz and Schmidt in their examination of Hawking's quasilocal mass. By the term "small sphere" we mean a cut S(r), level in an affine radius r, of the lightcone belonging to a generic spacetime point. As a power series in r, we compute the energy E of the gravitational and matter fields on a spacelike hypersurface spanning S(r). Much of our analysis concerns conceptual and technical issues associated with assigning the zero-point of the energy. For the small-sphere limit, we argue that the correct zero-point is obtained via a "lightcone reference," which stems from a certain isometric embedding of S(r) into a genuine lightcone of Minkowski spacetime. Choosing this zero-point, we find agreement with Hawking's quasilocal mass expression, up to and including the first non-trivial order in the affine radius. The vacuum limit relates the quasilocal energy directly to the Bel-Robinson tensor. DA - 1999/3/15/ PY - 1999/3/15/ DO - 10.1103/physrevd.59.064028 VL - 59 IS - 6 SP - SN - 0556-2821 UR - http://inspirehep.net/record/477238 ER - TY - JOUR TI - An optimized process for fabrication of SrBi2Ta2O9 thin films using a novel chemical solution deposition technique AU - Kim, SH AU - Kim, DJ AU - Lee, KM AU - Park, M AU - Kingon, AI AU - Nemanich, RJ AU - Im, J AU - Streiffer, SK T2 - JOURNAL OF MATERIALS RESEARCH DA - 1999/11// PY - 1999/11// DO - 10.1557/JMR.1999.0594 VL - 14 IS - 11 SP - 4395-4401 SN - 0884-2914 ER - TY - JOUR TI - Ad-dimers on strained carbon nanotubes: A new route for quantum dot formation? AU - Orlikowski, D AU - Nardelli, MB AU - Bernholc, J AU - Roland, C T2 - PHYSICAL REVIEW LETTERS AB - The presence of ad-dimers on carbon nanotubes under tension leads to the formation of defects that wrap themselves around the circumference of the nanotube. These defects are actually short segments of a tube with a changed helicity, which suggests that the combination of ad-dimers plus strain can be used to form nanotube-based quantum dots. Our classical molecular dynamics and tight binding simulations show that the formation of such structures is particularly clean and promising for the $\left(n,0\right)$ zigzag tubes, where the presence of ad-dimers induces plastic transformations on what are otherwise brittle tubes. DA - 1999/11/15/ PY - 1999/11/15/ DO - 10.1103/PhysRevLett.83.4132 VL - 83 IS - 20 SP - 4132-4135 SN - 0031-9007 ER - TY - JOUR TI - Wave speeds for an elastoplastic model for two-dimensional deformations with a nonassociative flow rule AU - Gordon, M AU - Garaizar, FX T2 - QUARTERLY OF APPLIED MATHEMATICS AB - A system of partial differential equations describing elastoplastic deformations in two space dimensions is studied. The constitutive relations for plastic deformation include a nonassociative flow rule and shear strain hardening. After a change of variables, the characteristic speeds of plane wave solutions of the system are computed. For both plastic and elastic deformations, there are two nonzero wave speeds, referred to as DA - 1999/6// PY - 1999/6// DO - 10.1090/qam/1686188 VL - 57 IS - 2 SP - 245-259 SN - 0033-569X ER - TY - JOUR TI - Thermochemical stability of silicon-oxygen-carbon alloy thin films: A model system for chemical and structural relaxation at SiC-SiO2 interfaces AU - Wolfe, DM AU - Hinds, BJ AU - Wang, F AU - Lucovsky, G AU - Ward, BL AU - Xu, M AU - Nemanich, RJ AU - Maher, DM T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS AB - Alloy thin films of hydrogenated silicon–oxygen–carbon (Si,C)Ox x&lt;2, were deposited and analyzed in terms of changes in structure and bonding as a function of rapid thermal annealing between 600 and 1100 °C using a combination of Fourier transform infrared spectroscopy, Raman scattering and high-resolution transmission electron microscopy. Results showed that three structural/chemical transformations took place upon annealing. The initial reaction (600–800 °C) involved the loss of hydrogen bonded to both silicon and carbon. At intermediate temperatures (900–1000 °C) a Si–O–C type bond was observed to form, and subsequently disappear after annealing to 1050 °C. The formation of ordered amorphous-SiC regions, nanocrystalline-Si regions, and stoichiometric, thermally relaxed SiO2 accompanied the disappearance of the Si–O–C bond at the 1050 °C annealing temperature. Using this alloy as a model system, important information is obtained for optimized processing of SiC–SiO2 interfaces for device applications. DA - 1999/// PY - 1999/// DO - 10.1116/1.581745 VL - 17 IS - 4 SP - 2170-2177 SN - 0734-2101 ER - TY - JOUR TI - Tailoring of optical phonon modes in nanoscale semiconductor structures: role of interface-optical phonons in quantum-well lasers AU - Belenky, G AU - Dutta, M AU - Gorfinkel, VB AU - Haddad, GI AU - Iafrate, GJ AU - Kim, KW AU - Kisin, M AU - Luryi, S AU - Stroscio, MA AU - Sun, JP AU - Teng, HB AU - Yu, SG T2 - PHYSICA B-CONDENSED MATTER AB - This paper discusses the concept of enhancing semiconductor laser performance through tailoring of scattering rates of confined polar-optical phonons. Studies of optically pumped intersubband scattering in coupled quantum-well lasers have demonstrated that interface-phonon-assisted transitions are important in such structures; furthermore, simple analytical expressions have been derived that indicate the importance of interface-phonon scattering in quantum-well lasers. These calculations reveal that the interface-phonon-assisted transitions are dominant for small quantum well dimensions of approximately 40 Å; such dimensions are typical of novel lasers including both the unipolar quantum cascade laser and the tunneling injection laser. Recent numerical calculations have confirmed these effects and have extended them to indicate how confined and interface phonons also affect critical laser properties such as optical gain. The application of confined phonon effects to intersubband lasers is one of the most important applications of confined-phonon physics to the present time. DA - 1999/3// PY - 1999/3// DO - 10.1016/S0921-4526(98)01410-0 VL - 263 SP - 462-465 SN - 1873-2135 KW - interface phonons KW - quantum-well lasers KW - phonon confinement KW - phonon-assisted transitions ER - TY - JOUR TI - Superdeformation and prolate-oblate competition in T1 nuclei AU - Reviol, W. AU - Riedinger, L. L. AU - Smith, B. H. AU - Bingham, C. R. AU - Weintraub, W. AU - Carpenter, M. P. AU - Janssens, R. V. F. AU - Fischer, S. M. AU - Nisius, D. AU - Seweryniak, D. AU - Jenkins, D. AU - Wadsworth, R. AU - Wilson, A. N. AU - Moore, E. F. T2 - Acta Physica Polonica. B DA - 1999/// PY - 1999/// VL - 30 IS - 3 SP - 723-732 ER - TY - JOUR TI - Phase instability and electron-assisted renormalization of acoustic phonon spectrum in free-standing quantum wires AU - Komirenko, SM AU - Kim, KW AU - Kochelap, VA AU - Dutta, M AU - Stroscio, MA T2 - PHYSICA B AB - Abstract In this paper we consider the possibility of a Peierls phase transition for a system of one-dimensional electrons and acoustic phonons confined in a free-standing quantum wire (FSQWI). We assume that electrons and phonons are coupled via the deformation potential interaction. The dispersion relation for this system is derived taking into account the role of electrostatic effects. The Peierls phase transition to the state characterized by periodic lattice deformation (PLD) is obtained in the high-permittivity limit. The formalism developed in this paper facilitates investigation of the renormalized acoustic phonon spectrum and predicts the possibility of the Peierls transition in FSQWIs fabricated from semiconductor materials with large permittivity. DA - 1999/3// PY - 1999/3// DO - 10.1016/s0921-4526(98)01253-8 VL - 263 SP - 522-525 SN - 0921-4526 KW - coupled excitation KW - phase instability KW - electron-phonon interaction ER - TY - JOUR TI - Finite difference schemes and block Rayleigh quotient iteration for electronic structure calculations on composite grids AU - Fattebert, JL T2 - JOURNAL OF COMPUTATIONAL PHYSICS AB - We present an original numerical method to discretize the Kohn–Sham equations by a finite difference scheme in real-space when computing the electronic structure of a molecule. The singular atomic potentials are replaced by pseudopotentials and the discretization of the 3D problem is done on a composite mesh refined in part of the domain. A “Mehrstellenverfahren” finite difference scheme is used to approximate the Laplacian on the regular parts of the grid. The nonlinearity of the potential operator in the Kohn–Sham equations is treated by a fixed point algorithm. At each step an iterative scheme is applied to determine the searched solutions of the eigenvalue problem for a given fixed potential. The eigensolver is a block generalization of the Rayleigh quotient iteration which uses Petrov–Galerkin approximations. The algorithm is adapted to a multigrid resolution of the linear systems obtained in the inverse iterations. Numerical tests of the different algorithms are presented on problems coming from the electronic structure calculation of some molecules. DA - 1999/2/10/ PY - 1999/2/10/ DO - 10.1006/jcph.1998.6138 VL - 149 IS - 1 SP - 75-94 SN - 0021-9991 KW - Rayleigh quotient iteration KW - multigrid method KW - finite differences KW - mesh refinement KW - electronic structure calculations KW - Kohn-Sham equations ER - TY - JOUR TI - Electronic near-surface defect states of bare and metal covered n-GaN films observed by cathodoluminescence spectroscopy AU - Young, AP AU - Schafer, J AU - Brillson, LJ AU - Yang, Y AU - Xu, SH AU - Cruguel, H AU - Lapeyre, GJ AU - Johnson, MAL AU - Schetzina, JF T2 - JOURNAL OF ELECTRONIC MATERIALS DA - 1999/3// PY - 1999/3// DO - 10.1007/s11664-999-0032-z VL - 28 IS - 3 SP - 308-313 SN - 0361-5235 KW - defects states KW - n-GaN KW - Schottky barrier ER - TY - JOUR TI - Dielectric function of Cd0.57Mg0.43Te alloy film studied by ellipsometry AU - Kim, T. J. AU - Kim, Y. D. AU - Yoo, S. D. AU - Aspnes, D. E. AU - Kossut, J. T2 - Journal of the Korean Physical Society DA - 1999/// PY - 1999/// VL - 34 IS - 1999 June SP - S496-498 ER - TY - JOUR TI - Confined phonon and phonon-mode properties of III-V nitrides with wurtzite crystal structure AU - Alexson, D AU - Bergman, L AU - Dutta, M AU - Kim, KW AU - Komirenko, S AU - Nemanich, RJ AU - Lee, BC AU - Stroscio, MA AU - Yu, SG T2 - PHYSICA B AB - Stimulated by the recent interest in the use of nitride-based III–V wurtzite structures for optoelectronic and electronic devices, this paper reports on the application of the Loudon model for uniaxial crystals to derive the Fröhlich interaction Hamiltonian as well as the electron–optical-phonon scattering rate in wurtzite crystals. This paper also presents experimental analyses of the mode behavior of phonons in wurtzite crystals. DA - 1999/3// PY - 1999/3// DO - 10.1016/s0921-4526(98)01423-9 VL - 263 SP - 510-513 SN - 0921-4526 KW - phonons in wurtzite structures KW - Loudon model KW - nitride-based III-V structures ER - TY - JOUR TI - Bonding constraints and defect formation at interfaces between crystalline silicon and advanced single layer and composite gate dielectrics AU - Lucovsky, G AU - Wu, Y AU - Niimi, H AU - Misra, V AU - Phillips, JC T2 - APPLIED PHYSICS LETTERS AB - An increasingly important issue in semiconductor device physics is understanding of how departures from ideal bonding at silicon–dielectric interfaces generate electrically active defects that limit performance and