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  • 1
    Electronic Resource
    Electronic Resource
    Mass spectrometric transient study of dc plasma etching of Si in CF4 and CF4/O2 mixtures (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 119-122 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: dc plasma etching experiments were carried out on polycrystalline Si wafers using CF4 and CF4/O2 mixtures as etchants. The etchants were injected into a slow stream of Ar while a continuous discharge was maintained. The resulting transients of intermediate and product species were determined mass spectrometrically; some of these were found to depend very much on the oxygen concentration, even though hysteresis effects which complicated earlier results were not noticed in this study.The results do not support existing simplified models, but yield some detailed information concerning the etching mechanism. The etch rates increase when small amounts of oxygen are added to the CF4, probably due to an increase in the atomic fluorine concentrations, while at larger oxygen concentrations they decrease, in part because the fragmentation of the etchant gas CF4 is then suppressed. CF2 radicals are found to be present in the plasma in appreciable concentrations; presumably, this species is directly involved in the formation of SiF4 at the surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335385
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  • 2
    Electronic Resource
    Electronic Resource
    Time-ordered operators and Feynman–Dyson algebras (1987)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 28 (1987), S. 1459-1470 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: An approach to time-ordered operators based upon von Neumann's infinite tensor product Hilbert spaces is used to define Feynman–Dyson algebras. This theory is used to show that a one-to-one correspondence exists between path integrals and semigroups, which are integral operators defined by a kernel, the reproducing property of the kernel being a consequence of the semigroup property. For path integrals constructed from two semigroups, the results are more general than those obtained by the use of the Trotter–Kato formula. Perturbation series for the Feynman–Dyson operator calculus for time evolution and scattering operators are discussed, and it is pointed out that they are "asymptotic in the sense of Poincaré'' as defined in the theory of semigroups, thereby giving a precise formulation to a well-known conjecture of Dyson stated many years ago in the context of quantum electrodynamics. Moreover, the series converge when these operators possess suitable holomorphy properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.527499
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  • 3
    Electronic Resource
    Electronic Resource
    Γ- and X-band contributions to nonresonant tunneling in GaAs/Al0.35Ga0.65As double quantum wells (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2517-2519 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Time-resolved photoluminescence in the picosecond regime is performed on an asymmetric GaAs/Al0.35Ga0.65As double quantum well structure with a barrier thickness of 6 nm to obtain the Γ- and X-point barrier contributions to nonresonant tunneling. Application of hydrostatic pressure up to 37 kbar at 5 K reveals that tunneling via virtual X states is at least 800 times less efficient than via virtual Γ states. Above 24.5 kbar an extremely fast scattering of electrons out of the n=1 quantized level of the narrower quantum well is observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101994
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  • 4
    Electronic Resource
    Electronic Resource
    Excimer and CO2 laser interactions with foamed polystyrene (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1701-1703 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the results of a study of excimer (308 nm) and CO2 laser etching of foamed polystyrenes. The relative role of photochemical and photothermal effects in material removal can be seen by comparing vaporization energies λ obtained under different material removal regimes. The most efficient material removal occurs with 308 nm pulses at a high repetition rate. Under these conditions λ=10–20 J cm−3 corresponding to 0.3–0.6 eV per monomer. This should be compared to 2–5 eV per monomer with photochemical ablation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102194
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  • 5
    Electronic Resource
    Electronic Resource
    Design considerations for diffraction coupled arrays with monolithically integrated self-imaging cavities (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1848-1850 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Conditions for stabilization of in-phase or out-of-phase array eigenmodes in diffraction coupled diode laser arrays are derived and applied to several array architectures. The analysis predicts that the discrimination between these two eigenmodes is strongest in arrays with half Talbot distance long free-propagation region. In this geometry, the out-of-phase and in-phase near fields are, respectively, reproduced and channeled halfway between the original channel locations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101255
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  • 6
    Electronic Resource
    Electronic Resource
    Observation of a resonant enhancement of microwave radiation from a gas-filled backward wave oscillator (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 559-561 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-power microwave radiation at 8 GHz from a gas-filled backward wave oscillator driven by an intense relativistic electron beam has been measured. It has been observed that an order of magnitude resonant increase in microwave output power occurs at a particular pressure of the background gas. This resonance has also been observed to be strongly dependent on the value of applied axial magnetic field. Possible explanations for the observed results are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99856
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  • 7
    Electronic Resource
    Electronic Resource
    Magnetic suspension of superconductors at 4.2 K (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2346-2347 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have observed the stable suspension of superconductors at 4.2 K below a permanent magnet; the superconductors were the type II material Nb3Sn and the high transition temperature material YBa2Cu3Ox. Suspension below a magnet is to be distinguished from levitation above a magnet, which is the classic demonstration of the Meissner effect. Suspension at 4.2 K can be quantitatively explained as due to complete flux trapping in the superconductor. Suspension has previously been observed only at high temperatures in high transition temperature materials, in which the flux trapping is not complete.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100521
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  • 8
    Electronic Resource
    Electronic Resource
    Time-resolved measurements of tunneling between double quantum wells in In0.53Ga0.47As/InP (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 885-887 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Tunneling of electrons between double quantum wells is investigated by time-resolved photoluminescence in the picosecond regime. The samples contain two In0.53Ga0.47As quantum wells with different widths, separated by various InP barriers. At low excitation density, the luminescence decay time of the narrower quantum well depends strongly on the thickness of the barrier, revealing the lifetimes to be tunneling controlled. A semiclassical model explains the observed nonresonant tunneling escape times. With increasing density, the luminescence decay time of the narrower quantum well strongly increases and finally saturates due to effective mass filtering, which leads to a lineup of the electron levels in both wells and resonant tunneling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101615
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  • 9
    Electronic Resource
    Electronic Resource
    Persistent currents in ceramic and evaporated thin-film toroids of Ba2YCu3O7 (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 328-330 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have demonstrated the existence of circumferential persistent currents in Ba2YCu3O7 ceramic toroids at 77 and 4.2 K and in thin films at 77 K. The field dependence of the critical current densities obtained from these persistent current measurements at 77 K is in fair agreement with that obtained from transport measurements. The persistent critical current densities for fields less than 10 G are 150 A/cm2 for the ceramic at 77 K and 105 A/cm2 for the thin film. A long term experiment showed that the resistivity is less than 3×10−18 Ω cm at 77 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99454
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  • 10
    Electronic Resource
    Electronic Resource
    Cooling of hot carriers in Ga0.47In0.53As (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 673-675 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Carrier cooling is measured in an Al0.48In0.52As/Ga0.47In0.53As/InP heterostructure by time-resolved photoluminescence experiments for excitation densities between 5×1016 and 2.2×1018 cm−3. For low excitation density, the energy-loss rate by emission of optical phonons is close to theoretical bulk value, whereas a reduction of the energy-loss rate by a factor of 100 is found for the highest excitation density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98330
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