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  • 2000-2004  (30)
  • 1995-1999  (64)
  • 1990-1994  (81)
  • 1860-1869  (2)
  • 1
    Electronic Resource
    Electronic Resource
    A transmission electron microscope investigation of the dose dependence of the microstructure of silicon-on-insulator structures formed by nitrogen implantation of silicon (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 3503-3511 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transmission electron microscope studies have been made of (100) silicon wafers implanted at 500 °C with 200-keV 14N+ ions to doses of either 0.25, 0.75, or 1.4×1018 cm−2. For all of these specimens, the as-implanted wafers contained a buried amorphous layer with a damaged upper single-crystal silicon layer. For the 1.4×1018 cm−2 specimen, the amorphous layer contained bubbles. Wafers subsequently annealed at 1200 °C in order to form silicon-on-insulator structures showed the following. For the 0.25×1018 cm−2 specimen, there was a buried discontinuous polycrystalline α-Si3N4 layer, and an upper silicon layer with no observable defects. For the 0.75×1018 cm−2 specimen, there was a buried continuous polycrystalline α-Si3N4 layer containing small silicon islands, and an upper silicon layer either without defects or with microtwins adjacent to the nitride/silicon interface. For the 1.4×1018 cm−2 specimen, there was a buried multilayer structure with the middle layer consisting of substantially single-crystal α-Si3N4 free from silicon islands but containing bubbles; and an upper silicon layer with microtwins and threading dislocations. For the 0.25 and 0.75×1018 cm−2 specimens, the α-Si3N4 had often grown epitaxially in the single-crystal silicon. For the 0.75×1018 cm−2 specimen, such epitaxy had less often occurred. For the 1.4×1018 cm−2 specimen, such epitaxy was not observed. These structural results are correlated with the implantation conditions and nitrogen depth profiles obtained by secondary ion mass spectrometry. The mechanisms responsible for producing the structures are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348491
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  • 2
    Electronic Resource
    Electronic Resource
    Electronic properties of silicon δ-doped InSb (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 671-675 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated magneto-transport and cyclotron resonance (CR) of two-dimensional electron gas in silicon δ-doped p-InSb under a magnetic field of up to 12 T at 4.2 K. Because there are multiple subbands occupied, Shubnikov–de Haas oscillations show a beating behavior. The CR spectra also display several peaks originating from different subbands. Effective masses of electrons associated with the lowest three subbands can therefore be directly determined, and they are in excellent agreement with a self-consistent calculation, which takes into account the electrostatic Poisson equation, the Schrödinger equation, and realistic sample parameters. Furthermore, we observed an absorption peak, whose resonance position has anomalous angle dependence. It is attributed to impurity CR where donors are in the vicinity of the δ-doped sheet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351850
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  • 3
    Electronic Resource
    Electronic Resource
    Design considerations for z-pinch driven photoresonant x-ray lasing in neonlike krypton (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4671-4677 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A neonlike x-ray laser photoresonant pumping scheme is explored. An attractive design is a coaxial z-pinch consisting of an inner krypton lasant plasma surrounded by a carbon shell that itself is surrounded by a stagnated krypton plasma. The photoresonant radiation emitted from the outer plasma passes inwardly through the carbon shell and photoexcites lasant electrons to the 3s, 3d, and 4d levels. It is calculated that monochromatic pump powers of 30 GW/cm eV can be achieved for the 4d neonlike resonance line while powers of 100–200 GW/cm eV are attainable for the 3s and 3d resonance lines. The gain in several neonlike 3s-3p transitions is calculated as a function of temperature and density of the lasant plasma. Reasonable gain in only the 3p-3s (J=0–1) transition is obtained for high-density, high-temperature lasant conditions. This gain, which is driven by monopole excitation from the ground state to the 3p (J=0) level, is nearly independent of the presence of pump radiation. For low-density, low-temperature lasants, optimal gain is obtained in the 3p-3s (J=2–1) transitions. Under these conditions, the pump radiation is necessary to photoionize and photoexcite the lasant plasma to the neonlike stage while radiative decay from the resonantly pumped 4d level to the 3p (J=2) states provides the major upper lasing level pump mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350657
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  • 4
    Electronic Resource
    Electronic Resource