reliability. Building on previously established criteria for formation of low defect density glasses, constraint theory is extended to crystalline silicon–dielectric interfaces that go beyond Si–SiO2 through development of a model that quantifies average bonding coordination at these interfaces. This extension is validated by application to interfaces between Si and stacked silicon oxide/nitride dielectrics demonstrating that as in bulk glasses and thin films, an average coordination, Nav, greater than three yields increasing defective interfaces. DA - 1999/4/5/ PY - 1999/4/5/ DO - 10.1063/1.123728 VL - 74 IS - 14 SP - 2005-2007 SN - 1077-3118 ER - TY - JOUR TI - Apparatus for parity-violation study via capture gamma-ray measurements AU - Seestrom, SJ AU - Frankle, CM AU - Bowman, JD AU - Crawford, BC AU - Haseyama, T AU - Masaike, A AU - Matsuda, A AU - Penttila, SI AU - Roberson, RN AU - Sharapov, EI AU - Stephenson, SL T2 - NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB - The Time Reversal and Parity at Low Energy (TRIPLE) Collaboration uses a short-pulsed longitudinally polarized epithermal neutron beam at the Los Alamos Neutron Science Center to study spatial parity violation (PV) in the compound nucleus. The typical PV experiment measures the longitudinal cross-section asymmetry by the neutron transmission method through thick samples. Neutron capture γ-ray measurement provides an alternative method for the study of PV, which enables the use of smaller amounts of isotopically pure target material. In 1995 TRIPLE commissioned a new neutron-capture detector consisting of 24 pure CsI scintillators arranged in a cylindrical geometry around the neutron beam. The characteristics and the performance of the detector and spin transport are described. DA - 1999/9/1/ PY - 1999/9/1/ DO - 10.1016/S0168-9002(99)00481-7 VL - 433 IS - 3 SP - 603-613 SN - 1872-9576 KW - CsI-pure detector array KW - polarized neutrons KW - parity violation ER - TY - JOUR TI - Proximal electromagnetic shear forces AU - Ayars, E. AU - Aspnes, D. E. AU - Moyer, P. AU - Paesler, M. A. T2 - Journal of Microscopy AB - We perform a simple model calculation to estimate the electromagnetically induced shear force caused by a current dissipation when a charged tip is moved parallel to a conducting material. For parameters typical in shear force imaging, the force is many orders of magnitude below reported values. Thus, proximal electromagnetic tip-sample forces can be neglected in discussions of shear force imaging. DA - 1999/// PY - 1999/// DO - 10.1046/j.1365-2818.1999.00596.x VL - 196 IS - 1 SP - 59–60 ER - TY - JOUR TI - Parity violation in the compound nucleus AU - Mitchell, GE AU - Bowman, JD AU - Weidenmuller, HA T2 - REVIEWS OF MODERN PHYSICS AB - Parity violation in the compound nucleus is reviewed as an example of a wider class of phenomena: The breaking of a discrete symmetry by a weak interaction in a stochastic or chaotic quantum system. Generically, enhancement factors amplify the signal for symmetry breaking, and the stochastic properties allow the strength of the symmetry-breaking interaction to be inferred from that signal without the need to know the wave functions of individual states. We describe recent experiments on parity violation that have been undertaken in this spirit. The scattering of spin-polarized neutrons by medium-weight and heavy nuclei provides signals for parity violation at the percent level. The statistical analysis of the data yields values for the spreading width around ${10}^{\ensuremath{-}6}\mathrm{eV},$ in keeping with theoretical expectations. We discuss open problems and possible future directions. DA - 1999/1// PY - 1999/1// DO - 10.1103/RevModPhys.71.445 VL - 71 IS - 1 SP - 445-457 SN - 1539-0756 ER - TY - JOUR TI - Measurement of piezoelectric displacements of Pb(Zr, Ti)O-3 thin films using a double-beam interferometer AU - Maiwa, H AU - Christman, JA AU - Kim, SH AU - Kim, DJ AU - Maria, JP AU - Chen, B AU - Streiffer, SK AU - Kingon, AI T2 - JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS AB - The double-beam interferometric method is applied to measure the field-induced displacement of Pb(Zr, Ti)O 3 thin films. The dc electric field dependence of the longitudinal piezoelectric coefficient ( d 33 ) response of Pb(Zr, Ti)O 3 thin films deposited by metal organic chemical vapor deposition (MOCVD) was measured. Experimental d 33 values were compared with coefficients calculated using a phenomenological approach and bulk parameters. Qualitative agreement was obtained between measured and calculated coefficients. DA - 1999/9// PY - 1999/9// DO - 10.1143/jjap.38.5402 VL - 38 IS - 9B SP - 5402-5405 SN - 0021-4922 KW - piezoelectric properties KW - double-beam interferometry KW - PZT KW - MEMS KW - AFM ER - TY - JOUR TI - Heavy hybrids with constituent gluons - art. no. 014035. AU - Swanson, E. S. AU - Szczepaniak, A. P. T2 - Physical Review. D, Particles and Fields DA - 1999/// PY - 1999/// VL - 5901 IS - 1 SP - 4035- ER - TY - JOUR TI - Growth of epitaxial CoSi2 on SiGe(001) AU - Boyanov, BI AU - Goeller, PT AU - Sayers, DE AU - Nemanich, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - A technique for achieving epitaxial growth of (001)-oriented CoSi2 on strained epitaxial layers of Si1−xGex(001) is described. The technique is based on a variation of the template method, and is designed to control the local environment of Co atoms at the CoSi2/SiGe interface. The effects of the Co–Ge interactions on the interfacial reaction and the epitaxial orientation and the morphology of the silicide film were investigated. This reaction was found to cause pitting in (001)-oriented CoSi2 films, and to stabilize the (221¯) orientation for films codeposited under conditions where CoSi2(001) growth is achieved on Si(001) substrates. The (221¯)-oriented CoSi2 films were islanded after annealing at 700 °C. The islands were terminated by (1¯11) and (110) facets inclined at 15.8° and 19.5°, respectively, from CoSi2 [221¯] towards CoSi2 [114]. These results were interpreted in terms of reduction of interfacial and surface energies, and geometric effects. Silicide films up to 730-Å-thick were deposited and annealed up to 900 °C. The films were stable against agglomeration, and retained tensile stress in the CoSi2 layer after annealing at 700 °C. The rms roughness of the CoSi2 films was comparable to that of the Si(001) substrate—less than 15 Å over areas as large as 20×20 μm2. Films annealed at 900°C were severely agglomerated. DA - 1999/8/1/ PY - 1999/8/1/ DO - 10.1063/1.370894 VL - 86 IS - 3 SP - 1355-1362 SN - 0021-8979 ER - TY - JOUR TI - XAFS study of adsorbed and mineral forms of phosphate AU - Hesterberg, D AU - Zhou, WQ AU - Hutchison, KJ AU - Beauchemin, S AU - Sayers, DE T2 - JOURNAL OF SYNCHROTRON RADIATION DA - 1999/5/1/ PY - 1999/5/1/ DO - 10.1107/S0909049599000370 VL - 6 SP - 636-638 SN - 0909-0495 KW - XANES KW - phosphorus KW - speciation KW - soil ER - TY - JOUR TI - Time dependent dielectric wearout (TDDW) technique for reliability of ultrathin gate oxides AU - Wu, YD AU - Xiang, Q AU - Bang, D AU - Lucovsky, G AU - Lin, MR T2 - IEEE ELECTRON DEVICE LETTERS AB - The degradation of ultrathin oxides is measured and characterized by the dual voltage time dependent dielectric wearout (TDDW) technique. Compared to the conventional time-dependent dielectric breakdown (TDDB) technique, a distinct breakdown can be determined at the operating voltage I-t curve. A noisy, soft prebreakdown effect occurs for 1.8-2.7 nm ultrathin oxides at earlier stress times. The different stages of wearout of 1.8-2.7 nm oxides are discussed. The wearout of oxide is defined when the gate current reaches a critical current density at the circuit operating voltage. Devices still function after the soft breakdowns occur, but are not functional after the sharp breakdown. However, application of the E model to project the dielectric lifetime shows that this is more than 20 y for thermal oxides in the ultrathin regime down to 1.8 nm. DA - 1999/6// PY - 1999/6// DO - 10.1109/55.767092 VL - 20 IS - 6 SP - 262-264 SN - 0741-3106 KW - reliability TDDB KW - TDDW KW - ultrathin oxide ER - TY - JOUR TI - Thermodynamic perturbation theory for polydisperse colloidal suspensions using orthogonal polynomial expansions AU - Leroch, S AU - Kahl, G AU - Lado, F T2 - PHYSICAL REVIEW E AB - We present a method for calculating the thermodynamic and structural properties of a polydisperse liquid by means of a thermodynamic perturbation theory: the optimized random phase approximation (ORPA). The approach is an extension of a method proposed recently by one of us for an integral equation application [Phys. Rev. E 54, 4411 (1996)]. The method is based on expansions of all $\ensuremath{\sigma}$-dependent functions in the orthogonal polynomials ${p}_{i}(\ensuremath{\sigma})$ associated with the weight function ${f}_{\ensuremath{\Sigma}}(\ensuremath{\sigma})$, where $\ensuremath{\sigma}$ is a random variable (in our case the size of the particles) with distribution ${f}_{\ensuremath{\Sigma}}(\ensuremath{\sigma})$. As in the one-component or general $\mathcal{N}$-component case, one can show that the solution of the ORPA is equivalent to the minimization of a suitably chosen functional with respect to variations of the direct correlation functions. To illustrate the method, we study a polydisperse system of square-well particles; extension to other hard-core or soft-core systems is straightforward. DA - 1999/6// PY - 1999/6// DO - 10.1103/physreve.59.6937 VL - 59 IS - 6 SP - 6937-6945 SN - 2470-0053 ER - TY - JOUR TI - The effects of interfacial suboxide transition regions on direct tunneling in oxide and stacked oxide-nitride gate dielectrics AU - Yang, H AU - Niimi, H AU - Wu, Y AU - Lucovsky, G AU - Keister, JW AU - Rowe, JE T2 - MICROELECTRONIC ENGINEERING AB - This paper builds on previous work that has demonstrated the effects of interfacial suboxide transition regions at SiSiO2 interfaces on tunneling oscillations in the Fowler-Nordheim regime. This paper extends thes effects to the direct tunneling regime and focuses on differences in interfacial transition regions between SiSiO2 interfaces with, and without monolayer level interface nitridation. Tunneling currents in devices with the same oxide-equivalent thickness are reduced by monolayer level interfacial nitrogen with respect to devices without interface nitridation for i) substrate and gate injection and ii) in both the direct and Fowler-Nordheim tunneling regimes. DA - 1999/9// PY - 1999/9// DO - 10.1016/s0167-9317(99)00395-0 VL - 48 IS - 1-4 SP - 307-310 SN - 0167-9317 ER - TY - JOUR TI - The effects of chemical bonding and band offset constraints at Si-dielectric interfaces on the integration of alternative high-K dielectrics into aggressively-scaled CMOS Si devices AU - Lucovsky, G AU - Phillips, JC T2 - MICROELECTRONIC ENGINEERING AB - This paper identifies three aspects of the chemical bonding at Si-dielectric interfaces that play crucial roles in the implementation of alternative gate dielectrics for advanced CMOS Si devices: i) the character of the interface bonds, either isovalent with bond and nuclear charge balanced as in SiSiO2, or heterovalent, with an inherent mismatch between bond and nuclear charge, ii) physical bonding constraints related to the average number of bonds/atom, Nav, and iii) reduced conduction band offset energies that are result because of increased ionic bonding and d-state derived conduction bands in transition metal oxides. DA - 1999/9// PY - 1999/9// DO - 10.1016/s0167-9317(99)00391-3 VL - 48 IS - 1-4 SP - 291-294 SN - 0167-9317 ER - TY - JOUR TI - The effect of germanium on the Co-SiGe thin-film reaction AU - Boyanov, BI AU - Goeller, PT AU - Sayers, DE AU - Nemanich, RJ T2 - JOURNAL OF SYNCHROTRON RADIATION AB - Ge Co Germanium was found to have a strong influence on the path and products of the Co-SiGe reaction, and on the interfacial stability and crystallographic orientation of the silicide film. The segregation of Ge that occurs during the reaction of blanket Co films with SiGe results in thickness effects not present in the reaction of Co with Si. The thickness effect was modelled in terms of the energy cost of Ge segregation, and good agreement with experimental results was obtained. In s i tu EXAFS experiments on sub-monolayer Co films annealed on SiGe substrates indicate a strong preference for the formation of Co-Si bonds at the silicide-SiGe interface. The implications of these results for the stability of the interface and the epitaxial orientation of co-deposited cobalt disilicide (CoSi2) films will be discussed. DA - 1999/5/1/ PY - 1999/5/1/ DO - 10.1107/S0909049599000060 VL - 6 SP - 521-523 SN - 0909-0495 KW - cobalt silicide KW - silicon-germanium KW - thickness effects KW - interfacial bonding KW - molecular beam epitaxy ER - TY - JOUR TI - Suppression of boron transport out of p(+) polycrystalline silicon at polycrystalline silicon dielectric interfaces AU - Wu, Y. AU - Niimi, H. AU - Yang, H. AU - Lucovsky, G. AU - Fair, R. B. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 1999/// PY - 1999/// VL - 17 IS - 4 SP - 1813-1822 ER - TY - JOUR TI - Stability of copper sulfide in a contaminated soil AU - Zhou, WQ AU - Hesterberg, D AU - Hansen, PD AU - Hutchison, KJ AU - Sayers, DE T2 - JOURNAL OF SYNCHROTRON RADIATION DA - 1999/5/1/ PY - 1999/5/1/ DO - 10.1107/S0909049599001776 VL - 6 SP - 630-632 SN - 0909-0495 KW - X-ray absorption KW - XAFS KW - environmental ER - TY - JOUR TI - Spin parity of the 7.478 MeV state of B-10 and the S factor of the Be-9((p)over-right-arrow,gamma(0))B-10 reaction AU - Gaff, SJ AU - Canon, RS AU - Kelley, JH AU - Nelson, SO AU - Sabourov, K AU - Schreiber, EC AU - Tilley, DR AU - Weller, HR AU - Wulf, EA T2 - PHYSICAL REVIEW C AB - Polarized protons were used to measure the analyzing power of $\mathrm{the}{}^{9}\mathrm{Be}(\stackrel{\ensuremath{\rightarrow}}{p},\ensuremath{\gamma}{)}^{10}\mathrm{B}$ reaction for ${E}_{p}=280--0 \mathrm{keV}.$ The analyzing power for the ground state transition compared to calculations leads to a spin-parity assignment of ${2}^{+}$ for the 7.478 MeV state of ${}^{10}\mathrm{B}.$ This ${2}^{+}$ assignment is consistent with other observables for this reaction and is predicted by cluster and shell model calculations. It is found that the ${2}^{+}$ assignment leads to a value for the astrophysical S factor for capture to the ground state of ${}^{10}\mathrm{B}$ of $S(0)=0.20 \mathrm{keV}\mathrm{}\mathrm{b}$ which is about 40% smaller than that obtained with a ${2}^{\ensuremath{-}}$ assignment. DA - 1999/6// PY - 1999/6// DO - 10.1103/physrevc.59.3425 VL - 59 IS - 6 SP - 3425-3428 SN - 1089-490X ER - TY - JOUR TI - Raman analysis of phonon lifetimes in AlN and GaN of wurtzite structure AU - Bergman, L AU - Alexson, D AU - Murphy, PL AU - Nemanich, RJ AU - Dutta, M AU - Stroscio, MA AU - Balkas, C AU - Shin, H AU - Davis, RF T2 - PHYSICAL REVIEW B AB - Raman analyses of the lifetimes of phonons in GaN and AlN crystallites of wurtzite structure are presented. In order to ensure the accuracy of the measurement of the phonon lifetimes, an experimental procedure to eliminate the broadening due to the finite slit width was performed. The lifetime analyses indicate that the phonon lifetimes in AlN as well as in GaN fall into two main time regimes: a relatively long time of the ${E}_{2}^{1}$ mode and much shorter times of the ${E}_{2}^{2},$ $E1(\mathrm{TO}),$ and $A1(\mathrm{TO})$ modes. The lifetimes of the ${E}_{2}^{1},$ ${E}_{2}^{2},$ $E1(\mathrm{TO}),$ $A1(\mathrm{TO}),$ and $A1(\mathrm{LO})$ modes of an high-quality AlN crystallite are 4.4, 0.83, 0.91, 0.76, and 0.45 ps, respectively. Moreover, the lifetime of the $A1(\mathrm{LO})$ mode found in this study is consistent with the current phonon-decay model of that mode in wurtzite structure materials. The lifetimes of ${E}_{2}^{1},$ ${E}_{2}^{2},$ $E1(\mathrm{TO}),$ and $A1(\mathrm{TO})$ of a GaN crystallite were found to be 10.1, 1.4, 0.95, and 0.46 ps, respectively. The $A1(\mathrm{LO})$ mode in the GaN was not observed and its absence is attributed to plasmon damping. The lifetime shortening due to impurities was also studied: the lifetimes of the Raman modes of an AlN crystallite, which contains about two orders of magnitude more Si and C impurities relative to the concentration of the high-quality crystallite were found to be 50% shorter. DA - 1999/5/15/ PY - 1999/5/15/ DO - 10.1103/physrevb.59.12977 VL - 59 IS - 20 SP - 12977-12982 SN - 1550-235X ER - TY - JOUR TI - Radio to gamma-ray emission from shell-type supernova remnants: Predictions from nonlinear shock acceleration models AU - Baring, MG AU - Ellison, DC AU - Reynolds, SP AU - Grenier, IA AU - Goret, P T2 - ASTROPHYSICAL JOURNAL AB - Supernova remnants (SNRs) are widely believed to be the principal source of Galactic cosmic rays, produced by diffusive shock acceleration in the environs of the remnant's expanding blast wave. Such energetic particles can produce gamma rays and lower energy photons via interactions with the ambient plasma. The recently reported observation of TeV gamma rays from SN 1006 by the Collaboration of Australia and Nippon for a Gamma-Ray Observatory in the Outback (CANGAROO), combined with the fact that several unidentified EGRET sources have been associated with known radio/optical/X-ray-emitting remnants, provides powerful motivation for studying gamma-ray emission from SNRs. In this paper, we present results from a Monte Carlo simulation of nonlinear shock structure and acceleration coupled with photon emission in shelllike SNRs. These nonlinearities are a by-product of the dynamical influence of the accelerated cosmic rays on the shocked plasma and result in distributions of cosmic rays that deviate from pure power laws. Such deviations are crucial to acceleration efficiency considerations and impact photon intensities and spectral shapes at all energies, producing GeV/TeV intensity ratios that are quite different from test particle predictions. The Sedov scaling solution for SNR expansions is used to estimate important shock parameters for input into the Monte Carlo simulation. We calculate ion (proton and helium) and electron distributions that spawn neutral pion decay, bremsstrahlung, inverse Compton, and synchrotron emission, yielding complete photon spectra from radio frequencies to gamma-ray energies. The cessation of acceleration caused by the spatial and temporal limitations of the expanding SNR shell in moderately dense interstellar regions can yield spectral cutoffs in the TeV energy range that are consistent with Whipple's TeV upper limits on those EGRET unidentified sources that have SNR associations. Supernova remnants in lower density environments generate higher energy cosmic rays that produce predominantly inverse Compton emission observable at super-TeV energies, consistent with the SN 1006 detection. In general, sources in such low-density regions will be gamma-ray-dim at GeV energies. DA - 1999/3/1/ PY - 1999/3/1/ DO - 10.1086/306829 VL - 513 IS - 1 SP - 311-338 SN - 1538-4357 KW - acceleration of particles KW - cosmic rays KW - gamma rays : theory KW - ISM : individual (IC 443) KW - radiation mechanisms : nonthermal shock waves ER - TY - JOUR TI - Photoemission spectromicroscopy studies on epitaxial lateral overgrowth GaN surfaces AU - Yang, Y AU - Mishra, S AU - Cerrina, F AU - Xu, SH AU - Cruguel, H AU - Lapeyre, GJ AU - Schetzina, JF T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - Photoemission spectromicroscopy is employed to investigate the inhomogeneities of surface electronic structures of epitaxial lateral overgrowth GaN material. The image, acquired on a clean surface, shows the surface morphology and agrees with the atomic force microscopy image. The dominant contrast mechanism is attributed to the angular dependence of the quantum yield for regions at different angles. Energy distribution curves localized to a submicron region for the Ga 3d core level demonstrate that growth-front areas have different Fermi level pinning behavior compared with window areas and overgrowth regions. The sample exposed to atomic hydrogen shows the same Fermi level position for all areas of the surface. Photoemission spectromicroscopy reveals island formation when about 10 monolayers of Mg is deposited on the surface. DA - 1999/// PY - 1999/// DO - 10.1116/1.590840 VL - 17 IS - 4 SP - 1884-1890 SN - 1071-1023 ER - TY - JOUR TI - Monolayer-level controlled incorporation of nitrogen in ultrathin gate dielectrics using remote plasma processing: Formation of stacked 'N-O-N' gate dielectrics AU - Niimi, H. AU - Lucovsky, G. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 1999/// PY - 1999/// VL - 17 IS - 6 SP - 2610-2621 ER - TY - JOUR TI - Linear optical properties of a heavily Mg-doped Al0.09Ga0.91N epitaxial layer AU - Bergmann, MJ AU - Ozgur, U AU - Casey, HC AU - Muth, JF AU - Chang, YC AU - Kolbas, RM AU - Rao, RA AU - Eom, CB AU - Schurman, M T2 - APPLIED PHYSICS LETTERS AB - The room-temperature absorption coefficient and ordinary refractive index for a ∼0.4-μm-thick p-type wurtzite Al0.09Ga0.91N epitaxial layer were determined via optical transmission measurements. The layer was grown by metal organic chemical vapor deposition and heavily doped (∼5×1019 cm−3) with Mg. Additional measurements of the refractive index by prism coupling to the layer confirmed the transmission results. The low-temperature AlN buffer layer altered the expected interference fringes of the transmission spectrum below the band-gap energy and had to be accounted for in the analysis. The absorption coefficient exhibited band-tail effects and had a reduced slope near band-gap energy as compared to undoped GaN. Using a detailed balance argument, the reduced slope was consistent with the lack of a peak in the continuous-wave photoluminescent emission. DA - 1999/5/24/ PY - 1999/5/24/ DO - 10.1063/1.124102 VL - 74 IS - 21 SP - 3188-3190 SN - 0003-6951 ER - TY - JOUR TI - Light-front quark model analysis of exclusive 0(-) -> 0(-) semileptonic heavy meson decays AU - Choi, HM AU - Ji, CR T2 - PHYSICS LETTERS B AB - We present the analysis of exclusive $0^{-}$$\to$$0^{-}$ semileptonic heavy meson decays using the constituent quark model based on the light-front quantization. Our model is constrained by the variational principle for the well-known linear plus Coulomb interaction motivated by QCD. Our method of analytic continuation to obtain the weak form factors avoids the difficulty associated with the contribution from the nonvalence quark-antiquark pair creation. Our numerical results for the heavy-to-heavy and heavy-to-light meson decays are in a good agreement with the available experimental data and the lattice QCD results. In addition, our model predicts the two unmeasured mass spectra of $^{1}S_{0}(b\bar{b})$ and $^{3}S_{1}(b\bar{s})$ systems as $M_{b\bar{b}}$=9657 MeV and $M_{b\bar{s}}$= 5424 MeV. DA - 1999/8/12/ PY - 1999/8/12/ DO - 10.1016/S0370-2693(99)00817-5 VL - 460 IS - 3-4 SP - 461-466 SN - 1873-2445 KW - light-front quark model KW - semileptonic heavy meson decays KW - analytic continuation ER - TY - JOUR TI - Interfacial properties of ultrathin pure silicon nitride formed by remote plasma enhanced chemical vapor deposition AU - Misra, V. AU - Lazar, H. AU - Wang, Z. AU - Wu, Y. AU - Niimi, H. AU - Lucovsky, G. AU - Wortman, J. J. AU - Hauser, J. R. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 1999/// PY - 1999/// VL - 17 IS - 4 SP - 1836-1839 ER - TY - JOUR TI - GaP(001) and InP(001): Reflectance anisotropy and surface geometry AU - Esser, N AU - Schmidt, WG AU - Bernholc, J AU - Frisch, AM AU - Vogt, P AU - Zorn, M AU - Pristovsek, M AU - Richter, W AU - Bechstedt, F AU - Hannappel, T AU - Visbeck, S T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - We have investigated the optical anisotropy of GaP(001) and InP(001) surfaces. The samples were prepared by homoepitaxial metalorganic vapor phase epitaxy growth and either directly transferred into ultrahigh vacuum (UHV) or in situ capped and, after transfer, decapped in UHV by thermal desorption of a P/As capping layer. Symmetry, composition, and surface optical anisotropy were characterized by low-energy electron diffraction, Auger electron spectroscopy, and reflectance anisotropy spectroscopy. We observe (2×1)/(2×2)-like reconstructions for the very P-rich and (2×4) reconstructions for the more cation-rich surfaces. No (4×2) reconstruction could be prepared, independent of the preparation method. A comparison of the reflectance anisotropy between GaP(001) and InP(001) surfaces shows similar line shapes for the very cation-rich (2×4) surfaces. For less cation-rich surfaces, however, we observe distinct differences between the spectra of the two systems. In both cases, different line shapes in the reflection anisotropy spectra occur for the (2×4) periodicity, suggesting the existence of different (2×4) geometries. The experimental results are discussed on the background of atomic structures, total energies and reflectance anisotropy spectra obtained ab initio from density-functional theory local-density approximation calculations. DA - 1999/// PY - 1999/// DO - 10.1116/1.590810 VL - 17 IS - 4 SP - 1691-1696 SN - 1071-1023 ER - TY - JOUR TI - Excitonic structure and absorption coefficient measurements of ZnO single crystal epitaxial films deposited by pulsed laser deposition AU - Muth, JF AU - Kolbas, RM AU - Sharma, AK AU - Oktyabrsky, S AU - Narayan, J T2 - JOURNAL OF APPLIED PHYSICS AB - The optical properties of high quality single crystal epitaxial zinc oxide thin films grown by pulsed laser deposition on c-plane sapphire substrates were studied. It was found that annealing the films in oxygen dramatically improved the optical and electrical properties. The absorption coefficient, band gap, and exciton binding energies were determined by transmission measurements and photoluminescence. In both the annealed and the as-deposited films excitonic absorption features were observed at both room temperature and 77 K. In the annealed films the excitonic absorption peaks were substantially sharper and deep level photoluminescence was suppressed. DA - 1999/6/1/ PY - 1999/6/1/ DO - 10.1063/1.370601 VL - 85 IS - 11 SP - 7884-7887 SN - 1089-7550 ER - TY - JOUR TI - Estimation of uncertainties in XAFS data AU - Newville, M AU - Boyanov, BI AU - Sayers, DE T2 - JOURNAL OF SYNCHROTRON RADIATION DA - 1999/5/1/ PY - 1999/5/1/ DO - 10.1107/S0909049598018147 VL - 6 SP - 264-265 SN - 0909-0495 KW - XAFS analysis KW - error analysis KW - Fourier transform ER - TY - JOUR TI - Computational materials science: The era of applied quantum mechanics AU - Bernholc, J T2 - PHYSICS TODAY AB - For many centuries, materials were discovered, mined, and processed in a largely serendipitous way. However, the characterization of the atom and the progress made in x-ray diffraction during the early years of this century started a quest for a theory of materials in terms of their atomic constituents. Later decades saw scientists developing many qualitative and semi-quantitative models that explained the principles of atomic cohesion and the basic properties of semiconductors, metals, and salts. Considering their simplicity, some of the models were surprisingly accurate and led to remarkable progress. However, for most materials of current interest, the interatomic interactions are intricate enough to require fairly elaborate models. Fortunately, we are entering an era in which high-performance computing is coming into its own, allowing true predictive simulations of complex materials to be made from information on their individual atoms. DA - 1999/9// PY - 1999/9// DO - 10.1063/1.882840 VL - 52 IS - 9 SP - 30-35 SN - 1945-0699 ER - TY - JOUR TI - Charge redistribution at GaN-Ga2O3 interfaces: A microscopic mechanism for low defect density interfaces in remote plasma processed MOS devices prepared on polar GaN faces AU - Therrien, R AU - Niimi, H AU - Gehrke, T AU - Lucovsky, G AU - Davis, R T2 - MICROELECTRONIC ENGINEERING AB - Abstract Interfacial defect densities are typically two orders of magnitude higher at [III–V]-dielectric interfaces than at SiSiO 2 interfaces. This paper demonstrates GaN devices with significantly reduced interfacial defect densities using a two step remote plasma process to form the GaN-dielectric interface and then deposit the dielectric film. Separate plasma oxidation and deposition steps have previously been used for fabrication of aggressively scaled Si devices. Essentially the same 300°C remote plasma processing has been applied to GaN metal-oxide semiconductor (MOS) capacitors and field effect transistors (FETs). This paper i) discusses the low temperature plasma process for GaN device fabrication, ii) briefly reviews GaN device performance, and then iii) presents a chemical bonding model that provides a basis for the improved interface electrical properties. DA - 1999/9// PY - 1999/9// DO - 10.1016/s0167-9317(99)00394-9 VL - 48 IS - 1-4 SP - 303-306 SN - 0167-9317 ER - TY - JOUR TI - Bonding constraint-induced defect formation at Si-dielectric interfaces and internal interfaces in dual-layer gate dielectrics AU - Lucovsky, G. AU - Wu, Y. AU - Niimi, H. AU - Misra, V. AU - Phillips, J. C. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 1999/// PY - 1999/// VL - 17 IS - 4 SP - 1806-1812 ER - TY - JOUR TI - Bioturbation and particle transport in Carolina slope sediments: A radiochemical approach AU - Fornes, WL AU - DeMaster, DJ AU - Levin, LA AU - Blair, NE T2 - JOURNAL OF MARINE RESEARCH AB - In situ tracer experiments investigated short-term sediment mixing processes at two Carolina continental margin sites (water depth = 850 m) characterized by different organic C fluxes, 234 Th mixing coefficients (D b ) and benthic assemblages. Phytoplankton, slope sediment, and sand-sized glass beads tagged with 210 Pb, 113 Sn, and 228 Th, respectively, were placed via submersible at the sediment-water interface at both field sites (Site I off Cape Fear, and Site III off Cape Hatteras). Experimental plots were sampled at 0, 1.5 days, and 90 days after tracer emplacement to examine short-term, vertical transport. Both sites are initially dominated by nonlocal mixing. Transport to the bottom of the surface mixed layer at both sites occurs more rapidly than 234 Th-based D b values predict; after 1.5 days, tagged particles were observed 5 cm below the sediment-water interface at Site I and 12 cm below at Site III. Impulse tracer profiles after 90 days at Site III exhibit primarily diffusive distributions, most likely due to a large number of random, nonlocal mixing events. The D b values determined from 90-day particle tagging experiments are comparable to those obtained from naturally occurring 234 Th profiles (∼100-day time scales) from nearby locations. The agreement between impulse tracer mixing coefficients and steady-state natural tracer mixing coefficients suggests that the diffusive analogue for bioturbation on monthly time scales is a realistic and useful approach. Tracer profiles from both sites exhibit some degree of particle selective mixing, but the preferential transport of the more labile carbon containing particles only occurred 30% of the time. Consequently, variations in the extent to which age-dependent mixing occurs in marine sediments may depend on factors such as faunal assemblage and organic carbon flux. DA - 1999/3// PY - 1999/3// DO - 10.1357/002224099321618245 VL - 57 IS - 2 SP - 335-355 SN - 1543-9542 ER - TY - JOUR TI - Scanning electron microscopy and cathodoluminescence study of the epitaxial lateral overgrowth (ELO) process for gallium nitride AU - Johnson, MAL AU - Yu, ZH AU - Brown, JD AU - El-Masry, NA AU - Cook, JW AU - Schetzina, JF T2 - JOURNAL OF ELECTRONIC MATERIALS DA - 1999/3// PY - 1999/3// DO - 10.1007/s11664-999-0030-1 VL - 28 IS - 3 SP - 295-300 SN - 0361-5235 KW - cathodoluminescence (CL) KW - epitaxial lateral overgrowth (ELO) KW - GaN KW - metalorganic vapor phase epitaxy (MOVPE) ER - TY - JOUR TI - Renormalized effective QCD Hamiltonian: Gluonic sector AU - Robertson, DG AU - Swanson, ES AU - Szczepaniak, AP AU - Ji, CR AU - Cotanch, , SR T2 - PHYSICAL REVIEW D AB - Extending previous QCD Hamiltonian studies, we present a new renormalization procedure which generates an effective Hamiltonian for the gluon sector. The formulation is in the Coulomb gauge where the QCD Hamiltonian is renormalizable and the Gribov problem can be resolved. We utilize elements of the G\l{}azek and Wilson regularization method but now introduce a continuous cut-off procedure which eliminates non-local counterterms. The effective Hamiltonian is then derived to second order in the strong coupling constant. The resulting renormalized Hamiltonian provides a realistic starting point for approximate many-body calculations of hadronic properties for systems with explicit gluon degrees of freedom. DA - 1999/4/1/ PY - 1999/4/1/ DO - 10.1103/physrevd.59.074019 VL - 59 IS - 7 SP - SN - 2470-0029 ER - TY - JOUR TI - Optical and structural studies of Ge nanocrystals embedded in AlN matrix fabricated by pulsed laser deposition AU - Hassan, KM AU - Sharma, AK AU - Narayan, J AU - Muth, JF AU - Teng, CW AU - Kolbas, RM T2 - APPLIED PHYSICS LETTERS AB - Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation K. M. Hassan, A. K. Sharma, J. Narayan, J. F. Muth, C. W. Teng, R. M. Kolbas; Optical and structural studies of Ge nanocrystals embedded in AlN matrix fabricated by pulsed laser deposition. Appl. Phys. Lett. 30 August 1999; 75 (9): 1222–1224. https://doi.org/10.1063/1.124648 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioApplied Physics Letters Search Advanced Search |Citation Search DA - 1999/8/30/ PY - 1999/8/30/ DO - 10.1063/1.124648 VL - 75 IS - 9 SP - 1222-1224 SN - 1077-3118 ER - TY - JOUR TI - Neutron resonance spectroscopy of Sn-117 from 1 eV to 1.5 keV AU - Smith, DA AU - Bowman, JD AU - Crawford, BE AU - Grossmann, CA AU - Haseyama, T AU - Johnson, MB AU - Masaike, A AU - Matsuda, Y AU - Mitchell, GE AU - Nazarenko, VA AU - Penttila, SI AU - Roberson, NR AU - Seestrom, SJ AU - Sharapov, EI AU - Smotritsky, LM AU - Stephenson, SL AU - Yuan, V T2 - PHYSICAL REVIEW C AB - Parity violation has been studied recently for neutron resonances in ${}^{117}\mathrm{Sn}.