    Generation of high-energy x-radiation using a plasma flow switch (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1999-2007 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experiments with coaxial plasma guns at currents in excess of ten megamperes have resulted in the production of high-voltage pulses (0.5 MV) and hard x radiation (10–200 keV). The x-radiation pulse occurs substantially after the high-voltage pulse suggesting that high-energy electrons are generated by dynamic processes in a very high speed ((approximately-greater-than)106 m/s), magnetized plasma flow. Such flows, which result from acceleration of relatively low-density plasma (10−4 vs 1.0 kg/m3) by magnetic fields of 20–30 T, support high voltages by the back electromotive force-u×B during the opening switch phase of the plasma flow switch. A simple model of classical ion slowing down and subsequent heating of background electrons can explain spectral evidence of 30-keV electron temperatures in fully stripped aluminum plasma formed from plasma flows of 1–2 × 106 m/s. Similar modeling and spectral evidence indicates tungsten ion kinetic energies of 4.5 MeV and 46 keV electron temperatures of a highly stripped tungsten plasma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348773
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  • 5
    Electronic Resource
    Electronic Resource
    Use of atomic layer epitaxy buffer for the growth of InSb on GaAs by molecular beam epitaxy (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7166-7172 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A 300 A(ring) buffer layer of InSb grown by atomic layer epitaxy at a substrate temperature of 300 °C at the GaAs/InSb interface has been employed to grow epitaxial films of InSb having bulk-like properties. The reduction of the defects in the top InSb film has been observed with cross-sectional transmission electron microscopy and channeling Rutherford backscattering spectroscopy. The optimum substrate temperature for the primary InSb layer growth was 420 °C with an atomic flux ratio of Sb to In of 1.4 and a growth rate of 1 μm/h. The best 5-μm-thick InSb layers had x-ray rocking curve widths of 100 s, 77 K n-type carrier concentrations in the low 1015/cm3 range, and 77 K carrier mobilities greater than 105 cm2/V s. Mesa isolated photodiodes had carrier lifetimes of 20 ns, in comparison to 200 ns observed in bulk InSb having a similar carrier concentration. An unexplained, weak free-electron spin resonance transition has been observed in these films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347608
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  • 6
    Electronic Resource
    Electronic Resource
    An efficient tabulated collisional radiative equilibrium radiation transport model suitable for multidimensional hydrodynamics calculations (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 3480-3489 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A computationally efficient method for transporting radiation in multidimensional plasmas has been developed and evaluated. The basis of this method is a uniform plasma approximation that allows one to utilize existing escape probability techniques that are successfully used in one-dimensional (1D) calculations to approximately solve the multidimensional radiation transport problem. This method is superior to diffusion methods because (1) the probability of escape technique insures that the plasma goes to the correct optically thin and thick limits, (2) the effects of line absorption due to photoexcitations are modeled, and (3) this method uses source functions that are based on a self-consistent nonlocal thermodynamic equilibrium calculation, not an ad hoc assumption that the source functions are Planckian. This method is highly efficient because equation of state information from 1D calculations is tabulated as a function of plasma internal energy, ion density, and the line probability of escape from a uniform plasma, and then used in multidimensional calculations. Given the internal energy and ion density, and by calculating the line probability of escape from a zone of the multidimensional plasma, the equation of state, including emissivities and absorption coefficients, of the zone is determined from the table. Total radiative power, K-shell radiative power, total radiative yield, K-shell radiative yield, and plasma density and temperature profiles obtained from 1D Z-pinch calculations employing this method are in good agreement with the same powers, yields, and profiles calculated using a full radiation transport model. This method has been implemented in the 2D plasma radiating imploding source model code [F. L. Cochran et al., Phys. Plasmas 2, 2765 (1995)] to determine the influence of radiation transport in argon Z-pinch experiments performed on the Z machine [R. B. Spielman et al., Phys. Plasmas 5, 2105 (1998)] at Sandia National Laboratories. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1373415
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  • 7
    Electronic Resource
    Electronic Resource