$ The neutron resonance spectroscopy is essential for the analysis of the parity violation data. We have measured neutron resonances in ${}^{117}\mathrm{Sn}$ for neutron energies from 1 to 1500 eV using the time-of-flight method and the $(n,\ensuremath{\gamma})$ reaction. The sample was enriched to 87.6% ${}^{117}\mathrm{Sn}.$ Neutron scattering and radiative widths were determined, and orbital angular momentum assignments were made with a Bayesian analysis. The s-wave and p-wave strength functions and average level spacings were determined. DA - 1999/5// PY - 1999/5// DO - 10.1103/physrevc.59.2836 VL - 59 IS - 5 SP - 2836-2843 SN - 1089-490X ER - TY - JOUR TI - Near-edge X-ray absorption fine structure spectroscopy of MDI and TDI polyurethane polymers AU - Urquhart, SG AU - Smith, AP AU - Ade, HW AU - Hitchcock, AP AU - Rightor, EG AU - Lidy, W T2 - JOURNAL OF PHYSICAL CHEMISTRY B AB - The sensitivity of near-edge X-ray absorption fine structure (NEXAFS) to differences in key chemical components of polyurethane polymers is presented. Carbon 1s NEXAFS spectra of polyurethane polymers made from 4,4‘-methylene di-p-phenylene isocyanate (MDI) and toluene diisocyanate (TDI) isocyanate monomers illustrate that there is an unambiguous spectroscopic fingerprint for distinguishing between MDI-based and TDI-based polyurethane polymers. NEXAFS spectra of MDI and TDI polyurea and polyurethane models show that the urea and carbamate (urethane) linkages in these polymers can be distinguished. The NEXAFS spectroscopy of the polyether component of these polymers is discussed, and the differences between the spectra of MDI and TDI polyurethanes synthesized with polyether polyols of different molecular composition and different molecular weight are presented. These polymer spectra reported herein provide appropriate model spectra to represent the pure components for quantitative microanalysis. DA - 1999/6/3/ PY - 1999/6/3/ DO - 10.1021/jp990059w VL - 103 IS - 22 SP - 4603-4610 SN - 1089-5647 ER - TY - JOUR TI - Mixing angles and electromagnetic properties of ground state pseudoscalar and vector meson nonets in the light-cone quark model - art. no. 074015 AU - Choi, H. M. AU - Ji, C. R. T2 - Physical Review. D, Particles and Fields DA - 1999/// PY - 1999/// VL - 5907 IS - 7 SP - 4015 ER - TY - JOUR TI - Large-scale simulations of phase separation of elastically coherent binary alloy systems AU - Orlikowski, D AU - Sagui, C AU - Somoza, A AU - Roland, C T2 - PHYSICAL REVIEW B AB - The effects of long-range elastic fields on the phase separation process of both two- and three-dimensional binary alloy systems was investigated with large-scale Langevin simulations. The elastic effects incorporated in the model are the result of anisotropy and dilational misfits introduced via inhomogeneities in the elastic constants of the constituents. The domain morphology obtained is readily understandable in terms of selection criteria for the shape and/or orientation of the domains based on the different shear moduli that are present in the system. Furthermore, the coarsening behavior of the domains is discussed in terms of the generated chemical potential barriers surrounding the precipitates. Other aspects of the coarsening process such as dynamic scaling of the correlation functions and local inverse coarsening are also discussed. DA - 1999/4/1/ PY - 1999/4/1/ DO - 10.1103/physrevb.59.8646 VL - 59 IS - 13 SP - 8646-8659 SN - 2469-9969 ER - TY - JOUR TI - Investigation of thickness effects on AlN coated metal tips by in situ I-V measurement AU - Kang, DH AU - Zhirnov, , VV AU - Wojak, GJ AU - Preble, EA AU - Choi, WB AU - Hren, JJ AU - Cuomo, JJ T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - The effects of the aluminum nitride coating thickness on molybdenum emitter tips were investigated by an in situ I–V measurement technique inside a typical magnetron sputtering system. AlN was deposited on Mo tips using a dc-modulated 1 kW power source at 200 °C. Each I/V measurement was carried out immediately following a 15 s AlN deposition. Significantly improved field emission was observed as well as a strong emission thickness dependence, which we attribute to the influence of space charge. DA - 1999/// PY - 1999/// DO - 10.1116/1.590608 VL - 17 IS - 2 SP - 632-634 SN - 1071-1023 ER - TY - JOUR TI - Imaging electron emission from diamond and III-V nitride surfaces with photo-electron emission microscopy AU - Nemanich, RJ AU - English, SL AU - Hartman, JD AU - Sowers, AT AU - Ward, BL AU - Ade, H AU - Davis, RF T2 - APPLIED SURFACE SCIENCE AB - Wide bandgap semiconductors such as diamond and the III–V nitrides (GaN, AlN, and AlGaN alloys) exhibit small or even negative electron affinities. Results have shown that different surface treatments will modify the electron affinity of diamond to cause a positive or negative electron affinity (NEA). This study describes the characterization of these surfaces with photo-electron emission microscopy (PEEM). The PEEM technique is unique in that it combines aspects of UV photoemission and field emission. In this study, PEEM images are obtained with either a traditional Hg lamp or with tunable UV excitation from a free electron laser. The UV-free electron laser at Duke University provides tunable emission from 3.5 to greater than 7 eV. PEEM images of boron or nitrogen (N)-doped diamond are similar to SEM of the same surface indicating relatively uniform emission. For the N-doped samples, PEEM images were obtained for different photon energies ranging from 5.0 to 6.0 eV. In these experiments, the hydrogen terminated surface showed more intense PEEM images at lower photon energy indicating a lower photothreshold than annealed surfaces which are presumed to be adsorbate free. For the nitrides, the emission properties of an array of GaN emitter structures is imaged. Emission is observed from the peaks, and relatively uniform emission is observed from the array. The field at the sample surface is approximately 10 V/μm which is sufficient to obtain an image without UV light. This process is termed field emission electron microscopy (FEEM). DA - 1999/5// PY - 1999/5// DO - 10.1016/S0169-4332(99)00021-5 VL - 146 IS - 1-4 SP - 287-294 SN - 0169-4332 KW - diamond KW - photo-electron emission microscopy KW - field emission electron microscopy ER - TY - JOUR TI - Hydrogen plasma removal of post-RIE residue for backend processing AU - Somashekhar, A AU - Ying, H AU - Smith, PB AU - Aldrich, DB AU - Nemanich, RJ T2 - JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB - Reactive ion etching of a patterned silicon dioxide layer leaves behind a uniform fluorocarbon layer which must subsequently be removed. Both surface and via polymeric residues form during the reactive ion etch step and their removal using ‐based plasma clean processes is reported here. X‐ray photoelectron spectroscopy was used to determine the composition of the residue. Scanning electron microscope images were taken before and after the dry clean treatment to determine the effectiveness of the residue removal process. A radio‐frequency‐generated hydrogen plasma was used in the dry clean experiments. Power, temperature, and pressure were varied while gas flow was kept constant at 75 sccm and the process time was 5–10 min. The surface residue (on the oxide) was most efficiently removed at 400 W, 450°C, and 15 mTorr when exposed to the plasma for 10 min. The in‐via residue was best removed following a 5 min plasma exposure at 100 W, 450°C and 15 mTorr. © 1999 The Electrochemical Society. All rights reserved. DA - 1999/6// PY - 1999/6// DO - 10.1149/1.1391933 VL - 146 IS - 6 SP - 2318-2321 SN - 0013-4651 ER - TY - JOUR TI - Epitaxial lateral overgrowth of GaN on SiC and sapphire substrates AU - Yu, Z. H. AU - Johnson, M. A. L. AU - Brown, J. D. AU - El-Masry, N. A. AU - Muth, J. F. AU - Cook, J. W. AU - Schetzina, J. F. AU - Haberern, K. W. AU - Kong, H. S. AU - Edmond, J. S. T2 - MRS Internet Journal of Nitride Semiconductor Research AB - The epitaxial lateral overgrowth (ELO) process for GaN has been studied using SiC and sapphire substrates. Both MBE and MOVPE growth processes were employed in the study. The use of SiO 2 versus SiN x insulator stripes was investigated using window/stripe widths ranging from 20 μm/4 μm to 3 μm/15 μm. GaN film depositions were completed at temperatures ranging from 800 °C to 1120 °C. Characterization experiments included RHEED, TEM, SEM and cathodolumenescence studies. The MBE growth experiments produced polycrystalline GaN over the insulator stripes even at deposition temperatures as high as 990 °C. In contrast, MOVPE growth produced single-crystal GaN stripes with no observable threading dislocations. DA - 1999/// PY - 1999/// DO - 10.1557/s1092578300002878 VL - 4S1 IS - G4.3 ER - TY - JOUR TI - Effect of nitrogen incorporation on electron emission from chemical vapor deposited diamond AU - Park, M AU - Sowers, AT AU - Rinne, CL AU - Schlesser, R AU - Bergman, L AU - Nemanich, RJ AU - Sitar, Z AU - Hren, JJ AU - Cuomo, JJ AU - Zhirnov, , VV AU - Choi, WB T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - Two different types of the nitrogen-doped chemical vapor deposited (CVD) diamond films were synthesized with N2 (nitrogen) and C3H6N6 (melamine) as doping sources. The samples were analyzed by scanning electron microscopy, Raman scattering, photoluminescence spectroscopy, and field-emission measurements. More effective substitutional nitrogen doping was achieved with C3H6N6 than with N2. The diamond film doped with N2 contained a significant amount of nondiamond carbon phases. The sample produced with N2 exhibited a lower field emission turn-on field than the sample produced with C3H6N6. It is believed that the presence of the graphitic phases (or amorphous sp2 carbon) at the grain boundaries of the diamond and/or the nanocrystallinity (or microcrystallinity) of the diamond play a significant role in lowering the turn-on field of the film produced using N2. It is speculated that substitutional nitrogen doping plays only a minor role in changing the field emission characteristics of CVD diamond films. DA - 1999/// PY - 1999/// DO - 10.1116/1.590630 VL - 17 IS - 2 SP - 734-739 SN - 2166-2746 ER - TY - JOUR TI - Absorption coefficient and refractive index of GaN, AlN and AlGaN alloys AU - Muth, J. F. AU - Brown, J. D. AU - Johnson, M. A. L. AU - Yu, Z. H. AU - Kolbas, R. M. AU - Cook, J. W. AU - Schetzina, J. F. T2 - MRS Internet Journal of Nitride Semiconductor Research DA - 1999/// PY - 1999/// VL - 4S1 IS - G5.2 ER - TY - JOUR TI - A critical comparison between MOVPE and MBE growth of III-V nitride semiconductor materials for opto-electronic device applications AU - Johnson, M. A. L. AU - Yu, Z. H. AU - Brown, J. D. AU - Koeck, F. A. AU - El-Masry, N. A. AU - Kong, H. S. AU - Edmond, J. A. AU - Cook, J. W. AU - Schetzina, J. F. T2 - MRS Internet Journal of Nitride Semiconductor Research AB - A systematic study of the growth and doping of GaN, AlGaN, and InGaN by both molecular beam epitaxy (MBE) and metal-organic vapor phase epitaxy (MOVPE) has been performed. Critical differences between the resulting epitaxy are observed in the p-type doping using magnesium as the acceptor species. MBE growth, using rf-plasma sources to generate the active nitrogen species for growth, has been used for III-Nitride compounds doped either n-type with silicon or p-type with magnesium. Blue and violet light emitting diode (LED) test structures were fabricated. These vertical devices required a relatively high forward current and exhibited high leakage currents. This behavior was attributed to parallel shorting mechanisms along the dislocations in MBE grown layers. For comparison, similar devices were fabricated using a single wafer vertical flow MOVPE reactor and ammonia as the active nitrogen species. MOVPE grown blue LEDs exhibited excellent forward device characteristics and a high reverse breakdown voltage. We feel that the excess hydrogen, which is present on the GaN surface due to the dissociation of ammonia in MOVPE, acts to passivate the dislocations and eliminate parallel shorting for vertical device structures. These findings support the widespread acceptance of MOVPE, rather than MBE, as the epitaxial growth technique of choice for III-V nitride materials used in vertical transport bipolar devices for optoelectronic applications. DA - 1999/// PY - 1999/// DO - 10.1557/s1092578300003100 VL - 4S1 IS - G5.10 ER - TY - JOUR TI - Surface sensitivity of impurity incorporation: Mg at GaN (0001) surfaces AU - Bungaro, C AU - Rapcewicz, K AU - Bernholc, J T2 - PHYSICAL REVIEW B AB - The interplay of surface termination, reconstruction patterns, and availability of species involved determines the incorporation of impurities during growth. We study ab initio this interplay for Mg at the GaN (0001) surfaces and find that optimal incorporation conditions strongly depend upon surface orientation and cannot be predicted using bulk stoichiometric arguments. With reasonable assumptions on the kinetics, high densities of Mg can be achieved in the absence of hydrogen and the Ga surface displays superior incorporation characteristics to that of the N surface. DA - 1999/4/15/ PY - 1999/4/15/ DO - 10.1103/physrevb.59.9771 VL - 59 IS - 15 SP - 9771-9774 SN - 2469-9969 ER - TY - JOUR TI - Phonon dynamics and lifetimes of AlN and GaN crystallites AU - Bergman, L. AU - Alexson, D. AU - Nemanich, R. J. AU - Dutta, M. AU - Stroscio, M. A. AU - Balkas, C. AU - Davis, R. F. T2 - MRS Internet Journal of Nitride Semiconductor Research AB - The quasi-LO and quasi-TO modes of AlN crystallite were investigated. The analysis indicates that the Raman mode behavior concurs with Loudons’ model of mode-mixing in wurtzite (WZ) structure crystals which is due to the long-range electrostatic field. Phononlifetimes of GaN and AlN crystallites were studied via Raman lineshape. It was found that the low energy E2 mode lifetime is about an order of magnitude longer than that of the other modes, and that impurities impact significantly the phonon-lifetimes. DA - 1999/// PY - 1999/// DO - 10.1557/s1092578300003422 VL - 4S1 IS - G6.65 ER - TY - JOUR TI - Parity violation in neutron resonances in Ag-107,Ag-109 AU - Lowie, L. Y. AU - Bowman, J. D. AU - Corvi, F. AU - Crawford, B. E. AU - Delheij, P. P. J. AU - Frankle, C. M. AU - Iinuma, M. AU - Knudson, J. N. AU - Masaike, A. AU - Masuda, Y. AU - Matsuda, Y. AU - Mitchell, G. E. AU - Penttila, S. I. AU - Postma, H. AU - Roberson, N. R. AU - Seestrom, S. J. AU - al., T2 - Physical Review. C, Nuclear Physics AB - Parity nonconservation (PNC) was studied in p-wave resonances in Ag by measuring the helicity dependence of the neutron total cross section. Transmission measurements on natural Ag were performed in the energy range 32 to 422 eV with the time-of-flight method at the Manuel Lujan Neutron Scattering Center at Los Alamos National Laboratory. A total of 15 p-wave neutron resonances were studied in ${}^{107}\mathrm{Ag}$ and nine p-wave resonances in ${}^{109}\mathrm{Ag}.$ Statistically significant asymmetries were observed for eight resonances in ${}^{107}\mathrm{Ag}$ and for four resonances in ${}^{109}\mathrm{Ag}.$ An analysis treating the PNC matrix elements as random variables yields a weak spreading width of ${\ensuremath{\Gamma}}_{w}{=(2.67}_{\ensuremath{-}1.21}^{+2.65})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7} \mathrm{eV}$ for ${}^{107}\mathrm{Ag}$ and ${\ensuremath{\Gamma}}_{w}{=(1.30}_{\ensuremath{-}0.74}^{+2.49})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7} \mathrm{eV}$ for ${}^{109}\mathrm{Ag}.$ DA - 1999/// PY - 1999/// DO - 10.1103/physrevc.59.1119 VL - 59 IS - 2 SP - 1119-1130 ER - TY - JOUR TI - Near-edge X-ray absorption fine structure spectroscopy on ordered films of an amphiphilic derivate of 2,5-diphenyl-1,3,4-oxadiazole AU - Giebler, R AU - Schulz, B AU - Reiche, J AU - Brehmer, L AU - Wuhn, M AU - Woll, C AU - Smith, AP AU - Urquhart, SG AU - Ade, HW AU - Unger, WES T2 - LANGMUIR AB - The surfaces of ordered films formed from an amphiphilic derivative of 2,5-diphenyl-1,3,4-oxadiazole by the Langmuir−Blodgett (LB) technique and organic molecular beam deposition (OMBD) were investigated by the use of near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. For the assignment of the spectral features of the C, N, and O K-edge absorption spectra, fingerprint spectra of poly(p-phenylene terephthalamide) (Kevlar), poly(ethylene terephthalate), poly(p-phenylene-1,3,4-oxadiazole), and 2,5-di(pentadecyl)-1,3,4-oxadiazole, which contain related chemical moieties, were recorded. Ab initio molecular orbital calculations, performed with explicit treatment of the core hole, are used to support the spectral interpretations. Angle-resolved NEXAFS spectroscopy at the C, N, and O K-edges suggests a preferentially upright orientation of the oxadiazole derivative in the outermost layer of the films. X-ray specular reflectivity data and molecular modeling results suggest a similar interpretation. DA - 1999/2/16/ PY - 1999/2/16/ DO - 10.1021/la980888t VL - 15 IS - 4 SP - 1291-1298 SN - 0743-7463 ER - TY - JOUR TI - Kaon electroweak form factors in the light-front quark model - art. no. 034001 AU - Choi, H. M. AU - Ji, C. R. T2 - Physical Review. D, Particles and Fields DA - 1999/// PY - 1999/// VL - 5903 IS - 3 SP - 4001- ER - TY - JOUR TI - Hybrid meson decay phenomenology - art. no. 034016 AU - Page, P. R. AU - Swanson, E. S. AU - Szczepaniak, A. P. T2 - Physical Review. D, Particles and Fields DA - 1999/// PY - 1999/// VL - 5903 IS - 3 SP - 4016 ER - TY - JOUR TI - Conformal "thin-sandwich" data for the initial-value problem of general relativity AU - York, JW T2 - PHYSICAL REVIEW LETTERS AB - The initial-value problem is posed by giving a conformal three-metric on each of two nearby spacelike hypersurfaces, the proper-time separation of the hypersurfaces up to a multiplier to be determined, and the mean (extrinsic) curvature of one slice. The resulting equations have the same elliptic form as in the one-hypersurface formulation. The metrical roots of this form are revealed by a conformal ``thin sandwich'' viewpoint coupled with the transformation properties of the lapse function. DA - 1999/2/15/ PY - 1999/2/15/ DO - 10.1103/PhysRevLett.82.1350 VL - 82 IS - 7 SP - 1350-1353 SN - 0031-9007 ER - TY - JOUR TI - Computing carrier interactions with confined and excluded phonons in nanostructures of complex geometries AU - Kiselev, AA AU - Kim, KW AU - Stroscio, MA T2 - PHYSICAL REVIEW B AB - We provide a simple and highly effective procedure for calculating quantities such as electron scattering rates involving confined and excluded phonons for quantum wires of arbitrary geometry. This problem is particularly difficult to solve by the usual summation procedure as well as by alternative treatments proposed thus far. To demonstrate the strength of our approach, we produce exact analytical results in the case of a quantum well. As a numerical example, we consider a classic T-shaped structure with different sizes and radii of curvature at the intersections. We examine the possibility of manipulating structural characteristics such as electron-phonon scattering rates by making minor modifications to the quantum wire cross-sectional geometries. DA - 1999/4/15/ PY - 1999/4/15/ DO - 10.1103/physrevb.59.10212 VL - 59 IS - 15 SP - 10212-10216 SN - 1550-235X ER - TY - JOUR TI - Case study of the physics component of an integrated curriculum AU - Beichner, R AU - Bernold, L AU - Burniston, E AU - Dail, P AU - Felder, R AU - Gastineau, J AU - Gjertsen, M AU - Risley, J T2 - AMERICAN JOURNAL OF PHYSICS AB - Over a four-year time span, several departments at North Carolina State University offered experimental sections of courses taken by freshman engineering students. The acronym IMPEC (Integrated Math, Physics, Engineering, and Chemistry curriculum) describes which classes were involved. This paper discusses the physics component of the curriculum and describes the impact of the highly collaborative, technology-rich, activity-based learning environment on a variety of conceptual and problem-solving assessments and attitude measures. Qualitative and quantitative research results indicate that students in the experimental courses outperformed their cohorts in demographically matched traditional classes, often by a wide margin. Student satisfaction and confidence rates were remarkably high. We also noted substantial increases in retention and success rates for groups underrepresented in science, math, and engineering. Placing students in the same teams across multiple courses appears to have been the most beneficial aspect of the learning environment. DA - 1999/7// PY - 1999/7// DO - 10.1119/1.19075 VL - 67 IS - 7 SP - S16-S24 SN - 0002-9505 ER - TY - JOUR TI - Structural fingerprints in the reflectance anisotropy spectra of InP(001)(2x4) surfaces AU - Schmidt, WG AU - Briggs, EL AU - Bernholc, J AU - Bechstedt, F T2 - PHYSICAL REVIEW B AB - The reflectance anisotropy has been calculated from first principles for a series of recently proposed structural models of the $\mathrm{InP}(001)(2\ifmmode\times\else\texttimes\fi{}4)$ surface. The features of the calculated spectra are related to specific surface bonding configurations. We find a pronounced negative anisotropy around 1.7 eV linked to transitions between \ensuremath{\sigma}-like In-In bonding states and empty dangling bonds localized at the surface cations. The strength of that anisotropy is directly related to the number of In-In bonds at the surface. This explains the gradual change of the corresponding measured anisotropy in that energy region, depending on the growth conditions. Positive anisotropies at higher energies arise from transitions between P-P dimer related states and surface resonances. Additionally we find derivativelike features at the energy of the ${E}_{1}$ peak that depend only weakly on the surface structure and stoichiometry. In conjunction with the experimental data, our results indicate that the (2\ifmmode\times\else\texttimes\fi{}4) reconstructed InP(001) surface features In-In bonds along [110] and P-P dimers parallel to $[11\ifmmode\bar\else\textasciimacron\fi{}0],$ respectively. The relative number of these bonds varies with the growth conditions. DA - 1999/1/15/ PY - 1999/1/15/ DO - 10.1103/physrevb.59.2234 VL - 59 IS - 3 SP - 2234-2239 SN - 1550-235X ER - TY - JOUR TI - Segregation effects at vacancies in AlxGa1-xN and SixGe1-x alloys AU - Boguslawski, P AU - Bernholc, J T2 - PHYSICAL REVIEW B AB - It is shown by quantum molecular-dynamics calculations that the formation energies of vacancies in semiconductor alloys strongly depend on the chemical identities of their nearest-neighbor atoms. For example, in ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{N}$ alloys the Ga-terminated vacancy is lower in energy than the Al-terminated one by 2.8 eV, while the corresponding difference in ${\mathrm{Si}}_{x}{\mathrm{Ge}}_{1\ensuremath{-}x}$ is 1 eV. This leads to unexpectedly strong preferences for vacancy termination in semiconductor alloys. The results also predict that local segregation will occur at grain boundaries and dislocations. DA - 1999/1/15/ PY - 1999/1/15/ DO - 10.1103/physrevb.59.1567 VL - 59 IS - 3 SP - 1567-1570 SN - 1550-235X ER - TY - JOUR TI - Search for parity violation in Nb-93 neutron resonances AU - Sharapov, EI AU - Bowman, JD AU - Crawford, BE AU - Delheij, PPJ AU - Frankle, CM AU - Fukuda, K AU - Iinuma, M AU - Knudson, JN AU - Lokitz, SJ AU - Lowie, LY AU - Masaike, A AU - Masuda, Y AU - Matsuda, Y AU - Mitchell, GE AU - Penttila, SI AU - Postma, H AU - Roberson, NR AU - Seestrom, SJ AU - Shimizu, HM AU - Stephenson, SL AU - Yen, YF AU - Yuan, VW T2 - PHYSICAL REVIEW C AB - A new search has been performed for parity violation in the compound nuclear states of ${}^{94}\mathrm{Nb}$ by measuring the helicity dependence of the neutron total cross section. Transmission measurements on a thick niobium target were performed by the time-of-flight method at the Manuel Lujan Neutron Scattering Center with a longitudinally polarized neutron beam in the energy range 32 to 1000 eV. A total of 18 p-wave resonances in ${}^{93}\mathrm{Nb}$ were studied with none exhibiting a statistically significant parity-violating longitudinal asymmetry. An upper limit of $1.