    Trends in plasma conditions inferred from an analysis of x-ray data from high wire-number, Z-pinch load implosions (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 3708-3717 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An analysis of x-ray data from two series of Z-pinch shots taken on the short current-risetime Saturn accelerator at Sandia National Laboratories [Proceedings of 6th International IEEE Pulsed Power Conference, Arlington, VA, edited by P. J. Turchi and B. H. Bernstein (IEEE, New York, 1987), p. 310] is presented. In one series, the array radius was held constant and the array mass was varied; in the other series, the array mass was held constant and its radius varied. In both sets of experiments, large wire-number loads (N≥93) of aluminum were used in contrast to earlier small wire-number aluminum array experiments on Saturn where N≤42. Average electron temperatures and ion densities were inferred from the data. In addition, from the measured size of the emission region of K-shell x rays and from the inferred ion density, a fraction of the total array mass that participated in the K-shell emission was inferred and found to be directly correlated to the K-shell yields that were measured. This paper also demonstrates that the yields varied as a function of array mass and radius in much closer agreement with predictions [J. Appl. Phys. 67, 1725 (1990)] than had been observed in the earlier small wire-number experiments. Thus, a serious misperception that the reason for the early disagreement was in the calculations and not in the experiments is corrected. These predictions were made using one-dimensional (1D) magnetohydrodynamics calculations. The density and temperature trends inferred from the data analysis are well-behaved and consistent with the 1D calculations. This data analysis confirms the importance of achieving uniform plasma initial conditions and implosion symmetry when comparing computer code calculations with experiment. When the wire number of an array load is increased, a more uniform shell of plasma is calculated initially as the wires explode and, as the plasma stagnates on axis, the x-ray powers and yields are found experimentally to approach the powers and yields predicted by 1D calculations. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1380695
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  • 8
    Electronic Resource
    Electronic Resource
    High energy photon radiation from a Z-pinch plasma (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 4509-4517 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new approach to the generation of kilovolt x ray radiation in Z-pinch plasma radiation sources is proposed. In cases where the pulse power machine has insufficient energy to efficiently produce K-shell emission from the atomic number element that emits in the required kilovolt energy range, it may be advantageous to produce x rays by recombination radiation emitted from a lower atomic number plasma. The optimal load conditions for maximizing the high energy free–bound continuum radiation that can be produced in a given spectral range are analyzed. The largest yield is expected from a highest-atomic-number element that could efficiently produce K-shell yield on a given pulse power machine. Two options available for the choice of a wire array material to generate x rays with photon energies above 7–8 keV are identified and discussed, aluminum and titanium. The analytical estimates and simulation results for "Z" machine implosions show that continuum radiation from an aluminum plasma in this spectral range could exceed the K-shell output from nickel. If a titanium plasma could be ionized to a H-like state on "Z," then its yield above 7 keV should be higher compared to that of aluminum by a factor of 3 to 4. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1398572
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  • 9
    Electronic Resource
    Electronic Resource
    Stability and radiative performance of structured Z-pinch loads imploded on high-current pulsed power generators (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2765-2772 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The stability and radiative performance of structured Z-pinch plasma loads heated by high-current ((approximately-greater-than)20 MA) pulsed power generators are investigated. A limited mapping of parameter space is made for the regions of stability for loads configured as thin shells, uniform fills, and multiple shells. Although large diameter thin shell loads are shown to be the most efficient radiators of K-shell x rays, they are susceptible to disruption by the Rayleigh–Taylor instability. Large diameter uniform fill loads are shown to be more stable and very good radiators. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871475
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  • 10
    Electronic Resource
    Electronic Resource
    Optimization of x-ray emission in Z-pinch implosions: Theory versus experiment (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2590-2596 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Three sets of Z-pinch experiments were performed in recent years [Phys. Rev. E 50, 2166 (1994)] that confirmed the existence of a theoretically predicted region in (load mass)-(implosion velocity) space where efficient conversion of implosion energy to kilovolt x rays was possible [J. Appl. Phys. 67, 1725 (1990)]; but they also raised questions about the validity of the theoretical models [Phys. Plasmas 1, 321 (1994)] and about the influence of the pulse-power generator and load design on the detailed behavior of the measured x-ray yields. Newly completed experiments suggest that some of these influences can be overcome and that K-shell yields can be increased in greater accord with theoretical expectations. In this paper, a brief description of these experiments is given, and some comparisons with recent theoretical findings are made along with comparisons with the above-mentioned earlier work. These new comparisons demonstrate the need for further improvements in the theoretical models and in the way experiments are designed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871221
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