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$ eV (95% confidence level) was obtained for the weak spreading width ${\ensuremath{\Gamma}}_{w}$ in ${}^{93}\mathrm{Nb}.$ DA - 1999/2// PY - 1999/2// DO - 10.1103/physrevc.59.1131 VL - 59 IS - 2 SP - 1131-1135 SN - 1089-490X ER - TY - JOUR TI - Safety and efficacy of the Environmental Products Group Masterflow Aquarium Management System with Aegis Microbe Shield (TM) AU - Lewbart, GA AU - Stoskopf, MK AU - Losordo, T AU - Geyer, J AU - Owen, J AU - Smith, DW AU - Law, M AU - Altier, C T2 - AQUACULTURAL ENGINEERING AB - This study investigated the safety and efficacy of the EPG Masterflow Aquarium Management System with Aegis Microbe Shield™ (EPG-MAMS). Four different species of fish were used in the study. Ten fish of each species were placed in 75 l aquariums containing the EPG filter media, a commercially available filter media (Whisper®) and an aquarium with no filter material. At the end of the 45 day trial three fish from each tank were sacrificed and preserved in formalin for histopathology. Water quality parameters were routinely monitored. The EPG filter media was compared with the Whisper® filter media for efficacy against Aeromonas salmonicida using a shaker flask microbiological assay. The EPG filter proved to be clinically and histopathologically safe and reduced to some degree the number of A. salmonicida suspended in water in an in vitro study. DA - 1999/1// PY - 1999/1// DO - 10.1016/S0144-8609(98)00043-0 VL - 19 IS - 2 SP - 93-98 SN - 0144-8609 KW - Environmental Products Group KW - Masterflow Aquarium Management System KW - Aegis Microbe Shield ER - TY - JOUR TI - Extraction of bounds on time-reversal non-invariance from neutron reactions AU - Davis, E.D. AU - Gould, C.R. T2 - Physics Letters B AB - Ratios involving on-resonance measurements of the three-fold and five-fold correlation cross sections for which the dependence on some of the unknown spectroscopic data is eliminated are considered. Closed form expressions are derived for the statistical distributions of these ratios. Implications for bounds on the variance of matrix elements of time reversal non-invariant nucleon-nucleon interactions are considered within a Bayesian framework and the competitiveness with bounds from other experiments is evaluated. The prospects for null five-fold correlation measurements improving by an order of magnitude or more upon the current bound on a parity-conserving T-odd interaction are good. DA - 1999/2// PY - 1999/2// DO - 10.1016/S0370-2693(99)00013-1 VL - 447 IS - 3-4 SP - 209-215 J2 - Physics Letters B LA - en OP - SN - 0370-2693 UR - http://dx.doi.org/10.1016/s0370-2693(99)00013-1 DB - Crossref ER - TY - JOUR TI - Dispersion of polar optical phonons in wurtzite quantum wells AU - Komirenko, SM AU - Kim, KW AU - Stroscio, MA AU - Dutta, M T2 - PHYSICAL REVIEW B AB - Dispersion relations for polar optical phonon modes in wurtzite quantum wells (QW's) are obtained in the framework of the dielectric continuum model. It is found that anisotropy of the dielectric medium causes a number of qualitative peculiarities in the phonon spectra. Among these are the absence of the proper confinement for the oscillatory waves located in the QW, inversion of the order of symmetric and antisymmetric quasiconfined optical modes, formation of the finite energy intervals where such confined modes---which are found to be dispersive---can exist, penetration of the half-space phonons into the QW, etc. Some additional peculiarities, such as appearance of propagating modes, strong dispersion of long-wavelength half-space modes, and reduction of the number of interface modes, arise as a result of overlapping characteristic phonon frequencies of the surrounding material and the material of QW. Predicted phonon behavior leads to the conclusion that dependence of dielectric properties of ternary-binary low-dimensional wurtzite heterostructures on composition can serve as a powerful tool for the purposes of phonon spectrum engineering. In order to illustrate these results, the optical phonon spectra are calculated for an ${\mathrm{Al}}_{0.15}{\mathrm{Ga}}_{0.85}\mathrm{N}/\mathrm{GaN}/{\mathrm{Al}}_{0.15}{\mathrm{Ga}}_{0.85}\mathrm{N} \mathrm{QW},$ an $\mathrm{AlN}/\mathrm{GaN}/\mathrm{AlN} \mathrm{QW},$ and for a $\mathrm{GaN}$ dielectric slab. DA - 1999/2/15/ PY - 1999/2/15/ DO - 10.1103/physrevb.59.5013 VL - 59 IS - 7 SP - 5013-5020 SN - 1550-235X ER - TY - JOUR TI - Chemical and strain effects on Boron-doped Si(100) AU - Ramamoorthy, M AU - Briggs, EL AU - Bernholc, J T2 - PHYSICAL REVIEW B AB - Theoretical investigations uncover complex strain-induced modes of boron ordering at the Si(100) surface, which are highly anomalous in comparison with other group III impurities. The fundamental units of the clustering process are subsurface pairs of B atoms. The structural relaxations around segregated B impurities are substantial and the induced strain fields couple with the $(2\ifmmode\times\else\texttimes\fi{}1)$ dimer reconstruction of the surface to stabilize complex, zigzag modes of ordering. Impurity configurations exist that are strongly bound with respect to isolated subsurface impurity pairs up to the critical doping level of 0.5 monolayer. Above this doping level, however, all modes of ordering of the impurities at the surface are repulsive. A number of experimental observations are explained and interesting structures are predicted. DA - 1999/2/15/ PY - 1999/2/15/ DO - 10.1103/physrevb.59.4813 VL - 59 IS - 7 SP - 4813-4821 SN - 2469-9969 ER - TY - JOUR TI - Phase segregation in polymer thin films: Elucidations by X-ray and scanning force microscopy AU - Ade, H AU - Winesett, DA AU - Smith, AP AU - Qu, S AU - Ge, S AU - Sokolov, J AU - Rafailovich, M T2 - EUROPHYSICS LETTERS AB - We have used quantitative X-ray microscopy in combination with Scanning Force Microscopy to monitor the phase separation of spun cast thin films of polystyrene and poly(methyl methacrylate) blends upon annealing. Both techniques complement and enhance each other in elucidating the complicated structures that develop as a function of annealing time. We have determined the composition of the mixed phases that result from solvent spin casting. We subsequently observe the sudden rearrangement into domains much smaller than those originally formed. Unique, intricate hydrodynamic mass flow patterns form during coarsening which are in qualitative agreement with recent simulations of phase segregation in two-dimensional viscous fluids. Complicated polymer-polymer interfaces persist even in the later stages that are explained in terms of the geometric constraints of a thin film and the dependance of polymer viscosity on film thickness. DA - 1999/2/15/ PY - 1999/2/15/ DO - 10.1209/epl/i1999-00198-7 VL - 45 IS - 4 SP - 526-532 SN - 0295-5075 ER - TY - JOUR TI - Representation of GaP formation by a reduced order surface kinetics model using p-polarized reflectance measurements AU - Beeler, S AU - Tran, HT AU - Dietz, N T2 - JOURNAL OF APPLIED PHYSICS AB - This contribution presents results on the parameter estimation of rate constants and optical response factors in a reduced order surface kinetics (ROSK) model, which has been developed to describe the decomposition kinetics of the organometallic precursors involved and their incorporation into the film deposition. As a real-time characterization technique, we applied p-polarized reflectance spectroscopy (PRS) during low temperature growth of epitaxial GaP heterostructures on Si(001) substrates by pulsed chemical beam epitaxy. The high surface sensitivity of PRS allows us to follow alterations in the composition and thickness of the surface reaction layer as they are encountered during periodic precursor supply. Linkage of the PRS response to the ROSK model provides the base for the parameter estimation of the reduced order surface kinetics model, giving insights into the organometallic precursor decomposition and growth kinetics. DA - 1999/7/1/ PY - 1999/7/1/ DO - 10.1063/1.370783 VL - 86 IS - 1 SP - 674-682 SN - 1089-7550 ER - TY - JOUR TI - Improvement of gate dielectric reliability for p plus poly MOS devices using remote PECVD top nitride deposition ultra-thin (2.4-6 nm) gate oxides AU - Wu, Y AU - Lucovsky, G T2 - MICROELECTRONICS RELIABILITY AB - Abstract Dual layer dielectrics have been formed by remote PECVD deposition of ultra-thin (0.4–1.2 nm) nitrides onto thin thermal oxides grown on n -type Si(100) substrates. Activation of boron-implanted p + polycrystalline silicon gate electrodes was accomplished by a high temperature anneal, 1–4 min at 1000°C. Boron penetration through the dielectric film to the n -type substrate was investigated by performing a quasi-static C – V analysis and monitoring the flatband voltage shift. Boron penetration was effectively stopped by a 0.8 nm nitride film, and partially stopped by a 0.4 nm nitride film. In addition, the charge to breakdown as monitored by the Q bd value to 50% cumulative failure was highest for the device with the 0.8 nm top nitride, and decreased significantly in the thermal oxide. However there were essentially no differences in the mid-gap interface state densities, D it , between oxide and nitride/oxide gate dielectric structures with Al gate. It is concluded that the 0.8 nm of plasma nitride was sufficient to block boron atom out-diffusion from a heavily implanted p + poly-silicon gate electrode under the conditions of an aggressive implant activation anneal to improve the dielectric reliability. DA - 1999/3// PY - 1999/3// DO - 10.1016/S0026-2714(98)00244-3 VL - 39 IS - 3 SP - 365-372 SN - 0026-2714 ER - TY - JOUR TI - Effect of growth temperature on point defect density of unintentionally doped GaN grown by metalorganic chemical vapor deposition and hydride vapor phase epitaxy AU - Joshkin, VA AU - Parker, CA AU - Bedair, SM AU - Muth, JF AU - Shmagin, IK AU - Kolbas, RM AU - Piner, EL AU - Molnar, RJ T2 - JOURNAL OF APPLIED PHYSICS AB - We report on the investigation of the effect of growth temperature on point defect density of unintentionally doped GaN grown by atmospheric pressure metalorganic chemical vapor deposition and hydride vapor phase epitaxy. A correlation between photoluminescence (PL) spectra and the concentration of donors and acceptors in unintentionally doped GaN is presented. The effects of oxygen and native acceptors on the electrical and optical properties of GaN epitaxial layers are discussed and a classification of PL data is presented. On this basis we show that oxygen creates a shallow donor in GaN with an activation energy of about 23.5±1 meV. We determine that the concentration of native acceptors in GaN increases with an increase in growth temperature. These native acceptors, probably gallium antisites (GaN) and/or gallium vacancies (VGa), are nonradiative defects. We show that a second donor level in GaN has an activation energy of about 52.5±2.5 meV and produces a PL peak with an energy of about 3.45 eV at low temperatures. From Hall investigations we show that a third donor in GaN has an activation energy of 110±10 meV. DA - 1999/7/1/ PY - 1999/7/1/ DO - 10.1063/1.370727 VL - 86 IS - 1 SP - 281-288 SN - 0021-8979 ER - TY - JOUR TI - Confinement-induced miscibility in polymer blends AU - Zhu, S. AU - Liu, Y. AU - Rafailovich, M. H. AU - Sokolov, J. AU - Gersappe, D. AU - Winesett, D. A. AU - Ade, H. T2 - Nature DA - 1999/// PY - 1999/// VL - 400 IS - 6739 SP - 49-51 ER - TY - JOUR TI - Predicted images and spectra of gamma rays and x-rays from shell supernova remnants AU - Reynolds, S. P. T2 - Astrophysical Letters & Communications DA - 1999/// PY - 1999/// VL - 38 IS - 1-6 SP - 425 ER - TY - JOUR TI - Reaction rate of Mg-24(p,gamma)Al-25 AU - Powell, DC AU - Iliadis, C AU - Champagne, AE AU - Grossmann, CA AU - Hale, SE AU - Hansper, VY AU - McLean, LK T2 - NUCLEAR PHYSICS A AB - The proton-capture reaction on 24Mg has been investigated in the bombarding energy range of Ep=0.2–1.7 MeV. Resonance properties (strengths, branching ratios and lifetimes) of low-energy resonances have been measured. From the experimental results, accurate proton partial widths, γ-ray partial widths and total widths (Γp, Γγ, and Γ) have been deduced. The present experimental information establishes the 24Mg+p reaction rates over the temperature range T=0.02–2.0 GK with statistical uncertainties of 5% to 21%. Our recommended reaction rates deviate from previous estimates by 18% to 45%. Based on our results, we can rule out the recent suggestion that the total width of the ER=223 keV resonance has a significant influence on the reaction rates. We also discuss several effects that might give rise to systematic uncertainties in the reaction rates. The astrophysical implications for hydrogen burning of 24Mg at low stellar temperatures are presented. DA - 1999/11/29/ PY - 1999/11/29/ DO - 10.1016/S0375-9474(99)00390-5 VL - 660 IS - 3 SP - 349-378 SN - 0375-9474 ER - TY - JOUR TI - Relaxation phenomena in GaN/ AlN/ 6H-SiC heterostructures AU - Edwards, N. V. AU - Batchelor, A. D. AU - Buyanova, I. A. AU - Madsen, L. D. AU - Bremser, M. D. AU - Davis, R. F. AU - Aspnes, D. E. AU - Monemar, B. T2 - MRS Internet Journal of Nitride Semiconductor Research AB - We have developed a method to modulate the strain state (normally > 4 kbar, tensile) of moderately thick (∼2 μm) GaN based structures grown on 6H-SiC to a range 0 to -2 kbar of compressive stresses by introducing a strain-mediating layer (SML) above the standard high-temperature AlN buffer layer. The strain characteristics of subsequently deposited nitride layers can be modulated by changing the growth parameters of the SML layer. This is achieved by in-situ techiniques during crystal growth without degrading the optical and structural properties of the deposited layers. DA - 1999/// PY - 1999/// DO - 10.1557/s1092578300002830 VL - 4S1 IS - G3.78 ER - TY - JOUR TI - Raman analysis and field emission study of ion beam etched diamond films AU - Park, M AU - McGregor, DR AU - Bergman, L AU - Nemanich, RJ AU - Hren, JJ AU - Cuomo, JJ AU - Choi, WB AU - Zhirnov, , VV T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - Discontinuous diamond films were deposited on silicon using a microwave plasma chemical vapor deposition system. The diamond deposits were sharpened by argon ion beam etching. Raman spectroscopy was carried out to study the structural change of the diamond after ion beam bombardment. It was found that amorphous sp2 carbon is produced as diamond is being sputtered by the Ar ion beam. The field emission turn-on field was also drastically lowered after sharpening, which, it is speculated, is caused by field enhancement due to change in geometry and/or structural changes (such as amorphization of crystalline diamond into graphitic or amorphous sp2 carbon) by Ar ion irradiation. DA - 1999/// PY - 1999/// DO - 10.1116/1.590622 VL - 17 IS - 2 SP - 700-704 SN - 2166-2746 ER - TY - JOUR TI - Quantum held theory of meson mining - art. no. 056003 AU - Binger, M. AU - Ji, C. R. T2 - Physical Review. D, Particles and Fields DA - 1999/// PY - 1999/// VL - 6005 IS - 5 SP - 6005 ER - TY - JOUR TI - Photodetachment of H- AU - Kuan, WH AU - Jiang, TF AU - Chung, KT T2 - PHYSICAL REVIEW A AB - In a recent experiment [Andersen et al., Phys. Rev. Lett. 79, 4770 (1997)], the ${\mathrm{H}}^{\ensuremath{-}}$ photodetachment cross section (PDCS) and resonances are measured to high precision. Detailed resonance profiles are obtained. To make a critical comparison with experiment, the ${\mathrm{H}}^{\ensuremath{-}}$ PDCS below the $n=2$ and $n=3$ thresholds is calculated with a saddle-point complex-rotation method. The theoretical PDCS are convoluted with a Gaussian profile using experimental resolution for full width at half maximum. The theoretical results are calculated with length, velocity, and acceleration gauges. They are compared with the precision data in the literature. Improved widths are obtained for some of the narrow resonances below the $n=3$ threshold. DA - 1999/7// PY - 1999/7// DO - 10.1103/PhysRevA.60.364 VL - 60 IS - 1 SP - 364-369 SN - 1094-1622 ER - TY - JOUR TI - Electronic transport in extended systems: Application to carbon nanotubes AU - Nardelli, M. B. T2 - Physical Review. B, Condensed Matter and Materials Physics DA - 1999/// PY - 1999/// VL - 60 IS - 11 SP - 7828-7833 ER - TY - JOUR TI - Dry ex situ cleaning processes for (0001)(Si) 6H-SiC surfaces AU - King, SW AU - Nemanich, RJ AU - Davis, RF T2 - JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB - A completely dry ex situ cleaning process based on oxidation and HF vapor exposure for removal of residual C and oxide, respectively, from [the silicon‐terminated surface of SiC] 6H‐SiC surfaces to levels equivalent to or better than conventional wet chemical ex situ processing has been demonstrated. X‐ray photoelectron spectroscopy (XPS) of surfaces exposed to UV‐generated ozone revealed the formation of carbon and silicon oxides, as indicated by the broad Si‐O Si 2p peak at 102.4 eV (full width at half‐maximum = 2.1 eV) and a shift in the surface C 1s peak from 283.6 to 284.2 eV, respectively. Evidence for a reduction in the amount of surface C was shown by an increase in the ratio of the SiC C peak to the surface C peak from 0.8 to 2.7 after the treatment. Removal of the silicon oxide via exposure to the vapor from a 10:1 buffered HF solution was indicated by the absence (below the XPS detection limit) of the Si‐O Si 2p peak at 102.4 eV. However, this last process results in a F‐terminated surface. © 1999 The Electrochemical Society. All rights reserved. DA - 1999/7// PY - 1999/7// DO - 10.1149/1.1391986 VL - 146 IS - 7 SP - 2648-2651 SN - 0013-4651 ER - TY - JOUR TI - Cobalt suicide formation on 6H silicon carbide AU - Porto, AO AU - Boyanov, BI AU - Sayers, DE AU - Nemanich, RJ T2 - JOURNAL OF SYNCHROTRON RADIATION AB - Cobalt films (1, 25 and 100 A) have been directly deposited on top 6H-SiC(0001) wafers by molecular beam epitaxy and annealed at 500-800°C in UHV. The structure of the metal-semiconductor interface was investigated by XAFS. The results show that Co-Si bonds were preferentially formed in the 1 A Co films. In the 25 and 100 A Co films only Co-Co bonds were identified. The XRD pattern of the 100 A Co film exhibits a Co (200) peak confirming the presence of unreacted metal even after annealing at 800°C. DA - 1999/5/1/ PY - 1999/5/1/ DO - 10.1107/S0909049599001326 VL - 6 SP - 188-189 SN - 0909-0495 KW - Silicon Carbide KW - metal-semiconductor contacts KW - molecular beam epitaxy ER - TY - JOUR TI - Band offsets for ultrathin SiO2 and Si3N4 films on Si(111) and Si(100) from photoemission spectroscopy AU - Keister, J. W. AU - Rowe, J. E. AU - Kolodziej, J. J. AU - Niimi, H. AU - Madey, T. E. AU - Lucovsky, G. T2 - Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures DA - 1999/// PY - 1999/// VL - 17 IS - 4 SP - 1831-1835 ER - TY - JOUR TI - Auger decay of multiply excited atomic systems AU - Chung, KT T2 - PHYSICAL REVIEW A AB - By studying the branching ratios in the Auger decay of many triply excited three-electron atomic systems, we try to discover the physical reason behind the relative magnitude of the partial widths. It appears that Auger decay is most likely to happen when the two interacting electrons are in close proximity and the overlap of their charge distribution is significant in coordinate space. It is also pointed out that when an ${\mathrm{nl}}_{1}{\mathrm{nl}}_{2}{n}^{\ensuremath{'}}{l}_{3}{(n}^{\ensuremath{'}}>n>~2)$ state decays into an ${n}^{\ensuremath{''}}{l}_{1}{n}^{\ensuremath{'}}{l}_{3}(n>{n}^{\ensuremath{''}})+\ensuremath{\epsilon}{l}_{2}$ channel, the ${n}^{\ensuremath{'}}{l}_{3}$ orbital of the initial state is more diffused than that of the two-electron target. Therefore, some ${n}^{\ensuremath{''}}{l}_{1}{\mathrm{ml}}_{3}(m>{n}^{\ensuremath{'}})+\ensuremath{\epsilon}{l}_{2}$ channels will also contribute significantly to the Auger width of this state. The argument presented in this work is also applied to two- and four-electron systems. Explicit examples are presented. DA - 1999/3// PY - 1999/3// DO - 10.1103/PhysRevA.59.2065 VL - 59 IS - 3 SP - 2065-2070 SN - 1094-1622 ER - TY - JOUR TI - An integral equation study of a simple point charge model of water AU - Lombardero, M AU - Martin, G AU - Jorge, S AU - Lado, F AU - Lomba, E T2 - JOURNAL OF CHEMICAL PHYSICS AB - We present an extensive integral equation study of a simple point charge model of water for a variety of thermodynamic states ranging from the vapor phase to the undercooled liquid. The calculations are carried out in the molecular reference-hypernetted chain approximation and the results are compared with extensive molecular dynamics simulations. Use of a hard sphere fluid as a reference system to provide the input reference bridge function leads to relatively good thermodynamics. However, at low temperatures the computed microscopic structure shows deficiencies that probably stem from the lack of orientational dependence in this bridge function. This is in marked contrast with results previously obtained for systems that, although similarly composed of angular triatomic molecules, do not tend to the tetrahedral coordinations that are characteristic of water. DA - 1999/1/8/ PY - 1999/1/8/ DO - 10.1063/1.478156 VL - 110 IS - 2 SP - 1148-1153 SN - 0021-9606 ER -